Multi-channel constant current chip low-brightness consistency automatic compensation circuit, device and control method

Abstract

The application provides a multi-channel constant current chip low-brightness consistency automatic compensation circuit, device and control method, the circuit comprises a main control module, a constant current module, a current regulating module, a voltage detection circuit, the constant current chip module comprises a constant current chip, the current regulating module comprises a dummy load control circuit and a dummy load; the main control module is connected with the dimming end of the constant current chip, the control end of the dummy load control circuit and the voltage detection circuit respectively, the current regulating module is connected with the output end of the constant current module, the output end of the constant current module is connected with an external LED chip, the controlled end of the dummy load control circuit is connected with the dummy load and the output end of the constant current module, the dummy load is connected with the output end of the constant current module, and the voltage detection circuit is connected with the external LED chip; the resistance value of the dummy load is controlled through a PWM signal, so that the current flowing through the external LED chip is controlled, the same LED chip is kept with the same brightness when being adjusted to the lowest brightness, and the influence of the difference of the constant current chip is avoided.

Description

Technical Field

[0001] This invention relates to the field of LED driver power supplies, specifically to a multi-channel constant current chip low brightness consistency automatic compensation circuit, device, and control method. Background Technology

[0002] Multi-channel constant current dimming technology has been widely used in the LED driver power supply field. For the same lamp, due to differences in constant current chips—for example, the threshold for adjusting to the lowest brightness may differ even among constant current chips of the same model—the current supplied to the LED chip may vary when the same constant current chip receives a PWM signal with the minimum duty cycle, resulting in different brightness levels for the lamp. When multiple identical lamps are used in a scenario, it cannot be guaranteed that the brightness will remain consistent when all lamps are adjusted to the lowest level, leading to a poor user experience. Summary of the Invention

[0003] The primary objective of this invention is to provide an automatic compensation circuit for low brightness consistency of multi-channel constant current chips, which can solve the problem of inconsistent brightness at the lowest brightness level for multiple identical lamps due to differences in constant current chips.

[0004] A second objective of this invention is to provide an apparatus including the aforementioned multi-channel constant current chip low brightness consistency automatic compensation circuit.

[0005] A third objective of this invention is to provide a control method for the aforementioned multi-channel constant current chip low-brightness consistency automatic compensation circuit.

[0006] To achieve the aforementioned first objective, this invention provides a multi-channel constant current chip low-brightness consistency automatic compensation circuit, comprising: a main control module, a constant current module, a current adjustment module, and a voltage detection circuit. The constant current chip module includes a constant current chip, and the current adjustment module includes a dummy load control circuit and a dummy load. The main control module is connected to the dimming terminal of the constant current chip, the control terminal of the dummy load control circuit, and the voltage detection circuit. The current adjustment module is connected to the output terminal of the constant current module, which is connected to the LED chip. The controlled terminal of the dummy load control circuit is connected to the dummy load and the output terminal of the constant current module, and the dummy load is connected to the output terminal of the constant current module. The voltage detection circuit is connected to the LED chip. The constant current module supplies power to the LED chip. The voltage detection circuit detects the current voltage value of the LED chip and transmits it to the main control module. The main control module determines a target PWM signal based on the current voltage value and the start-up voltage value. When the target PWM signal is input to the controlled terminal of the dummy load control circuit, the voltage across the LED chip is the start-up voltage value. The dummy load control circuit changes the resistance value of the dummy load according to the target PWM signal.

[0007] As can be seen from the above scheme, this invention outputs a PWM signal from the main control module to the controlled terminal of the dummy load control circuit to control the resistance value of the dummy load. This dummy load resistance then limits the current flowing through the LED chip, ensuring that the current flowing through the LED chip is the current corresponding to its minimum brightness. The voltage detection module can determine whether the current flowing through the LED chip at this time is the current required for the LED chip to reach its minimum brightness by detecting the current voltage value. For each lamp with the same LED chip, there is a specific target PWM signal. The main control module can output the target PWM signal to the controlled terminal of the dummy load control circuit, ensuring that the current of the LED chip in the lamp corresponding to the target PWM signal is the current corresponding to its minimum brightness. Since the LED chips are identical, their minimum brightness currents are also identical. Therefore, under the control of the target PWM signal, the current flowing through multiple LED chips is the same, resulting in the same brightness. This allows multiple identical lamps to maintain consistent brightness even when adjusted to the minimum brightness, despite differences in constant current chips.

[0008] A further approach is to connect a dummy load in parallel with the LED at the output of the constant current module.

[0009] Therefore, it can be seen that the current of the LED chip can be controlled by using a dummy load in parallel to shunt the current.

[0010] A further approach is to include an optocoupler in the dummy load control circuit, with the control terminal of the dummy load control circuit being the input terminal of the optocoupler and the controlled terminal of the dummy load control circuit being the output terminal of the optocoupler.

[0011] To achieve the second objective mentioned above, the present invention provides a multi-channel constant current chip low brightness consistency automatic compensation device, comprising a housing, wherein the housing includes the aforementioned multi-channel constant current chip low brightness consistency automatic compensation circuit.

[0012] To achieve the third objective mentioned above, the control method for the multi-channel constant current chip low brightness consistency automatic compensation circuit provided by the present invention includes the following steps:

[0013] Output a preset minimum PWM signal to the dimming terminal of the constant current chip; obtain the start-up voltage value and the current voltage value; output a gradual PWM signal to the controlled terminal of the dummy load control circuit, and keep the duty cycle of the gradual PWM signal unchanged when the obtained current voltage value is equal to the start-up voltage value.

[0014] As can be seen from the above scheme, the present invention changes the resistance value of the dummy load by adjusting the gradual PWM signal, thereby adjusting the current flowing through the LED chip by the dummy load. This ensures that the current of multiple identical LED chips remains consistent when the brightness is reduced to the lowest level. The current flowing through the LED chip at this time is determined by comparing the current voltage value detected in real time with the start-up voltage value.

[0015] A further approach is to record the gradual PWM signal as the target PWM signal when the current voltage value is equal to the turn-on voltage value.

[0016] Therefore, after recording the target PWM signal, when the LED chip is adjusted to the lowest brightness, the target PWM signal can be used directly without repeating the test to obtain the target PWM value. Attached Figure Description

[0017] Figure 1 This is a circuit schematic diagram of the low brightness consistency automatic compensation circuit embodiment of the multi-channel constant current chip of the present invention.

[0018] Figure 2 This is a flowchart of an embodiment of the control method for the low brightness consistency automatic compensation circuit of the multi-channel constant current chip of the present invention.

[0019] The present invention will be further described below with reference to the accompanying drawings and embodiments. Detailed Implementation

[0020] The multi-channel constant current chip low brightness consistency automatic compensation circuit of the present invention controls the dummy load current diversion of the current adjustment module through the main control module, so that the current of the same LED chip is consistent at the lowest brightness, and thus the brightness is consistent.

[0021] Example of a multi-channel constant current chip low brightness consistency automatic compensation circuit:

[0022] This embodiment uses an N-channel constant current chip low-brightness consistency automatic compensation circuit for illustration, where N is a positive integer greater than 1. See also... Figure 1 , Figure 1 The circuit diagrams of the first and Nth constant current chip low brightness consistency automatic compensation circuits are shown in detail. The circuit diagrams of other constant current chip low brightness consistency automatic compensation circuits that may exist between the first and Nth channels are not shown.

[0023] The first constant current chip low-brightness consistency automatic compensation circuit includes a main control module 11, a first constant current module 12, a first current adjustment module 13, and a first voltage detection circuit 14. The main control module 11 includes an MCU. The first constant current module 12 includes a first constant current chip U4. The first current adjustment module 13 includes a first dummy load R12 and a first dummy load control circuit. The first dummy load control circuit consists of a first optocoupler U3 and a tenth resistor R10. Pin 1 of the first optocoupler U3 receives a 3.3V DC voltage, and pin 2 receives the first target PWM signal PWM1 from the MCU. The first voltage detection circuit 14 includes a first sampling resistor group and a second sampling resistor group. The first sampling resistor group includes a first resistor R15 and a second resistor R17, and the second sampling resistor group includes a third resistor R14 and a fourth resistor R16. The first end of the first resistor R15 is connected to the positive terminal of the output of the first constant current module 12, i.e., LED+. The second end of the first resistor R15 is connected to the MCU and the first end of the second resistor R17, and the second end of the second resistor R17 is grounded. The first end of the third resistor R14 is connected to the negative terminal of the output of the first constant current module 12, namely LED1-. The second end of the third resistor R14 is connected to the MCU and the first end of the fourth resistor R16. The second end of the fourth resistor R16 is grounded.

[0024] The Nth constant current chip low-brightness consistency automatic compensation circuit includes a main control module 11, a second constant current module 22, a second current adjustment module 23, and a second voltage detection circuit 24. The main control module 11 is shared with the first constant current chip low-brightness consistency automatic compensation circuit. The first constant current module 22 includes a second constant current chip U6. The second current adjustment module 23 includes a second dummy load R21 and a second dummy load control circuit. The second dummy load control circuit consists of a second optocoupler U5 and a nineteenth resistor R19. Pin 1 of the second optocoupler U6 receives a 3.3V DC voltage, and pin 2 receives the second target PWM signal PWMN from the MCU. The second voltage detection circuit 24 includes a third sampling resistor group and a fourth sampling resistor group. The third sampling resistor group includes a fifth resistor R24 ​​and a sixth resistor R26, and the second sampling resistor group includes a seventh resistor R23 and an eighth resistor R25. The first terminal of the fifth resistor R24 ​​is connected to the positive terminal of the output of the second constant current module 22. The output of the second constant current module 22 shares a common anode with the output of the first constant current module 21, and its positive terminal is also LED+. The second terminal of the fifth resistor R24 ​​is connected to the MCU and the first terminal of the sixth resistor R26, and the second terminal of the sixth resistor R26 is grounded. The first terminal of the seventh resistor R23 is connected to the negative terminal of the output of the second constant current module 22, i.e., LEDN-. The second terminal of the seventh resistor R23 is connected to the MCU and the first terminal of the eighth resistor R25, and the second terminal of the eighth resistor R25 is grounded.

[0025] An external LED chip (not shown in the figure) can be connected to terminal J1. The same LED chip is connected to both the first constant current chip low brightness consistency automatic compensation circuit and the Nth constant current chip low brightness consistency automatic compensation circuit. That is, the same lamp is connected. The current and brightness are the same when the constant current module is adjusted to the lowest brightness output. See the control method embodiment of the multi-channel constant current chip low brightness consistency automatic compensation circuit below for details.

[0026] Example of an automatic compensation device for low brightness consistency of multi-channel constant current chip:

[0027] The multi-channel constant current chip low brightness consistency automatic compensation device includes a housing, and the housing is provided with the multi-channel constant current chip low brightness consistency automatic compensation circuit of the above embodiment.

[0028] Example of a control method for a multi-channel constant current chip low-brightness consistency automatic compensation circuit:

[0029] This embodiment is based on the circuit implementation of the above embodiment. See [link / reference]. Figure 2 First, step S1 is executed, outputting a preset minimum PWM signal to the dimming terminal of the constant current chip. Specifically, the MCU outputs a first minimum PWM signal to the dimming terminal (pin 3) of the first constant current chip and a second minimum PWM signal to the dimming terminal (pin 3) of the second constant current chip, thereby ensuring that both the LED chips connected to the first and second constant current modules reach their minimum brightness. However, due to the differences in the constant current chips, the minimum brightness achievable by identical LED chips differs, resulting in inconsistent brightness between the two LED chips.

[0030] Continue with step S2 to obtain the start-up voltage value and the current voltage value. For the same LED chip, the start-up voltage value is basically the same, and this start-up voltage value can be pre-selected and stored in the flash memory integrated in the MCU. The current voltage value can be obtained through the first voltage detection circuit and the second voltage detection circuit respectively.

[0031] Then, step S3 is executed, outputting a gradual PWM signal to the controlled terminal of the dummy load circuit. When the current voltage value is equal to the start-up voltage value, the duty cycle of the gradual PWM signal remains unchanged. When the voltage across both LED chips is the start-up voltage value V0, the current I0 flowing through both LED chips is the same. When the current flowing through both LED chips is I0, the voltage value across them is the start-up voltage value V0. Therefore: P1 = V0I0 + V0 2 / R1=V1I1 and P2=V0I0+V0 2 / R2=V2I2, where P1 is the power output of the first constant current chip, V1 is the voltage output of the first constant current chip, I1 is the current output of the first constant current chip, P2 is the power output of the second constant current chip under the second minimum PWM signal, V2 is the voltage output of the second constant current chip, I2 is the current output of the second constant current chip, P1≠P2, R1 is the target resistance value of the first dummy load, and R2 is the target resistance value of the second dummy load. Since the resistance of the dummy load is related to the duty cycle of the PWM signal received by the optocoupler, i.e., the resistance of the dummy load = actual resistance / (1 - duty cycle), where the actual resistance is the resistance of R12 or R21, the MCU can output a gradually increasing PWM signal to control the resistance of the connected dummy load. This means outputting a PWM signal with a gradually increasing duty cycle to the first optocoupler and another PWM signal with a gradually increasing duty cycle to the second optocoupler. Simultaneously, the first and second voltage detection circuits detect the voltage across the LED chip. When the voltage across the LED chip gradually changes to V0, the duty cycle of the current gradually increasing PWM signal remains unchanged, and the gradually increasing PWM signals at this point are recorded as the first target PWM signal PWM1 and the second target PWM signal PWMN, respectively. The duty cycles of the first target PWM signal PWM1 and the second target PWM signal PWMN may be different. By adjusting the target PWM signal, lamps containing the same LED chip can achieve consistent brightness when adjusted to the lowest brightness setting.

[0032] In summary, the control method of the multi-channel constant current chip low brightness consistency automatic compensation circuit of the present invention is based on the multi-channel constant current chip low brightness consistency automatic compensation circuit. It controls the resistance value of the dummy load through the PWM signal, thereby controlling the current flowing through the LED chip, so that multiple identical LED chips maintain consistent current and brightness when adjusted to the lowest brightness, avoiding the influence of differences in constant current chips.

Claims

1. A multi-channel constant current chip low brightness consistency automatic compensation circuit, characterized in that, include: The first constant current chip low brightness consistency automatic compensation circuit and the Nth constant current chip low brightness consistency automatic compensation circuit. The first constant current chip low brightness consistency automatic compensation circuit and the Nth constant current chip low brightness consistency automatic compensation circuit share a main control module, and each includes: a constant current module, a current adjustment module, and a voltage detection circuit. The constant current module includes a constant current chip, and the current adjustment module includes a dummy load control circuit and a dummy load. The main control module is connected to the dimming terminal of the constant current chip, the control terminal of the dummy load control circuit, and the voltage detection circuit. The current adjustment module is connected to the output terminal of the constant current module, and the output terminal of the constant current module is connected to the LED chip. The controlled terminal of the dummy load control circuit is connected to the dummy load and the output terminal of the constant current module. The dummy load is connected to the output terminal of the constant current module, and the voltage detection circuit is connected to the LED chip. The dummy load and the LED chip are connected in parallel to the output terminal of the constant current module. The constant current module is used to supply power to the LED chip; The voltage detection circuit is used to detect the current voltage value of the LED chip and transmit it to the main control module; The main control module is used to change the resistance value of the dummy load by adjusting the gradual PWM signal. The current voltage value is detected in real time and compared with the start-up voltage value to determine whether the current flowing through the LED chip is the current corresponding to the lowest brightness of the LED chip. When the current voltage value is equal to the start-up voltage value, the gradual PWM signal is recorded as the target PWM signal. When the target PWM signal is input to the controlled terminal of the dummy load control circuit, the voltage across the LED chip is the start-up voltage value. The dummy load control circuit is used to change the resistance value of the dummy load according to the target PWM signal; The dummy load control circuit includes an optocoupler, the control terminal of the dummy load control circuit is the input terminal of the optocoupler, and the controlled terminal of the dummy load control circuit is the output terminal of the optocoupler. The first constant current chip low brightness consistency automatic compensation circuit and the Nth constant current chip low brightness consistency automatic compensation circuit share the same main control module, so P1=V0I0+V0 2 / R1=V1I1,P2=V0I0+V0 2 / R2=V2I2, P1 is the power output of the first constant current chip, V1 is the voltage output of the first constant current chip, I1 is the current output of the first constant current chip, P2 is the power output of the second constant current chip under the second minimum PWM signal, V2 is the voltage output of the second constant current chip, I2 is the current output of the second constant current chip, P1≠P2, R1 is the target resistance value of the first dummy load, R2 is the target resistance value of the second dummy load, the resistance value of the dummy load = the actual resistance value / (1 Duty cycle).

2. A multi-channel constant current chip low brightness consistency automatic compensation device, comprising a housing, characterized in that: The housing includes the multi-channel constant current chip low brightness consistency automatic compensation circuit as described in claim 1.

3. A control method based on the multi-channel constant current chip low brightness consistency automatic compensation circuit as described in claim 1, characterized in that, Includes the following steps: Output a preset minimum PWM signal to the dimming terminal of the constant current chip; Obtain the activation voltage value and the current voltage value; The gradual PWM signal is output to the controlled terminal of the dummy load control circuit, and the duty cycle of the gradual PWM signal remains unchanged when the current voltage value is equal to the turn-on voltage value. When the current voltage value is equal to the start-up voltage value, the gradual PWM signal is recorded as the target PWM signal.

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