CN116744502A

CN116744502A - LED drive circuit, backlight source and vehicle display system including the circuit

Info

Publication number: CN116744502A
Application number: CN202310855263.XA
Authority: CN
Inventors: 朱晓东; 胡俊鹏; 付雪兰; 牛海潮
Original assignee: Continental Automotive Body Electronic System Wuhu Co Ltd
Current assignee: Continental Automotive Body Electronic System Wuhu Co Ltd
Priority date: 2023-07-12
Filing date: 2023-07-12
Publication date: 2023-09-12

Abstract

The invention relates to an LED drive circuit, which includes a power module and a drive module. The power module is used to supply power voltage to an LED array. The drive module includes a temperature detection unit for detecting the ambient temperature of the drive module. The power module includes a power supply, a voltage regulation unit, a power controller and a voltage detection unit. The power controller is configured to receive detection results from the voltage detection unit and the temperature detection unit, and use the detection results according to the received detection results. The voltage regulating unit regulates a power supply voltage supplied from the power supply to the LED array. The invention also relates to a backlight source including the LED driving circuit, and a vehicle-mounted display system including the backlight source.

Description

LED driving circuit, backlight source comprising same and vehicle-mounted display system

Technical Field

The application relates to an LED driving circuit, a backlight source comprising the LED driving circuit and a vehicle-mounted display system comprising the backlight source.

Background

Currently, with the development of vehicle technology, vehicle-mounted display products are also becoming more and more diversified. In vehicle displays, LED lamps are typically used as backlights. Conventional LED products typically use integrated circuits to drive the LEDs, which circuits allow for automatic regulation of the supply voltage based on the voltage drop across the LEDs. That is, in order to ensure that the LED can continuously and normally operate, it is necessary to supply a constant current or voltage to the LED by means of a driving circuit. The specific working principle of the integrated circuit is to control the power supply voltage through a PWM modulation technology, so that the purpose of controlling the working brightness of the LED is achieved. When the current of the LED is too large, the driver automatically reduces the output current of the LED, so that the LED is protected from damage.

In recent years, a novel area dimming display technology has been developed, which makes side light emission of a conventional display product direct light emission, and is divided into a plurality of areas, each of which is provided with a Light Emitting Diode (LED) lamp. In such a local dimming LED product, the driving circuit and the power supply are separated from each other and are usually provided in different circuit boards, so that automatic adjustment of the power supply voltage according to the LED operating conditions cannot be achieved.

Disclosure of Invention

According to a first aspect of the present application, there is provided an LED driving circuit comprising a power supply module for supplying a power supply voltage to an LED array, and a driving module configured to supply a constant driving current to the LED array based on the power supply voltage supplied by the power supply module, wherein,

the driving module comprises a temperature detection unit for detecting the ambient temperature of the driving module and feeding back the detection result to the power supply module,

the power module comprises a power supply, a voltage regulating unit, a power supply controller and a voltage detecting unit, wherein the voltage detecting unit is used for detecting the current working voltage of the LED array, the voltage regulating unit is arranged on a power supply path from the power supply to the LED array, the power supply controller is configured to receive detection results from the voltage detecting unit and the temperature detecting unit, and the power supply controller is used for regulating the power supply voltage supplied from the power supply to the LED array by means of the voltage regulating unit according to the received detection results.

Advantageously, the temperature detection unit comprises a thermal element arranged in the vicinity of the drive module, and the power supply controller is configured to infer an ambient temperature of the drive module based on a change in a resistance value of the thermal element.

Advantageously, the voltage adjusting unit includes a plurality of adjusting resistors connected in parallel to each other, each adjusting resistor having the same and/or different resistance value, each adjusting resistor having a switching element connected in series thereto, and the power supply controller is configured to selectively turn on the corresponding switching element according to detection results received from the voltage detecting unit and the temperature detecting unit to adjust the power supply voltage supplied to the LED array.

Advantageously, the power supply controller is further configured to obtain the voltage quantity Vf to be regulated based on the ambient temperature of the driving module and the current operating voltage of the LED array when the ambient temperature of the driving module exceeds a set threshold, and to reduce the power supply voltage supplied to the LED array by switching in the corresponding regulating resistor by means of the corresponding switching element.

Advantageously, the power supply controller is further configured to disconnect the respective regulating resistor from the supply path of the power supply when the ambient temperature of the drive module decreases to a target value.

Advantageously, the switching element is a transistor.

Advantageously, the voltage detection unit comprises a series circuit of a first resistor and a second resistor, one end of the series circuit being connected to the LED array and the other end being grounded, wherein the power supply controller is configured to derive the current operating voltage of the LED array based on the sampled voltage at the connection point between the first resistor and the second resistor.

Advantageously, the voltage regulating unit is connected between the connection point and ground.

According to a second aspect of the present application, there is also provided a backlight for an in-vehicle display system, the backlight comprising: an LED array; and an LED driving circuit as described above.

According to a third aspect of the present application, there is also provided a system for in-vehicle display, the system comprising: a display screen; and a backlight as described above, the backlight being disposed on the back of the display screen for providing corresponding backlighting to the display screen.

According to the LED driving circuit of the above embodiment of the present application, the ambient temperature is detected by placing a heat sensitive element (e.g., NTC) in the driving module (optionally, near the LED array), and the power supply voltage can be adjusted in combination with the operating voltage fed back by the LEDs and the ambient temperature information. In particular, when the ambient temperature is too high, the forward voltage drop across the drive module is caused by reducing the supply voltage, thereby reducing the heat loss of the drive module. The stability and safety of the illumination control of the LED array can also be ensured in a low, controllable temperature environment. At the same time, as the power supply voltage is reduced, the power consumption of the whole system is reduced, so the driving circuit can reduce the power consumption of the system. In addition, since the temperature of the driving module is reduced, the reliability of the system can be enhanced, and the performance of the driving module itself can be improved, i.e., the capability of driving the LED current can be increased.

Drawings

Other features and advantages of the methods of the present application will be apparent from, or are apparent from, the accompanying drawings, which are incorporated herein, and the detailed description of the application, which, together with the drawings, serve to explain certain principles of the application.

Fig. 1 is a schematic diagram showing the structure of a conventional integrated driving and controlling circuit.

Fig. 2 is a schematic diagram illustrating a structure of a conventional local dimming display system.

Fig. 3 illustrates a schematic structure of an LED driving circuit according to an exemplary embodiment of the present application.

Fig. 4 shows a flowchart of a voltage adjustment process of the LED driving circuit shown in fig. 3.

Detailed Description

An LED driving circuit according to the present application will be described below by way of embodiments with reference to the accompanying drawings. In the following description, numerous specific details are set forth in order to provide a thorough understanding of the present application to those skilled in the art. It will be apparent, however, to one skilled in the art that the present application may be practiced without some of these specific details. Rather, the application can be considered to be implemented with any combination of the following features and elements, whether or not they relate to different embodiments. Thus, the various aspects, features, embodiments and advantages described below are for illustration only and should not be considered elements or limitations of the claims.

The applicant has found that in a conventional integrated driving circuit, since the power supply and the driver are provided on the same circuit board, automatic adjustment of the power supply voltage of the LED as the LED demand changes can be easily achieved, as shown in fig. 1.

Unlike such an integrated driving circuit, in the local dimming display system shown in fig. 2, the power module and the driving module are separated from each other, that is, the local dimming display system generally includes two circuit boards independent of each other: the LED lamp panel is internally provided with an LED lamp and a driver, and the main board is internally provided with a power supply of an LED and other peripheral components.

In the local dimming display system, a power supply module is mainly responsible for anode power supply of the LED, and a driving module is responsible for constant current control of the LED. Typically, the voltage output by the power supply is a fixed value, but at the LED panel end, since the forward voltage drop of the LED voltage will have a floating voltage of approximately 1 volt at different temperatures and different color sets, this floating voltage drop will be emitted in the form of heat at the driver end, which will cause two problems: one is that the LED current is limited and the other is that if the driver heat is high, it can affect the reliability and power requirements of the system components.

Currently, there are two main approaches to LED driving technology of a local dimming display system in the market: one is directly driven by a driver, commonly referred to as "direct drive", and the other is to control the different LEDs to light up at different times by a switch matrix, commonly referred to as "time-sharing drive". The technical concept of the application is mainly proposed for the prior art without related heat management and power supply voltage regulation schemes under the two LED driving technologies.

Specifically, the present inventive concept is presented based on the following considerations: the LED light source can produce heat when working, if heat dissipation can not be timely carried out, the heat can enable the temperature of the surrounding environment to rise, and therefore the whole area dimming display product works at high temperature. At this time, since the energy lost by the driving module is high, the temperature is generally high. When the ambient temperature reaches a certain value, the heat generated by the driving module may affect other components in the display product, such as an optical film, a plastic part, and the like. While the LED itself increases with temperature, the required supply voltage is rather low. In this regard, the present application contemplates adding a thermal element to the existing LED driver circuit, by which the ambient temperature surrounding the driver module can be detected and fed back to the power controller of the motherboard. The power supply controller can control the adjusting resistance matrix of the feedback loop of the power supply end of the main board by utilizing the curve relation of the temperature and the voltage according to the feedback temperature, thereby realizing the purpose of reducing the power supply voltage.

Fig. 3 illustrates a schematic structure of an LED driving circuit according to an exemplary embodiment of the present application. As shown in fig. 3, the LED driving circuit includes a power module 10 and a driving module 20, wherein the power module 10 is responsible for supplying a power voltage to the LED array, and the driving module 20 can supply a constant driving current to the LED array based on the power voltage supplied from the power module 10.

The driving module 20 includes a temperature detecting unit 201 for detecting an ambient temperature of the driving module 20 and feeding back a detection result to the power module 10, particularly the power controller 102, as a judgment criterion for performing voltage regulation thereof. It is noted that during operation of the LED, both the driving module and the LED array in the LED circuit generate heat, but the heat generated by the driving module is usually the largest. In this context, the term "ambient temperature of the drive module 20" refers to a broad concept that encompasses the ambient temperature around the drive module and/or the LED array caused by the combined action of the drive module heat and the LED array heat. As a simplification, the ambient temperature may be taken as the highest temperature in the LED circuit, i.e. typically the temperature in the vicinity of the drive module.

The power module 10 may include a power source VCC, a voltage adjusting unit 101, a power source controller 102, and a voltage detecting unit 103, the voltage detecting unit 103 being configured to detect a current operating voltage of the LED array, the voltage adjusting unit 101 being disposed on a power supply path from the power source controller to the LED array, the power source controller 102 being configured to receive detection results from the voltage detecting unit 103 and the temperature detecting unit 201, and to adjust the power source voltage supplied from the power source VCC to the LED array by means of the voltage adjusting unit 101 according to the received detection results.

Specifically, the temperature detection unit 201 may include a thermal element disposed near the driving module (and/or the LED array), and the power controller 102 is configured to estimate the ambient temperature of the driving module 20 based on a change in resistance value of the thermal element. Here, the thermal element is implemented as a negative temperature coefficient thermistor (Negative Temperature Coefficient, NTC), the resistance value of which NTC decreases as the ambient temperature of the drive module increases. The current ambient temperature of the driving module can be calculated by monitoring the resistance value of the NTC. However, it will be understood by those skilled in the art that the thermosensitive element in the present application is not limited to the negative temperature coefficient thermistor, but may be replaced with other components such as a combination of a temperature sensor and a variable resistor, as long as it is possible to realize a change (increase or decrease) of the variable resistor with a change (increase or decrease) of the temperature measured by the temperature sensor.

The voltage detection unit 103 includes a series circuit composed of a first resistor R1 and a second resistor R2, one end of the series circuit is connected to the LED array, the other end is grounded, and the power supply controller 102 is configured to calculate the current operating voltage of the LED array based on the sampling voltage at the connection point between the first resistor R1 and the second resistor R2.

The voltage adjusting unit 101 may be connected between the connection point of the resistors R1, R2 and the ground terminal, and may include a plurality of adjusting resistors RS1, RS2 connected in parallel to each other, each having the same and/or different resistance values, and each having a switching element S1, S2 connected in series. The switching elements S1, S2 shown in fig. 3 are transistors, however other types of controlled switches are also conceivable. The power controller 102 may selectively turn on the respective switching elements S1, S2 according to the detection results received from the voltage detection unit 103 and the temperature detection unit 201 to adjust the power supply voltage supplied to the LED array.

Specifically, when the ambient temperature of the driving module 20 exceeds the set threshold, the power supply controller 102 may obtain the voltage amount Vf to be adjusted based on the ambient temperature of the driving module 20 and the current operating voltage of the LED array, and reduce the power supply voltage supplied to the LED array, for example, by switching in the corresponding adjusting resistors RS1, RS2 via the corresponding switching elements S1, S2.

After the voltage supplied to the LED array drops, the temperature of the driving module no longer rises or drops, at which time the switching-on of the regulating resistors can be continued until the ambient temperature of the driving module 20 drops to the target value, the respective regulating resistors RS1, RS2 can be switched off, i.e. the respective regulating resistors RS1, RS2 are disconnected from the supply path of the power supply.

The following describes the specific implementation steps of the voltage regulation process with reference to fig. 4:

the first step: the driving circuit monitors the ambient temperature of the driving module in real time through the NTC, and simultaneously outputs the current working voltage of the LED array by means of feedback control of R1 and R2;

and a second step of: when the ambient temperature of the driving module reaches a set threshold (which may be set based on the element that the product needs to protect), the LED temperature (the resistance and voltage drop of the NTC are inversely related to the temperature, i.e. the higher the temperature, the smaller the voltage drop) and the voltage curve may be queried, and the queried result is further sent to the power supply controller;

and a third step of: at the power supply controller, obtaining the voltage quantity Vf to be regulated according to the current working voltage of the LED array and the ambient temperature of the driving module;

fourth step: controlling a switching element (e.g., a triode) by means of a power supply controller to switch a regulating resistor conforming to the voltage quantity Vf to be regulated into a network of feedback resistors R1, R2, so that the power supply voltage supplied to the LEDs decreases the voltage quantity Vf;

fifth step: after the power supply voltage is reduced, the ambient temperature of the driving module is not increased or reduced any more, and the connection of the adjusting resistor can be continuously maintained at the moment; and

sixth step: the regulating resistor may be turned off until the ambient temperature of the drive module decreases to a lower limit.

According to another embodiment of the present application, there is also provided a backlight for an in-vehicle display system, the backlight including an LED array and an LED driving circuit as shown in fig. 3.

According to a further embodiment of the application, it also relates to a system for vehicle mounted display comprising a display screen and a backlight as described above, which backlight may be arranged for example at the back of the display screen for providing a corresponding backlighting to the display screen.

It will be appreciated by a person skilled in the art that the individual steps of the method according to the application are not limited to being carried out in the order listed above. Furthermore, in the present application, terms such as "comprising" and "including" mean that there are no other steps than those directly or explicitly described in the description and claims, nor do the inventive aspects exclude the presence of other steps not directly or explicitly described.

While the application has been described in terms of preferred embodiments, the application is not limited thereto. Any person skilled in the art shall not depart from the spirit and scope of the present application and shall accordingly fall within the scope of the application as defined by the appended claims.

Claims

1. An LED driving circuit comprising a power supply module (10) and a driving module (20), the power supply module (10) being for supplying a power supply voltage to an LED array, the driving module (20) being configured to supply a constant driving current to the LED array based on the power supply voltage provided by the power supply module (10),

the driving module (20) includes a temperature detecting unit (201), the temperature detecting unit (201) is configured to detect an ambient temperature of the driving module (20) and feed back a detection result to the power module (10),

the power module (10) comprises a power supply (VCC), a voltage regulating unit (101), a power supply controller (102) and a voltage detecting unit (103), wherein the voltage detecting unit (103) is used for detecting the current working voltage of the LED array, the voltage regulating unit (101) is arranged on a power supply path from the power supply (VCC) to a power supply port of the LED array, the power supply controller (102) is configured to receive detection results of the voltage detecting unit (103) and the temperature detecting unit (201), and regulate the power supply voltage supplied from the power supply (VCC) to the LED array by means of the voltage regulating unit (101) according to the received detection results.

2. The LED driving circuit according to claim 1, wherein the temperature detection unit (201) includes a heat sensitive element disposed near the driving module (20), and the power supply controller (102) is configured to estimate an ambient temperature of the driving module (20) based on a resistance change of the heat sensitive element.

3. LED driving circuit according to claim 1 or 2, characterized in that the voltage regulating unit (101) comprises a plurality of regulating resistors (RS 1, RS 2) connected in parallel to each other, each regulating resistor having the same and/or different resistance value, respectively, each regulating resistor being connected in series with a switching element (S1, S2), the power supply controller (102) being configured to selectively switch on the respective switching element (S1, S2) in accordance with the detection results received from the voltage detecting unit (103) and the temperature detecting unit (201) for regulating the power supply voltage supplied to the LED array.

4. A LED driving circuit according to claim 3, characterized in that the power supply controller (102) is further configured to obtain the amount of voltage Vf to be adjusted based on the ambient temperature of the driving module (20) and the current operating voltage of the LED array when the ambient temperature of the driving module (20) exceeds a set threshold value, and to reduce the power supply voltage supplied to the LED array by switching in the respective adjusting resistor (RS 1, RS 2) by means of the respective switching element (S1, S2).

5. The LED driving circuit according to claim 4, wherein the power supply controller (102) is further configured to disconnect the respective regulating resistor (RS 1, RS 2) from the supply path of the power supply when the ambient temperature of the driving module (20) decreases to a target value.

6. A LED driving circuit according to claim 3, characterized in that the switching elements (S1, S2) are transistors.

7. The LED driving circuit according to claim 1 or 2, characterized in that the voltage detection unit (103) comprises a series circuit of a first resistor (R1) and a second resistor (R2), one end of the series circuit being connected to the LED array and the other end being grounded, wherein the power supply controller (102) is configured to infer the current operating voltage of the LED array based on the sampled voltage at the connection point between the first resistor (R1) and the second resistor (R2).

8. The LED driving circuit according to claim 7, characterized in that the voltage regulating unit (101) is connected between the connection point and ground.

9. A backlight for an in-vehicle display system, the backlight comprising:

an LED array; and

the LED driving circuit according to any one of claims 1 to 8.

10. A display system for use on board a vehicle, the system comprising:

a display screen; and

the backlight of claim 9, disposed on a back side of the display screen for providing corresponding backlighting to the display screen.