US 9,812,975 B2
Resonant converter with capacitive mode control and associated control method
Yuedong Chen, Chengdu (CN)
Assigned to Chengdu Monolithic Power Systems Co., Ltd., Chengdu (CN)
Filed by Chengdu Monolithic Power Systems Co., Ltd., Chengdu (CN)
Filed on Sep. 21, 2016, as Appl. No. 15/272,418.
Claims priority of application No. 2015 1 0613326 (CN), filed on Sep. 24, 2015.
Prior Publication US 2017/0093296 A1, Mar. 30, 2017
Int. Cl. H02M 1/088 (2006.01); H02M 3/335 (2006.01); H02M 1/00 (2006.01)
CPC H02M 3/33546 (2013.01) [H02M 1/088 (2013.01); H02M 2001/0009 (2013.01)] 20 Claims
OG exemplary drawing
 
8. A control circuit used for controlling a resonant converter, comprising:
a voltage sensing circuit, configured to sense an output voltage signal of the resonant converter to generate a feedback voltage signal;
a current sensing circuit, configured to sense a current flowing through a resonant inductor of the resonant converter to generate a current sense signal;
a mode judging circuit, configured to receive the current sense signal, and further configured to compare the current sense signal with a zero-crossing threshold to generate a mode signal, wherein the mode signal is configured to judge whether the resonant converter operates in an inductive mode or a capacitive mode; and
a frequency controller, configured to receive the mode signal and the feedback voltage signal, and further configured to generate a high-side control signal and a low-side control signal respectively used for controlling a high-side switch and a low-side switch of the resonant converter based on the feedback voltage signal and the mode signal, wherein the frequency controller comprises a setting capacitor, and wherein the frequency controller further comprises N up thresholds and N low thresholds, and wherein each of the N up thresholds is corresponding to each of the N low thresholds, and wherein each of the N up thresholds is higher than each of the N low thresholds correspondingly, and wherein N is a positive integer and is larger than or equal to 2, and wherein
when the resonant converter operates in the inductive mode, the frequency controller is configured to compare a setting voltage signal across the setting capacitor with the largest one of the N up thresholds, and with the smallest one of the N low thresholds in each operation cycle to generate the high-side control signal and the low-side control signal, wherein the operation cycle comprises one or more switching cycles of the resonant converter, and wherein
when the resonant converter enters into the capacitive mode, the frequency controller is configured to compare the setting voltage signal with each of the N up thresholds sequentially operation cycle by operation cycle, and with each of the N low thresholds sequentially operation cycle by operation cycle to generate the high-side control signal and the low-side control signal, and wherein
the frequency controller is further configured to change a switching frequency of the resonant converter by varying the N up thresholds and the N low thresholds.