KR-20260062488-A - Forward-flyback converter and power supplying apparatus using the same

Abstract

An embodiment of the present invention comprises: a first switch and a second switch that alternately switch with each other; a first transformer comprising a primary coil, a magnetic core, and a secondary coil; a second transformer comprising a primary coil, a magnetic core, and a secondary coil; a third transformer comprising a primary coil, a magnetic core, and a secondary coil; a first diode; and a second diode. A forward-flyback converter comprising a first transformer, a second transformer, and a third diode, wherein the primary coil of the first transformer, the primary coil of the second transformer, and the primary coil of the third transformer are connected in series to the contacts of the first switch and the second switch, the secondary coil of the first transformer, the secondary coil of the second transformer, and the secondary coil of the third transformer are connected in parallel to each other, and the first diode, the second diode, and the third diode are each connected in series to the secondary coil of the first transformer, the secondary coil of the second transformer, and the secondary coil of the third transformer, respectively, and when the second switch is turned on, power can be transferred through the first transformer, and when the first switch is turned on, magnetic field energy stored in the second and third transformers can be transferred to the secondary coil of the second transformer and the secondary coil of the third transformer. It provides a forward-flyback converter.

Inventors

• 윤한신
• 권경현
• 이동인
• 정성욱
• 김홍성
• 장동혁
• 최인석

Assignees

• 인천대학교 산학협력단

Dates

Publication Date

20260507

Application Date

20241029

Claims (18)

1. A forward-flyback converter comprising: a first switch and a second switch that alternately switch with each other; a first transformer including a primary coil, a magnetic core, and a secondary coil; a second transformer including a primary coil, a magnetic core, and a secondary coil; a third transformer including a primary coil, a magnetic core, and a secondary coil; a first diode; a second diode; and a third diode, wherein The primary coil of the first transformer, the primary coil of the second transformer, and the primary coil of the third transformer are connected in series to the contacts of the first switch and the second switch, and The secondary coil of the first transformer, the secondary coil of the second transformer, and the secondary coil of the third transformer are connected in parallel with each other, The first diode, the second diode, and the third diode are each connected in series to the secondary coil of the first transformer, the secondary coil of the second transformer, and the secondary coil of the third transformer, respectively. When the second switch is turned on, power can be transmitted through the first transformer, and A forward-flyback converter in which, when the first switch is turned on, magnetic field energy stored in the second and third transformers can be transferred to the secondary coil of the second transformer and the secondary coil of the third transformer.
2. In paragraph 1, A forward-flyback converter in which the first transformer is a forward transformer and the second and third transformers are flyback transformers.
3. In paragraph 2, A forward-flyback converter in which magnetic field energy can be stored in the second and third transformers when the second switch is turned on.
4. In paragraph 3, A forward-flyback converter in which the first diode can conduct when the second switch is turned on.
5. In paragraph 4, A forward-flyback converter in which, when the second switch is turned on, the leakage inductance current can be expressed by Equation 1. [Mathematical Formula 1] (Here, t represents time, Lm,fly is the magnetizing inductance of the flyback transformer, iLm,fly is the current flowing through the magnetizing inductance (Lm,fly), Vs is the DC input voltage, Vo is the DC output voltage, and n represents the winding ratio.)
6. In paragraph 2, A forward-flyback converter in which, when the second switch is turned off, the magnetic field energy stored in the second and third transformers is discharged and recirculation can occur.
7. In paragraph 6, A forward-flyback converter in which the first diode, the second diode, and the third diode can conduct when the second switch is turned off.
8. In paragraph 2, A forward-flyback converter in which, when the first switch is turned on, the magnetic core of the first transformer is reset, and the current flowing through the first magnetizing inductor (Lm,for) connected in parallel to the primary coil of the first transformer can be reset.
9. In paragraph 8, A forward-flyback converter in which the second and third diodes can conduct when the first switch is turned on.
10. In Paragraph 9, A forward-flyback converter in which the current flowing through the second and third diodes can be expressed by Equation 2. [Mathematical Formula 2] (Here, t represents time, iLm,fly represents the current flowing through the magnetizing inductance (Lm,fly) of the flyback transformer, iLm,for represents the current flowing through the magnetizing inductance (Lm,for) of the forward transformer, io represents the output current, and n represents the winding ratio.)
11. In paragraph 2, A forward-flyback converter in which, when the first switch is turned off, the magnetic field energy stored in the first transformer is discharged and recirculation can occur.
12. In Paragraph 11, A forward-flyback converter in which the first to third diodes can conduct when the first switch is turned off.
13. In paragraph 1, The above forward-flyback converter is a forward-flyback converter configured as shown in Circuit Diagram 1. [Circuit Diagram 1]
14. In paragraph 1, A forward-flyback converter in which the primary coil and secondary coil of the first transformer, the primary coil and secondary coil of the second transformer, and the primary coil and secondary coil of the third transformer are circuit patterns of a printed circuit board.
15. In Paragraph 14, The circuit pattern of the above printed circuit board includes four layers, and The primary coil of the first transformer, the primary coil of the second transformer, and the primary coil of the third transformer are disposed on the second and third layers of the printed circuit board, and A forward-flyback converter in which the secondary coil of the first transformer, the secondary coil of the second transformer, and the secondary coil of the third transformer are disposed on the first and fourth layers of the printed circuit board.
16. In paragraph 1, The above forward-flyback converter is a forward-flyback converter with an output of 4kW, composed of three magnetic cores.
17. In Paragraph 16, The above forward-flyback converter is a forward-flyback converter having one magnetic core of a forward transformer.
18. A power supply comprising a forward-flyback converter of at least one of claims 1 to 17.

Description

Forward-flyback converter and power supplying apparatus using the same The present invention relates to a forward-flyback converter with a reduced number of magnetic cores and a power supply device using the same. Recently, the need for Low-Voltage DC Converters (LDCs) for low-voltage (LV) battery charging and power supply in electric vehicle (EV) charging systems has become increasingly prominent. This is because the power requirements of EV charging systems are increasing as autonomous driving technology advances. Therefore, there is a need for high-power LDC technology for use in next-generation autonomous driving technologies. Meanwhile, to minimize the increase in volume due to increased power capacity, it is necessary to reduce the volume of the LDC. Generally, magnetic materials such as transformers and output inductors account for about 50% of the volume of an LDC converter. FIG. 1 is a circuit diagram showing a conventional 2kW LDC, FIG. 2 is a circuit diagram showing a conventional 4kW forward-flyback converter, FIG. 3 is a diagram showing the layout of the 4kW forward-flyback converter of FIG. 2, FIG. 4 is a diagram showing the coils constituting the transformer of the 4kW forward-flyback converter of FIG. 2, and FIG. 5 is a diagram showing the magnetic circuit of the transformer of the 4kW forward-flyback converter of FIG. 2. FIGS. 1a and FIGS. 2a are drawings showing conventional 2kW LDCs with different topologies. As there is a requirement to increase power capacity from 2kW to 4kW, a 4kW class LDC was developed by connecting two 2kW LDCs in series and parallel. However, as shown in FIG. 2, four magnetic cores of the transformer were used when connecting two 2kW LDCs in series and parallel. As a result, the effect of volume reduction was inevitably reduced despite integrating the output inductor and transformer. The effect of increasing power density was also poor. In addition, as the transformer secondary rectification structure was connected in parallel to achieve a 4kW output, the number of semiconductor devices such as switches and diodes increased, leading to an increase in costs. Figure 1 is a circuit diagram showing a conventional 2kW LDC. Figure 2 is a circuit diagram showing a conventional 4kW forward-flyback converter. Figure 3 is a diagram showing the layout of the 4kW forward-flyback converter of Figure 2. Figure 4 is a diagram showing the coils constituting the transformer of the 4kW forward-flyback converter of Figure 2. Figure 5 is a diagram showing the magnetic circuit of the transformer of the 4kW forward-flyback converter of Figure 2. FIG. 6 is a circuit diagram showing a forward-flyback converter according to an embodiment of the present invention. FIG. 7 is a diagram showing a magnetic material in a circuit diagram of a forward-flyback converter according to an embodiment of the present invention. FIG. 8 is a diagram showing the layout of a forward-flyback converter according to an embodiment of the present invention. FIG. 9 is a drawing showing the shape of a transformer according to an embodiment of the present invention. FIG. 10 is a drawing showing a coil constituting a transformer according to an embodiment of the present invention. FIG. 11 is a diagram showing the magnetic circuit of a transformer according to an embodiment of the present invention. FIG. 12 is a diagram showing the operation waveform of a forward-flyback converter according to an embodiment of the present invention. FIG. 13 is a circuit diagram showing the current flow of the first mode of a forward-flyback converter according to an embodiment of the present invention. FIG. 14 is a diagram showing the current flow of FIG. 13 in the coil of a transformer according to an embodiment of the present invention. FIG. 15 is a circuit diagram showing the current flow of the second mode of a forward-flyback converter according to an embodiment of the present invention. FIG. 16 is a diagram showing the current flow of FIG. 15 in the coil of a transformer according to an embodiment of the present invention. FIG. 17 is a circuit diagram showing the current flow of the third mode of a forward-flyback converter according to an embodiment of the present invention. FIG. 18 is a diagram showing the current flow of FIG. 17 in the coil of a transformer according to an embodiment of the present invention. FIG. 19 is a circuit diagram showing the current flow of the fourth mode of a forward-flyback converter according to an embodiment of the present invention. FIG. 20 is a diagram showing the current flow of FIG. 19 in the coil of a transformer according to an embodiment of the present invention. FIG. 21 is a diagram showing the simulation results of a forward-flyback converter according to an embodiment of the present invention. FIG. 22 is a diagram showing another simulation result of a forward-flyback converter according to an embodiment of the present invention. FIG. 23 is a diagram showing the magnetic flux density of