A DC switching power conversion circuit with step-down and step-up functions

Abstract

The invention discloses a DC switching power supply conversion circuit with step-down and step-up functions, belonging to the technical field of switching power supplies, comprising an input positiveelectrode, an input negative electrode, a step-up and step-down voltage control terminal, a PWM control terminal, resistors R1, R2 and R3, diodes D1, D2, D3, D4, D5, operational amplifiers N1A and N1B, an inductor L1, a capacitor C1, an N-channel field effect transistor V2, a P-channel field effect transistor V1, an output negative electrode and an output positive electrode. When the input level of the step-up and step-down control terminal is low, the forward input terminal of the operational amplifier N1B can be pulled low through the diode D5, so that the circuit operates in the BUCK step-down mode; When the input level of the step-up and step-down control terminal is high, the reverse input terminal of the operational amplifier N1A can be pulled high through the diode D4, so that the circuit operates in a BOOST step-up state. The invention realizes the step-down and step-up functions, and has the advantages of good practicability, high economy and high efficiency.

Description

technical field [0001] The invention relates to the technical field of switching power supplies, in particular to a DC switching power conversion circuit capable of stepping down or boosting voltage. Background technique [0002] Switching power supply is a kind of power supply that uses modern power electronic technology to control the time ratio of switching on and off to maintain a stable output voltage. The switching power supply circuit has the characteristics of low power consumption, high conversion efficiency, small linear change, and stable operation, so it is widely used in various electronic equipment such as industrial control, communication office, and home consumption. [0003] The most common non-isolated switching power supply conversion methods in switching power supplies are BUCK step-down conversion and BOOST step-up conversion. Less commonly used are BUCK-BOOST step-down step-up and SEPIC single-ended primary inductance conversion. [0004] In the existi...

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Problems solved by technology

[0004] In the existing non-isolated switching power supply conversion methods, the simple BUCK conversion circuit can only realize step-down conversion, while the BOOST conversion circuit can only realize boost conversion. When the output voltage fluctuation range is large or the load voltage change requirement is large, In some applications, it will not be applicable. For example, some multi-functional lithium-ion battery chargers are required to be able to charge 1 to 6 series-connected lithium-ion batteries. The input power is a common power supply in the market, and the input voltage range is 7V~ 19V, the product requires not only charging 1 lithium battery in series (charging voltage 4.2V), but also charging 6 lithium-ion batteries in series, the charging voltage is 25.2V, then a charger will be needed The internal conversion circuit can both step down and boost the voltage, and neither the BUCK conversion circuit nor the BOOST conversion circuit can meet the requirements.

However, if the BUCK-BOOST buck-boost topology is used, because its input voltage and output voltage are inverse phase, and the input and output do not share the same ground, the voltage and current control will become very complicated and difficult to apply; if If the SEPIC single-ended primary inductance conversion circuit is used, although it can achieve the purpose of both stepping up and stepping down, because two inductors and one capacitor are needed for energy transfer in the circuit, the control circuit is complicated and there are many power devices. , the loss is large, the conversion efficiency is not high, and the electromagnetic interference generated will be large, so SEPIC circuits are rarely used in practical applications

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