JPH0728687Y2 - Protection circuit for magnetron modulation circuit - Google Patents

Description

[Detailed description of the device] [Industrial applications]

The present invention relates to a protection circuit for a modulation circuit of a pulse magnetron used in a radar device.

[Prior art]

Magnetrons are classified into continuous wave magnetrons for heating and pulsed magnetrons for radar. In continuous wave magnetrons used for microwave heating including microwave ovens, etc., depending on the load conditions, the rate at which electrons generated from the cathode return to the cathode without reaching the anode becomes high, which causes the temperature of the cathode to rise. Has a problem that it is abnormally elevated and is likely to deteriorate. To that end, there is a technology to protect the magnetron by monitoring the temperature of the cathode.
No. 49-1522. In addition, the anode current of the magnetron is also monitored to detect abnormal operation of the magnetron. Both technologies are technologies for detecting various abnormal states on the assumption that the heater circuit of the magnetron is normal, and it is not possible to directly detect the abnormality of the heater circuit of the magnetron itself. Further, in the continuous wave magnetron, it is not particularly important to monitor the heater breakage because the heater can be operated even after the heater breaks once it is started. Despite the situation of such a continuous wave magnetron, there is no technology for monitoring the burnout of the heater. Therefore, the modulation circuit of the conventional pulsed magnetron for radar has no operation for no-load operation at the time of magnetron failure. When the heater of the magnetron is in a protection state and is broken due to its life, etc., the anode current does not flow to the magnetron and the output circuit of the modulator becomes unloaded. An abnormally high voltage that is several times higher may occur, causing a circuit burnout accident due to dielectric breakdown. Therefore, the output circuit of the modulator becomes unloaded due to the failure of the magnetron as described above, and the insulation of the pulse transformer and the secondary circuit of the pulse transformer is prevented so that dielectric breakdown does not occur even if an abnormally high voltage occurs. The performance was enhanced more than necessary.

[Problems to be solved by the device]

However, with this method, there is no guarantee that the dielectric breakdown accident during no-load operation can be completely prevented, and also the miniaturization of the circuit is hindered. Therefore, in the present invention, it is an object to realize a compact circuit configuration capable of completely preventing a dielectric breakdown accident during no-load operation.

[Means for Solving the Problems]

In the present invention, in the protection circuit of the modulation circuit of the pulse magnetron, the heater current monitoring means for outputting an alarm signal when the heater current value of the magnetron is a predetermined value or less, and the high voltage applied to the magnetron by the alarm signal. A means of providing a high voltage interruption means for interruption is taken.

[Action]

In the protection circuit of the magnetron modulation circuit according to the present application, when the heater current value of the magnetron is less than or equal to a predetermined value,
Since the warning signal is output from the heater current monitoring means, the high voltage cutoff means cuts off the high voltage applied to the magnetron according to the warning signal.

【Example】

Hereinafter, a protection circuit for a magnetron modulation circuit according to the present invention will be described in detail with reference to the drawings. In the drawing, 1 is a magnetron, 2 is a modulation circuit power supply, 3 is a thyristor (FET) for controlling the supply of high voltage, 4 is a heater current of the magnetron 1 is monitored, and ON when a predetermined heater current is flowing. Is a detection circuit that outputs a heater signal a that is turned off when it does not flow, 5 is a trigger amplification circuit, 6 is a heater power supply, 7 is a pulse transformer, 8 is a pulse forming circuit, 9 is a charging coil, and 10 is a holding diode. . Here, a portion including the thyristor (FET) 3, the pulse transformer 7, the pulse forming circuit 8, the charging coil 9, and the holding diode 10 is a modulation circuit for supplying a high voltage to the magnetron 1. The thyristor (FET) 3, the detection circuit 4, and the trigger amplification circuit 5 constitute a protection circuit. An electric current is supplied to the heater of the magnetron 1 from the heater power supply 6 through the detection circuit 4 and the secondary winding of the pulse transformer 7. At this time, the heater signal a from the detection circuit 4 is turned on, and the trigger amplification circuit 5 is in an operable state by the heater signal a. Here, when the trigger pulse b is input, a gate open signal c is output from the trigger amplifier circuit 5, the thyristor (FET) 3 is turned on, and the charge of the pulse forming circuit 8 is on the primary side of the pulse transformer 7. And a high voltage pulse having a turns ratio multiplied by 2 is supplied to the magnetron 1 to operate the magnetron 1 and a modulation signal (pulse radio wave) is output. At the time of this discharge, the charging coil 9 has a sufficiently large impedance and separates the modulation circuit power supply 2 from the pulse forming circuit 8 and the pulse transformer 7. The holding diode 10 is for holding the charging voltage during charging. However, when the heater is disconnected, the heater current does not flow, so the heater signal a from the detection circuit 4 is turned off.
Becomes Therefore, the trigger amplification circuit 5 becomes inoperable, so that even if the trigger pulse b is input, the gate opening signal c is not output from the trigger amplification circuit 5, the thyristor (FET) 3 is kept OFF, and pulse formation is performed. The charge of the circuit 8 is not discharged through the primary side of the pulse transformer 7. Therefore, no abnormal high voltage is generated on the secondary side of the pulse transformer 7. Therefore, dielectric breakdown does not occur. Even if the detection circuit 4 detects the change in the heater current due to the change in the voltage drop in the resistor having the low resistance value, the change in the heater current is detected by the current transformer CT or the photocoupler. May be.

【effect】

According to the protection circuit of the magnetron modulation circuit according to the present application, even if the heater of the magnetron is broken, the high voltage applied to the magnetron is cut off to prevent the abnormal high voltage from being generated, so that the insulation breakdown of the circuit occurs. do not do.
Therefore, the insulation performance of the pulse transformer and the secondary side circuit of the pulse transformer can be minimized, so that the magnetron modulation circuit having high reliability can be realized compactly.

[Brief description of drawings]

FIG. 1 is a block diagram of an embodiment of a protection circuit for a magnetron modulation circuit according to the present invention. 1 ... Magnetron, 2 ... Modulation circuit power supply, 3 ... Thyristor (FET), 4 ... Detection circuit, 5 ... Trigger amplification circuit, 6 ... Heater power supply, 7 ... Pulse transformer, 8 ... Pulse forming circuit.

Claims (1)

[Scope of utility model registration request] 1. A protection circuit for a modulation circuit of a pulse magnetron, wherein a heater current monitoring means for outputting an alarm signal when a heater current value of the magnetron is a predetermined value or less, and a high voltage applied to the magnetron by the alarm signal. A protection circuit for a magnetron modulation circuit, comprising: a high-voltage interruption means for interruption.