A power relay control circuit for a microwave oven including a microprocessor as its controller is provided, wherein two power relay driving transistors are to be turned on or turned off by a thyristor, which is triggered by a switching transistor, and a stabilizing circuit respectively. Two signals of different levels from terminals of the microprocessor are supplied to the base of the switching transistor and the stabilizing circuit in order to make the oven start heating operation. If the microprocessor operates in all possible abnormal states, both signals from the terminals of the microprocessor are to become the same level, all HIGH or all LOW, making either of the power relay driving transistors turned off, resulting in preventing power supply from being applied to the power relay.
A microcomputer-based control device for microwave ovens includes a timer defining an operation period of a magnetron and incorporated in the microcomputer, an encoder generating electrical pulses, the number of which is in accordance with an amount of angular displacement of an operation knob, the encoder being independent of the microcomputer, first and second semiconductor switches for starting an operation of the magnetron in response to either any one or a plurality of a pulse train generated by the encoder, the semiconductor switches being incorporated in the microcomputer, and a counter for setting, at the timer, a cooking period in accordance with the numer of pulses of the pulse train generated by the encoder.
A microwave oven is described suitable for use on transports where DC power is available. The microwave oven employs a first inverter to generate internal AC power that is then used to operate the microwave components other than the magnetron microwave source. The internal AC power is passed with relatively low current through the oven interlocks to activate and drive a power inverter that, through an additional output transformer winding, delivers high voltage power to the magnetron. In a preferred embodiment a relay, that is connected to sense when external AC power is available, causes an automatic switching that decouples the internal AC power from the power inverter to enable conventional operation from external AC line power. When external AC line power is no longer applied, the microwave oven automatically switches to operate from the available DC power.
An improved controller for a microwave oven capable of preventing it from an undesired heating caused by an erroneous operation thereof, which includes a heating member for generating heating energy; a power switch for controlling electric power supply to the heating member; a switch module including a plurality of switches for selecting a desired function; a microcomputer for outputting scanning signals having predetermined time differences to the switch module and for outputting a predetermined control signal in accordance with a key input signal outputted from the switch module; and a controller for controlling the power switch in accordance with control signals outputted from the microcomputer and a signal applied from the switch module, wherein the control signals includes a latch signal maintaining a predetermined state after the output signal of a switch is detected, while having the same level as a scanning signal outputted from a switch which is selected by an operation mode corresponding to scanning signals outputted from the switch module, and a power control signal which is transferred from a first state to a second state after the latch signal becomes a predetermined state and another predetermined time is lapsed while maintaining the first state.
5276300 - AC/DC powered microwave oven - Owned by International Marine Industries, Inc. (Guilford, CT) [*] Notice:The portion of the term of this patent subsequent to February 27, 2007 has been disclaimed.
A microwave oven is described suitable for use on transports where DC power is available. The microwave oven employs a first inverter to generate internal AC power that is then used to operate the microwave components other than the magnetron microwave source. The internal AC power is passed with relatively low current through the oven interlocks to activate and drive a power inverter that, through an additional output transformer winding, delivers high voltage power to the magnetron. In a preferred embodiment a relay, that is connected to sense when external AC power is available, causes an automatic switching that decouples the internal AC power from the power inverter to enable conventional operation from external AC line power. When external AC line power is no longer applied, the microwave oven automatically switches to operate from the available DC power. An efficient cooling fan is provided that is driven by a DC motor. The motor is provided DC power that is derived from a reverse coupling of AC line power through a transformer used at the output of the first inverter. During a DC power mode, the DC power available at a center tap of the primary winding of this transformer is used to drive the DC motor. Operating controls are described for the power inverter.
A temperature regulating control unit and method of making the same are provided, the unit comprising a RTD temperature sensor, a unit for applying electrical signals to the sensor, and a microcomputer for receiving digital signals from the sensor in relation to the temperature being sensed by the sensor, the unit for applying electrical signals to the sensor applying a varying voltage to the sensor.
