DESCRIPTION
OF THE SI9114A BID/CMOS PWM CONTROLLER The Si9114A controller is similar in configuration to the Si9110. It uses a traditional constant frequency current mode control, the most commonly used architecture. The duty cycle is limited to less than 50% to avoid problems with core reset. Current mode control is presently the de-facto standard for PWM control circuits. Indeed, it is the only candidate that should be considered, given its many advantages: S Cycle by cycle current limit protection S Simple loop compensation, eliminating effect of output inductor S Excellent fast transient response due to inner control loop S Automatic input voltage feed-forward compensation depletion mode MOSFET. The 9.2-V threshold has a hysteresis of 300 mV to prevent oscillations when the transition voltage is not clearly defined or when high-line supply impedance is encountered. For applications where the input dc voltage is not high, and the chip power consumption is not excessive, the feedback winding can be eliminated.
Vishay
