JP3680563B2 - Half-bridge converter backup circuit - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a backup circuit for a half-bridge converter in which a backup battery can supply the DC power even when a single-phase AC power input to a half-bridge converter that outputs DC power fails.
[0002]
[Prior art]
FIG. 3 is a circuit diagram showing a conventional example of backup when the AC power supply of the half-bridge converter fails. In this conventional circuit, a first switching circuit 4 in which an insulated gate bipolar transistor (hereinafter abbreviated as IGBT) as a semiconductor switching element and a diode are connected in antiparallel, and a second switching circuit having the same configuration as the first switching circuit 4 is provided. The switching circuit 5 is connected in series to form a first series circuit, the first capacitor 6 and the second capacitor 7 are connected in series to form a second series circuit, and the first series circuit and the second series circuit are connected to each other. A half-bridge converter 10 is configured by connecting a series circuit in parallel. A filter circuit is inserted between the single-phase AC power supply 1 and the half-bridge converter 10, and this filter circuit is composed of a filter capacitor 2 and a filter reactor 3 as an AC reactor. By turning on and off the first switching circuit 4 and the second switching circuit 5 constituting the half-bridge converter 10, the AC power from the single-phase AC power source 1 is converted into DC power, and the positive terminal 8 and the negative electrode Output from terminal 9.
[0003]
When the load (not shown) connected between the positive electrode terminal 8 and the negative electrode terminal 9 may cause a serious trouble even in a very short power failure (for example, a computer or an electronic circuit), a single-phase alternating current In order to back up a power failure of the power supply 1, a backup circuit including a battery 21 and a boost chopper 20 that boosts DC power from the battery 21 is provided. In general, since the load voltage is often higher than the battery voltage, a step-up chopper is used, but when the load voltage is lower, the step-down chopper is used. The output side of the boost chopper 20 is connected to both ends of the second series circuit.
[0004]
The step-up chopper 20 includes a DC reactor 22, a chopper switch circuit 23 having a reverse parallel connection of an IGBT and a diode, and a first blocking diode 24. The step-up operation is as follows. That is, the chopper switch circuit 23 is first turned on to store energy in the DC reactor 22, and then is turned off to release the energy stored in the DC reactor 22 to the load. It is well known that the voltage of the battery 21 can be boosted to a desired value by appropriately adjusting the ratio of the off time. Therefore, if the undervoltage detector (not shown) detects that the voltage of the single-phase AC power supply 1 has decreased to a predetermined value or less (or a power failure), the boost chopper 20 immediately starts to operate, and the single-phase AC power supply 1 Instead, the battery 21 supplies DC power to the load.
[0005]
[Problems to be solved by the invention]
The battery 21 used as a backup power source is expensive and heavy. For this reason, it is desirable to reduce the capacity of the battery 21 as much as possible and to reduce the number and series of the battery 21 in order to reduce the size and weight. By the way, if the number of batteries in series is reduced, the output voltage becomes lower, so the boost ratio of the boost chopper 20 must be increased. The chopper switch circuit 23 in order that it will be using a semiconductor switching element having a high breakdown voltage, since the loss of the high-voltage element is Ru Oh large than the loss of the low voltage element, there is a problem that reduces the efficiency of the device However, since the capacity of the battery 21 must be increased by the increase in loss, there is a disadvantage that the apparatus becomes large and expensive.
[0006]
Furthermore, when the boosting ratio of the boosting chopper 20 is increased, the time from when the power failure is detected until the boosting chopper 20 starts operating and supplying DC power to the load becomes longer, so that the power to the load is not interrupted. Since the capacities of the first capacitor 6 and the second capacitor 7 constituting the bridge converter 10 have to be increased, there is a disadvantage that the apparatus is further increased in size and the price is increased.
[0007]
Therefore, the present invention is to improve the apparatus efficiency during the backup operation without increasing the capacity of the capacitor constituting the half-bridge converter.
[0008]
[Means for Solving the Problems]
In order to achieve the above object, the backup circuit of the half-bridge converter of the present invention includes:
Two pairs of the second series circuit of the first series circuit and two capacitors switching circuit connected in series are connected in series and parallel connection, are inserted AC reactor between the single-phase AC power source and the parallel connection If the output side of a boost chopper that boosts and supplies DC power from a backup battery is connected to both ends of one capacitor of the second series circuit of the half-bridge converter and the single-phase AC power supply fails, the AC The first switch inserted between the reactor and the single-phase AC power supply is turned off, and the single-phase AC power supply side terminal of the AC reactor and the connection point between the capacitors of the second series circuit are short-circuited by the second switch. The boost chopper is operated, and one switching circuit of the first series circuit is turned on / off.
[0009]
Or, two sets of the second series circuit wherein the first series circuit and the two capacitors are connected in series to the switching circuit connected in series are connected in parallel, insert the AC reactor between the single-phase AC power source and the parallel connection An output side of a step-up chopper that boosts and supplies DC power from a backup battery to both ends of one capacitor of the second series circuit of the half-bridge converter, and a DC reactor that constitutes the step-up chopper; When the second reactor that is magnetically coupled is connected to both ends of the other capacitor of the second series circuit via a blocking diode, and the single-phase AC power supply fails, the AC reactor and the single-phase AC power supply Between the single-phase AC power supply side terminal of the AC reactor and the capacitors of the second series circuit. And short-circuiting the consent second switch, wherein with operating a step-up chopper, shall be one on-off operation of the switching circuit of the first series circuit.
[0010]
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. A single-phase AC power source 1, a filter capacitor 2, a filter reactor 3 as an AC reactor, and a positive electrode terminal shown in the circuit of the first embodiment of FIG. 8, the negative terminal 9, the half-bridge converter 10 and its components, the boost chopper 20 and its components, and the name, application, and function of the battery 21 are the same as those of the conventional circuit described above with reference to FIG. These descriptions are omitted.
[0011]
In the circuit of the first embodiment, the first switch 31 is inserted between the single-phase AC power source 1 and the half-bridge converter 10 to short-circuit the power source side of the filter reactor 3 and the intermediate point of the second series circuit. A switch 32 is newly installed, and the output side of the boost chopper 20 is connected to both ends of the second capacitor 7 (conventionally, both ends of the second series circuit).
[0012]
During normal operation, that is, when the single-phase AC power supply 1 supplies power to the load, the first switch 31 is on and the second switch 32 is off, but the voltage of the single-phase AC power supply 1 is below a predetermined value. In the case of a drop (or power failure), the first switch 31 is opened to disconnect the single-phase AC power supply 1 from the half-bridge converter 10 and the second switch 32 is closed. At the same time, the chopper switch circuit 23 starts an on / off operation, whereby the boost chopper 20 boosts the DC power from the battery 21 and supplies it to the second capacitor 7. Here, since the second capacitor 7 shares a half of the load voltage, the boosting ratio of the boosting chopper 20 may be half that of the conventional one.
[0013]
Simultaneously with the start of the operation of the step-up chopper 20, the second switching circuit 5 is also started to turn on / off. When the second switching circuit 5 is turned on, the second capacitor 7 is used as a power source, and the path “the positive side of the second capacitor 7 → the second switch 32 → the second switching circuit 5 → the negative side of the second capacitor 7”. The current flows and the energy is stored in the filter reactor 3. Next, when the second switching circuit 5 is turned off, a current flows through a path “filter reactor 3 → first switching circuit 4 → first capacitor 6 → second switch 32 → filter reactor 3” to charge the first capacitor 6. To do. That is, the energy stored in the second capacitor 7 (this energy is supplied from the boost chopper 20 as described above) moves to the first capacitor 6 by the on / off operation of the second switching circuit 5. Thus, the same DC voltage as before appears between the positive terminal 8 and the negative terminal 9.
[0014]
FIG. 2 is a circuit diagram showing a second embodiment of the present invention. In the circuit of the second embodiment, a two-winding reactor 41 is used as a constituent element of the boost chopper 40, and the second winding of the boost chopper 40 is shown. 43 and the second blocking diode 44 are different from the circuit of the first embodiment shown in FIG.
That is, in this second embodiment, the step-up chopper 40 includes a two-winding reactor 41 having a first winding 42 as a DC reactor and a second winding 43 as a second reactor, the chopper switch circuit 23, and a first blocking. A diode 24 and a second blocking diode 44 are included. Here, the first winding 42 and the second winding 43 are magnetically coupled, and a second blocking diode 44 is connected to the second winding 43 in series, and this series circuit is connected to the other winding. It connects to the 1st capacitor | condenser 6 as a capacitor | condenser.
[0015]
In the circuit of the first embodiment shown in FIG. 1 described above, the step-up chopper 20 immediately starts operating and charges the second capacitor 7 when the single-phase AC power supply 1 is interrupted, but the first switch 31 and the second switch 32 are connected. Until the switching is completed, the half-bridge converter 10 cannot be chopper-operated. Therefore, the charging of the first capacitor 6 is delayed with respect to the second capacitor 7. Therefore, if a series circuit of the second winding 43 and the second blocking diode 44 is connected to the second capacitor 7, the turn ratio between the first winding 42 and the second winding 43 when the boost chopper 40 starts operation. Since the second capacitor 7 is immediately charged with a voltage corresponding to the above, it is not necessary to increase the capacitance of the first capacitor 6 and the second capacitor 7 constituting the second series circuit.
[0016]
【The invention's effect】
By adding a battery and a step-up chopper to a half-bridge converter that is connected to a single-phase AC power source and supplies DC power to a load, a power failure of the single-phase AC power source can be backed up. However, since the boosting chopper generally has a large boosting ratio, the loss of the boosting chopper is large, and there is a disadvantage that the efficiency of the apparatus must be reduced and the capacity of the backup battery must be increased. In the present invention, a first switch that disconnects the single-phase AC power supply and the half-bridge converter and a second switch that short-circuits the input side of the half-bridge converter via a filter reactor are provided, and a power failure of the single-phase AC power supply is provided. Sometimes the boost chopper charges one capacitor of the second series circuit that constitutes the half-bridge converter, and the half-bridge converter operates as a chopper to charge the other capacitor of the second series circuit. With such a configuration, the step-up ratio of the step-up chopper can be reduced to half that of the prior art, so that the loss can be reduced by eliminating the need for a high voltage semiconductor switch element. As a result, the efficiency of the entire apparatus can be improved, and the battery capacity can be reduced by the amount of loss, so that the effect of reducing the size and weight of the apparatus and reducing the price can be obtained.
[0017]
Furthermore, by using a two-winding reactor as the DC reactor for the boost chopper so that the delay time until the half-bridge converter starts the chopper operation can be covered, each capacitor constituting the second series circuit can be covered. Since the capacitance can be reduced, the effect of further reducing the size and weight of the device and reducing the price can be obtained.
[Brief description of the drawings]
FIG. 1 is a circuit diagram showing a first embodiment of the present invention. FIG. 2 is a circuit diagram showing a second embodiment of the present invention. Circuit diagram showing an example [Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Single-phase alternating current power supply 2 Filter capacitor 3 Filter reactor 4 as an AC reactor 1st switching circuit 5 2nd switching circuit 6 1st capacitor 7 2nd capacitor 10 Half bridge converters 20 and 40 Boost chopper 21 Battery 22 DC reactor 23 Chopper switch Circuit 24 First blocking diode 31 First switch 32 Second switch 41 Two-winding reactor 42 First winding 43 as a DC reactor Second winding 44 as a second reactor Second blocking diode

Claims (2)

Connecting one terminal of a single-phase AC power source through an AC reactor to a coupling point between the switching circuits of the first series circuit in which two sets of switching circuits composed of semiconductor switching elements and diodes connected in reverse parallel are connected in series; The other terminal of the single-phase AC power supply is connected to a connection point between the capacitors of a second series circuit in which two capacitors are connected in series, and the first series circuit and the second series circuit are connected in parallel. In the half-bridge converter configured to extract DC power from the connection point,
Wherein a backup battery, which is connected to both ends of one of the capacitors of the second series circuit, a step-up chopper and supplying the boosted DC power from the backup battery Previous Stories hand of the capacitor, the AC reactor and A first switch inserted between a single-phase AC power source and a second switch for short-circuiting a single-phase AC power source side terminal of the AC reactor and a coupling point between the capacitors of the second series circuit. When the phase AC power supply fails, the first switch is opened, the second switch is closed, the step-up chopper is operated, one switching element of the first series circuit is turned on / off, and the parallel connection point A backup circuit for a half-bridge converter, wherein DC power is taken out of the circuit. Connecting one terminal of a single-phase AC power source through an AC reactor to a coupling point between the switching circuits of the first series circuit in which two sets of switching circuits composed of semiconductor switching elements and diodes connected in reverse parallel are connected in series; The other terminal of the single-phase AC power supply is connected to a connection point between the capacitors of a second series circuit in which two capacitors are connected in series, and the first series circuit and the second series circuit are connected in parallel. In the half-bridge converter configured to extract DC power from the connection point,
Configuration and the backup battery, which is connected to both ends of one of the capacitors of the second series circuit, a step-up chopper and supplying the boosted DC power from the backup battery Previous Stories hand of the capacitor, the step-up chopper A second reactor that is magnetically coupled to a DC reactor that is connected to the other capacitor of the second series circuit, and a blocking diode that is inserted in series between the second reactor and the other capacitor; A first switch inserted between the AC reactor and the single-phase AC power supply, and a second switch for short-circuiting a single-phase AC power supply side terminal of the AC reactor and a connection point between the capacitors of the second series circuit The first switch is opened at the time of a power failure of the single-phase AC power supply, the second switch is closed, and the boost chopper is created. Is allowed, the one switching element is turned on and off operation of the first series circuit, half-bridge converter backup circuit, characterized in that retrieving the DC power from the parallel connection point.

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