Duplicate supply selection circuit

Abstract

The invention provides a duplicate supply selection circuit, relates to the field of analog integrated circuits and aims at solving the technical problem of selecting a power source with high voltage value for power supply in the situation that two power sources are connected simultaneously. The duplicate supply selection circuit includes a bias circuit, a duplicate supply voltage comparison circuit and a power selection circuit; the input of the bias circuit is a first supply voltage and a second supply voltage, and the output is a bias voltage; the input of the duplicate supply voltage comparison circuit is the first supply voltage, the second supply voltage and the bias voltage, and the output is a comparison signal; and the input of the power selection circuit is the first supply voltage, the second supply voltage and the comparison signal, and the output is a selection voltage that is a supply voltage with a higher voltage value of the first supply voltage and the second supply voltage. The selection circuit can be applied in the circuit of a lithium ion battery charger.

Description

Dual power supply selection circuit Technical field The invention relates to the field of analog integrated circuits, in particular to a dual power supply selection circuit. Background technique In the circuit design, when two power supplies supply power at the same time, the power supply needs to be selected. If the power supply cannot be selected normally, the components may be damaged. Take the lithium ion (Li-ion) battery charger as an example. As the linear charging chip of the lithium ion battery becomes more and more integrated, the charging power transistor (PMOS) is also integrated into the linear charger. In order to reduce the size of the charger and reduce production costs, CMOS technology is preferred. When charging the lithium-ion battery, the charging power tube is connected to two power sources at the same time, namely the charging power source and the load (the battery to be charged). When the charger is powered on, the voltage of the rechargeable battery ...

AI Technical Summary

Problems solved by technology

When the battery voltage is lower than the power supply voltage, the reverse-biased diode (Diode) in the physical device structure of the PMOS transistor is forward-conducting, which will damage the charger chip and cause the charger to fail to work normally.

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