PWM CONTROLLER FOR DC POWERED HEATING BLANKET

摘要

A PWM-based controller for controlling a voltage applied to a DC-powered electric heating blanket from a power source includes a square wave producing circuit for connection in the circuit with the battery and the blanket. The square wave producing circuit produces a variable duty cycle square wave for controlling application of power to the blanket in accordance with the duty cycle of the square wave. The square wave producing circuit has a control input for varying the duty cycle of the square wave in response to a voltage at the control input. The voltage at the control input may be set manually using a voltage varying circuit connected to the power source. A low voltage detection circuit may also be connected to the power source and coupled to the control input of the square wave producing circuit for automatically producing a voltage that decreases the duty cycle of the square wave when the battery voltage decreases to or below a predetermined level.