A serial LED fault detection method based on current detection

Abstract

The application relates to the field of LED fault detection, in particular to a serial LED fault detection method based on current detection, which comprises the following steps: powering on a serial LED circuit and keeping the serial LED circuit in an extinguished state to collect background current; lighting a first light-emitting color of a first stage to collect first current; comparing the first current minus the background current with a first preset reference current to judge whether the first light-emitting color of the first stage is normal; lighting a second light-emitting color of the first stage to collect second current; comparing the second current minus the first current with a second preset reference current to judge whether the second light-emitting color of the first stage is normal; lighting three light-emitting colors of each stage in turn to judge whether the three light-emitting colors of each stage are normal. The fault judgment method can efficiently and accurately judge the light-emitting color faults of each LED light-emitting chip in the serial LED circuit by taking the current increment of the light-emitting color lighted once as the basis.

Description

TECHNICAL FIELD

[0001] The present application relates to the field of LED fault detection, in particular to a serial LED fault detection method based on current detection. BACKGROUND

[0002] The development of LED light emitting technology, and the advantages of long service life, high light efficiency, no radiation and low power consumption of LED itself, make LED light emitting chip more and more widely used in various fields, especially serial LED based on bus control. However, in the actual use process, since there are many LED light emitting chips in serial LED, when a certain LED light emitting chip is out of order, it will affect the light emitting effect of the whole serial LED.

[0003] The existing LED fault detection mainly detects open circuit fault or short circuit fault of LED, but in some application scenarios with high light emitting effect requirements, it is also necessary to detect whether the light emitting color of the LED light emitting chip is normal, and the existing fault detection scheme is powerless for this. It can only be judged whether the LED light emitting chip is faulty by manually observing the light emitting color of the LED light emitting chip, which is too large for the workload of serial LED, the detection efficiency is low, and manual observation needs to rely on observation experience and will have errors, greatly reducing the accuracy of fault detection. SUMMARY

[0004] The technical problem to be solved by the present application is to provide a serial LED fault detection method based on current detection, which can efficiently and accurately detect the light emitting color fault of each LED light emitting chip in the serial LED circuit.

[0005] The technical solution of the present application to solve the above technical problem is as follows: a serial LED fault detection method based on current detection, for detecting the fault of serial LED circuit through a current detection circuit; wherein the current detection circuit comprises a microprocessor and a current sampling resistor for converting the current flowing into the serial LED circuit into voltage, the serial LED circuit comprises multiple stages of LED light emitting chips, each stage of LED light emitting chip has RGB three kinds of light emitting colors, the power supply end of each stage of LED light emitting chip is connected to the power supply through the sampling resistor, the data input end of the first stage of LED light emitting chip is connected to the PWM signal, and the data output end of the previous stage of LED light emitting chip is connected to the data input end of the next stage of LED light emitting chip; the serial LED fault detection method based on current detection comprises the following steps,

[0006] S1, power on the serial LED circuit, and keep all stages of LED light emitting chips in the serial LED circuit in an extinguished state, collect the current flowing through the current sampling resistor at this time, and take the current as the background current of the first stage of LED light emitting chip;

[0007] S2, the microprocessor sends a PWM signal to light the first light-emitting color of the first LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a first current; the first current is subtracted by the background current to obtain the actual current of the first light-emitting color of the first LED light-emitting chip, and the actual current of the first light-emitting color of the first LED light-emitting chip is compared with a first preset reference current to determine whether the first light-emitting color of the first LED light-emitting chip LED1 is normal;

[0008] S3, the microprocessor sends a PWM signal to light the second light-emitting color of the first LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a second current; the second current is subtracted by the first current to obtain the actual current of the second light-emitting color of the first LED light-emitting chip, and the actual current of the second light-emitting color of the first LED light-emitting chip is compared with a second preset reference current to determine whether the second light-emitting color of the first LED light-emitting chip LED1 is normal;

[0009] S4, the microprocessor sends a PWM signal to light the third light-emitting color of the first LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a third current; the third current is subtracted by the second current to obtain the actual current of the third light-emitting color of the first LED light-emitting chip, and the actual current of the third light-emitting color of the first LED light-emitting chip is compared with a third preset reference current to determine whether the third light-emitting color of the first LED light-emitting chip LED1 is normal;

[0010] S5, the current flowing through the current sampling resistor after the three light-emitting colors of the previous LED light-emitting chip are fully lit is collected as the background current of the next LED light-emitting chip, and the method of S2-S4 is used to light the three light-emitting colors of each LED light-emitting chip in turn; whether the three light-emitting colors of each LED light-emitting chip are normal is determined.

[0011] The beneficial effects of the present application are: in the current detection-based serial LED fault detection method, the three light colors of each level of LED light emitting chip in the serial LED circuit are automatically and sequentially lit by the PWM signal. After each light color is lit, the current flowing through the current sampling resistor will have a current increment, which is the actual current of the light color corresponding to the level of LED light emitting chip. However, the current flowing through the LED light emitting chip is different, and the light color is also different. Therefore, by comparing the actual current of the light color corresponding to the level of LED light emitting chip with the reference current of the light color, it can be determined whether the light color corresponding to the level of LED light emitting chip is normal, that is, the light color fault of the LED light emitting chip. The fault detection method of the present application relies on the current increment of the light color lit once by the microprocessor detection as the basis for fault detection, without manual participation, and can efficiently and accurately detect the light color fault of each LED light emitting chip in the serial LED circuit. BRIEF DESCRIPTION OF DRAWINGS

[0012] Figure 1 The structural block diagram of the current detection circuit in the current detection-based serial LED fault detection method of the present application is shown in the figure.

[0013] Figure 2 The flow chart of the current detection-based serial LED fault detection method of the present application is shown in the figure.

[0014] Figure 3 The circuit principle diagram of the current detection circuit and the serial LED circuit in the current detection-based serial LED fault detection method of the present application is shown in the figure. DETAILED DESCRIPTION

[0015] The principles and features of the present application are described below in conjunction with the accompanying drawings, and the examples are only used to explain the present application and are not used to limit the scope of the present application.

[0016] A current detection-based serial LED fault detection method is used to detect the fault of the serial LED circuit by the current detection circuit. Wherein, as Figure 1As shown, the current detection circuit includes a microprocessor (not shown) and a current sampling resistor for converting the current flowing into the serial LED circuit into voltage, and further includes a power switch sub-circuit, a differential amplification sub-circuit, a voltage comparison sub-circuit, a peak holding sub-circuit and an overcurrent protection sub-circuit; one end of the power switch sub-circuit is connected with a power supply, the other end of the power switch sub-circuit is connected with the power supply end of each stage of LED light emitting chip through the current sampling resistor, and the controlled end of the power switch sub-circuit is connected with the power supply enable signal output interface of the microprocessor; the two input ends of the differential amplification sub-circuit are connected at the two ends of the current sampling resistor respectively, the output end of the differential amplification sub-circuit is connected on the input end of the voltage comparison sub-circuit, and the output end of the differential amplification sub-circuit is further connected with the A / D conversion interface of the microprocessor; the output end of the voltage comparison sub-circuit is connected on the input end of the peak holding sub-circuit, the output end of the peak holding sub-circuit is connected on the controlled end of the power switch sub-circuit through the overcurrent protection sub-circuit; the output end of the peak holding sub-circuit is further connected with the high level overcurrent indication signal input interface of the microprocessor; and the input end of the peak holding sub-circuit is further connected with the power supply enable signal output interface of the microprocessor.

[0017] The serial LED circuit includes multiple stages of LED light emitting chips, each stage of LED light emitting chip has RGB three kinds of light emitting colors, the power supply end of each stage of LED light emitting chip is connected with the power supply through the sampling resistor, the data input end of the first stage of LED light emitting chip is connected with the PWM signal, and the data output end of the previous stage of LED light emitting chip is connected with the data input end of the next stage of LED light emitting chip.

[0018] As shown in the figure, Figure 2 The serial LED fault detection method based on current detection includes the following steps,

[0019] S1, power on the serial LED circuit, and keep all the stage LED light emitting chips in the serial LED circuit in an extinguished state, collect the current flowing through the current sampling resistor at this time, and take the current as the background current of the first stage of LED light emitting chip;

[0020] S2, the microprocessor sends a PWM signal to light up the first light emitting color of the first stage of LED light emitting chip, collects the current flowing through the current sampling resistor at this time, and obtains the first current; subtracts the background current from the first current to obtain the actual current of the first light emitting color of the first stage of LED light emitting chip, compares the actual current of the first light emitting color of the first stage of LED light emitting chip with the first preset reference current, and judges whether the first light emitting color of the first stage of LED light emitting chip LED1 is normal;

[0021] S3, the microprocessor sends a PWM signal to light the second light-emitting color of the first-stage LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a second current; the second current is subtracted from the first current to obtain the actual current of the second light-emitting color of the first-stage LED light-emitting chip, and the actual current of the second light-emitting color of the first-stage LED light-emitting chip is compared with a second preset reference current to determine whether the second light-emitting color of the first-stage LED light-emitting chip LED1 is normal;

[0022] S4, the microprocessor sends a PWM signal to light the third light-emitting color of the first-stage LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a third current; the third current is subtracted from the second current to obtain the actual current of the third light-emitting color of the first-stage LED light-emitting chip, and the actual current of the third light-emitting color of the first-stage LED light-emitting chip is compared with a third preset reference current to determine whether the third light-emitting color of the first-stage LED light-emitting chip LED1 is normal;

[0023] S5, the current flowing through the current sampling resistor after the three light-emitting colors of the previous-stage LED light-emitting chip are all lighted is taken as the background current of the next-stage LED light-emitting chip, and the method of S2-S4 is used to light the three light-emitting colors of each stage of LED light-emitting chip in turn; whether the three light-emitting colors of each stage of LED light-emitting chip are normal is determined.

[0024] In the specific embodiment, the specific method of powering on the serial LED circuit is that the microprocessor sends a power enable signal to make the power switch subcircuit conductive, and then makes the serial LED circuit conductive with the power supply, and the serial LED circuit is powered on.

[0025] In the specific embodiment, the specific process of collecting the current flowing through the current sampling resistor is that the differential amplification subcircuit amplifies the voltage between the two ends of the current sampling resistor to obtain a voltage amplification signal, and the voltage amplification signal is transmitted to the microprocessor, and the microprocessor performs A / D conversion on the voltage amplification signal to obtain the current flowing through the current sampling resistor.

[0026] In the embodiment, the overcurrent protection of the serial LED circuit is further included in the process of collecting the current flowing through the current sampling resistor, and the specific process of the overcurrent protection is that the voltage comparison sub-circuit is used to compare the voltage amplification signal output by the differential amplification sub-circuit with the reference voltage signal, to determine whether the voltage amplification signal is greater than the reference voltage signal, and output a high level signal in the case that the voltage amplification signal is greater than the reference voltage signal; the high level signal output by the voltage comparison sub-circuit acts on the peak value holding sub-circuit, so that the peak value holding sub-circuit still outputs a stable peak value signal even if the voltage comparison sub-circuit no longer outputs a high level signal; the peak value signal output by the peak value holding sub-circuit controls the action of the overcurrent protection sub-circuit, the action of the overcurrent protection sub-circuit controls the disconnection of the power switch sub-circuit, and the overcurrent protection of the serial LED circuit is completed.

[0027] Figure 3 The circuit principle diagram of the current detection circuit and the serial LED circuit in the serial LED fault detection method based on current detection is shown in the embodiment. Figure 3

[0028] The power switch sub-circuit includes a first MOS tube and a second MOS tube; the source of the first MOS tube is one end of the power switch sub-circuit and is used to be connected with the power supply, the source of the first MOS tube is further grounded through a second capacitor, the source of the first MOS tube is further connected to the gate of the first MOS tube through a thirteenth resistor, the drain of the first MOS tube is the other end of the power switch sub-circuit and is used to be connected with the power supply end of each stage of LED light emitting chip through the current sampling resistor; the gate of the first MOS tube is connected to the drain of the second MOS tube through a twelfth resistor, the source of the second MOS tube is grounded, the gate of the second MOS tube is the controlled end of the power switch sub-circuit and is used to be connected with the power supply enable signal output interface of the microprocessor through a fifth resistor, and the gate of the second MOS tube is further grounded through an eleventh resistor.

[0029] ​The differential amplification sub-circuit comprises an operational amplifier, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor and an eighteenth resistor; one end of the eighteenth resistor is an input end of the differential amplification sub-circuit and is connected to one end of the current sampling resistor connected to the power supply switch sub-circuit, the other end of the eighteenth resistor is connected to a non-inverting input end of the operational amplifier, the non-inverting input end of the operational amplifier is grounded through the sixteenth resistor, one end of the seventeenth resistor is another input end of the differential amplification sub-circuit and is connected to one end of the current sampling resistor connected to the power supply end of each stage of LED light emitting chip, the other end of the seventeenth resistor is connected to an inverting input end of the operational amplifier, the inverting input end of the operational amplifier is connected to the output end of the operational amplifier through the fifteenth resistor, the output end of the operational amplifier is an output end of the differential amplification sub-circuit and is grounded through a third capacitor and a fourteenth resistor in parallel, and the output end of the operational amplifier is also connected to an A / D conversion interface of the microprocessor; a positive power supply end of the operational amplifier is connected to a logic power supply, and a negative power supply end of the operational amplifier is grounded; the resistance value of the eighteenth resistor is equal to that of the seventeenth resistor, and the resistance value of the sixteenth resistor is equal to that of the fifteenth resistor.

[0030] The voltage comparison sub-circuit comprises a first comparator, a seventh resistor and an eighth resistor; a non-inverting input end of the first comparator is an input end of the voltage comparison sub-circuit and is connected to the output end of the differential amplification sub-circuit, the inverting input end of the first comparator is grounded through the seventh resistor, and the inverting input end of the first comparator is also connected to a logic power supply through the eighth resistor; a positive power supply voltage end of the first comparator is connected to the logic power supply, a negative power supply voltage end of the first comparator is grounded, and an output end of the first comparator is an output end of the voltage comparison sub-circuit and is connected to an input end of the peak value holding sub-circuit through a first diode.

[0031] The peak holding sub-circuit comprises a second comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a sixth resistor and a first capacitor; one end of the fourth resistor is an input end of the peak holding sub-circuit and is connected to an output end of the voltage comparison sub-circuit through a first diode, the other end of the fourth resistor is connected to a positive input end of the second comparator, and the positive input end of the second comparator is grounded through the first resistor; a negative input end of the second comparator is connected to a logic power supply through the second resistor, and the negative input end of the second comparator is grounded through the third resistor and the first capacitor in parallel; an output end of the second comparator is an output end of the peak holding sub-circuit and is connected to a controlled end of the power switch sub-circuit through the overcurrent protection sub-circuit, the output end of the second comparator is also connected to the positive input end of the second comparator through the sixth resistor, and the output end of the second comparator is also connected to a high-level overcurrent indication signal input interface of a microprocessor; and the positive input end of the second comparator is also connected to a power supply enable signal output interface of the microprocessor through a second diode.

[0032] The overcurrent protection sub-circuit comprises a third MOS tube, a ninth resistor and a tenth resistor; one end of the ninth resistor is connected to an output end of the peak holding sub-circuit, the other end of the ninth resistor is connected to a gate of the third MOS tube, the gate of the third MOS tube is grounded through the tenth resistor, a source of the third MOS tube is grounded, and a drain of the third MOS tube is connected to a controlled end of the power switch sub-circuit.

[0033] In the serial LED circuit, the power supply ends of the LED light emitting chips of each stage are also grounded through corresponding capacitors, and the ground ends of the LED light emitting chips of each stage are grounded. In this embodiment, the serial LED circuit is provided with n stages of LED light emitting chips, namely, a first stage of LED light emitting chips LED1, a second stage of LED light emitting chips LED2, …, and an n-th stage of LED light emitting chips LEDn, the power supply end of the first stage of LED light emitting chips LED1 is grounded through a fourth capacitor, the power supply end of the second stage of LED light emitting chips LED2 is grounded through a fifth capacitor, and the power supply end of the n-th stage of LED light emitting chips LEDn is grounded through an n+3 capacitor.

[0034] In the present application:

[0035] (1) The first MOS Q1 is a power switch, controlled by the second MOS Q2, and the second MOS Q2 is controlled by the power enable signal output by the power enable signal output interface POWER_EN of the microprocessor. When the power enable signal is high, the drain and source of the second MOS Q2 are turned on, and the drain and source of the first MOS Q1 are also turned on. The power source POWER_IN is led to the output port POWER through the current sampling resistor R19, and at this time the serial LED circuit is powered on.

[0036] (2) The current sampling resistor R19 converts the current flowing into the serial LED circuit into a voltage.

[0037] (3) The operational amplifier U2A, the eighteenth resistor R18, the seventeenth resistor R17, the sixteenth resistor R16, and the fifteenth resistor R15 constitute a differential amplification sub-circuit, which amplifies the voltage across the current sampling resistor R19; preferably R18=R17, R16=R15, then the amplification factor of the differential amplification sub-circuit =R15 / R17; the amplified voltage signal is output from the output terminal of the operational amplifier U2A to the A / D conversion interface of the microprocessor, which can be converted into A / D data by the microprocessor; specifically, the calculation formula of the current signal flowing into the serial LED circuit is: current value=(A / D data*A / D reference voltage) / (A / D total range*amplification factor*R19); wherein the A / D reference voltage is the reference voltage of the A / D conversion circuit in the microprocessor, the A / D total range is the total range of the A / D conversion circuit in the microprocessor, the unit of voltage is V, the unit of current is A, and the unit of resistance is ohm.

[0038] (4) The current passing through the current sampling resistor R19 becomes a voltage amplification signal at the output of the operational amplifier U2A.

[0039] (5) The first comparator U1A, the eighth resistor R8, and the seventh resistor R7 constitute an overvoltage comparison sub-circuit. When the voltage amplification signal output by the operational amplifier U2A exceeds the voltage (reference voltage signal) at the inverting input terminal of the first comparator U1A, the first comparator U1A outputs a high level. In combination with (4), the first comparator U1A outputs a high level when overcurrent occurs.

[0040] (6) The second comparator U1B and the sixth resistor R6, the first resistor R1, the second resistor R2, the third resistor R3 and the fourth resistor R4 constitute a peak holding sub-circuit. When the high level output by the first comparator U1A passes through the fourth resistor R4 and the first diode D1, the potential of the non-inverting input of the second comparator U1B is raised, so that the potential of the non-inverting input of the second comparator U1B is higher than that of the inverting input of the second comparator U1B, and the second comparator U1B outputs a high level; at this time, since the high level output by the second comparator U1B raises the potential of the non-inverting input of the second comparator through the sixth resistor R6, and the resistance pairs composed of the first resistor R1 and the sixth resistor R6 and the second resistor R2 and the third resistor R3 are designed to be appropriate, even if the first comparator U1A no longer outputs a high level, the potential of the non-inverting input of the second comparator U1B is still higher than that of the inverting input, thereby realizing stable holding of the peak value.

[0041] (7) The output high level of the second comparator U1B makes the third MOS tube Q3 conduct, the second MOS tube Q2 cut off, and the first MOS tube Q1 shut down, thereby playing a shutdown protection role when the current overflows. At the same time, the output high level of the second comparator U1B overflows the indication signal to the microprocessor through the high level overcurrent indication signal input interface OCP.

[0042] (8) Reset of the peak holding sub-circuit: when the power enable signal is low, the potential of the non-inverting input of the second comparator U1B is pulled low and is lower than that of the inverting input of the second comparator U1B, the second comparator U1B outputs a low level, and the second comparator U1B no longer holds the peak value, and the state is restored.

[0043] (9) The feature of the serial LED circuit is to transmit RGB data through PWM. Each stage of the serial LED has three kinds of light-emitting colors of RGB. When it is needed to detect whether the serial LED circuit is faulty, the following operations can be performed:

[0044] 【1】 The power enable signal output by the power enable signal output interface POWER_EN of the microprocessor turns on the first MOS tube Q1 to power the serial LED circuit, at this time, all the LED light-emitting chips of all stages are in an extinguished state, and a delay time is set to stabilize the power supply.

[0045] 【2】 Sampling is performed through the A / D conversion interface of the microprocessor, and the current can be calculated according to the sampled data, the formula for calculating the current is referred to (3), and the current sampled at this time is the background current.

[0046] [3] The PWM signal output by the PWM signal output interface of the microprocessor makes the first-level LED chip LED1 light up the first luminous color (e.g., red) at the maximum value. Then, the current at this time is sampled by the A / D conversion interface of the microprocessor to obtain the first current. The first current is subtracted from the background current to get the actual current of the first luminous color of the first-level LED chip LED1. The actual current of the first luminous color of the first-level LED chip LED1 is compared with the first preset reference current to determine whether the first luminous color of the first-level LED chip LED1 is normal.

[0047] [4] The PWM signal output through the PWM signal output interface of the microprocessor is used to light up the second light color (e.g., green) of the first-level LED chip LED1. The current at this time is sampled through the A / D conversion interface of the microprocessor to obtain the second current. The second current is subtracted from the first current to obtain the actual current of the second light color of the first-level LED chip LED1 (when lighting up different light colors of the same level LED chip, the light colors previously lit by the LED chip of that level do not go out. That is to say, the current will increase for each light color lit up, so the current has an increment, and the current increment is the actual current value of the light color lit up). The actual current of the second light color of the first-level LED chip LED1 is compared with the second preset reference current to determine whether the second light color of the first-level LED chip LED1 is normal.

[0048] [5] The PWM signal output through the PWM signal output interface of the microprocessor is used to light up the third light-emitting color (e.g., blue) of the first-level LED chip LED1. The current at this time is sampled through the A / D conversion interface of the microprocessor to obtain the third current. The third current is subtracted from the second current to obtain the actual current of the third light-emitting color of the first-level LED chip LED1. The actual current of the third light-emitting color of the first-level LED chip LED1 is compared with the third preset reference current to determine whether the third light-emitting color of the first-level LED chip LED1 is normal.

[0049] 【6】PWM signal outputted by PWM signal output interface of microprocessor makes second stage LED light emitting chip LED1 light up maximum value of first light emitting color, and then fourth current is obtained by sampling current at this time through A / D conversion interface of microprocessor, and actual current of first light emitting color of second stage LED light emitting chip LED2 is obtained by subtracting third current from fourth current (when different stage LED light emitting chip is lighted up, three light emitting colors of previous stage LED light emitting chip lighted up do not extinguish), and whether first light emitting color of second stage LED light emitting chip LED2 is normal or not can be judged by comparing actual current of first light emitting color of second stage LED light emitting chip LED2 with first preset reference current.

[0050] 【7】PWM signal outputted by PWM signal output interface of microprocessor makes second stage LED light emitting chip LED2 light up maximum value of second light emitting color again, and then fifth current is obtained by sampling current at this time through A / D conversion interface of microprocessor, and actual current of second light emitting color of second stage LED light emitting chip LED2 is obtained by subtracting fourth current from fifth current, and whether second light emitting color of second stage LED light emitting chip LED2 is normal or not can be judged by comparing actual current of second light emitting color of second stage LED light emitting chip LED2 with second preset reference current.

[0051] 【8】PWM signal outputted by PWM signal output interface of microprocessor makes third light emitting color of second stage LED light emitting chip LED2 light up maximum value again, and then sixth current is obtained by sampling current at this time through A / D conversion interface of microprocessor, and actual current of third light emitting color of second stage LED light emitting chip LED2 is obtained by subtracting fifth current from sixth current, and whether third light emitting color of second stage LED light emitting chip LED2 is normal or not can be judged by comparing actual current of third light emitting color of second stage LED light emitting chip LED2 with third preset reference current.

[0052] 【9】By analogy, RGB three light emitting colors of each stage LED light emitting chip are lighted up in turn, and fault condition of three light emitting colors of each stage LED light emitting chip can be judged by current increment of each light emitting color lighted up once and corresponding preset reference current.

[0053] In the current detection based serial LED fault detection method, the three light emitting colors of each LED light emitting chip in the serial LED circuit are automatically and sequentially lightened by the PWM signal, and the current flowing through the current sampling resistor has a current increment after each light emitting color is lightened, and the current increment is the actual current of the light emitting color corresponding to the LED light emitting chip; however, the current flowing through the LED light emitting chip is different, and the light emitting color is also different, so by comparing the actual current of the light emitting color corresponding to the LED light emitting chip with the reference current of the light emitting color, it can be judged whether the light emitting color corresponding to the LED light emitting chip is normal, that is, the light emitting color fault of the LED light emitting chip; the fault judgment method of the application relies on the current increment of the lightened light emitting color detected by the microprocessor as the basis for fault judgment, without manual participation, and can efficiently and accurately detect the light emitting color fault of each LED light emitting chip in the serial LED circuit.

[0054] In addition, during fault detection, a current detection circuit with current limiting protection function is used to detect the fault of the serial LED circuit, the current detection circuit converts the current signal flowing into the serial LED circuit into a voltage signal through a current sampling resistor, amplifies the voltage signal by a differential amplification sub-circuit, and judges whether the amplified voltage signal exceeds the reference voltage signal by a voltage comparison sub-circuit, when the reference voltage signal is exceeded, it means that the current signal flowing into the serial LED circuit is too large, so the voltage comparison sub-circuit outputs a high level to make the peak value maintaining sub-circuit also output a high level, even if the voltage comparison sub-circuit no longer outputs a high level, the peak value maintaining sub-circuit also outputs a high level, realizing the stable maintenance of the peak value, and the high level of the peak value maintaining sub-circuit outputting the stable maintenance of the peak value controls the overcurrent protection sub-circuit to act, so that the power switch sub-circuit is disconnected, realizing stable overcurrent protection, avoiding frequent protection and self-recovery of the power supply leading to unstable light emission of the LED light emitting chip, so as to ensure the smooth progress of the fault detection and avoid damaging the LED light emitting chip.

[0055] The above only describes the preferred embodiments of the application, and is not intended to limit the application, any modification, equivalent replacement, improvement, etc. within the spirit and principles of the application should be included in the protection scope of the application.

Claims

1. A current detection based serial LED fault detection method, characterized in that: The serial LED fault detection method based on current detection is used for detecting the fault of a serial LED circuit through a current detection circuit; wherein the current detection circuit comprises a microprocessor and a current sampling resistor for converting the current flowing into the serial LED circuit into voltage, the serial LED circuit comprises a plurality of LED light emitting chips, each of which has RGB three kinds of light emitting colors, the power supply ends of the LED light emitting chips are connected to the power supply through the sampling resistor, the data input end of the first stage LED light emitting chip is connected to a PWM signal, and the data output end of the previous stage LED light emitting chip is connected to the data input end of the next stage LED light emitting chip; the current detection circuit further comprises a power switch sub-circuit, one end of the power switch sub-circuit is connected to the power supply, the other end of the power switch sub-circuit is connected to the power supply ends of the LED light emitting chips through the current sampling resistor, and the controlled end of the power switch sub-circuit is connected to the power supply enable signal output interface of the microprocessor; The serial LED fault detection method based on current detection comprises the following steps: S1, the serial LED circuit is powered on, and all the stage LED light emitting chips in the serial LED circuit are kept in an extinguished state, the current flowing through the current sampling resistor at this time is collected, and the current is taken as the background current of the first stage LED light emitting chip; the specific method for powering on the serial LED circuit is that the power switch sub-circuit is turned on by the microprocessor sending a power supply enable signal, and then the serial LED circuit is turned on between the power supply, and the serial LED circuit is powered on; S2, the first light emitting color of the first stage LED light emitting chip is lightened by the microprocessor sending a PWM signal, the current flowing through the current sampling resistor at this time is collected, and the first current is obtained; the actual current of the first light emitting color of the first stage LED light emitting chip is obtained by subtracting the background current from the first current, and whether the first light emitting color of the first stage LED light emitting chip LED1 is normal is judged by comparing the actual current of the first light emitting color of the first stage LED light emitting chip with the first preset reference current; S3, the second light emitting color of the first stage LED light emitting chip is lightened by the microprocessor sending a PWM signal, the current flowing through the current sampling resistor at this time is collected, and the second current is obtained; the actual current of the second light emitting color of the first stage LED light emitting chip is obtained by subtracting the first current from the second current, and whether the second light emitting color of the first stage LED light emitting chip LED1 is normal is judged by comparing the actual current of the second light emitting color of the first stage LED light emitting chip with the second preset reference current; S4, the microprocessor sends a PWM signal to light the third light-emitting color of the first-stage LED light-emitting chip, and collects the current flowing through the current sampling resistor at this time to obtain a third current; the third current is subtracted from the second current to obtain the actual current of the third light-emitting color of the first-stage LED light-emitting chip, and the actual current of the third light-emitting color of the first-stage LED light-emitting chip is compared with a third preset reference current to determine whether the third light-emitting color of the first-stage LED light-emitting chip LED1 is normal; S5, the current flowing through the current sampling resistor after all the three light-emitting colors of the LED light-emitting chip in the previous stage are lighted is collected as the background current of the LED light-emitting chip in the next stage, and the method of S2-S4 is used to light the three light-emitting colors of each stage of LED light-emitting chip in turn; whether the three light-emitting colors of each stage of LED light-emitting chip are normal is determined.

2. The current-sense based serial LED fault detection method of claim 1, wherein: The power switch subcircuit comprises a first MOS tube and a second MOS tube; one end of the power switch subcircuit is connected with the power supply through the source of the first MOS tube; the source of the first MOS tube is grounded through a second capacitor; the source of the first MOS tube is connected to the gate of the first MOS tube through a thirteenth resistor; the other end of the power switch subcircuit is connected with the power supply end of each stage of LED light-emitting chip through the current sampling resistor and the drain of the first MOS tube; the gate of the first MOS tube is connected to the drain of the second MOS tube through a twelfth resistor; the source of the second MOS tube is grounded; the gate of the second MOS tube is the controlled end of the power switch subcircuit and is connected with the power supply enable signal output interface of the microprocessor through a fifth resistor; and the gate of the second MOS tube is grounded through an eleventh resistor.

3. The current sense based serial LED fault detection method of claim 1, wherein: The current detection circuit further comprises a differential amplification subcircuit, two input ends of the differential amplification subcircuit are connected to both ends of the current sampling resistor, and the output end of the differential amplification subcircuit is connected with the A / D conversion interface of the microprocessor; The specific process of collecting the current flowing through the current sampling resistor is that the differential amplification subcircuit amplifies the voltage between both ends of the current sampling resistor to obtain a voltage amplification signal, and the voltage amplification signal is transmitted to the microprocessor; and the microprocessor performs A / D conversion on the voltage amplification signal to obtain the current flowing through the current sampling resistor.

4. The current sense based serial LED fault detection method of claim 3, wherein: The differential amplification sub-circuit comprises an operational amplifier, a fifteenth resistor, a sixteenth resistor, a seventeenth resistor and an eighteenth resistor; one end of the eighteenth resistor is an input end of the differential amplification sub-circuit and is connected to one end of the current sampling resistor connected to the power switch sub-circuit, the other end of the eighteenth resistor is connected to a non-inverting input end of the operational amplifier, the non-inverting input end of the operational amplifier is connected to ground through the sixteenth resistor, one end of the seventeenth resistor is another input end of the differential amplification sub-circuit and is connected to one end of the current sampling resistor connected to the power supply end of the LED light emitting chip, the other end of the seventeenth resistor is connected to an inverting input end of the operational amplifier, the inverting input end of the operational amplifier is connected to the output end of the operational amplifier through the fifteenth resistor, the output end of the operational amplifier is an output end of the differential amplification sub-circuit and is connected to ground through a third capacitor and a fourteenth resistor in parallel, and the output end of the operational amplifier is also connected to an A / D conversion interface of the microprocessor; a positive power supply end of the operational amplifier is connected to a logic power supply, and a negative power supply end of the operational amplifier is connected to ground; the resistance value of the eighteenth resistor is equal to that of the seventeenth resistor, and the resistance value of the sixteenth resistor is equal to that of the fifteenth resistor.

5. The current sense based serial LED fault detection method of claim 3, wherein: The current detection circuit further comprises a voltage comparison sub-circuit, a peak holding sub-circuit and an overcurrent protection sub-circuit; the input end of the voltage comparison sub-circuit is connected to the output end of the differential amplification sub-circuit, the output end of the voltage comparison sub-circuit is connected to the input end of the peak holding sub-circuit, the output end of the peak holding sub-circuit is connected to the controlled end of the power switch sub-circuit through the overcurrent protection sub-circuit; the output end of the peak holding sub-circuit is also connected to a high-level overcurrent indication signal input interface of the microprocessor; the input end of the peak holding sub-circuit is also connected to a power supply enable signal output interface of the microprocessor; In the process of collecting the current flowing through the current sampling resistor, the overcurrent protection of the serial LED circuit is further included, and the specific process of the overcurrent protection is as follows, The voltage comparison sub-circuit compares the voltage amplification signal output by the differential amplification sub-circuit with a reference voltage signal, judges whether the voltage amplification signal is greater than the reference voltage signal, and outputs a high-level signal in the case that the voltage amplification signal is greater than the reference voltage signal; The high-level signal output by the voltage comparison sub-circuit acts on the peak holding sub-circuit, so that the peak holding sub-circuit still outputs a stable peak signal even if the voltage comparison sub-circuit no longer outputs the high-level signal; The peak signal output by the peak holding sub-circuit controls the action of the overcurrent protection sub-circuit, the action of the overcurrent protection sub-circuit controls the disconnection of the power switch sub-circuit, and the overcurrent protection of the serial LED circuit is completed.

6. The current sense based serial LED fault detection method of claim 5, wherein: The voltage comparison sub-circuit comprises a first comparator, a seventh resistor and an eighth resistor; the non-inverting input terminal of the first comparator is the input terminal of the voltage comparison sub-circuit and is connected to the output terminal of the differential amplification sub-circuit, the inverting input terminal of the first comparator is connected to ground through the seventh resistor, and the inverting input terminal of the first comparator is also connected to the logic power supply through the eighth resistor; the positive power supply voltage terminal of the first comparator is connected to the logic power supply, the negative power supply voltage terminal of the first comparator is connected to ground, and the output terminal of the first comparator is the output terminal of the voltage comparison sub-circuit and is connected to the input terminal of the peak value holding sub-circuit through a first diode.

7. The current sense based serial LED fault detection method of claim 5, wherein: The peak value holding sub-circuit comprises a second comparator, a first resistor, a second resistor, a third resistor, a fourth resistor, a sixth resistor and a first capacitor; one end of the fourth resistor is the input terminal of the peak value holding sub-circuit and is connected to the output terminal of the voltage comparison sub-circuit through a first diode, the other end of the fourth resistor is connected to the non-inverting input terminal of the second comparator, and the non-inverting input terminal of the second comparator is also connected to ground through the first resistor; the inverting input terminal of the second comparator is connected to the logic power supply through the second resistor, and the inverting input terminal of the second comparator is also connected to ground through the third resistor and the first capacitor in parallel, the output terminal of the second comparator is the output terminal of the peak value holding sub-circuit and is connected to the controlled terminal of the power supply switch sub-circuit through the overcurrent protection sub-circuit, the output terminal of the second comparator is also connected to the non-inverting input terminal of the second comparator through the sixth resistor, the output terminal of the second comparator is also connected to the high-level overcurrent indication signal input interface of the microprocessor, and the non-inverting input terminal of the second comparator is also connected to the power supply enable signal output interface of the microprocessor through a second diode.

8. The current sense based serial LED fault detection method of claim 5, wherein: The overcurrent protection sub-circuit comprises a third MOS transistor, a ninth resistor and a tenth resistor; one end of the ninth resistor is connected to the output terminal of the peak value holding sub-circuit, the other end of the ninth resistor is connected to the gate of the third MOS transistor, the gate of the third MOS transistor is connected to ground through the tenth resistor, the source of the third MOS transistor is connected to ground, and the drain of the third MOS transistor is connected to the controlled terminal of the power supply switch sub-circuit.

9. The current sense based serial LED fault detection method of claim 5, wherein: In the serial LED circuit, the power supply terminals of the LED light emitting chips at each stage are also connected to ground through corresponding capacitors, and the ground terminals of the LED light emitting chips at each stage are connected to ground.

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