AC turntable motor control circuit, for DC-powered microwave oven, has inverted DC motor supply rectified and regulated to control the magnetron's inverted DC supply

摘要

A controlling micro-computer (54) provides control signals (E1,E2) for an inverter comprising push-pull transistors (56,58) and a transformer (60), operating from a 12v DC supply. The 21v AC output powers the turntable motor (62), and is rectified (64) and regulated (66) to provide, when the oven door switch (DSW) is closed, a constant 15v DC supply (Vcc) for the main control circuit (46). The latter's output signals (01,02) control alternately conducting field effect transistors (48,50) which supply an HV transformer (52) from the DC source (30). The transformer secondary supplies the oven's microwave source, a magnetron (MGT), via a voltage doubler circuit. Following the usual practice, the oven interior light (32), and fan (36), are controlled by the door switch via relays (34,38). The door switch also controls interlock switches (SW1,SW2), which prevent microwave operation when the door is open.