Electronic postage meter having a regulated power supply system responsive to a voltage developed in a transformer primary winding circuit

摘要

An electronic postage meter includes a printer mechanism for printing postage and a microcomputer system for monitoring the printing of postage by the printing mechanism. A secure housing protects the printing mechanism and the microcomputer system. A source of operating potential is provided and is external to the secure housing. The electronic postage meter includes a system for energizing the microcomputer system. A transformer is provided and is mounted within the secure housing. The transformer secondary winding is operatively connected to the microcomputer system. A controlling circuit is coupled to the transformer primary winding and also to the external source of operating potential. The controlling circuit controls the voltage applied to the transformer primary winding and operates to switch the voltage applied to the transformer primary winding between a first condition where the transformer primary winding is energized and a second condition where the primary winding is not energized. The controlling circuit includes a circuit for varying the period of time the transformer primary winding is energized and the period of time the primary winding is deenergized. The period varying circuit is operated in response to a voltage established in the transformer primary winding. The controlling circuit includes a terminal which is adapted to be energized by a predetermined source of operating voltage. A step up voltage generating circuit is coupled to the controlling circuit for energizing said terminal at a voltage which is greater than the predetermined voltage.