JP2008301623A - Balancing circuit with discharge function - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a balancing circuit with a discharge function that reduces circuit scale and manufacturing costs. <P>SOLUTION: The balancing circuit 2 with a discharge function is configured to provide discharging circuits 2a, 2b for discharging each of capacitors C1, C2 connected in series between DC power supply wires VH, VL. When potential V4 between the capacitors C1, C2 is below a prescribed value (potential V3 between resistors R7, R8 connected in series between the DC power supply wires VH, VL), the balancing circuit 2 discharges the capacitor C1 by the discharging circuit 2a. When the potential V4 exceeds the prescribed value, the balancing circuit discharges the capacitor C2 by the discharging circuit 2b. When AC supply from an AC power supply AC is stopped, a power-supply stop detection circuit 3 discharges only the capacitor C2 by using only the discharging circuit 2b. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a balance circuit with a discharge function.

  Patent Documents 1 and 2 disclose two capacitors connected in series between two DC power supply lines. And the technique of balancing the both-ends voltage applied to each of these two capacitors is disclosed.

  More specifically, a pair of a resistor and a transistor connected in series with each other is provided in two capacitors, and the transistor is made conductive based on the magnitude relationship between the potential between the two capacitors and the reference potential. Yes. Due to the conduction of the transistor, one of the capacitors is discharged, and the balance of the voltage across each capacitor is maintained.

  Patent Document 3 discloses a single capacitor connected between two DC power supply lines and a discharge circuit that discharges the electric charge stored in the capacitor when power supply to the DC power supply line is interrupted. Has been. The discharge circuit includes a resistor and a transistor connected in series to the capacitor, and discharges the capacitor by conduction of the transistor.

Japanese Patent Laid-Open No. 10-295081 JP 63-314132 A JP 2002-262573 A

  However, in the techniques described in Patent Documents 1 and 2, when the power supply to the DC power supply line is interrupted, the voltages charged in the two capacitors cannot be discharged.

  Even if the discharge circuit described in Patent Document 3 is used to discharge the voltage charged in the two capacitors, the resistors and transistors for discharging the capacitor in Patent Document 3 are the same as those in Patent Documents 1 and 2. It is necessary to provide a pair corresponding to one capacitor, which increases circuit scale and manufacturing cost.

  Accordingly, an object of the present invention is to provide a balance circuit with a discharge function having a discharge function that suppresses an increase in circuit scale and manufacturing cost.

  A first aspect of the balance circuit with a discharge function according to the present invention includes a first DC power supply line (VH) to which a predetermined first potential (V1) is supplied, and a second lower than the predetermined first potential. A second DC power supply line (VL) to which a potential (V2) is supplied; a first capacitor (C1) connected between the first DC power supply line and the second DC power supply line; A second capacitor (C2) connected in series with the first capacitor on the second DC power supply line side, a first discharge circuit (2a) for discharging the first capacitor, and the second When the third electric potential (V4) between the second discharge circuit (2b) for discharging the capacitor and the first capacitor and the second capacitor is smaller than a predetermined value (V3), the first The first capacitor is discharged using the discharge circuit of FIG. A balance circuit (2) for discharging the second capacitor using the second discharge circuit when the value is larger than the value, and the supply of the predetermined first potential is stopped. A power stop detection circuit (3) that discharges only the first capacitor using only one discharge circuit, or discharges only the second capacitor using only the second discharge circuit.

  A second aspect of the balance circuit with a discharge function according to the present invention is the balance circuit with a discharge function according to the first aspect, wherein the balance circuit (2) includes the first potential (V1) and the second potential. A potential point (P) for supplying a fourth potential (V3) obtained by internally dividing the potential (V2) at a constant ratio as the predetermined value is provided.

  A third aspect of the balance circuit with a discharge function according to the present invention is a balance circuit with a discharge function according to the second aspect, and the second discharge circuit (2b) has one end connected to the first capacitor ( C1) and the second capacitor (C2), the control terminal is provided with a second transistor (Tr2) connected to the potential point (P), the balance circuit (2), A second rectifier element (D6) that is connected between the control terminal of the second transistor and the potential point, and that allows a current to flow only from the second transistor toward the potential point; The detection circuit (3) makes the second transistor conductive to discharge only the second capacitor.

  A balance circuit with a discharge function according to a fourth aspect of the present invention is a discharge function balance circuit according to a second aspect, wherein one end of the first discharge circuit (2a) is the first capacitor (C1). ) And the second capacitor (C2), and the control circuit includes a first transistor (Tr1) connected to the potential point (P), and the balance circuit (2) A first rectifier element (D5) that is connected between the control terminal of one transistor and the potential point and flows current only in a direction from the potential point toward the first transistor; In (3), the first transistor is turned on to discharge only the first capacitor.

  According to the first aspect of the balance circuit with a discharge function according to the present invention, when the supply of the first potential is stopped, the first capacitor is discharged using the first discharge circuit used by the balance circuit. The voltage across the first capacitor decreases due to the discharge, and the third potential decreases with the decrease in the voltage across the first capacitor. Thus, the balance circuit discharges the second capacitor using the second discharge circuit. To do. Therefore, it is not necessary to provide a dedicated discharge circuit for discharging the first capacitor and the second capacitor when the supply of the first potential is stopped, and the circuit scale and manufacturing cost can be reduced.

  The second aspect of the balance circuit with a discharge function according to the present invention contributes to the realization of the balance circuit with a discharge function according to the first aspect.

  According to the 3rd and 4th aspect of the balance circuit with a discharge function which concerns on this invention, it contributes to realization of the balance circuit with a discharge function which concerns on a 2nd aspect.

(Embodiment)
FIG. 1 shows a conceptual configuration diagram of an example of a balance circuit with a discharge function according to an embodiment of the present invention.

  The balance circuit with a discharge function includes DC power supply lines VH and VL, a rectifier circuit 1, capacitors C1 and C2, discharge circuits 2a and 2b, a balance circuit 2, and a power supply stop detection circuit 3.

  The rectifier circuit 1 rectifies alternating current input from the alternating current power supply AC into direct current, and supplies the potential V1 to the direct current power supply line VH and the potential V2 lower than the potential V1 to the direct current power supply line VL. In the present embodiment, the DC power supply line VL will be described as being connected to a constant reference potential (for example, ground potential) (that is, the potential V2 is substantially constant).

  More specifically, for example, the rectifier circuit 1 includes diodes D1 to D4. The cathodes of the diodes D1, D3 are connected to the DC power supply line VH, and the anodes of the diodes D2, D4 are connected to the DC power supply line VL. The anode of the diode D1 and the cathode of the diode D2 are commonly connected to one end of the AC power supply AC, and the anode of the diode D3 and the cathode of the diode D4 are commonly connected to the other end of the AC power supply AC.

  In the present embodiment, AC power supply AC is described as a single-phase AC power supply, but a three-phase AC power supply may be used.

  The capacitor C1 is connected between the DC power supply lines VH and VL. The capacitor C2 is connected in series with the capacitor C1 on the DC power supply line VL side. One set of capacitors C1 and C2 smoothes the direct current from the rectifier circuit 1.

  The discharge circuit 2a discharges the capacitor C1, and the discharge circuit 2b discharges the capacitor C2. More specifically, for example, the discharge circuit 2a includes a resistor R1 and an NPN transistor Tr1, and for example, the discharge circuit 2b includes a resistor R2 and a PNP transistor Tr2.

  The resistor R1 has one end connected to the DC power supply line VH and the other end connected to the collector electrode of the NPN transistor Tr1. The resistor R2 has one end connected to the DC power supply line VL and the other end connected to the collector electrode of the PNP transistor Tr2.

  The emitter electrodes of the NPN transistor Tr1 and the PNP transistor Tr2 are connected in common between the capacitors C1 and C2.

  The balance circuit 2 uses the discharge circuit 2a to discharge the capacitor C1 when the potential V4 between the capacitors C1 and C2 is smaller than a predetermined value, and the discharge circuit 2b when the potential V4 is larger than the predetermined value. Used to discharge the capacitor C2 and maintain the balance of the voltages across the capacitors C1 and C2. Note that maintaining the balance means maintaining the voltages across the capacitors C1 and C2 within a desired range.

  More specifically, for example, the balance circuit 2 includes resistors R7 and R8, a diode D6, and a potential point P. The resistor R7 has one end connected to the DC power supply line VH and the other end connected to the potential point P. The resistor R8 has one end connected to the DC power supply line VL and the other end connected to the potential point P. When the resistance values of the resistors R7 and R8 are r7 and r8, respectively, the potential point P supplies a potential V3 obtained by internally dividing the potential V1 and the potential V2 by a constant ratio r7: r8 as a predetermined value. When the alternating current from the alternating current power supply AC is supplied, the potentials V1 and V2 do not fluctuate. Therefore, the potential V3 obtained by internally dividing these at a constant ratio does not fluctuate.

  The diode D6 has an anode connected to the base electrode of the PNP transistor Tr2 and a cathode connected to the potential point P. The base electrode of the NPN transistor Tr1 is connected to the potential point P.

  The power stop detection circuit 3 discharges only the capacitor C2 using only the discharge circuit 2b by stopping the supply of the potential V1 to the DC power supply line VH. For example, as shown in FIG. 1, the power stop detection circuit 3 is connected to both ends of the AC power supply AC and between the base electrode of the PNP transistor Tr2 and the anode of the diode D6.

  Next, the operation of the balance circuit with the discharge function will be described roughly as a balance operation of the capacitors C1 and C2 during the normal operation and a discharge operation of the capacitors C1 and C2 when the power supply is stopped.

  First, the balancing operation for maintaining the balance of the voltages applied to both ends of each of the capacitors C1 and C2 will be described with reference to FIGS. FIG. 2 is a diagram showing the relationship between the potentials V1 to V4 when the voltage across the capacitor C1 rises. FIG. 3 is a diagram showing the relationship between the potentials V1 through V4 when the voltage across the capacitor C2 rises. is there.

  For example, when the voltage across the capacitor C1 rises due to product variations of the capacitors C1 and C2, the potential V4 between the capacitors C1 and C2 falls.

  Since the potential V3 does not fluctuate, the base-emitter voltage VBE1 (= V3-V4) of the NPN transistor Tr1 increases as the potential V4 decreases (see FIG. 2). The transistor Tr1 becomes conductive.

  Due to the conduction of the NPN transistor Tr1, a series circuit including the capacitor C1, the resistor R1, and the NPN transistor Tr1 is conducted, and the capacitor C1 is discharged. From the above, it can be understood that the balance circuit 2 discharges the capacitor C1 using the discharge circuit 2a when the potential V4 between the capacitors C1 and C2 falls below a predetermined value (potential V3).

  Along with the discharge, the voltage across the capacitor C1 decreases and the potential V4 increases. As the potential V4 increases, the voltage VBE1 of the NPN transistor Tr1 decreases. When the voltage VBE1 falls below a predetermined voltage, the NPN transistor Tr1 becomes non-conductive and the capacitor C1 stops discharging.

  Further, when the voltage across the capacitor C2 increases, the potential V4 increases. Since the potential V3 does not fluctuate, the base-emitter voltage VBE2 (= V4-V3) of the PNP transistor Tr2 increases with the increase of the potential V4 (see FIG. 3). The transistor Tr2 becomes conductive. The diode D6 permits a base current flowing from the base electrode of the PNP transistor Tr2 to the potential point P, and thus does not hinder the operation of the PNP transistor Tr2 in the balance operation.

  Due to the conduction of the PNP transistor Tr2, the series circuit including the capacitor C2, the resistor R2, and the PNP transistor Tr2 is turned on, and the capacitor C2 is discharged. From the above, it can be understood that the balance circuit 2 uses the discharge circuit 2b to discharge the capacitor C2 when the potential V4 between the capacitors C1 and C2 exceeds a predetermined value (potential V3).

  As a result of this discharge, the voltage across the capacitor C2 decreases and the potential V4 decreases. When the voltage VBE2 of the PNP transistor Tr2 decreases and falls below a predetermined voltage, the PNP transistor Tr2 becomes non-conductive.

  As described above, in normal operation, when the voltage across one of the capacitors C1 and C2 rises, the capacitor can be discharged to maintain the balance between the voltages across the two.

  When attention is paid to the potentials V3 and V4, it can be understood that the above-described balancing operation is discharging the capacitors C1 and C2 so that the potentials V3 and V4 are equal to each other.

  Next, the discharging operation of the capacitors C1 and C2 when the power is stopped will be described. When the supply of alternating current from the alternating current power supply AC is stopped, the power supply stop detection circuit 3 detects the stop and lowers the potential of the base electrode of the PNP transistor Tr2. This operation can be executed by, for example, conducting a switch inside the power stop detection circuit 3 to pull down the base electrode of the PNP transistor Tr2. When the supply of alternating current from the alternating current power supply AC is stopped, the supply of the potential V1 is also stopped.

  As the potential of the base electrode of the PNP transistor Tr2 decreases, the voltage VBE2 increases and the PNP transistor Tr2 becomes conductive. Due to the conduction, the capacitor C2 is discharged through the discharge circuit 2b.

  At this time, since the diode D6 supports the voltage between the potential point P and the base electrode of the PNP transistor Tr2, the potential V3 at the potential point P is directly related to the decrease in the potential of the base electrode of the PNP transistor Tr2 by the power stop detection circuit 3. Not affected. In other words, the diode D6 ensures the uniformity of the ratio at the potential V3 obtained by internally dividing the potentials V1 and V2 by a certain ratio.

  As the capacitor C2 is discharged, the potential V4 decreases and the potential V1 also decreases. On the other hand, since the capacitor C1 is not discharged, the voltage across the capacitor C1 does not change. Therefore, the amount of decrease per unit time of the potential V1 and the potential V4 is the same. In addition, the potential V3 also decreases as the potential V1 decreases. However, since the potential V3 is a value obtained by internally dividing the potentials V1 and V2 at a constant ratio, the amount of decrease in the potential V3 per time is the time per time of the potential V4. Is less than the amount of decrease.

  Therefore, the potential difference between the potentials V3 and V4, that is, the voltage VBE1 of the NPN transistor Tr1 rises, the NPN transistor Tr1 becomes conductive, and the capacitor C1 is discharged through the discharge circuit 2a.

  Thereafter, since the PNP transistor Tr2 is turned on by the power stop detection circuit 3, the capacitor C2 is discharged, and the balance circuit 2 discharges the capacitor C1 so that the potentials V3 and V4 are equal to each other.

  As described above, the balance of the voltages across the capacitors C1 and C2 can be maintained during normal operation, and the capacitors C1 and C2 can be discharged when the power is stopped.

  Since the discharge current from the capacitor C2 flows through the resistor R2 and the PNP transistor Tr2, and the discharge current from the capacitor C1 flows through the resistor R1 and the NPN transistor Tr1, they need to have sufficient power capacity. Such resistors R1, R2, NPN transistor Tr1, and PNP transistor Tr2 are generally expensive. Therefore, it is not necessary to increase the number of expensive resistors and transistors having a large power capacity as compared with the case where a pair of dedicated discharge circuits are separately provided corresponding to the capacitors C1 and C2, so that the manufacturing cost can be reduced. Further, it can be reduced from the viewpoint of circuit scale.

  If the diode D6 is not provided in the balance circuit with the discharge function and the base electrode of the PNP transistor Tr2 and the potential point P are short-circuited, the power supply stop detection circuit 3 causes a decrease in the potential of the base electrode. The potential V3 decreases. In this case, since the potential V3 is lower than the potential V4, the NPN transistor Tr1 cannot be made conductive and the capacitor C1 cannot be discharged.

  Next, a specific example of the power stop detection circuit 3 will be described. FIG. 4 shows a conceptual configuration diagram of a balance circuit with a discharge function including a specific example of the power supply stop detection circuit 3. The parts other than the power stop detection circuit 3 are the same as the balance circuit with a discharge function shown in FIG.

  The power stop detection circuit 3 includes resistors R5 to R6 and R9, a capacitor C3, and transistors Tr3 and Tr4.

  The resistors R9, R5, and R6 are connected in series in this order between one end of the AC power supply AC and the DC power supply line VL. The capacitor C3 has one end connected between the resistors R5 and R9 and the other end connected to the DC power supply line VL.

  The resistor R4 and the transistor Tr4 are connected in series between the DC power supply lines VH and VL in this order, and the base electrode of the transistor Tr4 is connected between the resistors R5 and R6.

  The resistor R3 and the transistor Tr3 are connected in series between the base electrode of the PNP transistor Tr2 and the DC power supply line VL in this order, and the base electrode of the transistor Tr3 is connected between the resistor R4 and the transistor Tr4.

  In the power supply stop detection circuit 3 having such a configuration, the capacitor C3 is connected in series with the AC power supply AC via the diode D4. Therefore, the capacitor C3 is charged in a half cycle of the AC power supply AC, and in the other half cycle, the resistor R5. , R6 is discharged. When the supply of alternating current from the alternating current power supply AC is stopped, the capacitor C3 maintains the discharge without being charged. Then, the potential between the resistors R5 and R6 decreases, the transistor Tr4 becomes non-conductive, the potential of the base electrode of the transistor Tr3 connected to the DC power supply line VL through the resistor R4 increases, and the transistor Tr3 Is conducted.

  Therefore, the base current of the PNP transistor Tr2 can flow through the resistor R3 and the transistor Tr3. As a result, the PNP transistor Tr2 becomes conductive, and the potential V4 can be lowered.

  As described above, the capacitor C2 is discharged by the discharge circuit 2b and the capacitor C1 is discharged by the discharge circuit 2a.

  FIG. 5 shows an example of a pair of voltage across the capacitors C1 and C2 (voltage between the DC power supply lines VH and VL) in the balance circuit with a discharging function shown in FIG. Referring to FIG. 5, the voltage was maintained at 270 V until the supply of AC from AC power supply AC was stopped in the vicinity of time 5 seconds, but after the supply of AC from AC power supply AC was stopped. The voltage is reduced to 30 V or less around the time of 90 seconds. As described above, according to the balance circuit with a discharge function according to the present embodiment, one discharge standard of 75 V or less can be achieved within 3 minutes from the power stop.

  The time required for the voltage across the pair of capacitors C1 and C2 to fall below a predetermined reference value (for example, 75V) after the supply of alternating current from the AC power source AC is stopped is defined as the reference time (for example, 3 minutes). It may be close. In this case, since the power capacity required for the resistors R1, R2, the NPN transistor Tr1, and the PNP transistor Tr2 can be reduced, the circuit scale and manufacturing cost can be reduced.

(Modification)
The conceptual block diagram of the balance circuit with a discharge function which concerns on a modification is shown in FIG. The balance circuit with a discharge function according to the modification will be described by describing only the differences from the embodiment.

  In this balance circuit with a discharge function, a diode D5 is provided instead of the diode D6. The diode D5 has an anode connected to the potential point P and a cathode connected to the base electrode of the NPN transistor Tr1.

  The power stop detection circuit 3 discharges only the capacitor C1 using only the discharge circuit 2a by stopping the supply of the potential V1 to the DC power supply line VH. For example, as shown in FIG. 6, the power stop detection circuit 3 is connected to both ends of the AC power supply AC and between the base electrode of the NPN transistor Tr1 and the cathode of the diode D5.

  In the balance circuit with a discharge function having such a configuration, the diode D6 and the power supply stop detection circuit 3 do not perform a special function in the balance operation of the capacitors C1 and C2 during normal operation. Therefore, since it is the same as the operation of the balance circuit with a discharge function according to the embodiment, detailed description is omitted.

  Next, the discharging operation of the capacitors C1 and C2 when the power is stopped will be described. When the supply of alternating current from the alternating current power supply AC is stopped, the power supply stop detection circuit 3 detects the stop and raises the potential of the base electrode of the NPN transistor Tr1. This operation can be performed, for example, by pulling up the base electrode of the NPN transistor Tr2 by turning on the switch inside the power stop detection circuit 3. When the supply of alternating current from the alternating current power supply AC is stopped, the supply of the potential V1 is also stopped.

  As the potential of the base electrode of the NPN transistor Tr1 increases, the voltage VBE1 increases and the NPN transistor Tr1 becomes conductive. Due to the conduction, the capacitor C1 is discharged through the discharge circuit 2a.

  At this time, since the diode D5 supports the voltage between the potential point P and the base electrode of the NPN transistor Tr1, the potential V3 at the potential point P is directly related to the increase in the potential of the base electrode of the NPN transistor Tr1 by the power stop detection circuit 3. Not affected. In other words, the diode D5 ensures the constantness of the ratio at the potential V3 obtained by internally dividing the potentials V1 and V2 by a constant ratio.

  And the electric potential V1 falls with discharge of the capacitor | condenser C1. At this time, since the capacitor C2 is not discharged, the voltage across the capacitor C2 does not change and the potential V4 does not fluctuate. Further, since the potential V3 is a value obtained by internally dividing the potentials V1 and V2 by a certain ratio, the potential V3 decreases as the potential V1 decreases.

  Therefore, the voltage VBE2 of the PNP transistor Tr2 increases, the PNP transistor Tr2 becomes conductive, and the capacitor C2 is discharged via the discharge circuit 2b.

  Thereafter, since the NPN transistor Tr1 is turned on by the power stop detection circuit 3, the capacitor C1 is discharged, and the balance circuit 2 discharges the capacitor C2 so that the potentials V3 and V4 are equal to each other.

  As described above, the balance of the voltages across the capacitors C1 and C2 can be maintained during normal operation, and the capacitors C1 and C2 can be discharged when the power is stopped.

It is a notional block diagram of the balance circuit with a discharge function according to the embodiment. It is a figure which shows the relationship of each electric potential V1-V4 when the both-ends voltage of the capacitor | condenser C1 rises. It is a figure which shows the relationship of each electric potential V1-V4 when the both-ends voltage of the capacitor | condenser C2 rises. It is a notional block diagram of the balance circuit with a discharge function according to the embodiment. It is a graph which shows the voltage of a pair of capacitor | condenser C1, C2. It is a notional block diagram of the balance circuit with a discharge function concerning a modification.

Explanation of symbols

2 Balance circuit 2a, 2b Discharge circuit 3 Power supply stop detection circuit D5, D6 Diode P Potential point Tr1 NPN transistor Tr2 PNP transistor V1 to V4 potential

Claims (4)

A first DC power supply line (VH) to which a predetermined first potential (V1) is supplied;
A second DC power supply line (VL) to which a second potential (V2) lower than the first potential is supplied;
A first capacitor (C1) connected between the first DC power supply line and the second DC power supply line;
A second capacitor (C2) connected in series with the first capacitor on the second DC power line side;
A first discharge circuit (2a) for discharging the first capacitor;
A second discharge circuit (2b) for discharging the second capacitor;
When the third potential (V4) between the first capacitor and the second capacitor is smaller than a predetermined value (V3), the first capacitor is discharged using the first discharge circuit; A balance circuit (2) for discharging the second capacitor using the second discharge circuit when the third potential is larger than the predetermined value;
Since the supply of the first potential is stopped, only the first capacitor is discharged using only the first discharge circuit, or the second discharge circuit is used only using the second discharge circuit. A balance circuit with a discharge function, comprising a power stop detection circuit (3) for discharging only the capacitor. The balance circuit (2)
A potential point (P) at which a fourth potential (V3) obtained by internally dividing the first potential (V1) and the second potential (V2) at a constant ratio is supplied as the predetermined value.
The balance circuit with a discharge function according to claim 1, comprising: One end of the second discharge circuit (2b) is connected between the first capacitor (C1) and the second capacitor (C2), and a control terminal is connected to the potential point (P). A second transistor (Tr2)
The balance circuit (2) is connected between the control terminal of the second transistor and the potential point, and is a second rectifier element (current rectifier element) that allows current to flow only from the second transistor toward the potential point. D6)
The balance circuit with a discharge function according to claim 2, wherein the power stop detection circuit (3) conducts the second transistor to discharge only the second capacitor. One end of the first discharge circuit (2a) is connected between the first capacitor (C1) and the second capacitor (C2), and a control terminal is connected to the potential point (P). A first transistor (Tr1),
The balance circuit (2) is connected between the control terminal of the first transistor and the potential point, and a first rectifier element (current rectifier element) that allows current to flow only from the potential point toward the first transistor. D5)
The balance circuit with a discharge function according to claim 2, wherein the power stop detection circuit (3) conducts the first transistor to discharge only the first capacitor.

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