US 12,483,139 B2
Multi-level conversion circuit and control method for flying capacitor voltage thereof
Yichao Wang, Shanghai (CN); Yuhua Hu, Shanghai (CN); Kai Dong, Shanghai (CN); and Jinfa Zhang, Shanghai (CN)
Assigned to Delta Electronics (Shanghai) Co., Ltd., Shanghai (CN)
Filed by Delta Electronics (Shanghai) Co., Ltd., Shanghai (CN)
Filed on Sep. 25, 2023, as Appl. No. 18/372,559.
Claims priority of application No. 202211401242.2 (CN), filed on Nov. 9, 2022.
Prior Publication US 2024/0162818 A1, May 16, 2024
Int. Cl. H02M 1/088 (2006.01); H02M 1/00 (2006.01); H02M 3/158 (2006.01)
CPC H02M 3/1584 (2013.01) [H02M 1/0012 (2021.05); H02M 1/0095 (2021.05); H02M 1/088 (2013.01)] 16 Claims
OG exemplary drawing
 
1. A control method for flying capacitor voltage, applied in a multi-level DC-DC conversion circuit, wherein the number of levels of the multi-level DC-DC conversion circuit is N which is an integer greater than or equal to three, the multi-level DC-DC conversion circuit comprises a positive input terminal, a negative input terminal, an inductor, N−1 lower switches, N−1 upper switches, N−2 flying capacitors, a positive output terminal and a negative output terminal, the positive input terminal and the negative input terminal are configured to receive an input voltage, the positive output terminal and the negative output terminal are configured to provide an output voltage, a first terminal of the inductor is electrically connected to the positive input terminal, the N−1 lower switches are connected in series between a second terminal of the inductor and the negative output terminal, the first lower switch and the (N−1)th lower switch are coupled to the second terminal of the inductor and the negative output terminal respectively, the N−1 upper switches are connected in series between the second terminal of the inductor and the positive output terminal, the first upper switch and the (N−1)th upper switch are coupled to the second terminal of the inductor and the positive output terminal respectively, the kth flying capacitor is connected between a common connection node of the kth lower switch and the (k+1)th lower switch and a common connection node of the kth upper switch and the (k+1)th upper switch, k is a positive integer less than or equal to N−2, the negative output terminal is electrically connected to the negative input terminal, and when the multi-level DC-DC conversion circuit works in a DCM (discontinuous conduction mode), the control method comprises steps of:
(a) determining the N−1 lower switches as N−1 main switches, and determining the N−1 upper switches as N−1 synchronous rectification switches;
(b) acquiring an adjustment value corresponding to each of the N−2 flying capacitors according to an actual voltage and a reference voltage of the flying capacitor; and
(c) adjusting a duty ratio of the kth main switch according to the adjustment value corresponding to the flying capacitor connected to the kth main switch, and adjusting a duty ratio of the (N−1)th main switch according to the adjustment value corresponding to the flying capacitor connected to the (N−1)th main switch, wherein regarding each of the N−1 main switches, the duty ratio is adjusted by a first adjustment amount when D<(N−2)/(N−1), the duty ratio is adjusted by a second adjustment amount when (N−2)/(N−1)<D≤1, a product of the first adjustment amount and the second adjustment amount is negative, and D is the duty ratio of the N−1 main switches before the adjustment.