Method for switching main power supply and backup power supply and switching circuit

Abstract

The invention discloses a method for switching a main power supply and a backup power supply and a switching circuit. The switching circuit comprises a main power supply switch, a backup power supply switch, a first switch control logic to a fourth switch control logic, a main power supply detection circuit and a switch control signal generation circuit, wherein, the main power supply switch comprises a first PMOS pipe and a second PMOS pipe; the first PMOS pipe and the second PMOS pipe are connected in series between the main power supply and an output node; the backup power supply switch comprises a third PMOS pipe and a fourth PMOS pipe; the third PMOS pipe and the fourth PMOS pipe are connected in series between the output node and the backup power supply; and the switch control signal generation circuit determines connection and stop of the first PMOS pipe to the fourth PMOS pipe according to input of the main power supply detection circuit. Independent substrates of the PMOS pipes are generated through a mode of cross coupling, which not only can avoid substrate creepage, but also can meet the requirement of respectively connecting and stopping two serially connected PMOS pipes.

Description

technical field [0001] The invention relates to a dual power supply system with a backup power supply, in particular to a dual power supply system capable of seamlessly switching between the main power supply and the backup power supply by controlling a MOS switch when the main power supply drops or recovers. Background technique [0002] With the development of science and technology, more and more equipment and precision instruments, such as communication terminal equipment, bank computer systems, surgical equipment and many high-precision instruments for measurement, need an uninterrupted and stable working power supply. Based on this These devices and instruments often have two or more power supplies to power them, one of which is the main power supply, and the rest are secondary power supplies. When the system works normally, the internal voltage of the system is usually provided by the main power supply, and the auxiliary power supply is disconnected from the system; w...

AI Technical Summary

Problems solved by technology

However, the shortcoming of this patent is that M201, M202, M203 and M204 series switches must be turned on and off at the same time, otherwise leakage through the parasitic diode of the PMOS substrate may occur. For example, when VDD=VBAT, if the switch M202 is turned off, but the switch M201 is turned on, Then when VDD>VSYS, VDD will leak to VSYS through the substrate diode of the switch M202, and in some specific applications, such a control logic that is not on and off at the same time may be required; second, when VDD is too low, the switch switches The output of the control circuit may not be correct, that is to say, even if VSYS recovers at this time, the control circuit may not be able to give correct information, switch the switch to use VSYS for power supply

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