an AC-DC converter

Abstract

The invention discloses an AC-DC converter, which comprises a diode bridge rectification circuit. The rectification circuit comprises a first bridge arm and a second bridge arm, wherein the first bridge arm consists of diodes D1 and D2; and the second bridge arm consists of switching power tubes Q1 and Q2 which are connected reversely in parallel with a flywheel diode respectively. The AC-DC converter further comprises an inductor L, a capacitor C3, diodes D3 and D4 and capacitors C1 and C2, wherein L is connected between an AC input voltage live wire end and a midpoint of the first bridge arm; D3, C1, C2 and D4 are connected in series and then connected to the output end of the diode bridge rectification circuit in parallel with C3; the anode of D3 is connected with the anode of C3, and the cathode of D3 is connected with the anode of C1; the anode of D4 is connected with the cathode of C2, and the cathode of D4 is connected with the cathode of C3; moreover, a circuit midpoint between C1 and C2 is connected with the midpoint of the second bridge arm. The AC-DC converter provided by the invention can effectively stabilize the voltage of a center point without using a capacitor with a high capacitance value, so the volume and cost of the converter are reduced; moreover, input current harmonic waves are suppressed, thereby achieving more remarkable effect of improving the quality of output voltage.

Description

technical field [0001] The invention relates to the technical field of power supplies, in particular to an AC-DC converter in the power supply. Background technique [0002] AC-DC converters have been widely used in devices such as uninterruptible power supplies (UPS) and switching power supplies that require DC power supply. Generally, AC-DC converters are also called rectifiers. For example, if figure 1 As shown, the figure shows a schematic diagram of the topology of a traditional diode bridge rectifier, which includes the first bridge arm composed of diode D1 and diode D2, and the first bridge arm composed of insulated gate bipolar power transistors (IGBT) Q1 and Q2. The second bridge arm is connected to an AC voltage input at its input end, and converts the AC voltage into a DC voltage output through a diode bridge rectifier circuit. [0003] The traditional voltage doubler rectifier has been widely used because of its simple topology and low cost. Its structure is as...

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Problems solved by technology

However, when using these two topological structures, it can only achieve the purpose of suppressing the input current harmonics to improve the quality of the output voltage, but cannot stabilize the center point voltage of the DC output.

This is because these two topological structures lead to the charge and discharge cycle of capacitors C1 and C2 is determined by the cycle of the input AC voltage, and cannot be completely controlled by the IGBT device

The period of the input AC voltage is usually large, which causes when one of the capacitors is charged, the other capacitor has a longer time for uncontrollable voltage changes, resulting in unstable voltage at the center point

If the purpose of stabilizing the center point voltage is to be achieved, it is necessary to increase the capacitor value at the output end of the above-mentioned AC-DC converter to balance the voltages of capacitors C1 and C2, but this will not only greatly increase the volume and cost of the AC-DC converter, but also Cannot make the center point voltage completely stable

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