Power source circuit for microwave oven

DETAILED DESCRIPTION Accordingly, it is an object of the present invention to provide a power source circuit for a microwave oven wherein safety can be improved by reliably preventing the magnetron from oscillating when the door is open even if there is some failure of insulation of the high voltage transformer.
In accordance with the present invention, there is provided a power source circuit for a microwave oven which includes a first and second bus, a high voltage transformer and first, second and third door switches.
The first and second buses are connected to a power source.
The high voltage transformer has a primary winding with first and second ends connected to the first and second buses respectively.
The first door switch is connected between the first bus and the first end of the primary winding and is opened in response to opening of a door of the microwave oven.
Likewise, the second door switch is connected between the second bus and the second end of the primary winding and is opened by opening of the microwave oven door.
The third door switch has a movable contact and a first and second fixed contact.
The movable contact makes electrical contact with the first fixed contact in response to closure of the door and contacts the second fixed contact in response to opening of the door.
The movable contact and the first fixed contact are connected together and connected between the first switch and the first end of the primary winding when the door is closed.
Further, the movable contact and the second fixed contact are connected together and connected between the first switch and the second bus when the door is opened.