Frequency Modulation and Pulse-Width Modulation Pin-Selectable Controls for Switching Power Supplies
Original Publication Date: 1987-Aug-01
Included in the Prior Art Database: 2005-Feb-01
A technique is described whereby an electrical control circuit, implemented along with a switching regulator power supply, allows the same integrated circuit control module to be used in the regulation of the output voltage, whether in frequency modulation (FM) mode or in pulse- width modulation (PWM) mode, through the use of a selector pin arrangement. The partial block diagram of the control module circuit, as shown in the figure, utilizes voltage-controlled oscillator (VCO) 10 for control of the FM regulator and both comparator 11 and VCO 10 for control of the PWM regulator. To use FM, the designer specifies pin B to be connected to ground, so as to disable the PWM output portion of the circuit. The FM control input is applied to pin A of VCO 10, which varies the frequency. The output of VCO 10 is applied to flip-flop 12.