CN109617385B - Capacitor precharge circuit - Google Patents
Capacitor precharge circuit Download PDFInfo
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- CN109617385B CN109617385B CN201910110881.5A CN201910110881A CN109617385B CN 109617385 B CN109617385 B CN 109617385B CN 201910110881 A CN201910110881 A CN 201910110881A CN 109617385 B CN109617385 B CN 109617385B
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- 239000003990 capacitor Substances 0.000 title claims abstract description 94
- 238000001514 detection method Methods 0.000 claims abstract description 48
- 230000000087 stabilizing effect Effects 0.000 claims description 13
- 230000005669 field effect Effects 0.000 claims description 10
- 229910044991 metal oxide Inorganic materials 0.000 claims description 8
- 150000004706 metal oxides Chemical class 0.000 claims description 8
- 239000004065 semiconductor Substances 0.000 claims description 8
- 238000001914 filtration Methods 0.000 claims description 5
- 239000004568 cement Substances 0.000 abstract description 15
- 238000000034 method Methods 0.000 description 13
- 238000010586 diagram Methods 0.000 description 11
- 230000002159 abnormal effect Effects 0.000 description 3
- 238000013459 approach Methods 0.000 description 1
- 230000001276 controlling effect Effects 0.000 description 1
- 230000000694 effects Effects 0.000 description 1
- 230000000750 progressive effect Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
- 230000006641 stabilisation Effects 0.000 description 1
- 238000011105 stabilization Methods 0.000 description 1
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/32—Means for protecting converters other than automatic disconnection
- H02M1/34—Snubber circuits
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Abstract
The invention discloses a capacitor precharge circuit. The capacitive precharge circuit includes: an inductor L1, a switching tube Q2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a voltage reference, a capacitor C2, a diode D1, a drive control circuit and a current detection circuit; the capacitor precharge circuit of the invention is adopted to replace components such as PTC resistor, NTC resistor or cement resistor in the traditional power circuit, thereby avoiding the problem of repeated power on/off in a very short interval time in a high temperature environment, and further improving the reliability of the electronic circuit.
Description
Technical Field
The invention relates to the field of power electronics, in particular to a capacitor precharge circuit.
Background
At present, the performance of high-precision equipment on a power supply is higher and higher, and in order to improve the input-output characteristics of the power supply, a relatively large capacitor is generally added at the input-output end of the power supply, and the addition of the capacitors at the input-output end can improve the dynamic characteristics and the ripple characteristics of the power supply. However, the addition of a large capacitor causes a large rush current, resulting in an excessive rush current of the power supply device. For example: a capacitor at the input/output of the BOOST topology of the switching direct current (the BOOST converter, BOOST); a capacitor at the output of a BOOST-type power factor correction (BOOST-Power Factor Correction, BOOST-PFC) circuit; the alternating current is input, and bus capacitors and the like are connected after full-wave, half-wave or thyristor rectification, and the capacitors can cause large impact current at the moment of starting up, and the excessive impact current at the input end is needed to provide a power supply with higher power; the impact current at the output end can increase the failure risk of the electronic circuit, and meanwhile, the design needs to be enough to be several times larger than the design of the electronic circuit in normal operation, so that the volume and the cost of the power supply can be increased greatly.
In order to suppress the surge current caused by the capacitor during the power-on process, the output capacitor is usually precharged by adding a positive temperature coefficient (Positive Temperature Coeffficient, PTC) resistor or a negative temperature coefficient (Nagetive Temperature Coefficient, NTC) resistor or a cement resistor to suppress the surge current during the power-on process.
In order to suppress the surge current during the start-up process, the existing precharge circuit is shown in fig. 1, wherein R is a PTC resistor, an NTC resistor, or a cement resistor; before starting up, the direct current input voltage is filtered by C1 and then is charged by L2, D2 and R to the output capacitor C3; when the voltage of the capacitor C3 is charged to be close to the input voltage, the main power circuit controls the relay to be closed; the power switch tube slowly increases the output voltage to reach the set BOOST voltage by slowly starting the duty ratio. However, if the PTC resistor is selected by R, the power supply is repeatedly turned on and off in a high-temperature environment or in a short time interval, the PTC impedance will become large, so that the power supply cannot be turned on normally; in a low temperature environment, the PTC resistance will be small again, resulting in excessive rush current at start-up. If R selects NTC resistance, in low temperature environment, NTC resistance will become large, which will cause power supply to be started up normally; in a high-temperature environment, or the power supply repeatedly starts and shuts down in a short interval time, the NTC impedance becomes very small, and the impact current is too large during starting up; if the cement resistor is selected by R, although the high-low temperature characteristic is good, a plurality of cement resistors are often required to be connected in series and parallel in one power supply, so that the volume and the weight of the power supply are greatly increased, and the power supply is difficult to apply in environments with high requirements on the weight and the volume.
Therefore, the existing precharge circuit still has the problem of overlarge startup surge current, thereby increasing the volume and cost of the power supply and further causing low reliability of the precharge circuit.
Disclosure of Invention
The invention aims to provide a capacitor pre-charging circuit, which solves the problems of overlarge starting-up impact current and low reliability of the traditional pre-charging circuit.
In order to achieve the above object, the present invention provides the following solutions:
a capacitor precharge circuit, which is applied to a power supply circuit, wherein the power supply circuit comprises a BOOST circuit, a BOOST-PFC circuit and an alternating current rectifying and filtering circuit; the capacitive precharge circuit includes: an inductor L1, a switching tube Q2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a voltage reference, a capacitor C2, a diode D1, a drive control circuit and a current detection circuit;
one end of the inductor L1 is connected with the input end of the power supply circuit, the other end of the inductor L1 is connected with the positive electrode of the diode D1, and the negative electrode of the diode D1 is respectively connected with the collector electrode of the switching tube Q1, one end of the resistor R1 and one end of the resistor R2; the other end of the resistor R1 is connected with the collector of the switch tube Q2, the base of the switch tube Q2 is respectively connected with the other end of the resistor R2 and the first end of the voltage reference, and the emitter of the switch tube Q2 is connected with one end of the capacitor C2; one end of the resistor R3 is respectively connected with the first end of the drive control circuit and the first end of the current detection circuit; the other end of the resistor R3 is respectively connected with one end of the resistor R4 and the second end of the voltage reference; the other end of the capacitor C2 is respectively connected with the other end of the resistor R4, the third end of the voltage reference, one end of the resistor R5 and the output end of the power supply circuit;
the second end of the drive control circuit is connected with the second end of the current detection circuit, and the third end of the drive control circuit is connected with the base electrode of the switch tube Q1; the emitter of the switching tube Q1 is connected to the other end of the resistor R5 and the third end of the current detection circuit, respectively.
Optionally, the driving control circuit is a totem pole circuit;
the totem pole circuit comprises a switching tube Q4 and a switching tube Q5;
the emitter of the switch tube Q4 is connected with one end of the R3; the base electrode of the switching tube Q4 is respectively connected with the base electrode of the switching tube Q5 and an operational amplifier in the current detection circuit; the collector of the switching tube Q4 is respectively connected with the collector of the switching tube Q5 and the base of the switching tube Q1; the emitter of the switching tube Q5 is connected with the output end of the power supply circuit.
Optionally, the method further comprises: resistor R6, resistor R7, and diode D3;
the resistor R7 is arranged between the current detection circuit and one end of the resistor R3; one end of the resistor R7 is respectively connected with one end of the resistor R3 and one end of the resistor R6, and the other end of the resistor R7 is respectively connected with an operational amplifier in the current detection circuit and the negative electrode of the diode D3; the positive electrode of the diode D3 is connected with the output end of the power supply circuit.
Optionally, the current detection current specifically includes: an operational amplifier, a resistor R9, a resistor R10, and a resistor R11;
the positive electrode of the operational amplifier is connected with one end of the resistor R10, and the negative electrode of the operational amplifier is respectively connected with one end of the resistor R9 and one end of the resistor R11; the other end of the resistor R10 is connected with the other end of the resistor R5; the other end of the resistor R11 is connected with the other end of the resistor R6.
Optionally, the method further comprises: a capacitor C4, a capacitor C5, and a resistor R8;
the capacitor C4 is connected with the resistor R8 in parallel, and one end of the capacitor C4 is connected with the other end of the resistor R6 and the other end of the resistor R11 respectively; the other end of the capacitor C4 is respectively connected with the anode of the diode D3, the emitter of the switch tube Q5, one end of the capacitor C5 and the output end of the power supply circuit; the other end of the capacitor C5 is connected to the other end of the resistor R5 and the other end of the resistor R10, respectively.
Optionally, the switching tube Q1 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device;
the switch tube Q2 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device;
the switch tube Q4 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device;
the switch tube Q5 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device.
Optionally, the inductor L1 is a patch inductor, a plug-in inductor, or a planar inductor drawn by a multilayer printed circuit board.
The capacitive precharge circuit of claim 1, wherein said diode D1 is an anti-reflection diode.
According to the specific embodiment provided by the invention, the invention discloses the following technical effects: the invention discloses a capacitor precharge circuit, which replaces a PTC resistor, an NTC resistor or a cement resistor in a traditional power circuit, solves the problems of abnormal starting and the like caused by the PTC resistor and the NTC resistor in the repeated switching-on and switching-off process in a high-temperature environment or a low-temperature environment, and improves the reliability of an electronic circuit; the problems of volume, weight and the like of cement resistance in the circuit are improved, and conditions are provided for miniaturization and high power density of the power supply.
Drawings
In order to more clearly illustrate the embodiments of the present invention or the technical solutions of the prior art, the drawings that are needed in the embodiments will be briefly described below, it being obvious that the drawings in the following description are only some embodiments of the present invention, and that other drawings may be obtained according to these drawings without inventive effort for a person skilled in the art.
FIG. 1 is a circuit diagram of a prior art precharge circuit according to the present invention;
FIG. 2 is a circuit diagram of a capacitor precharge circuit according to the present invention applied to a BOOST circuit;
fig. 3 is a circuit diagram of the capacitor precharge circuit applied to a BOOST-PFC circuit according to the present invention;
FIG. 4 is a circuit diagram of the capacitor precharge circuit of the present invention applied to an AC rectifying and filtering circuit;
FIG. 5 is a circuit diagram of another capacitive precharge circuit according to an embodiment of the present invention, which is an improvement over the capacitive precharge circuit of FIG. 2;
FIG. 6 is a waveform diagram of the key nodes in FIG. 5 according to the present invention;
fig. 7 is an expanded view of the waveform based on fig. 6 provided by the present invention.
Detailed Description
The following description of the embodiments of the present invention will be made clearly and completely with reference to the accompanying drawings, in which it is apparent that the embodiments described are only some embodiments of the present invention, but not all embodiments. All other embodiments, which can be made by those skilled in the art based on the embodiments of the invention without making any inventive effort, are intended to be within the scope of the invention.
The invention aims to provide a capacitor precharge circuit which can improve the reliability of an electronic circuit.
In order that the above-recited objects, features and advantages of the present invention will become more readily apparent, a more particular description of the invention will be rendered by reference to the appended drawings and appended detailed description.
As shown in the dashed boxes in fig. 2-4, a capacitor precharge circuit is applied to a power supply circuit, and the power supply circuit comprises a BOOST circuit, a BOOST-PFC circuit and an ac rectifying and filtering circuit; the capacitive precharge circuit includes: an inductor L1, a switching tube Q2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a voltage reference, a capacitor C2, a diode D1, a drive control circuit and a current detection circuit; one end of the inductor L1 is connected with the input end of the power supply circuit, the other end of the inductor L1 is connected with the positive electrode of the diode D1, and the negative electrode of the diode D1 is respectively connected with the collector electrode of the switching tube Q1, one end of the resistor R1 and one end of the resistor R2; the other end of the resistor R1 is connected with the collector of the switch tube Q2, the base of the switch tube Q2 is respectively connected with the other end of the resistor R2 and the first end of the voltage reference, and the emitter of the switch tube Q1 is connected with one end of the capacitor C2; one end of the resistor R3 is respectively connected with the first end of the drive control circuit and the first end of the current detection circuit; the other end of the resistor R3 is respectively connected with one end of the resistor R4 and the second end of the voltage reference; the other end of the capacitor C2 is respectively connected with the other end of the resistor R4, the third end of the voltage reference, one end of the resistor R5 and the output end of the power supply circuit; the second end of the drive control circuit is connected with the second end of the current detection circuit, and the third end of the drive control circuit is connected with the base electrode of the switch tube Q1; the emitter of the switching tube Q1 is connected to the other end of the resistor R5 and the third end of the current detection circuit, respectively. The resistor R1, the resistor R2, the resistor R3, the resistor R4, the switching tube Q2 and the voltage reference form a linear power supply, and the linear power supply can be replaced by other linear voltage circuits.
Fig. 2 is a circuit diagram of the capacitor precharge circuit provided by the invention applied to a BOOST circuit, as shown in fig. 2, the precharge circuit provided by the invention replaces a PTC resistor, an NTC resistor or a cement resistor in the BOOST circuit.
Before the BOOST main power circuit works, the precharge circuit charges the output capacitor C3 to the input voltage; after the direct-current input voltage passes through the filter capacitor C2, power is supplied to the linear voltage stabilizing circuit, so that a stable voltage VDD based on a reference point is obtained, and the VDD is used for supplying power to the drive control circuit and the current detection circuit; the current detection circuit detects a voltage signal converted from the current on the resistor R5 and feeds the voltage signal back to the drive control circuit, and the drive control circuit judges the magnitude of the current to control the on-off of the switching tube Q1.
When the switching tube Q1 is turned on, the input dc charges the output capacitor C3 through the filter inductor L1, the diode D1, and the switching tube Q1. The charging current rises with a certain slope, when the charging current value reaches the set maximum charging current, the current detection circuit feeds back to the drive control circuit, the drive control circuit turns off the switch tube Q1, and the capacitor C3 voltage is charged up after a plurality of periods of charging; when the voltage of the capacitor C3 approaches the input voltage, the main power circuit closes the relay K1, and the pre-charging circuit is not effective.
When the relay K1 is closed, the main power switching tube Q3 of the BOOST topology starts to work, and the duty ratio is changed from small to large according to the setting of the slow-start time until the voltage on the output capacitor C3 reaches the set BOOST output voltage; because of the anti-reverse diode D1, the output voltage cannot be reversely poured to the direct current input side through the precharge circuit; the precharge circuit provided by the invention replaces the PTC resistor, the NTC resistor or the cement resistor, solves the problems of abnormal starting and the like caused by the PTC resistor and the NTC resistor in the repeated switching-on and switching-off processes in the high-temperature environment and the low-temperature environment, and improves the reliability of the electronic circuit; the problems of volume, weight and the like of cement resistance in the circuit are improved, and conditions are provided for miniaturization and high power density of the power supply.
Normally, the BOOST circuit does not support the output short-circuit protection function, but the addition of the precharge circuit provided by the invention provides a solution for the short-circuit protection of the BOOST circuit.
When the output detects a short-circuit current, the main power turns off the relay K1, at which point the precharge circuit starts to function. As the output end is in a short circuit state, the charging current can rise sharply as long as the switching tube Q1 is opened, when the charging current reaches the limit value, the driving control circuit can turn off the switching tube Q1, and as long as the output end is in short circuit, the voltage of the capacitor C3 can not be charged, and the main power can not be closed K1; until the short circuit state of the output end disappears, the capacitor C3 is charged to the input voltage, the main power can not close K1, and the switching tube Q3 starts to work.
The D1 is realized by adopting an independent diode or two diodes which are respectively provided with a switch tube Q1 and two branches of linear voltage stabilization. The switching tube Q1 is realized by NMOS or is a control switch, a bipolar device or a field effect device. The current detection is realized by adopting a resistor to detect current or a sensor, and the driving control circuit is realized by adopting a discrete component totem pole driving or an integrated driving chip; or a chip integrated with current detection and drive control to realize the current detection and drive control. The linear voltage stabilizing circuit is realized by adopting discrete components or three-terminal voltage stabilizing chips.
Fig. 3 is a circuit diagram of the capacitor precharge circuit applied to a BOOST-PFC circuit according to the present invention. The precharge circuit provided by the invention replaces a PTC resistor, an NTC resistor or a cement resistor in a BOOST-PFC circuit.
Before the BOOST-PFC main power circuit works, the precharge circuit charges the output capacitor C3 to the magnitude of the input ac peak voltage; the alternating-current input voltage is rectified into M-shaped waves through bridge rectification, and then the M-shaped waves pass through a filter inductor L1 and an anti-reflection diode D1 to supply power to the linear voltage stabilizing circuit. When the input voltage is larger than the VDD voltage, the linear voltage stabilizing circuit works normally to obtain a stabilized voltage VDD based on a reference point, and the VDD supplies power for the drive control circuit and the current detection circuit; the current detection circuit detects a voltage signal converted by the current on R5 and feeds the voltage signal back to the drive control circuit, and the drive control circuit judges the magnitude of the current to control the on-off of the switching tube Q1.
When the switching tube Q1 is turned on, the input dc charges the output capacitor C3 through the filter inductor L1, the diode D1, and the switching tube Q1. The charging current rises with a certain slope, when the charging current value reaches the set maximum charging current, the current detection circuit feeds back to the drive control circuit, the drive control circuit turns off the switch tube Q1, and the capacitor C3 voltage is charged up after a plurality of periods of charging; when the voltage of the capacitor C3 is close to the peak voltage of the alternating current input, the main power circuit closes the relay K1, and the pre-charging circuit does not work any more.
When the relay K1 is closed, the main power switching tube Q3 of the BOOST-PFC circuit starts to work, and the duty ratio can be changed according to a loop according to the setting of the slow-up time, so that the output voltage is slowly started. Until the voltage above the output capacitor C3 reaches the set PFC output voltage; because of the anti-reverse diode D1, the output voltage cannot be reversely poured to the direct current input side through the precharge circuit; the precharge circuit provided by the invention replaces the PTC resistor, the NTC resistor or the cement resistor, solves the problems of abnormal starting and the like caused by the PTC resistor and the NTC resistor in the repeated switching-on and switching-off processes in the high-temperature environment and the low-temperature environment, and improves the reliability of the electronic circuit; the problems of volume, weight and the like of cement resistance in the circuit are improved, and conditions are provided for miniaturization and high power density of the power supply.
Normally, the BOOST-PFC circuit does not support the output short-circuit protection function, but the addition of the precharge circuit provides a solution for short-circuit protection of the BOOST-PFC circuit.
When the output detects a short-circuit current, the main power turns off the relay K1, at which point the precharge circuit starts to function. As the output end is in a short circuit state, the charging current can rise rapidly as long as the switching tube Q1 is opened, and when the charging current reaches the limit value, the driving control circuit can turn off the switching tube Q1; as long as the output end is short-circuited, the voltage of the capacitor C3 cannot be charged, and the main power circuit cannot close the relay K1; until the short circuit state of the output end disappears, after the capacitor C3 is charged to be close to the peak voltage of the alternating current input, the main power can not close the relay K1, and the Q3 starts to work.
The D1 is realized by adopting an independent diode or two diodes which are respectively provided with a switch tube Q1 and two linear voltage stabilizing branches; the switching tube Q1 is realized by NMOS or is used for controlling a switch, a bipolar device or a field effect device; the current detection is realized by adopting a resistor to detect current or a sensor, and the driving control circuit is realized by adopting a discrete component totem pole driving or an integrated driving chip; or a chip integrated with current detection and drive control to realize the current detection and drive control. The linear voltage stabilizing circuit is realized by adopting discrete components or three-terminal voltage stabilizing chips.
Fig. 4 is a circuit diagram of the capacitor precharge circuit applied to the ac rectifying and filtering circuit. The precharge circuit provided by the invention replaces PTC resistor, NTC resistor or cement resistor in the circuit.
The precharge circuit will charge the output capacitor C3 to the magnitude of the input ac peak voltage before the relay K1 is closed. The alternating-current input voltage is rectified into M-shaped waves through bridge rectification, and then the M-shaped waves pass through a filter inductor L1 and an anti-reflection diode D1 to supply power to the linear voltage stabilizing circuit; when the voltage is greater than the VDD voltage, the linear voltage stabilizing circuit works normally to obtain a stable voltage VDD based on a reference point, and the VDD supplies power for the drive control circuit and the current detection circuit. The current detection circuit detects a voltage signal converted by the current on R5 and feeds the voltage signal back to the drive control circuit, and the drive control circuit judges the magnitude of the current to control the on-off of the switching tube Q1.
When the switching tube Q1 is turned on, the input dc charges the output capacitor C3 through the filter inductor L1, the diode D1, and the switching tube Q1. The charging current rises with a certain slope, when the charging current value reaches the set maximum charging current, the current detection circuit feeds back to the drive control circuit, the drive control circuit turns off the switch tube Q1, and the capacitor C3 voltage is charged up after a plurality of periods of charging. When the voltage of the capacitor C3 is close to the peak voltage of the alternating current input, the main power circuit closes the relay K1, and the pre-charging circuit does not work any more.
FIG. 5 is a circuit diagram of another capacitor precharge circuit according to the present invention, which is an improvement of the capacitor precharge circuit according to FIG. 2, wherein a linear voltage stabilizing source is formed by a resistor R1, a resistor R2, a resistor R3, a resistor R4, a diode D4, and a switching tube Q2 as shown in FIG. 5; the diode D4 adopts 431 as a voltage reference of a linear power supply, a resistor R3 and a resistor R4 form a feedback network, and the switching tube Q2 works in a linear region for NMOS; the linear power supply output powers the current sense and drive control circuit based on the regulated voltage VDD at the reference point.
The resistor R9, the resistor R10, the resistor R11 and the operational amplifier U1 form a current detection and switching tube Q1 control signal circuit; the drive control circuit and the current detection circuit may be integrated into one chip. The positive electrode of the operational amplifier is connected with one end of the resistor R10, and the negative electrode of the operational amplifier is respectively connected with one end of the resistor R9 and one end of the resistor R11; the other end of the resistor R10 is connected with the other end of the resistor R5; the other end of the resistor R11 is connected with the other end of the resistor R6; the resistor R7 is arranged between one ends of the current detection circuit and the resistor R3; one end of the resistor R7 is respectively connected with one end of the resistor R3 and one end of the resistor R6, and the other end of the resistor R7 is respectively connected with an operational amplifier in the current detection circuit and the negative electrode of the diode D3; the positive electrode of the diode D3 is connected with the output end of the power supply circuit; the capacitor C4 is connected with the resistor R8 in parallel, and one end of the capacitor C4 is connected with the other end of the resistor R6 and the other end of the resistor R11 respectively; the other end of the capacitor C4 is respectively connected with the anode of the diode D3, the emitter of the switch tube Q5, one end of the capacitor C5 and the output end of the power supply circuit; the other end of the capacitor C5 is connected to the other end of the resistor R5 and the other end of the resistor R10, respectively.
VDD is divided by a resistor R6 and a resistor R8 to be used as a reference for hysteresis comparison, and charging current flowing through R5 is converted into voltage to be sent to the other end of the hysteresis comparator; the switching tube Q4 and the switching tube Q5 form a totem pole circuit for driving the switching tube Q1; the drive control circuit and the current detection circuit may be integrated into one chip. The emitter of the switch tube Q4 is connected with one end of the R3; the base electrode of the switching tube Q4 is respectively connected with the base electrode of the switching tube Q5 and an operational amplifier in the current detection circuit; the collector of the switching tube Q4 is respectively connected with the collector of the switching tube Q5 and the base of the switching tube Q1; the emitter of the switching tube Q5 is connected with the output end of the power supply circuit.
Before the BOOST main power circuit works, the precharge circuit charges the output capacitor C3 to the input voltage; the direct current input voltage is supplied to the linear voltage stabilizing circuit through the filter inductor L1 and the anti-reflection diode D1, and the stabilized voltage VDD based on the reference point is obtained.
When the switching tube Q1 is turned on, the input direct current passes through the filter inductor L1, the diode D1 and the switching tube Q1 charges the output capacitor C3, the charging current rises with a certain slope, and when the charging current value reaches the set maximum charging current, the hysteresis comparator turns over, and the totem pole driving circuit turns off the switching tube Q1.
When the switching tube Q1 is turned off, the hysteresis comparator turns over after the charging current is smaller than the lower limit of the hysteresis comparator, and the totem pole driving circuit can turn on the switching tube Q1. After a plurality of cycles of charging, the capacitor C3 voltage is charged high; when the voltage of the capacitor C3 is close to the input voltage, the linear power supply stops working, the main power circuit can close the relay K1, and the pre-charging circuit does not work any more.
The current detection is realized by adopting a resistor to detect current or a sensor, and the driving control circuit is realized by adopting a discrete component totem pole driving or an integrated driving chip; or a chip integrated with current detection and drive control to realize current detection and drive control; the linear voltage-stabilizing power supply circuit is realized by adopting discrete components or three-terminal voltage-stabilizing chips.
Fig. 6 is a waveform diagram of a key node in fig. 5 provided by the present invention, as shown in fig. 6, wherein the key node is a waveform of voltage and current for determining a charging process of a bus capacitor in a power-up process, and fig. 7 is an expanded view based on the waveform of fig. 6 provided by the present invention; the output voltage waveform of the output capacitor C3 to ground is c3_vout in fig. 7, where c3_vout is the capacitor voltage of the capacitor C3); the waveform of the gate and the source of the switching tube Q1 is Q1-Vgs in FIG. 7, and Q1-Vgs is the driving voltage of the switching tube Q1; the waveform of the current detection of the reference point after the current flows through the resistor R5 is shown as R5_Isense in FIG. 7, wherein R5_Isense is the detection voltage on the current detection resistor R5; the charging current waveform is i_charge in fig. 7, and i_charge is the charging current waveform of the capacitor C3.
As can be seen from fig. 6-7, the voltage across capacitor C3 slowly rises with the switching of switching tube Q1, eventually being charged near the input voltage 300 Vdc. When the switching tube Q1 is conducted, the charging current rises, and when a certain value is reached, the driving control circuit turns off the switching tube Q1; when the current drops to a certain value, the drive control circuit turns on the switching tube Q1 to continue charging. As can be seen from the waveform, the precharge circuit is capable of completing precharge of the output capacitor.
Because the input and output capacitors of the power supply can generate large impact current in the starting process, and the reliability problem is caused by the excessive impact current, when the large capacitors are at the input and output ends of the power supply, the capacitor precharge circuit provided by the invention is adopted to precharge the capacitors, so that the impact current in the starting process is restrained, the magnitude of precharge current can be set, and the precharge time is controlled; the volume of the power supply can be reduced; the precharge circuit provided by the invention replaces components such as PTC resistor, NTC resistor or cement resistor in the power supply circuit, and can effectively improve the reliability of the electronic circuit.
In the present specification, each embodiment is described in a progressive manner, and each embodiment is mainly described in a different point from other embodiments, and identical and similar parts between the embodiments are all enough to refer to each other.
The principles and embodiments of the present invention have been described herein with reference to specific examples, the description of which is intended only to assist in understanding the methods of the present invention and the core ideas thereof; also, it is within the scope of the present invention to be modified by those of ordinary skill in the art in light of the present teachings. In view of the foregoing, this description should not be construed as limiting the invention.
Claims (4)
1. The capacitor pre-charging circuit is characterized by being applied to a power supply circuit, wherein the power supply circuit comprises a BOOST circuit, a BOOST-PFC circuit and an alternating current rectifying and filtering circuit; the capacitive precharge circuit includes: an inductor L1, a switching tube Q2, a resistor R1, a resistor R2, a resistor R3, a resistor R4, a resistor R5, a voltage reference, a capacitor C2, a diode D1, a drive control circuit and a current detection circuit; the driving control circuit is a totem pole circuit; the totem pole circuit comprises a switching tube Q4 and a switching tube Q5; the emitter of the switch tube Q4 is connected with one end of the R3; the base electrode of the switching tube Q4 is respectively connected with the base electrode of the switching tube Q5 and an operational amplifier in the current detection circuit; the collector of the switching tube Q4 is respectively connected with the collector of the switching tube Q5 and the base of the switching tube Q1; the emitter of the switch tube Q5 is connected with the output end of the power supply circuit;
further comprises: resistor R6, resistor R7, and diode D3; the resistor R7 is arranged between the current detection circuit and one end of the resistor R3; one end of the resistor R7 is respectively connected with one end of the resistor R3 and one end of the resistor R6, and the other end of the resistor R7 is respectively connected with an operational amplifier in the current detection circuit and the negative electrode of the diode D3; the positive electrode of the diode D3 is connected with the output end of the power supply circuit;
the current detection current specifically includes: an operational amplifier, a resistor R9, a resistor R10, and a resistor R11; the positive electrode of the operational amplifier is connected with one end of the resistor R10, and the negative electrode of the operational amplifier is respectively connected with one end of the resistor R9 and one end of the resistor R11; the other end of the resistor R10 is connected with the other end of the resistor R5; the other end of the resistor R11 is connected with the other end of the resistor R6;
one end of the inductor L1 is connected with the input end of the power supply circuit, the other end of the inductor L1 is connected with the positive electrode of the diode D1, and the negative electrode of the diode D1 is respectively connected with the collector electrode of the switching tube Q1, one end of the resistor R1 and one end of the resistor R2; the other end of the resistor R1 is connected with the collector of the switch tube Q2, the base of the switch tube Q2 is respectively connected with the other end of the resistor R2 and the first end of the voltage reference, and the emitter of the switch tube Q2 is connected with one end of the capacitor C2; one end of the resistor R3 is respectively connected with the first end of the drive control circuit and the first end of the current detection circuit; the other end of the resistor R3 is respectively connected with one end of the resistor R4 and the second end of the voltage reference; the other end of the capacitor C2 is respectively connected with the other end of the resistor R4, the third end of the voltage reference, one end of the resistor R5 and the output end of the power supply circuit; the diode D1 is realized by adopting an independent diode or two diodes which are respectively provided with a switching tube Q1 and two linear voltage stabilizing branches; the inductor L1 is a patch inductor, a plug-in inductor or a plane inductor drawn by a multilayer printed circuit board;
the second end of the drive control circuit is connected with the second end of the current detection circuit, and the third end of the drive control circuit is connected with the base electrode of the switch tube Q1; the emitter of the switching tube Q1 is connected to the other end of the resistor R5 and the third end of the current detection circuit, respectively.
2. The capacitive precharge circuit of claim 1, further comprising: a capacitor C4, a capacitor C5, and a resistor R8;
the capacitor C4 is connected with the resistor R8 in parallel, and one end of the capacitor C4 is connected with the other end of the resistor R6 and the other end of the resistor R11 respectively; the other end of the capacitor C4 is respectively connected with the anode of the diode D3, the emitter of the switch tube Q5, one end of the capacitor C5 and the output end of the power supply circuit; the other end of the capacitor C5 is connected to the other end of the resistor R5 and the other end of the resistor R10, respectively.
3. The capacitor precharge circuit of claim 2, wherein said switching tube Q1 is an N-type metal oxide semiconductor, a control switch, a bipolar device, or a field effect device;
the switch tube Q2 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device;
the switch tube Q4 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device;
the switch tube Q5 is an N-type metal oxide semiconductor tube, a control switch, a bipolar device or a field effect device.
4. The capacitive precharge circuit of claim 1, wherein said diode D1 is an anti-reflection diode.
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| CN201910110881.5A CN109617385B (en) | 2019-02-12 | 2019-02-12 | Capacitor precharge circuit |
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Denomination of invention: A capacitor pre charging circuit Granted publication date: 20231215 Pledgee: Guanggu Branch of Wuhan Rural Commercial Bank Co.,Ltd. Pledgor: WUHAN YONGLI RAYCO TECHNOLOGY Co.,Ltd. Registration number: Y2024980042895 |
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