JPS6348282Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field] The present invention relates to a hyperthermia magnetron drive circuit for generating output-controlled microwaves from a magnetron.

[Prior Art] A conventional magnetron drive circuit for hyperthermia that generates output-controlled microwaves from a magnetron uses a commercial power supply 10 as shown in FIG.
, a step-up transformer 12 that boosts the voltage of the power supply to about 2 kV to 3 kV, a rectifier 14 that rectifies the AC output on the secondary side of the step-up transformer 12, and a rectified drive voltage of about 2 kV to 3 kV. It consists of a variable resistor 16 for varying the value. Then, by applying an arbitrary voltage within a predetermined range between the cathode 18a and the anode 18b of the magnetron 18 by operating the variable resistor 16, the magnetron 18 is
8 generates microwaves whose output is controlled.

In addition, as shown in Fig. 2 as another conventional example,
Sending a rectangular wave pulse signal 20 with a frequency of about 10 to 20 kHz to the primary side of the step-up transformer 12 instead of the commercial power supply 10 and changing the pulse width of this pulse signal 20 without using the variable resistor 16. There is also a magnetron drive circuit that generates microwaves whose output is controlled from the magnetron 18.

However, in the conventional example shown in FIG.
Since the phase of the AC power source is controlled by the variable resistor 16, the circuit configuration is simple, but it has the disadvantage that the microwave output cannot be automatically controlled. signal 2
This has the disadvantage that the circuit configuration for arbitrarily adjusting the zero pulse width is complicated.

[Purpose of the invention] The present invention was devised in view of the drawbacks of the prior art, and its purpose is to provide a magnetron drive circuit for hyperthermia that can automatically and accurately control the output of microwaves with a simple circuit configuration. be.

[Configuration of the invention] In order to achieve this object, the present invention provides a phase control circuit that controls the phase of an AC power source using a trigger signal, a trigger circuit that can adjust the phase control angle of the phase control circuit, and a phase control circuit that controls the phase of an AC power supply using a trigger signal. A transformer and a rectifier for boosting and rectifying the output voltage from the circuit and applying it between the cathode and anode of the magnetron, and a current flowing to the light emitting element in the trigger circuit based on a detection signal obtained by detecting the output of the microwave. output control means for automatically controlling the phase angle of the phase control circuit by controlling the trigger circuit; The device is characterized in that it performs phase angle control while preventing noise from being mixed into the control signal.

[Embodiments of the invention] Hereinafter, preferred embodiments of the invention will be described with reference to the drawings.

In FIG. 3, for example, a triax 24 is used as a phase control circuit for controlling the phase of the AC power supply 22 using a trigger signal, which will be described later.
A 100V AC power supply 22 is applied between the main electrodes 24a and 24b of the triax 24, and a trigger is provided at the gate terminal 24c of the triax 24, which can adjust the phase control angle of the sine wave AC of the power supply 22 by conducting the triax 24. A circuit 26 is connected.

This trigger circuit 26 is composed of a photocoupler 28, a CR circuit consisting of a resistor R connected in parallel with the resistor Rp of the light receiving element 28a of the photocoupler 28, and a capacitor C connected in series with the resistor R, and a diagonal 30 as a trigger element. ing. Therefore, the trigger circuit is internally electrically isolated and operates via an optical signal, and this trigger circuit functions as an isolator that removes common mode noise from the control signal.

The light emitting element 28b of the photocoupler can change the light emitting state of the light emitting element 28b by a current source 32 that can control the current value, and the time constant of the CR circuit changes according to the change in the resistance value of the light emitting element 28a. It's getting old.

Also, both terminals 30a-30 of the diac 30
The voltage of a capacitor C is applied between the capacitor C and the gate 24c of the triac 24 when the voltage charged in the capacitor C reaches the trigger voltage of the diac 30. Trigger current flows to At this time, the triac 24 is turned on, and the two terminals 24a and 24b of the triac 24 become conductive, and the voltage of the AC power supply 22 is applied to the primary side of the step-up transformer 12.

Further, in the vicinity of the magnetron 18, a diode detector 38 consisting of a diode 34 and a resistor 36 for detecting the output of microwaves generated from the magnetron 18, and the diode detector 38 are provided.
A comparator 40 which inputs the output voltage generated in the resistor 36 of No. 8 and compares this output voltage with a reference voltage, and a light emitting element 28b which inputs the control signal from the comparator 40 to the base and has one end connected to the collector. Output control means consisting of a control transistor 42 for controlling the flowing current is provided.

Incidentally, since the magnitude of the current flowing from the current source 32 to the light emitting element 28b can be changed appropriately according to the output state of the microwave generated from the magnetron 18, the light emitting state of the light emitting element 28b changes and the resistance value of the light receiving element 28a changes. changes, and the time constant of the CR circuit changes. Therefore, it is possible to change the time it takes for the voltage between both electrodes of the capacitor C to reach the breakover voltage that triggers the diode 30, thereby changing the timing at which the triax 24 is triggered, that is, the phase control angle of the AC power source 22, by changing the phase control angle of the AC power source 22. It can be automatically changed according to the microwave output generated from the microwave.

Then, as shown in Figure 4a, from the AC power source
When a 100V sine wave alternating current 100V is applied to the triax 24, when the CR circuit has a certain time constant, due to the charging characteristics of the capacitor C, the triac 3
0 is applied with a voltage shown in a voltage waveform 102, and turns on when the voltage applied to the diode 30 reaches the diode trigger voltage shown at point A, and thereafter the voltage waveform 104 follows the discharge characteristics of the capacitor.
becomes.

As a result of the trigger 24 being triggered at point A, as shown in FIG.
06, and this voltage waveform 106 is boosted and rectified by the step-up transformer 12 and rectifier 14 shown in FIG. 3 to become the voltage waveform 108 shown in FIG. is applied to the magnetron 18 to generate microwaves.

The phase control angle α is automatically adjusted by the output control means according to the output state of the microwave generated from the magnetron 18, and the average voltage value of the voltage waveform 108 can be changed by changing the phase control angle α. The output state of the microwaves generated from the magnetron 18 can be automatically controlled.

According to this embodiment, the output of microwaves can be automatically controlled with a simple circuit configuration.

In addition, although the diac 30 was used as the trigger element in the above embodiment, it is not limited to this, and UJT,
CUJT, PUT, etc. can be used as a trigger element, and triac 2 can also be used as a phase control circuit.
4 may be replaced by a combination of transistors or a combination of thyristors, and it is also possible to use other semiconductor elements.

[Effects of the invention] As explained above, according to the invention, the magnetron drive circuit for hyperthermia can have a simple circuit configuration, and the output of microwaves generated from the magnetron can be automatically controlled. There is an effect.

In addition, by using a photocoupler that has insulation separation between the input and output of the trigger circuit on the input side and functions as an isolator that removes common-mode noise, it is possible to prevent noise signals from entering the signal system, ensuring reliable phase control. It also has the effect of allowing you to do the following.

[Brief explanation of the drawing]

1 and 2 are circuit diagrams showing conventional examples of different magnetron drive circuits, FIG. 3 is a circuit diagram showing an embodiment of the magnetron drive circuit for hyperthermia of the present invention, and FIG. 4a is a circuit diagram showing the voltage applied to the diac and FIG. 4B is a voltage waveform diagram showing the sine wave voltage of the power supply, FIG. 4B is a voltage waveform diagram applied to the primary side of the step-up transformer, and FIG. 4C is a voltage waveform diagram applied to the magnetron. 12... Transformer, 14... Rectifier, 18... Magnetron, 18a... Cathode, 18b... Anode,
22...AC power supply, 24...triax (phase control circuit), 26...trigger circuit, 28...photocoupler, Rp, R, C...CR circuit, 30...diax (trigger element), 38...diode Detector, 40... Comparator, 42... Control transistor.

Claims (1)

[Scope of utility model registration request] A phase control circuit that controls the phase of an AC power supply using a trigger signal, a trigger circuit that can adjust the phase control angle of the phase control circuit, and a magnetron cathode that boosts and rectifies the output voltage from the phase control circuit.
The phase angle of the phase control circuit is automatically controlled by controlling the current flowing to the light emitting element in the trigger circuit using a transformer and a rectifier for applying between the anodes and a detection signal obtained by detecting the output of the microwave. The trigger circuit includes a photocoupler whose light emission state is adjusted, a CR circuit including a resistance of a light receiving element of the photocoupler, and a trigger element.
1. A magnetron drive circuit for hyperthermia, which is characterized in that it performs phase angle control while preventing noise from being mixed into a control signal.