CN211479626U - LCD backlight drive circuit - Google Patents
LCD backlight drive circuit Download PDFInfo
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- CN211479626U CN211479626U CN202020372189.8U CN202020372189U CN211479626U CN 211479626 U CN211479626 U CN 211479626U CN 202020372189 U CN202020372189 U CN 202020372189U CN 211479626 U CN211479626 U CN 211479626U
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Abstract
The utility model provides a backlight driving circuit of a liquid crystal display, which relates to the technical field of vehicle-mounted electronics and comprises a booster circuit connected with the anode of a vehicle-mounted storage battery power supply; the liquid crystal display comprises a plurality of LED diodes which are connected in series; the output end of the booster circuit is connected with the anode of the first LED diode of the liquid crystal display through a current-limiting resistor, and the cathode of the last LED diode is connected with the dimming circuit. The utility model discloses LCD backlight drive circuit has quick response, integrality, safe and reliable, low cost's advantage.
Description
Technical Field
The utility model relates to a LCD drive circuit that is shaded belongs to on-vehicle electron technical field.
Background
The automobile industry is continuously developing, automobile electronics are also changing day by day, and in vehicle-mounted electronics, liquid crystal displays are used more and more, and screens are also larger and larger. As liquid crystal displays become larger and more influential to users, the demand for displays becomes higher and higher.
In an on-board environment, there are fluctuations in the on-board voltage due to the constant alignment and variation of the on-board load. If the screen of the liquid crystal display is small, the display content is less, and even if the backlight of the liquid crystal display fluctuates, the influence on a user is small; if the screen is large, the display content is large, the backlight of the liquid crystal display fluctuates, the reading information is influenced, the driving pleasure is influenced, and even the driving safety is influenced.
In the existing automotive electronics, the lcd backlight driving circuits are generally classified into the following types:
the first scheme is as follows: a current limiting resistor is used.
The advantages are that: the cost is low.
The disadvantages are as follows: 1. when the vehicle-mounted voltage fluctuates, the backlight of the liquid crystal display fluctuates correspondingly. 2. In order to enable the liquid crystal to be used in a wider ground voltage range, the current limiting resistor can limit current, the resistance value of the current limiting resistor needs to be selected to be large, and when the liquid crystal works, a large voltage drop is generated, so that the backlight output energy efficiency is influenced, and meanwhile, large heat is generated.
Scheme II: voltage reduction and current limiting resistors are used.
The advantages are that: and for the use environment of small current, the realization is simple and the cost is low.
The disadvantages are as follows: for the use environment of heavy current, the efficiency is low, and it is big to generate heat, because the electric current is big simultaneously, influences EMC characteristic.
The third scheme is as follows: a backlight driving circuit with constant voltage and constant current is adopted.
The advantages are that: stable work and good effect.
The disadvantages are as follows: the cost is high.
In a vehicle-mounted environment, the working voltage is fluctuant, 9V-16V is normal working voltage, the requirement of many automobile factories is increased to 6V-18V, and the following conclusion is obtained by analyzing the prior scheme:
1. if a stable voltage is obtained by means of voltage reduction, the obtained voltage is low in such a wide voltage range.
2. Since the LED voltage drops have individual differences, it is necessary to prevent excessive current from flowing through the LEDs. And the current-limiting resistor is connected in series, so that the energy efficiency is very low, and redundant energy efficiency is converted into heat energy. This is not only an energy inefficient problem, but also heat dissipation is a significant problem.
3. If the current limiting resistor is not used and the constant current source circuit is used for realizing, the energy efficiency is improved, but the cost is increased.
4. Power = voltage x current, achieving the same power, with lower voltages, requires more current. The lines flowing through then need to be thicker, requiring more board area.
5. Because of the larger current, EMC (electromagnetic compatibility) characteristics of the in-vehicle electronic equipment are deteriorated, and more cost is required to reduce electromagnetic interference.
The present application was made based on this.
SUMMERY OF THE UTILITY MODEL
In order to solve the above-mentioned defect that exists among the prior art, the utility model provides a LCD drive circuit that is shaded has quick response, integrality, safe and reliable, low cost's advantage.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
a liquid crystal display backlight drive circuit comprises a booster circuit connected with the positive pole of a vehicle-mounted storage battery power supply; the liquid crystal display comprises a plurality of LED diodes which are connected in series; the output end of the booster circuit is connected with the anode of the first LED diode of the liquid crystal display through a current-limiting resistor, and the cathode of the last LED diode is connected with the dimming circuit.
Further, the dimming circuit comprises a PWM signal capable of being controlled to change, a first resistor, a second resistor and an NPN triode; an emitting electrode of the NPN triode is grounded, a collector electrode of the NPN triode is connected with the negative electrode of the last LED diode, and a base electrode of the NPN triode is connected with the PWM signal through a first resistor; one end of the second resistor is connected with the base electrode of the NPN triode, and the other end of the second resistor is grounded.
After the technical scheme is adopted, compared with the prior art, the utility model, have following beneficial technological effect: the vehicle-mounted power supply circuit with the protection circuit has the advantages that the response frequency can reach more than 500kHz, and the quick response is realized; the circuit works completely, has complete constant voltage and constant current circuits, and has the advantages of completeness, stability and reliability; and has the advantages of low cost and the like.
Drawings
FIG. 1 is a circuit diagram of the LCD backlight driving circuit of the present invention (during boosting);
fig. 2 is a circuit diagram of the lcd backlight driving circuit of the present invention (after boosting).
Detailed Description
In order to make the technical means and technical effects achieved by the present invention clearer and more complete, an embodiment is provided, and the following detailed description is made with reference to the accompanying drawings:
as shown in fig. 1 and 2, a backlight driving circuit for a liquid crystal display of the present embodiment includes a voltage boosting circuit connected to the positive electrode of a vehicle-mounted battery power supply; the liquid crystal display comprises a plurality of LED diodes which are connected in series; the output end of the booster circuit is connected with the anode of the first LED diode of the liquid crystal display through a current limiting resistor R3, and the cathode of the last LED diode is connected with the dimming circuit. A stable boost voltage (LCD _ ILL _ VBOOST) is obtained through a boost circuit (boost circuit), power is supplied to the liquid crystal backlight LED through a current limiting resistor R3, and the current limiting resistor R3 can prevent the current flowing through the LED from being too large due to individual difference of LED voltage drops.
The dimming circuit comprises a PWM signal capable of being controlled to change, a first resistor R1, a second resistor R2 and an NPN triode; an emitting electrode of the NPN triode is grounded, a collector electrode of the NPN triode is connected with the negative electrode of the last LED diode, and a base electrode of the NPN triode is connected with the PWM signal through a first resistor; one end of the second resistor R2 is connected with the base of the NPN triode, and the other end of the second resistor R2 is grounded. The R1, R2 and Q1 combine a dimming control circuit, and the on and off of the current flowing through the Q1 are controlled by changing the PWM signal, so that the dimming control of the liquid crystal backlight LED is achieved.
The working principle of the embodiment is as follows:
1. in a vehicle-mounted environment, the operating voltage fluctuates, and under the condition that the power demand of the liquid crystal display driving circuit is large, the current demand can be reduced under the condition of the same power by boosting to a stable voltage.
2. After the driving voltage is increased, more LEDs can be connected in series due to the voltage drop of the LEDs, and the LEDs are connected in series with the current-limiting resistor and then driven together, so that the power loss is reduced, and the energy efficiency is improved.
3. Because in a LED branch road, the LED quantity that can drive increases, and the branch road of LED can reduce correspondingly, consequently has reduced actual electric current demand, and then has reduced the circuit design requirement, has reduced the size demand of circuit board.
4. The dimming control of the backlight driving of the liquid crystal display can be realized through the simple transistor (i.e., NPN transistor in the present embodiment) circuit and through the PWM.
The above is a detailed description of the technical solutions provided in connection with the preferred embodiments of the present invention, and it should not be assumed that the embodiments of the present invention are limited to the above description, and it will be apparent to those skilled in the art that the present invention can be implemented in a variety of ways without departing from the spirit and scope of the present invention.
Claims (2)
1. A liquid crystal display backlight driving circuit is characterized in that: the vehicle-mounted battery power supply comprises a booster circuit connected with the positive pole of a vehicle-mounted battery power supply; the liquid crystal display comprises a plurality of LED diodes which are connected in series; the output end of the booster circuit is connected with the anode of the first LED diode of the liquid crystal display through a current-limiting resistor, and the cathode of the last LED diode is connected with the dimming circuit.
2. A liquid crystal display backlight driver circuit as claimed in claim 1, wherein: the dimming circuit comprises a PWM signal capable of being controlled to change, a first resistor, a second resistor and an NPN triode; an emitting electrode of the NPN triode is grounded, a collector electrode of the NPN triode is connected with the negative electrode of the last LED diode, and a base electrode of the NPN triode is connected with the PWM signal through a first resistor; one end of the second resistor is connected with the base electrode of the NPN triode, and the other end of the second resistor is grounded.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020372189.8U CN211479626U (en) | 2020-03-23 | 2020-03-23 | LCD backlight drive circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202020372189.8U CN211479626U (en) | 2020-03-23 | 2020-03-23 | LCD backlight drive circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN211479626U true CN211479626U (en) | 2020-09-11 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202020372189.8U Active CN211479626U (en) | 2020-03-23 | 2020-03-23 | LCD backlight drive circuit |
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| Country | Link |
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| CN (1) | CN211479626U (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114495845A (en) * | 2022-02-11 | 2022-05-13 | 芜湖宏景电子股份有限公司 | Two-stage brightness control circuit of vehicle-mounted sound equipment product |
-
2020
- 2020-03-23 CN CN202020372189.8U patent/CN211479626U/en active Active
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN114495845A (en) * | 2022-02-11 | 2022-05-13 | 芜湖宏景电子股份有限公司 | Two-stage brightness control circuit of vehicle-mounted sound equipment product |
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Legal Events
| Date | Code | Title | Description |
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| GR01 | Patent grant | ||
| GR01 | Patent grant | ||
| CP03 | Change of name, title or address |
Address after: 312000 No.56 Shuguang Road, Keqiao Economic Development Zone, Shaoxing City, Zhejiang Province Patentee after: Yanfeng Visteon Yidong Automotive Electronics Co.,Ltd. Address before: 312030 No.56 Shuguang Road, Keqiao Economic Development Zone, Shaoxing City, Zhejiang Province Patentee before: YANFENG VISTEON BETUNG AUTOMOTIVE INSTRUMENT Co.,Ltd. |
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| CP03 | Change of name, title or address |