Alternating current-to-direct current circuit

Abstract

The invention discloses an alternating current-to-direct current circuit. The circuit comprises a rectification circuit, a BUCK circuit and a voltage detection control circuit, wherein the voltage detection control circuit is provided with a first preset valve used for limiting the lowest work voltage of the BUCK circuit and a second preset valve used for limiting the highest work voltage of the BUCK circuit, and is used for respectively detecting an instantaneous value of pulsating direct current and a voltage value of a low-voltage output end; the voltage detection control circuit outputs a PWM (pulse-width modulation) signal to control the BUCK circuit to work when the instantaneous value of the pulsating direct current is more than the preset vale and less than the second preset valve, and the output voltage Vout of the low voltage output end is less than a third preset value; and when the instantaneous value of the pulsating direct current is more than the second preset value, the voltage detection control circuit controls the BUCK circuit to stop working. The alternating current-to-direct current circuit has the advantages that the BUCK circuit works in a low voltage part of the pulsating direct current by limiting the highest work voltage of the BUCK circuit, so that the efficiency is improved, the circuit does not use high-voltage electrolytic capacitor, and the efficiency is high.

Description

technical field [0001] The invention relates to an AC-to-DC circuit, in particular to an AC-to-DC circuit applied in a low-power AC / DC power supply. Background technique [0002] There are many AC to DC circuits, which can be realized with a rectifier circuit. Industrial and civil power supply generally adopts AC power supply. Taking civilian use as an example, my country uses 220VAC / 50Hz, America uses 120VAC or 110VAC, and the frequency is 60Hz, while the United Kingdom uses 240VAC / 50Hz. Other countries and regions are also different. Generally speaking Come, there are two types of frequency: 50Hz or 60Hz, and the working voltage is about 110V and 220V. Its characteristic is that the direction of the amplitude of the voltage (or current) changes periodically with time, such as figure 1 shown. [0003] figure 1 The alternating current that changes sinusoidally over time is called alternating sinusoidal voltage, and the time required for one change is called the cycle of al...

AI Technical Summary

Problems solved by technology

[0010] The common BUCK circuit is used in the occasion of pulsating DC input. When the voltage of the input pulsating DC reaches the peak value, the duty cycle reaches the minimum, the switching loss is large, and there are disadvantages of low circuit efficiency and large loss.

[0011] "An AC-to-DC Circuit" of Chinese Patent Application No. 201210056555 shows an AC-to-DC circuit for low-power applications. It is used for applications with output power above 3W, and it also has many current harmonics and low efficiency. shortcoming

[0014] For the two-stage scheme of using BOOST's PFC plus DC / DC, there are also disadvantages of complex circuits and high costs.

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