Switching power supply and control method thereof

Abstract

The invention provides a switching power supply and a control method thereof. In the switching power supply, electric energy received by a control power supply end of a main circuit is from a first starting circuit and a second starting circuit, and the main circuit, the first starting circuit and the second starting circuit take electricity from a direct current bus of an inverter in a system where switching power supply voltage is located; the direct current bus voltage value required for starting control function in the main circuit by the second starting circuit is lower than the direct current bus voltage value required for starting control function by the first starting circuit, so that when the voltage of the direct current bus is smaller than the direct current bus voltage value required for starting the control function in the main circuit by the first starting circuit, the second starting circuit can also provide control power for the main circuit to ensure the start of the control function in the main circuit so as to start the main circuit when the voltage of the direct current bus is low; and when the inverter is shut down for maintenance through the working energy consumption of the main circuit, the safety of maintenance operation in the release of electric energy on the direct current bus is improved.

Description

technical field [0001] The invention belongs to the technical field of power electronics, and more specifically, relates to a switching power supply and a control method thereof. Background technique [0002] The capacitance capacity of the DC busbar in the photovoltaic inverter system is relatively large. For photovoltaic inverters with large power such as 50kW+, the busbar capacitance capacity is at the mF+ level, which will cause the busbar to discharge slowly when the photovoltaic inverter is turned off. , the discharge time is long, which is not conducive to shutdown maintenance. [0003] In order to solve the problem of long discharge time of the busbar capacitance of the photovoltaic inverter, the existing technical solution is to increase the busbar discharge circuit. like figure 1 As shown, when the bus voltage is high, that is, when the voltage difference between the capacitors BUS+ and BUS- is high, the control terminal V of the switch Q2 GS2 The voltage is hig...

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Problems solved by technology

[0004] However, in this solution, an additional power resistor R1 is required for discharge, and the power resistor R1 takes up a large space, which leads to a larger volume of the photovoltaic grid-connected system

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