Constant-current driving circuit and vehicle lamp device

Abstract

The utility model provides a constant current driving circuit and a vehicle lamp device, which are used for driving a plurality of paths of parallel LEDs, a protection unit is arranged between a power supply management unit and a lamp panel, the protection unit is provided with a fourth switch tube, the base electrode of the fourth switch tube is connected to the cathode driving end of a constant current unit, and when the cathode driving end is in overcurrent, the cathode driving end is connected with the constant current unit. When the lamp panel is powered off, the fourth switch tube is switched on, the switching states of the third switch tube, the second switch tube and the first switch tube are controlled to turn over, power supply to the lamp panel is cut off, and overcurrent protection is achieved. According to the constant-current driving circuit and the vehicle lamp device, when the current of any cathode driving end of the constant-current unit exceeds a corresponding threshold value, the switching state of the fourth switching tube can be triggered to turn over, then the protection unit is controlled to cut off power supply to the lamp panel, overcurrent damage to the lamp panel is avoided, and the service life of the vehicle lamp device is prolonged. Therefore, the damage rate of the multi-path parallel constant-current driving type LED vehicle lamp can be effectively reduced, the fault maintenance cost is reduced, the overcurrent fire risk can be reduced, and the safety is improved.

Description

Technical Field

[0001] The utility model relates to the technical field of lighting, and particularly relates to a constant current drive circuit and a vehicle lamp device. Background Art

[0002] Compared with traditional halogen tungsten bulbs, light emitting diodes (LEDs) have the advantages of low power, long life, short response time, small volume, etc. More and more vehicles use LEDs as vehicle lamp light sources.

[0003] In LED vehicle lamps, LED lamp beads are arranged in an array, and generally multiple paths are connected in parallel and driven by constant current to ensure the uniformity and stability of the luminous brightness. Among them, compared with traditional halogen tungsten bulbs, LEDs are more likely to burn out when overcurrent. In the multiple-path parallel constant current drive, when an LED lamp bead in one path is open-circuited and damaged, and the total current of the constant current drive remains unchanged, as the number of normal lamp strings sharing the total current becomes smaller, the current of the normal lamp strings increases, which easily causes the LEDs in the normal lamp strings to be overcurrent and damaged, increases the maintenance cost of the vehicle lamp, and there is a potential safety hazard of fire. Summary of the Utility Model

[0004] Based on this, the purpose of the utility model is to provide a constant current drive circuit and a vehicle lamp device to solve the problems that in the prior art, the multiple-path parallel constant current drive type LED vehicle lamp is prone to expand damage when the lamp beads are open-circuited and damaged, increases the maintenance cost, and has insufficient safety.

[0005] On the one hand, the utility model provides a constant current drive circuit for driving a lamp board with multiple paths of parallel-connected LEDs. The constant current drive circuit includes a power management unit, a constant current unit, and a protection unit. Among them,

[0006] The protection unit is connected between the output end of the power management unit and the anode input end of the lamp board, and the input end of the power management unit is connected to a driving power supply;

[0007] The constant current unit includes a plurality of cathode drive ends respectively connected to the cathodes of each lamp string of the lamp board, and an enable end connected to the output end of the power management unit;

[0008] The protection unit includes a first switching tube connected in series between the output end of the power management unit and the anode input end of the lamp board. The control end of the first switching tube is grounded through a second switching tube. The control end of the first switching tube is also connected to the output end of the power management unit through a first resistor. The control end of the second switching tube is connected to the output end of the power management unit through a second resistor. A third switching tube is connected between the control end and the output end of the second switching tube;

[0009] Wherein, the control terminal of the third switching transistor is respectively connected to the output terminal of the power management unit and the ground through a third resistor and a fourth resistor, the control terminal of the third switching transistor is also grounded through a fourth switching transistor, the base of the fourth switching transistor is connected to the cathode driving terminal, a plurality of the fourth switching transistors are provided, and are respectively connected to the plurality of cathode driving terminals in one-to-one correspondence.

[0010] Optionally, a first diode is further connected in series between the third resistor and the control terminal of the third switching transistor, and the input terminal of the fourth switching transistor is connected to the intermediate node between the third resistor and the first diode.

[0011] Optionally, a plurality of groups of the third resistor and the first diode are provided and are connected in parallel with each other, and the intermediate nodes of each group of the third resistor and the first diode are respectively connected to the input terminals of each of the fourth switching transistors in one-to-one correspondence.

[0012] Optionally, the first resistor is further connected in parallel with a first capacitor, the second resistor is further connected in parallel with a second capacitor, and the control terminal of the second switching transistor is further grounded through a third capacitor.

[0013] Optionally, a fifth resistor is further connected in series between the base of the fourth switching transistor and the cathode driving terminal.

[0014] Optionally, the constant current unit includes a first triode and a second triode, wherein,

[0015] the collector of the first triode is connected to the enable terminal through a sixth resistor, the emitter of the first triode is grounded, and the base of the first triode is grounded through a seventh resistor;

[0016] a plurality of the second triodes are provided, the bases of the second triodes are connected to the collector of the first triode, the collectors of each of the second triodes are respectively connected to each of the cathode driving terminals in one-to-one correspondence, and the emitters of the second triodes are connected to the base of the first triode.

[0017] Optionally, a fourth capacitor is connected between the collector and the emitter of the first triode.

[0018] Optionally, a second diode is further connected in series between each cathode driving terminal and the collector of each of the second triodes, an eighth resistor is further connected in series between the emitter of the second triode and the base of the first triode, and at least one second triode corresponding to one cathode driving terminal is connected in parallel.

[0019] Optionally, the power management unit includes a third diode connected in series between the positive input terminal and the output terminal of the power management unit. A fifth capacitor is connected between the positive input terminal and the ground. The fifth capacitor is in parallel with a ninth resistor. A sixth capacitor is connected between the output terminal of the power management unit and the ground. The negative input terminal of the power management unit is grounded. A transient diode is also connected between the positive input terminal of the power management unit and the ground.

[0020] The present invention also provides a vehicle lamp device, which includes a lamp board having multiple parallel-connected LEDs and the above constant current driving circuit.

[0021] The constant current driving circuit provided by the present invention is used for driving a lamp board with multiple parallel-connected LEDs. A protection unit is provided between the power management unit and the lamp board. The protection unit is provided with a fourth switching tube. The base of the fourth switching tube is connected to the cathode driving end of the constant current unit. When an overcurrent occurs at the cathode driving end, the fourth switching tube conducts, and then controls the switching states of the third switching tube, the second switching tube, and the first switching tube to flip, disconnecting the power supply to the lamp board to achieve overcurrent protection. When the current at any cathode driving end of the constant current unit in the constant current driving circuit of the present invention exceeds the corresponding threshold value, the switching state of the fourth switching tube can be triggered to flip, and then the protection unit is controlled to cut off the power supply to the lamp board, avoiding overcurrent damage to the lamp board, effectively reducing the damage rate of the multiple parallel-connected constant current driven LED vehicle lamp, reducing the fault maintenance cost, and reducing the risk of overcurrent fire, improving safety.

[0022] The vehicle lamp device provided by the present invention includes the above constant current driving circuit, which can effectively reduce the damage rate of the multiple parallel-connected constant current driven LED vehicle lamp, reduce the fault maintenance cost, and reduce the risk of overcurrent fire, improving the safety of the vehicle. Description of the Drawings

[0023] Figure 1 It is a schematic diagram of the main structure of the constant current driving circuit in the embodiment of the present invention.

[0024] The following specific embodiments will further illustrate the present invention in conjunction with the above drawings. Specific Embodiments

[0025] To facilitate the understanding of the present invention, the present invention will be described more comprehensively below with reference to the relevant drawings. Several embodiments of the present invention are given in the drawings. However, the present invention can be implemented in many different forms and is not limited to the embodiments described herein. On the contrary, these embodiments are provided to make the disclosure of the present invention more thorough and comprehensive.

[0026] It should be noted that when an element is referred to as being "fixed to" another element, it can be directly on the other element or there can also be an intermediate element. When an element is considered to be "connected to" another element, it can be directly connected to the other element or there may be an intermediate element at the same time. The terms "vertical", "horizontal", "left", "right" and similar expressions used herein are only for the purpose of illustration.

[0027] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by those of ordinary skill in the technical field to which this utility model belongs. The terms used herein in the specification of this utility model are only for the purpose of describing specific embodiments and are not intended to limit this utility model. The term "and / or" used herein includes any and all combinations of one or more of the related listed items.

[0028] To solve the problems in the prior art that in a multi-path parallel constant-current drive type LED headlight, when a lamp bead is open-circuited and damaged, it is easy to expand the damage, increase the maintenance cost, and have insufficient safety. This utility model provides a constant-current drive circuit for driving a lamp board with multi-path parallel LEDs. A protection unit is arranged between the power management unit and the lamp board. Specifically, the protection unit is provided with a fourth switching tube, and the base of the fourth switching tube is connected to the cathode drive end of the constant-current unit. When an overcurrent occurs at the cathode drive end, the fourth switching tube conducts, and then controls the switching states of the third switching tube, the second switching tube and the first switching tube to flip, disconnecting the power supply to the lamp board to achieve overcurrent protection. Thus, when the current at any cathode drive end exceeds the corresponding threshold, the switching state of the fourth switching tube can be triggered to flip, and then the protection unit is controlled to cut off the power supply to the lamp board, avoiding overcurrent damage to the lamp board, effectively reducing the damage rate of the multi-path parallel constant-current drive type LED headlight, reducing the fault maintenance cost, and reducing the risk of overcurrent fire, improving safety.

[0029] Specifically, as Figure 1 shown, the constant-current drive circuit of this embodiment is used for driving a lamp board 01 with multi-path parallel LEDs, and includes a power management unit 10, a constant-current unit 30 and a protection unit 20. The protection unit 20 is connected between the output end of the power management unit 10 and the anode input end of the lamp board 01. The input end of the power management unit 10 is connected to the drive power supply VCC. The constant-current unit 30 includes a plurality of cathode drive ends connected to the cathodes of the respective lamp strings of the lamp board 01 one by one, and an enable end connected to the output end of the power management unit 10. When the lamp board 01 is normal, after connecting to the drive power supply VCC, the power management unit 10 provides a stable voltage output at its output end, the enable end of the constant-current unit 30 is connected to an effective enable signal and enabled, and at the same time the protection unit 20 is set to the on state, and the lamp board 01 lights up normally.

[0030] The protection unit 20 includes a first switching transistor Q1 connected in series between the output terminal of the power management unit 10 and the anode input terminal of the lamp board 01. The control terminal of the first switching transistor Q1 is grounded through a second switching transistor Q2. The control terminal of the first switching transistor Q1 is also connected to the output terminal of the power management unit 10 through a first resistor R1. The control terminal of the second switching transistor Q2 is connected to the output terminal of the power management unit 10 through a second resistor R2. A third switching transistor Q3 is connected between the control terminal of the second switching transistor Q2 and the output terminal. The control terminal of the third switching transistor Q3 is connected to the output terminal of the power management unit 10 and the ground respectively through a third resistor R3 and a fourth resistor R4. The control terminal of the third switching transistor Q3 is also grounded through a fourth switching transistor Q4. The base of the fourth switching transistor Q4 is connected to the cathode driving terminal. There are multiple fourth switching transistors Q4, and they are connected to multiple cathode driving terminals in one-to-one correspondence.

[0031] In this embodiment, the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 are all logic high-level conduction type switching transistors. When overcurrent occurs in any one of the lamp strings of the lamp board 01, the corresponding cathode driving terminal of the constant current unit 30 is affected by the overcurrent and the voltage rises, reaching the conduction condition of the fourth switching transistor Q4. The fourth switching transistor Q4 conducts, pressing down the control terminal of the third switching transistor Q3 to the ground potential. The third switching transistor Q3 turns off. The control terminal of the second switching transistor Q2 is pulled up to a high level through the second resistor R2. The second switching transistor Q2 conducts, and then pulls down the control terminal of the first switching transistor Q1 to the ground level. The first switching transistor Q1 turns off, thereby realizing the power-off of the lamp board 01 and realizing overcurrent protection.

[0032] Specifically, the first switching transistor Q1 and the second switching transistor Q2 are, for example, insulated gate bipolar transistors, which have strong current load capacity, can improve the reliability of the first switching transistor Q1 as the main control switch for powering on the lamp board 01, and improve the reliability of the second switching transistor Q2 that can be used as current discharge during power-off, thereby ensuring the reliability of the use of the protection unit 20 and ensuring the reliability of overcurrent protection during long-term use, or an N-type MOS transistor is used; the third switching transistor Q3 and the fourth switching transistor Q4 are, for example, NPN-type triodes, or an N-type MOS transistor is used.

[0033] Among them, the specific types of the first switching transistor Q1, the second switching transistor Q2, the third switching transistor Q3, and the fourth switching transistor Q4 can be specifically selected according to specific circumstances. As long as the formed logic chain can realize the switching state of the first switching transistor Q1 flipping with the switching state of the fourth switching transistor Q4, they all fall within the scope of implementation of the present invention.

[0034] For example, the first switching transistor Q1 and the second switching transistor Q2 are logic low-level conduction type switching transistors, and the third switching transistor Q3 and the fourth switching transistor Q4 are logic high-level conduction type switching transistors.

[0035] A first diode D1 is also connected in series between the third resistor R3 and the control terminal of the third switching transistor Q3. The input terminal of the fourth switching transistor Q4 is connected to the intermediate node between the third resistor R3 and the first diode D1, which can avoid the interference of reverse current on the potential of the control terminal of the third switching transistor Q3 and ensure the accuracy of control.

[0036] Corresponding to multiple fourth switching transistors Q4, in order to further reduce the interference between them, in this embodiment, multiple sets of the third resistor R3 and the first diode D1 are provided and are connected in parallel with each other. The intermediate nodes of each set of the third resistor R3 and the first diode D1 are respectively and correspondingly connected to the input terminals of each fourth switching transistor Q4.

[0037] In order to reduce the influence of voltage fluctuation interference, in this embodiment, the first resistor R1 is also connected in parallel with a first capacitor C1, the second resistor R2 is also connected in parallel with a second capacitor C2, and the control terminal of the second switching transistor Q2 is also grounded through a third capacitor C3.

[0038] A fifth resistor R5 is also connected in series between the base and the cathode driving terminal of the fourth switching transistor Q4. The fifth resistor R5 can be used as a current-limiting resistor to reduce the breakdown risk of the fourth switching transistor Q4.

[0039] In order to ensure constant current driving, in this embodiment, the constant current unit 30 adopts a triode constant current driving circuit, which includes a first triode Q5 and a second triode Q6. Among them, the collector of the first triode Q5 is connected to the enable terminal through a sixth resistor R6, the emitter of the first triode Q5 is grounded, the base of the first triode Q5 is grounded through a seventh resistor R7, and the voltage drop between the base and the emitter of the first triode Q5 is maintained stable, so that the voltage drop across the first resistor R7 is maintained stable and the current flowing through the first resistor R7 is maintained stable; multiple second triodes Q6 are provided. The bases of the second triodes Q6 are connected to the collector of the first triode Q5. The collectors of each second triode Q6 are respectively and correspondingly connected to each cathode driving terminal. The emitters of the second triodes Q6 are connected to the base of the first triode Q5. Each path of the second triodes Q6 is connected in parallel to the seventh resistor R7, and its total current is equal to the current of the seventh resistor R7, which can maintain the total current constant and achieve constant current driving.

[0040] In order to improve the working stability of the constant current unit 60, in this embodiment, a fourth capacitor C4 is connected between the collector and the emitter of the first triode Q5, which can improve the stability of its collector voltage, and further improve the stability of the base voltage of each second triode Q6, improve the stability of the working state of the second triode Q6, and further improve the constant current effect.

[0041] A second diode D2 is also connected in series between each cathode driving terminal and the collector of each second triode Q6, which can improve the unidirectional stability of the current and ensure the driving effect on the lamp board. An eighth resistor R8 is also connected in series between the emitter of the second triode Q6 and the base of the first triode Q5, which can improve the rate of change of the voltage drop from the cathode driving terminal to the seventh resistor R7 with the current, increase the voltage rise degree of the cathode driving terminal during overcurrent, and facilitate the selection of the specific specifications of the fourth switching tube Q4. At least one second triode Q6 is connected in parallel with a corresponding cathode driving terminal, which can reduce the current load of a single second triode Q6, improve the driving current load capacity, and facilitate increasing the driving current magnitude of a single lamp string according to the brightness requirement of the lamp string of the lamp board 01.

[0042] The power management unit 10 includes a third diode D3 connected in series between the positive input terminal and the output terminal of the power management unit. A fifth capacitor C5 is connected between the positive input terminal and the ground, and the fifth capacitor C5 is connected in parallel with a ninth resistor R9. A sixth capacitor C6 is connected between the output terminal of the power management unit 10 and the ground. The negative input terminal of the power management unit 10 is grounded, which can improve the stability of the input voltage and the output voltage. A transient diode D4 is also connected between the positive input terminal of the power management unit 10 and the ground, which can be used for overcurrent and overvoltage protection of the input power supply connected to the power management unit 10 and ensure the electrical safety of the backend.

[0043] The present utility model also provides a vehicle lamp device, which includes a lamp board with multiple parallel-connected LEDs and the above-mentioned constant current driving circuit. When an open circuit fault occurs in any one of the multiple parallel-connected LED lamp paths of the lamp board, the power supply to the lamp board can be disconnected, avoiding overcurrent damage to other lamp strings, effectively reducing the damage rate of the LED lamp beads of the lamp board, reducing the fault repair cost, and reducing the risk of overcurrent ignition, thus improving the vehicle safety.

[0044] In the description of this specification, the description with reference to terms such as "one embodiment", "some embodiments", "example", "specific example", or "some examples" means that the specific features, structures, materials, or characteristics described in connection with the embodiment or example are included in at least one embodiment or example of the present utility model. In this specification, the schematic representations of the above terms do not necessarily refer to the same embodiment or example. Moreover, the specific features, structures, materials, or characteristics described can be combined in a suitable manner in any one or more embodiments or examples.

[0045] The above-described embodiments merely represent several specific implementation manners of the present utility model. The description thereof is relatively specific and detailed, but it should not be construed as a limitation to the scope of the patent of the present utility model. It should be noted that for those of ordinary skill in the art, without departing from the concept of the present utility model, several variations and improvements can still be made, and these all fall within the protection scope of the present utility model. Therefore, the protection scope of the patent of the present utility model shall be subject to the appended claims.

Claims

1. A constant current driving circuit for driving a lamp board with multiple parallel LEDs, characterized in that, The flow driving circuit includes a power management unit, a constant current unit, and a protection unit. Among them, the protection unit is connected between the output terminal of the power management unit and the anode input terminal of the lamp board, and the input terminal of the power management unit is connected to the driving power supply; the constant current unit includes a plurality of cathode driving terminals respectively connected to the cathodes of each lamp string of the lamp board, and an enable terminal connected to the output terminal of the power management unit; the protection unit includes a first switching tube connected in series between the output terminal of the power management unit and the anode input terminal of the lamp board. The control terminal of the first switching tube is grounded through a second switching tube. The control terminal of the first switching tube is also connected to the output terminal of the power management unit through a first resistor. The control terminal of the second switching tube is connected to the output terminal of the power management unit through a second resistor. A third switching tube is connected between the control terminal and the output terminal of the second switching tube; wherein, the control terminal of the third switching tube is respectively connected to the output terminal of the power management unit and the ground through a third resistor and a fourth resistor. The control terminal of the third switching tube is also grounded through a fourth switching tube. The base of the fourth switching tube is connected to the cathode driving terminal. There are a plurality of the fourth switching tubes, and they are respectively connected to the plurality of cathode driving terminals in one-to-one correspondence.

2. The constant current driving circuit according to claim 1, wherein A first diode is also connected in series between the third resistor and the control terminal of the third switching tube. The input terminal of the fourth switching tube is connected to the intermediate node between the third resistor and the first diode.

3. The constant current driving circuit according to claim 2, wherein, There are multiple groups of the third resistor and the first diode, and they are connected in parallel with each other. The intermediate nodes of each group of the third resistor and the first diode are respectively connected to the input terminals of each fourth switching tube in one-to-one correspondence.

4. The constant current driving circuit according to claim 1, characterized in that The first resistor is also connected in parallel with a first capacitor. The second resistor is also connected in parallel with a second capacitor. The control terminal of the second switching tube is also grounded through a third capacitor.

5. The constant current driving circuit according to claim 1, characterized in that, A fifth resistor is also connected in series between the base of the fourth switching tube and the cathode driving terminal.

6. The constant current driving circuit according to claim 1, wherein The constant current unit includes a first triode and a second triode. Among them, the collector of the first triode is connected to the enable terminal through a sixth resistor. The emitter of the first triode is grounded. The base of the first triode is grounded through a seventh resistor; there are a plurality of the second triodes. The bases of the second triodes are connected to the collector of the first triode. The collectors of each second triode are respectively connected to each cathode driving terminal in one-to-one correspondence. The emitters of the second triodes are connected to the base of the first triode.

7. The constant current driving circuit according to claim 6, wherein A fourth capacitor is connected between the collector and the emitter of the first triode.

8. The constant current driving circuit according to claim 6, wherein A second diode is also connected in series between each cathode driving terminal and the collector of each second triode. An eighth resistor is also connected in series between the emitter of the second triode and the base of the first triode. There is at least one second triode connected in parallel with one of the cathode driving terminals.

9. The constant current driving circuit according to claim 1, wherein The power management unit includes a third diode connected in series between the positive input terminal and the output terminal of the power management unit. A fifth capacitor is connected between the positive input terminal and the ground. The fifth capacitor is in parallel with a ninth resistor. A sixth capacitor is connected between the output terminal of the power management unit and the ground. The negative input terminal of the power management unit is grounded. A transient diode is also connected between the positive input terminal of the power management unit and the ground.

10. A vehicle lamp device, characterized in that, It includes a lamp board having multiple parallel-connected LEDs, and the constant current driving circuit according to any one of claims 1 to 9.

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