JP4033158B2 - Power circuit - Google Patents

Description

  The present invention includes a plurality of power conversion circuits including switching elements for power conversion that perform an ON-OFF operation using a DC voltage as an input, on the primary side of a common transformer, and uses the power from the plurality of power conversion circuits as a load. The present invention relates to a power supply circuit provided with a secondary side DC conversion circuit for supply on the secondary side of the transformer.

In the power supply circuit, for example, when one power conversion circuit of two power conversion circuits provided on the primary side is driven, an overcurrent is generated in the other power conversion circuit due to energy generated in the power conversion circuit. A device in which each power conversion circuit is provided with a backflow prevention diode for preventing the current from flowing is already proposed (see, for example, Patent Document 1).
Japanese Patent Laid-Open No. 9-261958 (FIGS. 1, 2, and 4 to 6)

  In the power supply circuit disclosed in Patent Document 1, although the backflow prevention diode can prevent a current from flowing to the other power conversion circuit due to the energy of the one power conversion circuit, it is turned ON / OFF using a DC voltage as an input. No measures have been taken to reduce the switching noise and switching loss that occur during the ON operation of the operating power conversion switching element, leaving room for improvement.

  In view of the above-mentioned situation, the present invention intends to provide a power supply circuit that can reduce switching noise and switching loss that occur when the power conversion switching element is turned on.

In order to solve the above-described problems, the present invention includes a plurality of power conversion circuits each including a power conversion switching element that performs an ON-OFF operation using a DC voltage as an input, on the primary side of a common transformer, The circuit is provided with a backflow prevention diode for preventing a backflow of current due to an induced voltage from one power conversion circuit to the other power conversion circuit, and a secondary side for supplying power generated by the power conversion circuit to a load In a power supply circuit comprising a DC conversion circuit on the secondary side of the transformer, a resonance coil for being electrically connected to the transformer and energy stored in the resonance coil being charged A resonance capacitor for storing in the form of and a charge accumulated in the resonance capacitor before the switching element is turned on to flow as a resonance current A resonance circuit provided separately from the power conversion circuit for reducing switching noise and switching loss generated at the time of ON operation of the switching element, comprising a closed circuit including a resonance switching element for switching. The transformer is connected to the primary side or the secondary side in an electrically insulated state, and the resonance circuit is shared with the plurality of power conversion circuits, and the power supply side of each power conversion circuit by the resonance circuit A power supply circuit is configured by connecting a capacitor for charging in order to suppress the generation of a reverse voltage of the reverse current blocking diode by charging a resonance current that is fed back to the reverse current blocking diode in parallel with the reverse current blocking diode. did.
Therefore, switching noise and switching loss generated when the switching element is turned on can be reduced by the resonance circuit. Then, the resonance current generated by the resonance circuit is fed back to the power supply side of each power conversion circuit, and a reverse voltage is applied to the backflow prevention diode, but this is stored in the form of charge by the charge capacitor. Therefore, it is possible to avoid the backflow prevention diode from being damaged, and it is possible to use a backflow prevention diode having a small (low) reverse breakdown voltage.

  The plurality of power conversion circuits include a first power conversion circuit including a rectifier circuit that converts a commercial AC voltage from a commercial AC power source into a DC voltage, and the DC voltage from the secondary battery during a power failure of the commercial AC power source. You may comprise from the 2nd power converter circuit which supplies electric power to a load through a secondary side DC converter circuit.

Although switching noise and switching loss generated when the switching element is turned on can be reduced by a resonance circuit, even if a reverse voltage is applied to the backflow prevention diode by providing the resonance circuit, backflow prevention is possible. It is possible to provide a highly reliable power supply circuit capable of reliably avoiding damage to the diode with a charging capacitor. Further, the reverse current blocking diode can be constituted by a diode having a small reverse breakdown voltage such as a Schottky diode. In addition, by composing a resonance circuit provided separately from the power conversion circuit shared for a plurality of power conversion circuits, it is possible to reduce the number of parts by sharing the resonance circuit, This is advantageous in terms of manufacturing and cost. A resonance coil for connecting the resonance circuit to the transformer in an electrically insulated state, a resonance capacitor for storing energy accumulated in the resonance coil in the form of electric charge, and a switching element Compared to the case where the resonance circuit is incorporated in the power conversion circuit by comprising a closed circuit including a resonance switching element for switching the charge accumulated in the resonance capacitor to flow as a resonance current before turning on. Thus, the transformer can be freely arranged on either the primary side or the secondary side, and the degree of freedom in design can be increased.

  The first power conversion circuit includes a rectifier circuit that converts a commercial AC voltage from a commercial AC power source into a DC voltage, and the second power conversion circuit is connected to the secondary battery during a power failure of the commercial AC power source. By configuring the unit to supply power to the load through the secondary side DC conversion circuit with DC voltage, it becomes possible to supply power to the load with the second power conversion circuit even in the event of a power failure. A high power circuit can be obtained.

  FIG. 1 shows a forward type power supply circuit. This power supply circuit is connected to a secondary winding N2 of a common high-frequency transformer (which may be a low-frequency transformer) 1 in an electrically insulated state and is a secondary for supplying DC power to the load 2 Side DC conversion circuit 3 and the first winding N1 on the primary side of the common high-frequency transformer 1 are connected in an electrically insulated state, and a DC voltage is obtained by rectifying the AC voltage from the commercial AC power supply 4. A first power conversion circuit 6 for supplying power to the secondary side DC conversion circuit 3 via the common high-frequency transformer 1 by a DC voltage output via the rectifier circuit 5 for conversion to The secondary side DC conversion circuit 3 is connected to the second winding N3 on the primary side of the high frequency transformer 1 in a state of being electrically insulated, and through the common high frequency transformer 1 by the output of the secondary battery 7. Second power to supply power to And a circuit 8. As the secondary battery 7, a fuel cell, a solar battery, a nuclear battery or the like may be used, and a generator or the like may be used instead of the secondary battery 7. One of the two power conversion circuits 6 and 8 is a power conversion circuit that operates with an AC voltage from a commercial AC power supply, and the other is a power conversion circuit that operates with a DC voltage from a secondary battery. Either of them may be a power conversion circuit that operates with power from a commercial AC power supply, or may be a power conversion circuit that operates with a DC voltage. In addition, it is possible to provide three or more power conversion circuits. In this case, if a power supply circuit is configured by providing at least one power source unit configured with a commercial AC power source and one configured with a DC power source such as a secondary battery, for example, a commercial AC power source There is an advantage that power can be supplied to the secondary side DC conversion circuit 3 using a DC power supply even during a power failure. In addition to the forward type as shown in FIG. 1, the power supply circuit may be a flyback type, a full bridge type, a half bridge type, or the like, and may be configured as any type of power supply circuit.

As shown in FIG. 1, the first power conversion circuit 6 is connected to the first winding N1 on the primary side of the high-frequency transformer 1 and repeats ON-OFF to generate a voltage set to the secondary side. An FET Q1 as a power conversion switching element for supply and a reverse current blocking diode 9 for preventing a reverse current flow due to an induced voltage from the second power conversion circuit 8 in operation are provided.
The second power conversion circuit 8 is connected to the second winding N3 on the primary side of the high-frequency transformer 1, and is used to supply a voltage set to the secondary side by repeatedly turning on and off. An FET Q3 serving as a conversion switching element and a reverse current blocking diode 10 for preventing a reverse current flow due to an induced voltage from the first power conversion circuit 6 in operation are provided.
Gate circuits 11 and 12 to which a control signal from a control device (not shown) is input are connected to the FET Q1 and FET Q3, and the FET Q1 and FET Q3 are turned on and off by the gate signals from the gate circuits 11 and 12. It has become so.

A resonance circuit 13 for reducing switching noise and switching loss generated when the FET Q1 and FET Q3 are turned on is connected to the secondary side of the transformer 1 in an electrically insulated state. Here, the resonance circuit 13 is arranged on the secondary side of the transformer 1, but it may be arranged on the primary side. Thus, by providing the resonance circuit 13 shared for the plurality of power conversion circuits 6 and 8, the number of components can be reduced compared to the case where the resonance circuit 13 is provided for all the power conversion circuits 6 and 8. There is an advantage that can be achieved.
A resonance coil N4 for connecting the resonance circuit 13 to the secondary side of the transformer 1 in an electrically insulated state, and energy stored in the resonance coil N4 is stored (charged) in the form of electric charges. And a closed circuit including a resonance capacitor 14 for switching, and a FET Q2 as a switching element for resonance for switching the current of the resonance coil N4 to flow as a resonance current before the FET Q1 or Q3 is turned on. by, to freely change the position of the resonant circuit 13 (although disposed on the secondary side in the figure, may be a primary side) Ru advantage there that can. Although not shown, the FET Q2 is connected to a gate circuit (not shown) to which a control signal from a control device (not shown) is input. The resonance circuit 13 is not limited to the form shown in the figure, and may be configured in any form.

  In each of the power conversion circuits 6 and 8, when the current of the resonance coil N4 of the resonance circuit 13 is cut off by the resonance switching element Q2, the power conversion circuits 6 and 8 are connected to the primary side via the transformer 1. Charging capacitors 15 and 16 are provided for charging in the form of electric charges that resonance current flows and reverse voltage is applied to the reverse current blocking diodes 9 and 10, and these capacitors 15 and 16 include the reverse current blocking diodes 9 and 16. 10 in parallel.

A case will be described in which the first power conversion circuit 6 is operated to drive the load 2 disposed on the secondary side by supplying power from the power conversion circuit 6. 2A shows a case where the charging capacitors 15 and 16 are not provided, and FIG. 2B shows various waveforms when the charging capacitors 15 and 16 are provided. .
First, FIGS. 2A and 2B show pulse waveforms for turning the FET Q1 on and off at a predetermined cycle. At the same time as the FET Q1 is turned off, the potential at the point a in FIG. 1 rises as shown in FIGS. 2A and 2B, so that the charging current I for charging the capacitor 14 flows in the resonance circuit 13. Start (period d1). Before the charging of the capacitor 14 is completed, a gate signal (see FIG. 2B) for turning on the FET Q2 is output to a gate circuit (not shown) of the FET Q2. When the charging is completed, the capacitor 14 starts discharging electric charges, and a current I flows in a direction opposite to the direction as shown in FIG. The FET Q2 is turned off immediately before the FET Q1 is turned on, and the reverse current I flowing through the resonance coil N4 is converted into the current I1 of the primary winding N1 shown in FIG. By charging this reverse current I1 with a charging capacitor 15 connected in parallel to the backflow prevention diode 9, the potential at point a and the potential between b and a in FIG. 1 are V1 in FIG. As shown in FIG. 2B, the voltage does not change abruptly, and the change can be a gradual voltage change (a voltage close to 0) as shown by V2 in FIG. 2B, and the backflow blocking diodes 9 and 10 are damaged. As a matter of course, it is possible to use an element having a small (low) reverse breakdown voltage such as a Schottky diode as the backflow blocking diodes 9 and 10. Since the switching element Q1 is turned on after the potential at the point of the switching element Q1 is sufficiently lowered by the resonance current I1 of the primary winding N1, the switching noise and switching loss generated when the switching element Q1 is turned on are reduced. be able to.

  FIG. 1 shows a power supply circuit diagram in which the reverse current blocking diodes 9 and 10 and the charging capacitors 15 and 16 for the reverse current blocking diodes 9 and 10 are connected to the negative side of the primary windings N1 and N3 of the high-frequency transformer 1. Thus, the reverse current blocking diodes 9 and 10 are connected to the positive side of the primary side windings N1 and N3 or the negative side of the switching element Q1, and the charging capacitors 15 and 16 are connected to the primary side windings as shown in FIG. It may be a power supply circuit diagram connected in a state extending over the plus side of N1 and N3 and the minus side of the switching element Q1 connected in series to the minus side of the primary windings N1 and N3.

  Further, FIG. 4 shows a cascade forward type circuit using a FET having a low (small) ON resistance in order to reduce the loss due to the resistance component of the switching element. Since the FET having a low ON resistance has a low withstand voltage, two FETs Q11 and Q12 or Q31 and Q32 are connected in series so that the off-time voltage of the switching element can be divided and reduced. These two FETs Q11, Q12 or Q31, Q32 are driven to be turned on and off at the same timing, but there is a deviation in the timing due to variations in the elements themselves. For this reason, it is possible to prevent a voltage exceeding the withstand voltage from being applied to the FET Q11 or Q12 (Q31 or Q32) that was previously turned off, and the primary winding N1 on the primary side when both FETs Q11 and Q12 (or Q31, Q32) are off. Alternatively, capacitors 17, 18 or 19, 20 are provided to stabilize the potential of the second winding N3. By providing these capacitors 17, 18 or 19, 20 FETs Q11, Q12 or Q31, Q32 having a low withstand voltage can be used. In addition, the capacitors 17, 18 or 19, 20 also serve as the charging capacitors. The capacitors 17, 18, 19, and 20 include a common line (medium line) 21 or 22 connected to an intermediate portion (middle point) of the first winding N 1 or the second winding N 3 on the primary side and a power source (rectifier circuit). 5 is connected between the positive side (positive output terminal) of the DC voltage from 5 and between the common line (medium line) 21 or 22 and the negative side (negative output terminal). In other words, the common line (middle line) 21 or 22 connected to the intermediate part (middle point) of the first winding N1 or the second winding N3 on the primary side and the drain of the FET Q11 provided on the plus side The capacitors 17, 18 or 19, 20 are connected between the common line (medium line) 21 or 22 and the source of the FET Q12 provided on the negative side. Reference numerals 9 and 10 shown in FIG. 4 denote the above-described reverse current blocking diodes, which are positioned closer to the input side (rectifier circuit 5 side) than the connection point of the positive and negative output terminals of the DC voltage of the capacitors 17, 18 or 19, 20. Yes. Further, 11A, 11B, 12A, and 12B shown in FIG. 4 are gate circuits for the FETs Q11, Q12, Q31, and Q32. FIG. 5 shows various waveforms in the circuit shown in FIG. 4. In this case as well, by providing capacitors 17, 18 or 19, 20 as in FIG. 2, the source voltage of FET Q11 and the drain voltage of FET Q12 are changed. The change can be maintained in a gradual state.

  FIGS. 6 and 7 show flyback power supply circuit diagrams, FIGS. 8 and 9 show half-bridge power supply circuit diagrams, and FIGS. 10 and 11 show full-bridge power supply circuit diagrams. 6 to 11 are the same reference numerals as those used in the power supply circuit diagrams shown in FIGS. 1, 3 and 4.

It is a forward type first power supply circuit diagram with a part omitted. (A) shows various waveforms in the power supply circuit in which the capacitor for charging is omitted, and (b) shows various waveforms in the power supply circuit provided with the capacitor for charging. FIG. 6 is a forward-type second power supply circuit diagram with a part omitted. FIG. 6 is a third cascade forward type power supply circuit diagram with a part omitted. Various waveforms in the power supply circuit shown in FIG. 4 are shown. It is a flyback type 4th power supply circuit diagram which omitted a part. FIG. 9 is a fifth power supply circuit diagram of a flyback type in which a part is omitted. FIG. 10 is a sixth half-bridge power supply circuit diagram with a part omitted. FIG. 10 is a seventh half-bridge power supply circuit diagram with a part omitted. It is a full-bridge type 8th power supply circuit diagram which a part was omitted. It is a 9th power supply circuit diagram of a full bridge type which omitted a part.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 High frequency transformer 2 Load 3 Secondary side DC conversion circuit 4 Commercial AC power supply 5 Rectifier circuit 6, 8 Power conversion circuit 7 Secondary battery 9, 10 Backflow prevention diode 11, 12 Gate circuit 13 Resonance circuit 14 Resonance capacitor 15, 16 Capacitors N1, N3 Primary winding N2 Secondary winding L Set distance N4 Resonance coil

Claims (2)

A plurality of power conversion circuits including switching elements for power conversion that perform ON-OFF operation with a DC voltage as an input are provided on the primary side of a common transformer, and each power conversion circuit includes power from one power conversion circuit to the other power. A reverse current blocking diode for preventing a reverse current flow caused by an induced voltage is provided in the conversion circuit, and a secondary side DC conversion circuit for supplying power generated by the power conversion circuit to a load is provided on the secondary side of the transformer. In the power supply circuit, the resonance coil for connecting to the transformer in an electrically insulated state, the resonance capacitor for storing the energy stored in the resonance coil in the form of charges, A resonance stub for switching in order to cause the charge accumulated in the resonance capacitor to flow as a resonance current before the switching element is turned on. A resonance circuit provided separately from the power conversion circuit for reducing switching noise and switching loss generated during the ON operation of the switching element, the primary side of the transformer or Connected to the secondary side in an electrically insulated state, the resonance circuit is shared with the plurality of power conversion circuits, and a resonance current is fed back to the power supply side of each power conversion circuit by the resonance circuit. A power supply circuit comprising a charge capacitor connected in parallel to the reverse current blocking diode for charging in the form of electric charge to suppress generation of a reverse voltage of the reverse current blocking diode .   The plurality of power conversion circuits include a first power conversion circuit including a rectifier circuit that converts a commercial AC voltage from a commercial AC power source into a DC voltage, and the DC voltage from the secondary battery during a power failure of the commercial AC power source. The power supply circuit according to claim 1, comprising a second power conversion circuit that supplies power to the load through the secondary side DC conversion circuit.

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