JPS6315675A - Transistor inverter device - Google Patents

Abstract

PURPOSE:To suppress increase of switch loss of a main circuit transistor, by a method wherein when current at primary side of a rectifying and smoothing circuit becomes over a prescribed value, reverse bias amount is increased at turning-off of the main circuit transistor and at OFF-state. CONSTITUTION:A main circuit transistor 2 constitutes main circuit of a transistor inverter. Primary current of a rectifying and smoothing circuit 1 is detected by a current detecting circuit 26, and the detected output is supplied to a power conversion circuit 27 for reverse bias. when the primary current of the rectifying and smoothing circuit 1 becomes over a prescribed value, reverse bias amount between base . emitter is increased at turning-off of the main circuit transistor 2 and OFF-state by the power conversion circuit 27 for reverse bias. Thereby increase of the turning-off time of the main circuit transistor 2 is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of the Invention The present invention relates to a transistor inverter device for controlling the rotational speed of an electric motor.

2. Description of the Related Art In recent years, transistor inverter devices have come into widespread use in order to vary the rotational speed of electric motors and reduce or increase the capacity of various devices.

An example of the above-mentioned transistor inverter device will be described below with reference to the drawings.

FIG. 3 is a schematic configuration diagram of a transistor inverter device, and FIG. 4 is a circuit diagram of a base drive circuit of a conventional transistor inverter device. In FIG. 3, reference numeral 1 denotes a rectifying and smoothing circuit, which converts an AC power supply into a DC power supply. 2 is a main circuit transistor group, which constitutes the main circuit of the transistor inverter device. Reference numeral 3 denotes main circuit transistors, six of which are connected in series and parallel to form the main circuit of the transistor inverter device. 4 is a motor connected to the output of the main circuit transistor 3; 6 is a power supply circuit that converts AC commercial power into DC for control.

6 is a frequency setting section. Reference numeral 7 denotes a control section that generates a waveform of a set frequency based on the signals from the frequency setting section. Reference numeral 8 denotes a base drive section, which transmits the waveform generated by the control section 7 to the main circuit transistor group 2. A base drive circuit 9 operates the main circuit transistor 3. In FIG. 4, a photocoupler 10 transmits the output of the control section 7 to the base drive circuit 9. 1
1 is e)LED-, 12 is a phototransistor,
It constitutes the photocoupler 10. 13 is a power supply; C14, which supplies voltage to the base drive circuit 9, is a first NPN transistor; the base thereof is a resistor 15 connected in series with the emitter of the phototransistor 12;
．． 16, and the collector is connected to the first resistor 17
It is connected to the power source 13 via. Reference numeral 18 denotes a second PNPN upper type transistor whose base is connected to the collector of the phototransistor 12 and connected to the power supply 13 via a resistor 19.

2o is a third NPN type transistor, the base is connected to the collector of the first NPN type transistor, the collector is connected to the collector of the second PNPN upper type transistor via a second resistor 21, and The base of the main circuit transistor 3 is connected. 22 is a group of diodes connected in series, and a capacitor 23
are connected in parallel, connected to the power supply 13 via the third resistor 24, and connected to the emitter of the main circuit transistor 3. 25 is a base drive signal circuit.

The operation of the transistor inverter device configured as described above will be described below.

When the output of the control section 7 is turned on, the photocoupler 1o
The photoLED 11 emits light, and the phototransistor 12
turns on. At this time, the second PNPN upper type resistor 18
When the base current flows and turns on, the first NP
The base current of the N-type transistor 14 also flows through the first NPN
type transistor turns on. Therefore, the current flowing through the resistor 17 flows from the collector to the emitter of the first NPN transistor and does not flow through the third NPN transistor 2Q, so the third NPN transistor 20 is turned off. That is, when the output of the control section 7 is turned on, the second PNPN transistor 18 is turned on and the third NPN transistor 20 is turned off.

Therefore, a current limited by the second resistor 21 flows into the base of the main circuit transistor 3 and turns on the main circuit transistor 3.

Next, when the output of the control section 7 changes from on to off, the phototransistor 12 is turned off, the second PNPN transistor 18 is turned off, and the first NPN transistor 14 is turned off. The third NPN transistor 2o is turned on. Here, the diode group 22
The base and emitter of the main circuit transistor 3 are reverse biased by the capacitor 23, and a current flows that draws carriers in the base from the base, so that the main circuit transistor 3 rapidly changes from on to off.

When this drawing current disappears, the main circuit transistor 3 is stabilized in an OFF state.

Problems to be Solved by the Invention However, in the above configuration, the amount of reverse bias between the base and emitter of the main circuit transistor 3 is constant, and when the collector current of the main circuit transistor 3 increases, the main circuit When the transistor 3 is turned off, the number of carriers accumulated in the base increases, resulting in a longer turn-off time.As a result, the switching loss of the main circuit transistor 3 increases, resulting in a decrease in efficiency. .

In view of the above problems, the present invention detects the current on the primary side of the rectifying and smoothing circuit and reverse biases it even when the collector current of the main circuit transistor increases and the number of carriers accumulated in the base at turn-off increases. To provide a transistor inverter device that can suppress an increase in the turn-off time of the main circuit transistor and prevent a decrease in efficiency by increasing the amount of the main circuit transistor.

Means for Solving the Problems In order to solve the above problems, the transistor inverter device of the present invention includes a current detection circuit that detects the current on the primary side of the rectifying and smoothing circuit, and a current detection circuit that detects the current on the primary side of the rectifying and smoothing circuit, and when the main circuit transistor is turned off and off. a reverse bias power source that reverse biases between the base and emitter of the main circuit transistor when the main circuit transistor is in the state;
The reverse bias power supply conversion circuit changes the voltage value of the reverse bias power supply according to a signal from the current detection circuit.

According to the present invention, the current detection circuit detects the current on the primary side of the rectifying and smoothing circuit with the above-described configuration, and when the collector current of the main circuit transistor increases, a signal from the current detection circuit causes the current detection circuit to detect the current on the primary side of the rectifying and smoothing circuit. increases the amount of reverse bias between the base and emitter when the main circuit transistor is turned off and in the off state, suppressing an increase in the turn-off time and suppressing a decrease in efficiency.

Embodiment Hereinafter, a transistor inverter device according to an embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a configuration diagram of a base drive circuit of a transistor inverter device according to an embodiment of the present invention, and FIG. 2 shows a circuit diagram of a reverse bias power conversion circuit according to an embodiment of the present invention. It is something. In FIG. 1, 1 is a rectifier and smoothing circuit, 3 is a main circuit transistor, 13 is a power supply, 18 is a second PNP type transistor, and 20 is a third transistor.
21 is a second resistor, 23 is a capacitor, 24 is a third resistor, and 25 is a base drive signal circuit. Since the above structure is the same as that shown in FIG. 4, detailed explanation will be omitted. . 2θ is a current detection circuit that detects the current on the primary side of the current smoothing circuit 1 and generates an "L" signal if it is below a specified current value, and an "H" signal if it is above the specified current value. It is. Reference numeral 27 denotes a power conversion circuit for reverse bias, which controls the amount of reverse bias between the base and emitter of the main circuit transistor 3 when it is turned off and when it is in the off state, based on the signal from the current detection circuit 26. 23 are connected in parallel, and the terminal a is connected to the third resistor 24, the terminal is also connected to the base drive signal circuit 25, and the terminal C is connected to the collector current detection circuit . 28 is a comparator, which is the reference power supply 2
Compare the reference voltage of 9 and the signal input from terminal C,
If the signal input from terminal C is larger, set it to “H”.
If it is smaller, "L" is output. 3o is a fourth NPN type transistor whose base is connected to the output of the comparator 28, which turns on when the output of the comparator 28 is "H" and turns off when the output of the comparator 28 is "L". 31 is a relay, and the fourth NPN transistor 3o is OFF.
If so, the NC terminal and terminal a are connected, and the fourth N
When the PN type transistor 3o is ON, it operates so that the NC terminal and the terminal a are connected.

32 is the first reverse bias power supply, and the positive side is NC
The negative side of the terminal is connected to the terminal. Reference numeral 33 denotes a second reverse bias power source, the positive side of which is connected to the No terminal, and the negative side of the second reverse bias power source 33 connected to the terminal No. 33, which has a voltage value larger than that of the first reverse bias power source 32.

The operation of the transistor inverter device configured as described above will be explained below with reference to FIGS. 1 and 2.

The current on the primary side of the current smoothing circuit 1 is detected by a current detection circuit 26.
If the current is below the specified current value, an "L" signal is output, and if the current is above the specified current value, an "H" signal is output from the terminal cK ratio of the reverse bias power conversion circuit 27. First, when the input signal of terminal C is "L", the comparator 28 is "L".
The fourth NPN transistor 3o is in an off state, and the terminal a is connected to the NC terminal. Therefore, when the main circuit transistor 3 is turned off or in the off state, the first reverse bias power supply 32
The base and emitter are reverse biased. Next, terminal C
When the input signal is "H", the comparator 28 outputs "H", the fourth NPN transistor 30 is in the ON state, and the terminal a is connected to the No terminal. Therefore, the second reverse bias power supply 33 applies a reverse bias between the base and the emitter when the main circuit transistor 3 is turned off or in the off state. Since the voltage value of the second reverse bias power supply 33 is larger than that of the first reverse bias power supply 32, when the input signal of the terminal C is "H", that is, on the primary side of the rectification and smoothing circuit. When the current is greater than the specified current value, the amount of reverse bias between the base and emitter of the main circuit transistor 3 increases when it is turned off and when it is in the off state.

As described above, according to this embodiment, the current detection circuit that detects the current on the primary side of the rectifying and smoothing circuit reverses the current detection circuit between the base and emitter of the main circuit transistor when the main circuit transistor is turned off or in the off state. By providing a reverse bias power supply for biasing and a reverse bias power conversion circuit that changes the voltage value of the reverse bias power supply according to a signal from the current detection circuit, the current on the primary side of the rectifying and smoothing circuit is regulated. If the current exceeds the current value, the amount of reverse bias between the base and emitter is increased when the main circuit transistor is turned off and in the off state, thereby suppressing an increase in the turn-off time, thereby suppressing an increase in the switching loss of the main circuit transistor. In addition, an increase in heat dissipation from the main circuit transistor can be suppressed, and the heat sink can be made smaller. In addition, by increasing the amount of reverse bias between the base and emitter of the main circuit transistor, the terminal voltage between the collector and emitter increases, which approaches the withstand voltage between the collector and base, resulting in surge voltage and steep This also has the effect of preventing the main circuit transistor from malfunctioning with respect to dv/dt.

In addition, since the current on the primary side of the rectifier and smoothing circuit is detected as the detection point, it is less affected by high frequency noise generated by the main circuit transistor than when detecting the secondary side current. , This has the effect of reducing the occurrence of malfunctions.

Note that the present invention is not limited to this embodiment, but is effective in changing the reverse bias voltage without departing from the gist of the present invention.

Effects of the Invention As described above, the present invention provides a main circuit transistor that constitutes the main circuit of a transistor inverter, and a current detection circuit that detects a current on the primary side of a rectifying and smoothing circuit.

A reverse bias power source that reverse biases between the base and emitter of the main circuit transistor when the main circuit transistor is turned off or in an off state, and a voltage value of the reverse bias power source is changed by a signal from the current detection circuit. By providing a reverse bias power conversion circuit,
If the current on the primary side of the rectifying and smoothing circuit exceeds the specified value,
By increasing the amount of reverse bias between the base and emitter when the main circuit transistor is turned off and in the off state, and suppressing an increase in turn-off time, an increase in switch loss of the main circuit transistor is suppressed and a decrease in efficiency is suppressed. Moreover, since the primary side current of the rectifying and smoothing circuit is detected as the detection point, the effect of high frequency noise generated in the main circuit transistor is small, and the malfunction occurrence rate is low.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a base drive circuit of a transistor inverter according to an embodiment of the present invention, FIG. 2 is a circuit diagram of a reverse bias power conversion circuit of FIG. 1, and FIG. 3 is a schematic configuration of a transistor inverter device. 4 are circuit diagrams of a base drive circuit of a conventional transistor inverter device. 1... Rectifier smoothing circuit, 3... Main circuit transistor, 26... Current detection circuit, 27...
...Reverse bias power conversion circuit, 32...
First reverse bias power supply, 33...Second reverse bias power supply. Name of agent: Patent attorney Toshio Nakao and 1 other person/-
11 Dashi Kuhei; Yoirono Announcement 2--1 Main circuit transistor Z6-19 Detection ci circuit d.--Reverse bias computer G: Horizontal circuit 1 Figure 1
J? 7-Tang bias power supply; power source for reverse bias; 3z-Brown I reverse bias power supply;

Claims (1)

[Claims] A main circuit transistor constituting a main circuit of a transistor inverter, a rectifier and smoothing circuit that supplies power to the main circuit transistor, a current detection circuit that detects a current on the primary side of the rectifier and smoother circuit, and the main circuit transistor. a reverse bias power supply that reverse biases between the base and emitter of the main circuit transistor during turn-off and in the off state; and a reverse bias power supply that changes the voltage value of the reverse bias power supply according to a signal from the collector current detection circuit. A transistor inverter device comprising a conversion circuit.