Magnetron Power Supply

• US 20130134872A1
• Filed: 07/12/2011
• Published: 05/30/2013
• Est. Priority Date: 07/13/2010
• Status: Active Grant

• Current Assignee: Ceravision Limited
• Original Assignee: Ceravision Limited
• Inventors: Lidstrom, Kjell
• Granted Patent: US 9,390,879 B2
• Time in Patent Office: Days
• US Class Current: 315/39.51
• CPC Class Codes: H01J 23/34 Circuit arrangements not adapted to a particular application of the tube and not otherwise provided for
• CPC Class Codes: H01J 25/50 Magnetrons, i.e. tubes with a magnet system producing an H-field crossing the E-field with travelling wave not moving completely around the electron space H01J25/42; functioning with plural reflection or with reversed cyclotron action H01J25/62, H01J25/64
• CPC Class Codes: H05B 6/685 the measurements being made at the low voltage side of the circuit

Abstract

A power supply for a magnetron has a PFC DC voltage source and an HV (High Voltage) converter. The voltage source is mains driven and supplies DC voltage above mains voltage on line, smoothed by capacitor to the HV converter. The latter supplies switched alternating current to transformer. This supplies higher voltage alternating current to a rectifier, in turn supplying the magnetron with high, magnetron powering, anode voltage on line. The DC voltage source has an PFC inductor, which is switched by a transistor switch under control of an integrated circuit. It is the inductor which enables the voltage source to provide a variable DC voltage. An input rectifier is provided for rectifying mains voltage. The output voltage of the voltage source is monitored and fed back to the integrated circuit by a voltage divider.

Claims

1. A power supply for a magnetron, the power supply including:

a Magnetron, Switched Converter Power Circuit, the MSCPC having a control input and being adapted to generate increased voltage at a certain multiple of DC voltage applied to it when a normal control voltage or a control voltage deviating in one direction from the normal is applied to the control input, the one direction being ineffective on the multiple, and an increased voltage at a decreasing multiple with deviation of the control voltage from the normal in the other direction, the other direction being effective on the multiple, i.e. reducing it;

a DC voltage source arranged to supply the DC voltage or the DC voltage together with an increase therein to the MSCPC;

means for measuring power or current from the DC voltage source passing through the MSCPC for driving the magnetron;

converter control means for applying a control voltage to the MSCPC in accordance with a function of the difference between a desired magnetron power and the said measured power or current; and

DC voltage control means for passing deviation of the control voltage in the ineffective-on-the-multiple direction to the DC voltage source for causing it to supply the increased DC voltage to the MSCPC;

the arrangement being such that in use;

when the converter control means applies the normal voltage to the MSCPC, the latter is supplied with the DC voltage and applies normal power to the magnetron for operating it at normal power,

when the converter control means applies normal voltage deviated in the multiple-effective direction, the MSCPC is supplied with the DC voltage and applies less power to the magnetron for operating it at less than normal power and

when the converter control means applies normal voltage deviated in the multiple-ineffective direction, the MSCPC is supplied with increased DC voltage and applies higher power to the magnetron for operating it at higher than normal power.

2. A magnetron power supply as claimed in claim 1, wherein the DC voltage control means for passing deviation of the control voltage is a microprocessor programmed to produce a control voltage indicative of a desired output power of the magnetron to the MSCPC for controlling the power of the magnetron.

3. A magnetron power supply as claimed in claim 2, wherein the power or current measuring means is a resistor in series with the MSCPC, one end of the resistor being grounded and the other being connected to the MSCPC and to the microprocessor.

4. A magnetron power supply as claimed in claim 2, wherein the converter control means is an adaptation of the microprocessor programmed to control the voltage source in the manner set out.

5. A magnetron power supply as claimed in claim 1, wherein the converter control means is:

a microprocessor programmed to produce a control voltage indicative of a desired output power of the magnetron and

an integrated circuit arranged in a feed back loop and adapted to apply a control signal to the MSCPC in accordance with a comparison of a voltage from the measuring means with the voltage from the microprocessor for controlling the power of the magnetron to the desired power.

6. A magnetron power supply as claimed in claim 5, wherein the power or current measuring means is a resistor in series with the MSCPC, one end of the resistor being grounded and the other being connected to the MSCPC and to an input of the integrated circuit, preferably via a feed back resistor.

7. A magnetron power supply as claimed in claim 5, wherein the integrated circuit is an operational amplifier connected as an error signal amplifier, the error signal being the difference between signals indicative of a measurement of the converter current and the desired output power of the magnetron.

8. A magnetron power supply as claimed in claim 6, wherein a ripple smoothing resistor is incorporated between the input of the integrated circuit having the series resistor connected to it and a DC voltage source line.

9. A power supply as claimed in claim 5, wherein the integrated circuit is arranged as an integrator with a feedback capacitor, whereby its output voltage is adapted to control a voltage-to-frequency circuit for controlling the converter.

10. A magnetron power supply as claimed in claim 5, wherein the DC voltage control means for passing deviation of the control voltage is a hardware circuit is provided between an output of the integrated circuit and a control input of the DC voltage source, the circuit being adapted and arranged to:

isolate the DC voltage source control input from the integrated circuit output, when the required magnetron output is normal or less, and to

pass the control voltage deviated in the ineffective direction, or a signal corresponding to it, to the DC voltage source control input.

11. A magnetron power supply as claimed in claim 10, wherein the hardware circuit is an emitter-follower transistor circuit connected to bias the common point of a voltage divider controlling the DC voltage source, the transistor circuit biasing up the divider voltage only when more than normal power is required.