A voltage selection circuit and method

Abstract

The invention discloses a voltage selection circuit and method. The voltage selection circuit comprises a peak current source circuit, a hysteresis comparison circuit and a voltage output circuit, wherein the input end of the peak current source circuit is connected with a power supply voltage, and the output end of the peak current source circuit is connected with the hysteresis comparison circuit and used for generating a bias current source; the input end of the hysteresis comparison circuit is connected with a first input voltage source and a second power supply voltage, and the output endof the hysteresis comparison circuit is connected with the voltage output circuit and used for generating a logic level; and the voltage output circuit outputs the first input voltage source or a second input voltage source selectively according to the logic level. According to the voltage selection circuit and method, in order to quickly and accurately select the lower voltage or the higher voltage of the two voltage sources as the output voltage, the peak current source circuit provides a bias current, so the static power consumption of the circuit is low; the hysteresis comparison circuitof the source end input eliminates the Miller effect of parasitic capacitance, and the circuit has the advantages of being high in response speed, high in anti-noise interference capacity and the like; and in addition, the structure of the voltage selection circuit is simple, and the chip area is saved.

Description

technical field [0001] The invention belongs to the technical field of analog integrated circuits, and more specifically relates to a voltage selection circuit and method. Background technique [0002] In the technical field of analog power supplies, a voltage selection circuit is often used to compare two input voltages, so as to select the higher or lower input voltage as the output voltage. For example, an LDO circuit with a reverse input current protection function often includes a voltage selection circuit inside to ensure that the substrate potential of the power transistor is always at an appropriate potential during operation. Otherwise, when the input voltage suddenly loses power, the output voltage spikes and other abnormal conditions occur, the parasitic body diode in the power tube may be turned on, resulting in the phenomenon of current backflow, which will cause great damage to the chip itself and the power supply battery. damage. [0003] figure 1 Shown is ...

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Problems solved by technology

[0004] Aiming at the defects of the prior art, the object of the present invention is to provide a voltage selection circuit and method, aiming at solving the problem in the prior art that when the two input power supply voltages are relatively close, the proper input power supply voltage cannot be correctly selected as the output

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