An Input Undervoltage Protection Type Constant Current Power Supply

Abstract

The invention discloses an input undervoltage protection type constant-current power supply. An input undervoltage protection circuit is provided and coupled between a power circuit and an outer net power supply, and when the input voltage of the outer net power supply is lower than a set value, a switching power supply is powered off. When the input voltage is normal, the input end of an OR-NOT circuit U4 is in a low level, the low level is output by the OR-NOT circuit U4, a protection circuit does not act, a normally closed contact of a relay K1 is closed, and the switching power supply works normally. When the input voltage is lower than 85 V, the resistance voltage division value is reduced to the low level, at this moment, the low level is input to the OR-NOT circuit U4 inputs, a high level is output, a triode Q7 is in saturation conduction, a coil of the relay K1 is powered on, the normally closed contact of the relay K1 is disconnected, the switching power supply is powered off, a switching power supply circuit is protected, and the aim of fast cutting off power supplying to protect the power supply under low voltage is achieved.

Description

technical field [0001] The invention relates to a power supply circuit, in particular to an input undervoltage protection type constant current power supply suitable for the power supply of LED lighting lamps, and belongs to the field of electronic technology. Background technique [0002] At present, the traditional LED power supply circuit includes a power supply circuit 1 , an output circuit 2 , an amplifier circuit 4 , a sampling circuit 5 , a drive control circuit 6 , a constant voltage constant current circuit 7 and a PFC correction circuit 8 . [0003] During the process of realizing the present invention, the inventors found at least the following problems in the prior art: most of the existing LED power supplies are wide power supplies, and the input voltage range is AC85-265V. However, in practical applications, the power supply conditions of the power grid are often very poor, sometimes falling below 85V, and the power supply can still work at this time, but the w...

AI Technical Summary

Problems solved by technology

At present, although there are undervoltage protection circuits, these protection circuits have low sensitivity and slow response, which will still cause the power supply circuit to burn out.

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