Introduce the topology of lithium-ion battery chargers for electric vehicles

The topological structure of the lithium-ion battery charger for electric vehicles can be seen from the current 18650 lithium-ion battery. The charging process in the normal charging mode is generally carried out in homes and public places. The charging power of the normal charging mode is usually 6.6kw, and the typical charging time is 5-8 hours. The normal charging mode is similar to the charging power converter in the emergency charging mode. The normal charging method can also use a single-stage AC/DC converter. However, due to the single-stage converter with PFC function, the peak current of the switch tube is very large. In the two-stage converter, the PFC can use a traditional boost boost circuit, and the switch tube can be a soft switch or a hard switch. However, in order to improve efficiency, a soft-switching boost converter should be selected. The traditional AC/DC full-wave rectifier circuit uses a rectifier + capacitor filter circuit. The circuit is a combination of non-linear devices and energy storage elements. The waveform of the input AC voltage is sinusoidal, while the waveform of the input current is severely distorted and pulsed. The resulting harmonic current is harmful to the power grid and reduces the power factor of the power supply. In this design, the rectifier circuit part adopts an active power factor correction circuit. Unlike a typical PFC main circuit, this circuit uses a lossless absorption buffer network. The exchange loss is reduced, the stability of the network is improved, and the service life of the network is prolonged. A group of passive components are used to make the switch tube realize zero current switching and zero voltage switching, which improves the working efficiency of the power supply and reduces the production cost compared with other resonant soft switching circuits. 1. The single-phase three-level PFC circuit is shown in Figure 10-15(a). The three-level inverter arm clamped by the diode can also be the same as the traditional two-level inverter arm, with appropriate modifications , Can be divided into three-level inverter arm and boost circuit. Because the boost circuit has the advantages of continuous input current, simple topology, high efficiency, etc., it often becomes the first choice for single-phase PFC circuit topology. However, due to the boost characteristics of the boost circuit, in the case of 220V AC input, the output voltage is usually controlled at about 400V. If the input voltage is further increased and the boost ratio remains unchanged, the corresponding output voltage will also increase. Or if the input voltage is constant, you want a high output voltage. This means that the power components in the boost circuit have to withstand voltage stress exceeding 400V. On the one hand, the switching loss and on-state loss of the device are added; on the other hand, when the voltage rises to a certain level, it will bring difficulties to the selection of the device, which becomes a single-phase PFC circuit that requires high-voltage and high-frequency operation. A difficult contradiction to resolve. Therefore, the single-phase three-level boost circuit provides a good way to solve this contradiction. The three-level control has the following characteristics: (1) The three-level topology can effectively solve the problem of low voltage of power electronic devices, because the switching voltage that each switching device can withstand is only half of the DC side voltage, so it is suitable for high voltage , High-power occasions. In a three-level topology, a single bridge can output three levels, and the line voltage has more steps to simulate a sine wave, which reduces the distortion of the output waveform, thereby greatly reducing the harmonics. (3) The multi-level voltage step wave is reduced, so that the influence of insulation on the load is reduced. (4) The three-level PWM method moves the first group of harmonic distribution bands to a frequency band twice the switching frequency, and the inductance of the load can be used to better suppress the influence of higher harmonics. The three-layer topology can have a 3×3×3 (that is, 27) space voltage vector. Compared with the two-layer topology, the space voltage vector is greatly increased. The addition of the vector brings the freedom of the harmonic elimination algorithm, and a good output waveform can be obtained. 2. Although the single-phase three-level passive lossless soft switching PFC circuit has a three-level PFC topology, the output voltage under the same conditions, the voltage stress of the switching tube is reduced by half, so that the corresponding state loss and switching loss are less, but when switching The frequency is higher and the loss is considerable. Therefore, it is still necessary and meaningful to use soft switching technology to further improve efficiency. Softswitch technology can be broadly divided into active softswitch technology and passive softswitch technology. So, for the general lithium-ion battery manufacturer. Active snubber circuit, RCD snubber circuit, resonant converter, passive non-destructive snubber circuit Statement: Some pictures and content of the articles published on this site are from the Internet. If there is any infringement, please contact to delete the previous article: Ni-MH battery and Ni-Cd battery , The difference between lithium-ion batteries