Patent ID: 6771025
Filing Date: 2004-08-03
Classification: H05B

Abstract:
A control circuit for a magnetron, the circuit being supplied from a source of a.c. voltage and comprising a power switch, a process controller/firing circuit for the power switch, characterised in that the circuit further comprises separate first and second transformers, the first transformer (7) supplies a desired filament voltage to the magnetron (1), and the second transformer (9) controls the current flow in the magnetron and hence the power output thereof, the second transformer being controlled by the operation of the process controller/firing circuit (3) and the power switch, and wherein the power switch comprises a pair of inversely connected back to back thyristors (TH1, TH2) and the process controller/firing circuit comprises a half wave blanking power controller whereby control of the second transformer and hence control of the power output of the magnetron is achieved using a phase angle technique and wherein in-rush current is limited by having the starting point for firing other than at the zero voltage of each switching cycle.