A low-temperature-drift multi-channel LED constant current driving circuit with temperature compensation function

Abstract

The utility model discloses a kind of low temperature drift's multi-channel LED constant current drive circuit with temperature compensation function, including voltage input end, LED load, constant current drive circuit and temperature compensation circuit, temperature compensation circuit is provided with NTC thermistor R9 and triode Q8, utilize common constant current drive circuit to realize the constant current drive to LED load, make the luminous intensity of LED stable, LED's luminous intensity will not appear with the fluctuation of input voltage and increase or reduce, and add temperature compensation circuit, cooperate constant current drive circuit, not only can be realized when the use environment temperature changes, the current size of LED is always unchanged, almost no temperature drift, the brightness of LED becomes extremely stable, moreover, the current value precision of lighting to stable state is extremely high, basically no error, by setting the maximum current value required under high temperature and the parameter of each component of temperature compensation circuit, the brightness when LED just lights up can also be accurately set, to realize current compensation function.

Description

Technical Field

[0001] This utility model relates to the field of LED driver circuit technology, specifically to a multi-channel LED constant current driver circuit with low temperature drift and temperature compensation function. Background Technology

[0002] To ensure constant brightness and prevent brightness fluctuations due to input voltage variations, LEDs are typically driven using constant current circuits. Among the various constant current circuits available, transistor-based constant current circuits are highly favored due to their low cost, simple circuitry, and wide range of brand options.

[0003] Please refer to Chinese utility model patent CN210807724U, which discloses four types of LED constant current control circuits, and the problems are as follows:

[0004] Please refer to the appendix to the instruction manual with publication number CN210807724U. Figure 1 The first calculation doesn't consider fluctuations in the LED's input voltage (i.e., the LED's anode). This means the current flowing through the LED will still vary significantly, resulting in large deviations in the LED's brightness. Brightness increases with higher voltage and decreases with lower voltage. Furthermore, it doesn't account for changes in the transistor's Vbe voltage. Because the control power supply voltage remains constant, the resistance values ​​of resistors R1 and R2 change minimally with temperature, and Vb can be considered a constant voltage. led = (Vb - Vbe) / R3, where Vb and R3 remain constant. When the circuit is working normally, the junction temperature of the transistor gradually increases, and Vbe will increase with the increase of the junction temperature. Therefore, Ve and I... led The value will gradually decrease as the junction temperature of the transistor increases.

[0005] Please refer to the appendix to the instruction manual with publication number CN210807724U. Figure 2 I led =(Vcc-Vled) / (R3+RDSON)≈(Vcc-VLED) / R3, the constant current accuracy is relatively low.

[0006] Please refer to the appendix to the instruction manual with publication number CN210807724U. Figure 3 I led ≈(Vb+Txη-Vbe) / R3, where η is the temperature drift coefficient, and Vb is controlled by the Zener diode, resulting in significant temperature drift.

[0007] Please refer to Figure 4, I of the specification with publication number CN210807724U. led ≈Vbe / R3, severe temperature drift, relatively expensive.

[0008] In general, most existing LED constant current drive circuits based on transistors suffer from problems such as LED brightness varying with voltage fluctuations, and significant temperature drift due to the decrease in transistor Vbe with increasing temperature. led The problem of reduction. Utility Model Content

[0009] In view of this, the present invention provides a multi-channel LED constant current drive circuit with low temperature drift and temperature compensation function.

[0010] The technical solution is as follows:

[0011] The first aspect of this application relates to a low-temperature drift multi-channel LED constant current driving circuit with temperature compensation function, including at least one LED constant current driving circuit. Each LED constant current driving circuit is provided with an LED load whose positive terminal is connected to the voltage input terminal and a constant current driving circuit connected to the negative terminal of the LED load. Each constant current driving circuit is also connected to the voltage input terminal. It also includes a temperature compensation circuit, which is provided with an NTC thermistor R9. One end of the NTC thermistor R9 is grounded, and the other end is connected to the voltage input terminal after being connected in series with a resistor R10. The common terminal of the NTC thermistor R9 and the resistor R10 is connected to the base of a transistor Q8. The collector of the transistor Q8 is connected to each constant current driving circuit, and the emitter of the transistor Q8 is connected to the ground after being connected in series with a resistor R16.

[0012] The above-mentioned low-temperature drift multi-channel LED constant current drive circuit with temperature compensation function utilizes existing constant current drive circuits to achieve constant current drive for LED loads. When the input voltage of the LED fluctuates, the current flowing through the LED remains unchanged, thus stabilizing the LED's luminous intensity and preventing it from increasing or decreasing with fluctuations in input voltage. A temperature compensation circuit composed of NTC thermistors R9 and R10, along with the constant current drive circuit, ensures that the LED current remains constant despite changes in ambient temperature, with almost no temperature drift and extremely stable LED brightness. Furthermore, the accuracy of the current value from lighting to a stable state is extremely high, with virtually no error. By setting the maximum current value required at high temperatures and the parameters of each component in the temperature compensation circuit, the brightness of the LED at initial lighting can be precisely set, thus achieving current compensation. Moreover, the temperature compensation circuit can compensate for the current during the lighting to a stable state, and the derating range is adjustable, solving the problem of regulatory failure due to LED luminous decay during regulatory certification.

[0013] In some implementations, a three-terminal adjustable shunt regulator D1 with its positive terminal grounded is also included, wherein the negative terminal of the three-terminal adjustable shunt regulator D1 is connected in series with a resistor R4 and then connected to the voltage input terminal.

[0014] Each constant current drive circuit is equipped with at least one transistor Q4 whose collector is simultaneously connected to the negative terminal of the corresponding LED load. The base of each transistor Q4 is connected to the collector of a transistor Q8. The common terminal of the collector of the transistor Q8 and the base of each transistor Q4 is connected to the common terminal of the negative terminal of the three-terminal adjustable shunt regulator D1 and the resistor R4. The emitter of each transistor Q4 is connected to one end of the corresponding current-limiting resistor unit. The other end of each current-limiting resistor unit is grounded. The reference voltage terminal of the three-terminal adjustable shunt regulator D1 is connected in series with a resistor R11 and then connected to the common terminal of the emitter of one of the transistors Q4 and the corresponding current-limiting resistor unit. This reference voltage terminal is also connected in series with a capacitor C15 and then grounded.

[0015] In some embodiments, each current-limiting resistor unit consists of at least one resistor R22, with the emitter of each transistor Q4 connected to one end of each resistor R22 in the corresponding current-limiting resistor unit, and the other end of each resistor R22 grounded.

[0016] In some embodiments, a capacitor C4 is connected in parallel across both ends of the LED load.

[0017] In some embodiments, the LED load consists of at least one light-emitting diode LED1 connected in series with its positive and negative terminals connected in sequence. The positive terminal of the first LED1 is connected to the voltage input terminal, and the negative terminal of the last LED1 is connected to the collector of each transistor Q4 in the corresponding constant current drive circuit.

[0018] In some embodiments, a single-cathode / all-cathode circuit is also included. The LED load consists of two groups. The single-cathode / all-cathode circuit includes a common-cathode fast recovery diode Q12, a MOSFET Q2, and a MOSFET Q3. The common cathode of the common-cathode fast recovery diode Q12 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to the negative terminal of a three-terminal adjustable shunt regulator D1. The collector of transistor Q8 is connected to the common terminal of the bases of all transistors Q4. The collector is also connected in series with a capacitor C7 and then grounded. The emitter of transistor Q7 is grounded. The common-cathode... The two anodes of the fast recovery diode Q12 are connected to the drains of MOSFET Q2 and MOSFET Q3, respectively. The two anodes are also connected in series with resistors R6 and R5, respectively, and then connected to the voltage input terminal. The gate of MOSFET Q2 is connected in series with resistor R8 and then connected to the common terminal of the negative terminal of one of the LED loads and the collector of the corresponding transistor Q4. The gate of MOSFET Q3 is connected in series with resistor R7 and then connected to the common terminal of the negative terminal of the other LED load and the collector of the corresponding transistor Q4. The sources of MOSFETs Q2 and Q3 are both grounded. Attached Figure Description

[0019] Figure 1 This is a schematic diagram of a multi-channel LED constant current drive circuit.

[0020] Figure 2 The circuit diagram of a multi-LED constant current drive circuit when no single-LED-to-all-LED-off circuit is set up;

[0021] Figure 3 The circuit diagram shows the constant current drive circuit for multiple LEDs when a circuit with one LED extinguishing and all LEDs extinguishing is set up. Detailed Implementation

[0022] The present invention will be further described below with reference to the embodiments and accompanying drawings.

[0023] like Figure 1 and Figure 2 As shown, a multi-channel LED constant current drive circuit with temperature compensation function and low temperature drift mainly includes a voltage input terminal 1, a temperature compensation circuit 4, and at least one LED constant current drive circuit.

[0024] Each LED constant current drive circuit includes an LED load 2 and a constant current drive circuit 3. The positive terminal of the LED load 2 is connected to the voltage input terminal 1, and the negative terminal of the LED load 2 is connected to the constant current drive circuit 3. Each constant current drive circuit 3 is also connected to the voltage input terminal 1. Each constant current drive circuit 3 implements constant current drive control for the LED load 2.

[0025] In this embodiment, each LED load 2 is composed of at least one LED1 connected in series with its positive and negative terminals connected in sequence. The parameters of each LED1 are the same, and the number of LED1 in the LED load 2 is determined according to actual needs.

[0026] Furthermore, a capacitor C4 is connected in parallel across both ends of the LED load 2. Specifically, one end of capacitor C4 is connected to the positive terminal of LED1 at the beginning of the LED load 2, and the other end is connected to the negative terminal of LED1 at the end of the LED load 2. Therefore, by setting capacitor C4, it is possible to filter, stabilize the current, and suppress voltage fluctuations, while also improving the starting characteristics and anti-interference ability of the LED.

[0027] In this embodiment, the constant current drive circuit 3 includes at least one transistor Q4 and the same number of current-limiting resistor units as the transistor Q4. The collector of each transistor Q4 is connected to the negative terminal of the light-emitting diode LED1 at the tail end of the corresponding LED load 2, and the base of each transistor Q4 is connected to the collector of transistor Q8. The common terminal of the collector of transistor Q8 and the base of each transistor Q4 is connected to the negative terminal of the three-terminal adjustable shunt regulator D1. The common terminal of the collector of transistor Q8, the negative terminal of the three-terminal adjustable shunt regulator D1, and the base of each transistor Q4 is connected in series with a resistor R4 and then connected to the voltage input terminal 1. That is, the common terminal of the collector of transistor Q8 and the base of each transistor Q4 is connected to the common terminal of the negative terminal of the three-terminal adjustable shunt regulator D1 and the resistor R4. The emitters of each transistor Q4 are connected to one end of the corresponding current-limiting resistor unit, and the other end of each current-limiting resistor unit is grounded. The reference voltage terminal of the three-terminal adjustable shunt regulator D1 is connected in series with a resistor R11 and then to the emitter of one of the transistors Q4. The function of the resistor R11 is for adjustment, and the value of the resistor R11 is determined according to the adjustment requirements. The reference voltage terminal of the three-terminal adjustable shunt regulator D1 is also connected in series with a capacitor C15 and then grounded. The positive terminal of the three-terminal adjustable shunt regulator D1 is grounded.

[0028] For each constant current drive circuit 3, the number of transistors Q4 is determined by the current I of the LED load 2. led The magnitude determines the current I. led The larger the value, the more transistors Q4 there are.

[0029] Furthermore, each current-limiting resistor unit consists of at least one resistor R22. The emitter of each transistor Q4 is connected to one end of the corresponding resistor R22 in the current-limiting resistor unit, and the other end of each resistor R22 is grounded. For the current-limiting resistor unit, the number of resistors R22 connected in parallel is determined by the constant current I of the LED load 2. led The magnitude determines the constant current I. led The larger the value, the more resistors R22 there are. It should be noted that only the emitter of transistor Q4 and the common terminal of each resistor R22 in the corresponding current-limiting resistor unit are connected in series with resistor R11 and then connected to the reference voltage terminal of the three-terminal adjustable shunt regulator D1.

[0030] The temperature compensation circuit 4 includes an NTC thermistor R9, a transistor Q8, and a resistor R16. One end of the NTC thermistor R9 is connected to the common terminal of the base of transistor Q8 via a resistor R10, and then connected to voltage input terminal 1. The other end of the NTC thermistor R9 is grounded. The emitter of transistor Q8 is connected to the ground via a resistor R16, and the collector of transistor Q8 is connected to the base of all transistors Q4. Specifically, the common terminal of the collector of transistor Q8 and the negative terminal of the three-terminal adjustable shunt regulator D1 is connected to voltage input terminal 1 via a resistor R4. The base of each transistor Q4 is connected to the negative terminal of the three-terminal adjustable shunt regulator D1 and the common terminal of the collector of transistor Q8 and resistor R4.

[0031] Therefore, the temperature compensation circuit 4 consists of a drive resistor R10, an NTC thermistor R9, a transistor Q8, and a resistor R16 that controls the degree of current attenuation. Furthermore, the NTC thermistor R9 is located near the heat source of the low-temperature drift multi-channel LED constant current drive circuit, which is composed of all the transistors.

[0032] When the circuit board temperature is low, the NTC thermistor R9 has a large resistance, the base-emitter junction of transistor Q8 is open, and the base current of each transistor Q4 will decrease to varying degrees depending on the resistance of resistor R16. The larger the resistance R16, the larger the base current of transistor Q4, and the greater the current I of LED load 2. led The larger the value, the smaller the resistor R16, the smaller the base current of transistor Q4, and the smaller the current I of LED load 2. led The smaller the value, the lower the voltage drop across the NTC thermistor R9. As the temperature rises, the voltage drop across the base-beam (BE) junction of transistor Q8 becomes less than the turn-on voltage of Q8, causing Q8 to turn off. At this time, the current I of LED load 2... led Obtain the set maximum current value and keep it stable.

[0033] The collectors of each transistor Q4 are connected to the negative terminal of the corresponding LED load 2. The emitter of one transistor Q4 is connected to one end of the corresponding current-limiting resistor unit and the reference voltage terminal of the three-terminal adjustable shunt regulator D1. The bases of each transistor Q4 are connected to the common terminal of the driving resistor R4 and the negative terminal of the three-terminal adjustable shunt regulator D1. The positive terminal of the three-terminal adjustable shunt regulator D1 is grounded. Therefore, the constant current I of the LED load 2... led =V REF / R 限流 , where V REF R represents the reference voltage at the reference voltage terminal of the three-terminal adjustable shunt regulator D1. 限流 This indicates the total resistance value of the current-limiting resistor unit. The constant current accuracy is limited by the selection of the current-limiting resistor.

[0034] Therefore, by applying the above constant current circuit, the reference voltage of the reference voltage terminal of the three-terminal adjustable shunt regulator D1 is either 1.25V or 2.5V, and the accuracy is extremely high. It is not affected by the input voltage and temperature. Therefore, with this design, a constant current output can still be obtained when the voltage and temperature change.

[0035] Please see Figure 3 The low-temperature drift multi-channel LED constant current drive circuit with temperature compensation function also includes a one-to-all-out circuit. The LED load 2 is provided with two sets. The one-to-all-out circuit is provided with a common cathode fast recovery diode Q12, MOSFET Q2, MOSFET Q3, resistor R5, resistor R6, resistor R7, resistor R8 and capacitor C7.

[0036] The common cathode of the common cathode fast recovery diode Q12 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to the negative terminal of the three-terminal adjustable shunt regulator D1. The collector of transistor Q8 is connected to the common terminal of the bases of all transistors Q4. This collector is also connected in series with capacitor C7 and then grounded. The emitter of transistor Q7 is grounded. The two anodes of the common cathode fast recovery diode Q12 are connected to the drains of MOSFETs Q2 and Q3, respectively. One anode of the common cathode fast recovery diode Q12 connected to the drain of MOSFET Q2 is also... A series resistor R6 is connected to voltage input terminal 1. The common-cathode fast recovery diode Q12 is connected to one anode of the drain of MOSFET Q3, and another series resistor R5 is connected to voltage input terminal 1. The gate of MOSFET Q2 is connected to the common terminal of the negative terminal of one LED load 2 and the collector of the corresponding transistor Q4, after a series resistor R8. The gate of MOSFET Q3 is connected to the common terminal of the negative terminal of the other LED load 2 and the collector of the corresponding transistor Q4, after a series resistor R7. The sources of both MOSFETs Q2 and Q3 are grounded. The common-cathode fast recovery diode Q12 is used as an OR gate.

[0037] When both LED loads 2 are working normally, the voltages of TP7 and TP10 are approximately equal, the source of MOSFET Q3 is grounded, and when the gate voltage is high, the VGS of MOSFET Q3 is greater than or equal to 0, MOSFET Q3 is turned on, and the current flowing through resistor R5 is all conducted to ground through the N-body diode of MOSFET Q3. The common cathode fast recovery diode Q12 is not working at all, and the circuit is operating normally.

[0038] When LED1 in one of the LED loads 2 corresponding to MOSFET Q3 is open-circuited, the voltage of TP7 will drop to near 0V, and the voltage of TP10, which is approximately the same as the voltage of TP7, will also drop to 0V. MOSFET Q3 will then be turned off, and the current will no longer flow through MOSFET Q3 but will instead flow to the common cathode fast recovery diode Q12. With the common cathode fast recovery diode Q12 conducting, the base of transistor Q7 will be at a high level, and transistor Q7 will be turned on. The base current of transistor Q4 and all parallel driving transistors will then flow to ground through transistor Q7, causing all transistors Q4 in both LED loads 2 to malfunction.

[0039] The same principle applies to the Q2 side of the MOSFET. If even one LED1 on the circuit board is open, all LED1s in the entire circuit will be turned off. This achieves the function of turning off all LEDs if one is open.

[0040] Finally, it should be noted that the above description is merely a preferred embodiment of the present utility model. Those skilled in the art, under the guidance of the present utility model, can make various similar representations without departing from the spirit and claims of the present utility model, and such modifications all fall within the protection scope of the present utility model.

Claims

1. A multi-channel LED constant current driving circuit with temperature compensation function and low temperature drift, comprising at least one LED constant current driving circuit, each LED constant current driving circuit being provided with an LED load (2) whose positive terminal is connected to the voltage input terminal (1) and a constant current driving circuit (3) connected to the negative terminal of the LED load (2), each constant current driving circuit (3) being connected to the voltage input terminal (1), characterized in that, It also includes a temperature compensation circuit (4), which is equipped with an NTC thermistor R9. One end of the NTC thermistor R9 is grounded, and the other end is connected to the voltage input terminal (1) after being connected in series with a resistor R10. The common terminal of the NTC thermistor R9 and the resistor R10 is connected to the base of the transistor Q8. The collector of the transistor Q8 is connected to each constant current drive circuit (3). The emitter of the transistor Q8 is connected to the ground after being connected in series with a resistor R16.

2. The low temperature drift multi-channel LED constant current driving circuit with temperature compensation function according to claim 1, characterized in that, It also includes a three-terminal adjustable shunt regulator D1 with the positive terminal grounded. The negative terminal of the three-terminal adjustable shunt regulator D1 is connected to the voltage input terminal (1) after the series resistor R4. Each constant current drive circuit (3) is equipped with at least one transistor Q4 whose collector is simultaneously connected to the negative terminal of the corresponding LED load (2). The base of each transistor Q4 is connected to the collector of transistor Q8. The common terminal of the collector of transistor Q8 and the base of each transistor Q4 is connected to the common terminal of the negative terminal of the three-terminal adjustable shunt regulator D1 and the resistor R4. The emitter of each transistor Q4 is connected to one end of the corresponding current limiting resistor unit. The other end of each current limiting resistor unit is grounded. The reference voltage terminal of the three-terminal adjustable shunt regulator D1 is connected in series with resistor R11 and then connected to the common terminal of the emitter of one of the transistors Q4 and the corresponding current limiting resistor unit. The reference voltage terminal is also connected in series with capacitor C15 and then grounded.

3. The low temperature drift multi-channel LED constant current driving circuit with temperature compensation function according to claim 2, characterized in that, Each current-limiting resistor unit consists of at least one resistor R22. The emitter of each transistor Q4 is connected to one end of each resistor R22 in the corresponding current-limiting resistor unit, and the other end of each resistor R22 is grounded.

4. The low temperature drift multi-channel LED constant current driving circuit with temperature compensation function according to claim 2, characterized in that, Both ends of the LED load (2) are connected in parallel with capacitor C4.

5. The low temperature drift multi-channel LED constant current driving circuit with temperature compensation function according to claim 2 or 4, characterized in that, The LED load (2) consists of at least one LED1 with positive and negative terminals connected in series. The positive terminal of the LED1 at the beginning is connected to the voltage input terminal (1), and the negative terminal of the LED1 at the end is connected to the collector of each transistor Q4 in the corresponding constant current drive circuit (3).

6. The low temperature drift multi-channel LED constant current driving circuit with temperature compensation function according to claim 2, characterized in that, It also includes a one-to-all-out circuit. The LED load (2) has two sets. The one-to-all-out circuit is equipped with a common cathode fast recovery diode Q12, a MOSFET Q2 and a MOSFET Q3. The common cathode of the common cathode fast recovery diode Q12 is connected to the base of transistor Q7. The collector of transistor Q7 is connected to the negative terminal of the three-terminal adjustable shunt regulator D1. The collector of transistor Q8 is connected to the common terminal of the base of each transistor Q4. The collector is also connected in series with capacitor C7 and then grounded. The emitter of transistor Q7 is grounded. The common cathode fast recovery diode Q12 is connected to the common cathode fast recovery diode Q3. The two anodes of 2 are connected to the drain of MOSFET Q2 and the drain of MOSFET Q3 respectively. The two anodes are also connected to the voltage input terminal (1) after being connected in series with resistors R6 and R5 respectively. The gate of MOSFET Q2 is connected in series with resistor R8 and then connected to the common terminal of the negative terminal of one of the LED loads (2) and the collector of the corresponding transistor Q4. The gate of MOSFET Q3 is connected in series with resistor R7 and then connected to the common terminal of the negative terminal of the other LED load (2) and the collector of the corresponding transistor Q4. The source of MOSFET Q2 and the source of MOSFET Q3 are both grounded.

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