JPS6051358B2 - inverter circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter circuit that eliminates spike voltages applied to switching elements.

A conventional inverter circuit is configured as shown in FIG. 1, for example.

To explain the operation of this circuit, 1 of drive transformer 1
A drive signal shown in FIG. 2A is supplied to the secondary winding 2, and a signal having the same waveform is generated in the secondary winding 3, whereby the transistor 4, which is a switching element, performs a switching operation.
That is, from time to time, the transistor 4 is conductive, and a current flows through the DC power supply 5, the A side of the primary winding 7 of the inverter transformer 6, and the collector-emitter loop of the transistor 4. At this time, the diode 8 is cut off because it has a reverse voltage. Next, the drive signal (transistor 4 in the section from time tl to time 2 in FIG. A back electromotive force is generated, the diode 8 becomes conductive, and the energy is regenerated to the DC power supply 5. Next, at a certain time, the transistor 4 becomes conductive again.The same operation is repeated, and the transformer 6 As shown in the opening of Figure 2, a rectangular wave pulse with a potential approximately twice that of the power supply 5 is generated between the primary winding 7, and this is converted to a predetermined voltage by the transformer 6. , is supplied from the secondary winding 9 to the load 10.When the transistor 4 is cut off, a voltage is generated between the emitter and the collector, which is the voltage of the power supply 5 and the voltage of the primary winding superimposed. is applied, but transformer 6
Since the primary winding 7 of is divided into primary windings A and B, if the result is not perfect, there will be leakage inductance, and a spike-like voltage will occur in the primary winding 7 at the time of interruption. This spike voltage will be applied to transistor 4. To reduce spike voltage, primary windings A and B
All that is required is to strengthen the coupling between the two coils, and bifilar winding is usually used as a method for this purpose, but it is not possible to completely reduce the leakage inductance to zero, and a spike voltage still occurs. Therefore, a transistor 4 having a high breakdown voltage between the collector and emitter is required, which not only makes the transistor 4 expensive, but also causes problems in that the switching operation becomes extremely slow. In view of the above problems, an object of the present invention is to provide an inverter circuit that can completely eliminate the spike voltage generated in the primary winding of an inverter transformer and can operate with switching elements having a low withstand voltage. However, there is a DC power supply 13 and a switching element 1 that repeatedly switches on and off.
2 and the primary winding 17 of the inverter transformer 14, and the primary winding 17 is configured with a series circuit of a capacitor 21 and a diode 19 whose direction is opposite to the DC power supply 13. The circuit 20 is connected in parallel so as to regenerate the energy stored in the primary winding 17, and the power supply 13 connects the capacitor 21 to the primary winding between the connection point of the capacitor 21 and the diode 19 and the power supply 13. The point is that the choke 22 is connected so as to be charged via the terminal 17.

Hereinafter, the present invention will be explained according to the illustrated embodiment.
In the figure, 11 is a drive transformer, 12 is an NPN transistor as a switching element, 13 is a DC power supply, 1
4 is an inverter transformer, the secondary winding 15 of which is connected to a load 16, the primary winding 17 of which is connected in parallel with a regenerative circuit 20 composed of a series circuit of a capacitor 21 and a diode 19; 21 is configured to be charged from a power source 13 via a primary winding 17 and a choke 22.

Next, the operation of this circuit will be explained.

When power supply 13 is applied, capacitor 21 connects primary winding 1
7. Charged to the same voltage as the power supply 13 via the choke 22. The transistor 12 performs a switching operation in the same way as in the conventional case by a drive signal from the drive transformer 11.
When the transistor 12 is energized, the loop current 11 and the current 12 flow through the power source 13, the primary winding 17 of the inverter transformer 14, the collector of the transistor 12, the emitter loop, the capacitor 21, the transistor 12, and the choke 22, and the current 12 flows through the primary winding. 17. Energy is stored in the choke 22. When the transistor 12 is cut off, a voltage is generated in the primary winding 17 of the inverter transformer 14 and the choke 22 in the direction shown in FIG. voltage is power supply 1
3, the diode 19 becomes conductive, current flows, the current L flows, and the energy stored in the choke 22 is regenerated to the DC power supply 13 via the diode 19. The energy stored in the primary winding 17 also charges the capacitor 21. However, when the voltage of the capacitor 21 becomes higher than the voltage of the power supply 13, a current flows in the loop of the primary winding 17, the capacitor 21, the choke 22, and the power supply 13. That is, when the transistor 12 is on, the voltage of the capacitor 21 reduced by the current 12 is restored to the same level as the power supply 13 by the energy stored in the primary winding 17, and the energy stored in the choke 22 is transferred to the power supply 13.
to be regenerated.

Thereafter, similar operations are repeated.

Then, a pulse waveform having a potential approximately twice that of the power supply 13 is generated between the primary winding 17, and a pulse of a predetermined voltage is supplied to the load 16, as in the conventional case. However, 1
Since the secondary winding 17 is not divided and is a single piece, there is essentially no leakage inductance, and no spike voltage occurs at all as in the prior art. Also, the energy stored in the choke 22, capacitor 21, and primary winding 17 is transferred to the power source 13.
Since the energy is regenerated, there is essentially no power loss. Therefore,
There is no need to consider spike voltages in the voltage applied between the collector and emitter of the transistor 12, and a transistor 12 with a low withstand voltage can be used, making the transistor 12 inexpensive and providing good switching operation.

Although the transistor 12 is used as the switch element in the above embodiment, a semiconductor switch such as a GTO thyristor may also be used, and although the embodiment uses a separately excited inverter, it is also possible to use a self-excited inverter. You can.
Furthermore, the load 16 may be connected in parallel to the primary winding. The present invention includes a DC power supply 13 and a switch element 1.
2 and the primary winding 17 of the inverter transformer 14, and a regenerative circuit 20 is connected in parallel to the primary winding 17, and the primary winding 17 of the inverter transformer 14 is divided. Since there is no leakage inductance, there is essentially no leakage inductance and no voltage spikes occur in the primary winding 17. Therefore, there is no need to consider spike voltages in the voltage applied to the switch element 12, and a switch element 12 with a low withstand voltage can be used, which not only makes the switch element 12 less expensive, but also provides good switching operation. becomes. Moreover, the regeneration circuit 20 is connected to the capacitor 2.
Since it is composed of a series circuit of 1 and diode 19,
The regeneration circuit 20 does not require a transformer or a power supply, and the circuit configuration is extremely simple, making it easy to manufacture and providing at low cost.

Furthermore, since the regenerative circuit 20 is in parallel with the primary winding 17, the surge generated by the switching operation of the switch element 12 can be brought to the power supply side instead of the load side, and the surge can be reliably suppressed without adversely affecting the load. can be lost. In addition, a choke 22 is connected between the connection point between the capacitor 21 and the diode 19 and the power supply 13 so that the power supply 13 charges the capacitor 21 via the primary winding 17. Switch element 1
When the capacitor 12 turns on and off, the capacitor 12 can absorb surges while operating so that energy storage and regeneration occurs in the same way as the primary winding 17. There is no wasted power loss when the choke 22,
Since the energy stored in the capacitor 21 and the primary winding 17 is regenerated to the power supply 13, there is essentially no power loss and the efficiency is very high.

[Brief explanation of drawings]

FIG. 1 is an inverter circuit diagram showing a conventional example, FIG. 2 is a waveform diagram for explaining its operation, and FIG. 3 is a circuit diagram of an inverter circuit showing an embodiment of the present invention. 12...NPN transistor (switch element), 13
... Current power supply, 14 ... Inverter transformer, 17
...Primary winding, 19...Diode, 20...Regeneration circuit, 21...Capacitor, 22...Choke.

Claims (1)

[Claims] 1 A loop circuit is formed with a DC power supply 13, a switching element 12 that repeatedly switches on and off, and a primary winding 17 of an inverter transformer 14, and a capacitor 21 and a DC power supply are connected to the primary winding 17. A regeneration circuit 20 constituted by a series circuit with a diode 19 in the opposite direction to 13 is connected in parallel so as to regenerate the energy stored in the primary winding 17, and a connection point between the capacitor 21 and the diode 19 is connected in parallel to regenerate the energy stored in the primary winding 17. An inverter circuit characterized in that a choke 22 is connected between the power supply 13 and the power supply 13 so that the capacitor 21 is charged by the power supply 13 via the primary winding 17.