JPS6120877Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a gate firing circuit for a thyristor.

FIG. 1 is a diagram showing a conventional thyristor firing circuit, in which the primary winding 2 of a pulse transformer 1 has a terminal 10.
A gate pulse signal is applied from and 11. The voltage induced in the secondary winding 3 is applied to the resistor 5, the diode 7, the gate electrode 12 of the thyristor 9, and the cathode electrode 1.
A current is passed through the thyristor 3 to generate a firing signal for the thyristor 9. Diodes 4 and 6 are used to reset the magnetic flux of pulse transformer 1, and capacitor 8 is a noise filter. In addition, the diode 8 is connected to the pulse transformer 1 by the noise voltage from the thyristor 9 side.
This is to prevent them from entering the next side. In such a conventional circuit system, when the ignition pulse voltage is not output, the gate pole 1 of the thyristor 9
2. The voltage between the cathode 13 is zero, and the noise voltage from the main circuit of the thyristor 9 despite the presence of the noise filter capacitor 8,
Another disadvantage is that false ignition is likely to occur due to noise voltage from the primary side of the pulse transformer.

This invention eliminates the above-mentioned conventional drawbacks, and provides a thyristor gate firing circuit that constantly applies a negative bias voltage to the gate electrode of the thyristor and operates reliably without malfunctioning due to external noise voltage. It is something.

A description will be given below based on an embodiment shown in FIG.

FIG. 2 is an electrical circuit diagram showing the gate ignition circuit of the present invention, and the same reference numerals as in FIG. 1 indicate the same parts. In the figure, a pulse transformer 14 separate from the pulse transformer 1 is provided, and one end of a primary winding 15 is connected to a power source, and the other end is connected to a collector electrode of a transistor 18 through a power source limiting resistor 17. When a base drive signal having a constant period as shown in the figure is applied to the base pole 19 of the transistor 18, the transistor 18 is repeatedly turned on and off by a switching action. This means that a voltage is applied to the primary winding 15 of the pulse transformer 14, and naturally a voltage is induced in the secondary winding 16. The induced voltage charges the capacitor 21 through the diode 20 according to the polarity of the pulse transformer winding indicated by the black mark in the diagram as + and - in the diagram. The diode 20 is provided to prevent this charged voltage from discharging. Since the voltage charged in the capacitor 21 is discharged through the diodes 24 and 23 and the resistor 22, a current always flows through the diode 24, and the current flows across the diode 24, that is, the gate of the thyristor 9, and the cathode electrodes 12 and 13.
A negative bias voltage will be applied between them.
Since this value is much smaller than the signal voltage from the pulse transformer 1 side, the thyristor 9 fires when the firing signal comes, and when the firing signal does not come, the gate pole 12 of the thyristor 9 is always negatively biased. are doing. By increasing the pulse frequency on the primary side of the pulse transformer 14 for the above-mentioned negative bias signal, the pulse transformer 14 can be made extremely compact with a small iron core and a small number of windings. Since the base signal is only turned on, the overall power can be made very small.

As described above, according to the present invention, it is possible to obtain a thyristor gate ignition circuit that has low power consumption, has small rated power specifications of surrounding electrical components, and does not malfunction due to external noise.

[Brief explanation of the drawing]

FIG. 1 is an electric circuit diagram showing a conventional thyristor gate ignition circuit, and FIG. 2 is an electric circuit diagram showing an embodiment of the present invention. In the figure, 1 and 14 are pulse transformers, 9 is a thyristor, 12 is a gate electrode, 18 is a transistor, 1
9 is a base electrode, 21 is a capacitor, 20, 2
4 and 23 are diodes. In addition, the same numbers in the figures indicate the same or corresponding parts.

Claims (1)

[Scope of utility model registration request] In a thyristor ignition circuit that controls the ignition of the thyristor by applying an ignition pulse to the gate of the thyristor via a first transformer, a high-frequency modulated unipolar pulse signal is inputted via a switch element. a second transformer to which pulsed power is supplied; a first diode for half-wave rectification of the pulsed power introduced through the second transformer; and a first diode and the second transformer. a capacitor provided in a closed circuit including the transformer and charged by the output of the second transformer; and a capacitor provided in the discharge circuit of this capacitor in the forward direction, and a connection point between the capacitor and the anode is connected to the cathode of the thyristor. , a second diode whose connection point between the capacitor and the cathode is connected to the gate of the thyristor, and a forward bias voltage of the second diode is applied as a reverse bias between the gate and cathode of the thyristor. A thyristor ignition circuit featuring: