CN102682714A - LED backlight source driving circuit and method for realizing soft startup - Google Patents
LED backlight source driving circuit and method for realizing soft startup Download PDFInfo
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Abstract
The invention discloses an LED (light-emitting diode) backlight source driving circuit and a method for realizing soft startup. The method comprises the steps as follows: an error amplifier output pin of a control circuit driving chip is earthed by a drain resistor; when a flat television mainboard rapidly resets the driving chip by an enabling pin of the driving chip, the voltage of the driving chip error amplifier output pin is rapidly drained by the drain resistor; and when the driving chip is restarted, the voltage of the error amplifier output pin rises from zero, and the duty ratio of PWM (pulse width modulation) signal output by the driving chip is slowly increased, so that a soft startup function of the whole circuit is realized. According to the invention, the soft startup function of the driving chip can be easily realized, and the accident damage of main circuit power devices caused by over-high voltage, current and temperature stress is prevented.
Description
[technical field]
The present invention relates to flat panel TV LED-backlit source, relate in particular to a kind of LED-backlit source driving circuit and the method that realizes soft start.
[background technology]
Traditional flat panel TV LED-backlit source driving circuit comprises main circuit and control circuit; Main circuit comprises direct-flow input circuit, energy storage inductor, switching tube, RC stress absorption circuit and output rectifier and filter, and output rectifier and filter comprises commutation diode and filter capacitor.Control circuit comprises chip for driving, chip power supply circuit, output voltage sampling circuit, output current sample circuit, PWM light adjusting circuit and enable circuits.
In classic flat-plate TV LED-backlit source driving circuit; The dutycycle of the pwm signal of chip for driving (like BIT3251) output and the proportional relation of output pin voltage of chip for driving error amplifier; The voltage of error amplifier output pin is high more, and the dutycycle of pwm signal is just big more.This traditional circuit has following two problems.
One of which: when main circuit output terminal open circuit or loose contact; The current sample feedback loop does not have signals collecting to return the error amplifier anti-phase input pin to chip for driving, and at this moment the anti-phase input pin voltage of error amplifier is far below the positive input pin voltage (reference voltage) of error amplifier, according to this error amount; The output voltage of error amplifier will be adjusted to mxm.; If enable the quick reset drives chip of pin at flat panel TV mainboard at this moment through chip for driving, the voltage of chip for driving error amplifier output pin can't be fallen in the extremely short time, keeps the value before resetting; Therefore in chip for driving during from new startup; It is maximum that the pwm signal dutycycle of chip for driving output pin reaches, and control circuit has lost the soft function that opens, and main circuit will damage owing to superpotential, current stress cause power semiconductor device.
Its two: when LED-backlit source driving circuit operate as normal; If the flat panel TV mainboard enables the quick reset drives chip of pin through chip for driving; The voltage of chip for driving error amplifier output pin can't be fallen in the extremely short time; Keep the value before resetting, therefore in chip for driving during from new startups, the pwm signal dutycycle of chip for driving output pin is kept the preceding value that resets; Control circuit has lost the soft function that opens, and main circuit will damage owing to superpotential, current stress cause power semiconductor device.
[summary of the invention]
The technical matters that the present invention will solve provides a kind of control circuit and realizes the soft function that opens, and makes the non-damageable flat panel TV LED-backlit of main circuit power semiconductor device source driving circuit realize the method for soft start.
Another technical matters that will solve of the present invention provides a kind of control circuit and realizes the soft function that opens, and makes the non-damageable LED-backlit source driving circuit of main circuit power semiconductor device.
In order to solve the problems of the technologies described above; The technical scheme that the present invention adopts is, a kind of flat panel TV LED-backlit source driving circuit is realized the method for soft start, with the error amplifier output pin of control circuit chip for driving through bleeder resistance ground connection; When the flat panel TV mainboard enables pin when fast chip for driving being resetted through chip for driving; The voltage of chip for driving error amplifier output pin is released through bleeder resistance fast, chip for driving when restarting, the rising of starting from scratch of the voltage of error amplifier output pin; The dutycycle of the pwm signal of chip for driving output slowly increases, and makes entire circuit realize the soft function that opens.
A kind of technical scheme of flat panel TV LED-backlit source driving circuit is; Comprise main circuit and control circuit; Main circuit comprises direct-flow input circuit, energy storage inductor, switching tube, RC stress absorption circuit and output rectifier and filter, and output rectifier and filter comprises commutation diode and filter capacitor; Control circuit comprises chip for driving, chip power supply circuit, output voltage sampling circuit, output current sample circuit, PWM light adjusting circuit, enable circuits and current sample ring compensating circuit; Described current sample ring compensating circuit comprises first resistance, bleeder resistance, first electric capacity and second electric capacity, is connected on after described first resistance and first capacitances in series between the error amplifier anti-phase input pin and error amplifier output pin of chip for driving; Described second electric capacity is connected between the error amplifier anti-phase input pin and error amplifier output pin of chip for driving; The error amplifier output pin of one termination chip for driving of said bleeder resistance, other end ground connection.
Above-described flat panel TV LED-backlit source driving circuit; Described enable circuits comprises the 3rd resistance, the 4th resistance and the 3rd electric capacity; The backlight switch signal output part of one termination TV SKD of said the 3rd resistance, another termination chip for driving enable control pin; Described the 4th resistance one termination chip for driving enable control pin, other end ground connection; Described the 3rd electric capacity and the 4th resistance also connect.
Above-described flat panel TV LED-backlit source driving circuit; Described PWM light adjusting circuit comprises the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance, the 9th resistance, first triode and diode; The collector of first triode connects chip power positive pole, grounded emitter through the 8th resistance; The anode of diode connects the collector of first triode, and negative electrode connects the error amplifier anti-phase input pin of chip for driving through the 9th resistance; One termination TV SKD pwm control signal output terminal of the 5th resistance, the base stage of another termination first triode; The base stage of one termination, first triode of the 6th resistance, other end ground connection; One termination TV SKD pwm control signal output terminal of the 7th resistance, the collector of another termination first triode.
Above-described flat panel TV LED-backlit source driving circuit, described chip power supply circuit comprises linear voltage-stabilizing circuit, the described direct-flow input circuit of input termination of said linear voltage-stabilizing circuit, the supply pin of another termination chip for driving.
Above-described flat panel TV LED-backlit source driving circuit; Described linear voltage-stabilizing circuit comprises second triode, stabilivolt, the 4th electric capacity, the tenth resistance and the 11 resistance; The emitter of second triode connects the chip for driving supply pin; Base stage connects the negative electrode of stabilivolt, and collector connects the direct-flow input circuit positive pole through the 11 resistance; The plus earth of stabilivolt, a termination direct-flow input circuit of the tenth resistance is anodal, the base stage of another termination second triode; The emitter of one termination, second triode of the 4th electric capacity, other end ground connection.
Above-described flat panel TV LED-backlit source driving circuit; Described output current sample circuit comprises the 12 resistance and the 13 resistance; The negative pole of flat panel TV LED-backlit source driving circuit output terminal connects the error amplifier anti-phase input pin of chip for driving through the 12 resistance eutral grounding through the 13 resistance.
Above-described flat panel TV LED-backlit source driving circuit; Said voltage sampling circuit comprises the 14 resistance, the 15 resistance and the 5th electric capacity; The positive pole of one termination flat panel TV LED-backlit source driving circuit output terminal of the 14 resistance, the overvoltage protection pin of another termination chip for driving; The overvoltage protection pin of one termination chip for driving of the 15 resistance, other end ground connection, the 5th electric capacity and the parallel connection of the 15 resistance.
Above-described flat panel TV LED-backlit source driving circuit comprises the 16 resistance, the positive pole of the said direct-flow input circuit of first termination of energy storage inductor, and second termination connects first end of switching tube; The second end ground connection of switching tube, the control utmost point of switching tube connects the output terminal of chip for driving through the 16 resistance; The anode of commutation diode connects first end of switching tube, and negative electrode connects the positive pole of flat panel TV LED-backlit source driving circuit output terminal; The negative electrode of one termination commutation diode of filter capacitor, other end ground connection, the grounding leg ground connection of chip for driving.
Above-described flat panel TV LED-backlit source driving circuit, described RC stress absorption circuit comprises the 17 resistance and the 6th electric capacity, a termination connects first end of switching tube after the 17 resistance and the 6th capacitances in series, other end ground connection.
LED-backlit source driving circuit of the present invention can be realized the chip for driving soft start function smoothly, prevents that the main circuit power device is because of voltage, electric current, the excessive accidental damage of temperature stress.
[description of drawings]
Below in conjunction with accompanying drawing and embodiment the present invention is done further detailed explanation.
Fig. 1 is the schematic diagram of flat panel TV LED-backlit source driving circuit embodiment of the present invention.
[embodiment]
As shown in Figure 1; The flat panel TV LED-backlit source driving circuit of the embodiment of the invention comprises main circuit and control circuit; Main circuit comprises direct-flow input circuit, energy storage inductor L5, switching tube Q29, RC stress absorption circuit and output rectifier and filter, and output rectifier and filter comprises commutation diode D14 and filter capacitor C32 and EC18.Control circuit comprises chip for driving IC6 (model BIT3251), chip power supply circuit, output voltage sampling circuit, output current sample circuit, PWM light adjusting circuit, enable circuits and current sample ring compensating circuit.
The chip for driving of present embodiment is LED constant current pwm chip BIT3251, and chip BIT3251 peripheral circuit is simple, device is less, cost performance is high, can realize that the high precision constant current mode comes driving LED work backlight.
The positive pole of the first termination direct-flow input circuit of energy storage inductor L5 (+24V or+12V), second termination connects first end of switching tube Q29.The second end ground connection of switching tube Q29, the control utmost point of switching tube Q29 connect the output terminal (the 8th pin OUT) of chip for driving IC6 through resistance R 120.The anode of commutation diode D14 connects first end of switching tube Q29, and negative electrode meets the anodal LED+ of flat panel TV LED-backlit source driving circuit output terminal.The negative electrode of the termination commutation diode D14 of filter capacitor C32 and EC18, other end ground connection, the grounding leg of chip for driving IC6 (the 7th pin GND) ground connection.
RC stress absorption circuit comprises resistance R 117 and capacitor C 34, and a termination connect first end of switching tube Q29, other end ground connection after resistance R 117 was connected with capacitor C 34.
Current sample ring compensating circuit is connected across between the error amplifier anti-phase input pin (the 4th pin INN) of error amplifier output pin (the 3rd pin CMP) and IC6 of chip for driving IC6.
Current sample ring compensating circuit comprises resistance R 23, bleeder resistance R23B, capacitor C 27 and capacitor C 26, between the error amplifier anti-phase input pin (the 4th pin INN) of resistance R 23 and error amplifier output pin (the 3rd pin CMP) that is connected on chip for driving IC6 after capacitor C 27 is connected and IC6.Capacitor C 26 is connected between the error amplifier anti-phase input pin (the 4th pin INN) of error amplifier output pin (the 3rd pin CMP) and IC6 of chip for driving IC6.The error amplifier output pin of the termination chip for driving IC6 of bleeder resistance R23B (the 3rd pin CMP), other end ground connection.
This circuit is except the current sample feedback loop has adopted traditional first order pole, simple zero compensation, and also the error amplifier output pin (the 3rd pin CMP) at chip for driving IC6 has connected bleeder resistance R23B to ground.Under states such as main circuit output terminal open circuit, loose contact or operate as normal; When the flat panel TV mainboard enables pin when fast chip for driving IC6 being resetted through chip for driving IC6; Through this resistance, can the voltage of chip for driving IC6 error amplifier output pin (the 3rd pin CMP) be released fast, chip for driving IC6 is when restarting; The voltage of error amplifier output pin (the 3rd pin CMP) slowly rises from zero; The dutycycle of the pwm signal of chip for driving IC6 output slowly increases, thereby makes entire circuit realize the soft function that opens, and avoids power semiconductor device owing to superpotential, current stress puncture.
Enable circuits comprises resistance R 24, resistance R 23A and capacitor C 24, the backlight switch signal output part (BK/ON) of a termination flat panel TV mainboard of resistance R 24, and another termination chip for driving IC6 enables control pin (the 2nd pin EA).Resistance R 23A one termination chip for driving IC6 enables control pin (the 2nd pin EA), other end ground connection.Capacitor C 24 and resistance R 23A also connect.R23A R24, C24 have formed switch backlight (BK/ON) control circuit.The sequential actual according to the flat panel TV mainboard, the startup sequential that the resistance of adjusting R23A R24 can be regulated chip for driving IC6 reaches and avoids televisor when switching on and shutting down, to produce flower screen and mosaic phenomenon.
The PWM light adjusting circuit comprises resistance R 1, resistance R 101, resistance R 59, resistance R 22, resistance R 74, NPN triode Q28 and diode D11, and the collector of NPN triode Q28 connects chip power positive pole (VCC1), grounded emitter through resistance R 22.The anode of diode D11 connects the collector of NPN triode Q28, and negative electrode connects the error amplifier anti-phase input pin (the 4th pin INN) of the IC6 of chip for driving IC6 through resistance R 74.One termination TV SKD pwm control signal output terminal of resistance R 1, the base stage of another termination NPN triode Q28.The base stage of one termination NPN triode Q28 of resistance R 101, other end ground connection.One termination TV SKD pwm control signal output terminal of resistance R 59, the collector of another termination NPN triode Q28.When the flat panel TV mainboard is come through light modulation pin (ADJ) transmission PWM dim signal; The triode Q28 of PWM light adjusting circuit is under the driving of PWM dim signal; Be operated on off state; Make the collector of triode Q28 produce pwm signal, this signal arrives the error amplifier anti-phase input pin of chip for driving IC6 through diode D11 resistance R 74, and the voltage through departure amplifier anti-phase input pin makes the output pin voltage follow of error amplifier dim signal to change; The dutycycle that also is the output pwm signal of controlling and driving chip IC 6 is followed the dim signal variation, thereby reaches the function of regulating the main circuit output current.
Chip power supply circuit comprises linear voltage-stabilizing circuit; Linear voltage-stabilizing circuit comprises NPN triode Q1, stabilivolt Z1, capacitor C 18, resistance R 16 and resistance R 15; The emitter of NPN triode Q1 connects chip for driving I C6 supply pin (the 1st pin VDD); Base stage connects the negative electrode of stabilivolt Z1, collector through resistance R 15 connect the direct-flow input circuit positive pole (+24V or+12V).The plus earth of stabilivolt Z1, a termination direct-flow input circuit of resistance R 16 anodal (+24V or+12V), the base stage of another termination NPN triode Q1.The emitter of one termination NPN triode Q1 of capacitor C 18, other end ground connection.Direct-flow input circuit (+24V or+12V) for chip for driving IC6 stable WV is provided through this circuit.
The output current sample circuit comprises resistance R 166 and resistance R 122; The negative pole LED-of flat panel TV LED-backlit source driving circuit output terminal passes through resistance R 168 ground connection, and connects the error amplifier anti-phase input pin (the 4th pin INN) of the IC6 of chip for driving IC6 through resistance R 122.The output current of resistance R 168 sampling main circuits; Sampled signal is sent to the anti-phase input pin of chip for driving IC6 error amplifier through resistance R 122; When the output current of main circuit has deviation; The voltage (reference signal) of sampled signal and error amplifier positive input pin produces error signal, and the dutycycle through the output pin of error amplifier is regulated chip for driving IC6 output pin pwm signal makes the output current of main circuit constant in preset value.
Voltage sampling circuit comprises resistance R 160, resistance R 164 and the 5th capacitor C 36, the anodal LED+ of a termination flat panel TV LED-backlit source driving circuit output terminal of resistance R 160, the overvoltage protection pin of another termination chip for driving IC6 (the 5th pin OVP).The overvoltage protection pin of one termination chip for driving IC6 of resistance R 164 (the 5th pin OVP), other end ground connection, the 5th capacitor C 36 and resistance R 164 parallel connections.164 pairs of main circuits transmissions of electricity of resistance R 160 and resistance R are pressed dividing potential drop in proportion and are carried out delivering to after the filtering overvoltage protection pin (the 5th pin OVP) of chip for driving IC6 through C36, and when the main circuit output terminal was opened a way, the voltage of output terminal will rise rapidly.After having reached the overvoltage protection thresholding of chip for driving IC6 the 5th pin, will trigger chip for driving IC6 and close output, the protection main circuit is avoided superpotential impact.
Claims (10)
1. a flat panel TV LED-backlit source driving circuit is realized the method for soft start; It is characterized in that; With the error amplifier output pin of control circuit chip for driving through bleeder resistance ground connection, when the flat panel TV mainboard through chip for driving enable pin when fast chip for driving being resetted, the voltage of chip for driving error amplifier output pin is released through bleeder resistance fast; Chip for driving is when restarting; The rising of starting from scratch of the voltage of error amplifier output pin, the dutycycle of the pwm signal of chip for driving output slowly increases, and makes entire circuit realize the soft function that opens.
2. flat panel TV LED-backlit source driving circuit; Comprise main circuit and control circuit; Main circuit comprises direct-flow input circuit, energy storage inductor, switching tube, RC stress absorption circuit and output rectifier and filter, and output rectifier and filter comprises commutation diode and filter capacitor; Control circuit comprises chip for driving, chip power supply circuit, output voltage sampling circuit, output current sample circuit, PWM light adjusting circuit and enable circuits; It is characterized in that; Comprise current sample ring compensating circuit; Described current sample ring compensating circuit comprises first resistance, bleeder resistance, first electric capacity and second electric capacity, is connected on after described first resistance and first capacitances in series between the error amplifier anti-phase input pin and error amplifier output pin of chip for driving; Described second electric capacity is connected between the error amplifier anti-phase input pin and error amplifier output pin of chip for driving; The error amplifier output pin of one termination chip for driving of said bleeder resistance, other end ground connection.
3. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Described enable circuits comprises the 3rd resistance, the 4th resistance and the 3rd electric capacity; The backlight switch signal output part of one termination TV SKD of said the 3rd resistance, another termination chip for driving enable control pin; Described the 4th resistance one termination chip for driving enable control pin, other end ground connection; Described the 3rd electric capacity and the 4th resistance also connect.
4. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Described PWM light adjusting circuit comprises the 5th resistance, the 6th resistance, the 7th resistance, the 8th resistance, the 9th resistance, first triode and diode; The collector of first triode connects chip power positive pole, grounded emitter through the 8th resistance; The anode of diode connects the collector of first triode, and negative electrode connects the error amplifier anti-phase input pin of chip for driving through the 9th resistance; One termination TV SKD pwm control signal output terminal of the 5th resistance, the base stage of another termination first triode; The base stage of one termination, first triode of the 6th resistance, other end ground connection; One termination TV SKD pwm control signal output terminal of the 7th resistance, the collector of another termination first triode.
5. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Described chip power supply circuit comprises linear voltage-stabilizing circuit, the described direct-flow input circuit of input termination of said linear voltage-stabilizing circuit, the supply pin of another termination chip for driving.
6. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Described linear voltage-stabilizing circuit comprises second triode, stabilivolt, the 4th electric capacity, the tenth resistance and the 11 resistance; The emitter of second triode connects the chip for driving supply pin, and base stage connects the negative electrode of stabilivolt, and collector connects the direct-flow input circuit positive pole through the 11 resistance; The plus earth of stabilivolt, a termination direct-flow input circuit of the tenth resistance is anodal, the base stage of another termination second triode; The emitter of one termination, second triode of the 4th electric capacity, other end ground connection.
7. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Described output current sample circuit comprises the 12 resistance and the 13 resistance; The negative pole of flat panel TV LED-backlit source driving circuit output terminal connects the error amplifier anti-phase input pin of chip for driving through the 12 resistance eutral grounding through the 13 resistance.
8. flat panel TV LED-backlit source driving circuit according to claim 1; It is characterized in that; Said voltage sampling circuit comprises the 14 resistance, the 15 resistance and the 5th electric capacity; The positive pole of one termination flat panel TV LED-backlit source driving circuit output terminal of the 14 resistance, the overvoltage protection pin of another termination chip for driving; The overvoltage protection pin of one termination chip for driving of the 15 resistance, other end ground connection, the 5th electric capacity and the parallel connection of the 15 resistance.
9. according to the described flat panel TV LED-backlit of arbitrary claim source driving circuit in the claim 2 to 8, it is characterized in that, comprise the 16 resistance, the positive pole of the said direct-flow input circuit of first termination of energy storage inductor, second termination connects first end of switching tube; The second end ground connection of switching tube, the control utmost point of switching tube connects the output terminal of chip for driving through the 16 resistance; The anode of commutation diode connects first end of switching tube, and negative electrode connects the positive pole of flat panel TV LED-backlit source driving circuit output terminal; The negative electrode of one termination commutation diode of filter capacitor, other end ground connection, the grounding leg ground connection of chip for driving.
10. flat panel TV LED-backlit source driving circuit according to claim 9; It is characterized in that; Described RC stress absorption circuit comprises the 17 resistance and the 6th electric capacity, and a termination connects first end of switching tube after the 17 resistance and the 6th capacitances in series, other end ground connection.
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| CN106373500A (en) * | 2016-11-04 | 2017-02-01 | 上海控易电子科技有限公司 | Liquid crystal display |
| CN106683621A (en) * | 2016-12-30 | 2017-05-17 | 厦门厦华科技有限公司 | LED backlight drive circuit and method of realizing soft start |
| CN107277985A (en) * | 2017-08-15 | 2017-10-20 | 合肥惠科金扬科技有限公司 | LED light adjusting circuits and LED display device |
| CN112886807A (en) * | 2021-02-07 | 2021-06-01 | 上海空间电源研究所 | Soft start realizing device and method |
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| CN102682714B (en) | 2015-04-15 |
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