Panasonic NN-K593MF Service Manual

3.1. Variable power cookingcontrolHigh Voltage Inverter Power supply (U) controls output powerby the signal from Digital Programmer Circuit (DPC). Powerrelay stays ON for P3 to P10 and For P1 to P2, both inverterdrive signal and power relay to control output power.NOTE:The ON/OFF time ratio does not correspond with thepercentage of microwave power since approximately 2seconds are required for heating of magnetronfilament.Variable Power CookingPOWER SETTING OUTPUTPOWER(%)APPROX.ON-OFF TIME OFPOWER RELAY (RY1)ON(SEC) OFF(SEC)HIGH P10 100% 22 0P9 90% 22 0P8 80% 22 0MEDIUM-HIGH P7 70% 22 0MEDIUM P6 60% 22 0P5 50% 22 0P4 40% 22 0MEDIUM-LOW P3 30% 22 0P2 20% 15 7LOW P1 10% 8 14DEFROST P3 30% 22 03.2. Inverter power supply circuitNEW H.V.This Inverter Power Supply Circuit supplies 4,000V DC to themagnetron tube from the line voltage, 220-240V 50Hz/60Hz ACinput. functions as the H.V. transformer, the H.V.capacitor andH.V.diode.1. The AC input voltage 220-240V 50Hz/60Hz is rectified toDC voltage immediately.2. DC voltage will be supplied to the switching devices calledIGBT. These devices will be switched ON-OFF by the 20 to40 KHz PWM(pulse width modulation) signal from themicrocomputer in the DPC.3. This drives the High voltage transformer to increase up to2,000V AC and approximately 3V AC by means oftransformer.4. Then the half-wave doubler voltage rectifier circuit,consisting of the H.V. diodes and Capacitors, generates thenecessary 4,000V DC needed for the magnetron.5. Output power of the magnetron tube is always monitored bythe signal output from the current transformer built into theinverter circuit.6. Then this signal will be fed back to the microcomputer in theDPC to determine operating conditions and outputnecessary to control PWM signal to the Inverter PowerSupply to control output power.3.3. Inverter turbo defrostWhen this Auto Control feature is selected and the Start Pad istapped:1. The digital programer circuit determines the power level andcooking time to complete cooking and indicates theoperating state in the display window. Table shows thecorresponding cooking times for respective serving bycategories.2. When cooking time the display window has elapsed, theoven turns off automatically by a control signal from thedigital programmer circuit.3 DESCRIPTION OF OPERATING SEQUENCE7NN-S453WF