JPS60174069A - Bridge inverter circuit - Google Patents

Abstract

PURPOSE:To alleviate a switching loss by flowing a switching current to a semiconductor switch having high switching speed and a main current to a large power semiconductor switch. CONSTITUTION:Transistors 12, 13 having faster switching speed than transistors 2, 3, 4, 5 are connected in parallel with any of transistors 2, 3 (transistor 4, 5) disposed at a diagonal position, the transistors having fast switching speed are operated only at the switching time, a main current is flowed to other transistors to reduce the switching loss and to largely improve the efficiency, thereby reducing the size of a cooling fan and size and weight.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical field to which the invention pertains] The present invention relates to a bridge inverter circuit for converting direct current power to alternating current power of a desired frequency, and more specifically, to a bridge inverter circuit that is highly efficient and compact.

This invention relates to improvements to obtain a lightweight bridge inverter circuit.

[Prior art and its problems]

Generally, in order to obtain an alternating current voltage from a direct current power source, the above-mentioned bridge inverter circuit is used, which generates an alternating current voltage by inverting the polarity of the voltage applied to the load using a semiconductor switch. , semiconductor switches controlled by the output of the drive circuit are connected in a bridge configuration between the DC power source and the load, and the diagonal pairs of semiconductor switches that make up the bridge are alternately turned on and off to generate an AC voltage across the load. I'm letting you do it.

A conventional example of such a bridge inverter circuit is shown in FIG. In FIG. 1, a transistor is used as the semiconductor switch.

The circuit shown in the figure alternately turns on and off a transistor pair consisting of transistors 2 and 3 and a transistor pair consisting of transistors 4 and 5, and alternately applies a DC voltage from a DC power source 1 to both ends of a load 6. This generates an alternating current voltage.

In this type of circuit, when a semiconductor switch is turned on or turned off, there is a period in which voltage and current cross, resulting in switching loss. This switching loss depends on the turn-on or turn-off time of the semiconductor switch.

Add current capacity to semiconductor switches to increase output capacity! When using a semiconductor switch with a large There are problems in that the weight cannot be reduced and the efficiency is low.

In addition, the operating frequency of this type of circuit is limited by the turn-on time, accumulation time, and fall time of the semiconductor switch.
Current large-capacity semiconductor switches do not have good characteristics, and they also have the disadvantage of not being able to operate at high frequencies.

[Purpose of the invention]

The present invention has been made in order to eliminate the problems and drawbacks of the prior art as described above, and therefore, an object of the present invention is to reduce switching loss, make it possible to reduce the size and weight, and also realize high frequency [Summary of the Invention] The main point of the present invention is to provide a bridge inverter circuit that can operate at a high switching speed in parallel with one of the semiconductor switches in each semiconductor switch pair in a bridge inverter circuit. add,
〇〇〇〇〇　Embodiment of the Invention　An embodiment of the present invention will be described with reference to the drawings.

[Figure 2 is a circuit diagram showing an embodiment of the present invention.

In this figure, the same parts as in FIG. 1 are indicated with the same reference numerals or symbols. Further, a case is shown in which a transistor is used as the semiconductor switch.

In FIG. 2, transistors 12 and 13 have a faster switching speed and a higher on-voltage than transistors 3 and 4.

Generally, as the switching speed increases, the on-state voltage tends to increase. The circuit operation of a transistor pair including transistor 2, transistor 3, and transistor 13 will be described.

First, when a drive signal is supplied to the transistor 2 from a drive circuit (not shown), the transistor 2 becomes conductive. After the transistor 2 is fully conductive, when a drive signal is applied to the transistor 13, the voltage of the DC power supply 1 is applied to the load 6. At this time, a transiently increasing current flows through transistor 2 and transistor 13, but since transistor 13, which becomes conductive after the power supply voltage, shares the burden, switching loss, which is the product of current and voltage, mainly occurs in transistor 13. .

When a drive signal is applied to the transistor 3 immediately after the transistor 13 becomes completely conductive, the current flowing through the transistor 13 is transferred to the transistor 3 having a lower on-voltage. From then on,
Power is supplied to the load through a path of DC power supply 1, transistor 2, load 6, and transistor 3.

Next, when cutting off the power supplied from the DC power 11 to the load 6, the transistor 3 is cut off first, and immediately after the current has transferred to the transistor 13, the transistor 13 is cut off, and switching is performed by the transistor 13, so there is a switching loss. is mainly generated in the transistor 13.
After transistor 13 is turned off, transistor 2 is turned off. Since no current flows through transistor 2, no switching loss occurs.

The above is a half-cycle operation. The operation of the next half cycle is transistor 4, transistor 12, transistor 5.
This is done using a transistor pair consisting of.

First, the transistors 5 to which the transistor 12 is not connected in parallel are made conductive. Next, the transistor 12 is turned on and the voltage of the DC power supply 1 is applied to the load 6. A transiently rising current flows through the transistor 12, the load 6, and the transistor 5. Since the switching operation is performed by the transistor 12 which becomes conductive later, switching losses, which are the product of current and voltage, occur mainly in the transistor 12. Immediately after the transistor 12 becomes completely conductive, when a drive signal is applied to the transistor 4, the current flowing through the transistor 12 is transferred to the transistor 4, which has a lower ON voltage 6. This is done through the route of transistor 5. When cutting off the flowing current, as in the previous half cycle, the transistor 4 with the faster switching speed transistor 12 connected in parallel is first cut off, and the current flows through the transistor 4.
Immediately after the current is transferred from the current to the transistor 12, the transistor 12 is cut off, and the current is further switched. After transistor 12 is completely cut off, transistor 5 is cut off and the next half cycle is completed.

In this way, one of the transistors 2 and 3 (transistors 4 and 5) located diagonally is connected to the transistor 2.
, 3, 4.5, switching losses are reduced by connecting transistors with faster switching speeds in parallel, operating the transistors with faster switching speeds only during switching, and allowing the main current to flow through the other transistors.
In addition to greatly improving efficiency, the stepwise fins are also smaller, making it possible to achieve significant reductions in size and weight.

In Figure 2, transistors 12 and 13 with high switching speed are connected in parallel to transistors 3 and 4.
Transistors 2, 5. ) transistor 2.4. ) It is clear that the same effect can be obtained no matter which set of transistors 3 and 5 is connected in parallel with transistors 12 and 13 having a high switching speed.

FIG. 3 shows the drive signal waveforms of each transistor.

In the figure, the drive signal 10 pulse width of transistor 2 is the maximum, and within the range of that pulse width, transistor 13
It will be recognized that the pulse width of the drive signal for the transistor 3 is within the range of the pulse width, and that the pulse width of the drive signal for the transistor 3 is located within the range of the pulse width. As a result, it will be easily understood that conduction is performed in the order of transistors 2 and 13.3, and transistors 3 and 13.2 are turned off in this order.

The same thing can be said about the transistors 5 and 12.4. Figure 4 shows a signal circuit for realizing the drive signal waveform shown in Figure 3. Figure 5 shows the signals of each part in Figure 4. Shows the waveform.

In these figures, the output P of the oscillator 20 is the common trigger output for the monostable multivibrator 21, 22, 23 and the bistable multivibrator 24. Monostable multivibrator 21゜22.23 Each output pulse width l111y T2 t 'ra is TI > T2 > T
← Configure each vibrator so that the relationship shown in 3 is satisfied. The outputs of the monostable multivibrators 22 and 23 are waveform-shaped by integrating circuits 25 and 26, respectively. The time constant R1a cl of the integrating circuit 25 is the time constant R2e c of the integrating circuit 26.
It is set smaller than l, and is used as one input of the next-stage AND circuit having a threshold hold level. By using the outputs Q and Q of the bistable multivibrator 24, which outputs ON and OFF pulses every half cycle, as other inputs of the AND circuit in the next stage, a drive signal waveform as shown in FIG. 5 can be obtained. This will be easily understood.

〔Effect of the invention〕

As explained above, high-power semiconductor switches that flow large currents have a long rise time and fall time, resulting in large losses due to these, resulting in a decrease in efficiency. There was a problem that it was difficult to

Generally, high-voltage, high-power semiconductor switches that switch quickly have a high on-voltage, resulting in large losses due to main current.

Therefore, in the present invention, a semiconductor switch with a fast switching speed is connected in parallel to a high power semiconductor switch, and transient switching is performed by the semiconductor switch with a fast switching speed, and the high power semiconductor switch does not perform switching. The above problem was solved by allowing the main current to flow.

The high-power semiconductor switch used here may have a low on-voltage and a slow switching speed.

In addition, semiconductor switches connected in parallel with high switching speeds only perform transient switching operations and do not allow main current to flow, so it is sufficient to use semiconductor switches with low power dissipation. As for semiconductor switches connected in parallel with a high switching speed, the faster the switching speed, the smaller the loss can be, and a small-capacity semiconductor switch may be used. It goes without saying that FBT, SIT, etc. can also be used as semiconductor switches with high switching speed.

In this way, switching loss can be reduced by flowing the switching current through a semiconductor switch with a high switching speed and the main current through a high-power semiconductor switch, so that the efficiency of the inverter circuit according to the present invention is improved.
Cooling fins are also made smaller. The present invention is particularly effective when applied to highly efficient, compact, and lightweight bridge inverter circuits that perform large-capacity power conversion.

[Brief explanation of drawings]

Figure 1 is a circuit diagram showing a conventional bridge inverter circuit.
Fig. 2 is a circuit diagram showing one embodiment of the present invention, and Fig. 3 is a circuit diagram showing an embodiment of the present invention.
A waveform diagram showing an example of a drive signal for the bridge inverter circuit shown in the figure, FIG. 4 is a circuit diagram showing an example of a signal circuit that generates the drive signal, and FIG. 5 is a waveform diagram showing signal waveforms of each part of FIG. 4. Figure. Description of symbols 1: DC power supply, 2: First transistor, 3: Second transistor, 4...
...Third transistor, 5...Fourth transistor, 6...Load, 12.13...
・Transistors with high switching speed (FIT, SI
T, etc.), 20... Oscillator, 21.22, 23.
...Monostable multivibrator, 24...
・Bistable multivibrator, 25, 26...
Integral circuit representative Patent attorney Akio Namiki Patent attorney Kiyoshi Matsuzaki Figure 1 Figure 2 Figure 1jE3

Claims (1)

[Claims] 1) Connect a load between the first semiconductor switch and the second semiconductor switch and connect the sensing circuit in parallel to the DC power supply,
A third semiconductor switch is provided between a connection point between the first semiconductor switch and the DC power supply and a connection point between the second semiconductor switch and the load, and a third semiconductor switch is connected between the first semiconductor switch and the load. A fourth semiconductor switch is connected between the i reading point and the connection point between the second semiconductor switch and the DC power supply, and the first semiconductor switch is connected between the second semiconductor switch and the DC power supply. a second pair of semiconductor switches;
3 above. In the bridge inverter circuit in which the fourth semiconductor switch pair is alternately turned on and off to apply an alternating current voltage to the negative and negative terminals, the #! 1. either one of the semiconductor switches of lI2 and the third. Either one of the fourth semiconductor switches is connected to the first. Second. Third. Fourth
A high-speed semiconductor switch having a faster switching speed than each semiconductor switch is connected in parallel, and when the semiconductor switch pair is made conductive, the high-speed semiconductor switch is not connected in parallel, the high-speed semiconductor switch, The above-mentioned high-speed semiconductor switches are connected in parallel, and the above-mentioned high-speed semiconductor switches are connected in parallel, and when they are turned off, the above-mentioned high-speed semiconductor switches are connected in parallel. A bridge inverter circuit characterized in that the switches are cut off in the order of the semiconductor switches that are not connected in parallel.