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A Microcontroller-Based High Efficiency Critical Conduction Mode Control for GaN-Based Totem-Pole PFC

Hardware prototype
Fig. 1. 2.2kW two-phase interleaving GaN-based CRM totem-pole PFC prototype
  Power factor correction (PFC) rectifiers are widely used in electric vehicle (EV) chargers and in the power supplies for telecom or data center in order to achieve unity power factor (PF) and to restrain total harmonic distortion(THD). The totem-pole PFC rectifier is well known for its simple topology. Recently, the totem-pole PFC rectifier has become popular again with the help of the high voltage Gallium-Nitride (GaN) high-electron-mobility-transistor (HEMT).

  In this paper, a microcontroller-based control method for the GaN-based critical conduction mode (CRM) totem-pole PFC is proposed. A simple digital control method based on synchronous rectifier (SR) on-time calculation which ensures zero-voltage switchign (ZVS) without zero current detection (ZCD) is proposed. Average current mode control is discussed and a compensator gain adjustment method is introduced to improve PF and restrain THD. Finally, all control functions are integrated in a microcontroller unit (MCU) and demonstrated on a 2.2 kW GaN-based two-phase interleaved CRM totem-pole PFC prototype as shown in Fig. 1. Fig. 2 shows the control diagram.

  The prototype with proposed control method can reach a peak efficiency of 98.96% and full load efficiency of 98.55%. The converter reaches a PF of 0.996 at full load.
Control diagram
Fig. 2. Micro-controller based average current mode control with SR on-time calculation in a GaN-based two-phase interleaved CRM totem-pole CRM PFC

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