AC-DC double-tube flyback circuit and LED dimming power supply

Abstract

The utility model discloses an AC-DC double-tube flyback circuit and an LED dimming power supply. The AC-DC double-tube flyback circuit comprises a control chip U1, resistors R5-7, MOS tubes Q1-2, diodes D3-4 and a transformer T2. A power supply pin of the control chip U1 is connected to a VDD end, an output pin of the control chip U1 is connected with a grid electrode of the MOS tube Q1 and is connected with a grid electrode of the MOS tube Q2 through a resistor R5, a sampling pin of the control chip U1 is respectively connected with a source electrode of the MOS tube Q2 and one end of a resistor R7 through a resistor R6, and a feedback pin of the control chip U1 is connected to a feedback signal; the single-drive output control chip is adopted to control the work of the MOS tube Q1 and the MOS tube Q2 at the same time, compared with a dual-drive control chip scheme, the single-drive output control chip has the advantage of being lower in cost, a new scheme is provided for low cost of flyback switching power supply products, and constant-voltage dimming and constant-current dimming switching use can be achieved through expansion on the basis of the scheme.

Description

Technical Field

[0001] The utility model relates to the technical field of LED dimming driving power supply and switching power supply, in particular to an AC-DC double-tube flyback circuit and an LED dimming power supply. Background Art

[0002] In the LED lighting industry, the flyback switching power supply has the following advantages:

[0003] 1. Cost advantage: The flyback switching power supply has a relatively simple circuit and requires fewer components, so it has certain advantages in production cost. This is an extremely attractive feature for the price-sensitive market.

[0004] 2. Wide application: Flyback switching power supplies are suitable for low-power, multi-channel output or isolated power supply applications, such as consumer electronics, adapters, etc. The market demand in these fields is huge, providing a broad space for the sales of flyback switching power supplies.

[0005] 3. Design flexibility: The output voltage of the flyback switching power supply can be higher, equal to or lower than the input voltage, which can better meet the scenarios with different voltage requirements. This design flexibility enables it to adapt to various complex application environments.

[0006] 4. Easy to implement: In comparison, the design and manufacture of flyback switching power supplies are relatively easy, and the technical threshold is low. This enables more manufacturers to enter this market, increases product supply, and promotes market competition.

[0007] 5. Market demand and consumer preference: With the popularization and upgrading of consumer electronic products, the demand for small, efficient and low-cost switching power supplies is growing. Flyback switching power supplies just meet these demands and are therefore more popular among consumers in the market.

[0008] Because of these unique advantages, its application in switching power supplies is very common. However, the problems of large leakage inductance, high switching tube peak, low efficiency and large output ripple of single-tube flyback switching power supplies also limit its use. Flyback switching power supplies have a large market share in the LED power supply market, so a flyback topology with low cost, high efficiency and support for ultra-high voltage input is very important. Utility Model Content

[0009] The utility model aims to solve at least one of the technical problems existing in the prior art. To this end, the utility model proposes an AC-DC double-tube flyback circuit and an LED dimming power supply.

[0010] An embodiment of the utility model solves the technical problem by adopting a technical solution: an AC-DC double-tube flyback circuit, including a control chip U1, resistors R5-7, MOS tubes Q1-2, diodes D3-4 and a transformer T2;

[0011] The power pin of the control chip U1 is connected to the VDD terminal, the output pin of the control chip U1 is connected to the gate of the MOS tube Q1 and is connected to the gate of the MOS tube Q2 via the resistor R5, the sampling pin of the control chip U1 is connected to the source of the MOS tube Q2 and one end of the resistor R7 via the resistor R6, and the feedback pin of the control chip U1 is connected to the feedback signal;

[0012] The drain of the MOS transistor Q1 is connected to the input signal and is respectively connected to the drain of the MOS transistor Q2 and one end of the first winding of the transformer T2 via the diode D3. The source of the MOS transistor Q1 is connected to the other end of the first winding of the transformer T2 and is respectively connected to the other end of the resistor R7 and the PGND end via the diode D4.

[0013] As one of the preferred embodiments of the present utility model, an AC-DC dual-tube flyback circuit further includes an isolation module connected between the output pin of the control chip U1 and the gate of the MOS tube Q1.

[0014] As one of the preferred embodiments of the utility model, the isolation module includes a resistor R1-3, a capacitor C1-2, a diode D1 and a transformer T1. The resistor R3 and the capacitor C1 are connected in series to the output pin of the control chip U1 and one end of the primary winding of the transformer T1. The other end of the primary winding of the transformer T1 is connected to the PGND end. One end of the secondary winding of the transformer T1 is respectively connected to one end of the resistor R1 and one end of the capacitor C2. The other end of the resistor R1 is respectively connected to the other end of the capacitor C2, one end of the resistor R2 and the cathode of the diode D1. The other end of the resistor R2 is connected to the gate of the MOS tube Q1. The anode of the diode D2 is respectively connected to the other end of the secondary winding of the transformer T1 and the source of the MOS tube Q1.

[0015] An LED dimming power supply comprises the AC-DC double-tube flyback circuit.

[0016] The beneficial effects of the utility model are as follows: an AC-DC double-tube flyback circuit and an LED dimming power supply, the AC-DC double-tube flyback circuit comprises a control chip U1, resistors R5-7, MOS tubes Q1-2, diodes D3-4 and a transformer T2; the power pin of the control chip U1 is connected to the VDD terminal, the output pin of the control chip U1 is connected to the gate of the MOS tube Q1 and is connected to the gate of the MOS tube Q2 via the resistor R5, the sampling pin of the control chip U1 is respectively connected to the source of the MOS tube Q2 and one end of the resistor R7 via the resistor R6, the feedback pin of the control chip U1 is connected to the feedback signal; the drain of the MOS tube Q1 is connected to the The input signal is connected to the drain of the MOS tube Q2 and one end of the first winding of the transformer T2 respectively through the diode D3, the source of the MOS tube Q1 is connected to the other end of the first winding of the transformer T2 and is connected to the other end of the resistor R7 and the PGND end respectively through the diode D4; by adopting a single-drive output control chip to simultaneously control the work of the MOS tube Q1 and the MOS tube Q2, compared with the dual-drive control chip solution, it has the advantage of lower cost, and proposes a new solution for the low cost of flyback switching power supply products, and on this basis, it can be expanded to realize the switching of constant voltage dimming and constant current dimming. BRIEF DESCRIPTION OF THE DRAWINGS

[0017] The above and / or additional aspects and advantages of the present invention will become apparent and easily understood from the description of the embodiments in conjunction with the following drawings, in which:

[0018] Figure 1 This is a principle block diagram of an LED dimming power supply;

[0019] Figure 2 It is a circuit schematic diagram of an LED dimming power supply;

[0020] Figure 3 The figure is a circuit schematic diagram of an AC-DC dual-tube flyback circuit. DETAILED DESCRIPTION

[0021] This section will describe in detail the specific embodiments of the utility model. The preferred embodiments of the utility model are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and the overall technical solution of the utility model, but it cannot be understood as a limitation on the protection scope of the utility model.

[0022] In the description of the present utility model, the meaning of "more than" is more than two, "greater than", "less than", "exceed" etc. are understood to exclude the number itself, and "above", "below", "within" etc. are understood to include the number itself. If there is a description of "first" or "second", it is only used for the purpose of distinguishing technical features, and cannot be understood as indicating or implying relative importance or implicitly indicating the number of the indicated technical features or implicitly indicating the order of the indicated technical features.

[0023] In the description of the present invention, it should be understood that descriptions involving orientation, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings, and are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation, and therefore cannot be understood as a limitation on the present invention.

[0024] In the present invention, unless otherwise clearly defined, the words "set", "install", "connect" and the like should be understood in a broad sense, for example, they can be directly connected or indirectly connected through an intermediate medium; they can be fixedly connected or detachably connected or integrally formed; they can be mechanically connected; they can be the internal connection of two elements or the interaction relationship between two elements. Those skilled in the art can reasonably determine the specific meanings of the above words in the present invention in combination with the specific content of the technical solution.

[0025] Reference Figures 1 to 3 , an LED dimming power supply, comprising an EM I circuit 10, a bridge rectifier and power factor correction circuit 20, a secondary rectifier filter circuit 40, a dimming control circuit 50, a voltage and current feedback circuit 60 and the AC-DC double-tube flyback circuit 30;

[0026] The EM I circuit 10 and the bridge rectifier and power factor correction circuit 20 are connected in series between the mains and the AC-DC double-switch flyback circuit 30;

[0027] The AC-DC dual-tube flyback circuit 30 and the secondary rectifier filter circuit 40 form an AC-DC flyback topology;

[0028] The voltage and current feedback circuit 60 is connected between the secondary rectifier filter circuit 40 and the AC-DC double-switch flyback circuit 30 to obtain the output voltage and output current;

[0029] The dimming control circuit 50 is connected between the secondary rectifier filter circuit 40 and the lamp and receives the dimming signal. When the dimming signal is input, the MCU makes a corresponding output according to the change of the dimming signal to drive the MOS tube Q3 to achieve the purpose of dimming.

[0030] In the AC-DC double-tube flyback circuit 30, the AC-DC double-tube flyback circuit 30 includes a control chip U1, resistors R5-7, MOS tubes Q1-2, diodes D3-4 and a transformer T2;

[0031] The power pin of the control chip U1 is connected to the VDD terminal, the output pin of the control chip U1 is connected to the gate of the MOS tube Q1 and is connected to the gate of the MOS tube Q2 via the resistor R5, the sampling pin of the control chip U1 is connected to the source of the MOS tube Q2 and one end of the resistor R7 via the resistor R6, and the feedback pin of the control chip U1 is connected to the feedback signal;

[0032] The drain of the MOS transistor Q1 is connected to the input signal and is respectively connected to the drain of the MOS transistor Q2 and one end of the first winding of the transformer T2 via the diode D3. The source of the MOS transistor Q1 is connected to the other end of the first winding of the transformer T2 and is respectively connected to the other end of the resistor R7 and the PGND end via the diode D4.

[0033] Specifically, the pin 1 of the control chip U1 is the ground, the pin 4 of the control chip U1 is the power input, and the pin 5 of the control chip U1 output simultaneously controls the operation of the MOS tube Q1 and the MOS tube Q2; the AC power module EM After rectification and filtering by the I circuit 10 and the bridge rectifier and power factor correction circuit 20, the DC is input to the drain of the MOS tube Q1. At this time, the 5-pin of the control chip U1 outputs a driving signal to the MOS tube Q1 and the MOS tube Q2. At this time, the MOS tube Q1 and the MOS tube Q2 are almost synchronously turned on to charge the winding T2A of the transformer T2. When the control chip U1 stops outputting the driving signal, the MOS tube Q1 and the MOS tube Q2 are almost synchronously turned off, and the winding T2A of the transformer T2 begins to release energy, generating a reverse electromotive force, and the winding T2B of the transformer T2 is electromagnetically induced, which is rectified and filtered by the secondary rectification and filtering circuit 40 and then output. At this time, the leakage inductance of the winding T2A of the entire transformer T2 is fed back to the DC input through the diodes D3 and D4 in the AC-DC dual-tube flyback circuit 30, and the voltage difference across the sampling resistor R7 of the 3-pin of the control chip U1 is realized to achieve primary current limiting.

[0034] Furthermore, an AC-DC dual-tube flyback circuit also includes an isolation module 70 connected between the output pin of the control chip U1 and the gate of the MOS tube Q1. This is because the source of the MOS tube Q1 is floating, and the isolation module 70 needs to be set at the source of the MOS tube Q1 to isolate the control circuit from the main circuit. As a preferred embodiment of the isolation module 70, the isolation module 70 includes a resistor R1-3, a capacitor C1-2, a diode D1 and a transformer T1. The resistor R3 and the capacitor C1 are connected in series to the output pin of the control chip U1 and one end of the primary winding of the transformer T1. The other end of the primary winding of the transformer T1 is connected to the PGND end. One end of the secondary winding of the transformer T1 is respectively connected to one end of the resistor R1 and one end of the capacitor C2. The other end of the resistor R1 is respectively connected to the other end of the capacitor C2, one end of the resistor R2 and the cathode of the diode D1. The other end of the resistor R2 is connected to the gate of the MOS tube Q1. The anode of the diode D2 is respectively connected to the other end of the secondary winding of the transformer T1 and the source of the MOS tube Q1.

[0035] In another embodiment, referring to Figure 2 In the voltage and current feedback circuit 60, the 8th pin of the comparator U2A is the ground, the 6th pin of the comparator U2A is the power input, and the 1st pin of the comparator U2A is the reference voltage pin; the output voltage is sampled and filtered by the resistor R12, the resistor R13, and the capacitor C4, and then input to the 4th pin of the comparator U2A and compared with the 1st pin of the comparator U2A. The output voltage can be changed by changing the resistance values ​​of the resistors R12 and R13; and the output current is the voltage difference between the two ends of the resistor R4, and is sent to the 2nd pin of the comparator U2B through the resistor R8. The reference voltage is sent to the pin 2 of the comparator U2B through the resistors R10 and R13. After voltage division and filtering by R11 and capacitor C3, the input is input to pin 3 of comparator U2B for comparison to realize secondary current limiting. The current limiting function can be realized by changing the resistance values ​​of resistors R10 and R11. After sampling and comparing the output voltage and output current, the output voltage is output through pin 5 of comparator U2A and pin 7 of comparator U2B to control the brightness change of the light emitting diode end of optocoupler DU1. The transistor end of optocoupler DU1 changes according to the received brightness change, thereby controlling the working state of the control chip U1 in the AC-DC dual-tube flyback circuit 30 and realizing the primary and secondary signal exchange.

[0036] In the utility model, the advantage of the utility model is that by adopting a single-drive output control chip to simultaneously control the operation of the MOS tube Q1 and the MOS tube Q2, compared with the dual-drive control chip solution, it has the advantage of lower cost, and proposes a new solution for the low cost of flyback switching power supply products, and on this basis, by expanding, constant voltage dimming and constant current dimming switching can be realized.

[0037] Of course, the present invention is not limited to the above-mentioned embodiments, and technicians familiar with the field may make equivalent modifications or substitutions without violating the spirit of the present invention. These equivalent modifications and substitutions are all included in the scope defined by the claims of this application.

Claims

1. An AC-DC double-switch flyback circuit, characterized in that: It includes a control chip U1, resistors R5-7, MOS tubes Q1-2, diodes D3-4 and transformer T2; The power pin of the control chip U1 is connected to the VDD terminal, the output pin of the control chip U1 is connected to the gate of the MOS tube Q1 and is connected to the gate of the MOS tube Q2 via the resistor R5, the sampling pin of the control chip U1 is connected to the source of the MOS tube Q2 and one end of the resistor R7 via the resistor R6, and the feedback pin of the control chip U1 is connected to the feedback signal; The drain of the MOS transistor Q1 is connected to the input signal and is respectively connected to the drain of the MOS transistor Q2 and one end of the first winding of the transformer T2 via the diode D3. The source of the MOS transistor Q1 is connected to the other end of the first winding of the transformer T2 and is respectively connected to the other end of the resistor R7 and the PGND end via the diode D4.

2. The AC-DC double-switch flyback circuit according to claim 1, characterized in that: It also includes an isolation module (70) connected between the output pin of the control chip U1 and the gate of the MOS tube Q1.

3. The AC-DC double-switch flyback circuit according to claim 2, characterized in that: The isolation module (70) comprises a resistor R1-3, a capacitor C1-2, a diode D1 and a transformer T1. The resistor R3 and the capacitor C1 are connected in series to an output pin of a control chip U1 and connected to one end of a primary winding of the transformer T1. The other end of the primary winding of the transformer T1 is connected to a PGND terminal. One end of a secondary winding of the transformer T1 is respectively connected to one end of the resistor R1 and one end of a capacitor C2. The other end of the resistor R1 is respectively connected to the other end of the capacitor C2, one end of the resistor R2 and a cathode of the diode D1. The other end of the resistor R2 is connected to a gate of a MOS tube Q1. The anode of the diode D2 is respectively connected to the other end of the secondary winding of the transformer T1 and a source of the MOS tube Q1.

4. An LED dimming power supply, characterized in that: The invention comprises the AC-DC double-switch flyback circuit as described in any one of claims 1 to 3.

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