The on-board charger refers to the charger that is fixedly installed on the electric vehicle. Its main function is to fully charge the power battery of the electric vehicle safely, quickly and conveniently.
According to the charging method of electric vehicles, charging can be divided into two categories: AC charging and DC charging.
Vehicle chargers generally have the following interfaces: AC input terminal, which is connected to the connector coming in from the AC charging socket; DC output terminal, the part where the vehicle charger outputs to the battery; low voltage control interface, the low voltage interface between the vehicle charger and the BMS and external connections; Liquid cooling input and output runner interface, the part where the coolant flows into and out of the charger.
In terms of the charging power supply module, it is divided into rectification, PFC, and DC/DC transformation.
From another perspective, we can also divide the car charger into the main circuit power supply part and the charging control board.
Among them, the charging control board mainly controls, monitors, measures, calculates, corrects, protects, and communicates with the external network of the power supply. It is the "central brain" of the vehicle charger.
The main function of the power supply part is to convert 220V alternating current into more than 300 volts of direct current, and the power supply part is divided into two parts: PFC and LLC.
The first part is the input filter (EMI filter), which is a very important means of suppressing EMC for on-board chargers.
Let's talk about the PFC circuit: from AC to DC, there is an included angle between the AC voltage and the current, and the capacitance of the included angle will cause grid waves, which will affect the efficiency in the middle. Because there is an included angle in the middle. This included angle is the CSIN value.
PFC is a voltage divider circuit. Now, in order to improve the efficiency of the whole system, the new structure of bridgeless PFC is often used to work directly.
Bridgeless PFC efficiency can be significantly improved, but it will cause common mode and noise, so the actual design needs to improve the heat dissipation and PFC board.
The phase-shift controlled full-bridge PWM converter is one of the most commonly used medium and high power DC/DC converter circuit topologies.
The phase-shift PWM control method uses the junction capacitance of the switch tube and the leakage inductance of the high-frequency transformer or the primary series inductance as resonant components so that the switch tube can be turned on and off at zero voltage, thereby effectively reducing the switching loss and the switching noise reduces the electromagnetic interference generated in the switching process of the device, and provides good conditions for the converter to increase the switching frequency, improve the efficiency, reduce the size and reduce the quality.
In the DC/DC part, in order to improve the efficiency, LLC resonance is usually used to realize ZVS and ZCS, and finally achieve high efficiency.
The topology of LLC must require a high switching frequency in order to reflect its advantages, usually COOL-MOS or MOSFET with SIC.
The development direction of on-board chargers is miniaturization and lightweight, and the entire power level has also begun to shift from 3.3kW to 6.6kW. In the future, in the development of single-phase AC to three-phase AC, the low price of 11kW and 21kW is also a core trend.
The development of new energy vehicles is the key to solving environmental pollution and energy crises, promoting the transformation and upgrading of my country's automobile industry, and realizing the leap-forward development of my country's automobile industry from large to strong. The technological development of on-board chargers provides strong support for the practical and popularization of new energy vehicles.
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