JP3008592B2 - AC-DC converter - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC-DC converter capable of suppressing harmonics and improving an input power factor by making an input current waveform sinusoidal, and stabilizing an output voltage.

[0002]

2. Description of the Related Art In recent years, a switching power supply represented by A
C-DC converters have come into widespread use in home electric appliances as well as OA information equipment. However, since most of the configurations are of the capacitor input type, the input current has a peak-like waveform with a small conduction angle, resulting in a drop in line voltage and an increase in distortion rate due to feedback of harmonic components to the line side. Is a direct cause of

A conventional AC-DC converter for suppressing harmonics and improving the input power factor will be described below.

FIG. 5 is a circuit diagram of a conventional AC-DC converter to which a step-up converter is applied. In FIG. 5, 1a and 1b are input terminals for receiving an input AC voltage. Reference numeral 2 denotes a full-wave rectifier as a first rectifier, which performs full-wave rectification on the received input AC voltage. 3 is a capacitor, 41 is a choke coil, 42 is a switching transistor, 43 is a current detection resistor, 44 is a diode as a second rectifier, 45 is a capacitor, 46a, 4
6b is an output terminal. Reference numeral 30 denotes a control drive circuit, which includes a reference voltage source 31, an error amplifier 32, a multiplier 33, a comparator 34, an oscillator 35, and a drive circuit 36.

The conventional AC-DC constructed as described above
The operation of the converter will be described below.

First, an input AC voltage is rectified and smoothed by a first rectifier 2 and a capacitor 3 and converted into a DC voltage V1. The capacitance of the capacitor 3 may or may not be small. Therefore, the DC voltage V1 has a full-wave rectified waveform sufficiently including the pulsating component of the input AC voltage. The DC voltage V1 is converted into a high-frequency AC voltage by the choke coil 41 and the switching transistor 42, rectified and smoothed by the second rectifier 44 and the capacitor 45, and output as the output voltage V0. Output voltage V0
Is compared and amplified by the error amplifier 32 with the reference voltage source 31. The output of the error amplifier 32 and the DC voltage V1 are
The result is multiplied by 3 and becomes a full-wave rectified waveform voltage V2 having a predetermined magnitude and proportional to the waveform of the DC voltage V1. The current flowing through the switching transistor 42 is a current detecting resistor 43
The detected voltage V3 is compared with the full-wave rectified waveform voltage V2 by the comparator 34. The output of the comparator 34 and the output voltage V4 of the oscillator 35 together with the driving circuit 36
The drive circuit 36 outputs a drive output voltage V5 for driving the switching transistor 42 at a predetermined on / off ratio.

FIG. 6 shows this state. 6A shows the output voltage V4 of the oscillator 35, FIG. 6B shows the full-wave rectified waveform voltage V2 and the detection voltage V3 of the current detection resistor 43,
(C) is the drive output voltage V5 of the drive circuit 36, and (d) is the choke current I2 flowing through the choke coil 41. By placing the peak value of the current flowing through the switching transistor 42 on a predetermined full-wave rectified waveform in this manner,
The choke current I2 can be made as shown in FIG. 6D, and the input AC current I1 can be a sine wave with suppressed harmonic components.
The input power factor can be at or near unity.

[0008]

However, in the above-mentioned conventional configuration, the output voltage must be set to be higher than the peak value of the input voltage because the boost converter system is used. When the voltage is lower than the voltage or when insulation between input and output is required, it is necessary to add a DC-DC converter for voltage conversion at a subsequent stage.
In that case, the input specification of the DC-DC converter is required to have a high voltage input, so that the cost is increased by increasing the number of parts, the efficiency is reduced by connecting the converters in series, the size is increased, As a result, a problem such as a decrease in reliability due to an increase in the number of inevitable problems arises. Further, the step-up converter does not have a means for limiting the rush current at the time of start-up or restart at the time of the circuit configuration, so that it has to be provided separately.

The present invention solves the above-mentioned conventional problems. One AC-DC converter alone makes an input current waveform sinusoidal without connecting a DC-DC converter in the subsequent stage, and an output voltage of an output voltage. To provide an AC-DC converter for power factor improvement capable of providing flexibility in selection, providing insulation between input and output as required, and eliminating the need for insulation transmission means when feeding back output voltage. It is an object.

[0010]

In order to achieve this object, an AC-DC converter according to the present invention comprises a first rectifier for rectifying an AC input, and a first rectifier for converting the input voltage rectified by the first rectifier into a first rectifier. And a series circuit of a choke coil, a first switching means, and a second rectifier connected in antiparallel to the first switching means and a current detecting means are connected in parallel to the first capacitor. And a parallel connection of a series circuit of a second capacitor, a second switching means, and a third rectifier connected in antiparallel to the second switching means in parallel with the choke coil. An output is taken out from both ends of the capacitor 2 and the current waveform obtained from the current detection means is converted into a sine wave in synchronism with the input voltage in order to make the current waveform of the AC input into a sine wave shape. Wherein the rising or falling of the forward voltage of the first detection winding provided in the choke coil by comparing the rectified voltage waveform as a trigger first
A first control drive circuit having a function of determining the on / off ratio of the switching means, and a second detection winding provided in the choke coil for stabilizing an output voltage taken out from both ends of the second capacitor. A configuration comprising a second control drive circuit having a function of adjusting the on / off ratio of the second switching means with a rise or fall of a flyback voltage as a trigger, or a first rectifier for rectifying an AC input, A first capacitor is connected in parallel to the input voltage rectified by the first rectifier, and a choke coil and first switching means are connected to the first capacitor in anti-parallel to the first switching means. A series circuit of a second rectifier and current detection means is connected in parallel, and a first separate winding is provided on the choke coil to form an output winding. A second capacitor to the output winding second
And a third circuit connected in reverse parallel to the second switching means and a third rectifier connected in parallel to take out an output from both ends of the second capacitor. By comparing a current waveform obtained from the current detecting means with a sine-wave full-wave rectified voltage waveform synchronized with the input voltage to make the waveform a sine wave, the first detection winding provided in the choke coil is forwarded. A first control drive circuit having a function of determining an on / off ratio of the first switching means by using a rise or fall of a voltage as a trigger; and a first control drive circuit for stabilizing an output voltage taken out from both ends of the second capacitor. The second switch is triggered by a rise or fall of a flyback voltage of a second separate winding provided in one choke coil. It has a structure comprising a second control drive circuit having a function of adjusting the on-off ratio of grayed means.

[0011]

With this configuration, the input AC current waveform is controlled by the first switching means so as to be similar and in-phase with the input AC voltage, so that the input AC current waveform is a sinusoidal waveform having little harmonic distortion. The input power factor is almost 1, and the output voltage can be freely set without connecting a DC-DC converter in the subsequent stage, and the insulation can be applied as needed.
The problems associated with the connection of the C converter can be solved all at once, and the output voltage signal can be directly controlled on the secondary side without having to insulate the output voltage signal and transmit it to the primary side. Can be omitted, and the inrush current can be automatically limited by the first switching means.

[0012]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. FIG. 1 is a circuit diagram of an AC-DC converter according to an embodiment of the present invention. In FIG. 1, 1a and 1b are input terminals for receiving an input AC voltage. A first rectifier 2 performs full-wave rectification of the received input AC voltage. 3 is a first capacitor, 4 is a choke coil, 5 is a switching transistor as first switching means, 5a is a second switching transistor connected in anti-parallel to the first switching transistor 5.
Rectifier. Reference numeral 6 denotes a current detection resistor as current detection means, 7 denotes a second capacitor, 8 denotes a switching transistor as second switching means, and 8a denotes a third anti-parallel connected to the second switching transistor 8. Rectifiers 9a and 9b are output terminals. Reference numeral 10 denotes a first control drive circuit, which includes an adjuster 11 that arbitrarily changes the peak of the input voltage, a first comparator 12, a first detection winding 13, and a first drive circuit 14. Become. Reference numeral 20 denotes a second control drive circuit, which includes a reference voltage source 21, a second comparator 22, a second detection winding 23, and a second drive circuit 24.
It is composed of

The operation of the AC-DC converter configured as described above will be described below. First, the input AC voltage is rectified and smoothed by the first rectifier 2 and the first capacitor 3, and is converted into the DC voltage V1. Here, the DC voltage waveform V1 is a full-wave rectified waveform sufficiently including the pulsation of the input voltage because the capacitance of the first capacitor 3 is sufficiently small. The DC voltage V1 is applied to the choke coil 4 when the first switching transistor 5 is turned on. The flyback voltage generated in the choke coil 4 when the switching transistor 5 is turned off is supplied to the third rectifier 8a and the second capacitor. 7 after being rectified and smoothed.

The current flowing through the switching transistor 5 while the switching transistor 5 is on is detected by the current detecting resistor 6, and the detected voltage V3 is compared by the first comparator 12 with the full-wave rectified waveform voltage V2. You. The output of the first comparator 12 is input to a first drive circuit 14 and receives a detection signal from a first detection winding 13 while simultaneously receiving the first switching transistor 5.
Is turned on, and the first switching transistor 5 is turned on until the peak value of the current flowing through the switching transistor 5 reaches a predetermined value. As described above, the peak value of the current flowing through the first switching transistor 5 is set to the first value.
6B, the input AC current waveform is converted into a sine wave with a suppressed harmonic component, and the input power factor is controlled. Can be set to 1 or close to it as in the conventional example.

However, in the case of this embodiment, the wave height of the full-wave rectified waveform voltage V2 is a constant value corresponding to the energy to be supplied to the expected maximum load, and the amplitude of the full-wave rectified waveform voltage V2 is not changed by the load. It differs from the conventional example in the point. This means that a constant maximum energy corresponding to the full-wave rectified waveform voltage V2 is always transmitted to the secondary side. In practice, the load constantly fluctuates, and the energy required by the load is not always constant, so that surplus energy is generated except in the maximum load state. The energy required by the load is output after being rectified and smoothed by the third rectifier 8a and the second capacitor 7 connected in anti-parallel to the second switching transistor 8.

The output voltage is compared with a reference voltage source 21 by a second comparator 22. With the generation of surplus energy, the output of the second comparator 22 is detected by a second detection winding 23. The operation is provided to the second drive circuit 24 together with the signal, and the operation is continued to be turned on until the processing of the surplus energy is completed. That is, by turning on the second switching transistor 8 after supplying the energy to the load, the secondary current continues to flow to the minus side, and the choke coil 4 is reversely excited to store the surplus energy in the choke coil 4. When this process ends, the second switching transistor 8 is turned off.

Thereafter, when the first switching transistor 5 driven by the detection signal of the detection winding 13 is turned on, all the surplus energy stored in the choke coil 4 is regenerated to the primary side, and this regenerated energy is The voltage is stored in the first capacitor 3 through the second rectifier 5a connected in anti-parallel to the first switching transistor 5. That is, by regenerating excess energy from the secondary energy to the primary energy from the maximum energy supplied from the primary energy to the secondary energy, it is controlled to supply the energy required by the load.

As described above, according to this embodiment, the control of only the switching accompanying the sinusoidal transformation of the input current waveform is performed on the primary side by regenerating the excess energy.
On the secondary side, only control of output voltage stabilization and control of surplus energy processing can be performed independently of each other. Therefore, two control systems, i.e., sinusoidal input current waveform and output voltage stabilization, are used in the circuit configuration. Since the output voltage can be completely separated between the secondary and the secondary, and when the output voltage is stabilized, it is not necessary to insulate and transmit the output voltage to the primary side.

(Embodiment 2) Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. FIG. 2 is a circuit diagram of an AC-DC converter according to a second embodiment of the present invention. In FIG. 2, input terminals 1a and 1b receive an input AC voltage. A first rectifier 2 performs full-wave rectification of the received input AC voltage. 3 is a first capacitor, 4 is a choke coil, 5 is a switching transistor as first switching means, 5a
Is a second rectifier connected in anti-parallel to the first switching transistor 5, and 6 is a current detecting resistor as current detecting means. 4a is another winding applied to the choke coil 4, 7 is a second capacitor, 8 is a switching transistor as second switching means, and 8a is a third transistor connected in anti-parallel to the second switching transistor 8. Rectifiers 9a and 9b are output terminals. 1
Reference numeral 0 denotes a first control drive circuit, which includes an adjuster 11 for arbitrarily changing the peak of the input voltage, a first comparator 12, and a first control drive circuit.
, And a first drive circuit 14. 2
Reference numeral 0 denotes a second control drive circuit, which includes a reference voltage source 21, a second comparator 22, a second detection winding 23, and a second drive circuit 24.

The operation of the AC-DC converter configured as described above will be described below. First, the input AC voltage is rectified and smoothed by the first rectifier 2 and the first capacitor 3, and is converted into the DC voltage V1. Here, the DC voltage waveform V1 is a full-wave rectified waveform sufficiently including the pulsation of the input voltage because the capacitance of the first capacitor 3 is sufficiently small. This DC voltage V1 is applied to the choke coil 4 when the first switching transistor 5 is turned on. A flyback voltage generated in another winding 4a applied to the choke coil 4 when the first switching transistor 5 is turned off is rectified and smoothed by the third rectifier 8a and the second capacitor 7, and then output.

The first switching transistor 5
Is turned on, the current flowing through the first switching transistor 5 is detected by the current detecting resistor 6, and the detected voltage V3 is compared by the first comparator 12 with the full-wave rectified waveform voltage V2. The output of the first comparator 12 is input to a first drive circuit 14, which receives the detection signal from the first detection winding 13 and simultaneously turns on the first switching transistor 5 to flow through the switching transistor 5. The first switching transistor 5 is turned on until the peak value of the current reaches a predetermined value. As described above, the peak value of the current flowing through the first switching transistor 5 is placed on a predetermined full-wave rectified waveform to be compared in the first comparator 12, and is controlled as shown in FIG. As in the conventional example, the input AC current waveform can be a sine wave with suppressed harmonic components, and the input power factor can be set to 1 or close to it.

However, in the case of this embodiment, the peak of the full-wave rectified waveform voltage V2 is a constant value corresponding to the energy to be supplied to the expected maximum load, and the amplitude of the full-wave rectified waveform voltage V2 is not changed by the load. It differs from the conventional example in the point. This means that a constant maximum energy corresponding to the full-wave rectified waveform voltage V2 is always transmitted to the secondary side. In practice, the load constantly fluctuates, and the energy required by the load is not always constant, so that surplus energy is generated except in the maximum load state. The energy required by the load is output after being rectified and smoothed by the third rectifier 8a and the second capacitor 7 connected in anti-parallel to the second switching transistor 8.

The output voltage is compared with a reference voltage source 21 by a second comparator 22. With the generation of surplus energy, the output of the second comparator 22 is detected by a second detection winding 23. The operation is provided to the second drive circuit 24 together with the signal, and the operation is continued to be turned on until the processing of the surplus energy is completed. That is, by turning on the second switching transistor 8 after supplying the energy to the load, the secondary current continues to flow to the minus side, and the choke coil 4 is reversely excited to store the surplus energy in the choke coil 4. When this process ends, the second switching transistor 8 is turned off.

Thereafter, when the first switching transistor 5 driven by the detection signal of the detection winding 13 is turned on, the surplus energy stored in the choke coil 4 is all regenerated to the primary side, and this regenerated energy is The voltage is stored in the first capacitor 3 through the second rectifier 5a connected in anti-parallel to the first switching transistor 5. That is, by regenerating excess energy from the secondary energy to the primary energy from the maximum energy supplied from the primary energy to the secondary energy, it is controlled to supply the energy required by the load.

As described above, according to this embodiment, the control of only the switching accompanying the sinusoidal conversion of the input current waveform is performed on the primary side by regenerating excess energy.
On the secondary side, only control of output voltage stabilization and control of surplus energy processing can be performed independently of each other. Therefore, two control systems, i.e., sinusoidal input current waveform and output voltage stabilization, are used in the circuit configuration. It can be completely separated between the secondary and the secondary, can provide insulation between input and output, and it is not necessary to transmit the output voltage to the primary side when stabilizing the output voltage. It has the feature that the means can be made unnecessary.

FIG. 3 is a waveform diagram illustrating the operation of the first and second embodiments. FIG. 3 shows the detection voltage V13 and the full-wave rectified waveform voltage V12 detected by the current detection resistor 6, and in this case, the operation is started with the rise of the forward voltage of the first detection winding 13 as a trigger. Become. FIG. 4 shows operation waveforms of the currents i ₁ and i ₂ flowing through the primary and secondary switching transistors. At the time of the rated load shown in FIG. 4A, the waveform matches that of the conventional ringing choke converter. When the rated load shown in FIG. 4B is less than the rated value, the difference between the supply and the regenerative is given to the load as net energy.

In the first and second embodiments, when a switching transistor has a parasitic diode inside such as a MOS-FET, the second rectifier 5a and the third rectifier 5a are connected in anti-parallel. 8a can be omitted.
Further, although a resistor is used as the current detecting means, it goes without saying that a current detecting means such as a current transformer may be used.

As shown in the above embodiment, while the first switching transistor 5 is on, the input voltage rectified by the first rectifier 2 is applied to the choke coil 4 to excite it, and the first switching transistor 5 is excited. While the switching transistor 5 is off, the degaussing current of the choke coil 4 is rectified and smoothed by the third rectifier 8a and the second capacitor 7, and then output to the load.

The input voltage rectified by the first rectifier 2 is represented by E
i, the output voltage is Eo, the inductance of the choke coil 4 is L, and the ON and OFF periods of the first switching transistor 5 are Ton and Toff, respectively. For the second embodiment, which is an insulation type, the primary side and the
It is assumed that the inductance of another winding 4a provided in the choke coil 4 is equal to L, with the winding ratio on the secondary side being 1: 1.

The amount of increase in the exciting current flowing through the choke coil 4 while the first switching transistor 5 is on is Ei · Ton / L The demagnetizing current flowing through the choke coil 4 while the first switching transistor 5 is off. Since the current flowing through the Eo · Toff / L choke coil 4 is continuous, the amount of increase and decrease of these currents are equal, and the following equation is established.

Ei · Ton = Eo · Toff That is, Eo = (Ton / Toff) · Ei.

Therefore, in the configuration as in the present invention, the output voltage can be freely set while making the input current a sine wave.

[0033]

As described above, according to the present invention, a first rectifier for rectifying an AC input, and a first capacitor connected in parallel to the input voltage rectified by the first rectifier, are provided. A capacitor is connected in parallel with a choke coil, a first switching means, and a series circuit of a second rectifier and a current detection means connected in anti-parallel to the first switching means, and a second circuit is connected in parallel with the choke coil. A series circuit of a capacitor, a second switching means, and a third rectifier connected in anti-parallel to the second switching means is connected in parallel, an output is taken out from both ends of the second capacitor, and the AC In order to make the input current waveform a sine wave shape, the current waveform obtained from the current detection means is compared with the sine wave full-wave rectified voltage waveform synchronized with the input voltage to the choke coil. A first control drive circuit having a function of determining an on / off ratio of the first switching means by using a rise or a fall of a forward voltage of the first detection winding, and both ends of the second capacitor. A second function having a function of adjusting the on / off ratio of the second switching means by using a rise or fall of a flyback voltage of a second detection winding provided in the choke coil as a trigger to stabilize an output voltage taken out. Or two control driving circuits, or
A first rectifier for rectifying an AC input, a first capacitor connected in parallel to the input voltage rectified by the first rectifier, a choke coil and first switching means connected to the first capacitor; A serial circuit of a second rectifier and a current detecting means connected in anti-parallel to the first switching means is connected in parallel, and a first separate winding is provided on the choke coil to form an output winding. , A series circuit of a second capacitor, a second switching means, and a third rectifier connected in anti-parallel to the second switching means is connected in parallel, and an output is taken out from both ends of the second capacitor. In order to make the AC input current waveform sinusoidal, the current waveform obtained from the current detection means is compared with a sine-wave full-wave rectified voltage waveform synchronized with the input voltage. A first control drive circuit having a function of determining an on / off ratio of the first switching means by using a rise or fall of a forward voltage of a first detection winding provided in a work coil, and the second capacitor In order to stabilize the output voltage taken out from both ends of the second choke coil, the rise or fall of the flyback voltage of the second separate winding provided in the first choke coil is used as a trigger to adjust the on / off ratio of the second switching means. With the configuration including the second control drive circuit having the function, the primary side converts the input current waveform into a sine wave and supplies constant energy, while the secondary side stabilizes the output voltage and regenerates excess energy. The processing is performed independently, and the input current factor is almost unity and the input current waveform with less harmonic distortion. For the pressure conversion DC-
Since the output voltage can be freely set without connecting a DC converter, all the problems associated with the connection of the DC-DC converter can be solved, and the input and output can be insulated as necessary, and the feedback of the output voltage can be performed. The present invention realizes an excellent AC-DC converter for power factor improvement, which eliminates the need for an insulated transmission means required for the power supply and further eliminates the need for an inrush current limiting circuit because the inrush current is automatically limited by the first switching means. You can do it.

[Brief description of the drawings]

FIG. 1 is a circuit configuration diagram of an AC-DC converter according to a first embodiment of the present invention.

FIG. 2 is a circuit configuration diagram of an AC-DC converter according to a second embodiment of the present invention.

FIG. 3 is a waveform chart for explaining the operation of the first and second embodiments.

FIG. 4 is a diagram showing current waveforms in primary and secondary in the first and second embodiments.

FIG. 5 is a circuit configuration diagram of a conventional AC-DC converter.

FIG. 6 is a waveform diagram for explaining the operation of the AC-DC converter in the conventional example and the first and second embodiments of the present invention.

[Explanation of symbols]

 1a, 1b Input terminal 2 First rectifier 3 First capacitor 4 Choke coil 4a Separate winding 5 First switching transistor 5a Second rectifier 6 Detector resistor 7 Second capacitor 8 Second switching transistor 8a Third Rectifier 9a, 9b Output terminal 10 First control drive circuit 20 Second control drive circuit 30 Control drive circuit 41 Choke coil 42 Switching transistor 43 Detection resistor 44 Rectifier 45 Capacitor 46a, 46b Output terminal

──────────────────────────────────────────────────続 き Continued on the front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02M 3/155 H02M 3/28

Claims (2)

(57) [Claims] 1. A first rectifier for rectifying an AC input, a first capacitor connected in parallel to an input voltage rectified by the first rectifier, and a choke coil and a first capacitor connected to the first capacitor. A switching circuit and a series circuit of a current detector and a second rectifier connected in anti-parallel to the first switching means are connected in parallel, and a second capacitor and a second switching means are connected in parallel with the choke coil. And a third switching means connected in anti-parallel to the second switching means.
A series circuit with the rectifier is connected in parallel, an output is taken out from both ends of the second capacitor, and a current waveform obtained from the current detecting means is converted into the input voltage in order to make the AC input current waveform a sine wave. And a sine-wave full-wave rectified voltage waveform synchronized with the first detection means, and the rising or falling of the forward voltage of the first detection winding provided in the choke coil is used as a trigger to determine the on / off ratio of the first switching means. A first control driving circuit having a function, and a rising or falling of a flyback voltage of a second detection winding provided in the choke coil for stabilizing an output voltage taken out from both ends of the second capacitor. An AC-DC converter comprising a second control drive circuit having a function of adjusting the on / off ratio of the second switching means as a trigger. Converter. 2. A first rectifier for rectifying an AC input, a first capacitor connected in parallel to the input voltage rectified by the first rectifier, and a choke coil and a first capacitor connected to the first capacitor. A serial circuit of a second rectifier and a current detecting means connected in anti-parallel to the switching means and the first switching means is connected in parallel, and a first separate winding is provided on the choke coil to serve as an output winding. A second capacitor, a second switching means, and the second
A serial circuit with a third rectifier connected in anti-parallel to the switching means is connected in parallel, and an output is taken out from both ends of the second capacitor, so that the current waveform of the AC input is sinusoidal. The rising or falling of the forward voltage of the first detection winding provided in the choke coil is determined by comparing the current waveform obtained from the current detection means with a sine wave full-wave rectified voltage waveform synchronized with the input voltage. A first control drive circuit having a function of determining an on / off ratio of the first switching means as a trigger; and a first control drive circuit provided in the first choke coil for stabilizing an output voltage taken out from both ends of the second capacitor. The rising or falling of the flyback voltage of the second separate winding is used as a trigger to adjust the on / off ratio of the second switching means. AC-DC converter comprising a second control drive circuit having a function.