Double-transistor flyback switching power supply

Abstract

The utility model relates to the technical field of switching power supplies, in particular to a double-transistor flyback switching power supply, which is characterized in that a PFC (Power Factor Correction) module consists of a PFC chip U1 and a peripheral circuit thereof, the peripheral circuit of the PFC chip U1 is provided with a quick start circuit, and the quick start circuit is integrally packaged in the PFC chip U1; the auxiliary driving module is composed of a double-tube driving chip U2 and a peripheral circuit thereof, and a double-tube circuit is integrated and packaged in the double-tube driving chip U2; the main driving module is composed of a single-tube driving chip U3 and a peripheral circuit thereof, the single-tube driving chip U3 is additionally provided with a switching signal end, and the switching signal end is electrically connected with the input end of the double-tube driving chip U2; the problem that control is difficult when a single chip drives double tubes is solved, and the problems that the number of peripheral circuit discrete components of multiple chips in a switching power supply is large, the space of a circuit board is occupied, and the production efficiency is low are solved.

Description

Technical Field

[0001] This utility model relates to the field of switching power supply technology, and in particular to a dual-transistor flyback switching power supply. Background Technology

[0002] Currently, in switching power supplies used for LED drivers, a PFC + dual-tube flyback (i.e., dual-tube quasi-resonant flyback technology) scheme has been proposed to achieve ultra-high efficiency. Its power conversion topology design doubles the power output, improving the switching power supply's performance in terms of energy efficiency, EMC, and temperature rise, greatly expanding its application scope and significantly alleviating customers' power limitation anxieties. More importantly, the PFC + dual-tube flyback scheme offers higher power density compared to the PFC + LLC or PFC + single-tube flyback schemes.

[0003] However, existing dual-transistor flyback switching power supplies typically use a KP2202B+KP85405 chip combination framework, where both the upper and lower transistors are controlled by the KP85405 chip. The dual-transistor control logic design is relatively complex and generates concentrated heat. On the other hand, the peripheral circuits of existing switching power supplies use discrete components, which occupy a lot of circuit board space and require the continuous insertion, installation, and soldering of discrete components during the manufacturing process, resulting in low production efficiency. Utility Model Content

[0004] To address the aforementioned shortcomings, the purpose of this invention is to propose a dual-transistor flyback switching power supply, which solves the problems of difficulty in controlling dual transistors with a single chip, as well as the problems of numerous discrete components in the peripheral circuits of multi-chip switching power supplies, which occupy circuit board space and result in low production efficiency.

[0005] To achieve this objective, the present invention adopts the following technical solution:

[0006] A dual-transistor flyback switching power supply includes a PFC module, a secondary drive module, a primary drive module, a dual-transistor circuit, and a transformer T1. The PFC module is electrically connected to both the secondary drive module and the primary drive module. The secondary drive module is electrically connected to the primary winding of the transformer T1 via the dual-transistor circuit. The primary drive module is electrically connected to the primary winding of the transformer T1.

[0007] The PFC module consists of a PFC chip U1 and its peripheral circuits. The peripheral circuits of the PFC chip U1 are equipped with a fast start circuit, which is integrated and packaged within the PFC chip U1.

[0008] The secondary drive module consists of a dual-transistor drive chip U2 and its peripheral circuits, with the dual-transistor circuits integrated and packaged within the dual-transistor drive chip U2.

[0009] The main drive module consists of a single-transistor drive chip U3 and its peripheral circuits. The single-transistor drive chip U3 is equipped with a switch signal terminal, which is electrically connected to the input terminal of the dual-transistor drive chip U2.

[0010] Furthermore, the fast startup circuit includes a MOSFET Q1, resistors R1 and R2, a voltage regulator DZ1, and a diode D10; one end of resistor R1 and one end of resistor R2 are electrically connected, the other end of resistor R1 and the gate of MOSFET Q1 are both electrically connected to the cathode of voltage regulator DZ1, the anode of voltage regulator DZ1 is grounded, the other end of resistor R2 is electrically connected to the drain of MOSFET Q1, the source of MOSFET Q1 is electrically connected to the anode of diode D10, and the cathode of diode D10 is electrically connected to the power supply terminal of PFC chip U1;

[0011] One end of the resistor R1 is used as a new pin HV terminal of the PFC chip U1 for electrical connection with the VBUS power supply bus.

[0012] Furthermore, the PFC chip U1 is model OB3674.

[0013] Furthermore, the dual-transistor circuit includes resistors R20, R21, R22, and R23, MOSFET Q3, and MOSFET Q4; one end of resistor R22 is electrically connected to the high-order output terminal of the dual-transistor driver chip U2, the other end of resistor R22 and one end of resistor R23 are both electrically connected to the gate of MOSFET Q4, the other end of resistor R23 and the source of MOSFET Q4 are both electrically connected to the drain of MOSFET Q3, the gate of MOSFET Q3 and one end of resistor R21 are both electrically connected to one end of resistor R20, the other end of resistor R21 and the source of MOSFET Q3 are both grounded, and the other end of resistor R20 is electrically connected to the low-order output terminal of the dual-transistor driver chip U2;

[0014] The low-order output pin of the dual-transistor driver chip U2 is removed, the drain of the MOS transistor Q4 replaces the high-order output pin of the dual-transistor driver chip U2 as a pin, and the source of the MOS transistor Q4 replaces the high-voltage floating power supply terminal of the dual-transistor driver chip U2 as a pin.

[0015] Furthermore, the dual-transistor driver chip U2 is model BP6914.

[0016] Furthermore, the gate of the built-in MOS transistor in the single-transistor driver chip U3 is used as the switching signal terminal.

[0017] Furthermore, the single-transistor driver chip U3 is model BP3187.

[0018] Furthermore, it also includes a synchronous rectification module; the secondary winding of the transformer T1 is electrically connected to the synchronous rectification module;

[0019] The synchronous rectification module is an integrated package of synchronous rectification chip U4 and its peripheral circuits.

[0020] Furthermore, the synchronous rectifier chip U4 is model KP4050.

[0021] The technical solution provided by this utility model can include the following beneficial effects: The dual-transistor flyback circuit architecture mainly consists of a secondary driver module, a main driver module, and a dual-transistor circuit. The secondary driver module controls the upper switching transistor (such as a MOSFET) of the dual-transistor circuit, and the main driver module controls the lower switching transistor. The advantage of independently controlling the upper and lower transistors is that it reduces the voltage stress on the switching transistors, improves the efficiency of the power supply, facilitates control logic design, and better dissipates heat. Furthermore, the power supply with the same parameters can be designed to handle higher power requirements. Based on this, the secondary driver module and the main driver module preferably use a dual-transistor driver chip U2 and a single-transistor driver chip U3, respectively. The dual-transistor driver chip U2 can drive two switching transistors, and the single-transistor driver chip U3 can control the two switching transistors separately by adding a switching signal terminal in conjunction with the dual-transistor driver chip U2.

[0022] Meanwhile, in order to reduce the number of discrete components and the space occupied on the circuit board, and improve production efficiency, the fast start circuit of the peripheral circuit of PFC chip U1 is integrated and packaged into PFC chip U1 to form a new PFC chip U1; the dual-transistor circuit directly driven by dual-transistor driver chip U2 is integrated and packaged into dual-transistor driver chip U2 to form a new dual-transistor driver chip U2; thus, in the future production of switching power supplies, the new PFC chip U1 and the new dual-transistor driver chip U2 can be used directly without adjusting the inherent functional circuit of the chip peripheral. Attached Figure Description

[0023] Figure 1 This is one embodiment of a dual-transistor flyback switching power supply circuit. Figure 1 .

[0024] Figure 2 Is it like this? Figure 1 The circuit diagram shown is before the PFC chip U1 integrates the fast startup circuit.

[0025] Figure 3 Is it like this? Figure 1 The circuit diagram shown is before the dual-transistor driver chip U2 integrates the dual-transistor circuit.

[0026] Figure 4 Is it like this? Figure 1 The diagram shows the internal circuitry of the PFC chip U1 after integrating the fast startup circuit.

[0027] Figure 5 Is it like this? Figure 1 The diagram shows the internal circuitry of the dual-transistor driver chip U2 before its integrated dual-transistor circuitry.

[0028] Figure 6 Is it like this? Figure 1 The diagram shows the internal circuit of the dual-transistor driver chip U2 after integrating the dual-transistor circuit.

[0029] Figure 7 Is it like this? Figure 1 The diagram shows the internal circuit of the single-transistor driver chip U3 after adding a switch signal terminal.

[0030] Figure 8 Is it like this? Figure 1 The circuit diagram shown is a dual-transistor flyback switching power supply. Figure 2 .

[0031] The components include: PFC module 1, secondary drive module 2, main drive module 3, dual-transistor circuit 4, transformer T1, PFC chip U1, fast start circuit 1, dual-transistor drive chip U2, single-transistor drive chip U3, switch signal terminal 31, MOSFET Q1, resistor R1, resistor R2, voltage regulator DZ1, diode D10, resistor R20, resistor R21, resistor R22, resistor R23, MOSFET Q3, MOSFET Q4, synchronous rectification module 5, and synchronous rectification chip U4. Detailed Implementation

[0032] The embodiments of this utility model are described in detail below. Examples of these embodiments are shown in the accompanying drawings, wherein the same or similar reference numerals denote the same or similar elements or elements having the same or similar functions throughout. The embodiments described below with reference to the accompanying drawings are exemplary and are only used to explain this utility model, and should not be construed as limiting this utility model.

[0033] In the description of embodiments of this utility model, the terms "first" and "second" are used for descriptive purposes only and should not be construed as indicating or implying relative importance or implicitly specifying the number of indicated technical features. Thus, features defined with "first" and "second" may explicitly or implicitly include one or more of the stated features. In the description of embodiments of this utility model, "a plurality of" means two or more, unless otherwise explicitly specified.

[0034] In the description of the embodiments of this utility model, it should be noted that, unless otherwise explicitly specified and limited, the terms "installation," "connection," and "joining" should be interpreted broadly. For example, they can refer to a fixed connection, a detachable connection, or an integral connection; they can refer to a direct connection or an indirect connection through an intermediate medium; they can refer to the internal communication of two components or the interaction between two components. Those skilled in the art can understand the specific meaning of the above terms in the embodiments of this utility model according to the specific circumstances.

[0035] The following is combined Figures 1 to 8 This describes a dual-tube flyback switching power supply according to an embodiment of the present invention.

[0036] A dual-transistor flyback switching power supply includes a PFC module 1, a secondary drive module 2, a main drive module 3, a dual-transistor circuit 4, and a transformer T1; the PFC module 1 is electrically connected to the secondary drive module 2 and the main drive module 3 respectively, the secondary drive module 2 is electrically connected to the primary winding of the transformer T1 via the dual-transistor circuit 4, and the main drive module 3 is electrically connected to the primary winding of the transformer T1.

[0037] PFC module 1 consists of PFC chip U1 and its peripheral circuits. The peripheral circuits of PFC chip U1 include a fast start circuit 1, which is integrated and packaged within PFC chip U1.

[0038] The secondary drive module 2 consists of a dual-transistor drive chip U2 and its peripheral circuits, with the dual-transistor circuit 4 integrated and packaged within the dual-transistor drive chip U2;

[0039] The main drive module 3 consists of a single-transistor drive chip U3 and its peripheral circuits. The single-transistor drive chip U3 is equipped with a switch signal terminal 31, which is electrically connected to the input terminal of the dual-transistor drive chip U2.

[0040] This utility model proposes a preferred embodiment of a dual-transistor flyback switching power supply, such as... Figure 1 As shown, the dual-transistor flyback circuit architecture mainly consists of a secondary driver module 2, a main driver module 3, and a dual-transistor circuit 4. The secondary driver module 2 controls the upper switching transistor (such as a MOSFET) of the dual-transistor circuit 4, and the main driver module 3 controls the lower switching transistor of the dual-transistor circuit 4. The advantage of independently controlling the upper and lower transistors is that it reduces the voltage stress on the switching transistors, improves the efficiency of the power supply, facilitates the design of control logic, and better dissipates heat. Furthermore, the power supply with the same parameters can be designed to handle higher power requirements. Based on this, the secondary driver module 2 and the main driver module 3 preferably use a dual-transistor driver chip U2 and a single-transistor driver chip U3, respectively. The dual-transistor driver chip U2 can drive two switching transistors, and the single-transistor driver chip U3 can control both switching transistors separately by adding a switch signal terminal 31 in conjunction with the dual-transistor driver chip U2.

[0041] Meanwhile, in order to reduce the number of discrete components and the space occupied on the circuit board, and improve production efficiency, the fast start circuit 1, which is a common feature of the peripheral circuit of the PFC chip U1, is integrated and packaged into the PFC chip U1 to form a new PFC chip U1 (before integration, the connection relationship between the fast start circuit 1 and the PFC chip U1 is as follows: Figure 2 (As shown); The dual-transistor circuit 4, which is directly driven by the dual-transistor driver chip U2, is integrated and packaged within the dual-transistor driver chip U2 to form a new dual-transistor driver chip U2 (before integration, the connection relationship between the dual-transistor circuit 4 and the dual-transistor driver chip U2 is as follows: Figure 3 (As shown); thus, in the future, the production of switching power supplies can directly use the new PFC chip U1 and the new dual-transistor driver chip U2, without the need to adjust the inherent functional circuits of the chips.

[0042] Furthermore, the fast start circuit 1 includes a MOSFET Q1, resistors R1 and R2, a voltage regulator DZ1, and a diode D10; one end of resistor R1 and one end of resistor R2 are electrically connected, the other end of resistor R1 and the gate of MOSFET Q1 are electrically connected to the cathode of voltage regulator DZ1, the anode of voltage regulator DZ1 is grounded, the other end of resistor R2 is electrically connected to the drain of MOSFET Q1, the source of MOSFET Q1 is electrically connected to the anode of diode D10, and the cathode of diode D10 is electrically connected to the power supply terminal of PFC chip U1;

[0043] One end of resistor R1 is used as the new pin HV terminal of PFC chip U1 for electrical connection with the VBUS power supply bus.

[0044] In this embodiment, as Figure 4 As shown, when the fast startup circuit 1 is integrated into the PFC chip U1, it is preferable to replace resistors R4 and R5 with MOSFET Q1, resistors R1 and R2, voltage regulator DZ1, and diode D10 (e.g., Figure 4 The part within the red box is integrated into the PFC chip U1; the MOS transistor Q1 is used as the core for the fast start circuit 1, which has a faster start-up speed and less loss compared to circuits composed of resistors.

[0045] Furthermore, the PFC chip U1 has the model number OB3674.

[0046] In this embodiment, the PFC chip U1 only needs a power supply terminal (i.e., VDD) to integrate the fast startup circuit 1 inside the chip. For example, the PFC chip U1 with model number OB3674 is stable and is often selected as the PFC chip U1. Figure 4 The area outside the red box is the original internal circuitry of the OB3674 chip.

[0047] Furthermore, the dual-transistor circuit 4 includes resistors R20, R21, R22, and R23, MOSFET Q3, and MOSFET Q4; one end of resistor R22 is electrically connected to the high-order output terminal of the dual-transistor driver chip U2, the other end of resistor R22 and one end of resistor R23 are both electrically connected to the gate of MOSFET Q4, the other end of resistor R23 and the source of MOSFET Q4 are both electrically connected to the drain of MOSFET Q3, the gate of MOSFET Q3 and one end of resistor R21 are both electrically connected to one end of resistor R20, the other end of resistor R21 and the source of MOSFET Q3 are both grounded, and the other end of resistor R20 is electrically connected to the low-order output terminal of the dual-transistor driver chip U2;

[0048] The low-order output pin of the dual-transistor driver chip U2 is removed. The drain of MOSFET Q4 replaces the high-order output pin of the dual-transistor driver chip U2 as a pin, and the source of MOSFET Q4 replaces the high-voltage floating power supply terminal of the dual-transistor driver chip U2 as a pin.

[0049] In this embodiment, as Figure 5 The original internal circuit of the dual-transistor driver chip U2, such as Figure 6 To integrate the dual-transistor circuit 4 into the internal circuit of the dual-transistor driver chip U2, the low-order output terminal (LO) pin of the dual-transistor driver chip U2 is removed after integration. The drain of MOSFET Q4 replaces the high-order output terminal (HO) of the dual-transistor driver chip U2 as a pin (HV), and the source of MOSFET Q4 replaces the high-voltage floating power supply terminal of the dual-transistor driver chip U2 as a pin (VS), thus forming a new dual-transistor driver chip U2.

[0050] Furthermore, the dual-transistor driver chip U2 is model number BP6914.

[0051] In this embodiment, the preferred model of the dual-transistor driver chip U2 is BP6914, which has two built-in MOS transistors and has a high-order output terminal (HO), a high-voltage floating power supply terminal (VS), and a low-order output terminal (LO), thus meeting the integration requirements of the dual-transistor circuit 4.

[0052] Furthermore, the gate of the built-in MOS transistor in the single-transistor driver chip U3 is used as a switching signal terminal 31.

[0053] Furthermore, the single-transistor driver chip U3 is model number BP3187.

[0054] In this embodiment, the preferred model of the single-transistor driver chip U3 is BP3187, and its internal circuitry is as follows: Figure 7 As shown, since the single-transistor driver chip U3 controls the switching transistor through the built-in MOS transistor, when the single-transistor driver chip U3 is linked with the dual-transistor driver chip U2, the gate of the built-in MOS transistor of the single-transistor driver chip U3 can be brought out as the switching signal terminal 31 (SIGNAL).

[0055] Furthermore, it also includes a synchronous rectification module 5; the secondary winding of transformer T1 is electrically connected to the synchronous rectification module 5;

[0056] The synchronous rectification module 5 is an integrated package of the synchronous rectification chip U4 and its peripheral circuits.

[0057] Furthermore, the synchronous rectifier chip U4 is model number KP4050.

[0058] In this embodiment, as Figure 8 As shown, the preferred model of the synchronous rectifier chip U4 is KP4050, which is commonly used to drive the MOSFET Q6 to achieve synchronous rectification. Since this module has a single function, when the output of the switching power supply adopts synchronous rectification, the synchronous rectifier chip U4 and its peripheral circuits can be integrated and packaged into a synchronous rectifier module 5, which can be directly connected in series with the secondary winding of the transformer T1 to improve the production efficiency of the switching power supply.

[0059] Other configurations and operations of a dual-tube flyback switching power supply according to embodiments of the present invention are known to those skilled in the art and will not be described in detail here.

[0060] In this specification, the terms "embodiment," "example," etc., refer to specific features, structures, materials, or characteristics described in connection with that embodiment or example, which are included in at least one embodiment or example of the present invention. In this specification, the illustrative expressions of the above terms do not necessarily refer to the same embodiment or example. Furthermore, the specific features, structures, materials, or characteristics described may be combined in any suitable manner in one or more embodiments or examples.

[0061] Although embodiments of the present invention have been shown and described, those skilled in the art will understand that various changes, modifications, substitutions and alterations can be made to these embodiments without departing from the principles and spirit of the present invention, the scope of which is defined by the claims and their equivalents.

Claims

1. A dual-transistor flyback switching power supply, characterized in that: It includes a PFC module, a secondary drive module, a primary drive module, a dual-transistor circuit, and a transformer T1; the PFC module is electrically connected to the secondary drive module and the primary drive module respectively, the secondary drive module is electrically connected to the primary winding of the transformer T1 via the dual-transistor circuit, and the primary drive module is electrically connected to the primary winding of the transformer T1. The PFC module consists of a PFC chip U1 and its peripheral circuits. The peripheral circuits of the PFC chip U1 are equipped with a fast start circuit, which is integrated and packaged within the PFC chip U1. The secondary drive module consists of a dual-transistor drive chip U2 and its peripheral circuits, with the dual-transistor circuits integrated and packaged within the dual-transistor drive chip U2. The main drive module consists of a single-transistor drive chip U3 and its peripheral circuits. The single-transistor drive chip U3 is equipped with a switch signal terminal, which is electrically connected to the input terminal of the dual-transistor drive chip U2.

2. The dual-transistor flyback switching power supply according to claim 1, characterized in that: The fast start circuit includes a MOSFET Q1, resistors R1 and R2, a voltage regulator DZ1, and a diode D10. One end of resistor R1 and one end of resistor R2 are electrically connected. The other end of resistor R1 and the gate of MOSFET Q1 are both electrically connected to the cathode of voltage regulator DZ1. The anode of voltage regulator DZ1 is grounded. The other end of resistor R2 is electrically connected to the drain of MOSFET Q1. The source of MOSFET Q1 is electrically connected to the anode of diode D10. The cathode of diode D10 is electrically connected to the power supply terminal of PFC chip U1. One end of the resistor R1 is used as a new pin HV terminal of the PFC chip U1 for electrical connection with the VBUS power supply bus.

3. The dual-transistor flyback switching power supply according to claim 1, characterized in that: The PFC chip U1 is model OB3674.

4. The dual-transistor flyback switching power supply according to claim 1, characterized in that: The dual-transistor circuit includes resistors R20, R21, R22, and R23, MOSFET Q3, and MOSFET Q4. One end of resistor R22 is electrically connected to the high-order output terminal of the dual-transistor driver chip U2. The other end of resistor R22 and one end of resistor R23 are both electrically connected to the gate of MOSFET Q4. The other end of resistor R23 and the source of MOSFET Q4 are both electrically connected to the drain of MOSFET Q3. The gate of MOSFET Q3 and one end of resistor R21 are both electrically connected to one end of resistor R20. The other end of resistor R21 and the source of MOSFET Q3 are both grounded. The other end of resistor R20 is electrically connected to the low-order output terminal of the dual-transistor driver chip U2. The low-order output pin of the dual-transistor driver chip U2 is removed, the drain of the MOS transistor Q4 replaces the high-order output pin of the dual-transistor driver chip U2 as a pin, and the source of the MOS transistor Q4 replaces the high-voltage floating power supply terminal of the dual-transistor driver chip U2 as a pin.

5. A dual-transistor flyback switching power supply according to claim 1, characterized in that: The dual-transistor driver chip U2 is model BP6914.

6. A dual-transistor flyback switching power supply according to claim 1, characterized in that: The gate of the built-in MOS transistor in the single-transistor driver chip U3 is used as the switching signal terminal.

7. A dual-transistor flyback switching power supply according to claim 1, characterized in that: The single-transistor driver chip U3 is model BP3187.

8. A dual-transistor flyback switching power supply according to claim 1, characterized in that: It also includes a synchronous rectification module; the secondary winding of the transformer T1 is electrically connected to the synchronous rectification module; The synchronous rectification module is an integrated package of synchronous rectification chip U4 and its peripheral circuits.

9. A dual-transistor flyback switching power supply according to claim 8, characterized in that: The synchronous rectifier chip U4 is model KP4050.

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