LLC constant-voltage LED driving power supply

Abstract

The utility model relates to the technical field of LED driving power supplies, in particular to an LLC constant-voltage LED driving power supply, which comprises an LM321 comparator, a chip U2, a TL431 constant-voltage ring and a transformer J1, when the power supply is provided with a rated load, only the TL431 constant-voltage ring works, a first pin of the LM321 comparator is grounded through a resistor RS5 and a capacitor C31, a capacitor C34, a resistor R54 and a resistor R53 are bridged between the first pin and a second pin of the LM321 comparator, and the first pin and the second pin of the LM321 comparator are grounded through the resistor RS5 and the capacitor C31. The capacitor C34, the resistor R54 and the resistor R53 are connected in parallel, a third pin of the LM321 comparator is connected with the capacitor C26 in series through the resistor R56, the capacitor C33 and the resistor R55, and a fourth pin of the LM321 comparator is coupled with the resistor R44 through the diode D7; according to the utility model, a resistor R1, a resistor R2, an LM321 comparator and peripheral devices form a current detection ring, and the current detection ring and a TL431 voltage ring form a constant-voltage current limiting circuit; the whole current has short-circuit protection and high-precision overload protection functions.

Description

TECHNICAL FIELD

[0001] The utility model relates to LED drive power supply technical field especially relates to a LLC constant voltage LED drive power supply. BACKGROUND

[0002] When the conventional LLC constant voltage power supply output is overloaded, the current size of the primary side is usually detected by the chip CS (current sense) pin to determine whether the output is overloaded, the circuit has the defects of low detection precision, and the detection precision completely depends on the chip itself (for example, the CS threshold voltage precision of a certain large factory LLC controller is ± 20%); Especially when LLC is applied to small power (below 100W) circuit, the output overcurrent range under full voltage (90-277VAC) cannot meet the requirements, some products add various compensation circuits on the chip CS pin, which will lead to complex circuit, high cost, high failure rate and other problems.

[0003] In order to solve the above problems, we propose a LLC constant voltage LED drive power supply. CONTENT OF THE UTILITY MODEL

[0004] In view of the defects of the prior art, the utility model provides a LLC constant voltage LED drive power supply to solve the technical problems of "when the conventional LLC constant voltage power supply output is overloaded, the current size of the primary side is usually detected by the chip CS (current sense) pin to determine whether the output is overloaded, the circuit has the defects of low detection precision, and the detection precision completely depends on the chip itself (for example, the CS threshold voltage precision of a certain large factory LLC controller is ± 20%), and it is difficult to debug; Especially when LLC is applied to small power (below 100W) circuit, the output overcurrent range under full voltage (90-277VAC) cannot meet the requirements, some products add various compensation circuits on the chip CS pin, which will lead to complex circuit, high cost, high failure rate and other problems".

[0005] To achieve the above purpose, the utility model realizes through the following technical schemes:

[0006] A LLC constant voltage LED drive power supply, comprising a LM321 comparator, a chip U2, a TL431 constant voltage ring and a transformer J1, when the power supply carries rated load, only the TL431 voltage ring works;

[0007] The first pin of the LM321 comparator is connected to ground through a resistor R5 and a capacitor C31, a capacitor C34, a resistor R54 and a resistor R53 are connected between the first pin and the second pin of the LM321 comparator, the capacitor C34, the resistor R54 and the resistor R53 are connected in parallel, the third pin of the LM321 comparator is connected in series with a resistor R56, a capacitor C33, a resistor R55 and a capacitor C26, the fourth pin of the LM321 comparator is connected with a resistor R44 through a diode D7, and the resistor R44 is connected in series with a TL431 constant voltage ring through a photo-coupler PC1-A;

[0008] The LM321 comparator, the current detection resistors R1 and R2 and peripheral devices form a current detection ring, and together with the TL431 voltage ring form a constant voltage current limiting circuit, and the entire current has short circuit protection and high precision overload protection functions;

[0009] The TL431 constant voltage ring is connected with the second pin of the photo-coupler PC1-A through a resistor R51, a capacitor C27 and a resistor R47, the photo-coupler PC1-A is connected with the resistor R44, and the TL431 constant voltage ring is connected with the first pin of the photo-coupler PC1-A through resistors R50 and R45;

[0010] The primary side T1-A of the transformer J1 is connected with a resistor R1 through a diode D2, the resistor R1 is connected with a resistor R2, and then connected with a resistor R37, the primary side T1-B of the transformer J1 is connected with a capacitor C26 through a resistor R49, when the power supply carries a rated load, only the TL431 voltage ring works, when the load becomes heavier, that is, the output current becomes larger, the voltage difference of the current detection resistor R1 connected with the resistor R2 reaches a set value, that is, the value obtained by the same direction input end of the LM321 comparator through resistance division, which will make the LM321 comparator output a low level, so that the input current of the photo-coupler increases, the output current of the photo-coupler increases, the voltage of the FB pin of the input chip U2 fed back is reduced, to reduce the output duty cycle of the chip U2, if the load is further increased, the protection function of the chip U2 will be triggered, the chip U2 outputs or enters off mode, so as to realize the overload protection well, under the power reduction of R1 and R2, the overload point can be set at will, the overcurrent point precision depends on the sampling precision of the resistors R1, R2 and the LM321 comparator, the resistance error value of the resistor can be selected as ±1%, and the sampling precision of the LM321 comparator is uV level, so the overcurrent point precision is high, and the problem of low current precision of the front-stage RC detection circuit in the LLC resonant circuit is solved;

[0011] When the output is overloaded, the voltage difference between R1 and R2 current detection resistors reaches the set value, which makes the LM321 comparator output a low level, so that the input current of the optocoupler increases, the output current of the optocoupler increases, the voltage fed back to the input chip FB pin is pulled down, and the chip output duty cycle is reduced.

[0012] The fifth pin of the chip U2 is coupled with the fourth pin of the optocoupler PC1-A.

[0013] As a preferred technical scheme of the utility model, the resistance R49 is connected with the capacitor C2S and grounded.

[0014] As a preferred technical scheme of the utility model, the resistance R56 is connected with the capacitor C33 and grounded.

[0015] As a preferred technical scheme of the utility model, the TL431 constant voltage ring is grounded through the resistance R48.

[0016] As a preferred technical scheme of the utility model, the resistance R45 is connected with the resistance R50 and coupled with the transformer J1.

[0017] As a preferred technical scheme of the utility model, the optocoupler PC1-A is connected with the capacitor C14 and grounded.

[0018] The utility model provides a kind of LLC constant voltage LED driving power supply, with following beneficial effects:

[0019] 1, when output is overloaded, the voltage difference between R1 and R2 current detection resistors reaches the set value, which makes the LM321 comparator output a low level, so that the input current of the optocoupler increases, the output current of the optocoupler increases, the voltage fed back to the input chip FB pin is pulled down, and the chip output duty cycle is reduced, solve the "conventional LLC constant voltage power output overload, usually rely on chip CS (current sense) foot detects the current size of primary side to judge whether output is overloaded, the detection precision of this circuit is low, and detection precision is completely dependent on chip itself (for example, the CS threshold voltage precision of certain large factory LLC controller is ±20%) " problem;

[0020] 2, resistance R1, R2 and LM321 comparator and peripheral device constitute a current detection ring, and TL431 voltage ring is commonly composed of constant voltage current limiting circuit, whole circuit is simple, with short-circuit protection, high-precision overload protection function, solve "LLC is applied to small power (100W below) circuit, full voltage (90-277VAC) under output overcurrent range cannot meet the requirements, some products are added with various compensation circuits on chip CS foot, which will lead to complex circuit, high cost and high failure rate " and other problems. BRIEF DESCRIPTION OF DRAWINGS

[0021] Fig. 1 It is the schematic diagram of the circuit structure of the utility model;

[0022] Fig. 2 It is the normal current detection circuit of the utility model. DETAILED DESCRIPTION

[0023] In order to make the technical problem, technical scheme and beneficial effect of the utility model to be solved more clearly, the utility model is further described in detail in the following with the drawings and examples.It should be understood that the specific examples described here are only used to explain the utility model, and are not used to limit the utility model.

[0024] Therefore, one feature indicated in the specification will be used to explain one feature of one embodiment of the utility model, and it is not suggested that each embodiment of the utility model must have the explained feature.In addition, it should be noted that the specification describes many features.Although certain features can be combined together to show possible system design, these features can also be used in other combinations which are not explicitly explained.Thus, unless otherwise explained, the explained combination is not intended to limit.

[0025] The principle and structure of the utility model are described in detail in the following with the drawings and examples:

[0026] Reference Figs. 1-2 An LLC constant voltage LED driving power supply, comprising an LM321 comparator, a chip U2, a TL431 constant voltage ring and a transformer J1, when the power supply is with rated load, only the TL431 voltage ring works;

[0027] One pin of the LM321 comparator is grounded through a resistor RS5 and a capacitor C31, a capacitor C34 and a resistor R54 and a resistor R53 are connected in parallel between the one pin and the two pin of the LM321 comparator, the three pin of the LM321 comparator is connected in series with a resistor R56, a capacitor C33, a resistor R55 and a capacitor C26, the four pin of the LM321 comparator is coupled with a resistor R44 through a diode D7, and the resistor R44 is connected in series with the TL431 constant voltage ring through a photo-coupler PC1-A;

[0028] The LM321 comparator, current detection resistors R1 and R2 and peripheral devices form a current detection ring, and together with the TL431 voltage ring, form a constant voltage current limiting circuit, and the whole current has short circuit protection and high precision overload protection functions.

[0029] The TL431 constant voltage ring is coupled with the No. 2 pin of the photocoupler PC1-A through the resistor R51, the capacitor C27 and the resistor R47, the photocoupler PC1-A is connected with the resistor R44, the TL431 constant voltage ring is coupled with the No. 1 pin of the photocoupler PC1-A through the resistor R50 and R45, the primary side T1-A of the transformer J1 is coupled with the resistor R1 through the diode D2, the resistor R1 is connected with the resistor R2 and then coupled with the resistor R37, the primary side T1-B of the transformer J1 is coupled with the capacitor C26 through the resistor R49;

[0030] When the output is overloaded, the voltage difference on the current detection resistors R1 and R2 reaches the set value, which makes the LM321 comparator output a low level, so that the input current of the photocoupler increases, the output current of the photocoupler increases, the voltage feedback to the input chip FB pin is reduced, and the chip output duty cycle is reduced.

[0031] The No. 5 pin of the chip U2 is coupled with the No. 4 pin of the photocoupler PC1-A.

[0032] The resistor R49 is connected with the capacitor C2S and then grounded.

[0033] The resistor R56 is connected with the capacitor C33 and then grounded.

[0034] The TL431 constant voltage ring is grounded through the resistor R48.

[0035] The resistor R45 is connected with the resistor R50 and then coupled with the transformer J1.

[0036] The photocoupler PC1-A is connected with the capacitor C14 and then grounded.

[0037] Specifically, the current detection resistors R1 and R2, the LM321 comparator and the peripheral devices form a current detection ring, and the TL431 voltage ring together forms a constant voltage current limiting circuit. The whole current has short circuit protection and high precision overload protection function.

[0038] When the power supply is rated load, only the TL431 voltage loop is working; when the load is heavier and the output current is larger, the voltage difference between the current detection resistor R1 and the resistor R2 reaches the value set by us, that is, the value obtained by the same input end of the LM321 comparator through resistor voltage division, which will make the LM321 comparator output a low level, increase the input current of the optocoupler, increase the output current of the optocoupler, and reduce the voltage of the FB pin of the input chip U2, thereby reducing the output duty cycle of the chip U2, and if the load is further increased, the protection function of the chip U2 will be triggered; the chip U2 outputs or enters the off mode, thereby realizing the overload protection well, and under the power reduction of R1 and R2, the overload point can be set at will; the overcurrent point precision depends on the resistors R1 and R2 and the sampling precision of the LM321 comparator, the resistors can be selected to have a resistance error value of ±1%, and the sampling precision of the LM321 comparator is in the order of uV, so the overcurrent point precision is high, and the problem of low current precision of the RC detection circuit in the LLC resonant circuit is solved.

[0039] The above is only a specific implementation of the present application, but the protection scope of the present application is not limited thereto, and any skilled person in the art can easily think of various equivalent modifications or replacements within the technical range disclosed by the present application, and these modifications or replacements should be covered within the protection scope of the present application. Therefore, the protection scope of the present application should be subject to the protection scope of the claims.

Claims

1. An LLC constant-voltage LED power supply, comprising an LM321 comparator, a chip U2, a TL431 constant-voltage ring and a transformer J1, characterized in that, a No. 1 pin of the LM321 comparator is grounded through a resistor RS5 and a capacitor C31, a capacitor C34, a resistor R54 and a resistor R53 are connected in parallel between the No. 1 pin and a No. 2 pin of the LM321 comparator, a No. 3 pin of the LM321 comparator is connected in series with a resistor R56, a capacitor C33, a resistor R55 and a capacitor C26, a No. 4 pin of the LM321 comparator is coupled with a resistor R44 through a diode D7, and the resistor R44 is connected in series with a photo-coupler PC1-A and the TL431 constant-voltage ring; the TL431 constant-voltage ring is coupled with a resistor R51, a capacitor C27 and a resistor R47 and a No. 2 pin of the photo-coupler PC1-A, the photo-coupler PC1-A is connected in parallel with the resistor R44, and the TL431 constant-voltage ring is coupled with a resistor R50 and a resistor R45 and a No. 1 pin of the photo-coupler PC1-A; a primary side T1-A of the transformer J1 is coupled with a resistor R1 through a diode D2, the resistor R1 is connected in parallel with a resistor R2 and coupled with a resistor R37, and a primary side T1-B of the transformer J1 is coupled with a resistor R49 and a capacitor C26; a No. 5 pin of the chip U2 is coupled with a No. 4 pin of the photo-coupler PC1-A.

2. The LLC constant voltage LED driver power supply according to claim 1, characterized in that, the resistor R49 is connected in parallel with a capacitor C2S and grounded.

3. The LLC constant voltage LED driver power supply of claim 1, wherein, the resistor R56 is connected in parallel with the capacitor C33 and grounded.

4. The LLC constant voltage LED driver power supply of claim 1, wherein, the TL431 constant-voltage ring is grounded through a resistor R48.

5. The LLC constant voltage LED driver power supply of claim 1, wherein, the resistor R45 is connected in parallel with the resistor R50 and coupled with the transformer J1.

6. The LLC constant voltage LED driver power supply of claim 1, wherein, the photo-coupler PC1-A is connected in parallel with a capacitor C14 and grounded.

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