A single-stage PFC flyback power supply circuit and product
By designing a single-stage PFC flyback power supply circuit and utilizing a Boost converter circuit composed of an inductor, transformer, and switching transistor, the high cost of traditional solutions is solved, achieving low-cost harmonic testing requirements and reducing power supply size.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SHENZHEN AMC TECH CO LTD
- Filing Date
- 2025-08-12
- Publication Date
- 2026-07-21
AI Technical Summary
In the existing technology, the two-stage PFC+DCDC solution is costly, difficult to meet harmonic requirements, and difficult to reduce costs.
Design a single-stage PFC flyback power supply circuit, using a Boost converter circuit composed of inductors, transformers, capacitors, bipolar transistors and switching transistors. Energy transfer is achieved by controlling the switching transistors to reduce the number of components.
This approach achieves the goal of meeting harmonic testing requirements while reducing the number of components and the size of the power supply, thereby reducing costs.
Smart Images
Figure CN224538065U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of switching power supply technology, and more specifically, to a single-stage PFC flyback power supply circuit and product. Background Technology
[0002] With the promotion of 3C certification in China, more and more power supplies will need to meet certain harmonic requirements to pass certification in the future. To meet this requirement, the traditional approach is to use a two-stage solution, namely PFC+DCDC. Although this solution can achieve a relatively high power factor and low harmonic current, the cost is very high. In order to reduce costs, a single-stage PFC flyback power supply circuit and product are needed. Utility Model Content
[0003] The technical problem to be solved by this utility model is to provide a single-stage PFC flyback power supply circuit and a single-stage PFC flyback power supply product, in view of the above-mentioned defects of the prior art.
[0004] The technical solution adopted by this utility model to solve its technical problem is:
[0005] A single-stage PFC flyback power supply circuit is constructed, which includes an inductor, a transformer, a first capacitor, a first diode, a second diode, a switching transistor, and a flyback power supply chip.
[0006] One end of the inductor and the positive terminal of the first diode are connected to the positive terminal of the power supply, and the negative terminal of the first capacitor is connected to the negative terminal of the power supply and grounded.
[0007] The other end of the inductor is connected to the positive terminal of the second diode, and the negative terminal of the first diode is connected to the positive terminal of the first capacitor and one end of the primary coil of the transformer.
[0008] The negative terminal of the second diode is connected to the middle or the other end of the primary coil of the transformer, and the other end of the primary coil of the transformer is connected to the switching transistor.
[0009] The switching transistor is used to control the grounding of the primary coil of the transformer. The switching transistor is connected to and controlled by the flyback power chip.
[0010] The single-stage PFC flyback power supply circuit of this utility model further includes a rectifier stack, wherein the positive output terminal of the rectifier stack is the positive terminal of the power supply, and the negative output terminal of the rectifier stack is the negative terminal of the power supply.
[0011] In the single-stage PFC flyback power supply circuit of this utility model, the switching transistor is an NMOS transistor;
[0012] The gate (G) of the NMOS transistor is connected to the flyback power supply chip, the source (S) of the NMOS transistor is grounded, and the drain (D) of the NMOS transistor is connected to the other end of the primary coil of the transformer.
[0013] The single-stage PFC flyback power supply circuit of this utility model further includes a third diode and a second capacitor.
[0014] One end of the secondary coil of the transformer is connected to the positive terminal of the third diode, and the negative terminal of the third diode is connected to the positive terminal and the positive output terminal of the second capacitor.
[0015] The other end of the secondary coil of the transformer is connected to the negative terminal of the second capacitor and the negative output terminal.
[0016] A method for applying a single-stage PFC flyback power supply circuit, wherein the single-stage PFC flyback power supply circuit described above is used, and the method includes the following steps:
[0017] The switching transistor switches between on and off states under the control of the flyback power supply chip;
[0018] When the switching transistor is turned on, the primary coil of the transformer is grounded, and the inductor and transformer begin to store energy.
[0019] When the switching transistor is turned off, the energy released by the inductor returns to the first capacitor via the second diode, and the energy of the primary coil of the transformer is coupled to the secondary coil of the transformer.
[0020] A flyback power supply product with single-stage PFC, wherein the product is provided with a flyback power supply circuit as described above for single-stage PFC.
[0021] The beneficial effects of this utility model are as follows: By applying the circuit of this application, the inductor, the second diode and the switching transistor are combined to form a Boost circuit, and the flyback power supply and the boost circuit share a single switching transistor. This can meet the requirements of power supply harmonic testing while significantly reducing the number of components used, thereby reducing cost and power supply size. It can be applied to any switching power supply product that requires harmonic testing and is suitable for widespread adoption. Attached Figure Description
[0022] To more clearly illustrate the technical solutions in the embodiments of this utility model or the prior art, the utility model will be further described below in conjunction with the accompanying drawings and embodiments. The drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort.
[0023] Figure 1 This is a circuit diagram of a single-stage PFC flyback power supply circuit in the on state of Embodiment 1 of this utility model.
[0024] Figure 2 This is a circuit diagram of the flyback power supply circuit of a single-stage PFC in the disconnected state according to Embodiment 1 of this utility model.
[0025] Figure 3 This is the switching transistor timing diagram of the single-stage PFC flyback power supply circuit of this utility model;
[0026] Figure 4 This is a circuit diagram of the flyback power supply circuit of a single-stage PFC in the on state of Embodiment 2 of this utility model;
[0027] Figure 5 This is a circuit diagram of the flyback power supply circuit of a single-stage PFC in the disconnected state according to Embodiment 2 of this utility model. Detailed Implementation
[0028] To make the objectives, technical solutions, and advantages of the embodiments of this utility model clearer, a clear and complete description will be provided below in conjunction with the technical solutions in the embodiments of this utility model. Obviously, the described embodiments are some, but not all, embodiments of this utility model. Based on the embodiments of this utility model, all other embodiments obtained by those skilled in the art without creative effort are within the protection scope of this utility model.
[0029] Example 1
[0030] The preferred embodiment of this utility model is a single-stage PFC flyback power supply circuit, such as... Figure 1 As shown, see also Figure 2 and Figure 3 It includes inductor L1, transformer T1, first capacitor EC1, first diode D1, second diode D2, switching transistor Q1, and flyback power supply chip;
[0031] One end of inductor L1 and the positive terminal of the first diode D1 are connected to the positive terminal of the power supply, and the negative terminal of the first capacitor EC1 is connected to the negative terminal of the power supply and grounded.
[0032] The other end of inductor L1 is connected to the positive terminal of the second diode D2, and the negative terminal of the first diode D1 is connected to the positive terminal of the first capacitor EC1 and one end of the primary coil of transformer T1.
[0033] The negative terminal of the second diode D2 is connected to the middle of the primary coil of transformer T1, and the other end of the primary coil of transformer T1 is connected to the switching transistor Q1.
[0034] Switch Q1 is used to control the grounding of the primary coil of transformer T1. Switch Q1 is connected to the flyback power supply chip and is controlled by it.
[0035] The working principle of this embodiment is as follows:
[0036] The timing sequence for the on / off state switching of Q1 is as follows: Figure 3 As shown;
[0037] like Figure 1 As shown, when Q1 is turned on, inductor L1 and transformer T1 store energy; (I_1 and I_2 are both current flow directions);
[0038] like Figure 2 As shown, Q1 is off, L1 releases energy and returns to capacitor EC1 via D2, and the energy of the primary winding of transformer T1 is coupled to the secondary winding of transformer; (I_1 and I_2 are both current flow directions);
[0039] The circuit of this application combines inductor L1, second diode D2 and switching transistor Q1 to form a boost circuit. The flyback power supply and the boost circuit share a single switching transistor Q1, which can meet the power supply harmonic testing requirements while significantly reducing the number of components, thereby reducing cost and power supply size. It can be applied to any switching power supply product that requires harmonic testing and is suitable for widespread adoption.
[0040] The drawback of this scheme is that L1 is connected to the primary intermediate winding of the transformer, and the energy stored and released by L1 is relatively small, so the power supply PF value cannot be greater than 0.9 across the entire voltage range.
[0041] Preferably, the circuit further includes a rectifier stack BD1, the positive output terminal of the rectifier stack BD1 being the positive terminal of the power supply, and the negative output terminal of the rectifier stack being the negative terminal of the power supply.
[0042] Preferably, the switching transistor Q1 is an NMOS transistor;
[0043] The gate (G) of the NMOS transistor is connected to the flyback power supply chip, the source (S) of the NMOS transistor is grounded, and the drain (D) of the NMOS transistor is connected to the other end of the primary coil of transformer T1.
[0044] It should be noted that the switching transistor is only a preferred implementation method, and it can be replaced by other controllable switch forms as needed. The solutions obtained based on such equivalent replacements also fall within the protection scope of this application.
[0045] Preferably, the circuit also includes a third diode D3 and a second capacitor EC2;
[0046] One end of the secondary coil of transformer T1 is connected to the positive terminal of the third diode D3, and the negative terminal of the third diode D3 is connected to the positive terminal of the second capacitor EC2 and the positive output terminal.
[0047] The other end of the secondary coil of transformer T1 is connected to the negative terminal of the second capacitor EC2 and the negative output terminal.
[0048] Example 2
[0049] This embodiment is basically the same as the previous embodiment, and the similarities will not be repeated here. Figure 4 and Figure 5 As shown, the difference is:
[0050] The negative terminal of the second diode D2 is connected to the other end of the primary coil of transformer T1;
[0051] The principle behind this implementation method is as follows:
[0052] Refer to the timing diagram for the on / off state switching of Q1. Figure 3 ;
[0053] like Figure 4 As shown, Q1 is turned on, and inductor L1 and transformer T1 store energy; (I_1 and I_2 are both current flow directions);
[0054] like Figure 5 As shown, Q1 is off, L1 releases energy and returns to capacitor EC1 via D2, and the energy of the primary winding of transformer T1 is coupled to the secondary winding of transformer T1; (I_1 and I_2 are both current flow directions);
[0055] In this scheme, L1 is connected to Q1. L1 stores and releases a large amount of energy, and the power supply's power factor (PF) can reach >0.9 across the entire voltage range. Compared to the first embodiment, this implementation scheme is more effective. Of course, both implementation schemes fall within the scope of protection of this application.
[0056] Example 3
[0057] A flyback power supply product with single-stage PFC is provided, wherein the product is provided with a single-stage PFC flyback power supply circuit as described above; the product range can cover any switching power supply product that requires harmonic testing, as well as other electronic products that can be applied to the circuits of this application.
[0058] It should be understood that those skilled in the art can make improvements or modifications based on the above description, and all such improvements and modifications should fall within the protection scope of the appended claims.
Claims
1. A flyback power supply circuit with single-stage PFC, characterized in that, It includes inductors, transformers, first capacitors, first diodes, second diodes, switching transistors, and flyback power supply chips; One end of the inductor and the positive terminal of the first diode are connected to the positive terminal of the power supply, and the negative terminal of the first capacitor is connected to the negative terminal of the power supply and grounded. The other end of the inductor is connected to the positive terminal of the second diode, and the negative terminal of the first diode is connected to the positive terminal of the first capacitor and one end of the primary coil of the transformer. The negative terminal of the second diode is connected to the middle or the other end of the primary coil of the transformer, and the other end of the primary coil of the transformer is connected to the switching transistor. The switching transistor is used to control the grounding of the primary coil of the transformer. The switching transistor is connected to and controlled by the flyback power chip.
2. The flyback power supply circuit for a single-stage PFC according to claim 1, characterized in that, The circuit also includes a rectifier stack, the positive output terminal of which is the positive terminal of the power supply, and the negative output terminal of which is the negative terminal of the power supply.
3. The flyback power supply circuit for a single-stage PFC according to claim 1, characterized in that, The switching transistor is an NMOS transistor; The gate (G) of the NMOS transistor is connected to the flyback power supply chip, the source (S) of the NMOS transistor is grounded, and the drain (D) of the NMOS transistor is connected to the other end of the primary coil of the transformer.
4. The flyback power supply circuit for a single-stage PFC according to claim 1, characterized in that, The circuit also includes a third diode and a second capacitor; One end of the secondary coil of the transformer is connected to the positive terminal of the third diode, and the negative terminal of the third diode is connected to the positive terminal of the second capacitor and the positive output terminal. The other end of the secondary coil of the transformer is connected to the negative terminal of the second capacitor and the negative output terminal.
5. A single-stage PFC flyback power supply product, characterized in that, The product is equipped with a flyback power supply circuit as described in any one of claims 1-4.