A switching power supply current detection circuit

Abstract

The embodiment of the present invention relates to a switching power supply current detection circuit, the detection circuit includes: a detection resistor, the first end of the detection resistor is connected to the voltage supply unit, and the second end is connected to the switching power supply circuit through the energy storage unit; the switch selection unit , used to connect the detection resistor to the comparison amplifier unit; the comparison amplifier unit, the output terminal of the comparison amplifier unit is connected to the first end of the switch tube; the switch tube, the second end of the switch tube is connected to the inverting input of the comparison amplifier unit end, the third end of the switch tube is connected to the control unit; the control unit is used to obtain the detected current value; the feedback unit is connected to the third end of the switch tube to form the negative feedback of the comparison amplifier unit. The current detection circuit and method of the present invention are not affected by the manufacturing process. Through the method of digital calibration, the voltage caused by non-ideal factors such as operational amplifiers and MOS tubes at the input end of the comparison amplifier unit is eliminated, so that the detection circuit works approximately in an ideal state. , high detection accuracy.

Description

technical field [0001] Embodiments of the present invention relate to the technical field of switching power supplies, in particular to a switching power supply current detection circuit. Background technique [0002] In the design of switching power supply, the design of the current detection circuit is very important. In order to ensure the stable output voltage of the switching power supply and perform overload protection, the current is usually collected by the current detection circuit and fed back to the switching power supply control circuit to realize the closed-loop control of the circuit. [0003] At present, the use of MOSFET as a current detection method has been more and more widely used. As a multi-sub device, MOSFET has resistance characteristics when it is turned on. The method of detecting the voltage drop of the power tube is to detect the voltage on the MOSFET on-resistance current purpose. [0004] The circuit implementation of the power tube voltage dro...

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Problems solved by technology

[0008] It can be seen from the above formula that RDS is affected by μ, C OX , V T The impact of the on-resistance of the MOSFET is greater, that is, the on-resistance of the MOSFET is greatly affected by the manufacturing process, and the current manufacturing process of the power tube cannot avoid the deviation of the above parameters, so the detection accuracy of the current detection circuit using this method is low

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