JPS6237072A - Protective circuit for inverter - Google Patents

Abstract

PURPOSE:To prevent the states of the simultaneous conduction of switching elements, and to improve reliability by nullifying a signal from the other swtiching element when one signal of signals alternately bringing the switching elements to a conductive state is inputted in the signals. CONSTITUTION:A half-bridge type inverter circuit is constituted of a transformer 1, transistors 4, 6 for a switching element, a DC power supply 5 and capacitors 8, 9, the transistors 4, 6 are each switched and controlled by conductive signals d1, d2 through transformers 12, 15, etc., and AC voltage Va is outputted from a secondary winding 16 for the transformer 1. Diodes 17, 18 are fitted as control means at that time. Accordingly, when the conductive signal d1(d2) is inputted and one transistor 4(6) is set under a conductive state, possibility in which the other transistor 6(4) is brought to the conductive state can be prevented because the transistors are clamped by diodes 17, 18 even when disturbance signals are overlapped from the outside.

Description

[Detailed Description of the Invention] [Summary] In a pre-Fuji type inverter, when a conduction signal that brings one switching element into a conductive state is input, a means for preventing a conduction signal from being input to the other switching element is provided. By providing this, it is possible to prevent both switching elements from becoming conductive at the same time and causing an accident.

[Industrial application field]

The present invention relates to an inverter protection circuit that can prevent accidents even when a disturbance signal is input to the inverter circuit.

゛Currently, inverters that generate AC voltage from a DC power supply are half-bridge or full-bridge systems, which reverse the polarity of the DC power supply connected to the primary winding of the transformer at predetermined intervals and output AC voltage to the secondary winding. has been widely adopted.

In such an inverter circuit, if the switching element that connects the bipolar terminals of the DC power source to the primary #@ line of the transformer malfunctions, the DC power source will be short-circuited, causing a major accident such as damage to the switching element.

Therefore, there is a strong demand for a means to prevent malfunctions of such switching elements as much as possible.

[Conventional technology]

FIG. 3 is a diagram showing an example of a conventional half-bridge type inverter circuit, and FIG. 4 is a diagram illustrating various signal waveforms in FIG. 3.

In FIG. 3, the terminal 3 of the primary winding 2 of the transformer 1 is connected to the positive terminal (+) of the DC power source 5 via the transistor 4, and to the negative terminal (-) of the DC power source 5 via the transistor 6. ), and terminal 7 is connected to capacitor 8
It is connected to the positive polarity terminal (+) through the capacitor 9, and to the negative polarity terminal (-) through the capacitor 9. As a result, DC power supply 5
Terminal voltage ■4 is divided by capacitors 8 and 9 into DC voltages Vdl and ■4□.

When the conduction signal dl (see FIG. 4), which becomes logic "1" at a predetermined period, is input to the input terminal 10, the transistor 11 becomes conductive in synchronization with the conduction signal d, and the transistor 4 is energized in synchronization with the conductive signal d.

The energized transistor 4 becomes conductive and the transformer 1
A DC voltage V 41 is applied to the primary winding 2 of the terminal 3.
An intermittent current ■ flows from the terminal 7 toward the terminal 7.

Similarly, when the conductive signal d2 (see FIG. 4) which becomes logic "1" alternately with the conductive signal d1 is input to the input terminal 13,
In the same process as described above, transistors 14 and 6 become conductive in synchronization with conduction signal d2, DC voltage Vd2 is applied to primary winding 2 of transformer 1, and voltage from terminal 7 to terminal 3 is applied to primary winding 2 of transformer 1.
An intermittent current rT□ flows toward.

As a result, in the secondary winding 16 of the transformer l, an alternating current voltage (1) having the same period as the conductive signals d and d2 is generated.

Note that as shown in FIG. 4, the conductive signals d and d2 are designed to ensure that only one of them is logic "1"; however, if the conductive signal d or d2 receives a disturbance signal as shown in FIG. When dX is superimposed due to power supply noise, inductive interference, etc., transistors 11 and 14, and therefore transistors 4 and 6, become conductive at the same time, shorting the terminal voltage V of DC power supply 5.

As a result, transistors 4 and 6 are damaged, and the DC power supply 5
A major accident may occur, such as the fuse installed in the machine blowing out or the breaker shutting off.

[Problem that the invention seeks to solve]

As is clear from the above explanation, in conventional inverter circuits, when the disturbance signal dx is superimposed on the conduction signal d or d2, the transistors 4 and 6 become conductive at the same time, which may cause a major accident in the inverter. .

[Means for solving problems]

FIG. 1 is a diagram showing the principle of the present invention.

In FIG. 1, DC voltages v4 and 4 with different polarities are applied to the primary winding 101 of the transformer 100 through switching elements 201 and 202 which are alternately turned on, and the secondary winding t4
[In an inverter circuit that outputs an AC voltage to 102, when a signal d+ (dz) that makes one switching element 201 (202) conductive is input, the other switching element 202 (201) is made conductive. signal dz(d+)
A control means 300 is provided for disabling the.

[Effect]

That is, according to the present invention, signals d and d2 are prevented from becoming valid at the same time, and switching elements 201 and 202 are prevented from becoming conductive at the same time, thereby preventing an accident from occurring in the inverter circuit.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a diagram showing a half-bridge inverter circuit according to an embodiment of the present invention. Note that the same reference numerals indicate the same objects throughout the figures. Further, various signal waveforms are as shown in FIG.

In FIG. 2, diodes 17 and 18 are provided as control means 300.

In FIG. 2, when a conductive signal d, as shown in FIG. 4 (see FIG. 4) is input to the input terminal 10, the transistor 1
1 and 4 become conductive in synchronization with the conduction signal d1,
Similarly to the above, intermittent current air flows through the primary winding 2 of the transformer 1.

Note that when the transistor 11 becomes conductive, the base-emitter voltage of the transistor 14 is clamped to the collector-emitter voltage of the transistor 11 by the diode 18. In this state, even if the disturbance signal dX is input from the input terminal 13, the transistor 14 is prevented from being set to a conductive state. Therefore, in a state where transistor 4 is set to be conductive, transistor 6 will not be further rendered conductive.

Similarly, when the conduction signal d2 is input to the input terminal 13 and the transistor 14 becomes conductive, the voltage between the base and emitter of the transistor 11 is changed by the diode 17 between the collector and emitter of the transistor 14, as described above. The disturbance signal dX is clamped to the voltage at the input terminal 10.
Even if an input signal is input from , transistor 11 is prevented from being set to a conductive state, and in a state where transistor 6 is set to a conductive state, transistor 4 is not further set to a conductive state.

As is clear from the above description, according to this embodiment, even when the conductive signal d or d2 is input and the disturbance signal dX is superimposed with the transistor 4 or 6 set to the conductive state, Transistors 6 or 4 are prevented from becoming conductive, and accidents such as damage to transistors 4 and 6 are prevented from occurring.

Note that FIG. 2 is only one embodiment of the present invention, and for example, the inverter circuit to which the present invention is applied is not limited to a half-bridge type, and the effects of the present invention can be obtained even in the case of a full-bridge type. remains unchanged.

〔Effect of the invention〕

As described above, according to the present invention, in the inverter circuit,
Switching and closing elements are prevented from becoming conductive at the same time, and accidents such as damage to switching elements, blowing of fuses provided in the DC power supply, or tripping of breakers are prevented, and the reliability of the inverter circuit is improved. .

[Brief explanation of the drawing]

FIG. 1 is a diagram showing the principle of the present invention, FIG. 2 is a diagram showing a half-bridge type inverter circuit according to an embodiment of the present invention,
FIG. 3 is a diagram showing an example of a conventional half-bridge type inverter circuit, and FIG. 4 is a diagram illustrating various signal waveforms in FIG. 3.

Claims (1)

[Claims] Direct current voltages (V_d_1, V_d_2) with different polarities are applied to the primary winding (101) of the transformer (100) via switching elements (201, 202) that are alternately turned on and off,
In an inverter circuit that outputs an alternating current voltage to a secondary winding (102), when a signal (d_1/d_2) that makes one of the switching elements (201/202) conductive is input, the other switching element (201/202) becomes conductive. 202/201) is provided with a control means (300) for disabling a signal (d_2/d_1) that turns on a signal (d_2/d_1).