V2 Control with Capacitor Current Ramp Compensation Using Self-Calibrated Lossless Capacitor Current Sensing

V2 control is a popular control scheme in Point-of-Load Buck converters and Voltage Regulators for microprocessor.  V2 control with ceramic capacitor is unstable when the converter operates at hundreds of kHz.  Moreover, the jittering issue is a common concern in the commerical products.  Compensating the loop by inductor current ramp increases the output impedance while compensating the loop by external ramp cannot always achieve desireable damping.  This invention proposes capacitor current ramp compensation for V2 control.  It can provide desireable damping to the loop while maintaining ultra fast load transient response.  Meanwhile, the capacitor current ramp helps to reduce the jittering.  The lossless sensing circuit is a simple R-C branch connected in parallel with output capacitor, the capacitor current is emulatd by the voltage acrosse the sensing resistor.  The sensing scheme is very easy to implement in a control IC.  Moreover, two simple time-constant matching methods are proposed.  First is a passive matching method by carefully selectingof both sensing capacitor and output capacitor to compensate part of capacitanse variation from the DC bias and temperature change.  The second is a novel active matching method based on proposed calibration technique to compensate other possible capacitance for optimal dynamic response over wide duty cycle range operation, and provide real-time over current protection.

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For Information, Contact:
Li Chen
Licensing Associate
Virginia Tech Intellectual Properties, Inc.
(540) 443-9217
Yingyi Yan
Pei-Hsin Liu
Fred Lee