A Segmented and Linear Frequency Controller for Flyback Converters.

This paper presents a segmented and linear frequency controller for flyback converters, which are widely used in power conversion applications, like isolated automotive, industrial, and medical power supplies. Due to the direct relationship between load and output of error amplifier (EA), V EAOUT , in the control loop, the output of EA is adopted to control the system operating frequency by generating a current proportional to the output of EA, I OUT , which is injected into a current-controlled oscillator for frequency modulation. Besides, the maximum and minimum frequencies are also settled for rang limitation used for multi-mode control, such as discontinuous conduction mode (DCM), and burst mode. Within a 0.18μm BCD process, the proposed segmented and linear frequency controller is simulated in a primaryside control flyback converter, whose results show that during the clamping range, the linear relationship between I OUT and V EAOUT is 2.61μA/V. Furthermore, the upper and lower limits are 380kHz and 12kHz, respectively.