Soft start method and system for charging vehicle-mounted power supply

Abstract

The invention discloses a soft start method and system for charging a vehicle-mounted power supply. The method comprises the following steps: acquiring mains supply sampling voltage; determining positive and negative zero crossing moments of the mains supply according to positive and negative sampling voltages; when the sampling voltage instantaneous value at the first forward zero-crossing momentis less than the voltage threshold value, driving the CLLC at the highest frequency in the first power frequency period; after the second forward zero-crossing moment starts, decreasing the wave sending frequency progressively, and driving the CLLC to operate; when the wave sending frequency is decreased progressively to the resonant frequency, starting the delay counting; and when the delay counting duration reaches the duration threshold value, completing the soft start. When low voltage is input, soft start is started according to the sine slope of mains supply voltage, overcharge voltageis avoided, and loss of electronic devices caused by large impact current generated by high voltage is avoided; in addition, the lower setting of the highest switching frequency improves the reliability and anti-interference performance of driving.

Description

technical field [0001] The invention relates to the field of electronic power, in particular to a soft start method and system for charging a vehicle power supply. Background technique [0002] Slow charging is to directly connect alternating current (AC) to electric vehicles, and then charge the battery pack after converting the alternating current (AC) to direct current through the on-board charger. The on-board charger is equipped with a power factor correction (powerfactor correction, PFC) module and a direct current-direct current converter (DC-DC). After the PFC module converts the incoming AC power into a DC bus voltage, the DC- The DC converter converts the DC target voltage into high-voltage DC to charge the battery pack. [0003] The DC-DC converter works at the resonant frequency to get the best efficiency. But when starting, if starting directly at the resonant frequency point, since the resonant impedance is 0 and the filter capacitor on the output side is usu...

AI Technical Summary

Problems solved by technology

In the traditional CLLC topology charging circuit, the input is the DC bus voltage. When the DC bus voltage is relatively high (390Vdc-680Vdc) input, the soft-inspired wave frequency is designed to be the highest frequency at 3 times the resonance frequency. However, the higher start-up frequency It will bring the following problems: First, to realize high-frequency pulse width modulation (Pulse Width Modulation, PWM), the requirements for the reliability and anti-interference of the drive circuit are high, which increases the cost; second, the time from the starting frequency to the resonance frequency longer, resulting in longer start-up times

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