WO2021059402A1

WO2021059402A1 - Boost converter

Info

Publication number: WO2021059402A1
Application number: PCT/JP2019/037640
Authority: WO
Inventors: 洋平久保田; 正樹金森; 慶一加藤; 志剛李
Original assignee: 東芝キヤリア株式会社
Priority date: 2019-09-25
Filing date: 2019-09-25
Publication date: 2021-04-01

Abstract

Provided is a boost converter capable of driving switches appropriately without increasing power supply capacity even when the number of driving circuits is great and, consequently, without increasing cost. The boost converter rectifies, boosts, and outputs the voltage of a single-phase AC power supply by switching based on pulse width modulation corresponding to a voltage command value. A second driving circuit (22) for driving a second switch (S2) is operated by the DC voltage of a first DC power supply (E1), and third and fourth driving circuits (23, 24) for driving third and fourth switches (S3, S4) are operated by the DC voltage of a second DC power supply (E2). When the third switch (S3) is turned on, a capacitor (12) of a bootstrap circuit (10) is charged with the DC voltage of the second DC power supply (E2), and a first driving circuit (21) for driving a first switch (S1) is operated with the voltage of the capacitor of the bootstrap circuit.

Description

Boost converter

An embodiment of the present invention relates to a boost converter mounted on a power supply device such as an air conditioner or a heat source machine including a refrigeration cycle, for example.

Boost converters installed in power supplies such as air conditioners and heat source machines that include refrigeration cycles include reactors, switches, capacitors, etc., and rectify and boost the voltage of the AC power supply by performing boost chopper switching. Output. This boost converter is also referred to as a high power factor converter, a PFC (Power Factor Correction) converter, or a totem pole type PFC converter.

Japanese Unexamined Patent Publication No. 2016-330378

In the case of a boost converter that outputs multiple levels of DC voltage, the number of switches used increases, and the number of drive circuits that drive each switch also increases accordingly. If the number of drive circuits is large, the power supply capacity must be increased, which leads to an increase in cost.

An object of the embodiment of the present invention is to provide a boost converter capable of appropriately driving each switch without increasing the power supply capacity and thus increasing the cost even if the number of drive circuits is large. ..

The boost converter according to claim 1 rectifies and boosts the voltage of a single-phase AC power supply by switching based on pulse width modulation according to a voltage command value, and outputs the positive side charging circuit, the negative side charging circuit, and the first. It is equipped with a fourth drive circuit and a bootstrap circuit. The positive side charging circuit leads from one end of the single-phase AC power supply to one end of the series circuit of the first and second capacitors via the first switch during the positive level period of the voltage command value, and the first and first ones thereof. The first energizing path leading from the other end of the series circuit of the two capacitors to the other end of the single-phase AC power supply via the second diode, and the reactor, the third switch, and the fourth switch from one end of the single-phase AC power supply. The first and third switches repeatedly turn on and off in a complementary manner while the second switch is continuously turned off, including a second energizing path leading to the interconnection point of the first and second capacitors. Charges the first and second capacitors. The negative charging circuit leads from the other end of the single-phase AC power supply to one end of the series circuit of the first and second capacitors via the first diode during the negative level period of the voltage command value, and the first And the third energization path leading from the other end of the series circuit of the second capacitor to one end of the single-phase AC power supply via the second switch, and the first from the other end of the single-phase AC power supply via the first diode. A fourth energizing path that leads to one end of the series circuit of the first and second capacitors, and from the interconnection point of the first and second capacitors to one end of the single-phase AC power supply via the fourth switch and the third switch. The first and second capacitors are charged by repeating complementary on and off of the second and fourth switches in a state where the first switch is continuously turned off. The second drive circuit operates by the voltage of the first DC power supply to drive the second switch. The third and fourth drive circuits operate by the voltage of the second DC power supply to drive the third and fourth switches. The bootstrap circuit includes a capacitor that is charged by the voltage of the second DC power source when the third switch is on. The first drive circuit operates and operates by the charging voltage of the capacitor of the bootstrap circuit to drive the first switch. One end of the series circuit of the first and second capacitors is a positive level output terminal, and the other end of the series circuit of the first and second capacitors is a negative level output terminal.

The figure which shows the structure of the booster circuit in one Embodiment. The figure which shows the structure of the drive control circuit in one Embodiment. The figure which shows the generation of the PWM signal in the controller of one Embodiment. The figure which shows the capacitor voltage of the boost strap circuit in one Embodiment.

Hereinafter, a boost converter according to an embodiment of the present invention will be described with reference to the drawings. This boost converter is composed of the boost circuit of FIG. 1 and the drive control circuit of FIG. 2, and is mounted on a power supply device such as an air conditioner or a heat source machine including a refrigeration cycle, for example.

The booster circuit rectifies and boosts the voltage (called AC power supply voltage) Vc of the single-phase AC power supply 1 by switching based on pulse width modulation according to the voltage command value Vs described later, and outputs the voltage command value Vs. It includes a positive charging circuit that allows current to flow along the path indicated by the solid line arrow during the positive level period, and a negative charging circuit that allows current to flow along the path indicated by the broken line arrow during the negative level period of the voltage command value Vs. Of the two power supply lines connected to one end and the other end of the single-phase AC power supply 1, the reactor 3 is inserted into the power supply line connected to one end of the single-phase AC power supply 1. FIG. 3 shows the relationship between the waveform of the AC power supply voltage Vc, the voltage command value Vs, and the on / off operation of each switch element S1 to S4 in the booster circuit.

The positive side charging circuit is in the positive half-wave section Ta (= T / 2) of the AC power supply voltage Vc in the substantially central predetermined period Ta2 where the voltage command value Vs becomes the positive level, and the negative of the AC power supply voltage Vc. In the side half-wave section Tb (= T / 2), during the predetermined periods Tb1 and Tb3 on both sides where the voltage command value Vs becomes a positive level, the reactor 3 and the switch element (first switch) S1 are connected from one end of the single-phase AC power supply 1. Is passed through one end of the series circuit of the capacitors (first and second capacitors) C1 and C2 in order, and from the other end of the series circuit of the capacitors C1 and C2 via the diode (second diode) D2, a single-phase AC power supply. The current-carrying circuit (first current-carrying path) L1 leading to the other end of 1 and one end of the single-phase AC power supply 1 are passed through the reactor 2, the switch element (third switch) S3, and the switch element (fourth switch) S4 in this order. The switch elements S1 and S3 complement each other in different phases in a state where the switch element S2 is continuously turned off and the switch element S4 is continuously turned on, including the current-carrying circuit (second current-carrying path) L2 leading to the interconnection point of the capacitors C1 and C2. The capacitors C1 and C2 are charged by repeatedly turning on and off.

The negative charging circuit is in the negative half-wave section Tb of the AC power supply voltage Vc in the substantially central predetermined period Tb2 where the voltage command value Vs becomes a negative level, and in the positive half-wave section Ta of the AC power supply voltage Vc. Of these, during the predetermined periods Ta1 and Ta3 on both sides where the voltage command value Vs becomes a negative level, the other end of the single-phase AC power supply 1 is passed through the diode (first diode) D1 to one end of the series circuit of the capacitors C1 and C2. A current-carrying path (third current-carrying path) L3 that leads from the other end of the series circuit of the diodes C1 and C2 to one end of the single-phase AC power supply 1 via the switch element (second switch) S2 and the reactor 2 in order, and a single phase. The other end of the AC power supply 1 is passed through the diode D1 to one end of the series circuit of the capacitors C1 and C2, and the single-phase AC is sequentially passed through the switch element S4, the switch S3 and the reactor 2 from the interconnection point of the capacitors C1 and C2. Including the current-carrying circuit (fourth current-carrying path) L4 leading to one end of the power supply 1, the switch elements S2 and S4 are complementarily turned on and off in different phases while the switch element S1 is continuously turned off and the switch S3 is continuously turned on. By repeating the above, the diodes C1 and C2 are charged.

One end of the series circuit of the capacitors C1 and C2 is the positive level output terminal P, the other end of the series circuit of the capacitors C1 and C2 is the negative level output terminal N, and the interconnection point of the capacitors C1 and C2 is the zero level output terminal M. It becomes. A predetermined level of DC voltage Vdc is generated between the output terminals P and N, and a DC voltage "+ Vdc / 2" which is 1/2 of the DC voltage Vdc is generated between the output terminals P and M, and the output terminals N and M are generated. A DC voltage "-Vdc / 2", which is 1/2 of the DC voltage Vdc, is generated between them. These three levels of DC voltage are the outputs of the boost converter. The reactor 3 may be inserted into the power supply line connected to the other end of the single-phase AC power supply 1, and further, the reactor 3 may be inserted in both of the power supply lines connected to both ends of the single-phase AC power supply 1. May be good. That is, the reactor 3 may be provided in at least one of the power supply lines connected to both ends of the single-phase AC power supply 1.

The switch elements S1 to S4 include parasitic diodes D11 to D14 connected in antiparallel to each element body, have bidirectional current flowing in both directions between the drain and the source when on, and power loss when on. Is a semiconductor switch element, for example, a MOSFET, which is smaller than the power loss due to the forward voltage drop of the parasitic diodes D11 to D14. Here, the switch elements S1 and S2 are the same as each other in a state where the switch element S1 is in the forward direction toward the output terminal P and the switch element S2 is in the forward direction from the output terminal N toward the reactor 2 and the switch element S1. They are connected in series in the direction. The switch elements S3 and S4 are serialized in opposite directions with each other in a state where the switch element S3 is in the forward direction toward the interconnection point A of the switch elements S1 and S2 and the switch element S4 is in the forward direction toward the output terminal M. It is connected. In the positive half-wave section Ta of the AC power supply voltage Vc, even if the switch element S4 is turned off, current flows through the parasitic diode D14 of the switch element S4. Therefore, if the loss of the parasitic diode D14 can be tolerated, the AC power supply voltage Vc The switch element S4 may be maintained in the off state in the positive half-wave section Ta of the above. Similarly, in the negative half-wave section Tb of the AC power supply voltage Vc, even if the switch element S3 is turned off, a current flows through the parasitic diode D13 of the switch element S3. The switch element S3 may be maintained in the off state in the negative half-wave section Tb of the power supply voltage Vc.

The drive control circuits of these switch elements S1 to S4 are configured as shown in FIG.

One end and the other end of the capacitor 3 are connected to the positive and negative terminals of the DC power supply E1, and the positive and negative input ends of the drive circuit 22 are connected to one end and the other end of the capacitor 3. .. Then, the gate of the switch element S2 is connected to the positive output end of the drive circuit 22 via the resistor 32, and the source (output terminal N) of the switch element S2 is connected to the negative output end of the drive circuit 22. .. The negative output end of the drive circuit 22 is conductive with the negative input end of the drive circuit 22, and is in a conductive state with the negative terminal of the DC power supply E1 through the negative input end. That is, the DC power supply E1 outputs a DC voltage based on the negative level of the output terminal N.

The drive circuit 22 operates by the DC voltage of the DC power supply E1 (voltage of the capacitor 3), and a pulse whose voltage changes to a high level “H” and a low level “L” according to the PWM signal X2 supplied from the controller 40. Drive signal Y2 is generated and output. The voltage of the drive signal Y2 is applied between the gate and source of the switch element S2 via the resistor 32.

The positive and negative input ends of the drive circuit 23 are connected to the positive and negative terminals of the DC power supply E2. Then, the gate of the switch element S3 is connected to the positive output end of the drive circuit 23 via the resistor 33, and the source of the switch element S3 and the source of the switch element S4 are interconnected to the negative output end of the drive circuit 23. Point C is connected. The negative output end of the drive circuit 23 is conductive with the negative input end of the drive circuit 23, and is in a conductive state with the negative terminal of the DC power supply E2 through the negative input end. That is, the DC power supply E2 outputs a DC voltage with reference to the zero level of the interconnection point C.

The drive circuit 23 operates by the DC voltage of the DC power supply E2, and transmits a pulse-shaped drive signal Y3 whose voltage changes to a high level “H” and a low level “L” according to the PWM signal X3 supplied from the controller 40. Generate and output. The voltage of the drive signal Y3 is applied between the gate and source of the switch element S3 via the resistor 33.

The positive and negative input ends of the drive circuit 24 are connected to the positive and negative terminals of the same DC power supply E2. Then, the gate of the switch element S4 is connected to the positive output end of the drive circuit 24 via the resistor 34, and the source of the switch element S4 and the source of the switch element S3 are interconnected to the negative output end of the drive circuit 24. Point C is connected. The negative output end of the drive circuit 24 is in a conductive state with the negative terminal of the DC power supply E2 through the negative input end of the drive circuit 24.

The drive circuit 24 generates and outputs a pulse-shaped drive signal Y4 whose voltage changes to a high level “H” and a low level “L” according to the PWM signal X4 supplied from the controller 40. The voltage of the drive signal Y4 is applied between the gate and source of the switch element S4 via the resistor 34.

Further, one end of the capacitor 12 of the bootstrap circuit 10 is connected to the positive terminal of the same DC power supply E2 via the diode 11 of the bootstrap circuit 10, and the other end of the capacitor 12 is the negative input end of the drive circuit 21. , The negative output end of the drive circuit 21 that conducts with the negative input end, between the drain and source of the switch element S3, the interconnection point C, the negative output end of the drive circuit 23, and the negative output end. It is connected to the negative terminal of the DC power supply E2 via the negative input end of the drive circuit 23 in order. That is, when the switch element S3 is on, the voltage of the DC power supply E2 is applied to the capacitor 12 of the bootstrap circuit 10, and the capacitor 12 is charged.

The positive input end and the negative input end of the drive circuit 21 are connected to both ends of the capacitor 12 of the bootstrap circuit 10, and the gate of the switch element S1 is connected to the positive output end of the drive circuit 21 via a resistor 31. It is connected, and the source of the switch element S1 is connected to the negative output end of the drive circuit 21. The drive circuit 21 operates by the voltage Vbs of the capacitor 12 of the bootstrap circuit 10, and has a pulse shape in which the voltage changes to a high level “H” and a low level “L” according to the PWM signal X1 supplied from the controller 40. The drive signal Y1 is generated and output. The voltage of the drive signal Y1 is applied between the gate and source of the switch element S1 via the resistor 31.

The controller 40 is connected to these drive circuits 21 to 24. The controller 40 causes the waveform of the voltage Fab generated between the interconnection point A of the switch elements S1 and S2 and the interconnection point B of the diodes D1 and D2 to reach a sinusoidal wave, and the output voltage Vdc between the output terminals P and N. The voltage command value Vs for reaching the target value Vt is calculated by calculation, and as shown in FIG. 3, the carrier signal voltage K1 on the positive side of the triangular wave shape is pulse-width modulated (voltage comparison) according to the voltage command value Vs. ) To generate pulse-shaped PWM signals X1 and X3 for the switch elements S1 and S3, and pulse-width-modulate the triangular wave-shaped negative carrier signal voltage K2 according to the voltage command value Vs. Pulse-like PWM signals X2 and X4 for S2 and S4 are generated.

The voltage command value Vs is set to the positive side level and the negative side level so that the waveform of the voltage Vab generated between the interconnection point A of the switch elements S1 and S2 and the interconnection point B of the diodes D1 and D2 reaches a sine wave. As it fluctuates, the value changes according to the difference between the output voltage Vdc between the output terminals P and N and the target value Vt with respect to the output voltage Vdc. Here, since the voltage Vb at the interconnection point B is the rectified waveform of the diodes D1 and D2, in the positive half-wave section Ta of the AC power supply voltage Vc, the voltage Vb becomes the voltage of the output terminal N on the negative side. In the negative half-wave section Tb of the AC power supply voltage Vc, the voltage Vb is the voltage of the output terminal P on the positive side. That is, the voltage Vb at the interconnection point B is a square wave showing a negative constant value in the positive half-wave section Ta of the AC power supply voltage Vc and a positive constant value in the negative half-wave section Tb of the AC power supply voltage Vc. .. Based on the voltage Vb of the square wave, the voltage Va of the interconnection point A required to bring the waveform of the voltage Vab between the interconnection points A and B to a sine wave of a predetermined level is the voltage command shown in FIG. It becomes a waveform of the value Vs. Then, in order to match the output voltage Vdc between the output terminals P and N with the target value Vt, the peak value (peak value) Vsp of the voltage command value Vs that becomes a positive level in the positive half-wave section Ta of the AC power supply voltage Vc is , The lower the output voltage Vdc value (measured value) between the output terminals P and N is lower than the target value Vt, the higher the value, and the higher the output voltage Vdc value (measured value) between the output terminals P and N is higher than the target value Vt. It gets lower. On the contrary, the peak value Vsp'of the voltage command value Vs, which becomes a negative level in the negative half-wave section Tb of the AC power supply voltage Vc, becomes negative as the value of the output voltage Vdc between the output terminals P and N is lower than the target value Vt. It becomes higher on the side, and the higher the value of the output voltage Vdc between the output terminals P and N is higher than the target value Vt, the lower it becomes on the negative side.

The calculation method of the voltage command value Vs is the same as the calculation method of the voltage command value in the conventional totem pole type PFC converter.

The PWM signal X1 which is the basis for generating the drive signal Y1 for the switch element S1 repeats high level "H" and low level "L" in the positive level period of the voltage command value Vs, and repeats the negative level period of the voltage command value Vs. Maintain a low level "L" at. The PWM signal X3, which is the basis for generating the drive signal Y3 for the switch element S3, repeats high level "H" and low level "L" in the positive level period of the voltage command value Vs, and repeats the negative level period of the voltage command value Vs. Maintain a low level "L" at. In the PWM signals X1 and X3, the phase of the high level "H" and the phase of the low level "L" are opposite to each other.

The PWM signal X2, which is the basis for generating the drive signal Y2 for the switch element S2, maintains a low level “L” during the positive level period of the voltage command value Vsb and a high level “H” during the negative level period of the voltage command value Vs. And the low level "L" are repeated. The PWM signal X4, which is the basis for generating the drive signal Y4 for the switch element S4, maintains a high level “H” during the positive level period of the voltage command value Vs, and maintains a high level “H” during the negative level period of the voltage command value Vs. And the low level "L" are repeated. In the PWM signals X2 and X4, the phase of the high level "H" and the phase of the low level "L" are opposite to each other.

According to the drive control circuit having such a configuration, the drive circuit 22 for driving the switch S2 operates by the DC voltage of the DC power supply E1, and the

drive circuits

23 and 24 for driving the switches S3 and S4 are the DC voltage of the DC power supply E2. Works with. Then, when the switch S3 is on, the capacitor 12 of the bootstrap circuit 10 is charged by the DC voltage of the DC power supply E2, and the drive circuit 21 for driving the switch S1 operates from the voltage Vbs of the capacitor 12.

FIG. 4 shows the relationship between the AC power supply voltage Vc, the input current I from the AC power supply 1 to the booster circuit, and the voltage Vbs of the capacitor 12.

If a configuration is adopted in which the capacitor 12 of the bootstrap circuit 10 is charged by the DC voltage of the DC power supply E1 and the drive circuit 21 is operated by the voltage Vbs of the capacitor 12, the voltage Vbs of the capacitor 12 is shown in FIG. As shown by the broken line, the voltage drops, and a sufficient level of voltage required for the operation of the drive circuit 21 cannot be secured. As a result, the switch S1 cannot be driven properly.

If the configuration is such that the capacitor 12 of the bootstrap circuit 10 is charged by the DC voltage of the DC power supply E2 when the switch S3 is on as in the present embodiment, the voltage Vbs of the capacitor 12 is shown by a solid line in FIG. It stabilizes without deterioration. As a result, a sufficient level of voltage required for the operation of the drive circuit 21 can be secured, and the switch S1 can be appropriately driven.

Since the operating voltage of the

drive circuits

23 and 24 is obtained from one DC power supply E2 and the DC power supply E2 is also used for charging the bootstrap circuit 10, even if the number of drive circuits is as large as four, The switches S1 to S4 can be appropriately driven without increasing the power supply capacity and thus without increasing the cost.

Other than that, the above embodiment is presented as an example, and is not intended to limit the scope of the invention. This novel embodiment can be implemented in various other forms, and various omissions, rewrites, and changes can be made without departing from the gist of the invention. In these embodiments, the scope of the invention is included in the gist, and is also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 ... AC power supply, 2 ... Reactor, D1, D2 ... Diode, S1 to S4 ... Switch elements (1st to 4th switches), C1, C2 ... Capacitors (1st and 2nd capacitors), P ... Positive level output Terminals, N ... Negative level output terminals, M ... Zero level output terminals, L1 to L4 ... Energized paths (1st to 4th energized paths), E1, E2 ... DC power supplies (1st and 2nd DC power supplies), 10 ... bootstrap circuit, 11 ... diode, 12 ... capacitor, 21-24 ... drive circuit (1st to 4th drive circuits), 40 ... controller

Claims

A boost converter that rectifies and boosts the voltage of a single-phase AC power supply by switching based on pulse width modulation according to the voltage command value and outputs it.
During the positive level period of the voltage command value, one end of the single-phase AC power supply is passed to one end of the series circuit of the first and second capacitors via the first switch, and the series circuit of the first and second capacitors is used. The first energization path leading from the end to the other end of the single-phase AC power supply via the second diode, and the first and first circuits from one end of the single-phase AC power supply via the reactor, the third switch, and the fourth switch. The first and second switches include a second energizing path leading to the interconnection point of the two capacitors, and the first and third switches repeatedly turn on and off in a complementary manner while the second switch is continuously turned off. A positive charging circuit that charges the capacitor,
During the negative level period of the voltage command value, the other end of the single-phase AC power supply leads to one end of the series circuit of the first and second capacitors via the first diode, and the series circuit of the first and second capacitors thereof. A third energizing path leading from the other end of the single-phase AC power supply to one end of the single-phase AC power supply via a second switch, and a series of the first and second capacitors from the other end of the single-phase AC power supply via the first diode. The first energization path that leads to one end of the circuit and leads from the interconnection point of the first and second capacitors to one end of the single-phase AC power supply via the fourth switch and the third switch. A negative charging circuit that charges the first and second capacitors by repeating complementary on and off of the second and fourth switches while the switches are continuously turned off.
A second drive circuit that operates by the voltage of the first DC power supply and drives the second switch,
The third and fourth drive circuits that operate by the voltage of the second DC power supply and drive the third and fourth switches, and
A bootstrap circuit that includes a capacitor that is charged by the voltage of the second DC power supply when the third switch is on.
A first drive circuit that operates by the charging voltage of the capacitor of the bootstrap circuit and drives the first switch.
With
One end of the series circuit of the first and second capacitors is a positive level output terminal, and the other end of the series circuit of the first and second capacitors is a negative level output terminal.
A boost converter that features that.
The voltage command value is on the positive side and the negative side so that the waveform of the voltage generated between the interconnection point of the first and second switches and the interconnection point of the first and second diodes reaches a sine wave. As it swings to the level, the value changes according to the difference between the output voltage of the boost converter and the target value with respect to the output voltage.
The boost converter according to claim 1.
The first to fourth switches are MOSFETs including parasitic diodes, respectively.
The third and fourth switches are connected in series in opposite directions to each other.
The boost converter according to claim 1.
In the positive charging circuit, the first and second capacitors are turned on and off repeatedly in a state where the second switch is continuously turned off and the fourth switch is continuously turned on. Charge and
In the negative charging circuit, the first and second capacitors are formed by repeating complementary on and off of the second and fourth switches in a state where the first switch is continuously turned off and the third switch is continuously turned on. To charge,
The boost converter according to claim 3.
A reactor inserted in at least one of both power supply lines connected to one end and the other end of the single-phase AC power supply.
The boost converter according to any one of claims 1 to 4, wherein the boost converter is characterized in that.