JP2013192383A - Dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a DC-DC converter in which a step-up ratio or a step-down ratio can be varied and an output voltage can be controlled variably to an arbitrary voltage with respect to an input voltage.SOLUTION: The DC-DC converter is configured to supply power in any one direction or both directions between smoothing capacitors Cdc1, Cdc2 and comprises a switch circuit connected to both ends of Cdc2, a flying capacitor Cfc connected to a connecting point of switches S1, S2 and a connecting point of switches S3, S4 in the switch circuit, a current sensor 3 which detects a current flowing to a reactor Lchop connected to a connecting point of S2 and S3 and one end of Cdc1, voltage detection circuits 2, 6 for detecting voltages in both ends of any one of or both Cdc1, Cdc2, and a control circuit 8 which generates a first voltage command value corresponding to a direction in which power is supplied between Cdc1 and Cdc2 and a first current command value on the basis of a first voltage detection value from the voltage detection circuits, generates a duty command value on the basis of the first current command value and a current detection value from the current sensor and turns on/off S1-S4 in accordance with the duty command value.

Description

  The present invention relates to a switched capacitor type DC-DC converter.

  As a high-efficiency DC-DC converter, a switched capacitor type DC-DC converter has attracted attention.

  FIG. 7 shows a circuit configuration diagram of a conventional DC-DC converter using a switched capacitor system. When the DC-DC converter is started, the control unit 102 turns on the switches S11 and S13, turns off the switches S12 and S14, sets the charging period, and charges the boost capacitor C1.

  Next, the switches S11 and S13 are turned off, and the switches S12 and S14 are turned on for a boosting period. The voltage is boosted by the boosting capacitor C1 and the output capacitor C3 is charged. Thereafter, the charging period and the boosting period are alternately switched, and the charging voltage of the output capacitor C3, that is, the output voltage Vo is stabilized at the steady-state output voltage Vo.

JP 2002-369501 A

  However, in the conventional DC-DC converter using the switched capacitor system shown in FIG. 7, the boost ratio is fixed at 2 (integer), so that the output voltage can be variably controlled with respect to the input voltage. Can not.

  An object of the present invention is to provide a DC-DC converter capable of varying a step-up ratio and a step-down ratio and variably controlling an output voltage to an arbitrary voltage with respect to an input voltage.

  In order to solve the above problems, the present invention provides a first smoothing capacitor connected between a first input / output terminal and a second input / output terminal, and a third input / output terminal and a fourth input / output terminal. A DC-DC converter that supplies power in one or both directions to a second smoothing capacitor connected to the first smoothing capacitor, connected between one end and the other end of the second smoothing capacitor, A switch circuit connected in series in the order of a switch, a second switch, a third switch, and a fourth switch; a connection point between the first switch and the second switch; and the third switch and the fourth switch. A flying capacitor connected between a connection point, a connection point between the second switch and the third switch, and a reactor connected between one end of the first smoothing capacitor; and a current flowing through the reactor A current detecting circuit for detecting; a first voltage detecting circuit for detecting a voltage across one or both of the first smoothing capacitor and the second smoothing capacitor; the first smoothing capacitor and the second smoothing capacitor; A first current command value is generated based on the first voltage command value corresponding to the direction in which power is supplied between the first voltage detection value and the first voltage detection value from the first voltage detection circuit, and the first current command value and the current And a control circuit for generating a duty command value based on a current detection value from the detection circuit and turning on / off each switch of the switch circuit based on the duty command value.

  According to the present invention, since the reactor is used, the step-up ratio and the step-down ratio can be varied, and the output voltage can be variably controlled to an arbitrary voltage with respect to the input voltage.

It is a circuit block diagram of the DC-DC converter of 1st Embodiment. It is a circuit block diagram of the control circuit of the DC-DC converter of 1st Embodiment. It is a figure which shows each mode at the time of the pressure | voltage rise operation of the DC-DC converter of 1st Embodiment. It is a figure which shows the ON / OFF state of each switch of the DC-DC converter of 1st Embodiment. It is a circuit block diagram of the control circuit of the DC-DC converter of 2nd Embodiment. It is a figure which shows the relationship between the output electric power of the DC-DC converter of 2nd Embodiment, and the both-ends voltage of a flying capacitor. It is a circuit block diagram of the conventional DC-DC converter using a switched capacitor system.

  Next, a DC-DC converter according to an embodiment of the present invention will be described in detail with reference to the drawings.

(First embodiment)
FIG. 1 is a circuit configuration diagram of the DC-DC converter according to the first embodiment. The DC-DC converter according to the first embodiment of the present invention is a switched-capacitor type DC-DC converter, which is applied to charge / discharge of energy storage elements 1 and 7 such as storage batteries and supplies power in both directions (step-up operation, step-down operation). Smoothing capacitor Cdc1 and smoothing capacitor Cdc2 are provided on each of the low voltage side and the high voltage side.

  In FIG. 1, the energy storage element 1 has a lower pressure than the energy storage element 7, and is connected to a terminal A (first input / output terminal) and a terminal B (second input / output terminal) on the low voltage side. The energy storage element 7 has a higher voltage than the energy storage element 1 and is connected to a terminal C (third input / output terminal) and a terminal D (fourth input / output terminal) on the high voltage side.

  A smoothing capacitor Cdc1 (first smoothing capacitor) is connected to the terminals A and B, and a smoothing capacitor Cdc2 (second smoothing capacitor) is connected to the terminals C and D.

  Note that the DC-DC converter of the first embodiment may be used only for the step-up operation or only for the step-down operation. When used only for the step-up operation, a load device may be used instead of the energy storage element 7, and when used only for the step-down operation, a load device may be used instead of the energy storage element 1.

  The switch circuit 4 is connected to both ends of the smoothing capacitor Cdc2, and from one end of the smoothing capacitor Cdc2 to the other end, the switch S1 (first switch), the switch S2 (second switch), the switch S3 (third switch), The switches S4 (fourth switch) are connected in series in this order. In each of switches S1 to S4, an emitter of an insulated gate bipolar transistor (hereinafter referred to as an IGBT) and an anode of a diode are connected, an IGBT collector and a cathode of a diode are connected, and a gate signal is applied to the gate of the IGBT. It is designed to be entered.

  One end of the smoothing capacitor Cdc1 is connected to one end of a step-up chopper reactor Lchop (reactor) for continuous voltage variable control via the current sensor 3, and the other end of the chopper reactor Lchop is connected to the switch S2. One end (anode side of the diode) and one end of the switch S3 (the cathode side of the diode) are connected.

  One end of the switch S2 (diode cathode side) is connected to the other end of the switch S1 (diode anode side), and the other end of the switch S3 (diode anode side) is one end of the switch S4 (diode cathode side). Is connected. The other end of the switch S4 (the anode side of the diode) is connected to the other ends of the smoothing capacitor Cdc1 and the smoothing capacitor Cdc2. One end of the switch S1 (the cathode side of the diode) is connected to one end of the smoothing capacitor Cdc2.

  A flying capacitor Cfc is connected to a connection point between the switch S1 and the switch S2 and a connection point between the switch S3 and the switch S4. The voltage detection circuit 2 (first voltage detection circuit) detects the voltage Vdc1 across the smoothing capacitor Cdc1 and outputs it to the control circuit 8. The current sensor 3 (current detection circuit) detects the current flowing through the chopper reactor Lchop and outputs it to the control circuit 8. The voltage detection circuit 5 (second voltage detection circuit) detects the voltage Vfc across the flying capacitor Cfc and outputs it to the control circuit 8. The voltage detection circuit 6 (first voltage detection circuit) detects the voltage Vdc2 across the smoothing capacitor Cdc2 and outputs it to the control circuit 8.

  The control circuit 8 generates a chopper current command value ichopref (first current command value) corresponding to the direction (step-up operation, step-down operation) in which power is supplied between the smoothing capacitor Cdc1 and the smoothing capacitor Cdc2. That is, when power is supplied from the smoothing capacitor Cdc1 to the smoothing capacitor Cdc2 (step-up operation), the voltage command value Vdcref (first voltage command value) and the voltage Vdc2 across the smoothing capacitor Cdc2 detected by the voltage detection circuit 6 are detected. Based on (first voltage detection value), a chopper current command value ichopref is generated. When the power is supplied from the smoothing capacitor Cdc2 to the smoothing capacitor Cdc1 (step-down operation), the voltage command value Vdcref (first voltage command value) and the voltage Vdc1 across the smoothing capacitor Cdc1 detected by the voltage detection circuit 2 are used. Based on (first voltage detection value), a chopper current command value ichopref is generated. The voltage command value Vdcref may be the same or different between the step-up operation and the step-down operation.

  The control circuit 8 generates a duty command value based on the chopper current command value ichopref and the current ichop (current detection value) flowing through the chopper reactor Lchop detected by the current sensor 3, and switches S1 to S1 according to the duty command value. The gate signal of S4 is generated, the gate signal is output to the switches S1 to S4, the switch S1 and the switch S4 are alternately turned on / off, and the switch S2 and the switch S3 are alternately turned on / off, thereby boosting the voltage. Operation and step-down operation are performed.

  FIG. 2 is a circuit configuration diagram of a control circuit of the DC-DC converter according to the first embodiment. In FIG. 2, the control circuit 8 includes adders 11, 13 and 16, proportional integration circuits (hereinafter referred to as PI circuit) 12 and 14, limiter circuit 15, comparators 17 and 18, and inverters 19 and 20. .

  During the step-down operation, the adder 11 calculates the deviation between the predetermined voltage command value Vdcref indicating the target value of the voltage Vdc1 across the smoothing capacitor Cdc1 and the voltage Vdc1 across the smoothing capacitor Cdc1 detected by the voltage detection circuit 2 from the PI circuit 12. During the step-up operation, a deviation between a predetermined voltage command value Vdcref indicating the target value of the voltage Vdc2 across the smoothing capacitor Cdc2 and the voltage Vdc2 across the smoothing capacitor Cdc2 detected by the voltage detection circuit 6 is input to the PI circuit 12. Output. The PI circuit 12 performs a PI operation on the deviation from the adder 11 and outputs a chopper current command value ichopref to the adder 13. The adder 13 outputs a deviation between the chopper current command value ichopref from the PI circuit 12 and the current ichop detected by the current sensor 3 to the PI circuit 14.

  The PI circuit 14 performs a PI operation on the deviation from the adder 13. The limiter circuit 15 performs limit processing on the output from the PI circuit 14 and outputs the result as a duty command value.

  The comparator 17 generates a first pulse signal that is H level when the output from the limiter circuit 15 is larger than the carrier signal composed of a triangular wave signal and L level when the output from the limiter circuit 15 is smaller than the carrier signal. The first pulse signal is applied to the gate of the switch S4. The inverter 19 inverts the first pulse signal from the comparator 17 and applies the inverted pulse signal to the gate of the switch S1.

  The adder 16 subtracts the output from the limiter circuit 15 from “1”. The comparator 18 generates a second pulse signal that is H level when the carrier signal is larger than the output from the adder 16 and L level when the carrier signal is smaller than the output from the adder 16. A pulse signal is applied to the gate of the switch S2. The inverter 20 inverts the second pulse signal from the comparator 18 and applies the inverted pulse signal to the gate of the switch S3.

  Next, the operation of the DC-DC converter according to the first embodiment configured as described above will be described in detail with reference to FIGS. 3 and 4. FIG. 3 is a diagram illustrating each mode during the step-up operation of the DC-DC converter according to the first embodiment. FIG. 3A shows an operation circuit diagram of mode 1 during the boosting operation, and FIG. 3B shows an operation circuit diagram of mode 2 during the boosting operation.

  FIG. 4 is a diagram illustrating an on / off state of each switch of the DC-DC converter according to the first embodiment. In FIG. 4, when the voltage ratio between the low voltage side and the high voltage side is 1: 2, only the operation in mode 1 and mode 2 is performed. When the voltage ratio between the low voltage side and the high voltage side is an arbitrary voltage ratio, the mode 3 and mode 4 operations are performed. When the duty command value is 0 to 0.5, the switching operation is performed in mode 1, mode 2, and mode 3. When the duty command value is 0.5 to 1, the switching operation is performed in mode 1, mode 2, and mode 4. .

  Here, the step-up operation when turning on / off at a duty of 50% will be described. In mode 1 during the boosting operation, as shown in FIG. 4, the switch S2 and the switch S4 are turned on, and the switch S1 and the switch S3 are turned off. For this reason, as shown in FIG. 3 (a), current flows through the path of Cdc1-> Lchop-> S2-> Cfc-> S4, energy is accumulated in the chopper reactor Lchop, and the voltage Vdc1 across the smoothing capacitor Cdc1 becomes the flying capacitor. Cfc is charged.

  In mode 2 during the step-up operation, as shown in FIG. 4, the switch S2 and the switch S4 are turned off, and the switch S1 and the switch S3 are turned on. For this reason, as shown in FIG. 3B, a current flows through a path of Cdc1-> Lchop-> S3-> Cfc-> S1-> Cdc2. As a result, the both-ends voltage Vfc of the flying capacitor Cfc is added to the both-ends voltage Vdc1 of the smoothing capacitor Cdc1, and the both-ends voltage Vdc2 of the smoothing capacitor Cdc2 becomes 2Vdc1, and this voltage is supplied to the energy storage element 7.

  Next, the step-down operation when turning on / off at a duty of 50% will be described. In mode 2 during the step-down operation, half the voltage Vdc2 across the smoothing capacitor Cdc2 is charged in the flying capacitor Cfc. In mode 1 during the step-down operation, the voltage Vfc across the flying capacitor Cfc becomes the voltage Vdc1 across the smoothing capacitor Cdc1, and this voltage is supplied to the energy storage element 1.

  In the first embodiment, the chopper reactor Lchop is provided, the current sensor 3 detects the current flowing through the chopper reactor Lchop, the voltage detection circuit 2 detects the voltage Vdc1 across the smoothing capacitor Cdc1, and the voltage detection circuit 6 The voltage Vdc2 across the smoothing capacitor Cdc2 is detected, and the control circuit 8 generates gate signals for the switches S1 to S4 based on these detected values, and outputs the gate signals to the switches S1 to S4.

  That is, by using the chopper reactor Lchop to perform current (ichop) feedback control, the step-up ratio and step-down ratio can be varied, and the output voltage can be variably controlled with respect to the input voltage.

(Second Embodiment)
In the DC-DC converter of the first embodiment, the voltage Vfc across the flying capacitor Cfc is normally clamped at ½ times the voltage Vdc2 across the smoothing capacitor Cdc2. However, if there is a difference between the time when the flying capacitor Cfc is charged and the time when the flying capacitor Cfc is discharged due to variations in the load, variations in each switch constituting the switch circuit 4, delay of a drive circuit (not shown), etc., the flying capacitor The voltage Vfc at both ends of Cfc fluctuates and is not balanced to ½ times the voltage Vdc2 at both ends of the smoothing capacitor Cdc2. In such a case, since the voltage applied to each switch constituting the switch circuit 4 varies, there is a concern that the breakdown voltage of each switch may be exceeded and destroyed.

  Therefore, the DC-DC converter according to the second embodiment solves the above-described problem, includes a voltage detection circuit 5 (second voltage detection circuit) that detects the voltage Vfc across the flying capacitor Cfc, and includes a control circuit 8. Generates a duty correction value based on the voltage command value Vfcref (second voltage command value) and the voltage Vfc (second voltage detection value) across the flying capacitor Cfc detected by the voltage detection circuit 5, and generates a duty correction value. The balance control (balance control) for eliminating the voltage imbalance of the voltage Vfc across the flying capacitor Cfc is performed based on the corrected duty command value obtained by adding to the duty command value.

  FIG. 5 is a circuit configuration diagram of a control circuit of the DC-DC converter according to the second embodiment. The control circuit of the second embodiment shown in FIG. 5 further includes an adder 21, a PI circuit 22, a limiter circuit 23, and adders 24 and 25 with respect to the control circuit of the first embodiment shown in FIG. It is provided.

  The other configuration shown in FIG. 5 is the same as the configuration shown in FIG. 2, and therefore, the same parts are denoted by the same reference numerals and description thereof is omitted.

  The adder 21 outputs a deviation between a predetermined voltage command value Vfcref indicating a target value of the voltage Vdc2 across the smoothing capacitor Cdc2 and the voltage Vfc across the flying capacitor Cfc detected by the voltage detection circuit 5 to the PI circuit 22.

  The PI circuit 22 performs a PI operation on the deviation from the adder 21. The limiter circuit 23 performs a limit process on the output from the PI circuit 22 and outputs it as a duty correction value.

  The adder 24 outputs a corrected duty command value obtained by adding the duty command value from the limiter circuit 15 and the duty correction value from the limiter circuit 23 to the non-inverting input terminal (+) of the comparator 17. The adder 25 adds the duty correction value from the limiter circuit 23 and the output from the adder 16 and outputs the sum to the inverting input terminal (−) of the comparator 18.

  The comparator 17 generates a first pulse signal that is H level when the output from the adder 24 is larger than the carrier signal composed of a triangular wave signal and L level when the output from the adder 24 is smaller than the carrier signal. The first pulse signal is applied to the gate of the switch S4. The inverter 19 inverts the first pulse signal from the comparator 17 and applies the inverted pulse signal to the gate of the switch S1.

  The comparator 18 generates a second pulse signal having an H level when the carrier signal is larger than the output from the adder 25 and an L level when the carrier signal is smaller than the output from the adder 25. Is applied to the gate of switch S2. The inverter 20 inverts the second pulse signal from the comparator 18 and applies the inverted pulse signal to the gate of the switch S3.

  Next, the operation of the DC-DC converter according to the second embodiment configured as described above will be described.

  First, the voltage Vfc across the flying capacitor Cfc detected by the voltage detection circuit 5 is input to the adder 21. The adder 21 outputs a deviation between the voltage command value Vfcref and the detected voltage Vfc across the flying capacitor Cfc. The deviation from the adder 21 is PI-calculated by the PI circuit 22 and output as a duty correction value to the adders 24 and 25 via the limiter circuit 23.

  The adder 24 adds the output from the limiter circuit 15 and the output from the limiter circuit 23. The output from the limiter circuit 23 and the output from the adder 16 are added by the adder 25.

  In other words, a duty correction value is generated based on the voltage command value Vfcref and the voltage Vfc across the flying capacitor Cfc detected by the voltage detection circuit 5, and a corrected duty command obtained by adding the duty correction value to the duty command value. Depending on the value, the switches S1 and S2 or the switches S3 and S4 constituting the switch circuit 4 are simultaneously turned on, and a period in which the flying capacitor Cfc is not charged / discharged is generated. The voltage Vfc across the flying capacitor Cfc is controlled using this period during which charging / discharging is not performed. When the deviation between the voltage command value Vfcref and the voltage Vfc across the flying capacitor Cfc detected by the voltage detection circuit 5 becomes zero, the voltage imbalance between the voltages Vfc across the flying capacitor Cfc can be eliminated.

  FIG. 6 is a diagram illustrating the relationship between the output power of the DC-DC converter of the second embodiment and the voltage Vfc across the flying capacitor Cfc. When balanced control (■ in FIG. 6) in which the duty command value is corrected by the duty correction amount is performed, the voltage Vfc across the flying capacitor Cfc is controlled to a constant voltage regardless of the magnitude of the output power. I understand that.

  However, in unbalanced control in which the duty command value is not corrected by the duty correction amount (♦ in FIG. 6), the voltage Vfc across the flying capacitor Cfc varies as the load becomes heavier. Therefore, the usefulness of the present invention can be confirmed.

  In this way, in the DC-DC converter that boosts or lowers the DC voltage, it is possible to establish a control that balances the voltage Vfc across the flying capacitor Cfc with ½ times the voltage Vdc2 across the smoothing capacitor Cdc2. Thereby, it is possible to prevent the breakdown voltage of each switch constituting the switch circuit 4 from being exceeded and destroyed. In addition, a low breakdown voltage switch can be used, and the cost can be reduced.

DESCRIPTION OF SYMBOLS 1,7 Energy storage element 2,5,6 Voltage detection circuit 3 Current sensor 4 Switch circuit 8 Control circuit 11, 13, 16, 21, 24, 25 Adder
12, 14, 22 PI circuit 15, 23 Limiter circuit 17, 18 Comparator 19, 20 Inverter S1-S4 Switch Cdc1, Cdc2 Smoothing capacitor Cfc Flying capacitor Lchop Chopper reactor

Claims (3)

Between the first smoothing capacitor connected between the first input / output terminal and the second input / output terminal and the second smoothing capacitor connected between the third input / output terminal and the fourth input / output terminal. A DC-DC converter that supplies power in one or both directions,
A switch circuit connected between one end and the other end of the second smoothing capacitor and connected in series in the order of a first switch, a second switch, a third switch, and a fourth switch;
A flying capacitor connected between a connection point of the first switch and the second switch and a connection point of the third switch and the fourth switch;
A reactor connected between a connection point of the second switch and the third switch and one end of the first smoothing capacitor;
A current detection circuit for detecting a current flowing through the reactor;
A first voltage detection circuit for detecting a voltage across one or both of the first smoothing capacitor and the second smoothing capacitor;
Based on the first voltage command value corresponding to the direction in which power is supplied between the first smoothing capacitor and the second smoothing capacitor and the first voltage detection value from the first voltage detection circuit, the first current command value is determined. Generating a duty command value based on the first current command value and the current detection value from the current detection circuit, and turning on and off each switch of the switch circuit by the duty command value;
The DC-DC converter characterized by having.   The first voltage detection value from the first voltage detection circuit is a detection value obtained by detecting the voltage across the second smoothing capacitor when power is supplied from the first smoothing capacitor to the second smoothing capacitor. 2. The DC− according to claim 1, wherein when the power is in a direction to supply power from the second smoothing capacitor to the first smoothing capacitor, the detected value is obtained by detecting a voltage across the first smoothing capacitor. DC converter. A second voltage detection circuit for detecting a voltage across the flying capacitor;
The control circuit generates a duty correction value based on the second voltage command value and the second voltage detection value from the second voltage detection circuit, and adds the duty correction value to the duty command value. 3. The DC-DC converter according to claim 1, wherein each switch of the switch circuit is turned on / off by a duty command value to control a voltage across the flying capacitor to a constant voltage. 4.

Images