CN201780764U - Special backlight driving circuit based on FPGA - Google Patents
Special backlight driving circuit based on FPGA Download PDFInfo
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- CN201780764U CN201780764U CN2010202893681U CN201020289368U CN201780764U CN 201780764 U CN201780764 U CN 201780764U CN 2010202893681 U CN2010202893681 U CN 2010202893681U CN 201020289368 U CN201020289368 U CN 201020289368U CN 201780764 U CN201780764 U CN 201780764U
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Abstract
The utility model discloses a special backlight driving circuit based on an FPGA, which comprises a main controller, a multi-bit A/D converter, a first MOS transistor and a second MOS transistor, wherein the main controller consists of an FPGA chip, and the first MOS transistor and the second MOS transistor are respectively connected with backlight connecting terminals in a one-to-one corresponding manner. Voltage feedback, circuit feedback and brightness signals are led into the A/D converter in communication connection with the FPGA chip, and the FPGA is in communication with a user by the aid of an RS232. The special backlight driving circuit can control PWM dimming duty ratio according to feedback values of a brightness sensor by setting brightness values in various brightness levels, thereby ensuring stable backlight brightness.
Description
Technical field
The utility model relates to field of liquid crystal, and especially aviation is specially a kind of extraordinary backlight source driving circuit based on FPGA with the driving circuit field of colour liquid crystal display device.
Background technology
Along with the maturation of LED technology and declining to a great extent of cost, LED has become a kind of trend as backlight.At civil area, the LED-backlit source driving circuit often adopts the LED integrated drive chips.Have the extraordinary application of high brightness ratio at backlight, integrated drive chips is under constant current work, and the output current instability during low-light level under the narrow PWM Waveform Control can cause flicker.Therefore in the application scenario with high brightness ratio backlight, also to increase process auxiliary drive, but do the complexity that has strengthened driving circuit like this, also improve the cost of LED.
The utility model content
The purpose of this utility model provides a kind of extraordinary backlight source driving circuit based on FPGA, adopts the LED integrated drive chips can cause the LED flicker to solve, and needs to increase the problem of process auxiliary drive.
In order to achieve the above object, the technical scheme that the utility model adopted is:
Extraordinary backlight source driving circuit based on FPGA, it is characterized in that: comprise the master controller that constitutes by fpga chip, the A/D converter of multidigit, also include first, second metal-oxide-semiconductor, the grid of described first metal-oxide-semiconductor is electrically connected with a PWM output interface of described fpga chip by buffer circuit, the source ground of first metal-oxide-semiconductor, drain electrode is introduced external voltage by inductance respectively, insert terminals of backlight by diode, the also drop-down voltage sample resistance that is connected to series connection on the lead between the corresponding terminals of described first metal-oxide-semiconductor and backlight, and between voltage sample resistance, lead to the sampling lead and be connected to an input end of described A/D converter, the grid of described second metal-oxide-semiconductor is electrically connected with another PWM output interface of described fpga chip by buffer circuit, the drain electrode of second metal-oxide-semiconductor is electrically connected with another terminals of described backlight, the source electrode of second metal-oxide-semiconductor is connected to current sampling resistor, and draw the sampling lead from described current sampling resistor and be connected to another input end of described A/D converter, also be connected to luminance sensor on the input end on the described A/D converter, the output terminal of A/D converter is electrically connected with the signal input interface of described fpga chip.
Described extraordinary backlight source driving circuit based on FPGA is characterized in that: described fpga chip is connected with outside upper machine communication by its RS232 interface.
The utility model is used for driving LED lamp string group, has overvoltage protection and constant current function, adopts the PWM dimming mode, only work when the PWM light modulation is effective of booster circuit.Rationally be provided with the metal-oxide-semiconductor opening and closing time in the circuit, eliminated ground bullet noise, improved the electromagnetic compatibility effect.The utility model can according to the value of feedback of luminance sensor, be controlled PWM light modulation dutycycle by setting the brightness value under the various gray scales, thereby guarantees that backlight illumination is stable.
Description of drawings
Fig. 1 is the utility model schematic block circuit diagram.
Fig. 2 is the utility model PWM light modulation oscillogram.
Fig. 3 is the utility model PWM oscillogram of boosting.
Embodiment
As shown in Figure 1.Extraordinary backlight source driving circuit based on FPGA comprises the master controller that is made of fpga chip, 12 A/D converter, and fpga chip is connected with the upper machine communication of external user by its RS232 interface.Also include first, the second metal-oxide-semiconductor T1, T2, the grid of the first metal-oxide-semiconductor T1 is electrically connected with a PWM output interface of fpga chip by buffer circuit, the source ground of the first metal-oxide-semiconductor T1, drain electrode is introduced external voltage Vin by inductance L 1 respectively, insert terminals of backlight by diode D, the also drop-down voltage sample resistance R 1 that is connected to series connection on the lead between the corresponding terminals of the first metal-oxide-semiconductor T1 and backlight, R2, and in voltage sample resistance R 1, lead to the sampling lead between the R2 and be connected to an input end of A/D converter, the grid of the second metal-oxide-semiconductor T2 is electrically connected with another PWM output interface of fpga chip by buffer circuit, another terminals of the drain electrode of the second metal-oxide-semiconductor T2 and backlight are electrically connected, the source electrode of the second metal-oxide-semiconductor T2 is connected to current sampling resistor R3, and draw the sampling lead from current sampling resistor R3 and be connected to another input end of A/D converter, also be connected to luminance sensor on the input end on the A/D converter, the output terminal of A/D converter is electrically connected with the signal input interface of fpga chip.As controller, working current, PWM light modulation waveform are set in the mode instruction round the clock and the order of light modulation progression of sending by the RS232 interface communication according to the user with fpga chip, the boost dutycycle of waveform of control PWM.Luminance sensor judges whether backlight illumination is stable under the pattern in daytime, is the foundation of brilliance control.
As Fig. 2, shown in Figure 3.According to user's light modulation instruction, FPGA sends PWM light modulation waveform.The PWM waveform that boosts only just occurs when the light modulation waveform is high level, and its dutycycle is determined by working current.
In order to reach the job stability of intelligent drive circuit, adopt following measure:
1, the A/D converter behind the current sample is 12 at least
Voltage on the general current sampling resistor is about 200mv, and the reference voltage of A/D converter is 1.2V, and the digital quantity after the conversion is about 170.The output current variable quantity is 1 o'clock, only accounts for 1/170 of total current, and human eye can not obviously be discovered.
2, pattern working current and working method are different round the clock
Extraordinary display will be obtained the screen brightness ratio and be up to 10000: 1, and Switching Power Supply is only just worked when light modulation PWM is high level.In order to guarantee that Switching Power Supply has the working time in 2 cycles (5us), the minimum duty time of light modulation PWM waveform is 10us.
Daytime pattern go out to shield maximum brightness with daytime pattern go out to shield the ratio of minimum brightness (1000nit: 5nit) as can be known, the light modulating frequency maximum be 500Hz.
If the pattern working current is the same round the clock, satisfy simultaneously daytime pattern go out to shield maximum brightness (1000nit) and night pattern go out to shield minimum brightness (0.1nit), then light modulating frequency has only 1/100000us=10Hz, this can cause flicker backlight.So the pattern working current must be different round the clock.
Night pattern go out to shield maximum brightness with night pattern go out to shield minimum brightness ratio (20nit: 0.1nit) as can be known, daytime pattern go out to shield high-high brightness be night pattern go out to shield 50 times of high-high brightness.Night, the pattern working current was too small,
If adopt the constant current working method, a little less than the antijamming capability, easily cause flicker backlight.Therefore under the night pattern, Switching Power Supply is with fixing very little dutycycle work.
3, control mode
Under the daytime pattern, the backlight illumination height, the LCD temperature rise is fast, and drive current needs constant.The dutycycle of boosting of by-pass cock power supply, make output current setting value ± 1% in, the adjustment of the dutycycle of boosting is with each variable quantity adjustment that only increases or reduce digital quantity 1, promptly the duty time only increases or reduces 15ns (crystal oscillator is 65M) at every turn.
Under the daytime pattern, even the LED lamp is operated in current constant mode, its luminosity also can increase and reduce along with temperature backlight, and is under daytime pattern higher brightness situation, particularly evident.According to the backlight illumination of luminance sensor perception, backlight illumination database under the different light modulation progression in the binding data storehouse, the dutycycle of control light modulation PWM waveform, thus stablize backlight illumination.
4, over-voltage protecting function
Open when carrying when Switching Power Supply, current sampling data is 0, can cause the output voltage of Switching Power Supply too high, can damage the electric capacity of output voltage smoothing effect.Set in FPGA, in case output voltage surpasses certain abnormal voltage, Switching Power Supply just quits work.
Claims (2)
1. based on the extraordinary backlight source driving circuit of FPGA, it is characterized in that: comprise the master controller that constitutes by fpga chip, the A/D converter of multidigit, also include first, second metal-oxide-semiconductor, the grid of described first metal-oxide-semiconductor is electrically connected with a PWM output interface of described fpga chip by buffer circuit, the source ground of first metal-oxide-semiconductor, drain electrode is introduced external voltage by inductance respectively, insert terminals of backlight by diode, the also drop-down voltage sample resistance that is connected to series connection on the lead between the corresponding terminals of described first metal-oxide-semiconductor and backlight, and between voltage sample resistance, lead to the sampling lead and be connected to an input end of described A/D converter, the grid of described second metal-oxide-semiconductor is electrically connected with another PWM output interface of described fpga chip by buffer circuit, the drain electrode of second metal-oxide-semiconductor is electrically connected with another terminals of described backlight, the source electrode of second metal-oxide-semiconductor is connected to current sampling resistor, and draw the sampling lead from described current sampling resistor and be connected to another input end of described A/D converter, also be connected to luminance sensor on the input end on the described A/D converter, the output terminal of A/D converter is electrically connected with the signal input interface of described fpga chip.
2. the extraordinary backlight source driving circuit based on FPGA according to claim 1 is characterized in that: described fpga chip is connected with outside upper machine communication by its RS232 interface.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010202893681U CN201780764U (en) | 2010-08-05 | 2010-08-05 | Special backlight driving circuit based on FPGA |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2010202893681U CN201780764U (en) | 2010-08-05 | 2010-08-05 | Special backlight driving circuit based on FPGA |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN201780764U true CN201780764U (en) | 2011-03-30 |
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| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2010202893681U Expired - Lifetime CN201780764U (en) | 2010-08-05 | 2010-08-05 | Special backlight driving circuit based on FPGA |
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| Country | Link |
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| CN (1) | CN201780764U (en) |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103177698A (en) * | 2013-03-27 | 2013-06-26 | 深圳市华星光电技术有限公司 | Light-emitting diode (LED) backlight driving circuit and backlight module |
| CN104823523A (en) * | 2012-07-24 | 2015-08-05 | 启迪公司 | Distributed lighting control |
-
2010
- 2010-08-05 CN CN2010202893681U patent/CN201780764U/en not_active Expired - Lifetime
Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN104823523A (en) * | 2012-07-24 | 2015-08-05 | 启迪公司 | Distributed lighting control |
| CN103177698A (en) * | 2013-03-27 | 2013-06-26 | 深圳市华星光电技术有限公司 | Light-emitting diode (LED) backlight driving circuit and backlight module |
| CN103177698B (en) * | 2013-03-27 | 2016-02-03 | 深圳市华星光电技术有限公司 | A kind of LED backlight drive circuit and backlight module |
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Legal Events
| Date | Code | Title | Description |
|---|---|---|---|
| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term | ||
| CX01 | Expiry of patent term |
Granted publication date: 20110330 |