Frequency lock loop for constant switching frequency of DC-DC converters
AssigneeReed Semiconductor Corporation
InventorsJiwei Fan, Yingqian Ma, Jingyuan Chen, Hal Chen, Jialun Du
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Abstract
A frequency lock loop for a constant switching frequency of DC-DC converter, wherein the frequency lock loop includes a modulation circuit to generate a modulation signal in response to an input signal of the DC-DC converter and a frequency signal. Wherein a timer of the DC-DC converter generates a timing signal in response to the input signal, and wherein the frequency signal is a function of the timing signal.
Claims16
A switching power supply controller comprising:
- a PWM timing circuit configured to generate a sample signal and a reset signal, wherein a leading edge of the sample signal occurs earlier than a leading edge of the reset signal;
- a frequency detection capacitor configured to be charged by a current source, wherein a voltage across the frequency detection capacitor is reset by the reset signal;
- a sample and hold circuit configured to detect a peak voltage across the frequency detection capacitor;
- a comparator configured to receive a ramp signal, a threshold voltage signal, the peak voltage and a predetermined reference, wherein a difference between the peak voltage and the predetermined reference is configured to adjust a comparison result between the ramp signal and the threshold voltage signal;
- and
- a timer configured to generate a timing signal based on the comparison result.
A method of removing variable switching frequencies from a direct current to direct current (DC-DC) converter utilizing a constant on/off time generator, the method comprising:
- charging a frequency detection capacitor by a current source, wherein a voltage across the frequency detection capacitor is reset by a reset signal;
- in response to a sample signal, sampling a peak voltage across the frequency detection capacitor, wherein a leading edge of the sample signal occurs earlier than a leading edge of the reset signal;
- comparing the peak voltage with a predetermined reference;
- converting a voltage difference between the peak voltage with the predetermined reference into a current difference;
- and
- adjusting a comparison result between a ramp signal and a threshold voltage signal based on the current difference.
Dependencies are inferred from the claim text.