Design Method of 6-Element Boundary Gain for LLC Resonant Converter of Electric Vehicle

Abstract

In the application of on-board chargers, LLC resonant converters need to work in multiple operating modes to achieve wide-range output requirements. For the most commonly used single-phase and three-phase LLC topologies, the time domain expressions of all possible operating modes are introduced to predict voltage and current behaviors. Based on the mode analysis, the 6-element boundary gain design method is proposed to design a wide gain range LLC resonant converter. The resonant current is used as the basis for ZVS judgment and the transformation trend of ZVS in the full operating range is given. Through reasonable distribution of the boost region and the buck region, the resonant devices can be designed more appropriately to achieve lower conduction loss and higher efficiency. Finally, the prototypes of 3.3kW and 6.6 kW are built to verify the theoretical analysis of the method in single-phase LLC and three-phase LLC. INDEX TERMS LLC resonant converter, Zero-voltage switching, wide range output, battery charger, electric vehicle.

Inductor-Aid Step-Up LLC Resonant Wireless Power Transfer

“…Figure. 19 indicates the switching ON process of S5, S6, which conduct to boost up the output voltage. Benefits from the primary control, zero-current detection is unnecessary to outset the higher voltage power transmission.…”

“…It concluded that the accuracy of FHA is higher when the system operates under a low quality factor and near the compensated resonant frequency. FHA has been widely examined and used in many applications, included the closed-loop control converter, bidirectional DC-DC converter, wide output vehicle chargers with power factor correction, and waterproof vessel wireless charger due to the high accuracy, simple design process, and control strategy [19][20][21][22][23]. Many subtle control methods such as the closed-loop design and the frequency doubler method to raise the output power based on FHA have been investigated in LLC non-WPT system area [24], [25].…”

A Review of Bidirectional On-Board Chargers for Electric Vehicles

“…A half-bridge LLC converter, as shown in Fig. 5 (a), can achieve a 10kW bidirectional power flow with 96% efficiency when it is controlled with a variable switching frequency [105]- [107]. A variable DC-link voltage of the AC/DC converter can maximize the efficiency of secondend stage.…”

A High Power Interleaved Parallel Topology Full-Bridge LLC Converter for Off-Board Charger

“…In this two-stage converter, a boost AC-DC converter is used as a power factor correction (PFC) module to isolate harmonic pollution from the grid and provide pure supply of direct voltage to the next stage module. In addition, an isolated DC/DC converter is used to directly handle complex load conditions to accommodate the linear load characteristics and wide adjustable output voltage range of the EV's high-voltage battery [9]. Therefore, the characteristics of this two-stage converter are largely influenced by the DC/DC converter, which means that the design of the DC/DC converter is particularly important for off-board chargers.…”