US 12,413,139 B2
Control circuit and control method for three-level DC-DC converter
Shuai Zhang, Hangzhou (CN); Zhen Zhang, Hangzhou (CN); and Wang Zhang, Hangzhou (CN)
Assigned to Silergy Semiconductor Technology (Hangzhou) LTD, Hangzhou (CN)
Filed by Silergy Semiconductor Technology (Hangzhou) LTD, Hangzhou (CN)
Filed on Feb. 16, 2023, as Appl. No. 18/110,631.
Claims priority of application No. 202210239205.X (CN), filed on Mar. 11, 2022.
Prior Publication US 2023/0291304 A1, Sep. 14, 2023
Int. Cl. H02M 3/158 (2006.01); H02M 1/00 (2006.01); H02M 1/088 (2006.01); H02M 1/32 (2007.01)
CPC H02M 1/322 (2021.05) [H02M 1/0095 (2021.05); H02M 1/088 (2013.01); H02M 3/158 (2013.01)] 18 Claims
OG exemplary drawing
 
1. A method of controlling a three-level DC-DC converter having first, second, third, and fourth power switches coupled in series between an input voltage and a reference ground, and a flying capacitor coupled between a common node of the first and second power switches and a common node of the third and fourth power switches, the method comprising, when a voltage across the flying capacitor is out of a first threshold range, one of:
a) operating the flying capacitor in a first mode in which the voltage across the flying capacitor is controlled to not be decreased in at least two consecutive first intervals, wherein each first interval is half of a switching period of the three-level DC-DC converter; and
b) operating the flying capacitor in a second mode in which the voltage across the flying capacitor is controlled not to be increased in at least two consecutive first intervals, such that the voltage across the flying capacitor approaches a predetermined value;
c) the method further comprising controlling the three-level DC-DC converter to operate in the first mode when the voltage across the flying capacitor is less than a lower threshold of the first threshold range, such that the flying capacitor consecutively enters a charging interval for a plurality of times, wherein the charging interval comprises one charging stage and one holding stage; and
d) the method further comprising controlling the three-level DC-DC converter to operate in the second mode when the voltage across the flying capacitor is greater than an upper threshold of the first threshold range, such that the flying capacitor consecutively enters a discharging interval for the plurality of times, wherein the discharging interval comprises one discharging stage in and one holding stage.