TW451074B - Adjustable backlight inverter - Google Patents

Abstract

The present invention relates to an adjustable backlight inverter, which uses the input voltage to adjust the maximum conduction interval of the internal frequency for changing the RC-voltage and current of the transformer's secondary side in the push-pull inverter, and therefore it is compatible to the different lamp's specifications.

Description

^ 451 07 4 ____ Case No. 89118892_Gallium ^ V. Description of the invention (1) [Scope of application of the invention] The present invention relates to an adjustable backlight inverter, which can be applied to display devices such as liquid crystal displays. [Background of the invention] Liquid crystal display (LCD) has the advantages of low power consumption, no radiation, full-plane display and small space. In terms of computer applications, LCD monitors have not only allowed the display screen of notebook computers to evolve from the early 9-inch VGA to the 13.1-inch XGa standard now, and "'f enters the field of larger monitors'." Replaces part of the cathode ray tube (CRT) market; applications for people's livelihoods such as car navigation systems, LCD TVs, etc. have also become feasible due to the liquid crystal display and high quality ^ Π 'LCD display is not The luminous display is not installed, and it requires a backlight to achieve the display function. The quality of the backlight source will directly affect the quality of the LCD display, except that the cost of the backlight source will account for 4 parts of the LCD module. High-definition, large-size liquid crystal displays' must be matched with high-performance backlight technology.

In the greedy technology, to convert the solid DC power to different DC or AC power, S inverter (inverter), especially the push-pull inverter Cpush-puU inverter, is most commonly used. The conventional push-pull converter has a fixed internal frequency and changes the external frequency with a control signal. As the inverter of the liquid as display still has no unified specifications, the industry needs to make different backlight converters to match the different lamp specifications of different brands of LCD monitors. The backlight converter 'stream n' is so diverse that it is difficult to control the inventory

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The monthly correction amount ’is not in line with economic benefits. To sum up, how to improve the backlight converter so that it has adjustment power can be applied to different lamp specifications is an urgent technical problem to be solved. [Summary of the invention] Herein, the present invention proposes an adjustable backlight converter that can adjust the maximum on-period of the internal frequency by using the external 4 voltage to change the resonance voltage and Resonant current, which makes Li comply with different lamp specifications. The detailed content and technology of the present invention are described below in conjunction with the drawings. [Detailed description of the invention] Please refer to the "Figure 1" waveform diagram of the analog dimming technique. After analog dimming, the amplitude of the lamp current I LAMP changes with the brightness control wheel-in voltage VBRITE. Please refer to "Figure 2" for the waveform diagram of the digital dimming technique. After digital dimming, the lamp current ILAMP changes with the pulse, and its duty cycle (duty eye I e) is controlled by the brightness control input voltage VBRITE. Regardless of analog dimming or digital dimming, the dimming is performed by changing the external frequency and the internal frequency remains unchanged, so its range of variation is limited. The industry needs to make different backlight converters to match the different lamp specifications required by different manufacturers of LCD monitors. As a result, there are many types of backlight converters, which are not economical. Please refer to "Figure 3" for the wiring diagram of the backlight inverter. The maximum on-period and step-up ratio of its internal frequency have been fixed 'cannot be adjusted' due to 451 Ο 7 4 _Case No. 89118892_Year Month Day_Amendment V. Description of the invention (3) Different backlighting needs to be designed for different lamp specifications Inverter line. Please refer to the "Figure 4" pinout diagram of the LX1 686 IC. The LX1686 integrated circuit has a total of 24 pins. 0 〇

First pin AOUT Second pin VSS_P Third pin VSS Fourth pin AFD_C Fifth pin RAMP_C Sixth pin RAMP_R Seventh pin FVERT Eighth pin FD_CR Ninth VCO_C Tenth pin BRT_POS Eleventh pin BRITE Twelfth pin DIG_DIM Thirteenth pin ENABLE Fourteenth pin I_R Fifteenth pin BRT Sixteenth pin VCOMP 17th pin VSNS 18th pin ICOMP 19th pin ISNS 20th pin OLSNS 21st pin TRI_C 22nd pin VDD A51074 8_ _a. Correction

Support pin VDD_P V. Description of the invention ¢ 4) Twentieth

Twenty-four pin BOUT, please refer to the "Simplified Figure 5" simplified circuit diagram of the LX1 686 integrated circuit

The LX1686 integrated circuit is an integrated circuit produced by LINFINITY. It uses a direct drive architecture. It cuts the frequency of the external frequency to change the current and control the output power. It can be used in cold cathode fluorescent lamps. lamp, referred to as CCFL

) Q LX 1 6 86 integrated circuit is mainly divided into five parts: 0 Bias generator 11, which can generate bias and bias current 'can be shut down by the enable input, and has a "lock below a specific voltage "(Under voltage lock out, UVL0 for short). Pulse width modulation slope generator (PWM ramp generator) 12 'The slope of the pulse width modulation is generated by the ramp oscillator' and is used in the cold cathode fluorescent lamp's startUp mode and Run mode (ruri mode) performs frequency sweep. Dimming controller (dimming contro 1) 1 3, has the function of locking the oscillation frequency according to the vertical scanning frequency of the LCD display, and can be switched-flow according to the MITE input, analog dimming or digital dimming according to the BRT input. 0 Pulse Width modulation controller (PWM controller) 14, has the function of stabilizing the transformer output voltage and lamp current. The output driver 15 receives the output voltage of the pulse width modulator ^ ^ ^ and generates signals such as AOUT and BOUT.

Month g__ a 4 51 ο Μ 89118892 V. Description of the invention (5) Please refer to the "Figure 6" block diagram of the adjustable backlight converter. The adjustable backlight converter of the present invention is a modification of the conventional backlight converter. The external voltage is used to adjust the maximum on-cycle of the internal frequency, and the resonance voltage and resonance current of the secondary side of the transformer in the push-pull converter are changed Make it meet different lamp specifications. Although the present invention takes the backlight converter composed of the L X1 6 8 6 integrated circuit as an example, but any device having the same function as the LX1 686 integrated circuit can be composed of a regulated backlight converter according to the technical content disclosed in this case. Device. Therefore, this case does not limit the LX1686 integrated circuit as a necessary limitation. Those with the same functions as the LX1 686 integrated circuit are commonly referred to as "driving devices". The invention is in addition to the driving device, plus some devices. The transistor 16 receives the aout, BOUT, VDD_P, GND_P and other signals output by the wheel-out driver 15 to generate an alternating voltage. The transistor may be a metal oxide field effect transistor (MOSFET). Use the transformer 17 to convert the alternating voltage to the load voltage to provide the backlight 21. When detected, the abnormality prevention device 18 is used to detect the load of the backlight 21 = the load of the light source 21 is too large, the backlight 21 is shorted. (〇pen) The load of the backlight 21 is 0, that is, the backlight 21 is short-circuited () to stop sl8 in an abnormal state and generate a trigger signal. > The delay time controller 19 is used to receive a trigger signal and generate a delay control k number and send it to the pulse width modulation controller 5. Since the display device does not have any display information during the start-up phase, the abnormality preventer 18 may mistakenly recognize it because no voltage is detected; therefore, the delay time is controlled by a short delay to avoid this situation. ^ #

Page 8 4 5 1 89118892 Main month: 佟 庀 __ * V. Description of the invention (6) ---- Please refer to "Figure 7" Circuit diagram of the adjustable backlight converter. The control voltage occ from the mainboard is attenuated by the resistor R39 and filtered by the capacitor C23. The resistors R46 and R46-1 have a voltage dividing effect in series. The resistor R46-1 and capacitor C24 form a filter to ease the output voltage generation and are less susceptible to noise interference. Please refer to "Figure 8" Circuit Diagram 2 of Adjustable Backlight Converter. VC0MP is the sixteenth pin of the LX1686 integrated circuit and can be used to adjust the maximum on-cycle of the internal frequency. VSNS is the seventeenth pin of the LX 1 686 integrated circuit. Its voltage is compared with the reference potential of 1.25V. If VSNS is higher than 1. 25V ’VC0MP becomes a low potential and overvoltage protection is applied. The sixteenth pin and the seventeenth pin of the LX1 686 integrated circuit VSNS ground 'VC0MP can maintain a high potential. The maximum on-period of the internal frequency can be adjusted by an external voltage. When it is detected that any lamp does not have the correct feedback voltage, its voltage is lower than the voltage of the sixth and fourth pins of U2. Then the first and second pins of U2, ADUT, and the second pin of VSS — P goes to a low potential, and the twentieth pin CLSNS is controlled by the frequency-triggering trigger via resistor η 6. The trigger time is determined by capacitor Ci8 and resistor R29. If the charging voltage of the capacitor C1 8 and the resistor R 2 9 is less than the eleventh pin, the thirteenth pin 0ABLE is completely released, and the external voltage is supplied through the resistor ri 7 (; the sixteenth pin VC0MP is supplied; If the charging voltage of capacitor C18 and resistor R29 is greater than or equal to the eleventh pin BRITE, the thirteenth pin ENABLE becomes a low potential, which locks the LX1 686 integrated circuit and opens or shorts ( short circuit).

Heart 1 0 she 89118892_ year, month, day ___ V. Description of the invention (7) When the resistor R1 and capacitor C2 are charged. The time constant is between 80msec and 100msec, that is, delaying 80msec to 100msec before the integrated circuit starts to operate. Avoid incomplete pictures on the LCD before data is entered. Please refer to "Figure 9", "Figure 10" and "Figure 11" of the wheel output current waveform of the adjustable backlight inverter. From "Fig. 9", it can be seen that the output current waveform of the adjusted backlight converter has a characteristic that the pulse width becomes smaller. That is, the maximum on-period of the internal frequency is controlled by the external voltage ^ "Fig. 10" is the minimum pulse width The output waveform of the period. "Figure 11" shows that the pulse width is reduced 'and the output waveform is the current waveform of the lamp. y [Effect of the invention] The adjustable backlight converter of the present invention can adjust the maximum on-period of the internal frequency by using an external voltage, and change the resonance voltage and resonance current of the secondary side of the transformer in the push-pull converter to make it Backlight converters that meet the specifications of different lighting camps. The invention has the advantage that it can be applied to different lamp specifications without the need to modify the circuit. Therefore, it can be manufactured in large quantities and adjusted according to actual needs, which can greatly reduce inventory pressure. "Although the invention is disclosed above with the foregoing preferred embodiments, It is not intended to limit the present invention. "Any person skilled in the art can make some modifications and retouching without departing from the spirit and scope of Ming Ming. Therefore, the scope of protection of the present invention shall be defined by the scope of the attached patent application. Whichever comes first.

45107 4 _Case No. 89118892_Year Month and Day ___ Brief Description of Drawings [Simple Description of Drawings] Figure 1 is a waveform diagram of analog dimming in the conventional technology. FIG. 2 is a waveform diagram of digital dimming according to the conventional technology. Figure 3 is a circuit diagram of a conventional backlight inverter. Figure 4 shows the pinout of the LX1 686 integrated circuit. Figure 5 is a simplified circuit diagram of the LX1686 integrated circuit. Figure 6 is a block diagram of an adjustable backlight inverter. Figure 7 is the first circuit diagram of the adjustable backlight inverter. Figure 8 is the second circuit diagram of the adjustable backlight converter. Figure 9 is one of the output current waveforms of the adjustable backlight inverter. Figure 10 is the second output current waveform of the adjustable backlight converter. Figure 11 is the third output current waveform of the adjustable backlight converter. [Illustration of symbols] 11 'Bias generator 12 Pulse width modulation slope generator 13 Dimming controller 14 Pulse width modulation controller 15 Output driver 16 Transistor 17 Transformer ~ t) 18 Anomaly preventer 19 Delay time controller 21 load

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Claims (1)

451074 __Case No. 89118892_Year Month Day __ VI. Scope of Patent Application 1. An adjustable backlight converter that converts DC voltage to provide a backlight source for AC voltage and can be used according to the brightness control signal and The load control signal adjusts the AC voltage, including at least: a transistor to receive the driving voltage to generate an alternating voltage; a transformer to convert the alternating voltage to the load voltage to provide the use of the backlight; an abnormality preventer To detect the load of the backlight source, a trigger signal is generated when the load is abnormal; a delay time controller 'is used to receive the trigger signal to provide a certain delay time and generate a delay control signal; and & a driving device that receives the brightness control signal, A load control signal, a delay control signal, and a load feedback signal to generate a driving voltage include: a bias generator 'for generating a bias voltage and a bias current; a dimming controller' for receiving a brightness control signal and the bias Voltage for generating dimming voltage; pulse width modulation slope generator, receiving bias for generating pulse wave Degree control voltage; a pulse width modulation controller, which receives the bias voltage, the photoelectric modulation f, the load controller signal, the load feedback control signal, and the delay control signal (the pulse width control voltage is used to generate the control voltage) And the output driver 'receives the control voltage to generate a driving voltage. As described in the first patent application, the adjustable backlight inverter, the driver Page 12 4§1 074 Case No. 89118892 Revised Page 13