LED driving fault detection circuit and detection method

Abstract

The application provides an LED driving fault detection circuit and a detection method, the circuit comprising a driving branch, a freewheeling diode and a control module; the driving branch comprising an LED module, a control switch and a sampling resistor, the LED module comprising an inductor and at least two LED lamps in series; the inductor is used for storing electric charge and providing electric energy when discharging; the control switch controls the operation of the LED module during constant current driving; the freewheeling diode DS is connected in parallel with the LED module and is used for freewheeling when the driving branch discharges; the sampling input end of the control module is connected with the second end of the control switch, the control module collects the charging current and the action time of the control switch, and realizes the detection and judgment of LED driving fault according to the charging current and the action time of the control switch. The application realizes the effective detection and judgment of LED in the normal working mode.

Description

TECHNICAL FIELD

[0001] The present application relates to a fault detection technology, in particular to an LED driving fault detection circuit and method. BACKGROUND

[0002] LED is a nonlinear device, and a small change in forward voltage will cause a large change in forward current. Its volt-ampere characteristic changes with temperature. These reasons determine that constant current driving mode is more suitable for LED driving. However, LED failure will have a great impact on the operation of the circuit, which requires detection of LED failure.

[0003] At present, in the LED constant current driving circuit, the LED open short circuit detection method usually uses resistance voltage division to collect voltage value analysis. When collecting, the constant current driving needs to be turned off for a short time, and the LED cannot be detected in real time whether it is in open short circuit condition. SUMMARY

[0004] In view of the above-mentioned shortcomings of the prior art, the purpose of the present application is to provide an LED driving fault detection circuit and method, which can solve the problem that the LED cannot be detected in the normal working mode in the prior art.

[0005] To achieve the above-mentioned purposes and other related purposes, the present application provides an LED driving fault detection circuit, which comprises a driving branch, a freewheeling diode and a control module.

[0006] The driving branch comprises an LED module, a control switch and a sampling resistor. The LED module comprises an inductor and at least two LED lamps. The inductor is connected in series with the at least two LED lamps. The inductor is used to store electric charge and provide electric energy when discharging. One end of the LED module is connected to the power supply voltage through the inductor, and the other end is connected to the first end of the control switch through the LED lamp. The second end of the control switch is connected to the ground through the sampling resistor. The control switch controls the operation of the LED module during the constant current driving process. The freewheeling diode is connected in parallel with the LED module, and is used for freewheeling when the driving branch discharges.

[0007] The sampling input end of the control module is connected to the second end of the control switch. The control module collects the charging current and the action time of the control switch, and realizes the detection and judgment of LED driving fault according to the charging current and the action time of the control switch.

[0008] Preferably, the action time includes a closing time, which is the time from the closing of the control switch to the end of the time when the end voltage of the sampling resistor reaches the threshold voltage. The end voltage of the sampling resistor is obtained according to the charging current and the resistance value of the sampling resistor.

[0009] Preferably, the detection and judgment of the LED drive fault comprises: comparing the closing time with preset theoretical closing time to obtain a comparison result, and judging the LED drive fault type according to the comparison result.

[0010] Preferably, the preset theoretical closing time is at least two, and each of the preset theoretical closing time T on is calculated in the following way:

[0011]

[0012] Wherein, I max is the maximum charging current during charging, L is the inductance, V CC is the power supply voltage, and V LED is the terminal voltage of the LED.

[0013] Preferably, the preset theoretical closing time comprises a maximum theoretical closing time and an intermediate theoretical closing time.

[0014] When the comparison result is that the closing time is greater than the maximum theoretical closing time, the type of the LED drive fault is open circuit.

[0015] When the comparison result is that the closing time is equal to the intermediate theoretical closing time, the type of the LED drive fault is short circuit, and the number of short-circuited LEDs is consistent with the number of short circuits corresponding to the intermediate theoretical closing time.

[0016] Preferably, the detection and judgment of the LED drive fault further comprises: comparing the opening time with preset theoretical opening time to obtain a comparison result, and judging the LED drive fault type according to the comparison result.

[0017] When the comparison result is that the opening time is equal to the preset theoretical opening time, the type of the LED drive fault is short circuit, and the number of short-circuited LEDs is consistent with the number of short circuits corresponding to the preset theoretical opening time.

[0018] Preferably, the preset theoretical opening time is at least two, and correspondingly, the action time comprises an opening time, which refers to the time from the start of timing of opening the control switch to the end of timing when the discharge current on the drive branch is zero.

[0019] Each of the preset theoretical opening time T off is calculated in the following way:

[0020]

[0021] Wherein, I F is the discharge current during discharging, L is the inductance, V CC is the power supply voltage, and VLED V is the terminal voltage of the LED. d This refers to the voltage across the freewheeling diode. To achieve the above and other related objectives, the present invention also provides an LED driver fault detection method, applicable to the aforementioned LED driver fault detection circuit; the method includes at least the following steps:

[0022] A preset theoretical time is defined, which includes at least two theoretical closure times.

[0023] The action time of the control switch is obtained; the action time includes the closing time, which refers to the time from the start of closing the control switch to the end of the time when the terminal voltage of the sampling resistor reaches the threshold voltage. The terminal voltage of the sampling resistor is obtained based on the charging current and the resistance value of the sampling resistor.

[0024] The closing time is compared with the preset theoretical closing time to obtain the comparison result, and the LED driver fault information is determined based on the comparison result.

[0025] Preferably, the preset theoretical closure time includes the maximum theoretical closure time and the intermediate theoretical closure time;

[0026] When the comparison result shows that the closing time is greater than the maximum theoretical closing time, the type of LED driver fault is open circuit.

[0027] When the comparison result shows that the closing time is equal to a certain intermediate theoretical closing time, the type of LED driver fault is short circuit, and the number of short-circuited LEDs is consistent with the number of short circuits corresponding to a certain preset theoretical closing time.

[0028] Preferably, the theoretical time further includes at least two theoretical disconnection times; correspondingly, the action time also includes a disconnection time, which refers to the time from the start of timing when the control switch is disconnected until the discharge current is zero.

[0029] Preferably, the method further includes: comparing the disconnection time with a preset theoretical disconnection time to obtain a comparison result, and determining the LED driver fault type based on the comparison result;

[0030] When the comparison result shows that the disconnection time is equal to a certain preset theoretical disconnection time, the type of LED driver fault is short circuit, and the number of short-circuited LEDs is consistent with the number of short circuits corresponding to the certain preset theoretical disconnection time.

[0031] As described above, the LED driver fault detection circuit and method of the present invention have the following beneficial effects:

[0032] The application provides an LED driving fault detection circuit and method. The circuit directly processes the charging current and the action time of the control switch through a control module to realize detection and judgment of the LED driving fault, avoids additional detection branch on the original driving branch, influences the normal work of the original driving branch, and realizes effective fault detection and judgment of the LED in the normal working mode. BRIEF DESCRIPTION OF DRAWINGS

[0033] Figure 1 The figure shows the structure of the LED driving fault detection circuit of the application.

[0034] Figure 2 The figure shows the flow chart of the LED driving fault detection method of the application. DETAILED DESCRIPTION

[0035] The embodiments of the application are described below with reference to specific examples. Those skilled in the art can easily understand other advantages and effects of the application from the disclosure. The application can also be implemented or applied in different specific embodiments, and the details in the specification can be modified or changed based on different views and applications without departing from the spirit of the application.

[0036] Please refer to Figures 1-2 . It should be noted that the figures provided in the embodiments only schematically illustrate the basic concept of the application, and only the components related to the application are shown in the figures, not the number, shape and size of the components in actual implementation. The shape, number and proportion of the components in actual implementation can be randomly changed, and the layout of the components can be more complex.

[0037] The application removes the AD sampling part and increases the closing time and opening time of the control switch based on the prior art, so as to realize detection and judgment of the LED open circuit, short circuit and the number of short circuits in the normal working mode. Based on the technical concept, the application provides the following technical solutions, and the technical concept of the application is introduced in detail in combination with specific embodiments.

[0038] Circuit embodiment:

[0039] The schematic diagram of the LED driving fault detection circuit provided by the application is shown in Figure 1 , which includes a driving branch, a freewheeling diode and a control unit.

[0040] The driving branch comprises an LED module, a control switch S and a sampling resistor RS, one end of the LED module is connected with a power supply voltage, and the other end is connected with a first end of the control switch S; a second end of the control switch S is connected with the ground through the sampling resistor RS; the control switch S controls the LED module to work during the driving process;

[0041] The freewheeling diode DS is connected in parallel with the LED module, and is used for freewheeling when the driving branch is discharged;

[0042] The sampling input end of the control unit is connected with the second end of the control switch S, and is used for sampling the charging current and the action time of the control switch, and realizes the detection and judgment of the LED driving fault according to the charging current and the action time of the control switch.

[0043] The LED driving fault detection circuit of the present application directly utilizes the control unit to process the collected charging current and the action time of the control switch on the basis of the original driving branch, and realizes the detection and judgment of the LED driving fault, which not only improves the efficiency, but also realizes the detection and judgment under the normal working of the driving branch, and is more suitable.

[0044] In the embodiment of the present application, the LED module comprises an inductor L1 and at least two LED lamps, the inductor is connected in series with the at least two LED lamps, and the inductor is used for storing electric charge and providing electric energy when discharging.

[0045] In the embodiment of the present application, the LED module comprises three LED lamps, and in other embodiments, the number of LED lamps can also be 2, 5, 10, etc., which is determined according to the actual application.

[0046] It should be noted that: when the control switch is closed, the preset theoretical closing time T on of the control switch is calculated as follows:

[0047]

[0048] Wherein, I max is the maximum charging current during charging, L is the inductive reactance of the inductor, U l is the voltage of the inductor, and U l = V CC -V LED .

[0049] Since there are at least two LED lamps in the LED module, the preset theoretical closing time has at least three, one of which is the maximum theoretical closing time, and the others are intermediate theoretical closing times; the calculation formula of each preset theoretical closing time is as follows:

[0050]

[0051] Among them, I max V is the maximum charging current during charging, L is the inductive reactance of the inductor, and V is the maximum charging current during charging. CC V is the power supply voltage. LED This is the terminal voltage of the LED.

[0052] In this embodiment of the invention, there are three LED lights, and four corresponding preset theoretical closing times, wherein...

[0053] The maximum theoretical closing time refers to the time when all three LEDs are working normally.

[0054] The intermediate theoretical closing time refers to the time during which at least one LED experiences a short circuit fault. Specifically,

[0055] When an LED light experiences a short circuit, the theoretical closing time is:

[0056] When two LEDs experience a short circuit, the theoretical closing time is:

[0057] When three LEDs experience a short circuit, the theoretical closing time in the middle is:

[0058] In this embodiment of the invention, the action time of the control switch includes the closing time t. on The closing time t on This means that the timing starts from when the control switch is closed and ends when the voltage across the sampling resistor reaches the threshold voltage. The voltage across the sampling resistor is obtained based on the charging current and the resistance of the sampling resistor.

[0059] Specifically, the control module includes a first timer for timing the closing time t. on Timing is initiated, and charging current is collected. When the terminal voltage U of the sampling resistor calculated based on the charging current is greater than the threshold voltage V... th When the closing time is reached, the closing time is considered to be over. In other words, the closing time refers to the time from when the control switch is closed until the voltage U across the sampling resistor reaches the threshold voltage V. th The time period; the calculation method for the terminal voltage U of the sampling resistor is as follows:

[0060] U = IR

[0061] Where U is the terminal voltage of the sampling resistor RS, I is the charging current of the drive branch, and R is the resistance value of the sampling resistor RS.

[0062] In the present application, the detection and judgment of the LED driving fault comprises comparing the closing time with a preset theoretical closing time to obtain a comparison result, and judging the LED driving fault type according to the comparison result.

[0063] When the comparison result is that the closing time t on is greater than a preset maximum theoretical closing time , the LED driving fault type is open circuit, and N is a natural number less than or equal to the number of LEDs.

[0064] When the comparison result is that the closing time t on is equal to a certain preset theoretical closing time , the LED driving fault type is short circuit, and the number of short-circuited LEDs is consistent with the number of short circuits corresponding to the certain preset theoretical closing time.

[0065] Specifically, when , it indicates that the LED driving fault type is short circuit, and the number of short-circuited LEDs is one; when , it indicates that the LED driving fault type is short circuit, and the number of short-circuited LEDs is two; when , it indicates that the LED driving fault type is short circuit, and the number of short-circuited LEDs is three; otherwise, it is considered that no short circuit fault occurs; in addition, if the system appears open circuit (open circuit), since there is no closed loop, the terminal voltage on the sampling resistor RS cannot reach the threshold voltage, so that the closing time t on of the control switch S will be infinite; in actual application, if t on is obviously too large (i.e., t on is greater than the maximum theoretical closing time ), it can be determined as open circuit.

[0066] The present application can judge whether the LED lamp load is open circuit, short circuit, and the number of LEDs that are short-circuited according to the detected actual closing time.

[0067] In order to eliminate the misjudgment caused by the closing time, the control module also detects the opening time t off of the control switch S, that is, the control module further comprises a second timer for timing the opening time of the control switch S. Correspondingly, the action time further comprises the opening time, which refers to the timing from the start of opening the control switch to the end of the discharge current on the driving branch being zero.

[0068] Further, in order to detect and judge the LED driving fault type, the control module further pre-stores a theoretical opening time. It needs to be first explained that the calculation of the preset theoretical opening time T off of the control switch is as follows:

[0069]

[0070] wherein, I F is the discharge current during discharging, L is the inductive reactance, U x is the voltage of the inductor, U x = V CC + V LED + V d , V d is the voltage of the freewheeling diode.

[0071] Since there are at least two LED lamps in the LED module, the preset theoretical closing time has at least two, and each of the preset theoretical opening time T off is calculated by the following formula:

[0072]

[0073] wherein, I F is the discharge current during discharging, L is the inductive reactance, V CC is the voltage of the power supply, V LED is the terminal voltage of the LED, V d is the voltage of the freewheeling diode.

[0074] In the embodiment of the present application, there are three LED lamps, and the corresponding preset theoretical opening time has three, which are respectively:

[0075] When one LED lamp has a short circuit fault, the theoretical opening time is

[0076] When two LED lamps have a short circuit fault, the theoretical opening time is

[0077] When three LED lamps have a short circuit fault, the theoretical opening time is

[0078] Further, the present application further comprises comparing the opening time with the preset theoretical opening time to obtain a comparison result, and judging the LED driving fault type according to the comparison result. Specifically, when the comparison result is that the opening time is equal to a preset theoretical opening time, the LED driving fault type is short circuit, and the number of short-circuited LED is consistent with the number of short circuits corresponding to the preset theoretical opening time.

[0079] Specifically, when it is indicated that the LED driving fault type is short circuit, and the number of short-circuited LED is one; when it is indicated that the LED driving fault type is short circuit, and the number of short-circuited LED is two; when If the LED driving fault type is short circuit, and the number of short-circuited LEDs is three.

[0080] The present application can determine the type of LED driving fault by disconnecting time t off The present application can further determine whether the LED load is short-circuited and the number of short-circuited LEDs.

[0081] As can be seen from the above, the present application can increase the reliability of LED short-circuit fault determination by double determination of closing time T on and disconnecting time T off When the number of LEDs is determined, if T on decreases and T off increases, it can be determined that the LED is short-circuited; and according to the specific matching of T on , T off , the number of short-circuited LEDs can be determined. If the collected T on , T off do not match, a fault-tolerant mechanism can be introduced, such as re-detection or checking whether other devices in the system are problematic.

[0082] Method embodiment:

[0083] To achieve the above technical concept, the present application further provides an LED driving fault detection method as shown in Figure 2 , which is suitable for the LED driving fault detection circuit described above, and the method at least includes the following steps:

[0084] Presetting a theoretical time, the theoretical time including at least two theoretical closing times;

[0085] Obtaining the action time of the control switch; the action time including the closing time, the closing time being the time from the start of closing the control switch to the end of timing when the end voltage of the sampling resistor reaches the threshold voltage, the end voltage of the sampling resistor being obtained according to the charging current and the resistance value of the sampling resistor;

[0086] Comparing the closing time with the preset theoretical closing time to obtain a comparison result, and determining the LED driving fault information according to the comparison result.

[0087] In the embodiment of the present application, the preset theoretical closing time includes a maximum theoretical closing time and an intermediate theoretical closing time.

[0088] Correspondingly, the LED driving fault information determined according to the comparison includes:

[0089] When the comparison result is that the closing time is greater than the maximum theoretical closing time, the type of the LED driving fault is open circuit.

[0090] When the comparison result is that the closing time is equal to a certain intermediate theoretical closing time, the type of the LED drive fault is short circuit, and the number of the short-circuited LEDs is consistent with the number of short circuits corresponding to the certain preset theoretical closing time.

[0091] As a preferred embodiment of the present application, the method further comprises: comparing the opening time with a preset theoretical opening time to obtain a comparison result, and judging the type of the LED drive fault according to the comparison result. Correspondingly, the theoretical time further comprises at least two theoretical opening times, and the action time further comprises an opening time, which refers to the time from the start of the opening control switch to the end of the discharge current being zero.

[0092] Specifically, in the constant current working mode, the closing control switch S is detected, the first timer is started, when the terminal voltage U of the sampling resistor reaches the threshold voltage V th , the control switch S is opened, at this time, the first timer is turned off, and the closing time t on of the normal working is recorded. At the same time, the second timer is started when the control switch S is opened, and when the discharge current in the drive branch is reduced to zero, the second timer is turned off, and the opening time t off of the discharge continuous current working is recorded. If t on is reduced and t off is lengthened, it can be judged that the LED has a short circuit, and the number of the short-circuited LEDs can be determined.

[0093] If it is open circuit, the control switch S is closed, and the terminal voltage of the sampling resistor RS never reaches the threshold voltage. If it does not reach the threshold voltage within a certain time, it can be judged that it is open circuit.

[0094] In summary, the present application can detect the open and short circuit faults in real time when the constant current drive works, and can detect the number of the short-circuited LEDs, thereby facilitating the subsequent fault detection and maintenance. The double short circuit detection mechanism can increase the accuracy of fault detection, and the detection method can also avoid the frequency flicker of the LED lamp caused by turning off the constant current drive. Therefore, the present application effectively overcomes the various shortcomings in the prior art and has high industrial utilization value.

[0095] The above embodiments only exemplarily illustrate the principles and effects of the present application, and are not used to limit the present application. Any person skilled in the art can modify or change the above embodiments without departing from the spirit and scope of the present application. Therefore, all equivalent modifications or changes completed by those skilled in the art without departing from the spirit and technical thought of the present application should be covered by the claims of the present application.

Claims

1. An LED driver fault detection circuit, characterized by, The circuit comprises a driving branch, a freewheeling diode and a control module; The driving branch comprises an LED module, a control switch and a sampling resistor, the LED module comprises an inductor and at least two LED lamps, the inductor is connected in series with the at least two LED lamps, the inductor is used to store electric charge and provide electric energy when discharging; one end of the LED module is connected to a power supply voltage through the inductor, and the other end is connected to a first end of the control switch through the LED lamp; a second end of the control switch is connected to the ground through the sampling resistor; the control switch controls the operation of the LED module during constant current driving; the freewheeling diode is connected in parallel with the LED module and is used for freewheeling when the driving branch discharges; The sampling input end of the control module is connected to the second end of the control switch, the control module collects the charging current and the action time of the control switch, and realizes the detection and judgment of the LED driving fault according to the charging current and the action time of the control switch; The action time includes a closing time, the closing time is compared with a preset theoretical closing time to obtain a comparison result, and the type of the LED driving fault is judged according to the comparison result; The preset theoretical closing time includes a maximum theoretical closing time and at least two intermediate theoretical closing times, the maximum theoretical closing time is the closing time calculated when all the LED lamps in the LED module are normally working, and the intermediate theoretical closing time is the closing time calculated when a corresponding number of LED lamps in the LED module have a short circuit fault; When the comparison result is that the closing time is greater than the maximum theoretical closing time, the type of the LED driving fault is open circuit; When the comparison result is that the closing time is equal to an intermediate theoretical closing time, the type of the LED driving fault is short circuit, and the number of short-circuited LED lamps is consistent with the number of short-circuited LED lamps corresponding to the intermediate theoretical closing time. The closing time refers to the time counting from the closing of the control switch to the end of the time counting when the terminal voltage of the sampling resistor reaches the threshold voltage, and the terminal voltage of the sampling resistor is obtained according to the charging current and the resistance value of the sampling resistor.

2. The LED drive fault detection circuit of claim 1, wherein, The detection and judgment of the LED driving fault includes comparing the opening time with a preset theoretical opening time to obtain a comparison result, and judging the type of the LED driving fault according to the comparison result; When the comparison result is that the opening time is equal to the preset theoretical opening time, the type of the LED driving fault is short circuit, and the number of short-circuited LED lamps is consistent with the number of short-circuited LED lamps corresponding to the preset theoretical opening time.

3. The LED drive fault detection circuit of claim 2, wherein, The preset theoretical opening time is at least two, and correspondingly, the action time includes an opening time, the opening time refers to the time counting from the opening of the control switch to the end of the time counting when the discharging current on the driving branch is zero; wherein the preset theoretical opening time is the opening time calculated when a corresponding number of LED lamps in the LED module have a short circuit fault.

4. An LED driving fault detection method, applicable to the LED driving fault detection circuit of claim 1; characterized in that, The method comprises at least the following steps: Pre-set theoretical time, the theoretical time includes maximum theoretical closing time and at least two intermediate theoretical closing time; Obtain the action time of the control switch; the action time includes closing time, the closing time is from the closing control switch to the end of the sampling resistor voltage reaches the threshold voltage, the sampling resistor voltage is obtained according to the charging current and the resistance of the sampling resistor; The closing time is compared with the pre-set theoretical closing time to obtain the comparison result, and the LED drive fault information is judged according to the comparison result; When the comparison result is that the closing time is greater than the maximum theoretical closing time, the type of the LED drive fault is open circuit; When the comparison result is that the closing time is equal to a certain intermediate theoretical closing time, the type of the LED drive fault is short circuit, and the number of short-circuit LED lamps is consistent with the number of short-circuit LED lamps corresponding to the certain intermediate theoretical closing time.

5. The LED drive fault detection method of claim 4, wherein, The theoretical time also includes at least two theoretical opening times; correspondingly, the action time also includes opening time, the opening time is from the opening control switch to the end of the discharge current to zero.

6. The LED drive fault detection method of claim 5, wherein, The method further comprises: comparing the opening time with the pre-set theoretical opening time to obtain the comparison result, and judging the type of LED drive fault according to the comparison result; When the comparison result is that the opening time is equal to a certain pre-set theoretical opening time, the type of the LED drive fault is short circuit, and the number of short-circuit LED is consistent with the number of short-circuit corresponding to the certain pre-set theoretical opening time.

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