LED fault detection circuit

Abstract

The LED fault detection circuit comprises a control circuit, a driving circuit, an MCU circuit, a sampling circuit and an LED, the control circuit is used for supplying power to the LED, the MCU circuit is used for controlling the on and off of an LED light source, when an LED load is lightened, the sampling circuit collects an output voltage value of the LED load in real time and sends the output voltage value to the MCU, and the MCU sends the output voltage value to the driving circuit. The MCU can judge the open / short circuit fault of the LED according to the output voltage value of the LED load. According to the LED fault detection circuit, a traditional MCU + linear chip + LED is omitted to achieve automobile lamp fault protection detection, a triode scheme is used for achieving constant current control, cost can be saved, the accuracy of LED open / short circuit fault detection can be improved, in addition, discrete devices such as triodes are used, the PCB layout is simple, and the EMC passing rate is improved.

Description

Technical Field

[0001] The utility model relates to the field of circuits, and in particular provides an LED fault detection circuit for detecting open / short circuit faults of LEDs. Background Art

[0002] With the development of society, new design concepts and pursuits are constantly emerging in automotive lighting design, and the requirements for automotive lighting protection are becoming increasingly stringent. Some lighting manufacturers require that all functions have open-circuit and short-circuit protection. Existing technology typically uses an "MCU + linear chip + LED" combination to implement automotive lighting fault protection detection. This has the following problems: 1. Conventional linear chips are expensive, and as current increases, the number of driver chips required increases, leading to higher overall lamp costs; 2. Conventional linear chips cannot detect single LED short-circuit faults; 3. Due to the large number of driver chips used, the first-time pass rate for EMC testing is reduced.

[0003] Therefore, proposing a new type of LED fault detection circuit to reduce the detection cost and improve the accuracy of LED open / short circuit fault detection has become an urgent problem to be solved. Utility Model Content

[0004] In view of this, the purpose of the present invention is to provide an LED fault detection circuit to solve the problems existing in the existing detection circuit.

[0005] The technical solution provided by the utility model is: an LED fault detection circuit, comprising: a control circuit, a drive circuit, an MCU circuit, a sampling circuit and an LED, wherein the drive circuit comprises a switch circuit module, a reference source module and a drive module, the switch circuit module comprises a PMOS tube RQ1, an NMOS tube RQ2, a resistor RR1, a resistor RR2, a resistor RR4, a resistor RR6 and a capacitor RC3, the source of the PMOS tube RQ1 is connected to the output end of the control circuit, the control circuit is used to output voltage, the drain of the PMOS tube RQ1 is connected to the positive electrode of the LED, the gate of the NMOS tube RQ2 is connected to the MCU circuit through the resistor RR4, the source of the NMOS tube RQ2 is grounded, the drain of the NMOS tube RQ2 is connected to the gate of the PMOS tube RQ1 through the resistor RR2, the two ends of the resistor RR1 and the capacitor RC3 are respectively connected to the gate and source of the PMOS tube RQ1, and the resistor RR6 is connected to the NMOS tube RQ2. The reference source module includes a resistor RR3, a resistor RR5 and a dual-switch diode RD1, one end of the resistor RR3 is connected to the drain of the PMOS tube RQ1, and the other end is connected to the positive electrode of the dual-switch diode RD1 and one end of the resistor RR5. The negative electrode of the dual-switch diode RD1 is grounded. The driving module includes a power transistor RQ3 and a sampling resistor RR7. The collector of the power transistor RQ3 is connected to the negative electrode of the LED. One end of the sampling resistor RR7 is connected to the emitter of the power transistor RQ3 and the other end is grounded. The base of the power transistor RQ3 is connected to the other end of the resistor RR5. The sampling circuit includes a resistor RR11, a resistor RR12 and a resistor RR13. One end of the resistor RR11 is connected to the negative electrode of the LED, and the other end is connected to one end of the resistor RR12. The other end of the resistor RR12 is grounded. One end of the resistor RR13 is connected between the resistor RR11 and the resistor RR12, and the other end is connected to the MCU circuit.

[0006] Preferably, the control circuit is a BUCK circuit.

[0007] Further preferably, the MCU circuit includes a low-dropout linear regulator LDO and an MCU connected to the low-dropout linear regulator LDO.

[0008] Further preferably, the LEDs are in multiple groups, the sampling circuit includes multiple sampling circuit branches, and the sampling circuit branches are connected to the LEDs in a one-to-one correspondence.

[0009] The LED fault detection circuit provided by the utility model comprises a control circuit for providing power to the LED, and an MCU circuit for controlling the on and off of the LED light source. When the LED load is lit, the output voltage value of the LED load is collected in real time by the sampling circuit and sent to the MCU. The MCU can determine whether the LED is on or short-circuited based on the output voltage value of the LED load.

[0010] The LED fault detection circuit provided by the utility model eliminates the traditional "MCU+linear chip+LED" to implement headlight fault protection detection, and uses a transistor solution to achieve constant current control, which not only saves costs but also improves the accuracy of LED open / short circuit fault detection. In addition, the use of discrete devices such as transistors simplifies the PCB layout and improves the EMC pass rate. BRIEF DESCRIPTION OF THE DRAWINGS

[0011] The present invention will be further described in detail below with reference to the accompanying drawings and embodiments:

[0012] Figure 1 This is a circuit block diagram of the LED fault detection circuit provided by the utility model;

[0013] Figure 2 This is the circuit diagram of the MCU circuit;

[0014] Figure 3 is a circuit diagram of a driving circuit;

[0015] Figure 4 This is the circuit diagram of the sampling circuit. DETAILED DESCRIPTION

[0016] The present invention will be further explained below in conjunction with specific implementation plans, but the present invention is not limited thereto.

[0017] like Figures 1 to 4As shown, the utility model provides an LED fault detection circuit, including: a control circuit, a drive circuit, an MCU circuit, a sampling circuit and an LED, wherein the drive circuit includes a switch circuit module, a reference source module and a drive module, the switch circuit module includes a PMOS tube RQ1, an NMOS tube RQ2, a resistor RR1, a resistor RR2, a resistor RR4, a resistor RR6 and a capacitor RC3, the source of the PMOS tube RQ1 is connected to the output end of the control circuit, the control circuit is used to output voltage, the drain of the PMOS tube RQ1 is connected to the positive electrode of the LED, the gate of the NMOS tube RQ2 is connected to the MCU circuit through the resistor RR4, the source of the NMOS tube RQ2 is grounded, the drain of the NMOS tube RQ2 is connected to the gate of the PMOS tube RQ1 through the resistor RR2, the two ends of the resistor RR1 and the capacitor RC3 are respectively connected to the gate and source of the PMOS tube RQ1, and the resistor RR6 is connected to the NMOS tube RQ 2, the reference source module includes a resistor RR3, a resistor RR5 and a dual-switch diode RD1, one end of the resistor RR3 is connected to the drain of the PMOS tube RQ1, and the other end is connected to the anode of the dual-switch diode RD1 and one end of the resistor RR5, and the cathode of the dual-switch diode RD1 is grounded. The driving module includes a power transistor RQ3 and a sampling resistor RR7, the collector of the power transistor RQ3 is connected to the cathode of the LED, one end of the sampling resistor RR7 is connected to the emitter of the power transistor RQ3, and the other end is grounded, and the base of the power transistor RQ3 is connected to the other end of the resistor RR5. The sampling circuit includes a resistor RR11, a resistor RR12 and a resistor RR13, one end of the resistor RR11 is connected to the cathode of the LED, and the other end is connected to one end of the resistor RR12, the other end of the resistor RR12 is grounded, one end of the resistor RR13 is connected between the resistor RR11 and the resistor RR12, and the other end is connected to the MCU circuit.

[0018] In this LED fault detection circuit, the control circuit is used to provide power to the LED, and the MCU circuit is used to control the on and off of the LED light source. When the LED load is lit, the output voltage value of the LED load is collected in real time through the sampling circuit and sent to the MCU. The MCU can determine whether the LED is on or short-circuit based on the output voltage value of the LED load.

[0019] As an improvement to the technical solution, the control circuit is a BUCK circuit.

[0020] As an improvement of the technical solution, the MCU circuit includes a low-voltage dropout linear regulator LDO and an MCU connected to the low-voltage dropout linear regulator LDO.

[0021] As an improvement of the technical solution, Figure 2As shown, the LEDs are in multiple groups, and the sampling circuit includes multiple sampling circuit branches, which are connected to the LEDs in a one-to-one correspondence.

[0022] Example

[0023] The LED fault detection circuit includes: a control circuit, a drive circuit, an MCU circuit, a sampling circuit and an LED.

[0024] Taking the reversing light as an example, the control circuit is a BUCK circuit, which mainly provides power for the reversing light.

[0025] The MCU circuit is composed of an LDO and an MCU. The LDO is used to provide a 5V voltage for the MCU. The MCU circuit is used to control the turning on and off of the LED light source. When the LED load is lit, the output voltage value of the LED load is collected in real time through the sampling circuit and sent to the MCU. The MCU can judge the current working status of the LED based on the output voltage value of the LED load. Among them, the MCU can select the S9KEAZ128AMLH model chip.

[0026] The driving circuit includes a switching circuit module, a reference source module, and a driving module. The switching circuit module includes a PMOS transistor RQ1, an NMOS transistor RQ2, a resistor RR1, a resistor RR2, a resistor RR4, a resistor RR6, and a capacitor RC3. The source of the PMOS transistor RQ1 is connected to the output terminal of the control circuit. The drain of the PMOS transistor RQ1 is connected to the positive electrode of the LED. The gate of the NMOS transistor RQ2 is connected to the MCU circuit through the resistor RR4. The source of the NMOS transistor RQ2 is grounded. The drain of the NMOS transistor RQ2 is connected to the gate of the PMOS transistor RQ1 through the resistor RR2. The two ends of the resistor RR1 and the capacitor RC3 are respectively connected to the gate and the source of the PMOS transistor RQ1. The resistor RR6 is connected between the gate and the source of the NMOS transistor RQ2. RR4 plays a role in current limiting and protection in the circuit. RR1 plays a role in current limiting and protection in the circuit. The capacitor RC3 is mainly used for filtering. The NMOS transistor will conduct only when Vg>Vs, and the PMOS transistor will conduct only when Vg<Vs. The two need to cooperate with each other to achieve the switching control of the LED by the MCU. When the high level of the MCU conducts RQ2, at this time, the source voltage of RQ1 is higher than the gate voltage, and RQ1 conducts normally, and the LED lights up normally. The reference source module includes a resistor RR3, a resistor RR5, and a dual-switch diode RD1. One end of the resistor RR3 is connected to the drain of the PMOS transistor RQ1, and the other end is connected to the positive electrode of the dual-switch diode RD1 and one end of the resistor RR5. The negative electrode of the dual-switch diode RD1 is grounded. The dual-switch diode RD1 mainly provides a forward biasing voltage for the emitter PN junction of the triode in the driving module, and its voltage to the ground is 1.4V. The driving module includes power triodes RQ3, RQ4, and sampling resistors RR7, RR9. The collectors of the power triodes RQ3 and RQ4 are respectively connected to the negative electrodes of two groups of LEDs. A linear driving scheme is adopted. The power triode RQ3 is used to achieve constant current control of the LED load. The sampling resistors RR7 and RR9 are used to adjust the current of the LED load. The bases of the triodes RQ3 and RQ4 are connected to the 1.4V of the dual-switch diode RD1 through the resistor RR5. The conduction condition of the triode is Vb>Ve. At this time, the voltage difference between the base and the emitter is 0.7V, so the emitter voltage is 0.7V. Then the voltage difference of the sampling resistor RR7 is 0.7V, and the resistance value of RR7 is 0.7V divided by the current flowing through the LED load; the sampling circuit includes resistors RR11 / RR12 / RR13 / RR14 / RR15 / RR16. Resistors RR11 / RR12 and RR14 / RR16 act as voltage dividers, while resistors RR13 and RR15 act as current limiting protection. The working principle is explained using the RL1 sampling circuit as an example: resistors RR11 and RR12 are connected in series, with one end of resistor RR11 connected to the LED cathode and one end connected to RR12. Resistors RR13 are connected to resistor RR12 and one end connected to the MCU. The current flowing through the LED can pass through the sampling circuit. Resistors RR11 and RR12 act as voltage dividers. The output voltage of the LED load is divided by the sampling circuit and then transmitted to the MCU. When an LED is open-circuited, the output voltage of the LED load is 0V. When an LED is short-circuited, the output voltage of the LED load increases compared to the output voltage during normal operation, and the voltage divider on the sampling circuit also increases. The MCU reads U. REV-FAULT1 It can be determined whether the LED load has an open or short circuit fault.

[0027] The following describes a complete fault detection process with the help of the accompanying drawings:

[0028] Take the RL1 sampling circuit as an example: the RL1 branch contains two LEDs. Assume that the voltage of a single LED is 2.5V to 3V, the output voltage of the DC-DC (control circuit) is 8.2V, and the voltage of RQ1 is 0.2V. At this time, U RL1 =U DC-DC -U RQ1 -U LED , that is, the theoretical output voltage range of LED when it is working normally is 2V≤U RL1 ≤3V. When an LED fails to open circuit, the theoretical output voltage U RL1 =0V, the MCU port detects an LED open circuit fault. When an LED short circuit fault occurs, the theoretical output voltage is 5V≤U RL1 ≤5.5V. According to the above calculation, the voltage threshold range of the LED in normal state can be set to 1.2V≤U RL1 ≤4V, the voltage threshold range for open circuit fault is set to 0V≤U RL1 <1V, the voltage threshold range for short circuit fault is set to U RL1 >4.8V.

[0029] Sampling circuit Assume RR11 = 91K, RR12 = 33K, and select the endpoint voltages of the voltage threshold range as 1V, 1.2V, 4V, 4.8V, and 5V. Then, U can be calculated. REV-FAULT1 (See Table 1). Table 1:

[0030] <![CDATA[U RL1 ]]> RR11 RR12 <![CDATA[U REV-FAULT1. ]]> 1V 91K 33K 1.33V 1.2V 91K 33K 1.28V 4V 91K 33K 1.06V 4.8V 91K 33K 0.32V 5V 91K 33K 0.27V

[0031] (Note: Based on the voltage values calculated in Table 1, software engineers need to convert the corresponding voltage values into digital quantities.)

[0032] At this time, MCU reads the real-time divided voltage U REV-FAULT1 , and then convert the voltage value into a real-time digital quantity, through which the working status of the LED load at this time can be determined.

[0033] The specific implementation methods of the present invention are written in a progressive manner, emphasizing the differences between the various implementation methods, and similar parts can be referenced to each other.

[0034] The embodiments of the present invention are described in detail above with reference to the accompanying drawings. However, the present invention is not limited to the above embodiments. Various changes can be made within the scope of knowledge possessed by ordinary technicians in this field without departing from the purpose of the present invention.

Claims

1. An LED fault detection circuit, characterized in that: include: A control circuit, a drive circuit, an MCU circuit, a sampling circuit, and an LED, wherein the drive circuit includes a switch circuit module, a reference source module, and a drive module; the switch circuit module includes a PMOS tube RQ1, an NMOS tube RQ2, a resistor RR1, a resistor RR2, a resistor RR4, a resistor RR6, and a capacitor RC3; the source of the PMOS tube RQ1 is connected to the output end of the control circuit; the control circuit is used to output a voltage; the drain of the PMOS tube RQ1 is connected to the positive electrode of the LED; the gate of the NMOS tube RQ2 is connected to the MCU circuit through the resistor RR4; the source of the NMOS tube RQ2 is grounded; the drain of the NMOS tube RQ2 is connected to the gate of the PMOS tube RQ1 through the resistor RR2; the two ends of the resistor RR1 and the capacitor RC3 are respectively connected to the gate and source of the PMOS tube RQ1; the resistor RR6 is connected between the gate and source of the NMOS tube RQ2; the base The quasi-source module includes a resistor RR3, a resistor RR5 and a dual-switch diode RD1. One end of the resistor RR3 is connected to the drain of the PMOS tube RQ1, and the other end is connected to the positive electrode of the dual-switch diode RD1 and one end of the resistor RR5. The negative electrode of the dual-switch diode RD1 is grounded. The driving module includes a power transistor RQ3 and a sampling resistor RR7. The collector of the power transistor RQ3 is connected to the negative electrode of the LED. One end of the sampling resistor RR7 is connected to the emitter of the power transistor RQ3 and the other end is grounded. The base of the power transistor RQ3 is connected to the other end of the resistor RR5. The sampling circuit includes a resistor RR11, a resistor RR12 and a resistor RR13. One end of the resistor RR11 is connected to the negative electrode of the LED, and the other end is connected to one end of the resistor RR12. The other end of the resistor RR12 is grounded. One end of the resistor RR13 is connected between the resistor RR11 and the resistor RR12, and the other end is connected to the MCU circuit.

2. The LED fault detection circuit according to claim 1, characterized in that: The control circuit is a BUCK circuit.

3. The LED fault detection circuit according to claim 1, wherein: The MCU circuit includes a low-dropout linear regulator LDO and an MCU connected to the low-dropout linear regulator LDO.

4. The LED fault detection circuit according to claim 1, wherein: The LEDs are in multiple groups, and the sampling circuit includes multiple sampling circuit branches, which are connected to the LEDs in a one-to-one correspondence.

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