Switching power supply with low voltage output

Abstract

The utility model provides a switching power supply with low voltage output, which comprises a main transformer and an auxiliary transformer, primary windings of the main transformer and the auxiliary transformer are connected in a manner that dotted terminals are connected in series end to end, secondary windings are respectively connected with synchronous rectification circuits, and output ends of the two synchronous rectification circuits are connected in parallel; the two synchronous rectification circuits are connected with the same power supply chip through the same feedback circuit. The utility model provides an improved flyback power supply design, and low-voltage and high-efficiency output is realized by reducing leakage inductance of the transformer and absorbing power loss. The design not only can improve the system efficiency and reduce the energy loss, but also can reduce the cost and complexity, and has wide application prospects, especially in the field of low-voltage and large-current power supplies. Compared with a traditional double-transistor forward power supply, the power supply provided by the utility model is lower in cost, higher in efficiency and higher in reliability, and has an important market application value.

Description

Technical Field

[0001] This utility model relates to the field of display power supplies, and more specifically, to a low-voltage output switching power supply capable of providing a voltage output of 5V or lower. Background Technology

[0002] In the power supply field of electronic devices such as displays, low-voltage, high-current power supplies are typically required. Traditional flyback power supply solutions, especially at lower output voltages, often suffer from low efficiency and high energy loss.

[0003] The cause of this problem lies in the transformer leakage inductance effect in flyback power supplies. Specifically, the reverse voltage spike generated by the transformer leakage inductance on the primary side needs to be suppressed by an absorption circuit, resulting in additional power loss. As the difference between the input and output voltages increases, the turns ratio of the transformer's primary and secondary windings also increases, leading to increased leakage inductance and a larger primary-side ringing peak. This larger ringing peak affects the detection of the synchronous rectification signal. The synchronous rectification circuit relies on detecting the ringing signal to control the MOS transistors to turn on or off. When the synchronous rectification circuit malfunctions, the rectifier diode losses increase, and excessive absorption increases absorption power consumption, reducing the overall system efficiency.

[0004] To overcome this problem, dual-transistor forward converters are now widely used in low-voltage, high-current power supply solutions. Dual-transistor forward converters have lossless absorption characteristics, eliminating additional losses due to transformer leakage inductance, thus effectively improving efficiency. However, compared to flyback converters, dual-transistor forward converters are more complex in structure and more expensive. They require two MOSFETs and a drive transformer on the primary side, and an energy storage inductor and freewheeling diode at the output, further increasing system complexity and cost.

[0005] Therefore, how to effectively reduce leakage inductance while ensuring output voltage stability has become a core issue that urgently needs to be addressed. Utility Model Content

[0006] The purpose of this invention is to address the aforementioned problems by proposing a low-voltage output switching power supply. It splits the original single transformer into two identical transformers, achieving efficient power output through a series connection of the primary windings and a parallel connection of the secondary windings. In this way, the input voltage is effectively reduced by half, and the turns ratio of the primary and secondary windings is correspondingly reduced, thus significantly reducing the leakage inductance of the single transformer. Compared to traditional flyback power supply designs, this method effectively reduces energy loss caused by leakage inductance, and the synchronous rectifier circuit will not cause signal detection errors due to ringing abnormalities, thereby improving the overall system efficiency to reach or exceed the efficiency level of a two-transistor forward converter.

[0007] The technical solution of this utility model is:

[0008] This utility model provides a low-voltage output switching power supply, including a main transformer and a secondary transformer. The primary windings of the main transformer and the secondary transformer are connected in series with the same terminals. The secondary windings are respectively connected to synchronous rectifier circuits, and the output terminals of the two synchronous rectifier circuits are connected in parallel. The two synchronous rectifier circuits are connected to the same power chip through the same feedback circuit.

[0009] Furthermore, the auxiliary winding of the main transformer is used to supply power to the power chip.

[0010] Furthermore, the power chip adopts an AC-DC flyback switching power supply architecture.

[0011] Furthermore, the main transformer and the secondary transformer have the same turns ratio, the same output voltage, and the same phase.

[0012] Furthermore, the synchronous rectification circuit employs a synchronous rectification switch.

[0013] Furthermore, the secondary transformers are configured in multiple groups.

[0014] Furthermore, the primary windings of the main transformer and the secondary transformer are half the primary windings of the transformer in the traditional flyback power supply scheme, while the secondary windings remain unchanged.

[0015] Furthermore, when there are n groups of auxiliary transformers, the primary windings of the main transformer and auxiliary transformers are 1 / (n+1) of the primary windings of the transformer in the traditional flyback power supply scheme, while the secondary windings remain unchanged.

[0016] The beneficial effects of this utility model are:

[0017] This utility model discloses a low-voltage output switching power supply. By connecting the primary windings of two transformers with the same turns ratio in series and the secondary synchronous rectifier circuits in parallel, it achieves reduced leakage inductance, reduced ringing amplitude of a single transformer, and stable synchronous rectifier detection and control signals, thus adapting to the goal of low output voltage. Using a single control chip to synchronously control the two secondary rectifier circuits, only one feedback circuit is needed for voltage regulation detection and output voltage adjustment, effectively solving the problems of synchronous control and voltage stability when multiple transformers are connected in parallel.

[0018] When further reduction of leakage inductance is required, this invention also provides an expansion scheme by increasing the number of transformer banks. This design not only simplifies the control structure but also improves the reliability and efficiency of the system, while possessing good scalability, providing an effective solution for low-voltage, high-current applications.

[0019] This invention is particularly applicable to the display industry, as it can provide a voltage output of 5V or lower, effectively improving the low efficiency of existing low-voltage output flyback power supply solutions and providing a more efficient solution for low-voltage, high-current power supply applications.

[0020] Other features and advantages of this invention will be described in detail in the following detailed description section. Attached Figure Description

[0021] The above and other objects, features and advantages of the present invention will become more apparent from the accompanying drawings, in which like reference numerals generally represent like parts.

[0022] Figure 1 A block diagram of a low-voltage output switching power supply according to an embodiment of the present invention is shown.

[0023] Figure 2 The original flyback power supply block diagram is shown. Detailed Implementation

[0024] Preferred embodiments of the present invention will now be described in more detail with reference to the accompanying drawings. Although preferred embodiments of the present invention are shown in the drawings, it should be understood that the present invention can be implemented in various forms and should not be limited to the embodiments set forth herein.

[0025] The power module of this invention adopts an AC-DC flyback switching power supply architecture. The primary windings of the main and secondary transformers are connected in series with their corresponding terminals. The power supply for the driver chip is achieved through the auxiliary winding of the main transformer. The secondary section uses two synchronous rectifier circuits connected in parallel at their outputs. Since the turns ratio of the main and secondary transformers is the same, the output voltages of the two transformers are identical and in phase. A single chip controls the two synchronous rectifier switches, thus simplifying the circuit design and reducing system complexity.

[0026] Compared to traditional flyback power supply solutions, this solution achieves higher efficiency by reducing transformer leakage inductance. Due to the reduced leakage inductance, the peak ringing value on the primary side of the individual transformer is lowered, and the power consumption required for the suppression and absorption circuit is reduced, resulting in a significant improvement in the overall power supply system efficiency. This allows the flyback power supply to be used in low-voltage, high-current applications.

[0027] Reduce transformer leakage inductance: By splitting the original transformer into two identical transformers, with the primary side connected in series and the secondary side connected in parallel, the leakage inductance of a single transformer is effectively reduced, thereby reducing the peak energy generated by leakage inductance and lowering the power loss.

[0028] Improved system efficiency: Due to the reduction in leakage inductance and the decrease in power consumption of the absorption circuit, the overall system efficiency is significantly improved, and the efficiency can even reach or exceed that of a two-transistor forward power supply.

[0029] Simplified circuit design: By connecting multiple synchronous rectifier circuits in parallel, only one chip is needed to control two synchronous rectifier switches. At the same time, the design of the feedback circuit can be simplified, reducing the complexity and cost of the system.

[0030] To accommodate lower output voltages: By adding more sets of secondary transformers, the leakage inductance of the transformers is further reduced, and losses are decreased, thus adapting to the need for lower voltage outputs.

[0031] In practical implementation, taking a power input of 220V and an output of 4.2V 15A as an example, two PQ2014 transformers are used with an efficiency of 86%; one large PQ3216 transformer is used with an efficiency of 77%; and the efficiency of a two-tube forward converter is 83.7%. Both the cost and efficiency advantages are obvious compared to the two-tube forward converter.

[0032] This invention employs a flyback scheme, achieving or exceeding the efficiency of a dual-tube forward converter, effectively reducing costs and resulting in significant economic benefits.

[0033] The various embodiments of the present invention have been described above. These descriptions are exemplary and not exhaustive, nor are they limited to the disclosed embodiments. Many modifications and variations will be apparent to those skilled in the art without departing from the scope and spirit of the described embodiments.

Claims

1. A switching power supply with low voltage output, characterized in that, The main transformer and the auxiliary transformer are connected in series with the same end-to-end connection of the primary windings, the secondary windings are connected to the synchronous rectification circuits respectively, and the output ends of the two synchronous rectification circuits are connected in parallel; the two synchronous rectification circuits are connected to the same power chip through the same feedback circuit.

2. The low voltage output switching power supply of claim 1 wherein, The auxiliary winding of the main transformer is used for power supply of the power chip.

3. The low voltage output switching power supply of claim 2 wherein, The power chip adopts an AC-DC flyback switching power supply architecture.

4. The low voltage output switching power supply of claim 1, wherein, The main transformer and the auxiliary transformer have the same turn ratio, the same output voltage and consistent phase.

5. The low voltage output switching power supply of claim 1 wherein, The synchronous rectification circuit adopts a synchronous rectification switch tube.

6. The low voltage output switching power supply of claim 1, wherein, The auxiliary transformer is provided in multiple groups.

7. The low voltage output switching power supply of claim 1 wherein, The primary windings of the main transformer and the auxiliary transformer are half of the primary windings of the transformer in a traditional flyback power supply scheme, and the secondary windings are unchanged.

8. The low voltage output switching power supply of claim 6 wherein, When the auxiliary transformer is n groups, the primary windings of the main transformer and the auxiliary transformer are 1 / (n+1) of the primary windings of the transformer in a traditional flyback power supply scheme, and the secondary windings are unchanged.

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