20 POWER CONVERSION www.epc-co.com Issue 2 2023 Power Electronics Europe www.power-mag.com A high efficiency, 3 kW capable, 2-phase, 3-level Converter using paralleled eGaN® FETs Jianglin Zhu, Michael de Rooij, Efficient Power Conversion As the revolution of renewable energy as well as transportation electrification progresses, the need for residential energy storage systems is increasing. A high efficiency DC-to-DC converter is usually required to exchange energy generated from renewable sources, such as solar panels, with a battery. The fast-switching speed and low RDS(on) of gallium nitride (GaN) FETs can help save energy by reducing power consumption inside the DC-to-DC converter[1]. This article shows how to design a high efficiency 100 – 250 V to 40 - 60 V DC-to-DC converter taking advantage of the low RDS(on) of the EPC2215. A 3-level flying capacitor topology offering a 2x reduction of voltage and current stresses, which improves overall efficiency, is employed. Advantages of a 3-level Buck or Boost Converter The 3-level flying capacitor buck or boost converter is an attractive topology as it allows for a 2x reduction in FET voltage stress and volt-seconds stress on the inductor, as well as 4x inductance reduction compared to a conventional twolevel converter with the same current ripple [2]. Figure 1 shows the operation of the 3-level converter operating in buck mode. One top switch and one bottom switch forms two complementary switch pairs Q1/Q4 and Q2/Q3. Top switch Q1 and Q2 operate at the same duty cycle but have a 180° phase shift between them, while the bottom switch Q3 and Q4 operate at a complementary duty cycle. The conventional current mode control can still be applied for this converter, as shown in figure 2. In such configuration, the output voltage loop generates the reference for the inner current loop. To ensure the switches have even voltage stress (0.5·Vin ) when the switch is off, an additional flying capacitor voltage loop is added to actively regulate the flying capacitor voltage, this can be achieved by adjusting the charging and discharging period of the flying capacitor [3]. Design Validation A 3 kW capable experimental 2-phase (1.5 kW per phase) 100 V – 250 V input and 40 V - 60 V output 3-level DC-to-DC Figure 2: Block diagram of output voltage and flying capacitor voltage balancing control loop. Figure 1: Operation principal of the three-level converter when Vout /Vin <0.5.
RkJQdWJsaXNoZXIy MjQ0NzM=