LED driving overload and short circuit protection circuit

Abstract

The utility model discloses an LED drive overload and short circuit protection circuit, which comprises a chip U1, an MOS tube Q1, an MOS tube Q2, a current detection unit, an amplification unit, a comparison unit and a charge and discharge unit, a drive signal is input into the input end of the drive chip U1, the output end totem of the chip U1 outputs a PWM signal to the G pole of the MOS tube Q1, the D pole of the MOS tube Q1 is electrically connected with an LED load, and the charge and discharge unit is electrically connected with the LED load. The S pole of the MOS tube Q1 is electrically connected with the input end of the current detection unit, the output end of the current detection unit is electrically connected with the input end of the amplification unit, and the output end of the amplification unit is electrically connected with the overcurrent protection end OCP of the chip U1 and the input end of the comparison unit. The output end of the comparison unit is electrically connected with the input end of the charging and discharging unit, one output end of the charging and discharging unit is electrically connected with the G pole of the MOS tube Q2, the other output end of the charging and discharging unit and the S pole of the MOS tube Q2 are respectively grounded, and the D pole of the MOS tube Q2 is electrically connected with the input end of the chip U1.

Description

Technical Field

[0001] The utility model relates to the technical field of LED driving, in particular to an LED driving overload and short circuit protection circuit. Background Art

[0002] Existing LED drivers generally lack overload protection, or their protection range is too wide and inaccurate. For example, protection requires an overload of at least 50%. When the LED voltage and driver voltage do not match, or when the LED power exceeds the LED driver power, the LED driver generates a sharp increase in heat, damaging the LED driver or reducing its service life. Furthermore, existing overload protection circuits respond slowly when the LED load shorts, requiring other MOSFETs to conduct to shut down the drive signal. This prevents instantaneous shutdown of the MOSFET connected to the LED load, resulting in significant short-circuit stress and potential damage to the MOSFET. Utility Model Content

[0003] The purpose of the present invention is to solve at least one of the technical problems existing in the prior art and to provide an LED driver overload and short circuit protection circuit that effectively protects the LED driver and the load.

[0004] According to an embodiment of the present utility model, the LED driver overload and short-circuit protection circuit includes a chip U1, a MOS transistor Q1, a MOS transistor Q2, a current detection unit, an amplifying unit, a comparing unit, and a charging and discharging unit. A driving signal is input to the input end of the driver chip U1, and the output end of the chip U1 totem outputs a PWM signal to the G pole of the MOS transistor Q1. The D pole of the MOS transistor Q1 is electrically connected to the LED load, and the S pole of the MOS transistor Q1 is electrically connected to the input end of the current detection unit. The output end of the current detection unit is electrically connected to the input end of the amplifying unit. The output end of the amplifying unit is electrically connected to the overcurrent protection terminal OCP of the chip U1 and the input end of the comparing unit respectively. The output end of the comparing unit is electrically connected to the input end of the charging and discharging unit. One output end of the charging and discharging unit is electrically connected to the G pole of the MOS transistor Q2. The other output end of the charging and discharging unit and the S pole of the MOS transistor Q2 are grounded respectively. The D pole of the MOS transistor Q2 is electrically connected to the input end of the chip U1. The drive signal outputs a PWM signal through the totem of chip U1 to turn on MOS tube Q1. The LED load current flows through the current detection unit to generate a current detection signal. The current detection signal is amplified by the amplifying unit and sent to the comparing unit for comparison with the reference signal of the comparing unit. When the LED load is normal, the amplified current detection signal is less than the reference signal, and the comparing unit outputs a low level, so that the MOS tube Q2 is not turned on, so that the drive signal is normally input to chip U1. When the LED load is overloaded, the amplified current detection signal is greater than the reference signal, and the comparing unit outputs a high level to charge the charging and discharging unit, so that the MOS tube Q2 is turned on, pulling down the drive signal, so that the chip U1 outputs a low level to turn off the MOS tube Q1. When the LED load is short-circuited, the short-circuit current is input to the overcurrent protection terminal OCP of chip U1 through the amplifying unit, triggering the overcurrent protection of chip U1. Chip U1 turns off the totem output, thereby turning off MOS tube Q1, which can instantly protect MOS tube Q1.

[0005] The LED driver overload and short-circuit protection circuit according to the embodiment of the utility model has at least the following beneficial effects: when overload protection is activated, the MOS transistor Q1 is turned off and no current detection signal is generated. The signal sent to the comparison unit through the amplification unit is substantially zero, and the comparison unit outputs a low level. At this time, the charge-discharge unit discharges. When the level drops to the turn-on level of the MOS transistor Q2, the MOS transistor Q2 is turned off, restoring the drive signal and turning on the MOS transistor Q1. In this way, the current of the LED load flows through the current detection unit again to generate a current detection signal. After amplification, the current is again compared with the reference signal of the comparison unit. If the current is greater than the reference voltage, the MOS transistor Q2 is turned off again. In this way, the LED load is intermittently lit and turned off, indicating an abnormal operation, thereby effectively protecting the LED load and the power supply itself. When the LED load recovers, the drive signal also returns to normal according to the above principle, and the LED will light up normally. When the LED load is short-circuited, the PWM signal will also be pulled low, effectively protecting the MOS tube Q1 from being burned out. Because the instantaneous change of the short circuit is very fast, when a short circuit occurs, the amplifier unit quickly responds to the amplified short-circuit current and feeds it back to the overcurrent protection terminal OCP of the chip U1, triggering the overcurrent protection of the chip, turning off the totem output, and quickly turning off the MOS tube Q1, which can instantly protect the MOS tube Q1 and turn off the output signal to protect the MOS tube Q1 before Q2 is turned on, so that the MOS tube Q1 does not have short-circuit impact stress. Long-term short circuit will not damage the MOS tube and will not generate heat. After the short circuit fault is restored, the drive signal also returns to normal and the LED lights up normally. It effectively protects LED lighting products, avoids heat damage caused by overcurrent, and extends the service life of LEDs; effectively protects LED drivers, avoids overheating and damage caused by overload, and extends the service life of LED drivers; effectively protects the driver's MOS tube from damage caused by output short circuit, reducing application risks and failure rates; effectively improves application risks, when overloaded, the LED lighting will light up and shut down at intervals, effectively prompting fault phenomena in the application, facilitating timely debugging and repair of faults.

[0006] Additional aspects and advantages of the present invention will be given in part in the following description and will become apparent from the following description or learned through practice of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The following is a further description of the specific embodiments of the present invention in conjunction with the accompanying drawings;

[0008] Figure 1 This is the schematic diagram of the LED driver overload and short-circuit protection circuit. DETAILED DESCRIPTION

[0009] This section will describe in detail the specific embodiments of the present invention. The preferred embodiments of the present invention are shown in the accompanying drawings. The purpose of the accompanying drawings is to supplement the description of the text part of the specification with graphics, so that people can intuitively and vividly understand each technical feature and overall technical solution of the present invention, but it cannot be understood as a limitation on the scope of protection of the present invention.

[0010] In the description of the present invention, it should be understood that descriptions involving orientations, such as up, down, front, back, left, right, etc., indicating orientations or positional relationships, are based on the orientations or positional relationships shown in the accompanying drawings. They are only for the convenience of describing the present invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, be constructed and operated in a specific orientation. Therefore, they cannot be understood as limitations on the present invention.

[0011] In the description of this utility model, "several" means one or more, "many" means more than two, "greater than," "less than," and "exceed" are understood to exclude the number itself, while "above," "below," and "within" are understood to include the number itself. The use of "first" and "second" in the description is solely for the purpose of distinguishing technical features and is not to be construed as indicating or implying relative importance, implicitly specifying the number of the indicated technical features, or implicitly specifying the order of the indicated technical features.

[0012] Reference Figure 1The utility model provides an LED driver overload and short-circuit protection circuit, comprising a chip U1, a MOS tube Q1, a MOS tube Q2, a current detection unit, an amplifying unit, a comparing unit, and a charging and discharging unit. A driving signal is input to the input end of the driver chip U1, and the output end of the chip U1 totem outputs a PWM signal to the G pole of the MOS tube Q1. The D pole of the MOS tube Q1 is electrically connected to the LED load, and the S pole of the MOS tube Q1 is electrically connected to the input end of the current detection unit. The output end of the current detection unit is electrically connected to the input end of the amplifying unit. The output end of the amplifying unit is respectively electrically connected to the overcurrent protection end OCP of the chip U1 and the input end of the comparing unit. The output end of the comparing unit is electrically connected to the input end of the charging and discharging unit. One output end of the charging and discharging unit is electrically connected to the G pole of the MOS tube Q2. The other output end of the charging and discharging unit and the S pole of the MOS tube Q2 are grounded respectively. The D pole of the MOS tube Q2 is electrically connected to the input end of the chip U1. The signal outputs a PWM signal through the totem of chip U1 to turn on MOS tube Q1. The LED load current flows through the current detection unit to generate a current detection signal. The current detection signal is amplified by the amplifying unit and sent to the comparing unit to be compared with the reference signal of the comparing unit. When the LED load is normal, the amplified current detection signal is less than the reference signal, and the comparing unit outputs a low level, so that the MOS tube Q2 is not turned on, so that the driving signal is normally input to chip U1. When the LED load is overloaded, the amplified current detection signal is greater than the reference signal, and the comparing unit outputs a high level to charge the charging and discharging unit, so that the MOS tube Q2 is turned on, pulling down the driving signal, so that the chip U1 outputs a low level to turn off the MOS tube Q1. When the LED load is short-circuited, the short-circuit current is input to the overcurrent protection terminal OCP of chip U1 through the amplifying unit, triggering the overcurrent protection of chip U1. Chip U1 turns off the totem output, thereby turning off MOS tube Q1, which can instantly protect MOS tube Q1.

[0013] After the overload protection, MOS tube Q1 is cut off and no current detection signal is generated. The signal sent to the comparison unit through the amplification unit is basically zero, and the comparison unit outputs a low level. At this time, the charge and discharge unit discharges. When the level drops to the turn-on level of MOS tube Q2, MOS tube Q2 is cut off, so that the drive signal is restored and MOS tube Q1 is turned on. In this way, the current of the LED load flows through the current detection unit again to generate a current detection signal. After amplification, it is compared with the reference signal of the comparison unit again. If it is greater than the reference voltage, MOS tube Q2 continues to be cut off. In this way, the LED load is lit intermittently to turn off, indicating abnormal operation and effectively protecting the LED load and the power supply itself. When the LED load recovers, the drive signal returns to normal according to the above principle, and the LED will light up normally. When the LED load is short-circuited, the PWM signal will also be pulled low, effectively protecting the MOS tube Q1 from being burned out. Because the instantaneous change of the short circuit is very fast, when a short circuit occurs, the amplifier unit quickly responds to the amplified short-circuit current and feeds it back to the overcurrent protection terminal OCP of the chip U1, triggering the overcurrent protection of the chip, turning off the totem output, and quickly turning off the MOS tube Q1, which can instantly protect the MOS tube Q1 and turn off the output signal to protect the MOS tube Q1 before Q2 is turned on, so that the MOS tube Q1 does not have short-circuit impact stress. Long-term short circuit will not damage the MOS tube and will not generate heat. After the short circuit fault is restored, the drive signal also returns to normal and the LED lights up normally. It effectively protects LED lighting products, avoids heat damage caused by overcurrent, and extends the service life of LEDs; effectively protects LED drivers, avoids overheating and damage caused by overload, and extends the service life of LED drivers; effectively protects the driver's MOS tube from damage caused by output short circuit, reducing application risks and failure rates; effectively improves application risks, when overloaded, the LED lighting will light up and shut down at intervals, effectively prompting fault phenomena in the application, facilitating timely debugging and repair of faults.

[0014] like Figure 1 As shown, one end of the resistor R1 inputs the driving signal, and the other end of the resistor R1 is electrically connected to one end of the resistor R2 and the input end of the chip U1. One end of the capacitor C4 and one end of the resistor R7 are electrically connected to the overcurrent protection terminal OCP of the chip U1, respectively. The other end of the capacitor C4 and the other end of the resistor R7 are grounded, respectively, to play a filtering role. It also includes a filtering unit 12, which includes a resistor R4 and a capacitor C1. One end of the resistor R4 is electrically connected to the S pole of the MOS tube Q1 and the input end of the current detection unit 11, respectively. The other end of the resistor R4 is electrically connected to the input of the amplifier unit 13 and one end of the capacitor C1, and the other end of the capacitor C1 is grounded. The current detection signal generated by the current flowing through the current detection unit 11 is sent to the amplifier unit 13 after filtering by the resistor R4 and the capacitor C2.

[0015] The amplification unit 13 includes an operational amplifier U2, a resistor R5, a resistor R8, a resistor R10 and a capacitor C5. The positive input terminal of the operational amplifier U2 is electrically connected to the other end of the resistor R4, the negative input terminal of the operational amplifier U2 is electrically connected to one end of the resistor R8, one end of the resistor R10 and one end of the capacitor C5, the other end of the resistor R10 is grounded, the other end of the resistor R8 and the other end of the capacitor C5 are electrically connected to the output terminal of the operational amplifier U2 and one end of the resistor R5, respectively, and the other end of the resistor R5 is electrically connected to the overcurrent protection terminal OCP of the chip U1. The comparison unit 14 includes an operational amplifier U3, a resistor R12, a resistor R13, a capacitor C6, and a capacitor C8. The positive input terminal of the operational amplifier U3 is electrically connected to the output terminal of the amplification unit 13 and one end of the capacitor C6, respectively. The negative input terminal of the operational amplifier U3 is electrically connected to one end of the capacitor C8, one end of the resistor R13, and one end of the resistor R12, respectively. The other end of the resistor R13 and the other end of the capacitor C8 are grounded, respectively. The other end of the resistor R12 is input with a DC voltage VCC. The output terminal of the operational amplifier U3 is electrically connected to the other end of the capacitor C6 and the input terminal of the charge and discharge unit 15, respectively.

[0016] The charge and discharge unit 15 includes a diode D1, a capacitor C7, and a resistor R11. The anode of the diode D1 is electrically connected to the output end of the comparison unit 14, and the cathode of the diode D1 is electrically connected to one end of the capacitor C7, one end of the resistor R11, and the G terminal of the MOS transistor Q2, respectively. The other end of the capacitor C7 and the other end of the resistor R11 are grounded, respectively. When the LED load is overloaded, the load current flows through resistor R6 to generate a current detection signal. After being filtered by filter unit 12, it is sent to operational amplifier U2. After being amplified by U2, it is sent to operational amplifier U3 for comparison. When the amplified current detection signal is greater than the reference signal, the output of operational amplifier U3 is high. The high level charges capacitor C7 through diode D1. When the voltage gradually rises to the turn-on voltage of MOS transistor Q2, MOS transistor Q2 turns on, causing the input drive signal to be pulled low. MOS transistor Q1 is turned off, shutting off the LED load, and effectively protecting the LED load and LED driver. When the overload protection is activated, no current flows through resistor R6, and the output of operational amplifier U3 is low. At this time, diode D1 is reversely cut off, and the voltage level of capacitor C7 slowly decreases. The time constant is determined by resistor R11 and capacitor C7. When the voltage level of capacitor C7 drops to the turn-on level of MOS transistor Q2, MOS transistor Q2 is turned off, and the drive signal is restored.

[0017] It is easy for those skilled in the art to understand that, under the premise of no conflict, the above preferred embodiments can be freely combined and superimposed.

[0018] The above are only preferred embodiments of the present invention and do not limit the patent scope of the present invention. All equivalent structural transformations made by using the contents of the present invention specification and drawings under the utility model concept, or directly or indirectly applied in other related technical fields are included in the patent protection scope of the present invention.

Claims

1. An LED driver overload and short circuit protection circuit, characterized in that: include: Chip U1, MOS tube Q1, MOS tube Q2, current detection unit (11), amplifier unit (13), comparison unit (14) and charge and discharge unit (15), the driving signal is input to the input end of the driving chip U1, the output end of the chip U1 totem outputs a PWM signal to the G pole of the MOS tube Q1, the D pole of the MOS tube Q1 is electrically connected to the LED load, the S pole of the MOS tube Q1 is electrically connected to the input end of the current detection unit (11), the output end of the current detection unit (11) is electrically connected to the amplifier unit (13), and the output end of the current detection unit (11) is electrically connected to the amplifier unit (13). ), the output end of the amplifying unit (13) is electrically connected to the overcurrent protection terminal OCP of the chip U1 and the input end of the comparing unit (14), the output end of the comparing unit (14) is electrically connected to the input end of the charging and discharging unit (15), one output end of the charging and discharging unit (15) is electrically connected to the G pole of the MOS tube Q2, the other output end of the charging and discharging unit (15) and the S pole of the MOS tube Q2 are grounded respectively, and the D pole of the MOS tube Q2 is electrically connected to the input end of the chip U1; The driving signal outputs a PWM signal through the chip U1 totem to turn on the MOS tube Q1. The LED load current flows through the current detection unit (11) to generate a current detection signal. The current detection signal is amplified by the amplifier unit (13) and sent to the comparison unit (14) to be compared with the reference signal of the comparison unit (14). When the LED load is normal, the amplified current detection signal is smaller than the reference signal, and the comparison unit (14) outputs a low level, so that the MOS tube Q2 is not turned on, so that the driving signal is normally input to the chip U1. When the LED load is overloaded, the amplified current detection signal is larger than the reference signal, and the comparison unit (14) outputs a high level to charge the charge and discharge unit (15), so that the MOS tube Q2 is turned on, the driving signal is pulled down, and the chip U1 outputs a low level to turn off the MOS tube Q1. When the LED load is short-circuited, the short-circuit current is input to the overcurrent protection terminal OCP of the chip U1 through the amplifier unit, triggering the overcurrent protection of the chip U1. The chip U1 turns off the totem output, thereby turning off the MOS tube Q1, which can instantly protect the MOS tube Q1.

2. The LED driver overload and short-circuit protection circuit according to claim 1, characterized in that: The filter unit (12) includes a resistor R4 and a capacitor C1, one end of the resistor R4 is electrically connected to the S pole of the MOS tube Q1 and the input end of the current detection unit (11), the other end of the resistor R4 is electrically connected to the input of the amplification unit (13) and one end of the capacitor C1, and the other end of the capacitor C1 is grounded.

3. The LED driver overload and short-circuit protection circuit according to claim 2, characterized in that: The current detection unit (11) comprises a resistor R6, one end of which is electrically connected to the S pole of the MOS tube Q1 and one end of the resistor R4, respectively, and the other end of the resistor R6 is grounded.

4. The LED driver overload and short-circuit protection circuit according to claim 3, characterized in that: The amplification unit (13) includes an operational amplifier U2, a resistor R5, a resistor R8, a resistor R10 and a capacitor C5, wherein the positive input terminal of the operational amplifier U2 is electrically connected to the other end of the resistor R4, the negative input terminal of the operational amplifier U2 is electrically connected to one end of the resistor R8, one end of the resistor R10 and one end of the capacitor C5, the other end of the resistor R10 is grounded, the other end of the resistor R8 and the other end of the capacitor C5 are electrically connected to the output terminal of the operational amplifier U2 and one end of the resistor R5 respectively, and the other end of the resistor R5 is electrically connected to the overcurrent protection terminal OCP of the chip U1.

5. The LED driver overload and short-circuit protection circuit according to claim 1, characterized in that: The comparison unit (14) includes an operational amplifier U3, a resistor R12, a resistor R13, a capacitor C6, and a capacitor C8. The positive input terminal of the operational amplifier U3 is electrically connected to the output terminal of the amplification unit (13) and one end of the capacitor C6, respectively. The negative input terminal of the operational amplifier U3 is electrically connected to one end of the capacitor C8, one end of the resistor R13, and one end of the resistor R12, respectively. The other end of the resistor R13 and the other end of the capacitor C8 are grounded, respectively. The other end of the resistor R12 inputs a DC voltage VCC, and the output terminal of the operational amplifier U3 is electrically connected to the other end of the capacitor C6 and the input terminal of the charge and discharge unit (15).

6. The LED driver overload and short-circuit protection circuit according to claim 1, characterized in that: The charge and discharge unit (15) comprises a diode D1, a capacitor C7 and a resistor R11, the anode of the diode D1 is electrically connected to the output end of the comparison unit (14), the cathode of the diode D1 is electrically connected to one end of the capacitor C7, one end of the resistor R11 and the G pole of the MOS tube Q2, respectively, and the other end of the capacitor C7 and the other end of the resistor R11 are grounded respectively.

7. The LED driver overload and short-circuit protection circuit according to claim 1, characterized in that: It includes a resistor R1 and a resistor R2. One end of the resistor R1 inputs a driving signal, and the other end of the resistor R1 is electrically connected to one end of the resistor R2 and the input end of the chip U1 respectively.

8. The LED driver overload and short circuit protection circuit according to claim 1, characterized in that: It includes a capacitor C4 and a resistor R7, one end of the capacitor C4 and one end of the resistor R7 are electrically connected to the overcurrent protection terminal OCP of the chip U1 respectively, and the other end of the capacitor C4 and the other end of the resistor R7 are grounded respectively.

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