Abstract
The GaN-based critical conduction mode (CRM) totem-pole power factor correction (PFC) converter with full-line-cycle zero voltage switching (ZVS) is a promising candidate for high-efficiency front-end rectifiers. However, the input current can be degraded by line-cycle current distortion and ac line zero-crossing current spikes, and maintaining reliable ZVS control is difficult in noise-susceptible high-frequency environments. In this paper, a detailed analysis of the current distortion issues in a GaN-based CRM totem-pole PFC with digital ZVS control is provided, and effective approaches are proposed to mitigate different kinds of current distortion and ensure stable ZVS control under high-frequency operation. The proposed solutions have the advantages of straightforward implementation and do not increase the control complexity. The current distortion issues are demonstrated in two GaN-based CRM totem-pole PFC prototypes, a 1.5 kW PFC for data centers and a 100 W PFC in a 6.78 MHz wireless charging power supply for consumer electronics. The proposed methods are experimentally verified with effective mitigation of the current distortion and improvement of the converter power efficiency.
Highlights
Power factor correction (PFC) converters are widely used in power supplies to satisfy requirements on power factor and harmonics
With a focus on the GaN-based CRM totem-pole PFC with digital zero voltage switching (ZVS) control, this paper investigates the root causes of the current distortion and systematically addresses them
For PFC_DC, the line-cycle current distortion is mainly caused by the ZCD signal propagation time delay, and the ac line zero-crossing current spike is mostly due to the noise current generated from the switching dv/dt of Si devices (S3, S4)
Summary
Power factor correction (PFC) converters are widely used in power supplies to satisfy requirements on power factor and harmonics. For the low-frequency line-cycle current distortion, to compensate the current sensing propagation time delay, [27] subtracts Tdelay from the time difference Tneg between the two inductor current zero-crossing points based on the numerical relationship Tdelay < Tneg This method is not applicable for a high-frequency PFC converter with much smaller boost inductance because Tneg is comparable to or even smaller than Tdelay. Soft transition approaches are proposed by turning on the GaN devices after each zero-crossing with gradually increased duty cycle or fixed small duty cycle [24], [26], [33] These soft transition methods are either complicated or difficult to control precisely, and cannot be directly applied on the GaN-based high-frequency CRM totem-pole PFC with ZVS control.
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