A linear LED driving circuit and a vehicle-mounted LED control system
By using a comparator to detect open and short circuits in the vehicle LED driver circuit, the problems of high cost and slow response speed in the prior art are solved, realizing a fast protection and cost-effective LED driver circuit design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- SINOTECH MIXIC ELECTRONICS
- Filing Date
- 2025-07-02
- Publication Date
- 2026-06-09
AI Technical Summary
Existing open-circuit and short-circuit protection solutions for automotive LED driver circuits suffer from high hardware costs, large circuit board space requirements, and slow response speeds.
Comparators are used to implement open-circuit and short-circuit protection. The first and second comparators are used to detect the open-circuit and short-circuit conditions of the LED module, respectively. The switching of the constant current LED driver circuit is controlled by a logic judgment unit, which reduces hardware costs and improves response speed.
It achieves fast open-circuit and short-circuit protection, reduces hardware costs and circuit board space, and improves protection response speed.
Smart Images
Figure CN224343415U_ABST
Abstract
Description
Technical Field
[0001] This utility model relates to the field of drive circuit design technology, and in particular to a linear LED drive circuit and an on-board LED control system. Background Technology
[0002] Existing automotive LED drivers typically employ different driver circuits for different LED modules. During the production and debugging of these driver circuits, short circuits at the driver circuit output and open circuits in the LED module are common anomalies. Therefore, LED driver circuits are generally designed with open-circuit and short-circuit protection functions.
[0003] A common open-circuit protection scheme uses a Zener diode paired with a current-limiting resistor: when an LED becomes open-circuited, the increased output voltage causes the Zener diode to break down and conduct. The conduction current creates a voltage drop across the current-limiting resistor. This voltage drop, once detected, can control the chip to stop working, thus achieving open-circuit protection. However, this additional protection circuitry increases hardware costs and board space, and is more difficult to debug. A common short-circuit protection scheme uses a current-limiting resistor: when a short circuit occurs, the current increases sharply, and the voltage drop across the current-limiting resistor increases accordingly. When the voltage drop exceeds its power limit, the resistor automatically disconnects and its resistance becomes infinite, thus achieving short-circuit protection. However, this scheme has the limitation of a slower response speed. Utility Model Content
[0004] To address the shortcomings of existing technologies, this invention provides a linear LED driving circuit and an on-board LED control system, which solves the problem of design defects in open-circuit protection and short-circuit protection in existing LED driving circuits.
[0005] According to an embodiment of the present invention, a first aspect provides a linear LED driving circuit, comprising:
[0006] A constant current LED driver includes a power transistor, a constant voltage output module connected to the emitter and base of the power transistor, and the collector of the power transistor connected to an external linear LED module. A sampling resistor is also connected in series between the constant voltage output module and the emitter of the power transistor. The operating current of the linear LED module is obtained based on the constant voltage output module and the sampling resistor.
[0007] The first comparator includes a first open-circuit sampling input terminal connected to the emitter of the power transistor, a second open-circuit sampling input terminal connected to the collector of the power transistor, and a first output terminal connected to the constant voltage output module;
[0008] The second comparator includes a first short-circuit sampling input terminal connected to the reference voltage module, a second short-circuit sampling input terminal connected to the collector of the power transistor, and a second output terminal connected to the constant voltage output module.
[0009] Optionally, the constant voltage output module includes a trigger unit, a logic judgment unit, an amplifier, and a voltage control unit;
[0010] The triggering unit is connected to the logic judgment unit, which is also connected to the reference voltage terminal of the amplifier, the first comparator, and the second comparator. The voltage control unit is connected to the positive input terminal of the amplifier and one end of the sampling resistor. The output terminal of the amplifier is connected to the base of the power transistor. The inverting input terminal of the amplifier is connected to the other end of the sampling resistor, the emitter of the power transistor, and the first open-circuit sampling input terminal of the first comparator.
[0011] Optionally, the positive input terminal of the first comparator is the second short-circuit sampling input terminal, the negative input terminal of the first comparator is the first short-circuit sampling input terminal, and the output terminal of the first comparator is the first output terminal, which is connected to the logic judgment unit.
[0012] Optionally, the positive input terminal of the second comparator is the second open-circuit sampling input terminal, the negative input terminal of the second comparator is the first open-circuit sampling input terminal, and the output terminal of the second comparator is the second output terminal, which is connected to the logic judgment unit.
[0013] Optionally, the reference voltage module is a BANDGAP bandgap reference voltage source.
[0014] A second aspect provides an in-vehicle LED control system, including a linear LED module and a linear LED driving circuit, wherein the linear LED driving circuit drives the linear LED module.
[0015] Optionally, the first and second comparators in the linear LED driving circuit are multiplexed from the comparators in the vehicle's overall control system.
[0016] Optionally, the switching voltage of the first comparator is 300mV.
[0017] Optionally, the switching voltage of the second comparator is 900mV.
[0018] Optionally, the number of LEDs in the linear LED module can be adjusted.
[0019] Compared with existing technologies, this invention uses a comparator to achieve open-circuit and short-circuit protection, with a fast response speed. Furthermore, the comparator can reuse electronic components from other systems, reducing hardware costs and circuit board space requirements. Attached Figure Description
[0020] Figure 1 This is a schematic diagram of the linear LED driving circuit according to an embodiment of the present invention;
[0021] Figure 2 This is a schematic diagram of the circuit structure of the linear LED driving circuit according to an embodiment of the present invention. Detailed Implementation
[0022] The technical solution of this utility model will be further described below with reference to the accompanying drawings and embodiments.
[0023] like Figure 1 As shown in the figure, this utility model embodiment proposes a linear LED driving circuit, including a constant current LED driver 10, a first comparator COMP1, a second comparator COMP2, and a reference voltage module 20. Figure 1 In the linear LED driver circuit, the circuit structure is as follows: the constant current LED driver 10 includes a power transistor Q1, a constant voltage output module U1, and a sampling resistor R. SNS In this configuration, the emitter and base of power transistor Q1 are connected to the constant voltage output module U1, and the sampling resistor R... SNS A first comparator COMP1 is connected in series between the constant voltage output module U1 and the emitter of the power transistor Q1, with the collector of the power transistor Q1 connected to the external linear LED module 30. COMP1 includes a first open-circuit sampling input connected to the emitter of the power transistor Q1, a second open-circuit sampling input connected to the collector of the power transistor Q1, and a first output connected to the constant voltage output module U1, used for open-circuit protection of the linear LED driving circuit. COMP2 includes a first short-circuit sampling input connected to the reference voltage module 20, a second short-circuit sampling input connected to the collector of the power transistor Q1, and a second output connected to the constant voltage output module U1, used for short-circuit protection of the linear LED driving circuit. Figure 1 In the diagram, the connection point between the collector of power transistor Q1 and the linear LED module 30 is marked as OUT, and the sampling resistor R... SNS Mark a point IN at the end connected to the emitter of power transistor Q1.
[0024] The linear LED driving circuit provided in this embodiment works on the following principle:
[0025] The linear LED module 30 obtains a fixed operating current under the control of the constant current LED driver 10. The first comparator COMP1, through its first and second open-circuit sampling input terminals, measures the input and output voltage of the power transistor Q1, i.e., the voltage V at point OUT. OUT The voltage V at point IN IN The voltage change at the first output terminal of the first comparator COMP1 is used to determine whether there is an open circuit in part of the linear LED module 30. The second comparator COMP2, through the first and second short-circuit sampling input terminals, converts the output voltage of power transistor Q1, i.e., the voltage V at point OUT. OUT The voltage change at the second output terminal of the second comparator COMP2 is compared with the reference voltage provided by the reference voltage module 20 to determine whether there is a short circuit in part of the linear LED module 30. The first output terminal of the first comparator COMP1 and the second output terminal of the second comparator COMP2 are also connected to the constant voltage output module U1 of the constant current LED driver 10. Therefore, when there is an open circuit or short circuit, the constant voltage output module U1 is turned off, and the constant current LED driver 10 stops providing operating current to the linear LED module 30, thereby realizing open circuit protection and short circuit protection.
[0026] The linear LED driving circuit provided in this embodiment of the present invention utilizes a comparator to achieve open-circuit and short-circuit protection, has a fast response speed, and the comparator can reuse electronic components from other systems, reducing hardware costs and circuit board space.
[0027] like Figure 2 As shown in the figure, this utility model embodiment illustrates the detailed circuit structure of a linear LED driving circuit. The constant voltage output module U1 includes a trigger unit INPUT, a logic judgment unit LOGIC, an amplifier EA, and a voltage control unit SENSE. The trigger unit INPUT is connected to the logic judgment unit LOGIC, which is also connected to the reference voltage terminal of the amplifier EA, the first output terminal of the first comparator COMP1, and the second output terminal of the second comparator COMP2. The voltage control unit SENSE is connected to the positive input terminal of the amplifier EA and the sampling resistor R. SNS One end of the amplifier is connected, the output terminal of amplifier EA is connected to the base of power transistor Q1, and the inverting input terminal of amplifier EA is connected to the sampling resistor R. SNS The other end is connected to the emitter of the power transistor Q1 and the first open-circuit sampling input of the first comparator COMP1.
[0028] In the aforementioned constant current LED driver 10, the amplifier EA and sampling resistor R of the constant voltage output module U1 SNSA negative feedback loop is formed with power transistor Q1, where amplifier EA adjusts the conduction level of power transistor Q1 to ultimately maintain a constant current flowing through the linear LED module 30. The detailed process is as follows: the voltage control unit SENSE and the sampling resistor R... SNS The voltage at one end of the connection is V supply Sampling resistor R SNS The voltage at the end connected to the emitter of power transistor Q1 is V. IN The output voltage of amplifier EA will V SUPPLY -V IN For a fixed value V CS The operating current of the linear LED module 30 is: The logic judgment unit LOGIC is connected to the reference voltage terminal of amplifier EA, the first output terminal of first comparator COMP1, the second output terminal of second comparator COMP2, and trigger unit INPUT. The output of first comparator COMP1 indicates whether there is an open circuit in part of the linear LED module 30, and the output of second comparator COMP2 indicates whether there is a short circuit in part of the linear LED module 30. Therefore, the logic judgment unit LOGIC is mainly used to turn amplifier EA on or off and power transistor Q1 on or off according to the output of trigger unit INPUT, the output of first comparator COMP1, and the output of second comparator COMP2, thereby completing the switching control of the entire LED driver circuit, as well as open circuit protection and short circuit protection.
[0029] It should be noted that, Figure 2 In this circuit, the positive input of the first comparator COMP1 is the second short-circuit sampling input, the negative input of the first comparator COMP1 is the first short-circuit sampling input, and the output of the first comparator COMP1 is the first output, connected to the logic unit LOGIC. The positive input of the second comparator COMP2 is the second open-circuit sampling input, the negative input of the second comparator COMP2 is the first open-circuit sampling input, and the output of the second comparator COMP2 is the second output, also connected to the logic unit LOGIC. By setting the switching voltages of the first comparator COMP1 and the second comparator COMP2, open-circuit protection and short-circuit protection in different application scenarios can be achieved. For example, if the switching voltage of the first comparator COMP1 is 300mV and the switching voltage of the second comparator COMP2 is 900mV, then in practical applications, when the linear LED module 30 is open-circuited, no current can flow through the voltage control unit SENSE and the sampling resistor R. SNS One end of the connection -- sampling resistor R SNS --Power transistor Q1-Power transistor Q1 collector output OUT--Linear LED module 30, the final path is to ground, so the output voltage V of the collector of power transistor Q1OUT It will be gradually pulled up until V SUPPLY Up to this point, the sampling resistor R SNS The voltage at the other end V IN It will also gradually rise to V. SUPPLY During this process, the first comparator COMP1 will detect when V OUT Below V IN When the voltage reaches 300mV, it is determined that the LED is open-circuited. The output of the first comparator COMP1 flips, and after passing through the logic judgment unit LOGIC, a control signal is output to turn off the amplifier EA, thereby turning off the power transistor Q1, thus providing protection. When a short circuit occurs in the linear LED module 30, the output voltage of the collector of the power transistor Q1 is directly shorted to GND, and the second comparator COMP2 will detect V. OUT If the voltage drops below 900mV, it is determined that the LED is short-circuited. The output of the second comparator COMP2 flips, and after passing through the logic judgment unit LOGIC, it outputs a control signal to turn off the amplifier EA, thereby turning off the power transistor Q1 and providing protection.
[0030] In a preferred implementation, the reference voltage module 20 is a BANDGAP bandgap reference voltage source used to generate a reference voltage with zero temperature drift, which can accurately determine open circuit and short circuit conditions within different temperature ranges.
[0031] This utility model embodiment also provides an in-vehicle LED control system, including a linear LED module 30 and the aforementioned linear LED driving circuit, to illustrate the practical application of the linear LED driving circuit to the linear LED module 30 in the in-vehicle LED control system. It should be noted that in the in-vehicle LED control system, the linear LED module 30 can be a structure used in in-vehicle dynamic through-type taillights or in-vehicle dynamic light-emitting grilles; this is not limited to these specific applications.
[0032] In a better implementation, the first comparator COMP1 and the second comparator COMP2 in the linear LED driver circuit reuse the comparators in the vehicle's overall control system to reduce hardware costs and board space.
[0033] In a better implementation, the switching voltage of the first comparator COMP1 is 300mV and the switching voltage of the second comparator COMP2 is 900mV. This can provide more accurate and faster protection for the actual application scenarios of vehicle LED control systems.
[0034] In a better implementation, the number of LEDs in the linear LED module 30 can be adjusted to avoid insufficient output voltage of the linear LED driver circuit due to a large number of LEDs connected in series in the linear LED module 30.
[0035] Finally, it should be noted that the above embodiments are only used to illustrate the technical solutions of this utility model and are not intended to limit it. Although this utility model has been described in detail with reference to preferred embodiments, those skilled in the art should understand that modifications or equivalent substitutions can be made to the technical solutions of this utility model without departing from the spirit and scope of the technical solutions of this utility model, and all such modifications or substitutions should be covered within the scope of the claims of this utility model.
Claims
1. A linear LED driving circuit, characterized in that, include: A constant current LED driver includes a power transistor, a constant voltage output module connected to the emitter and base of the power transistor, and the collector of the power transistor is connected to an external linear LED module. A sampling resistor is also connected in series between the constant voltage output module and the emitter of the power transistor to obtain the operating current of the linear LED module based on the constant voltage output module and the sampling resistor. The first comparator includes a first open-circuit sampling input terminal connected to the emitter of the power transistor, a second open-circuit sampling input terminal connected to the collector of the power transistor, and a first output terminal connected to the constant voltage output module; The second comparator includes a first short-circuit sampling input terminal connected to the reference voltage module, a second short-circuit sampling input terminal connected to the collector of the power transistor, and a second output terminal connected to the constant voltage output module.
2. The linear LED driving circuit as described in claim 1, characterized in that, The constant voltage output module includes a trigger unit, a logic judgment unit, an amplifier, and a voltage control unit; The triggering unit is connected to the logic judgment unit, which is also connected to the reference voltage terminal of the amplifier, the first comparator, and the second comparator. The voltage control unit is connected to the positive input terminal of the amplifier and one end of the sampling resistor. The output terminal of the amplifier is connected to the base of the power transistor. The inverting input terminal of the amplifier is connected to the other end of the sampling resistor, the emitter of the power transistor, and the first open-circuit sampling input terminal of the first comparator.
3. The linear LED driving circuit as described in claim 2, characterized in that, The positive input terminal of the first comparator is the second short-circuit sampling input terminal, the negative input terminal of the first comparator is the first short-circuit sampling input terminal, and the output terminal of the first comparator is the first output terminal, which is connected to the logic judgment unit.
4. The linear LED driving circuit as described in claim 2, characterized in that, The positive input terminal of the second comparator is the second open-circuit sampling input terminal, the negative input terminal of the second comparator is the first open-circuit sampling input terminal, and the output terminal of the second comparator is the second output terminal, which is connected to the logic judgment unit.
5. The linear LED driving circuit according to any one of claims 1 to 4, characterized in that, The reference voltage module is a BANDGAP bandgap reference voltage source.
6. A vehicle-mounted LED control system, characterized in that, It includes a linear LED module and a linear LED driving circuit as described in any one of claims 1 to 5, wherein the linear LED driving circuit drives the linear LED module.
7. The vehicle-mounted LED control system as described in claim 6, characterized in that, The first and second comparators in the linear LED driving circuit are multiplexed from the comparators in the vehicle's overall control system.
8. The vehicle-mounted LED control system as described in claim 6 or 7, characterized in that, The switching voltage of the first comparator is 300mV.
9. The vehicle-mounted LED control system as described in claim 6 or 7, characterized in that, The switching voltage of the second comparator is 900mV.
10. The vehicle-mounted LED control system as described in claim 6 or 7, characterized in that, The number of LEDs in the linear LED module is adjustable.