Micrel, Incorporated

Jayant Rao

Vinit Jayaraj

A boost switching regulator incorporates a peak inductor current modulation circuit to modulate the peak inductor current as a function of the load current, the input voltage, the regulated output voltage, and a fixed current value. In this manner, the switching frequency of the boost regulator can be maintained above a given value or within a given frequency range over a wide range of load conditions and also over input voltage variations and output voltage settings.

Boost regulator incorporating peak inductor current modulation

A boost switching regulator incorporates a ripple injection circuit to generate a voltage ripple signal for feedback control that mimics the actual ripple signal of the regulated output voltage. In this manner, the ripple injection circuit achieves optimal ripple injection for stable and enhanced feedback control. In one embodiment, the injected ripple signal is generated from a current injection signal that mimics the difference between the inductor current that flows through the synchronous rectifier and the load current when the synchronous rectifier is on. The injected voltage ripple signal is generated when the current injection signal is integrated by a feedforward capacitor.

Optimal ripple injection for a boost regulator

A control circuit in a PFM/PWM boost switching regulator includes a timer based PFM exit control circuit configured to receive a first control signal for controlling a main power switch, a zero-cross signal indicative of an inductor current having reached zero current value, and a timer reference signal indicative of a timer threshold duration. The timer based PFM exit control circuit assesses an idle time of the inductor current based on the first control signal and the zero-cross signal. The timer based PFM exit control circuit asserts the PFM exit signal in response to the idle time decreasing below a level being equal to or less than the timer threshold duration, and the boost switching regulator transitions out of the PFM mode and into the PWM mode in response to the PFM exit signal being asserted.

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Santa Clara, CA, United States of America

Jayant Rao