Abstract
The series resonant converter (SRC), controlled by the traditional pulse frequency modulation (PFM) with constant on-time, can operate in discontinuous conduction mode (DCM) and is applicable for high-voltage high-power applications with the requirement of a wide output voltage range. However, in the traditional PFM with constant on-time, the resonant capacitor voltage will be higher than the input voltage during the zero current stage, leading to a higher maximum magnetic flux density (MMFD) case. To avoid this, a novel asymmetric pulse frequency modulation (APFM) with constant on-time is proposed for SRC operating in DCM, where the MMFD of transformer core varies linearly with the operating frequency and output voltage among the whole output voltage range. The high-power transformer can be designed according to highest operating frequency and the transformer turns ratio can be designed to be small. Furthermore, the proposed APFM leads to smaller peak current for all switches and fully zero-current-switching can be achieved. The output power and voltage can be still regulated, meeting the high-voltage high-power applications. For the proposed APFM, there are four different driver combinations with exact the same effects and advantages. The theoretical analysis has been validated by the established simulation model and experimental platform.
Highlights
The high-voltage high-power converter is the key unit of highvoltage equipment, for example, the electrostatic precipitator (ESP) and X-ray power generator in environmental protection and medical industry fields [1]–[4]
Bm of the proposed control is proportional to Vo no matter 2Vo/Vin is smaller than n or not, leading to a much smaller Bm when compared to the traditional pulse frequency modulation (PFM) with constant on-time
EXPERIMENTAL RESULTS An experimental platform of high-voltage high-power series resonant converter (SRC) was built for test, as shown in Fig. 13(a), where the four switches are IGBTs of FZ900R12KE4 (1200V/900A) from
Summary
The high-voltage high-power converter is the key unit of highvoltage equipment, for example, the electrostatic precipitator (ESP) and X-ray power generator in environmental protection and medical industry fields [1]–[4]. 4) Stage 3 [t3, t4] (see Fig. 4(c)): Q2 is turned off with ZCS at t3 since the backward resonance is over at that time During this stage, as Vf is lower than Vin, there is absolutely no current flowing in the resonant tank through the paralleled diodes nor the secondary side and vCs keeps unchanged with the value of Vf. Stage 3 can be called the zero current stage. Referring to (13) and (17), it can be found that Bm of the proposed APFM has no such problem with the same Vo. As a result, the transformer can be designed at the highest switching frequency without that large Ae. Q2 is turned on at t1 to provide a backward resonant current path for Stage 2. The first APFM with constant on-time is taken for analysis
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