LED light source driving circuit and resistance value calculation method

Abstract

The application discloses an LED light source driving circuit and a resistance value calculation method, and relates to the field of LED light source driving.The LED light source driving circuit drives an LED module by outputting currents to a first output line and a second output line through a linear constant current chip, and limits the total output current of the linear constant current chip by setting a total current setting resistor.Meanwhile, the sum of the currents of the first output line and the second output line is equal to the total output current.Based on this, since the voltage of the power supply pin is equal to the voltage of the shunt pin, the current flowing from the power supply pin to the shunt pin of the power supply module has no power, so that the power of the linear constant current chip is reduced on the basis of keeping the sum of the currents of the first output line and the second output line unchanged and always equal to the total output current, and the heat accumulation of the linear constant current chip is reduced.

Description

Technical Field

[0001] This invention relates to the field of LED light source driving, and in particular to an LED light source driving circuit and a method for calculating resistance values. Background Technology

[0002] Fog lights are used to make your vehicle visible to other vehicles in foggy or rainy weather when visibility is significantly reduced. Rear fog lights are essential for vehicles. Previously, halogen bulbs were commonly used for rear fog lights. These bulbs not only had a slow response time, leading to reduced safety, but also generated a lot of heat, had low brightness, were not energy-efficient, and significantly shortened the lifespan of the rear fog lights. LEDs, on the other hand, have significant advantages such as fast response time, low power consumption, energy saving, and long lifespan, and have been widely used in automotive lighting. LED driver technology has also developed alongside the advancement of LED application technology.

[0003] In the current automotive industry, rear fog lights are trending towards miniaturization, and regulations impose high requirements on the upper and lower limits of luminous flux. To meet these requirements, rear fog lights typically use three 1W high-power LEDs. Currently, the main driving methods for LED rear fog lights are the DC-DC converter and the linear constant current converter. The DC-DC converter (which requires a DC-DC driver chip and energy storage inductor, resulting in a large size and high cost) is highly efficient, generating minimal heat when driving three 1W LEDs. However, its complex circuit structure, large size, and high cost make it less effective. The linear constant current converter, while simpler, smaller, and less expensive than the DC-DC converter, is less efficient. When driving three 1W LEDs, the linear constant current driver chip generates significant heat, requiring a large heatsink area to dissipate heat; otherwise, the chip risks premature overheating and triggering its protection mechanism. Summary of the Invention

[0004] To reduce driving costs and minimize heat buildup in linear constant current driver chips, this invention proposes an LED light source driving circuit, comprising:

[0005] The system comprises a total current setting resistor, a power supply module, and a linear constant current chip, a shunt module, and an LED module connected in sequence. The power supply module is connected to the power supply pin of the linear constant current chip. The shunt module includes a first output line and a second output line connected to the linear constant current chip, and a shunt resistor is provided on the first output line. The voltage of the power supply pin is equal to the voltage of the shunt pin. The shunt pin is a connection pin on the linear constant current chip that is connected to the first output line.

[0006] The total current setting resistor is connected to the linear constant current chip and is used to limit the total output current of the linear constant current chip; the linear constant current chip is used to output current to the first output line and the second output line to drive the LED module; the sum of the currents through the first output line and the second output line is equal to the total output current.

[0007] Furthermore, in the LED light source driving circuit: the power supply module is connected to the power supply pin (eighth pin) of the linear constant current chip; the seventh pin of the linear constant current chip is connected to one end of the total current setting resistor, and the other end of the total current setting resistor is connected to the first pin of the linear constant current chip and then connected to the connection line between the power supply module and the eighth pin; the sixth pin of the linear constant current chip is connected to one end of the shunt resistor on the first output line through the second output line and then connected to one end of the LED module; the shunt pin (fifth pin) of the linear constant current chip is connected to the other end of the shunt resistor; and the other end of the LED module is grounded.

[0008] Furthermore, the resistance value of the shunt resistor is less than a preset resistance value; the formula for calculating the preset resistance value is:

[0009] R1 max = (VIN - VLED) * R2 阻值 / (V 基准 -R2 阻值 *IOUT max );

[0010] In the formula, IOUT max =PIC max / (VIN-VLED), IOUT max This indicates the maximum current flowing through the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop across the LED module, and R2... 阻值 The resistance value of the resistor indicating the total current setting is expressed in V. 基准 This represents the reference voltage of the linear constant current chip, PIC. max R1 represents the maximum power value of the linear constant current chip. max This indicates the preset resistance value.

[0011] Furthermore, the resistance value of the shunt resistor is positively correlated with the operating power of the linear constant current chip.

[0012] Furthermore, the formula for setting the resistance value of the total current setting resistor is as follows:

[0013] R2 阻值 =V 基准 / ILED;

[0014] In the formula, V 基准R2 represents the reference voltage of the linear constant current chip, ILED represents the drive current of the LED module, i.e., the total output current, and R2 represents the reference voltage of the linear constant current chip. 阻值 This indicates the resistance value of the resistor set for the total current.

[0015] Furthermore, the formula for calculating the maximum power value of the linear constant current chip is as follows:

[0016] PIC max =(T max -T em ) / TR;

[0017] In the formula, T max T represents the maximum junction temperature of the linear constant current chip. em The linear constant current chip can withstand a maximum operating ambient temperature; TR represents the thermal resistance of the linear constant current chip to the environment; PIC represents the maximum operating ambient temperature. max This indicates the maximum power value.

[0018] Furthermore, the LED module includes multiple LEDs connected in series.

[0019] This invention also proposes a method for calculating the resistance value of an LED light source driving circuit. The LED light source driving circuit includes: a total current setting resistor, a power supply module, and a linear constant current chip, a shunt module, and an LED module connected in sequence. The power supply module is connected to the power supply pin of the linear constant current chip. The shunt module includes a first output line and a second output line connected to the linear constant current chip, and a shunt resistor is provided on the first output line. The voltage of the power supply pin is equal to the voltage of the shunt pin. The shunt pin is a connection pin on the linear constant current chip connected to the first output line. Wherein:

[0020] The total current setting resistor is connected to the linear constant current chip and is used to limit the total output current of the linear constant current chip; the linear constant current chip is used to output current to the first output line and the second output line to drive the LED module; the sum of the currents through the first output line and the second output line equals the total output current; the resistance value calculation method includes:

[0021] The value of the total current setting resistor is set according to the driving current of the LED module, i.e., the total output current.

[0022] The resistance value of the set resistor is set according to the total current and the maximum power value of the linear constant current chip. The resistance value of the shunt resistor is then determined based on the preset resistance value.

[0023] Furthermore, in the LED light source driving circuit:

[0024] The power module is connected to the power supply pin (eighth pin) of the linear constant current chip; the seventh pin of the linear constant current chip is connected to one end of the total current setting resistor, and the other end of the total current setting resistor is connected to the first pin of the linear constant current chip and then connected to the connection line between the power module and the eighth pin; the sixth pin of the linear constant current chip is connected to one end of the shunt resistor on the first output line through the second output line and then connected to one end of the LED module; the shunt pin (fifth pin) of the linear constant current chip is connected to the other end of the shunt resistor; the other end of the LED module is grounded.

[0025] Furthermore, the resistance value of the shunt resistor is less than the preset resistance value;

[0026] The formula for setting the total current setting resistor value is:

[0027] R2 阻值 =V 基准 / ILED;

[0028] In the formula, V 基准 R2 represents the reference voltage of the linear constant current chip, ILED represents the drive current of the LED module, i.e., the total output current, and R2 represents the reference voltage of the linear constant current chip. 阻值 This indicates the resistance value of the resistor that sets the total current.

[0029] The formula for setting the preset resistance value is:

[0030] R1 max = (VIN - VLED) * R2 阻值 / (V 基准 -R2 阻值 *IOUT max );

[0031] In the formula, IOUT max =PIC max / (VIN-VLED), IOUT max This indicates the maximum current flowing through the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop across the LED module, and R2... 阻值 The resistance value of the resistor indicating the total current setting is expressed in V. 基准 This represents the reference voltage of the linear constant current chip, PIC. max R1 represents the maximum power value of the linear constant current chip. max This indicates the preset resistance value.

[0032] Compared with the prior art, the present invention has at least the following beneficial effects:

[0033] (1) In the LED light source driving circuit of the present invention, the linear constant current chip drives the LED module by outputting current to the first output line and the second output line. The total output current of the linear constant current chip is limited by setting the total current setting resistor. At the same time, the sum of the currents through the first output line and the second output line is equal to the total output current. Based on this, since the voltage of the power supply pin is equal to the voltage of the shunt pin, the part of the current of the power module flowing from the power supply pin to the shunt pin has basically no power. Therefore, the power of the linear constant current chip is reduced while keeping the sum of the currents through the first output line and the second output line constant and always equal to the total output current, thereby reducing the heat accumulation of the linear constant current chip.

[0034] (2) In this invention, the resistance value of the shunt resistor is less than the preset resistance value. Since the preset resistance value is the maximum resistance value of the shunt resistor calculated based on the maximum power value, maximum junction temperature, maximum operating ambient temperature and thermal resistance to the environment of the linear constant current chip, it means that by ensuring that the resistance value of the shunt resistor is less than the preset resistance value, the operating power of the linear constant current chip can be avoided from being above the maximum power value, thereby ensuring that the chip junction temperature does not exceed the maximum junction temperature. This achieves the goal of driving the LED module with high efficiency while avoiding the risk of premature overheating protection of the chip and improving the service life of the chip.

[0035] (3) This invention realizes the current distribution of the linear constant current chip by setting a shunt resistor (part of the current flows into PIN5 and part of the current flows into PIN6), which reduces the operating power of the linear constant current chip. Therefore, there is no need for large-area heat dissipation, and the circuit structure is simple, small in size and low in cost. Attached Figure Description

[0036] Figure 1 This is a circuit diagram for driving an LED light source. Detailed Implementation

[0037] The following are specific embodiments of the present invention, which are described in conjunction with the accompanying drawings. However, the present invention is not limited to these embodiments.

[0038] Example 1

[0039] To reduce driving costs, decrease circuit size, and minimize heat buildup in linear constant current chips, such as... Figure 1 As shown, the present invention proposes an LED light source driving circuit, comprising:

[0040] The system includes a total current setting resistor R2, a power supply module, and a linear constant current chip, a shunt module, and an LED module connected in sequence. The power supply module is connected to the power supply pin PIN8 of the linear constant current chip. The shunt module includes a first output line and a second output line connected to the linear constant current chip, with a shunt resistor R1 on the first output line. The voltage of the power supply pin PIN8 is equal to the voltage of the shunt pin PIN5. The shunt pin is the connection pin PIN5 on the linear constant current chip, which is connected to the first output line. The power supply module is specifically a car battery.

[0041] The total current setting resistor R2 is connected to the linear constant current chip and is used to limit the total output current of the linear constant current chip; the linear constant current chip is used to output current to the first output line and the second output line to drive the LED module; the sum of the currents through the first output line and the second output line is equal to the total output current.

[0042] In the LED light source driving circuit: the power supply module is connected to the power supply pin PIN8 (eighth pin) of the linear constant current chip; the seventh pin PIN7 of the linear constant current chip is connected to one end of the total current setting resistor R2, and the other end of the total current setting resistor R2 is connected to the first pin PIN1 of the linear constant current chip and then connected to the connection line between the power supply module and the eighth pin PIN8; the sixth pin PIN6 of the linear constant current chip is connected to one end of the shunt resistor R1 on the first output line through the second output line and then connected to one end of the LED module; the shunt pin PIN5 (fifth pin) of the linear constant current chip is connected to the other end of the shunt resistor R1; the other end of the LED module is grounded.

[0043] The LED module includes multiple LEDs connected in series. Specifically, in this embodiment, the LED module includes three LEDs connected in series.

[0044] The resistance value of the shunt resistor is less than the preset resistance value; the formula for calculating the preset resistance value is:

[0045] R1 max = (VIN - VLED) * R2 阻值 / (V 基准 -R2 阻值 *IOUT max );

[0046] In the formula, IOUT max =PIC max / (VIN-VLED), IOUT max This indicates the maximum current flowing through the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop across the LED module, and R2... 阻值The resistance value of the resistor indicating the total current setting is expressed in V. 基准 This represents the reference voltage of the linear constant current chip, PIC. max R1 represents the maximum power value of the linear constant current chip. max This indicates the preset resistance value.

[0047] In this invention, the resistance value of the shunt resistor is less than a preset resistance value. Since the preset resistance value is the maximum resistance value corresponding to the shunt resistor calculated based on the maximum power value, maximum junction temperature, maximum operating ambient temperature of the linear constant current chip, and thermal resistance to the environment, it means that by ensuring that the resistance value of the shunt resistor is less than the preset resistance value, the operating power of the linear constant current chip can be prevented from exceeding the maximum power value, thereby ensuring that the chip junction temperature does not exceed the maximum junction temperature. This achieves high-efficiency driving of the LED module while avoiding the risk of premature overheating protection of the chip and improving the chip's service life.

[0048] In this embodiment, the V 基准 =0.099V.

[0049] The formula for setting the resistance value of the total current setting resistor is:

[0050] R2 阻值 =V 基准 / ILED;

[0051] In the formula, V 基准 R2 represents the reference voltage of the linear constant current chip, ILED represents the drive current of the LED module, i.e., the total output current, and R2 represents the reference voltage of the linear constant current chip. 阻值 This indicates the resistance value of the resistor set for the total current.

[0052] The formula for calculating the maximum power value of the linear constant current chip is as follows:

[0053] PIC max =(T max -T em ) / TR;

[0054] In the formula, T max T represents the maximum junction temperature of the linear constant current chip. em The linear constant current chip can withstand a maximum operating ambient temperature; TR represents the thermal resistance of the linear constant current chip to the environment; PIC represents the maximum operating ambient temperature. max This indicates the maximum power value. In this embodiment, the maximum junction temperature is 150°C, the chip's thermal resistance to the environment is 58.1°C / W, the maximum operating ambient temperature is 70°C, and the maximum power of the PIC is... max = (150-70) / 58.1 = 1.376W.

[0055] The linear constant current chip is model NSL21610.

[0056] In the LED light source driving circuit of the present invention, the linear constant current chip drives the LED module by outputting current to the first output line and the second output line. The total output current of the linear constant current chip is limited by setting a total current setting resistor. At the same time, the sum of the currents through the first output line and the second output line is equal to the total output current. Based on this, since the voltage of the power supply pin is equal to the voltage of the shunt pin, the current of the power module flowing from the power supply pin to the shunt pin has basically no power. Therefore, while keeping the sum of the currents through the first output line and the second output line constant and always equal to the total output current, the power of the linear constant current chip is reduced, thereby reducing the heat accumulation of the linear constant current chip.

[0057] The resistance value of the shunt resistor is positively correlated with the operating power of the linear constant current chip.

[0058] In this invention, the resistance value of the shunt resistor is positively correlated with the operating power of the linear constant current chip. That is, the more current flows through the shunt resistor, the lower the operating power of the linear constant current chip. Therefore, this invention limits the shunt resistor value to less than a preset value to keep the operating power of the linear constant current chip below its maximum power value. Theoretically, under the condition of being less than the preset resistance value, selecting a resistor with the smallest possible resistance as the shunt resistor allows the linear constant current chip to adjust the output current as much as possible to the first output line (the current that causes the chip to heat up mainly comes from the second output line, therefore adjusting the output current to the first output line as much as possible). The shunt resistor is used until it reaches current saturation, which can minimize the operating power of the linear constant current chip. However, since the lower the operating power of the linear constant current chip, the greater the power on the shunt resistor, the larger the package will be. Based on this, this embodiment sets the range of shunt resistor values ​​by setting a lower limit value: (lower limit value, preset resistance value). In other words, a resistor with a resistance value within this range is selected as the shunt resistor. This ensures that the circuit size is small and that the operating power of the linear constant current chip is less than the maximum power value, thereby reducing the heat accumulation of the linear constant current chip on the basis of a small-volume circuit.

[0059] Example 2

[0060] This invention also proposes a method for calculating the resistance value of an LED light source driving circuit, such as... Figure 1As shown, the LED light source driving circuit includes: a total current setting resistor R2, a power supply module, and a linear constant current chip, a shunt module, and an LED module connected in sequence; the power supply module is connected to the power supply pin PIN8 of the linear constant current chip; the shunt module includes a first output line and a second output line connected to the linear constant current chip, and a shunt resistor R1 is provided on the first output line; the voltage of the power supply pin PIN8 is equal to the voltage of the shunt pin PIN5; the shunt pin is the connection pin PIN5 on the linear constant current chip connected to the first output line; wherein:

[0061] The total current setting resistor R2 is connected to the linear constant current chip and is used to limit the total output current of the linear constant current chip; the linear constant current chip is used to output current to the first output line and the second output line to drive the LED module; the sum of the currents through the first output line and the second output line equals the total output current; the method for calculating the resistance value includes:

[0062] The value of the total current setting resistor is set according to the driving current of the LED module, i.e., the total output current.

[0063] The resistance value of the set resistor is set according to the total current and the maximum power value of the linear constant current chip. The resistance value of the shunt resistor is then determined based on the preset resistance value.

[0064] In the LED light source driving circuit:

[0065] The power module is connected to the power supply pin (pin 8) of the linear constant current chip; the seventh pin (pin 7) of the linear constant current chip is connected to one end of the total current setting resistor R2, and the other end of the total current setting resistor R2 is connected to the first pin (pin 1) of the linear constant current chip and then connected to the connection line between the power module and the eighth pin (pin 8); the sixth pin (pin 6) of the linear constant current chip is connected to one end of the shunt resistor R1 on the first output line through the second output line and then connected to one end of the LED module; the shunt pin (pin 5) of the linear constant current chip is connected to the other end of the shunt resistor R1; the other end of the LED module is grounded.

[0066] The resistance value of the shunt resistor is less than the preset resistance value;

[0067] The formula for setting the total current setting resistor value is:

[0068] R2 阻值 =V 基准 / ILED;

[0069] In the formula, V 基准 R2 represents the reference voltage of the linear constant current chip, ILED represents the drive current of the LED module, i.e., the total output current, and R2 represents the reference voltage of the linear constant current chip.阻值 This indicates the resistance value of the resistor that sets the total current.

[0070] The formula for setting the preset resistance value is:

[0071] R1 max = (VIN - VLED) * R2 阻值 / (V 基准 -R2 阻值 *IOUT max );

[0072] In the formula, IOUT max =PIC max / (VIN-VLED), IOUT max This indicates the maximum current flowing through the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop across the LED module, and R2... 阻值 The resistance value of the resistor indicating the total current setting is expressed in V. 基准 This represents the reference voltage of the linear constant current chip, PIC. max R1 represents the maximum power value of the linear constant current chip. max This indicates the preset resistance value.

[0073] It should be noted that all directional indications (such as up, down, left, right, front, back, etc.) in the embodiments of the present invention are only used to explain the relative positional relationship and movement of each component in a certain specific posture (as shown in the figure). If the specific posture changes, the directional indication will also change accordingly.

[0074] Furthermore, in this invention, descriptions involving terms such as "first," "second," and "a" are for descriptive purposes only and should not be construed as indicating or implying their relative importance or implicitly specifying the number of technical features indicated. Thus, a feature defined as "first" or "second" may explicitly or implicitly include at least one of that feature. In the description of this invention, "a plurality of" means at least two, such as two, three, etc., unless otherwise explicitly specified.

[0075] In this invention, unless otherwise explicitly specified and limited, the terms "connection," "fixed," etc., should be interpreted broadly. For example, "fixed" can mean a fixed connection, a detachable connection, or an integral part; it can mean a mechanical connection or an electrical connection; it can mean a direct connection or an indirect connection through an intermediate medium; it can mean the internal communication of two components or the interaction between two components, unless otherwise explicitly limited. Those skilled in the art can understand the specific meaning of the above terms in this invention according to the specific circumstances.

[0076] Furthermore, the technical solutions of the various embodiments of the present invention can be combined with each other, but only if they are feasible for those skilled in the art. If the combination of technical solutions is contradictory or cannot be implemented, it should be considered that such combination of technical solutions does not exist and is not within the scope of protection claimed by the present invention.

Claims

1. An LED light source driving circuit, characterized by, The application relates to an LED light source driving circuit. The power supply module is connected with a power supply pin of the linear constant current chip; the shunt module comprises a first output line and a second output line connected with the linear constant current chip, and a shunt resistor is arranged on the first output line; the voltage of the power supply pin is equal to the voltage of a shunt pin; the shunt pin is a connecting pin of the linear constant current chip connected with the first output line; wherein: The total current setting resistor is connected with the linear constant current chip and is used for limiting the output total current of the linear constant current chip; the linear constant current chip is used for outputting currents to the first output line and the second output line to drive the LED module; the sum of the currents of the first output line and the second output line is equal to the output total current; In the LED light source driving circuit, the power supply module is connected with the eighth pin of the linear constant current chip; one end of the seventh pin of the linear constant current chip is connected with one end of the total current setting resistor, and the other end of the total current setting resistor is connected with the first pin of the linear constant current chip and then connected to the connecting line between the power supply module and the eighth pin; one end of the sixth pin of the linear constant current chip is connected with one end of the shunt resistor on the first output line through the second output line and then connected to one end of the LED module; the fifth pin of the linear constant current chip is connected with the other end of the shunt resistor; the other end of the LED module is grounded; The resistance value of the shunt resistor is less than a preset resistance value; the calculation formula of the preset resistance value is: The resistance value of the shunt resistor is positively correlated with the running power of the linear constant current chip. R1 max = (VIN-VLED) * R2 resistance / (Vref - R2 resistance * IOUT max ); In the formula, IOUT max = PIC max / (VIN-VLED), IOUT max represents the maximum passing current corresponding to the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop of the LED module, R2 阻值 represents the resistance value of the total current setting resistor, V 基准 represents the reference voltage of the linear constant current chip, PIC max represents the maximum power value of the linear constant current chip, R1 max represents the preset resistance value.

2. The LED light source driving circuit according to claim 1, wherein The setting formula of the resistance value of the total current setting resistor is:

3. The LED light source driving circuit according to claim 2, wherein The calculation formula of the maximum power value of the linear constant current chip is: R2 阻值 = V 基准 / ILED; In the formula, V 基准 represents the reference voltage of the linear constant current chip, ILED represents the driving current of the LED module, i.e. the output total current, R2 阻值 represents the resistance value of the total current setting resistor.

4. The LED light source driving circuit according to claim 3, wherein The LED module comprises a plurality of serially connected LED lamps. PIC max = (T max -T em ) / TR; where T max represents the maximum junction temperature of the linear constant current chip, T em represents the maximum operating ambient temperature that the linear constant current chip can tolerate, TR represents the thermal resistance of the linear constant current chip to the environment, PIC max represents the maximum power value.

5. The LED light source driving circuit according to claim 1, wherein The LED light source driving circuit comprises a total current setting resistor, a power supply module and sequentially connected linear constant current chips, a shunt module and an LED module; the power supply module is connected with a power supply pin of the linear constant current chip; the shunt module comprises a first output line and a second output line connected with the linear constant current chip, and a shunt resistor is arranged on the first output line; the voltage of the power supply pin is equal to the voltage of a shunt pin; the shunt pin is a connecting pin of the linear constant current chip connected with the first output line; wherein:

6. A resistance value calculation method for an LED light source driving circuit, characterized by, The total current setting resistor is connected with the linear constant current chip and is used for limiting the output total current of the linear constant current chip; the linear constant current chip is used for outputting currents to the first output line and the second output line to drive the LED module; the sum of the currents of the first output line and the second output line is equal to the output total current; in the LED light source driving circuit: ​ The power module is connected with the eighth pin of the linear constant current chip; the seventh pin of the linear constant current chip is connected with one end of the total current setting resistor, and the other end of the total current setting resistor is connected with the first pin of the linear constant current chip and then connected to the connecting line between the power module and the eighth pin; the sixth pin of the linear constant current chip is connected with one end of the shunt resistor through the second output line and the first output line, and then connected to one end of the LED module; the fifth pin of the linear constant current chip is connected with the other end of the shunt resistor; the other end of the LED module is grounded; The resistance value calculation method comprises: The resistance value of the total current setting resistor is set according to the driving current of the LED module, i.e. the output total current; The preset resistance value is set according to the resistance value of the total current setting resistor and the maximum power value of the linear constant current chip, and the resistance value of the shunt resistor is determined based on the preset resistance value; The resistance value of the shunt resistor is less than the preset resistance value; The setting formula of the preset resistance value is: R1 max = (VIN-VLED) * R2 resistance / (Vref - R2 resistance IOUT max ); In the formula, IOUT max = PIC max / (VIN-VLED), IOUT max represents the maximum passing current corresponding to the second output line, VIN represents the voltage of the power module, VLED represents the voltage drop of the LED module, R2 阻值 represents the resistance value of the total current setting resistor, V 基准 represents the reference voltage of the linear constant current chip, PIC max represents the maximum power value of the linear constant current chip, R1 max represents the preset resistance value.

7. The resistance value calculation method for the LED light source driving circuit according to claim 6, characterized in that, The setting formula of the total current setting resistor resistance value is: R2 阻值 = V 基准 / ILED; In the formula, V 基准 represents the reference voltage of the linear constant current chip, ILED represents the driving current of the LED module, i.e. the output total current, R2 阻值 represents the resistance value of the total current setting resistor.

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