Slope compensation for peak 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.
Claims13
A ramp signal generator generating a slope compensated ramp signal for a peak current mode control modulator, the peak 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;
- a switch coupled between the first node and the third node, the switch being controlled by a signal indicative of the pulse-width modulation signal, the switch being open during an on-duration of the pulse-width modulation signal corresponding to an up-ramp of a current mode signal and the switch being closed during an off-duration of the pulse-width modulation signal corresponding to an down-ramp of the current mode signal;
- a first current source providing a current proportional to the input voltage to the first node to charge the first capacitor;
- a second current source providing a current proportional to the input voltage to the third node to charge the second capacitor;
- and
- a first current sink providing a current proportional to two times the regulated output voltage to the third node to discharge the third node,
- wherein in response to the switch being open during the on-duration of the pulse-width modulation signal, the ramp signal ramps up with a slope being proportional to the input voltage;
- and in response to the switch being closed during the off-duration of the pulse-width modulation signal, the ramp signal ramps down with a slope being proportional to the output voltage.
A method of generating a slope compensated ramp signal in a peak current mode modulator, the peak current mode 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 an on-duration and an off-duration;
- generating an up-ramp of the ramp signal having a slope proportional to the input voltage during the on-duration of the pulse-width modulation signal;
- generating a down-ramp of the ramp signal having a slope proportional to the output voltage during the off-duration of the pulse-width modulation signal;
- and
- providing the up-ramp and the down-ramp as the slope compensated ramp signal.
Dependencies are inferred from the claim text.