A control protection circuit for an LED

Abstract

The utility model provides a kind of LED control protection circuit, it includes multiple LED control protection module, each LED control protection module includes LED control unit and LED failure protection unit, LED control unit includes LED1 and switching device T2, the anode of LED1 is connected with node VF2, its cathode is connected with node VF5;Node VF2 is connected with power supply V1;The first connecting end of switching device T2 is connected with node VF5, its second connecting end is grounded, its control end is connected with node A;Node A is connected with power supply V1;The input end of LED failure protection unit is connected with node VF2, its output end is connected with node A, when LED failure protection unit detects the short circuit of LED1 by the voltage of node VF5, LED failure protection unit changes the voltage of node A to control switching device T2 to be turned off.Compared with prior art, the utility model uses the same power line bundle to supply power for multiple LED loads in parallel, which can realize that single or multiple failure does not affect power supply system and other load work.

Description

[Technical Field]

[0001] This utility model relates to the field of circuit design technology, and in particular to a control and protection circuit for LEDs. [Background Technology]

[0002] With the development of automobiles, the requirements for white light visibility are getting higher and higher, and more and more white light modules are being used in cars. For products with multiple monochrome lamps directly connected to the battery or high-side switch output, they need to be independent. The failure of LEDs should not cause power supply failure or failure of other LEDs, or increase leakage current.

[0003] Please refer to Figure 1 As shown, this is a circuit diagram of the current technical solution, which directly connects the power supply to a multi-LED load. However, Figure 1 The existing technical solution shown has the following problems:

[0004] 1) In Figure 1 In the existing technical solution shown, a short circuit in the LED will cause the upstream DC-to-DC converter to enter overcurrent protection, such as hiccup or shutdown mode;

[0005] 2) In Figure 1 In the existing technical solutions shown, a short circuit in the LED can cause other ECUs (Electronic Control Units) to enter an abnormal working state, such as not lighting up or flashing.

[0006] Therefore, it is necessary to propose a new technical solution to address the above problems. [Utility Model Content]

[0007] One of the objectives of this utility model is to provide a control and protection circuit for LEDs, which uses the same power supply harness to power multiple parallel LED loads, and can ensure that the failure of a single or multiple LEDs will not affect the operation of the power supply system and other loads.

[0008] According to one aspect of this utility model, an LED control and protection circuit is provided, comprising multiple LED control and protection modules connected in parallel. Each LED control and protection module includes an LED control unit and an LED failure protection unit. The LED control unit includes an LED1 and a switching device T2. The positive terminal of the LED1 is connected to node VF2, and its negative terminal is connected to node VF5. Node VF2 is connected to a power supply V1. The first connection terminal of the switching device T2 is connected to node VF5, its second connection terminal is grounded, and its control terminal is connected to node A. Node A is connected to the power supply V1. The input terminal of the LED failure protection unit is connected to node VF2, and its output terminal is connected to node A. When the LED failure protection unit detects a short circuit in the LED1 through the voltage of node VF5, the LED failure protection unit changes the voltage of node A to control the switching device T2 to turn off.

[0009] Compared with the prior art, this utility model uses the same power supply harness to power multiple parallel LED loads, which can ensure that the failure of a single or multiple LED loads will not affect the operation of the power supply system and other loads. [Attached Image Description]

[0010] To more clearly illustrate the technical solutions of the embodiments of this utility model, the drawings used in the description of the embodiments will be briefly introduced below. Obviously, the drawings described below are only some embodiments of this utility model. For those skilled in the art, other drawings can be obtained based on these drawings without creative effort. Among them:

[0011] Figure 1 This is a circuit diagram of the current technical solution;

[0012] Figure 2 This is a circuit diagram of the LED control and protection circuit in one embodiment of the present invention;

[0013] Figure 3 As shown in one embodiment of the present invention Figure 2 The circuit diagram of the LED control and protection module 110 shown is shown.

Detailed Implementation Methods

[0014] To make the above-mentioned objectives, features and advantages of this utility model more apparent and understandable, the utility model will be further described in detail below with reference to the accompanying drawings and specific embodiments.

[0015] The term "an embodiment" or "embodiment" as used herein refers to a specific feature, structure, or characteristic that may be included in at least one implementation of the present invention. The phrase "in one embodiment" appearing in different places in this specification does not necessarily refer to the same embodiment, nor is it a single or selective embodiment that excludes other embodiments. Unless otherwise specified, the terms coupling, connection, linking, and interconnection used herein to indicate electrical connection mean direct or indirect connection. For example, A being connected to B includes both a direct electrical connection between A and B and a connection between A and B via electrical components or circuits.

[0016] In the description of this utility model, it should be understood that the terms "upper", "lower", "front", "back", "positive", "back", "left", "right", "vertical", "horizontal", "top", "bottom", "inner", and "outer" indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this utility model and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this utility model.

[0017] Please refer to Figure 2 As shown, it is a circuit diagram of the LED control and protection circuit in one embodiment of the present invention. Figure 2 The LED control and protection circuit 100 shown includes four LED control and protection modules connected in parallel: LED control and protection module 110, LED control and protection module 120, LED control and protection module 130, and LED control and protection module 140. The circuit structures of LED control and protection modules 110, 120, 130, and 140 are identical or consistent. In other embodiments, the LED control and protection circuit 100 may include two, three, five, or more LED control and protection modules. That is, the LED control and protection circuit provided by this utility model includes multiple LED control and protection modules connected in parallel, and the circuit structures of these multiple LED control and protection modules are identical or consistent.

[0018] Please refer to Figure 3 As shown, this is one embodiment of the present invention. Figure 2 The circuit diagram of the LED control and protection module 110 shown is shown. Figure 3 The LED control and protection module shown includes an LED control unit 112 and an LED failure protection unit 114.

[0019] The LED control unit 112 includes an LED1 and a switching device T2. The positive terminal of LED1 is connected to node VF2, and its negative terminal is connected to node VF5. Node VF2 is connected to the power supply V1. The first connection terminal of the switching device T2 is connected to node VF5, its second connection terminal is grounded, and its control terminal is connected to node A. Node A is connected to the power supply V1. The input terminal of the LED failure protection unit 114 is connected to node VF2, and its output terminal is connected to node A. When the LED failure protection unit 114 detects a short circuit in LED1 through the voltage of node VF5, it changes the voltage of node A to control the switching device T2 to turn off. Furthermore, when the LED failure protection unit 114 detects that LED1 is working normally or open-circuited through the voltage of node VF5, it does not change the voltage of node A. When LED1 is working normally, the switching device T2 is turned on; when LED1 is open-circuited, the switching device T2 is turned off.

[0020] exist Figure 3 In the specific embodiment shown, the LED failure protection unit 114 includes resistors R2, R4, R6, R7, R8, and R11, diode D1, switching device T1, switching device T3, and switching device T4. In this configuration, the first connection terminal of switching device T1 is connected to node VF3, its control terminal is connected to node VF2 via resistor R2, and its second connection terminal is connected to node VF4; node VF3 is connected to power supply V1; the first connection terminal of switching device T4 is connected to power supply V1 via resistor R6, its control terminal is connected to node B via resistor R8, and its second connection terminal is connected to node VF1; one end of resistor R4 is connected to node VF4, and the other end is connected to node C; one end of resistor R7 is connected to node VF1, and the other end is connected to node C; one end of resistor R11 is connected to node C, and the other end is grounded; the cathode of diode D1 is connected to node B, and its anode is connected to node A; the first connection terminal of switching device T3 is connected to node B, its control terminal is connected to node C, and its second connection terminal is grounded.

[0021] When the LED failure protection unit 114 detects that LED1 is working normally or open-circuited through the voltage of node VF5, switching devices T1, T4 and T3 are all turned off; when the LED failure protection unit 114 detects that LED1 is short-circuited through the voltage of node VF5, switching devices T1, T4 and T3 are all turned on.

[0022] exist Figure 3In the specific embodiment shown, the LED failure protection unit 114 further includes a Zener diode SD1. The positive terminal of the Zener diode SD1 is connected to node VF3, and its negative terminal is connected to the power supply V1. When the LED failure protection unit 114 detects that the LED1 is working normally or open-circuited through the voltage of node VF5, the Zener diode SD1 does not work. When the LED failure protection unit 114 detects that the LED1 is short-circuited through the voltage of node VF5, the Zener diode SD1 works.

[0023] exist Figure 3 In the specific embodiment shown, the LED control unit 112 further includes resistors R1, R3, R5, and R12. One end of resistor R3 is connected to the power supply V1, and the other end is connected to node VF2; one end of resistor R12 is connected to the power supply V1, and the other end is connected to node A; one end of resistor R1 is connected to node A, and the other end is connected to the control terminal of the switching device T2; one end of resistor R5 is connected to the control terminal of the switching device T2, and the other end is grounded.

[0024] exist Figure 3 In the specific embodiment shown, switching device T1 is a PNP transistor, and the first connection terminal, the second connection terminal, and the control terminal of switching device T1 are the emitter, collector, and base of the PNP transistor, respectively; switching device T2 is an NPN transistor, and the first connection terminal, the second connection terminal, and the control terminal of switching device T2 are the collector, emitter, and base of the NPN transistor, respectively; switching device T3 is an NPN transistor, and the first connection terminal, the second connection terminal, and the control terminal of switching device T3 are the collector, emitter, and base of the NPN transistor, respectively; switching device T4 is a PNP transistor, and the first connection terminal, the second connection terminal, and the control terminal of switching device T4 are the emitter, collector, and base of the PNP transistor, respectively.

[0025] To facilitate understanding of this utility model, the following is combined with... Figure 3 Detailed introduction Figure 2 The working principle of the control and protection circuit for the LED shown.

[0026] It should be noted that:

[0027] A.

[0028] 1) V1 is the output voltage VDCDC1 of the DC-DC module 200 provided by the client.

[0029] 2) LED1 is the load for the high-power ECUx.

[0030] 3) VF1, VF2, VF3, VF4, and VF5 are the test voltage points.

[0031] 4) In LED control unit 112:

[0032] ● The function of resistor R3 is to limit the current of LED1.

[0033] ● Resistor R12 serves to trigger the conduction of transistor T2 and also limits current.

[0034] ● The function of resistor R1 is to limit the base current of T2.

[0035] ● The function of resistor R5 is to prevent accidental activation of resistor T2.

[0036] 5) In LED failure protection unit 114:

[0037] ●The function of transistors T1, T2, and T3 is to switch the circuit on and off.

[0038] ● The function of diode D1 is to prevent backflow.

[0039] ●The function of Zener diode SD1 is to prevent T1 from conducting normally during operation;

[0040] ● The function of resistors R2, R4, R6, R7, R8, and R11 is to configure the operating point of the transistor;

[0041] B.

[0042] 1. The forward voltage of LED1 is Vled.

[0043] 2. The breakdown voltage of Zener diode SD1 is V_sd1.

[0044] 3. The forward voltage of diode D1 is Vd1.

[0045] 4. The PN junction voltage of transistor T1 is Vpn1, the saturation voltage is Vsat1, and the amplification factor is β1.

[0046] 5. The PN junction voltage of transistor T2 is Vpn2, the saturation voltage is Vsat2, and the amplification factor is β2.

[0047] 6. The PN junction voltage of transistor T3 is Vpn3, the saturation voltage is Vsat3, and the amplification factor is β3.

[0048] 7. The PN junction voltage of transistor T4 is Vpn4, the saturation voltage is Vsat4, and the amplification factor is β4.

[0049] ■ Principles of Normal Operation

[0050] 1. Design V1-(V_sd1+Vpn1)<Vled+Vsat2 or design the current Iled flowing through LED1, i.e. Iled*R3<V_sd1+Vpn1, that is, when powered on, T1 works in the cutoff (or off) state under this condition.

[0051] 2. It can be deduced that the base voltage of T3 is 0 potential due to the pull-down resistor R11, which makes T3 in the cut-off state;

[0052] 3. V1 flows through R6. Due to the cutoff of T3 and the reverse cutoff of diode D1, T4 operates in the cutoff state.

[0053] 4. Another path for V1 is through R12. Since T3 and T4 are cut off, the current can only flow through the path of R12, R5, R1 and T2, so that T2 obtains base current ib2, ib2=[(V1-Vpn2) / (R1+R12)-Vpn2 / R5], β2*ib2>>Iled, T2 enters saturation state (i.e. T2 is turned on), LED1 lights up, and the V1-R3-LED1-T2 path works normally;

[0054] ■ Protection Mechanism Principles under Abnormal Operating Conditions

[0055] ●LED open circuit failure

[0056] 1. The transistor is a current-controlled device, meaning T2 is operating in the cutoff state.

[0057] 2. Because the DC-DC voltage V1 flows through R3 without a path and is at a high level, T1 operates in the off state;

[0058] 3. After T1 is closed, the states of T3 / T4 are the same as those during normal operation, and the conclusion is that the operation is in the closed state;

[0059] 4. The total current is approximately Iopen = (V1 - Vpn2) / (R1 + R12). The current is controlled within the mA range and will not cause the power supply or other loads to malfunction.

[0060] ●LED short circuit failure

[0061] 1. When the LED is short-circuited, the voltages of VF2 / VF5 are close to Vsat2, with a voltage range between 0.1-0.3V, making V1-(V_sd1+Vpn1)>>Vsat2, ib1=[V1-(V_sd1+Vpn1)-Vsat2] / R2, β1*ib1>>Ic1, ic1=[V1-(Vsat1+V_sd1)-Vpn3] / R4, and T1 operates in saturation (i.e., conduction state).

[0062] 2. The path V1-T1-R4-T3 makes T3 conduct, Ib3=(VF4-Vpn3) / R4-Vpn3 / R11

[0063] 3. There is a path via path V1-R6-T4-T3. When T3 is turned on, T4 is turned on, where Ic4=β4*Ib4, Ib4=[V1-Ic4*R6-Vpn4-Vsat3] / R8, Ib3_Total=Ib3+Ic4-Vpn3 / R11, β3*Ib3_Total>>Ic3, and the current Ic3 is currently derived from the base current of T4;

[0064] 4. Through the analysis in step 2 and step 3, T3 and T4 operate in a saturated state, and the conduction of T4 will aggravate the saturated conduction of T3. The cathode voltage of D1 is Vsat3, which forms the path V1-R12-D1-T3. The anode voltage of D1 is Vd1_anthod=Vsat3+Vd1, and the selected Vd1_anthod<Vpn2, so T2 is cut off. The large current path V1-R3-T2 is turned off, which will not affect the power supply and other loads due to short circuit;

[0065] 5. Once a short-circuit failure occurs, the circuit will trigger protection, and cannot recover even if the failure is intermittent. The failure analysis is as stated in step 4: since T3 and T4 generate positive feedback after being triggered by the failure, T3 will not exit the saturated operation, which ensures that no large-current path exists, unless power is cycled or a new module is replaced.

[0066] In summary, the present utility model provides an LED control and protection circuit, which uses the same power harness to supply power to multiple parallel LED control and protection modules. When a single channel or multiple channels fail, the output of the power supply system will not be affected; when a single channel or multiple channels fail, the operation of other LED control and protection modules will not be affected, wherein the LED failures mainly refer to short-circuit failure and open-circuit failure.

[0067] It should be noted that any modification made to the specific embodiments of the present utility model by those skilled in the art does not depart from the scope of the claims of the present utility model. Accordingly, the scope of the claims of the present utility model is not limited to the foregoing specific embodiments.

Claims

1. A control and protection circuit for an LED, characterized in that, It includes multiple LED control and protection modules connected in parallel, each LED control and protection module including an LED control unit and an LED failure protection unit. The LED control unit includes LED1 and switching device T2. The positive terminal of LED1 is connected to node VF2, and its negative terminal is connected to node VF5. Node VF2 is connected to power supply V1. The first connection terminal of the switching device T2 is connected to node VF5, its second connection terminal is grounded, and its control terminal is connected to node A. Node A is connected to power supply V1. The input terminal of the LED failure protection unit is connected to the node VF2, and its output terminal is connected to the node A. When the LED failure protection unit detects a short circuit in LED1 through the voltage of the node VF5, the LED failure protection unit changes the voltage of the node A to control the switching device T2 to turn off.

2. The LED control and protection circuit according to claim 1, characterized in that, When the LED failure protection unit detects that the LED1 is working normally or open circuit through the voltage of the node VF5, the LED failure protection unit does not change the voltage of the node A; When LED1 is working normally, the switching device T2 is turned on; When LED1 is open, the switching device T2 is turned off.

3. The LED control and protection circuit according to claim 2, characterized in that, The LED failure protection unit includes resistors R2, R4, R6, R7, R8, and R11, diode D1, switching device T1, switching device T3, and switching device T4. The first connection terminal of the switching device T1 is connected to node VF3, its control terminal is connected to node VF2 via resistor R2, and its second connection terminal is connected to node VF4; node VF3 is connected to the power supply V1; the first connection terminal of the switching device T4 is connected to the power supply V1 via resistor R6, its control terminal is connected to node B via resistor R8, and its second connection terminal is connected to node VF1; one end of resistor R4 is connected to node VF4, and the other end is connected to node C; one end of resistor R7 is connected to node VF1, and the other end is connected to node C; one end of resistor R11 is connected to node C, and the other end is grounded; the cathode of diode D1 is connected to node B, and its anode is connected to node A; the first connection terminal of the switching device T3 is connected to node B, its control terminal is connected to node C, and its second connection terminal is grounded.

4. The LED control and protection circuit according to claim 3, characterized in that, When the LED failure protection unit detects that LED1 is working normally or open circuit through the voltage of node VF5, the switching devices T1, T4 and T3 are all turned off. When the LED failure protection unit detects a short circuit in LED1 through the voltage of node VF5, switching devices T1, T4 and T3 are all turned on.

5. The LED control and protection circuit according to claim 4, characterized in that, The LED failure protection unit also includes a Zener diode SD1. The positive terminal of the Zener diode SD1 is connected to the node VF3, and its negative terminal is connected to the power supply V1. When the LED failure protection unit detects that the LED1 is working normally or open circuit through the voltage of the node VF5, the Zener diode SD1 does not work; When the LED failure protection unit detects a short circuit in LED1 through the voltage of node VF5, the Zener diode SD1 operates.

6. The LED control and protection circuit according to claim 5, characterized in that, The LED control unit also includes resistors R1, R3, R5, and R12. One end of the resistor R3 is connected to the power supply V1, and the other end is connected to the node VF2; One end of the resistor R12 is connected to the power supply V1, and the other end is connected to node A; One end of the resistor R1 is connected to node A, and the other end is connected to the control terminal of the switching device T2; One end of the resistor R5 is connected to the control terminal of the switching device T2, and the other end is grounded.

7. The LED control and protection circuit according to claim 6, characterized in that, The switching device T1 is a PNP transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device T1 are the emitter, collector, and base of the PNP transistor, respectively. The switching device T2 is an NPN transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device T2 are the collector, emitter, and base of the NPN transistor, respectively. The switching device T3 is an NPN transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device T3 are the collector, emitter, and base of the NPN transistor, respectively. The switching device T4 is a PNP transistor, and the first connection terminal, the second connection terminal, and the control terminal of the switching device T4 are the emitter, collector, and base of the PNP transistor, respectively.

8. The LED control and protection circuit according to any one of claims 1-7, characterized in that, The power supply V1 is the output voltage of the DC-DC module.

Images