False trigger open circuit protection circuit applied to LED drive circuit

Abstract

The utility model discloses a false trigger open circuit protection circuit applied to an LED drive circuit, which detects input voltage through a control module, and controls forced grounding of an FLTS pin or release of the FLTS pin through a first switching device, thereby effectively solving the problem that starting of false trigger open circuit protection functions of LED drive circuits including but not limited to PT16976, NCV7691 and the like fails. According to the invention, the limitation on the forward voltage of the load LED string is relieved, and the problem that the application scene is limited because the load voltage is limited by the existing false triggering open circuit protection circuit and the power consumption of the system is increased is solved.

Description

Technical Field

[0001] The utility model relates to the technical field, and in particular to a false trigger open circuit protection circuit applied to an LED drive circuit. Background Art

[0002] For LED driver circuits such as PT16976 and NCV7691, the circuit itself has an open circuit protection function. When the input voltage is higher than the open circuit protection detection threshold voltage, once a branch of the output load is open, the output end of the entire circuit will be locked, and the FLT pin will output a high level. In the application of this type of driver circuit, as the input voltage increases at the moment of power on, if the forward voltage of the load LED is high, when the input voltage rises to the open circuit protection detection threshold voltage, the output circuit has not yet been turned on and no output current has been formed. At this time, the driver chip will mistakenly believe that the entire circuit is in an open circuit state, thereby locking the entire circuit and the circuit startup will fail.

[0003] In order to avoid circuit startup failure, the general solution is to limit the forward voltage of the output load LED so that the load voltage is lower than the open circuit protection detection threshold voltage. This ensures that there is enough current in the output circuit before the input voltage reaches the open circuit detection threshold voltage, thereby avoiding false triggering of the open circuit protection function.

[0004] This solution limits the load voltage, increases the power consumption of the system, and thus limits the application scenarios. Utility Model Content

[0005] In response to the problems raised by the above-mentioned background technology, the purpose of the utility model is to provide a falsely triggered open-circuit protection circuit applied to an LED driving circuit, which detects the input voltage through a control module, and controls the forced grounding or release of the FLTS pin through a first switching device, thereby effectively solving the problem of failure to start the falsely triggered open-circuit protection function of LED driving circuits including but not limited to PT16976, NCV7691, etc., and removes the restriction on the forward voltage of the load LED string, thereby solving the problem that the existing falsely triggered open-circuit protection circuit limits the load voltage and increases the power consumption of the system, thereby limiting the application scenarios.

[0006] The utility model is realized by the following technical solutions:

[0007] A false trigger open circuit protection circuit applied to an LED drive circuit, comprising:

[0008] A control module and a first switching device;

[0009] The control module is connected to the input end of the first switch device, and the LED driving circuit is connected to the output end of the first switch device;

[0010] Wherein, the control module is used to detect the input voltage in real time and control the first switch device to be turned on and off;

[0011] When the control module detects that the input voltage is lower than the load LED conduction voltage, the first switch device is in the on state, and at this time, the switch protection function and the alarm output function of the LED drive circuit are shielded;

[0012] When the control module detects that the input voltage is higher than the load LED conduction voltage, the first switch device is in a cut-off state. At this time, the switch protection function and the alarm output function of the LED drive circuit work normally.

[0013] In the above technical solution, a control module and a first switching device are added before the LED driving circuit. The control module is used to detect the input voltage in real time. When the control module detects that the input voltage is lower than the load LED turn-on voltage, a control signal is sent to the first switching device to turn on the first switching device. When the first switching device is in the on state, the FLTS pin is equivalent to being directly connected to GND. At this time, regardless of whether there is voltage on the FLTS pin, it will be forced to be set to a low level. At this time, the switch protection function and alarm output function of the LED driving circuit are shielded, so that the driving circuit can operate normally.

[0014] When the control module detects that the input voltage is higher than the load LED conduction voltage, it sends a control signal to the first switching device to cut off the first switching device. When the first switching device is in the cut-off state, the FLTS pin is released, and the switch protection function and alarm output function of the LED drive circuit return to normal.

[0015] In an optional embodiment, the control module includes a detection network and a second switch device, the detection network is connected to the second switch device, and the second switch device is connected to the first switch device.

[0016] In an optional embodiment, the second switch device is a MOS transistor Q3, and a gate of the MOS transistor Q3 is connected to an intermediate node between the resistor R12 and the resistor R13.

[0017] In an optional embodiment, the detection network includes a resistor R12 and a resistor R13, the resistor R12 and the resistor R13 are connected in series, the resistor R12 is used to receive an input voltage, and the resistor R13 is grounded.

[0018] In an optional embodiment, the drain of the MOS tube Q3 is further connected to a resistor R14, one end of the resistor R14 is connected to the drain of the MOS tube Q3, and the other end is connected to the VIN port.

[0019] In an optional embodiment, the first switch device is a MOS transistor Q4, and the gate of the MOS transistor Q4 is connected to the middle node between the resistor R14 and the drain of the MOS transistor Q3. In an optional embodiment, the LED driving circuit includes a PT16976 driving chip or a NCV7691 driving chip.

[0020] In an optional embodiment, the PT16976 driver chip includes a VS pin, a PWM pin, a FLTS pin, an NTC pin, a GND pin, a FB pin, a BASE pin and a SC pin;

[0021] Wherein, the output end of the first switching device is connected to the FLTS pin.

[0022] In an optional embodiment, a capacitor C8 is further provided between the output end of the first switch device and the FLTS pin.

[0023] In an optional embodiment, the first switching device is a field effect transistor or a triode.

[0024] Compared with the prior art, the utility model has the following advantages and beneficial effects:

[0025] The input voltage is detected by the control module, and the forced grounding or releasing of the FLTS pin is controlled by the first switch device, thereby effectively solving the problem of failure to start the false triggering open circuit protection function of LED driving circuits including but not limited to PT16976, NCV7691, etc., and removing the restriction on the forward voltage of the load LED string, solving the problem that the existing false triggering open circuit protection circuit limits the load voltage and increases the power consumption of the system, thereby limiting the application scenarios. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] The drawings described herein are used to provide a further understanding of the embodiments of the present utility model, constitute a part of this application, and do not constitute a limitation of the embodiments of the present utility model. In the drawings:

[0027] Figure 1 A schematic diagram of the principle of a false trigger open circuit protection circuit applied to an LED drive circuit provided by an embodiment of the utility model;

[0028] Figure 2 A working principle diagram of a false trigger open circuit protection circuit provided in an embodiment of the utility model. DETAILED DESCRIPTION

[0029] In order to make the purpose, technical solutions and advantages of the utility model more clearly understood, the utility model is described in detail in an optional embodiment in combination with the embodiments and drawings below. The schematic implementation mode of the utility model and its description are only used to explain the utility model and are not intended to limit the utility model.

[0030] Example 1

[0031] This embodiment 1 provides a false trigger open circuit protection circuit applied to an LED driving circuit, such as Figure 1 As shown, a false trigger open circuit protection circuit applied to an LED driving circuit comprises:

[0032] A control module and a first switching device;

[0033] The control module is connected to the input end of the first switch device, and the LED driving circuit is connected to the output end of the first switch device;

[0034] Wherein, the control module is used to detect the input voltage in real time and control the first switch device to be turned on and off;

[0035] When the control module detects that the input voltage is lower than the load LED conduction voltage, the first switch device is in the on state, and at this time, the switch protection function and the alarm output function of the LED drive circuit are shielded;

[0036] When the control module detects that the input voltage is higher than the load LED conduction voltage, the first switch device is in a cut-off state. At this time, the switch protection function and the alarm output function of the LED drive circuit work normally.

[0037] It should be noted that for LED drive circuits such as PT16976 and NCV7691, the circuit itself has an open circuit protection function. When the input voltage is higher than the open circuit protection detection threshold voltage, once a branch of the output load is open, the output end of the entire circuit will be locked, and the FLT pin will output a high level. In the application of this type of drive circuit, as the input voltage increases at the moment of power on, if the forward voltage of the load LED is high, when the input voltage rises to the open circuit protection detection threshold voltage, the output circuit has not yet been turned on and no output current has been formed. At this time, the driver chip will mistakenly believe that the entire circuit is in an open circuit state, thereby locking the entire circuit and the circuit startup will fail.

[0038] To address this problem, the utility model proposes a falsely triggered open circuit protection circuit for an LED driving circuit. A control module and a first switching device are added before the LED driving circuit. The control module is used to detect the input voltage in real time. When the control module detects that the input voltage is lower than the load LED conduction voltage, a control signal is sent to the first switching device to turn on the first switching device. When the first switching device is in the on state, the FLTS pin is equivalent to being directly connected to GND. At this time, regardless of whether there is voltage on the FLTS pin, it will be forced to be set to a low level. At this time, the switch protection function and the alarm output function of the LED driving circuit are shielded, so that the driving circuit can operate normally.

[0039] When the control module detects that the input voltage is higher than the load LED conduction voltage, it sends a control signal to the first switching device to cut off the first switching device. When the first switching device is in the cut-off state, the FLTS pin is released, and the switch protection function and alarm output function of the LED drive circuit return to normal.

[0040] In an optional embodiment, the control module includes a detection network and a second switch device, the detection network is connected to the second switch device, and the second switch device is connected to the first switch device.

[0041] It should be noted that the detection network is used to detect the input voltage in real time and control the opening and closing of the second switch device. When the detection network detects that the input voltage is lower than the load LED conduction voltage, the second switch device is controlled to be in the cut-off state, thereby making the first switch device in the conduction state; when the detection network detects that the input voltage is higher than the load LED conduction voltage, the second switch device is controlled to be in the conduction state, thereby making the first switch device in the cut-off state.

[0042] In an optional embodiment, the second switch device is a MOS transistor Q3, and a gate of the MOS transistor Q3 is connected to an intermediate node between the resistor R12 and the resistor R13.

[0043] In an optional embodiment, the detection network includes a resistor R12 and a resistor R13, the resistor R12 and the resistor R13 are connected in series, the resistor R12 is used to receive an input voltage, and the resistor R13 is grounded.

[0044] It should be noted that if Figure 1 As shown, the detection network composed of resistor R12 and resistor R13 can detect the input voltage in real time, compare the input voltage with the load LED conduction voltage, and control the opening and closing of the MOS tube Q3.

[0045] In an optional embodiment, the drain of the MOS tube Q3 is further connected to a resistor R14, one end of the resistor R14 is connected to the drain of the MOS tube Q3, and the other end is connected to the VIN port.

[0046] In an optional embodiment, the first switch device is a MOS transistor Q4, and a gate of the MOS transistor Q4 is connected to an intermediate node between the resistor R14 and a drain of the MOS transistor Q3.

[0047] It should be noted that when the MOS tube Q4 is in the on state, the FLTS pin is equivalent to being directly grounded. At this time, regardless of whether there is voltage on the FLTS pin, it will be forced to be set to a low level. At this time, the LED driver circuit with an open circuit protection function can be solved. When the input voltage is higher than the open circuit protection detection threshold voltage, once a branch of the output load is open, the output end of the entire circuit will be locked, the FLT pin will output a high level, and the driver circuit will fail to start. Conversely, when the MOS tube Q4 is in the off state, the FLTS pin is in the open state. If a fault occurs, the FLTS pin will be set to a high level. At this time, the open circuit protection function of the driver circuit is activated.

[0048] In an optional embodiment, the LED driving circuit includes a PT16976 driving chip or a NCV7691 driving chip.

[0049] In an optional embodiment, the PT16976 driver chip includes a VS pin, a PWM pin, a FLTS pin, an NTC pin, a GND pin, a FB pin, a BASE pin and a SC pin;

[0050] Wherein, the output end of the first switching device is connected to the FLTS pin.

[0051] It should be noted that the PT16976 driver chip and the NCV7691 driver chip are chips with open circuit protection functions, which can be set through the chip's own internal logic circuit. When the output load is in an open circuit state, the FLTS pin will be set to a high level to achieve an alarm output, and the entire circuit will stop working to achieve the protection function. In this application, when the protection function is prone to false triggering during the power-on process, the FLTS pin is forced to a low level, and the protection function fails at this time, and the entire circuit can start working normally.

[0052] In an optional embodiment, a capacitor C8 is further provided between the output end of the first switch device and the FLTS pin.

[0053] In an optional embodiment, the first switch device is a field effect transistor or a triode. In this embodiment, the second switch device includes but is not limited to a field effect transistor or a triode, and also includes any other switch device with switch characteristics.

[0054] In an optional embodiment, the LED driving circuit includes a PT16976 driving chip or a NCV7691 driving chip.

[0055] Figure 2 The working principle diagram of the false trigger open circuit protection circuit provided by the embodiment of the utility model is as follows: Figure 2 As shown, the specific working process of the false trigger open circuit protection circuit applied to the LED driving circuit provided by the utility model is as follows:

[0056] During the use of a drive circuit with built-in protection function, it is hoped that the output load forward voltage limit can be reached, and it can be powered on and started normally when the output load voltage is higher than the open circuit protection detection threshold voltage. Based on this, a false trigger open circuit protection circuit applied to an LED drive circuit forcibly grounds the FLTS pin of the driver chip in the drive circuit before the input voltage rises to the load LED conduction voltage. According to the logic function of the driver chip PT16976 or the driver chip NCV7691, the open circuit protection function is shielded at this time, and the drive circuit can start normally. When the input voltage rises to the load LED conduction voltage or the voltage is stable, the FLTS pin is released, the open circuit protection function returns to normal, and the FLTS pin fault alarm output function returns to normal.

[0057] In the utility model, the input voltage is detected by the control module, and the forced grounding or release of the FLTS pin is controlled by the first switch device, thereby effectively solving the problem of the failure to start the open circuit protection function caused by the false triggering of LED driving circuits including but not limited to PT16976, NCV7691, etc., and removing the limitation on the forward voltage of the load LED string.

[0058] The specific implementation methods described above further illustrate the purpose, technical solutions and beneficial effects of the utility model in detail. It should be understood that the above description is only the specific implementation method of the utility model and is not used to limit the protection scope of the utility model. Any modifications, equivalent substitutions, improvements, etc. made within the spirit and principles of the utility model should be included in the protection scope of the utility model.

Claims

1. A false trigger open circuit protection circuit applied to an LED drive circuit, characterized in that: include: A control module and a first switching device; The control module is connected to the input end of the first switch device, and the LED driving circuit is connected to the output end of the first switch device; Wherein, the control module is used to detect the input voltage in real time and control the first switch device to be turned on and off; When the control module detects that the input voltage is lower than the load LED conduction voltage, the first switch device is in the on state, and at this time, the switch protection function and the alarm output function of the LED drive circuit are shielded; When the control module detects that the input voltage is higher than the load LED conduction voltage, the first switch device is in a cut-off state, and at this time, the switch protection function and the alarm output function of the LED drive circuit work normally; The control module includes a detection network and a second switch device, the detection network is connected to the second switch device, and the second switch device is connected to the first switch device; The detection network includes a resistor R12 and a resistor R13, wherein the resistor R12 is connected in series with the resistor R13, the resistor R12 is used to receive an input voltage, and the resistor R13 is grounded; The second switch device is a MOS transistor Q3, and the gate of the MOS transistor Q3 is connected to the middle node between the resistor R12 and the resistor R13; The drain of the MOS tube Q3 is also connected to a resistor R14 , one end of the resistor R14 is connected to the drain of the MOS tube Q3 , and the other end of the resistor R14 is connected to the VIN port.

2. The false trigger open circuit protection circuit applied to the LED driving circuit according to claim 1, characterized in that: The first switch device is a MOS transistor Q4 , and a gate of the MOS transistor Q4 is connected to an intermediate node between the resistor R14 and a drain of the MOS transistor Q3 .

3. The false trigger open circuit protection circuit for LED driving circuit according to claim 1, characterized in that: The LED driving circuit includes a PT16976 driving chip or a NCV7691 driving chip.

4. The false trigger open circuit protection circuit for LED driving circuit according to claim 3, characterized in that: The PT16976 driver chip includes a VS pin, a PWM pin, a FLTS pin, an NTC pin, a GND pin, a FB pin, a BASE pin and a SC pin; Wherein, the output end of the first switching device is connected to the FLTS pin.

5. The false trigger open circuit protection circuit applied to the LED driving circuit according to claim 4, characterized in that: A capacitor C8 is further provided between the output end of the first switch device and the FLTS pin.

6. The false trigger open circuit protection circuit applied to the LED driving circuit according to claim 1, characterized in that: The first switch device is a field effect transistor or a triode.

Images