Switch transistor voltage drop holding circuit and application of switch transistor voltage drop holding circuit in lithium battery protection circuit

Abstract

The invention provides a switch transistor voltage drop holding circuit comprising a first field effect transistor. The switch transistor voltage drop holding circuit is characterized in that the first input end of the voltage drop holding circuit is connected with the drain electrode of the first field effect transistor, the second input end is connected with the driving signal of the first field effect transistor, the output end is connected with the gate electrode of the first field effect transistor, and the source electrode of the first field effect transistor is grounded. When the second input end is low-level "0", the output end of the voltage drop holding circuit is low-level "0" constantly. When voltage of the first input end and the ground is greater than reference voltage and the second input end is high-level "1", the output end of the voltage drop holding circuit is high-level "1". When voltage of the first input end and the ground is less than reference voltage and the second input end is high-level "1", the output end of the voltage drop holding circuit is low-level "0". Advantages of the switch transistor voltage drop holding circuit are that the circuit structure is simple, and the first field effect transistor is enabled to possess the set voltage drop value constantly under the condition of extremely low load current so that normal conduction and work of the whole lithium battery protection control circuit can be guaranteed.

Description

technical field [0001] The invention relates to a voltage drop maintaining circuit, in particular to a switching transistor voltage drop maintaining circuit and its application in a lithium battery charging and discharging protection circuit. Background technique [0002] During the use of lithium batteries, overcharging, overdischarging or overloading current will affect the service life and performance of the battery. For the sake of safety, the lithium battery cell design must be equipped with a protection circuit to prevent overcharging and overdischarging. or short circuit caused by battery burning, explosion and other dangers. In actual use, people require the protection circuit to consume as little power as possible when there is no load, and it is best not to consume power. [0003] like Image 6 As shown, it is the circuit structure diagram of the lithium battery charge and discharge protection circuit that can be realized at present. When the load current is const...

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Problems solved by technology

[0005] However, in actual work, the load current will vary from thousands of amperes to several milliamps, or even several microamps, and only a fixed value of sampling resistor (usually the sampling resistor is only a few milliohms ) cannot realize the smooth power-gathering work of the protection circuit under all changing load current values

like Image 6 As shown, when the load current of the protection circuit is very small (only a few milliamps or a few microamps), the voltage drop across the transistor Q1 is basically zero at this time, and the gate potential of the first switching tube Q01 cannot When the first switching tube Q01 is turned off, the second switching tube Q02 is also turned off, so that the lithium battery protection control circuit cannot be Electric work; if the sampling resistance is selected to be larger to ensure the conduction of the circuit (in order to reduce the power consumption of the circuit, the sampling resistance is usually not too large), the entire circuit will generate a large power consumption due to the existence of the large resistance, This is contrary to the design concept of the lithium battery protection circuit, which requires the power consumption to be as small as possible.

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