18650 li ion rechargeable battery

　　PFC circuit in switching 18650 li ion rechargeable battery design

　　A few years ago, many 18650 li ion rechargeable battery manufacturers mostly used passive PFC modules in their power products. The PFC module is a filter that reduces harmonic currents and converts nonlinear loads into linear loads. The power factor generated by capacitors and inductors will be closer to unity.

　　Therefore, the next thing to talk about is active PFC and passive PFC circuits. Compared with active PFC, passive PFC has a lower power factor, and passive PFC is only suitable for 230V high-voltage power grid. For 115V low-voltage power grid, passive PFC also requires a voltage doubler to adapt to the grid specifications. However, passive PFC is more efficient than active PFC!

　　For active PFC, it is basically an AC/DC rectifier that controls the current waveform through PWM (Pulse Width Modulation). Initially, the AC voltage is rectified by a rectifier bridge. The PWM then triggers MOSFETs (usually two) in the active PFC circuit, splitting the intermediate DC voltage into a constant pulse train. These pulse signals pass through the filter capacitor and send a relatively smooth current to the main switching circuit. Before that, we will also see a large inductor coil, and this large inductor can buffer and sort out the sudden inrush of current. Of course, the magnetic coil is also an important component in the generation of reactance. In addition, we will also see a thermistor in the active PFC circuit, which is also used to limit the sudden inrush of current, especially when the 18650 li ion rechargeable battery is powered on and started.

　　80Plus requires PFC to exceed 0.9

　　Active PFC circuits usually have two different modes, current discontinuous mode DCM (DiscontinuousConductionMode) and current continuous mode CCM (ContinuousConductionMode). DCM refers to the working state in which the PFC MOSFET is turned on when the inductor current is zero; CCM refers to the working state in which the PFC MOSFET is turned on when the inductor current is always above zero. Therefore, in the MOSFET, all The reverse recovery energy will be wasted.

　　The second mode (CCM) in the power PFC circuit is mainly used for power supplies with a power output exceeding 200W because it can provide relatively low current noise peaks, which means that high-power power supplies can effectively suppress current ripples and output more for a smooth current. However, the disadvantage of CCM is that it consumes higher energy and generates additional EMI when the boost diode is turned off, so we often see an X capacitor added after the power rectifier bridge.

　　Therefore, in current 18650 li ion rechargeable battery products, CCM mode PFC circuits will be used. Although the power consumption is slightly higher and additional EMI will be generated, it can have a higher level of power factor output. Therefore, for large power consumers with high energy consumption, a high power factor 18650 li ion rechargeable battery is very necessary, and it is also very important for the energy saving of the national grid.

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