US-12627238-B2 - Power conversion circuit with voltage balancing

US12627238B2US 12627238 B2US12627238 B2US 12627238B2US-12627238-B2

Abstract

A power conversion circuit, includes the following elements. A transformer, includes a primary side winding, a first secondary side winding and a second secondary side winding. A first switching circuit, connected to the primary side winding. A second switching circuit, connected to the first secondary side winding. A third switching circuit, connected to the second secondary side winding. A first output capacitor, connected to the second switching circuit and the first secondary side winding, and has a first voltage value. The second output capacitor, connected to the third switching circuit and the second secondary side winding, and has a second voltage value. A control circuit, controls the first switching circuit, the second switching circuit and the third switching circuit to be turned-on or turned-off according to the first voltage value and the second voltage value, so as to charge the first output capacitor or the second output capacitor.

Inventors

Ting-Fu NI

Assignees

LITE-ON TECHNOLOGY CORPORATION

Dates

Publication Date: 20260512
Application Date: 20231227
Priority Date: 20230411

Claims (9)

1 . A power conversion circuit, comprising: a transformer, comprising a primary side winding, a first secondary side winding and a second secondary side winding; a first switching circuit, connected to the primary side winding; a second switching circuit, connected to the first secondary side winding; a third switching circuit, connected to the second secondary side winding; a first output capacitor, connected to the second switching circuit and the first secondary side winding, the first output capacitor has a first voltage value; a second output capacitor, connected to the third switching circuit and the second secondary side winding, the second output capacitor has a second voltage value; and a control circuit, electrically connected to the first switching circuit, the second switching circuit and the third switching circuit, wherein, the control circuit controls the first switching circuit, the second switching circuit and the third switching circuit to be turned-on or turned-off respectively according to the first voltage value and the second voltage value, and to charge the first output capacitor or the second output capacitor, wherein when the first voltage value of the first output capacitor is greater than the second voltage value of the second output capacitor, the control circuit controls the second switching circuit and the third switching circuit to be turned-on, the second secondary side winding charges the second output capacitor and the second switching circuit is bi-directionally conducted, and wherein when the third switch is turned-on, the third switching circuit is bi-directionally conducted, and when the third switch is turned-off, the third switching circuit is uni-directionally conducted.
2 . The power conversion circuit according to claim 1 , wherein the first output capacitor is connected to the second output capacitor in series, and the first output capacitor and the second output capacitor are connected to a load circuit, or the first output capacitor and the second output capacitor are respectively connected to a load circuit.
3 . The power conversion circuit according to claim 1 , wherein a turns number of the first secondary side winding is the same as a turns number of the second secondary side winding.
4 . The power conversion circuit according to claim 1 , wherein the control circuit controls the first switching circuit to be turned-off during a first period and controls the second switching circuit to be turned-on, and during a second period the first switching circuit is controlled to be turned-on and the second switching circuit is controlled to be turned-off, and the first period does not overlap the second period.
5 . The power conversion circuit according to claim 1 , wherein the first switching circuit, the second switching circuit and the third switching circuit respectively have a first switch, a second switch and a third switch, the first switch is electrically connected to the primary side winding and the control circuit, the second switch is electrically connected to the first secondary side winding and the first output capacitor, and the third switch is electrically connected to the second secondary side winding and the second output capacitor, wherein when the second switch is turned-off, the second switching circuit is uni-directionally conducted.
6 . The power conversion circuit according to claim 1 , wherein when the control circuit controls the first switching circuit to be turned-on, the primary side winding resets a magnetic field of the transformer.
7 . The power conversion circuit according to claim 1 , wherein when the first voltage value of the first output capacitor is less than the second voltage value of the second output capacitor, the control circuit controls the second switching circuit and the third switching circuit to be turned-on, and the first secondary side winding charges the first output capacitor, wherein, the second switching circuit is uni-directionally conducted, and the third switching circuit is bi-directionally conducted.
8 . The power conversion circuit according to claim 7 , wherein the control circuit controls the first switching circuit to be turned-off during a first period and controls the third switching circuit to be turned-on, and during a second period the first switching circuit is controlled to be turned-on and the third switching circuit is controlled to be turned-off, and the first period does not overlap the second period.
9 . The power conversion circuit according to claim 1 , further comprising: a snubber circuit, electrically connected to the primary side winding and the first switching circuit, and the snubber circuit comprises a capacitor, a resistor and a diode, the capacitor is connected to the resistor in parallel, and the diode is connected to the first switching circuit.

Description

This application claims the benefit of Taiwan application Serial No. 112113466, filed Apr. 11, 2023, the disclosure of which is incorporated by reference herein in its entirety. TECHNICAL FIELD The present disclosure relates to an electronic circuit, and in particular, relates to a power conversion circuit having a function of voltage balancing. BACKGROUND FIG. 1 is a circuit diagram of a power device 2000 in the prior art. The power device 2000 includes an input power supply 700, a processing circuit 800, a load circuit 600 and a first output capacitor Cb1 and a second output capacitor Cb2. The processing circuit 800 is connected to the input power supply 700 and the load circuit 600, the processing circuit 800 is used to adjust the amplitude and/or phase of the voltage and/or current provided by the input power supply 700. When the load circuit 600 is an inverter, the first output capacitor Cb1 is connected to the second output capacitor Cb2 in series, and the first output capacitor Cb1 and the second output capacitor Cb2 have larger capacitance values to store electrical energy. Since the parameters of the circuit parasitic elements of the first output capacitor Cb1 and the second output capacitor Cb2 are different, the voltages of the first output capacitor Cb1 and the second output capacitor Cb2 may be unbalanced. The processing circuit 800 may further comprise a balancing circuit (not shown in FIG. 1) to handle the condition of voltage imbalance. The balanced circuit in the prior art includes active components, passive components and inductors (not shown in FIG. 1), which form a buck converter and a boost converter and apply on the first output capacitor Cb1 and the second output capacitor Cb2 so as to reach voltage balance. However, adding a balanced circuit means adding more components (such as the above-mentioned active components, passive components and inductors), which leads to an increase in hardware costs. Therefore, it is necessary to improve the processing circuit 800 in the power device 2000 to replace the balancing circuit in the prior art with a more simplified circuit architecture, so as to perform the function of voltage balancing. SUMMARY The disclosure is directed to a power conversion circuit, which provides a function of voltage balancing. According to one embodiment, a power conversion circuit is provided. The power conversion circuit includes the following elements. A transformer, comprises a primary side winding, a first secondary side winding and a second secondary side winding. A first switching circuit, is connected to the primary side winding. A second switching circuit, is connected to the first secondary side winding. A third switching circuit, is connected to the second secondary side winding. A first output capacitor, is connected to the second switching circuit and the first secondary side winding, the first output capacitor has a first voltage value. A second output capacitor, is connected to the third switching circuit and the second secondary side winding, the second output capacitor has a second voltage value. A control circuit, is electrically connected to the first switching circuit, the second switching circuit and the third switching circuit. The control circuit controls the first switching circuit, the second switching circuit and the third switching circuit to be turned-on or turned-off respectively according to the first voltage value and the second voltage value, and to charge the first output capacitor or the second output capacitor. BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 (Prior Art) is a circuit diagram of a power device 2000 in the prior art. FIG. 2A is a block diagram of a power conversion circuit 1000 according to an embodiment of the present disclosure. FIG. 2B is a circuit diagram of the power conversion circuit 1000 of FIG. 2A. FIGS. 3A and 3B are schematic diagrams of an embodiment of voltage balancing operation performed by the power conversion circuit 1000 of FIG. 2B. FIG. 4 is a time variation diagram of the control voltages Vg1, Vg2 and Vg3 of the transistors Q1, Q2 and Q3 of the first switch 100, the second switch 200 and the third switch 300 respectively. FIGS. 5A and 5B are schematic diagrams of another embodiment of voltage balancing operation performed by the power conversion circuit 1000 in FIG. 2B. FIG. 6 is another time variation diagram of the control voltages Vg1, Vg2 and Vg3 of the transistors Q1, Q2 and Q3 of the first switch 100, the second switch 200 and the third switch 300 respectively. FIG. 7 is a detailed circuit diagram of the snubber circuit 500. In the following detailed description, for purposes of explanation, numerous specific details are set forth in order to provide a thorough understanding of the disclosed embodiments. It will be apparent, however, that one or more embodiments may be practiced without these specific details. In other instances, well-known structures and devices are schematically shown in order to simp