JPS6220785B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an inverter device using a pair of transistors connected in parallel with each other.

Conventionally, there is an inverter device of this type configured as shown in FIG. This device is of the so-called push-pull type, and connects the positive terminal of the DC power supply 1 to the output transformer 3 through the constant current reactor 2.
Transistors 4 and 5 are connected to the common connection point of the next windings N ₁ and N ₂ and have their negative terminals forming a switching circuit.
Connect to each emitter. The transistor 4 has a collector connected to the other end of the primary winding N ₁ , and a base connected to the primary winding N ₁ through a bias resistor 6 .
Connect to the common connection point of N ₂ . Further, the transistor 5 has a collector connected to the other end of the primary winding N ₂ and a base connected via a bias resistor 7 to a common connection point of the primary windings N ₁ and N ₂ .

The output transformer 3 has a resonance capacitor 8 connected between the primary windings N ₁ and N ₂ . In addition, the output transformer 3 has a secondary winding in addition to the primary winding.
N ₃ and a feedback winding N ₄ are provided.

A load 9 is connected between both ends of the secondary winding N ₃ , and one end of the feedback winding N ₄ is connected to the base of the transistor 4 and the other end to the base of the transistor 5 .

Now, when the DC power supply 1 is turned on and a base current is applied to each transistor 4, 5 via the bias resistors 6, 7, one of the transistors 4, 5 is turned on first due to a slight imbalance between the transistors 4, 5. If the transistor 4 were to turn on, a voltage would be applied to the primary winding _N1 of the output transformer 3, and this applied voltage would generate a sinusoidal resonant voltage in the resonant circuit of the primary winding _N1 and the capacitor 8. .

In this case, the collector of the transistor 5 on the off side
A sine wave as shown in Figure 2a is applied between the emitters, and a trapezoidal wave as shown in Figure 2b is applied to the collector of the on-side transistor 4, with harmonics smoothed by the action of the constant current reactor 2. A current is applied.

On the other hand, a sine wave output is generated in the feedback winding _N4 of the output transformer 3 due to the resonant voltage of the resonant circuit.
As a result, transistor 4 turns off, and transistor 5 turns on. However, during this switching, both transistors 4 and 5 turn on slightly, and the output voltage of the feedback winding _N4 causes both transistors 4 and 5 to turn on. A pulse-like base current as shown in Fig. 2c is generated in a closed circuit including the base and emitter in series, and these pulses flow in the negative direction to the transistor 4 going from on to off, and in the positive direction to the transistor 5 going from off to on. It acts to capture and advance the switching operation in each direction. As a result, transistor 5 is now turned on and transistor 4 is turned off. Also, transistor 4 turned off in this state
The output of feedback winding _N4 is applied as a reverse bias between the base and emitter of. This state is shown in FIG. 2d.

Thereafter, the above operation is repeated and the transistor 4
and 5 alternately turn on and off the output transformer 3 of 2.
AC output will now be generated on the next winding _N3 side.

However, with this configuration, the output of the feedback winding, which is given to the off-side transistor as a reverse bias immediately after it is turned off by the base current, has a sine waveform, so the output of the feedback winding is given as a reverse bias immediately after the transistor is turned off. As is clear from the diagram, the voltage is extremely small. For this reason, especially when the transistor operates at a high temperature, the turn-off time of the transistor's shearing characteristics becomes longer, which may increase the switching loss of the transistor and significantly reduce the operating efficiency as an inverter.

In addition, JP-A No. 48-27232 describes a transistor inverter that provides stable oscillation and suppresses the increase in main winding current when the iron core is saturated, thereby improving conversion efficiency. The feedback circuit has been started.

However, during switching, the voltage of the feedback winding and the voltage of the non-saturated reactor are applied to the transistor that turns OFF and ON, and the transistor turns OFF.
It is thought that it is possible to strengthen the activation of the transistor that turns on and off, but only the reverse bias voltage that is the voltage of the feedback winding minus the voltage of the non-saturating reactor is applied to the transistor that turns on and off. Turn-off may become uncertain. As a result, the switching loss of the transistor increases, and the operating efficiency of the inverter may decrease significantly.

The present invention has been made to eliminate the above-mentioned drawbacks, and an object of the present invention is to provide an inverter device in which the switching characteristics of the transistor can be improved by increasing the reverse bias voltage immediately after the transistor is turned off, and an improvement in operating efficiency can be expected. With the goal.

An embodiment of the present invention will be described below with reference to the drawings. In FIG. 3, the same parts as in FIG. 1 are designated by the same reference numerals.

In this case, an inductor 10 is connected between one end of the feedback winding _N4 of the output transformer 3 and the base of the transistor 4.
Insert.

The rest is the same as in FIG. 1, so the explanation thereof will be omitted.

Next, its operation will be explained.

Now, when a base current is applied to each transistor 4, 5 by the DC power supply 1 via the bias resistor 6, 7, one of the transistors 4, 5 is turned on first. If the transistor 4 is now turned on, a voltage is applied to the primary winding N ₁ of the output transformer 3, and this applied voltage generates a sinusoidal resonant voltage in the resonant circuit of the primary winding N ₁ and the capacitor 8. In this case, the collector-emitter voltage of the transistor 5 which is turned off is shown in FIG. 4a, and the collector current of the transistor 4 which is turned on is shown in FIG. 4b.

On the other hand, a sine wave output is generated in the feedback winding _N4 of the output transformer 3 due to the resonant voltage of the resonant circuit.
As a result, transistor 4 turns off, and transistor 5 turns on. However, during this switching, both transistors 4 and 5 turn on slightly, and the output voltage across feedback winding _N4 causes the above-mentioned closed circuit to be turned on. A pulsed base current shown in FIG. 4c is generated. This state is shown in FIG. In other words, when both transistors 4 and 5 are in the on state, a closed circuit including the bases and emitters of transistors 4 and 5 in series is formed in the feedback winding _N4 as shown in FIG. A current i flows. This electric current i is applied as a base current to the transistor 5 turning on in a positive direction and to the transistor 4 turning off in a negative direction, thereby controlling the switching operation of these transistors 4 and 5. By the way, while this current i is flowing, a voltage in the polar direction shown by the solid line in the figure is generated at both ends of the inductor 10, but when the current i disappears and is cut off, a back electromotive force is generated in the reactor 10, and the voltage at both ends is as shown by the broken line in the figure. The polarity is reversed as shown by . As a result, the voltage across the inductor 10 at this time is applied to the feedback winding _N4 , and is applied as a reverse bias to the transistor 4, which turns ON and OFF, and is applied as a forward bias to the transistor 5, which turns OFF and ON. Therefore, the reverse bias voltage at this point can obtain a large value immediately after the transistor 4 is turned off, as shown in FIG. 4d.

Thereafter, the above-mentioned operation is repeated, and the transistor 4,
An alternating current output is generated on the secondary winding N3 side of the output transformer 3 by alternately turning on and off the output transformer ₃ .

Therefore, with such a configuration, the reverse bias voltage immediately after the transistor is turned off can be set high, so that the switching characteristics of the transistor can be stabilized, thereby reducing the switching loss and improving the inverter's performance. This means that a significant improvement in operating efficiency can be expected.

It should be noted that the present invention is not limited to the above-mentioned embodiments, but can be implemented with appropriate modifications without changing the gist.
For example, a resistor 11 may be connected in parallel to the inductor 10 to suppress parasitic vibrations, as shown in FIG. 6, in which the same parts as in FIG. 3 are given the same reference numerals. Further, the DC power source may be obtained by rectifying the AC power source.

As described above, this invention uses a common feedback winding for a pair of transistors in a so-called push-pull type inverter that outputs a sinusoidal resonant voltage, and also connects an inductor in series with the feedback winding. The reverse bias voltage immediately after each transistor is turned off can be increased, and the switching characteristics of the transistor can be improved to improve efficiency.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an example of a conventional inverter device, Fig. 2 is a waveform diagram for explaining the same device,
FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG.
FIG. 5 is a waveform diagram for explaining the same embodiment, FIG. 5 is a circuit diagram for explaining the main part of the same embodiment, and FIG. 6 is a circuit diagram showing another embodiment of the present invention. 1...DC power supply, 2...Constant current reactor, 3
...output transformer, 4,5...transistor,
6, 7...Bias circuit, 8...Capacitor, 9
...Load, 10...Inductor, 11...Resistance.

Claims (1)

[Claims] 1. A DC power source; A pair of transistors connected in parallel to this power source and alternately turned on and off; An output transformer connected to obtain an output according to the on/off operation of the transistors; a resonance capacitor provided in connection with the transformer; a closed circuit that is magnetically coupled to the transformer and provided between the bases of the transistors and includes the bases and emitters of the transistors in series when switching the pair of transistors; a feedback winding that causes an instantaneous current to flow through the feedback winding; and a feedback winding that is connected in series to the feedback winding and generates an electromotive force when the instantaneous current is interrupted, thereby switching one of the pair of transistors from on to off. An inductor that applies a reverse bias voltage to a transistor and applies a forward bias voltage to a transistor switching from off to on. 2. The inverter device according to claim 1, characterized in that a resistor is connected in parallel to the inductor.