JPH062994U - Inverter circuit - Google Patents

Abstract

(57) [Summary] (Modified) [Purpose] In a full-bridge inverter circuit that supplies a gate signal by a pulse transformer, a fly generated on the secondary side of the pulse transformer when the gate signal is extinguished. The purpose is to prevent the switch element from being erroneously ignited by the back voltage. [Constitution] When the gate signal of the pulse transformer is in the idle period, a circuit for stopping the supply of the gate signal from the pulse transformer is provided through a photocoupler composed of a power source different from the full bridge inverter power source. Inverter circuit.

Description

[Detailed description of the device]

[0001]

[Field of Invention]

 The present invention relates to an ignition signal of a switch element of an inverter circuit.

[0002]

[Prior art]

 FIG. 1 shows a conventional full-bridge inverter circuit. E1 is a DC power source, Q1, Q2, Q3, and Q4 are semiconductor switching elements, D1, D2, D3, and D4 are feedback diodes, L is a reactor, and C is a capacitor. , PT1, PT2, PT3, PT4 are pulse transformers, D5, D6, D7, D8 are diodes, R1, R2, R3, R4, R5, R6, R7, R8, R9, R10, R11, R12 are It is resistance. Also, A, B, C and D in the figure indicate the input signal of the primary winding of each pulse transformer.

Next, the operation will be described. PWM control is performed such that when DC voltage E1 is received and switch elements Q1 and Q4 are closed, switch elements Q2 and Q3 are open, and switch elements Q2 and Q3 are closed, switch elements Q1 and Q4 are open. . Therefore, when the switch element Q4 is closed and Q1 (2) is closed, current flows through the path of E1 + 〓Q1〓C〓L〓Q4〓E1−, and when switch element Q2 is closed and Q3 is open, E1 + 〓 Current flows through the route of Q3〓L〓C〓Q2〓E1－.

In this way, the inverter circuit performs the PWM operation and outputs the sine wave AC through the filter composed of the reactor and the capacitor C in the output stage.

However, in the case of this circuit configuration, when the signals of A, B, C, and D are stopped, the flyback voltage is generated at the same time as the stop signal on the secondary side of each pulse transformer, which is the firing signal. As a result, one arm may erroneously fire at the same time, which may lead to the destruction of the switching element in the worst case.

FIG. 3 shows a false firing signal applied to the switching element at that time. Similarly, when the waveform of a in the figure is applied to the respective switching elements between one arm, the series switching elements are simultaneously turned on, and at worst, the switching elements are destroyed.

[0007]

[The purpose of the device]

 The present invention aims to eliminate the flyback voltage generated on the secondary side when the primary side signals of the signals A, B, C and D stop, thereby destroying the switching element. The purpose is to prevent.

[0008]

【Example】

 FIG. 2 shows an embodiment of the present invention. The same symbols as those in FIG. 1 indicate the same operation. Other than that, Q5, Q6, Q7, Q8 and Q9 are transistors, D9, D10, D11 and D12 are diodes, and C1, C2, C3 and C4 are capacitors and R13. , R14, R15 and R16 are resistors, and PC1, PC2, PC3 and PC4 are photocouplers. E2 is a power source for the control unit. (3)

The inverter drive operation is the same as in FIG. 1, and PWM operation is performed to output a sine wave AC through a filter composed of the reactor L and the capacitor C in the output stage.

Further, the phototransistors on the secondary side of the photocouplers PC1, PC2, PC3, and PC4 are normally kept ON, and the transistors 2y, Q5, Q6, Q7, and Q8 are OFF. When the primary side signals of the pulse transformers of A, B, C and D stop in this state, the stop signal is received so that the transistor Q9 in the separate power source E2 is turned off, whereby the photocoupler PC1 , PC2, PC3, PC4 primary side LEDs are extinguished, photocouplers PC1, PC2, PC3, PC4 secondary side phototransistors are simultaneously turned off, and transistors Q5, Q6, Q7, Q8 are turned on. As a result, the flyback voltage applied to each gate can be erased, and it is possible to prevent one arm from turning on at the same time.

Further, by combining the transistors Q5, Q6, Q7, Q8 and the photocouplers PC1, PC2, PC3, PC4, even if the drive current of the photocoupler varies a little, the transistors Q5, Q6, Q7, Q8 amplify Its influence can be minimized and a complete stop signal can be given to the gate.

FIG. 4 is an ignition signal of the switching device according to the present invention. Since the Q5, Q6, Q7, and Q8 transistors are turned on at the time of stoppage, the false firing signal due to the flyback voltage is eliminated, so that the simultaneous firing due to the false firing signal between one arm is prevented, Damage due to simultaneous switching on of switching elements is prevented.

[0013]

[Explanation of effect]

 (4) According to the present invention, in the pulse transformer drive type inverter of the full bridge configuration, one arm is turned on at the same time by the false firing signal generated at the time of stop, and the switching element is destroyed. It is possible to provide a highly reliable pulse transformer drive type inverter.

[Brief description of drawings]

FIG. 1 is a conventional full-bridge inverter circuit.

FIG. 2 is a full-bridge type inverter circuit of the present invention.

FIG. 3 is an ignition signal applied to a switching element of a conventional circuit.

FIG. 4 is an ignition signal applied to a switching device improved by the present invention.

[Explanation of symbols]

 E1, E2 DC power supply Q1, Q2, Q3, Q4 Semiconductor switching element Q5, Q6, Q7, Q8 Transistor D1, D2, D3, D4 Feedback diode D9, D10, D11, D12 Diode R1 to R16 Resistor C1 , C2, C3, C4 Capacitor PC1, PC2, PC3, PC4 Photocoupler PT1, PT2, PT3, PT4 Pulse transformer L reactor C Smoothing capacitor A, B, C, D Input signal of pulse transformer

Claims (1)

[Scope of utility model registration request] 1. A pulse transformer comprising a pair of individual insulated windings is used for each gate circuit of two semiconductor switching elements connected in series in the forward direction between the power supplies of a full-bridge inverter circuit. During the rest period of the gate signal of the pulse transformer, the light emitting element on the primary side of the photocoupler applied to a power source different from the full bridge inverter power source extinguishes, and the secondary side of the photocoupler is turned off. Transistor is off
By doing so, an inverter circuit having a circuit for short-circuiting the secondary output of the pulse transformer with low impedance and stopping the gate signal to the semiconductor switch element.