Slope Compensation for Current Mode Control Modulator
AssigneeAlpha and Omega Semiconductor (Cayman) Ltd.
InventorsNicholas I. Archibald, Rhys S. A. Philbrick, Steven P. Laur
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Abstract
A ramp signal generator generates a slope compensated ramp signal with optimal slope compensation for a current mode control modulator. In some embodiments, the ramp signal generator generates a ramp signal for the current control loop having a first ramp portion with slope compensation and a second ramp portion that matches the expected current mode signal. In some embodiments, the ramp signal generator is implemented using a switched capacitor circuit with charge scaling to generate the ramp signal with optimal slope compensation built into the ramp signal.
Claims20
A ramp signal generator generating a slope compensated ramp signal for a current mode control modulator, the current mode control modulator generating a pulse-width modulation signal in response to a feedback voltage signal indicative of a regulated output voltage generated from an input voltage, the ramp signal generator comprising:
- a first capacitor coupled between a first node and a second node, the second node being biased to a reference voltage and the first node providing the slope compensated ramp signal;
- a second capacitor coupled between a third node and the second node;
- and
- a first switch coupled between the first node and the third node, the first switch being controlled by a first signal indicative of the pulse-width modulation signal, the first switch being open during a first duration of the pulse-width modulation signal and the first switch being closed during a second duration of the pulse-width modulation signal,
- wherein in response to the first switch being open during the first duration of the pulse-width modulation signal, the ramp signal generator generates the slope compensated ramp signal having a first ramp portion generated by dividing a charge associated with an expected current level of the current control loop of the current mode control modulator among the first capacitor and the second capacitor during the first duration of the pulse-width modulation signal, the first capacitor being disconnected from the second capacitor and providing the first ramp portion of the slope compensated ramp signal, and
- wherein in response to the first switch being closed during the second duration of the pulse-width modulation signal, the ramp signal generator generates the slope compensated ramp signal having a second ramp portion generated by sharing the charge associated with the expected current level of the current control loop of the current mode control modulator between the first capacitor and the second capacitor during the second duration of the pulse-width modulation signal, the first capacitor being connected to the second capacitor and the first and second capacitors providing the second ramp portion of the slope compensated ramp signal.
A method of generating a slope compensated ramp signal in a current mode control modulator, the current mode control modulator generating a pulse-width modulation signal in response to a feedback voltage signal indicative of a regulated output voltage generated from an input voltage, the method comprising:
- receiving the pulse-width modulation signal having a first duration and a second duration;
- generating a first ramp portion of the slope compensated ramp signal by dividing a charge associated with an expected current level of the current control loop of the current mode control modulator among first and second capacitors during the first duration of the pulse-width modulation signal;
- and
- generating a second ramp portion of the slope compensated ramp signal by sharing the charge associated with an expected current level of the current control loop of the current mode control modulator between the first and second capacitors during the second duration of the pulse-width modulation signal;
- and
- providing the first ramp portion and the second ramp portion as the slope compensated ramp signal.
Dependencies are inferred from the claim text.