Precharge system and method

A precharge system, comprising a load circuit, a precharge circuit and a control circuit, wherein the load circuit comprises an input terminal, an input switch and a bus capacitor, the input terminal is configured to receive an input current, the input switch is coupled between the input terminal and the bus capacitor, and the precharge circuit is connected in parallel to the input switch and comprises a precharge resistor and a precharge switch connected in series,

• wherein the control circuit is configured to control the input switch to be in an off state and control the precharge switch to switch between an on state and an off state for multiple times during the load circuit being in a precharge mode, and the control circuit is configured to control the input switch to be in an on state during the load circuit being in a work mode,
• wherein when the precharge switch is in the on state, a consuming power of the precharge resistor is larger than a threshold power and is smaller than or equal to a limit power of the precharge resistor, the input current flows through the precharge resistor to charge the bus capacitor, and a bus voltage on the bus capacitor increases, and when the precharge switch is in the off state, the consuming power of the precharge resistor is zero, and the bus capacitor stops being charged,
• wherein when the precharge switch is controlled to switch between the on state and the off state, the threshold power is adjusted dynamically,
• wherein the threshold power is determined according to the times of switching the precharge switch between the on state and the off state, a time length of the precharge switch being in the on state each time, a time length of the precharge switch being in the off state each time, a temperature coefficient of the precharge resistor, and a condition of dissipating heat.