Virginia Tech Intellectual Properties, Inc.

Pei-Hsin Liu

Fred C Lee

Qiang Li

Yingyi Yan

Paolo Mattavelli

Syed Bari

Virginia Li

A power converter using constant on-time (COT) or ramp pulse modulation (RPM) control achieves more rapid resumption of steady-state operation after a step-up load transient by extending an on-time of a switching pulse by interrupting a ramp voltage waveform that is compared with a threshold that equals a threshold voltage at the termination of a switching pulse or increasing a voltage with which the ramp voltage is compared. These techniques are applied to both single-phase and multi-phase power converters.

Current mode control DC-DC converter with single step load transient response

Response of a variable frequency switching constant on-time or adaptive on-time controlled power converter to a large step-up or step-down change in load is improved with a simple circuit that detects magnitude and polarity of a change in output voltage and initiates, extends or terminates conduction of power pulses from an input source through said power converter. Both the amplitude and duration of undershoot or overshoot of the transient response are reduced or, alternatively, the capacitance of an output filter may be significantly reduced and still provide comparable transient performance. The fast adaptive on-time control is applicable to multi-phase power converters using phase managers or one or more phase-locked loops for interleaving of power pulses.

Transient performance improvement for constant on-time power converters

In a multi-phase power converter using a phase-locked loop (PLL) arrangement for interleaving of pulse frequency modulated (PFM) pulses of the respective phases, improved transient response, improved stability of high bandwidth output voltage feedback loop, guaranteed stability of the PLL loop and avoidance of jittering and phase cancellation issues are achieved by anchoring the bandwidth at the frequency of peak phase margin. This methodology is applicable to multi-phase power conveners of any number of phases and any known or foreseeable topology for individual phases and is not only applicable to power converters operating under constant on-time control, but is extendable to ramp pulse modulation (RPM) control and hysteresis control. Interleaving of pulses from all phases is simplified through use of phase managers with a reduced number of PLLS using hybrid interleaving arrangements that do not exhibit jittering even when ripple is completely canceled.

Hybrid interleaving structure with adaptive phase locked loop for variable frequency controlled switching converter

Peak current, valley current or average current mode controlled power converters in either digital or analog implementations obtain a stabilized feedback loop and allow high system bandwidth design by use of an external ramp generator using a slope computation equation or design parameters based on fixing the quality factor of a double pole at one-half of the switching frequency at a desired value The slope of the external ramp waveform is tuned automatically with knowledge of the slope change in the waveform of inductor current of a power converter derived by differentiating a waveform in the current feedback loop. This autotuning of the external ramp generator provides immunity of quality factor change under variations of duty cycle, component values of topological change of the power converter.

External ramp autotuning for current mode control of switching converter

Operation of a switching power converter having an output capacitor having a small equivalent series resistance (ESR) is stabilized and jitter reduced by sensing capacitor current with gain and combining the resulting signal with the output voltage signal to provide a feedback signal to control switching of the power converter. capacitor current can be sensed without interfering with operation of the filter capacitor by providing a branch circuit having a time constant matched to the output or filter capacitor but an arbitrarily high impedance so as to be effectively lossless. The gain provided in the capacitor current signal can be tuned to provide optimally short settling time after load transients; generally within one switching cycle. Matching of time constants and/or tuning of gain can be performed automatically.

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Blacksburg, VA, United States of America

Pei-Hsin Liu