Current limited supplied, output shunt regulated, off-line switching power supply for use with an ultrasonic motion detector

This paper describes a current limited supplied, fixed frequency, fixed duty cycle buck converter controlled by a shunt regulator at the output. This atypical operation is useful for a line voltage, low current supply used in a low cost, high volume production product. The fixed duty cycle and frequency are required to maintain a low noise floor for the operation of an ultrasonic motion detector.