CN116054610A - AC-DC converter, controller, driving system and driving method - Google Patents

Abstract

The invention provides an AC-DC converter, a controller, a driving system and a driving method, wherein the driving system comprises: the power supply clamping module provides power supply voltage for the driving module; the driving module drives the external power switch tube to be switched on and off; the sampling comparison module compares the driving voltage with the Miller platform voltage at the first sampling moment, the difference value of the driving voltage and the Miller platform voltage is larger than the set voltage, and the comparison signal is of a low level, otherwise, the comparison signal is of a high level; the secondary sampling module collects the comparison signal at the second sampling moment, is in a low level, and sends a reduction signal, otherwise sends an increase signal; the step current controller decreases or increases the input current provided to the driving module according to the decrease signal or the increase signal, thereby increasing or decreasing the time of the miller stage of the next period; when the comparison signals collected by the secondary sampling module are subjected to level conversion in adjacent periods, an amplification signal is sent to a stepping current controller, and the stepping current controller delays for a set time to multiply and amplify the input current. The time of the miller stage of the invention is fixed.

Description

AC-DC converter, controller, driving system and driving method

technical field

The present invention relates to the technical field of switching power supplies, and more specifically, to an AC-DC converter, a controller, a driving system and a driving method.

Background technique

AC-DC converters are widely used in almost all electronic equipment. FIG. 1 is a schematic diagram of a flyback AC-DC converter in the prior art. As shown in FIG. 1, the control chip 1 includes a chip power supply pin VCC, a feedback input terminal FB, a current detection terminal CS, a The output terminal Gate and a ground pin GND, the output terminal Gate outputs a driving voltage VG with a suitable duty ratio according to the voltage of the feedback input terminal FB, and the driving voltage VG is used to drive the external power switch tube 2, and the external power switch tube 2 One end is connected to the current detection resistor 3, the other end of the external power switch tube 2 is connected to the same-named end of the primary winding NP of the transformer 4, the other end of the primary winding of the transformer is connected to the input voltage rectified by the rectifier bridge 5, and the secondary side of the transformer The winding NS is connected to the output end through the first rectifier diode 6 and the output capacitor 7, and the output end generates a feedback signal to the The feedback input terminal FB of the control chip 1, the transformer also includes an auxiliary winding NA, the terminal of the same name of the auxiliary winding NA supplies power to the control chip (chip power supply pin VCC) through the second rectifier diode 13 and the first capacitor 14, and the starting resistor 22 is in After the AC power is turned on, the first capacitor 14 is charged, so that the chip can be started.

The traditional AC-DC control chip controls the on-off of the external power switch tube 2 through the totem pole drive output. As shown in Figure 2, when the PWM signal is at a high level, the external power switch tube 2 should be turned on, and the driving voltage VG should become high level. When the PWM signal is at a high level, its reverse signal PWMB signal is at a low level, the first switching tube 15 and the second switching tube 16 are all turned off, the third switching tube 17 is turned on, and the driving current of the first current mirror 20 I1 charges the second capacitor 18 , the gate voltage VH of the fourth switching tube 19 rises, the fourth switching tube 19 acts as a source follower, and the driving voltage VG also rises, thereby driving the external power switching tube 2 . Generally, the fully turned-on voltage of the external power switch tube 2 is about 6-10V, so the driving output voltage of the control chip 1 is generally clamped at about 12V to ensure that the external power switch tube is fully turned on while saving switching losses and ensuring external power. For the safety of the switching tube, the first voltage regulator tube 21 clamps the gate voltage VH voltage of the fourth switching tube 19 to about 13V, which is subtracted from the gate-source voltage of the fourth switching tube 19 (about 1V), so the drive output is high The level is clamped around 12V. In order to improve EMI (electromagnetic interference), the totem pole driving circuit controls the rising speed of the gate voltage VH of the fourth switching tube 19 through the driving current I1 of the first current mirror 20 and the third switching tube 17, and then through the source follower ( The fourth switching tube 19 ) indirectly controls the rising speed of VG, so as to realize the soft turn-on of the external power switching tube 2 .

The above soft opening of the external power switch tube 2 through the totem pole has the following problems:

First, once the driving current I1 of the first current mirror 20 and the parameters of the third switching tube 17 and the fourth switching tube 19 are determined, the rising slope of the gate voltage VH of the fourth switching tube 19 and the driving capability of the fourth switching tube 19 It is fixed. When driving external power switch tubes of different specifications, due to the great difference in the parasitic capacitance (gate-source capacitance Cgs and gate-drain capacitance Cgd) parameters of the external power switch tube, the requirements for the driving capability of the fourth switch tube 19 are different. , in addition, under different temperature, input voltage, etc., the rising speed of the driving voltage VG will change greatly, and the soft turn-on effect of the external power switch tube 2 will become worse, so that the EMI performance of the external power switch tube with different specifications A lot of difference;

Second, after the Miller platform, the driving voltage VG of different external power switch tubes rises at different speeds. If the driving voltage VG rises too slowly, the efficiency will be relatively low.

Contents of the invention

Aiming at one or more of the existing problems in the prior art, the present invention provides a drive system, which is set in the controller of the AC-DC converter and used to drive an external power switch tube, and the drive system includes a power supply clamping module , a sampling comparison module, a secondary sampling module, a stepping current controller and a driving module, wherein:

The power supply clamping module is used to provide a power supply voltage for the driving module;

The drive module is used to drive the external power switch tube to be turned on and off;

The sampling comparison module is used to collect the driving voltage of the driving module to the external power switch tube and collect the Miller platform voltage at the first sampling moment, compare the driving voltage with the Miller platform voltage, and output a comparison signal, and the driving voltage and the Miller platform voltage are compared. When the difference of the Miller platform is greater than the set voltage, the comparison signal is low level; when the driving voltage is not greater than the set voltage compared with the Miller platform voltage, the comparison signal is high level;

The secondary sampling module is used to sample the comparison signal at the second sampling moment, and when the sampled comparison signal is at a low level, send a reduction signal to the step current controller; when the comparison signal is at a high level, Send an increase signal to the stepping current controller;

The step current controller is used to provide an input current to the drive module, and when the step current controller receives a reduction signal, it reduces the input current with a first step; the step current controller receives when increasing the signal, increasing the input current by a second step size;

Wherein, the drive module is also used to amplify the input current, the input current increases, the time of the Miller platform in the next cycle is reduced, the input current decreases, and the time of the next cycle of the Miller platform is increased; the secondary The comparison signal collected by the sampling module sends an amplified signal to the stepping current controller when the level conversion occurs in the adjacent cycle, and the stepping current controller delays the setting time to increase the input current by the set multiple and maintain the set time.

According to one aspect of the present invention, the power supply clamping module includes a second resistor, a second regulator tube and a fifth switch tube, one end of the second resistor is connected to the pull-up voltage, and the other end of the second resistor is respectively connected to The fifth switch tube and the second voltage regulator tube, the second voltage regulator tube is used to clamp the conduction voltage of the fifth switch tube, and the fifth switch tube is turned on to supply power to the drive module.

According to one aspect of the present invention, the fifth switch tube is an NMOS tube, one end of the second resistor is connected to the pull-up voltage, and the other end of the second resistor is connected to the cathode of the voltage regulator tube and the gate of the fifth switch tube. pole, the anode of the second regulator tube is grounded, the drain of the fifth switch tube is connected to the pull-up voltage, and the source of the fifth switch tube is used to supply power to the drive module.

According to one aspect of the present invention, the drive module includes a second current mirror, an eighth switch tube, a ninth switch tube, a third resistor, and an inverter, and the second current mirror includes a sixth switch tube and a seventh switch tube. One end of the sixth switch tube is connected to the power supply clamp module, and the other end of the sixth switch tube is connected to the step current controller through the eighth switch tube, and the eighth switch tube is used to control the step current control Turn off and conduction between the device and the seventh switch tube, one end of the seventh switch tube is connected to the power supply clamp module, and the other end of the seventh switch tube is respectively connected to the third resistor and the ninth switch tube, the The inverter is used to control the turn-on and turn-off of the ninth switch tube, the ninth switch tube and the eighth switch tube are not turned on at the same time, the third resistor is a pull-down resistor, and the ninth switch tube is used to drive voltage is pulled low.

According to an aspect of the present invention, the sixth switch tube and the seventh switch tube are PMOS tubes, the eighth switch tube and the ninth switch tube are NMOS tubes, and the sources of the sixth switch tube and the seventh switch tube are The stages are all connected to the power supply clamp module, the gate and drain of the sixth switch are short-circuited and connected to the gate of the seventh switch and the drain of the eighth switch, and the gate of the eighth switch is used to input the PWM signal , the source of the eighth switching tube is connected to the output of the stepping current controller, the drain of the seventh switching tube is respectively connected to one end of the third resistor and the drain of the ninth switching tube, and the other end of the third resistor is connected to the ninth switching tube. The source stage of the switch tube is grounded, the gate of the ninth switch tube is connected to the output terminal of the inverter, and the input terminal of the inverter is connected to the PWM signal.

According to one aspect of the present invention, the sampling comparison module includes a switch, a third capacitor, a subtractor and a comparator, one end of the switch is connected to the driving voltage, and the other end of the switch is connected to the upper plate of the third capacitor and the comparator The positive input terminal of the comparator, the switch is used to control the on and off of the drive voltage and the positive input terminal of the comparator, thereby controlling the first sampling moment, the lower plate of the third capacitor is grounded, and the positive input of the subtractor terminal is connected to the driving voltage, the negative input terminal is a decompression reference, the decompression reference is the set voltage, the output terminal of the subtractor is connected to the negative input terminal of the comparator, and the output of the comparator is connected to the secondary sampling module.

According to one aspect of the present invention, the secondary sampling module is a sampling switch.

According to one aspect of the present invention, the step current control includes a bidirectional counter and a current controller, the bidirectional counter is used to control the step size of the input current increase or decrease, and the current controller is used to The step size of the control increases or decreases the input current.

According to a second aspect of the present invention, a driving method is provided for driving an external power switch tube of an AC-DC converter, the driving method comprising:

Collect driving voltage;

Collecting the Miller plateau voltage at the first sampling moment;

Compare the driving voltage with the Miller platform voltage, and output a comparison signal. When the difference between the driving voltage and the Miller platform is greater than the set voltage, the comparison signal is low; when the driving voltage and the Miller platform voltage When the comparison is not greater than the set voltage, the comparison signal is high level;

Collecting the comparison signal at the second sampling moment;

When the collected comparison signal is low level, reduce the drive current of the external power switch tube with the first step, thereby reducing the drive voltage of the external power switch tube, increasing the Miller plateau time of the next cycle until Miller The platform end time is greater than the second collection time;

When the collected comparison signal is at a high level, increase the drive current of the signal external power switch tube with the second step length, thereby increasing the drive voltage of the external power switch tube, reducing the Miller plateau time of the next cycle until m The end time of the Le platform is less than the second collection moment;

When the end time of the Miller platform is greater than the second acquisition time or the end time of the Miller platform is less than the second acquisition time, delay the set time, increase the driving current of the external power switch tube by a set multiple and maintain the set time.

According to a third aspect of the present invention, a controller is provided, including the above drive system.

According to the third aspect of the present invention, it also includes an internal power supply and reference system, a power supply voltage judgment system, an overload protection system, a pulse width modulation system, a cycle-by-cycle overcurrent protection system, and a logic system, wherein,

The internal power supply and reference system is used to generate the internal voltage required by each system through the power supply voltage and provide a current-limiting reference for the cycle-by-cycle overcurrent protection system;

The power supply voltage judging system is used to judge whether the power supply voltage is undervoltage or overvoltage. If the power supply voltage is undervoltage or overvoltage, a protection signal is sent to the logic system. If the power supply voltage is not undervoltage or overvoltage, a power supply voltage normal signal is sent to logic system;

The overload protection system is used to judge whether the load is overloaded, if the load is overloaded, send a protection signal to the logic system, and if the load is not overloaded, send a load normal signal to the logic system;

The logic system is used to generate a PWM signal and send it to the drive system when receiving the normal signal of the power supply voltage from the power supply voltage judging system and the normal load signal of the overload protection system, otherwise no PWM signal is generated;

The cycle-by-cycle overcurrent protection system is used to compare the primary current of the AC-DC transformer with the current-limiting reference in each cycle, and when the primary-side current of the transformer reaches the current-limiting reference, cycle shutdown is performed.

According to a fourth aspect of the present invention, an AC-DC converter is provided, including a transformer, an external power switch tube, and the above-mentioned controller, the transformer includes a primary winding, a secondary winding, and an auxiliary winding, and the primary winding of the transformer Connected to the external power switch tube, the auxiliary winding of the transformer is used to supply power to the controller, and the secondary winding of the transformer is used to output energy to the load and output a feedback voltage to the controller;

The controller is used to determine the duty cycle of the PWM signal according to the feedback voltage of the transformer, and generate a time-constant driving voltage of the Miller platform according to the PWM signal, and the driving voltage is used to drive the external power switch tube;

The external power switch tube is used to control the transformation of the transformer between the energy storage state and the degaussing state. When the external power switch tube is turned on, the transformer is in the energy storage state, and the primary winding stores energy; after the external power switch tube is turned off, The transformer enters the degaussing stage, and the energy of the transformer is converted to the secondary winding, and the energy is output from the secondary winding to the load.

The present invention dynamically adjusts the driving current for driving the external power switch tube by comparing the drive voltage and the Miller platform voltage, so that the time of the Miller platform is fixed, thereby realizing good soft opening of external power switch tubes of different specifications, and making EMI The performance is the best. At the same time, after the Miller platform, the driving current increases rapidly, and the gate-source voltage Vgs of the external power switch rises rapidly, so that its on-resistance decreases rapidly, and good efficiency is achieved.

Description of drawings

Other objectives and results of the present invention will be clearer and easier to understand by referring to the following detailed description and in conjunction with the accompanying drawings. In the attached picture:

FIG. 1 is a schematic diagram of a flyback AC-DC in the prior art;

Fig. 2 is the schematic diagram of the totem pole drive circuit of prior art;

Fig. 3 is a schematic diagram of an embodiment of the AC-DC converter of the present invention;

Fig. 4 is a schematic diagram of an embodiment of the controller of the present invention;

Fig. 5 is a schematic diagram of an embodiment of the drive system of the present invention;

Fig. 6 is a schematic diagram of each signal of the driving system shown in Fig. 5;

Among them, control chip 1, external power switch tube 2, current detection resistor 3, transformer 4, rectifier bridge 5, first rectifier diode 6, output capacitor 7, first voltage divider resistor 8, second voltage divider resistor 9, photoelectric Coupler 10, operational amplifier 11, first resistor 12, second rectifier diode 13, first capacitor 14, first switch tube 15, second switch tube 16, third switch tube 17, second capacitor 18, fourth switch Tube 19, first current mirror 20, first voltage regulator tube 21, starting resistor 22, controller 1', drive system 1000, power supply clamp module 100, second resistor 101, second voltage regulator tube 102, fifth switch Tube 103, drive module 200, second current mirror 201, sixth switch tube 2011, seventh switch tube 2012, eighth switch tube 202, inverter 203, ninth switch tube 204, third resistor 205, sampling comparison module 300, switch 301, third capacitor 302, subtractor 303, comparator 304, secondary sampling module 400, step current controller 500, bidirectional counter 501, current controller 502, logic system 2000, clock system 3000, cycle by cycle Overcurrent protection system 4000, pulse width modulation system 5000, overload protection system 6000, power supply voltage judging system 7000, internal power supply and reference system 8000.

Detailed ways

In the following description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of one or more embodiments. It may be evident, however, that these embodiments may be practiced without these specific details.

Various embodiments according to the present invention will be described in detail below with reference to the accompanying drawings.

Fig. 3 is a schematic diagram of an embodiment of the AC-DC converter of the present invention. As shown in Fig. 3, the AC-DC converter includes a transformer 4, an external power switch tube 2 and a controller 1', specifically:

The transformer 4 includes a primary winding, a secondary winding and an auxiliary winding, the primary winding of the transformer 4 is connected to the external power switch tube 2, the auxiliary winding of the transformer 4 is used to supply power to the controller 1′, and the The secondary side winding of the transformer 4 is used to output energy to the load and output the feedback voltage to the controller 1′;

The controller 1' is used to determine the duty ratio of the PWM (Pulse Width Modulation) signal according to the feedback voltage of the transformer 4, and generate a time-constant driving voltage of the Miller platform according to the PWM signal, and the driving voltage is used to drive the Describe the external power switch tube 2;

The external power switch tube 2 is used to control the transformation of the transformer 4 between the energy storage state and the degaussing state, specifically: when the external power switch tube 2 is turned on, the transformer 4 is in the energy storage state, and the primary winding stores energy; After the external power switch tube 2 is turned off, the transformer 4 enters the degaussing stage, and the energy of the transformer 4 is converted to the secondary winding, and the energy is output from the secondary winding to the load.

In one embodiment, as shown in FIG. 3, the AC-DC converter is a flyback AC-DC converter, and the controller 1' includes a chip power supply pin VCC, a feedback input terminal FB, a Current detection terminal CS, an output terminal Gate and a ground pin GND; one end (end with the same name) of the primary winding of the transformer 4 is connected to the external power switch tube 2, and the other end of the primary winding of the transformer 4 Connect the rectifier bridge; the secondary winding of the transformer 4 is connected to the output terminal through the first rectifier diode 6 and the output capacitor 7, and the output terminal passes through the first voltage dividing resistor 8, the second voltage dividing resistor 9, the photocoupler 10, The operational amplifier 11 and the first resistor 12 generate a feedback signal to the controller 1′; one end (end with the same name) of the auxiliary winding of the transformer 4 is connected to one end of the second rectifier diode 13, and the other end of the second rectifier diode 13 is respectively connected to The positive plate of the first capacitor 14 is connected to the chip power supply pin VCC of the controller 1'; the external power switch tube 2 is an NMOS tube, and the gate of the external power switch tube 2 is connected to the output terminal Gate of the controller 1' , the source of the external power switch 2 is respectively connected to the current detection resistor 3 and the current detection terminal CS of the controller 1 ′, and the drain of the external power switch 2 is connected to the same terminal of the primary winding of the transformer 4 .

Fig. 4 is a schematic diagram of an embodiment of the controller of the present invention. As shown in Fig. 4, the controller 1' includes an internal power supply and reference system 8000, a power supply voltage judging system 7000, an overload protection system 6000, a pulse width Modulation system 5000, cycle-by-cycle overcurrent protection system 4000, logic system 2000 and drive system 1000, specifically:

The internal power supply and reference system 8000 is used to generate the internal voltage required by each system through the power supply voltage and provide a current-limiting reference to the cycle-by-cycle overcurrent protection system 4000;

The power supply voltage judging system 7000 is used to judge whether the power supply voltage is undervoltage or overvoltage, if the power supply voltage is undervoltage or overvoltage, send a protection signal to the logic system 2000; if the power supply voltage is not undervoltage or overvoltage, send the power supply voltage to be normal Signal to logic system 2000;

The overload protection system 6000 is used to judge whether the load is overloaded, if the load is overloaded, send a protection signal to the logic system 2000; if the load is not overloaded, send a load normal signal to the logic system 2000;

The logic system 2000 is configured to generate a PWM signal and send it to the drive system 1000 when receiving the normal power supply voltage signal from the power supply voltage judging system 7000 and the normal load signal from the overload protection system 6000; otherwise, no PWM signal is generated;

The cycle-by-cycle overcurrent protection system 4000 is used to compare the primary current of the AC-DC transformer 4 with the current-limiting reference in each cycle, and when the primary current of the transformer 4 reaches the current-limiting reference, cycle shutdown is performed;

The drive system 1000 is used to convert the PWM signal into a drive signal with a constant Miller plateau and a drive current that is multiplied for a set period of time after the Miller plateau ends.

Preferably, the controller 1' also includes a clock system 3000, which is used to generate an internal clock to determine the operating frequency of the controller 1' and other clock signals that need timing.

Fig. 5 is a schematic diagram of an embodiment of the drive system of the present invention, and Fig. 6 is a schematic diagram of various signals of the drive system shown in Fig. 5, as shown in Fig. 5 and Fig. 6, the drive system 1000 includes a power supply clamping module 100, sampling comparison module 300, secondary sampling module 400, step current controller 500 and drive module 200, wherein:

The power supply clamping module 100 is used to provide a power supply voltage for the driving module 200;

The drive module 200 is used to drive the external power switch tube 2 to be turned on and off;

The sampling comparison module 300 is used to collect the drive voltage of the drive module 200 for the external power switch tube 2 and collect the Miller plateau voltage at the first sampling moment, compare the drive voltage with the Miller plateau voltage, and output a comparison signal. When the difference between the driving voltage and the Miller platform is greater than the set voltage, the comparison signal is at a low level; when the comparison between the driving voltage and the Miller platform voltage is not greater than the set voltage, the comparison signal is at a high level;

The secondary sampling module 400 is used to sample the comparison signal at the second sampling moment, and when the sampled comparison signal is low level, send a reduction signal to the step current controller 500; the comparison signal is high level Usually, send an increase signal to the stepping current controller 500;

The step current controller 500 is used to provide an input current to the drive module 200, and when the step current controller 500 receives a reduction signal, it reduces the input current with a first step; the step current When the controller 500 receives the increase signal, it increases the input current with a second step;

Wherein, the driving module 200 is also used to amplify the input current, the input current increases, the time of the Miller plateau in the next cycle is reduced, and the input current decreases, the time of the Miller plateau in the next cycle is increased; the two The comparison signal collected by the sub-sampling module 400 sends an amplified signal to the step current controller 500 when the level shift occurs in the adjacent cycle, and the step current controller 500 delays the set time to increase the input current by a set multiple and maintain the set time.

The driving system of the present invention has an adaptive function, and can obtain good EMI performance and high efficiency when driving external power switch tubes 2 of different specifications.

The above set time is set according to the power supply voltage VDD, the set time is the time when the driving voltage of the external power switch tube 2 reaches 0.9*VDD, the set time is 10-110 ns, preferably, the set time The fixed time is not more than 30ns.

In one embodiment, as shown in FIG. 5 , the power supply clamping module 100 includes a second resistor 101, a second regulator tube 102 and a fifth switch tube 103, one end of the second resistor 101 is connected to a pull-up voltage, The other end of the second resistor 101 is respectively connected to the fifth switch tube 103 and the second voltage regulator tube 102, the second voltage regulator tube 102 is used to clamp the conduction voltage of the fifth switch tube 103, the The fifth switch tube 103 is turned on to supply power to the driving module 200 .

Preferably, the fifth switch tube 103 is an NMOS tube, one end of the second resistor 101 is connected to a pull-up voltage, and the other end of the second resistor 101 is connected to the cathode of the voltage regulator tube and the gate of the fifth switch tube 103 pole, the anode of the second regulator tube 102 is grounded, the drain of the fifth switching tube 103 is connected to the pull-up voltage, and the source of the fifth switching tube 103 is used to supply power to the driving module 200 .

In one embodiment, as shown in FIG. 5 , the drive module 200 includes a second current mirror 201, an eighth switch tube 202, a ninth switch tube 204, a third resistor 205, and an inverter 203. The second The current mirror 201 includes a sixth switch tube 2011 and a seventh switch tube 2012, one end of the sixth switch tube 2011 is connected to the power supply clamp module 100, and the other end of the sixth switch tube 2011 is connected to the step by the eighth switch tube 202. connected to the current controller 500, the eighth switch tube 202 is used to control the turning off and on of the step current controller 500 and the seventh switch tube 2012, and one end of the seventh switch tube 2012 is connected to the power supply clamping module 100, the other end of the seventh switch tube 2012 is respectively connected to the third resistor 205 and the ninth switch tube 204, the inverter 203 is used to control the turn-on and turn-off of the ninth switch tube 204, the first The ninth switch tube 204 and the eighth switch tube 202 are not turned on at the same time, the third resistor 205 is a pull-down resistor, and the ninth switch tube 204 is used to pull down the driving voltage to a low level.

In one embodiment, as shown in FIG. 5, the sixth switch tube 2011 and the seventh switch tube 2012 are PMOS tubes, the eighth switch tube 202 and the ninth switch tube 204 are NMOS tubes, and the sixth switch tube 2012 is a PMOS tube. The source stages of the switching tube 2011 and the seventh switching tube 2012 are both connected to the power supply clamp module 100, the gate and drain of the sixth switching tube 2011 are short-circuited and connected to the gate of the seventh switching tube 2012 and the eighth switching tube 202 Drain, the gate of the eighth switch tube 202 is used to input the PWM signal, the source of the eighth switch tube 202 is connected to the output of the stepping current controller 500, the drain of the seventh switch tube 2012 is connected to the third resistor 205 respectively One end is connected to the drain of the ninth switching tube 204, the other end of the third resistor 205 is grounded to the source of the ninth switching tube 204, the gate of the ninth switching tube 204 is connected to the output end of the inverter 203, and the inverter The input terminal of 203 is connected with PWM signal.

In one embodiment, as shown in FIG. 5 , the sampling comparison module 300 includes a switch 301, a third capacitor 302, a subtractor 303, and a comparator 304. One end of the switch 301 is connected to a driving voltage, and one end of the switch 301 is The other end is connected to the upper plate of the third capacitor 302 and the positive input terminal of the comparator 304, and the switch 301 is used to control the on and off of the driving voltage and the positive input terminal of the comparator 304, thereby controlling the first sampling moment , the lower plate of the third capacitor 302 is grounded, the positive input terminal of the subtractor 303 is connected to the driving voltage, the negative input terminal decompression reference, the decompression reference is the set voltage, the output terminal of the subtractor 303 The negative input end of the comparator 304 is connected, and the output of the comparator 304 is connected to the re-sampling module 400 .

In one embodiment, the re-sampling module 400 is a sampling switch.

In one embodiment, as shown in FIG. 5, the step current controller 500 includes a bidirectional counter 501 and a current controller 502, and the bidirectional counter 501 is used to control the step size of increasing or decreasing the input current, so The current controller 502 is used to increase or decrease the input current according to the step size controlled by the bidirectional counter 501 .

The self-adaptive constant current driving mode of the driving system of the present invention ensures that when driving external power switch tubes 2 of different specifications, the time of the Miller platform is fixed by automatically adjusting the constant current driving current, thereby realizing a good soft opening function, The EMI performance is the best; at the same time, the driving current increases rapidly after the Miller platform, and the large current still has the function of adapting to the specification of the external power switch tube 2, and the Vgs of the external power switch tube 2 of different specifications can rise quickly, so that Its on-resistance decreases rapidly for good efficiency.

In a preferred embodiment of the present invention, as shown in FIG. 5 and FIG. 6, the power supply clamp module 100 composed of the second resistor 101, the second voltage regulator tube 102, and the fifth switch tube 103 provides power supply for the drive module 200. Voltage VDD, the highest voltage of VDD is clamped at about 12V. One end of the second resistor 101 is connected to the chip power supply pin VCC, the other end is connected to the cathode of the second voltage regulator tube 102 and the grid of the fifth switch tube 103, the anode ground pin GND of the second voltage regulator tube 102, and the fifth switch tube The drain of 103 is connected to the chip power supply pin VCC, the source of the fifth switching tube 103 is the supply voltage VDD, which is used to supply power to the drive unit, VDD=Vz-Vgsn, where Vz is the voltage of the second voltage regulator tube 102 The breakdown voltage is generally 13V, and Vgsn is the gate-source voltage of the fifth switching tube 103, generally around 1V, so VDD is clamped around 12V.

The drive module 200 is composed of a sixth switch tube 2011, a seventh switch tube 2012, an eighth switch tube 202, an inverter 203, a ninth switch tube 204 and a third resistor 205. The sixth switch tube 2011 and the seventh switch tube 2012 The source stages of the switches are all connected to VDD, the gate and drain of the sixth switching tube 2011 are short-circuited and connected to the gate of the seventh switching tube 2012 and the drain of the eighth switching tube 202, and the gate of the eighth switching tube 202 is connected to the PWM signal (specific waveform Referring to FIG. 6 ), the source of the eighth switching tube 202 is connected to the output of the step current controller 500, the drain of the seventh switching tube 2012 is connected to the output terminal Gate, and is connected to one end of the third resistor 205 and the ninth switching tube 204 The drain of the third resistor 205 is short-circuited, the other end of the third resistor 205 is connected to the source ground pin GND of the ninth switch tube 204, the gate of the ninth switch tube 204 is connected to the output terminal of the inverter 203, and the input terminal of the inverter 203 Terminates the PWM signal. When the PWM signal is at a high level, the output of the inverter 203 is at a low level, the ninth switch tube 204 is turned off, the eighth switch tube 202 is turned on, and the output current of the step current controller 500 is used as the sixth switch tube 2011 and The input current I2 of the current mirror composed of the seventh switching tube 2012 is amplified by N times to form a constant current driving current Ih to charge the output Gate, and the Gate rises to a high level; when the PWM signal is low, the eighth switching tube 202 Turn off, Ih=0, the ninth switch tube 204 is turned on, and Gate is at low level.

The sampling comparison module 300 is composed of a switch 301, a third capacitor 302, a subtractor 303, and a comparator 304. One end of the switch 301 is connected to the output Gate, and the other end is connected to the upper plate of the third capacitor 302 and the positive input of the comparator 304. The ground pin GND of the lower plate of the third capacitor 302, the control terminal of the switch 301 is connected to the delay signal SH_100ns (see Figure 6 for the specific waveform), the positive input terminal of the subtractor 303 is connected to the output Gate, and the negative input terminal of the subtractor 303 is connected to the chip The internal 0.5V reference, the output terminal of the subtractor 303 is connected to the negative input terminal of the comparator 304 , and the output terminal of the comparator 304 is connected to the input terminal of the re-sampling module 400 . Refer to FIG. 6 for the specific waveform of the comparison signal GH output by the comparator 304 .

The sampling comparison module 300 samples and outputs the Miller plateau voltage of the Gate (approximately equal to the threshold voltage of the external power switch 2) 100 ns after the rising edge of the PWM signal, and holds it on the third capacitor 302, that is, G_sh in FIG. 6 , input To the positive input terminal of the comparator 304; at the same time detect the drive voltage of the output Gate in real time and obtain the real-time voltage (drive voltage-0.5V) through the subtractor 303, and input it to the negative input terminal of the comparator 304; through the comparator 304 Miller The end time of the platform, that is, (driving voltage-0.5V)>Miller platform voltage G_sh at the first sampling moment, that is, the driving voltage is 0.5V higher than the Miller platform voltage G_sh at the first sampling moment, and the comparison signal GH starts from The high level flips to a low level, and it is judged that the Miller platform is over.

The secondary sampling module 400 is a sampling switch, the input end of the sampling switch is connected to the comparator 304, the control end of the sampling switch is connected to the delay signal SH_200ns (see Figure 6 for the specific waveform), and the output end of the switch is connected to the stepping current controller 500 The input terminal and the output terminal of the step current controller 500 are connected to the source terminal of the eighth switching tube 202 to provide the input current I2 for the driving module 200 . The output signal of the secondary sampling module 400 is re-sampled 200ns after the rising edge of the PWM signal. When the GH sampled at 200ns is at a high level, the Miller platform has not yet ended, that is, the time of the Miller platform opened in this cycle>200ns, step by step The input current controller 500 receives the increase signal that GH is high level, and increases the input current I2 by a second step (for example, the second step is 1%), then the constant current drive current Ih also increases accordingly 1%, because Ih increases by 1% in the next cycle, the duration of the Miller platform will be shortened by 1%, and so on until the time of the Miller platform is less than 200ns; on the contrary, when the GH sampled at 200ns is low power In normal times, the Miller platform has ended, that is, the time of the Miller platform opened in this cycle is <200ns, then the step current controller 500 receives the decrease signal that GH is low level, and reduces the input current I2 by one first Step size (for example, the first step size is 1%), then the constant current drive current Ih is also reduced by 1%, and the next cycle because Ih is reduced by 1%, the time of the Miller platform will increase by 1%. Repeat this until the time of the Miller platform is greater than 200ns; in this way, after stabilization, the chip will control the duration of the Miller platform to about 200ns, which has nothing to do with the specifications of the external power switch tube 2, the input voltage, and the ambient temperature , to achieve adaptive soft drive function. The end of the Miller platform means the end of the soft drive. At this time, the driving voltage of the output Gate needs to be increased rapidly in order to better drive the external power switch 2 to make it fully conductive, the conduction resistance is the smallest, and the efficiency is the highest. Therefore, in After the end of the Miller platform, that is, after GH is reversed, the step current controller 500 increases the input current I2 by M times, so that Ih increases rapidly, and the driving voltage of the output Gate rises rapidly (as shown in Figure 6). After the current lasts for 30ns, I2 drops to about 5uA, so that Ih is enough to maintain the Gate voltage at about 12V. In the maintenance phase, Ih=VDD/R, VDD is about 12V, and R is the pull-down resistor inside the chip, generally around 1M, so the maintenance phase Ih is only a few uA, and the power consumption of the whole driving system is very small.

The driving system of the present invention can control the Miller platform at around 200 ns when driving external power switch tubes 2 of different specifications through the self-adaptive driving method, and realize a good soft driving function, and the Miller platform can be controlled after the end of the Miller platform. As a result, the driving voltage VG rises rapidly, and the external power switch tube 2 is quickly and completely turned on, thereby improving efficiency.

The present invention also provides a driving method for the above driving system, including:

Collect driving voltage;

Collecting the Miller plateau voltage at the first sampling moment;

Compare the driving voltage with the Miller platform voltage, and output a comparison signal. When the difference between the driving voltage and the Miller platform is greater than the set voltage, the comparison signal is low; when the driving voltage and the Miller platform voltage When the comparison is not greater than the set voltage, the comparison signal is high level;

Collecting the comparison signal at the second sampling moment;

When the collected comparison signal is at a low level, the drive current of the external power switch tube 2 is reduced by the first step, thereby reducing the drive voltage of the external power switch tube 2 and increasing the Miller plateau time of the next cycle until The end time of the Miller platform is greater than the second collection time;

When the collected comparison signal is at a high level, increase the drive current of the signal external power switch tube 2 with the second step, thereby increasing the drive voltage of the external power switch tube 2 and reducing the Miller plateau time of the next cycle, Until the Miller platform end time is less than the second collection moment;

When the end time of the above-mentioned Miller platform is greater than the second acquisition time or the end time of the above-mentioned Miller platform is less than the second acquisition time, delay the set time, increase the drive current of the external power switch tube 2 with a set multiple and maintain the set time .

While the foregoing disclosure shows exemplary embodiments of the invention, it should be noted that various changes and modifications may be made without departing from the scope defined in the claims. Furthermore, although elements of the invention may be described or claimed in individual form, multiple elements are also contemplated unless expressly limited to a single element.

Claims (12)

1. A driving system, which is arranged in the controller of the AC-DC converter, is used to drive the external power switch tube, is characterized in that, comprises power supply clamping module, sampling comparison module, secondary sampling module, stepping current control and drive modules, of which: The power supply clamping module is used to provide a power supply voltage for the driving module; The drive module is used to drive the external power switch tube to be turned on and off; The sampling comparison module is used to collect the driving voltage of the driving module to the external power switch tube and collect the Miller platform voltage at the first sampling moment, compare the driving voltage with the Miller platform voltage, and output a comparison signal, and the driving voltage and the Miller platform voltage are compared. When the difference of the Miller platform is greater than the set voltage, the comparison signal is low level; when the driving voltage is not greater than the set voltage compared with the Miller platform voltage, the comparison signal is high level; The secondary sampling module is used to sample the comparison signal at the second sampling moment, and when the sampled comparison signal is at a low level, send a reduction signal to the step current controller; when the comparison signal is at a high level, Send an increase signal to the stepping current controller; The step current controller is used to provide an input current to the drive module, and when the step current controller receives a reduction signal, it reduces the input current with a first step; the step current controller receives when increasing the signal, increasing the input current by a second step size; Wherein, the drive module is also used to amplify the input current, the input current increases, the time of the Miller platform in the next cycle is reduced, the input current decreases, and the time of the next cycle of the Miller platform is increased; the secondary The comparison signal collected by the sampling module sends an amplified signal to the stepping current controller when the level shift occurs in the adjacent cycle, and the stepping current controller delays the setting time to increase the input current by the set multiple and maintain the set time. 2. The driving system according to claim 1, wherein the power supply clamping module includes a second resistor, a second regulator tube and a fifth switch tube, one end of the second resistor is connected to a pull-up voltage, so The other end of the second resistor is respectively connected to the fifth switch tube and the second voltage regulator tube, the second voltage regulator tube is used to clamp the conduction voltage of the fifth switch tube, the fifth switch tube is turned on, Supply power to the drive module. 3. The driving system according to claim 2, wherein the fifth switch tube is an NMOS tube, one end of the second resistor is connected to a pull-up voltage, and the other end of the second resistor is connected to a regulator tube The cathode of the fifth switching tube is connected to the grid of the fifth switching tube, the anode of the second voltage regulator tube is grounded, the drain of the fifth switching tube is connected to the pull-up voltage, and the source of the fifth switching tube is used to supply power to the driving module. 4. The drive system according to claim 1, wherein the drive module comprises a second current mirror, an eighth switch tube, a ninth switch tube, a third resistor and an inverter, and the second current mirror It includes a sixth switch tube and a seventh switch tube, one end of the sixth switch tube is connected to the power supply clamping module, the other end of the sixth switch tube is connected to the step current controller through the eighth switch tube, and the sixth switch tube is connected to the step current controller. The eight switch tubes are used to control the turn-off and conduction of the step current controller and the seventh switch tube, one end of the seventh switch tube is connected to the power supply clamping module, and the other end of the seventh switch tube is respectively connected to the third resistor connected to the ninth switch tube, the inverter is used to control the turn-on and turn-off of the ninth switch tube, the ninth switch tube and the eighth switch tube are not turned on at the same time, the third resistor is a pull-down resistor, The ninth switch tube is used to pull down the driving voltage to a low level. 5. The drive system according to claim 4, characterized in that, the sixth switch tube and the seventh switch tube are PMOS tubes, the eighth switch tube and the ninth switch tube are NMOS tubes, and the sixth switch tube Both the source stages of the switching tube and the seventh switching tube are connected to the power supply clamping module, the gate and drain of the sixth switching tube are short-circuited and connected to the grid of the seventh switching tube and the drain of the eighth switching tube, and the eighth switching tube The gate of the tube is used to input the PWM signal, the source of the eighth switch tube is connected to the output of the stepping current controller, the drain of the seventh switch tube is respectively connected to one end of the third resistor and the drain of the ninth switch tube, The other end of the third resistor and the source of the ninth switch tube are grounded, the gate of the ninth switch tube is connected to the output terminal of the inverter, and the input terminal of the inverter is connected to the PWM signal. 6. The driving system according to claim 1, wherein the sampling comparison module comprises a switch, a third capacitor, a subtractor and a comparator, one end of the switch is connected to the driving voltage, and the other end of the switch is connected to The upper plate of the third capacitor and the positive input terminal of the comparator, the switch is used to control the on and off of the driving voltage and the positive input terminal of the comparator, thereby controlling the first sampling moment, the lower pole of the third capacitor The board is grounded, the positive input terminal of the subtractor is connected to the driving voltage, the negative input terminal decompression reference, the decompression reference is the set voltage, the output terminal of the subtractor is connected to the negative input terminal of the comparator, and the comparison The output of the tor is connected to the subsampling module. 7. The driving system according to claim 1, wherein the secondary sampling module is a sampling switch. 8. The drive system according to claim 1, wherein the step current control comprises a bi-directional counter and a current controller, the bi-directional counter is used to control the step size of increasing or decreasing the input current, the The current controller is used to increase or decrease the input current according to the step size controlled by the bi-directional counter. 9. A driving method for driving an external power switch tube of an AC-DC converter, characterized in that, comprising: Collect driving voltage; Collecting the Miller plateau voltage at the first sampling moment; Compare the driving voltage with the Miller platform voltage, and output a comparison signal. When the difference between the driving voltage and the Miller platform is greater than the set voltage, the comparison signal is low; when the driving voltage and the Miller platform voltage When the comparison is not greater than the set voltage, the comparison signal is high level; Collecting the comparison signal at the second sampling moment; When the collected comparison signal is low level, reduce the drive current of the external power switch tube with the first step, thereby reducing the drive voltage of the external power switch tube, increasing the Miller plateau time of the next cycle until Miller The platform end time is greater than the second collection time; When the collected comparison signal is at a high level, increase the drive current of the signal external power switch tube with the second step length, thereby increasing the drive voltage of the external power switch tube, reducing the Miller plateau time of the next cycle until m The end time of the Le platform is less than the second collection moment; When the end time of the Miller platform is greater than the second acquisition time or the end time of the Miller platform is less than the second acquisition time, delay the set time, increase the driving current of the external power switch tube by a set multiple and maintain the set time. 10. A controller, characterized by comprising the drive system according to any one of claims 1-8. 11. The controller according to claim 10, further comprising an internal power supply and reference system, a power supply voltage judging system, an overload protection system, a pulse width modulation system, a cycle-by-cycle overcurrent protection system and a logic system, wherein, The internal power supply and reference system is used to generate the internal voltage required by each system through the power supply voltage and provide a current-limiting reference for the cycle-by-cycle overcurrent protection system; The power supply voltage judging system is used to judge whether the power supply voltage is undervoltage or overvoltage, if the power supply voltage is undervoltage or overvoltage, send a protection signal to the logic system, if the power supply voltage is not undervoltage or overvoltage, send a power supply voltage normal signal to logic system; The overload protection system is used to judge whether the load is overloaded, if the load is overloaded, send a protection signal to the logic system, and if the load is not overloaded, send a load normal signal to the logic system; The logic system is used to generate a PWM signal and send it to the drive system when receiving the normal signal of the power supply voltage from the power supply voltage judging system and the normal load signal of the overload protection system, otherwise no PWM signal is generated; The cycle-by-cycle overcurrent protection system is used to compare the primary side current of the AC-DC transformer with the current-limiting reference in each cycle, and when the primary-side current of the transformer reaches the current-limiting reference, cycle shutdown is performed. 12. An AC-DC converter, characterized in that it includes a transformer, an external power switch tube and the controller according to claim 10 or 11, the transformer includes a primary winding, a secondary winding and an auxiliary winding, the transformer The primary winding of the transformer is connected to the external power switch tube, the auxiliary winding of the transformer is used to supply power to the controller, and the secondary winding of the transformer is used to output energy to the load and output a feedback voltage to the controller; The controller is used to determine the duty ratio of the PWM signal according to the feedback voltage of the transformer, and generate a time-constant driving voltage of the Miller platform according to the PWM signal, and the driving voltage is used to drive the external power switch tube; The external power switch tube is used to control the transformation of the transformer between the energy storage state and the degaussing state. When the external power switch tube is turned on, the transformer is in the energy storage state, and the primary winding stores energy; after the external power switch tube is turned off, The transformer enters the degaussing stage, and the energy of the transformer is converted to the secondary winding, and the energy is output from the secondary winding to the load.

Images