CN101998720A - Circuit for improving conversion efficiency of LEDs by using inductance type converter - Google Patents
Circuit for improving conversion efficiency of LEDs by using inductance type converter Download PDFInfo
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- CN101998720A CN101998720A CN2009100134147A CN200910013414A CN101998720A CN 101998720 A CN101998720 A CN 101998720A CN 2009100134147 A CN2009100134147 A CN 2009100134147A CN 200910013414 A CN200910013414 A CN 200910013414A CN 101998720 A CN101998720 A CN 101998720A
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- led
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- conversion efficiency
- leds
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Abstract
The invention relates to a circuit for improving conversion efficiency of LEDs by using an inductance type converter, belonging to a power supply technology, in particular to a technology for improving conversion efficiency of the LEDs by using the inductance type converter. The invention provides a technology for ensuring that all LED strings are connected in parallel inside and then connected to a single power supply to reduce connecting points. When an LED drive IC is selected, key parameters comprises switching current limits, maximum output voltage and overvoltage protection threshold required for protecting open-circuit LED conditions.
Description
Technical field:
The invention belongs to a kind of power technology, relate to a kind of circuit that utilizes the raising LED conversion efficiency of inductive type transducer.
Background technology:
The extensive use of LED in the LCD of mobile phone is backlight had the several years.Nowadays it is used and is just expanding to large-area LCD application, comprises pocket PC, auto navigation GPS, digital frame, Portable DVD and even mobile computer.LED is also just beginning to replace conventional incandescent and halogen light source family expenses, automobile and other general light source.This trend actuating force behind is the quick progress of technology, comprises that LED is brighter, and efficient is higher, and price has more competitiveness.In fact using the reason of LED very simple, is exactly that they have high reliability and longer life-span, provides non-maintaining product in the place that does not need to change for the terminal use.
In order to provide backlight uniformly in LCD uses, several White LEDs are installed along the limit of LCD usually.The quantity of LED is proportional to the size of LCD.For medium size (7-10 inch), use 20-40 LED usually altogether.These LED are connected to parallel 3 or more LED string usually.
Content of the present invention:
The present invention is exactly at the problems referred to above, provides a kind of in order to reduce tie point, makes all LED string parallel connections in inside, is connected to a technology on the single supply then.
For achieving the above object, the present invention adopts following technical scheme, and the present invention is when selecting the LED drive IC, and key parameter comprises the switching current limit, maximum output voltage, and the required overvoltage protection threshold value of open circuit LED condition that needs protection.
Beneficial effect of the present invention:
LED forward voltage (VF), the various combination of LED electric current and supply voltage scope has determined the type of required inductive type conversion LED driver, LED VF changes along with electric current, temperature and the different of LED model.Maximum VF when appearing at minimum temperature is a key parameter of selecting the led drive circuit structure, normally selects in linear structure, buck or boost structure.Can make all LED string parallel connections like this, be connected to then on the single supply, reach the effect that tie point reduces in inside.
Description of drawings:
Fig. 1 is circuit theory diagrams of the present invention.
Embodiment:
The present invention is when selecting the LED drive IC, and key parameter comprises the switching current limit, maximum output voltage, and the required overvoltage protection threshold value of open circuit LED condition that needs protection.
Embodiment 1: the LCD module with 8 inch is an example, comprises (Fig. 1) backlight of 9 string (3 of every strings) White LEDs compositions altogether.The total voltage (VF of LED is 3.3V) of LED string is generally 10V (3 * 3.3V).The electric current of every LED is 20mA, and then total drive current is 180mA (9 * 20), and the LED total power consumption is 1.8W.Provide a 5V power supply with an AC power supplies adapter.Led driver based on inductance is highly suitable for this application.
At first the load of computing 2W needs great switching current.Suppose that efficient is 80%, input current equals Vout * Iout/Vin * efficient=10 * 0.18/5 * 0.8=450mA.The CAT4139 inductive type led driver that boosts has the driving force of 750mA (minimum value), so be well suited for this application.
The current rating of inductance should be able to be handled LED and drive peak switch current and do not enter saturated.In case occur saturatedly, the electric current surging will appear because this moment inductance function just become a resistance, circuit is no longer according to expection work.Suitable inductance rated current should be more than or equal to 80mA.
The maximum output voltage of duration of work LED should be lower than specified maximum output voltage.Because 3 LED series connection, under cold temperature, total forward voltage may be up to 11.4V (3 * 3.8V).The open circuit LED detection threshold of 24V is far above its limiting value.If LED disconnects, output voltage will rise and remain on 30V, and this moment, assembly was in low-power mode, and the electric current that receives from power supply only has several milliamperes.The electric capacity of 30V rated output voltage is suitable.
Consider a 6W LED lamp now by the power supply of 12V power supply.Can be connected in series with 6 high brightness White LEDs and realize, drive with the fixed current of a 300mA, typical forward voltage is 3.3V.
Claims (2)
1. a circuit that utilizes the raising LED conversion efficiency of inductive type transducer is characterized in that key parameter comprises the switching current limit, maximum output voltage when selecting the LED drive IC, and the required overvoltage protection threshold value of open circuit LED condition that needs protection.
2. a kind of raising LED conversion efficiency of utilizing the inductive type transducer according to claim 1 be the road, it is characterized in that the total voltage VF of LED string is 10V (3 * 3.3V).
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100134147A CN101998720A (en) | 2009-08-26 | 2009-08-26 | Circuit for improving conversion efficiency of LEDs by using inductance type converter |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN2009100134147A CN101998720A (en) | 2009-08-26 | 2009-08-26 | Circuit for improving conversion efficiency of LEDs by using inductance type converter |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN101998720A true CN101998720A (en) | 2011-03-30 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN2009100134147A Pending CN101998720A (en) | 2009-08-26 | 2009-08-26 | Circuit for improving conversion efficiency of LEDs by using inductance type converter |
Country Status (1)
| Country | Link |
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| CN (1) | CN101998720A (en) |
Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018126494A1 (en) * | 2017-01-04 | 2018-07-12 | 深圳市华星光电技术有限公司 | Led backlight driving circuit and liquid crystal display |
-
2009
- 2009-08-26 CN CN2009100134147A patent/CN101998720A/en active Pending
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| WO2018126494A1 (en) * | 2017-01-04 | 2018-07-12 | 深圳市华星光电技术有限公司 | Led backlight driving circuit and liquid crystal display |
| US10446090B2 (en) | 2017-01-04 | 2019-10-15 | Shenzhen China Star Optoelectronics Technology Co., Ltd | LED backlight driving circuit and liquid crystal display |
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Legal Events
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| C06 | Publication | ||
| PB01 | Publication | ||
| C02 | Deemed withdrawal of patent application after publication (patent law 2001) | ||
| WD01 | Invention patent application deemed withdrawn after publication |
Application publication date: 20110330 |