食品安全科普知识图片:TCL液晶电视电源板维修技术【步步精通】

TCL液晶电视目前在市场占有率不但的增加已经进入国内销量前三甲。电源在电视机中又是比较容易损坏的部分，熟悉并掌握对其维修、代换方法就比较重要。本人做售后多年，现在就为大家介绍一下我的经验。TCL液晶电视机采用的电源板主要的有以下几种；
   1 型号：PWL37C， 
    适用机型：LCD26/32/37M61，LCD27/32/37/40K73，L32/40/42E9，L32/37/40/42E77等 
    输出电压：+5V，+12V，+24V 
    2型号：JSK4330-007/007A 
    适用机型：LCD40/42K73，LCD40/42B66-P，LCD40/42A71-P等 
    输出电压：+5V，+12V，，+18V，+24V
    3型号：JSK4338-007 
    适用机型：LCD40/42K73B等 
    输出电压：+5V，+12V，，+18V，+24V 
    4型号：PWL4202C 
    适用机型：LCD40/42/46E77/F，L40/4246E64，LCD40/42/47K73等 
    输出电压：+5V，+12V，，+18V，+24V 
    5型号：PWL42C 
    适用机型：LCD42/46E77，LCD42M61F，L42M61R等 
    输出电压：+5V，+12V，，+18V，+24V 
    6型号：JSK3220-007A/C/D， 
    适用机型：LCD26B66/L/P，LCD32B66/L/P，LCD32A71/P等 
    输出电压：+9V，+12V，+24V 
    通常我把电源分成5个部分来维修，他们分别是；
    1待机电源部分； 
    2开/待机控制部分； 
    3PFC振荡电路部分； 
    4PWM振荡电路部分； 
    5保护电路部分。 
TCL液晶电视电源板维修技术【步步精通】下面就介绍一下这几个部分的工作和易损原件。
    PWL37C待机电源采用的振荡块是IC1（VIPER22A），VIPER22A在DVD机、卫星天线接收机上常用。典型的反激式电源，工作时会输出二组电压，一组+5V输出到主板给CPU部分供电，另一组+20V输出供给电源板的PFC振荡电路部分和PWM振荡电路部分用；开机后电源输出插座P3就会有+5V电压输出，如没有电压输出，只要检查以集成块VIPER22A为中心的开关电路即可。 
    常坏的元件有：限流电阻RB1、RB2、RB13（2.7欧)焊接帽部分易脱焊，如有损坏最好把这三个电阻用一个几欧的、功率1W或2W的电阻代换，以免以后再从此处坏；稳压管DB5(20V)、DB10(33V)、DB8（13V）易损坏，如损坏多会出现+5V电压在+4V左右抖动或不起振等现象；滤波电容CB7、CB8(1000UF)易变质，造成+5V电压低等。如果出现输出电压不对，就要查以TL431组成的稳压控制部分。
 
   第二部分：开/待机控制部分； 
    开机时电源板的插座P2的第一脚PS-ON收到从主板过来高电平开机信号，通过DS9、RS16加到三极管QS3（BT3904，可用C1815代）的B极，这时QS3导通，5V电压通过RS15后流过光耦IC6的1、2脚，此时光耦的3、4导通，从待机电源输出的20V左右的VC电压就可以通过Q11给PFC电路提供+19V左右的工作电压，再通过Q12后给PWM电路提供+12V左右的工作电压。  
    待机时电源板收到的PS-ON信号是低电平，QS3的B极因没有电压而截止，此时光耦IC6无法工作，因此VC电压就无法通过Q11、Q12提供VCC2和VCC1电压，机器的PFC和PWM就会停止工作。
  第三部分：PFC功率因素校正电路部分： 
    PFC是功率因素校正的意思，工作原理是通过电感来校正电流的相位，使电流与电压相位一致以提高功率因素，并防止电路产生的多次谐波对电网的干扰，提高电源的有效利用率。 
    功率因素的定义：交流输入实际功率与视在功率之比。 
    现在液晶电视机电源功率因素校正部分采用的是有源技术，采用此技术后功率因素值可由原来的50%提高至90%。 
    这部分是以集成块IC2（L6563）、开关管QF5、QF6（SK3568，可用K2645代）组成的PFC振荡电路，当19V左右的电压输入到IC2的第14脚后，IC2开始工作，从13脚输出脉冲信号控制QF3、QF4组成的推挽电路交替导通和截止。然后再驱动QF5和QF6导通和截止。整流后的市电对储能电感L1进行充电，电能转化成磁能储存在L1中；当PFC的驱动信号是低电平时，此时控制QF5、QF6的G极为低电平， QF5和QF6截止。使L1储存的磁能释放，经D2整流、C5滤波后输出400V左右电压。一般情况下PFC电路电容C5电压在370V 到410V之间都是正常的。通过测电容C5上的电压就可知道PFC电路工作是否正常。如果PFC电路没有工作，电容C5上的电压就只是整流滤波后的300V左右了。
   第四部分：PWM振荡电路部分； 
    当IC3（L6599）P12脚供电以后，IC3开始工作，此时会从IC3的P11和P15脚输出脉冲信号，去控制QW9和QW10轮流导通和截至，T1的次级感应到电流，经过整流得到12V和24V电压。其中+12V供给主板用， +24V供给屏的背光板使用。 
    比较容易坏的是P7外接的电阻RW13(1M)。该脚被取样电阻连接用来检测PFC电源的输出情况。该脚电压低于1.25V时，IC被关断。在正常的情况下该脚的的电压设定在1.25-6V之间。该脚的功能用于当PFC电源异常时，保护PWM电源。 
    另外大家要注意在电路中，阻值大的电阻还是比较容易坏的，所以也是我们检查的重点；其次容易坏的就是次级整流二极管DS1，DS2，DS3，DS4，次级整流
第五部分：保护电路部分。 
    当电路发生因过压或是过流而进入保护时，表现就是开机瞬间有+12V、+24V输出，然后下降为0V。这时首先应判断是因过压还是因过流而引起的保护，可依次断开过流保护运放输出端的二极管DS10、DS11和过压保护稳压管端的二极管DS7、DS8，如果断开某一二极管后电压能恢复正常，说明电路因此路进入保护而锁定无输出（注意断开二极管后，通电不能过久，以免引起元件损坏）．
    如果是过压而保护，断开二极管时输出电压偏高，应检查电压取样反馈回路IC7（TL431）及其周围元件是否有损坏．如果输出正常则是保护电路本身损坏，如过压保护稳压管及二极管有损坏． 
    如果是过流而保护，应检查输出端是否有短路，过流保护比较器IC4（LM393）及外围元件是否有损坏而引起误保护。在这里要知道过流保护电路中采用的比较器工作原理：一个单元的比较器有二个输入脚和一个输出脚，当正相输入脚的电压大于负相输入脚的电压时，在输出脚会输出一个高电压，反之就会输出零电压。
二极管和CRT电视机用的整流二极管是有区别的，这里用的整流二极管为肖特基二极管，特点为正向压降低、电流大。
    只要你了解了以上五个部分，TCL液晶电视机所用的电源板都可以维修。目前TCL电源板到现在为止全是高电平开机，所以在修电源板时，可以直接把待机+5V用导线连接到开待机控制脚，这样就可以开机了。不接负载也可以正常检修。为了观察故障更直观和方便，还可以在商店购买到24V或36V（功率60W或100W）低压灯泡做假负载用。转帖：http://www.jdwx.info/thread-118044-1-1.html [家电维修论坛](Www.Jdwx.Info) 方便学习已翻译为英文：TCL LCD TV is not only an increase in market share, domestic sales have entered the top three. Power on the TV is relatively easy to damage in part, be familiar with and master its repair, substitution method is more important. I do sales for many years, now to tell you about my experiences. TCL LCD TV power supply board is mainly used in the following categories;
   1 Model: PWL37C,
    Applicable models: LCD26/32/37M61, LCD27/32/37/40K73, L32/40/42E9, L32/37/40/42E77 etc.
    Output voltage: +5 V, +12 V, +24 V
    2 Model: JSK4330-007/007A
    Applicable models: LCD40/42K73, LCD40/42B66-P, LCD40/42A71-P etc.
    Output voltage: +5 V, +12 V,, +18 V, +24 V
    3 Model: JSK4338-007
    Applicable models: LCD40/42K73B etc.
    Output voltage: +5 V, +12 V,, +18 V, +24 V
    4 Model: PWL4202C
    Applicable models: LCD40/42/46E77/F, L40/4246E64, LCD40/42/47K73 etc.
    Output voltage: +5 V, +12 V,, +18 V, +24 V
    5 Model: PWL42C
    Applicable models: LCD42/46E77, LCD42M61F, L42M61R etc.
    Output voltage: +5 V, +12 V,, +18 V, +24 V
    6 Model: JSK3220-007A/C/D,
    Applicable models: LCD26B66/L/P, LCD32B66/L/P, LCD32A71 / P, etc.
    Output voltage: +9 V, +12 V, +24 V
    I usually put the power into five parts to repair, they are;
    A standby power supply;
    2 on / standby control section;
    3PFC oscillation circuit portion;
    4PWM oscillation circuit portion;
    5 protection circuit.
TCL LCD TV power supply board repair techniques [step] below proficient on the introduction of these parts work and wearing the original.
    PWL37C standby power use of the oscillation block is IC1 (VIPER22A), VIPER22A in DVD players, satellite dish receivers commonly used. A typical flyback power supply, working voltage when the output of the two groups, one group of +5 V output to the CPU part of the power supply to the motherboard, another group of power supply +20 V output oscillator circuit board part of the PFC and PWM oscillation circuit part with; boot power outlet after the P3 will have a +5 V voltage output, if there is no voltage output, as long as the checks to the center manifold VIPER22A switching circuitry.
    Often the bad elements are: current limiting resistor RB1, RB2, RB13 (2.7 Euro) welding cap sealing off part is easy, if damage resistance of these three is best with a few in Europe, the power 1W or 2W resistor substitution, to avoid the bad from here later; regulator DB5 (20V), DB10 (33V), DB8 (13V) easily damaged, such as damage will occur more than +4 V +5 V voltage in about phenomena such as jitter or vibration can not afford; filter capacitor CB7 , CB8 (1000UF) perishable, resulting in low +5 V voltage. If the output voltage does not, it is necessary to check the composition of the regulator TL431 control part.
  
   Part II: on / standby control section;
    Power outlet when the power supply board the first leg of P2 received PS-ON signal from the motherboard over high power, through DS9, RS16 added to the transistor QS3 (BT3904, can be used C1815 generation) of the B pole, then QS3 conduction, After the 5V voltage flowing through the optocoupler IC6 RS15 1,2 feet, then turn on the optocoupler's 3,4, from the standby power output of about 20V voltage VC can be provided through Q11 to the PFC circuit operating voltage of about +19 V , and through Q12 to the PWM circuit after about providing +12 V operating voltage.
    Standby power supply board received PS-ON signal is low, QS3 of B very close because there is no voltage, optocoupler IC6 not work this time, so the voltage on the VC can not Q11, Q12 and VCC1 VCC2 voltage to provide the machine PFC and PWM will stop working.
  Part III: PFC power factor correction circuit components:
    PFC power factor correction is the meaning of works to correct the current through the inductive phase, the current and voltage phase line to improve power factor, and to prevent the circuit of multiple harmonics of the grid disturbance, to improve the effective utilization of power .
    Power factor definition: the actual AC input power and apparent power ratio.
    LCD TV power supply is now part of the power factor correction is used in active technology, this technology uses the power factor value from 50% to 90%.
    This part is a manifold IC2 (L6563), switch QF5, QF6 (SK3568, available K2645 generation) consisting of PFC oscillator circuit, when the voltage of about 19V input to IC2, after the first 14 feet, IC2 start working, from 13 feet output pulse signal control QF3, QF4 push-pull circuit composed of alternating on-and off. QF6 QF5 and then drive on-and off. Rectified mains charging of energy storage inductor L1, electrical energy into magnetic energy stored in L1; When the PFC drive signal is low, then control QF5, QF6 of G is very low, QF5 and QF6 deadline. The release of magnetic energy stored in L1, rectified by D2, C5 filtered output voltage of about 400V. Under normal circumstances PFC circuit capacitor C5 between voltage 370V to 410V is normal. By measuring the voltage on the capacitor C5 can be aware of the PFC circuit is working properly. If the PFC circuit is not working, the voltage on the capacitor C5 is rectified filtered 300V or so.
   Part IV: PWM oscillation circuit portion;
    When the IC3 (L6599) P12 after the foot-powered, IC3 to work, this time from the IC3 of the P11 and P15 pin output pulse signal, to control QW9 and QW10 turns on and up, T1's secondary sense current through the rectifier to be 12V and 24V. +12 V supply which motherboard to use, +24 V supply screen backlight use.
    The bad is easier to P7 of the external resistor RW13 (1M). Sampling resistor connected to the pin is used to detect the output PFC power supply situation. When the pin voltage is lower than 1.25V, IC is turned off. In normal circumstances, the voltage of the pin set between 1.25-6V. The pin function is used when the abnormal PFC power supply, PWM power supply protection.
    Also it should be noted in the circuit, the resistance is relatively large resistance easily broken, so the focus of our examination; second is easily broken secondary rectification diodes DS1, DS2, DS3, DS4, the secondary rectifier
Part V: protection circuit.
    When the circuit is due to overvoltage or overcurrent protection and access to, the performance is to start an instant with +12 V, +24 V output, then dropped to 0V. At this time we must first determine because of overvoltage or overcurrent caused by the protection, overcurrent protection can turn off the output of op amp diode DS10, DS11 and overvoltage protection regulator side of the diode DS7, DS8, if you disconnect a one diode voltage can be back to normal, indicating the way into the protection circuit is locked so no output (note off diode, the power can not be too long in order to avoid component damage).
    If overvoltage protection, output voltage diode off the high voltage sampling should check the feedback loop IC7 (TL431) and its surrounding components for damage. If the normal output protection circuit itself is damaged, such as over-voltage regulator and diode damage.
    If over-current protection, output should check whether there is short circuit, overcurrent comparator IC4 (LM393) and peripheral components for damage caused by misuse protection. Here to know current protection circuit used in the comparator works: a comparator unit has two input pins and one output pin, when the positive input pin voltage is greater than the negative phase input pin voltage of the output pin will output a high voltage, otherwise the output will be zero voltage.
Diode and rectifier diode with a CRT TV there is a difference here with the rectifier diodes Schottky diode, characterized by a positive pressure to reduce the current large.
    As long as you understand the above five parts, TCL LCD TV power supply board used can be repaired. TCL power supply board is currently up to now are all high boot, so repair the power board, can use the standby +5 V wire to open the standby control pin so that it can boot up. Normal load can not receive maintenance. Failure to observe a more intuitive and convenient, you can buy at the store to 24V or 36V (power 60W or 100W) low-voltage light bulb to use false load.
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