Product Details
Feature:
1: Small size
2: high power
3: Easy to install
4: stable performance
5: cost-effective
1: Small size
2: high power
3: Easy to install
4: stable performance
5: cost-effective
Describe:
DC sampling type LCD universal LCD TV switching power supply module below 46 inches
(Note: This PFC380V voltage cannot be used, and the primary non-feedback winding cannot be used)
12V 24V without adjustment.
Small size, high power, stable and easy to install
DC sampling type LCD universal LCD TV switching power supply module below 46 inches
(Note: This PFC380V voltage cannot be used, and the primary non-feedback winding cannot be used)
12V 24V without adjustment.
Small size, high power, stable and easy to install
LCD TV power board repair experience
1. What is a PFC circuit? To put it bluntly, the PFC circuit is to raise the +300V voltage after rectification of the bridge stack to +375V----+400V. This is also the first point of the difference between the power supply of the LCD TV and the power supply of the CRT TV. The second point of the difference is that the secondary voltage is lower than that of the CRT. In other places, the principle is the same as that of the ordinary switching power supply. If the voltage across the large filter capacitor 330U/450V is measured to be +375V---+400V, it indicates that the power factor correction circuit is working normally; if the voltage across the capacitor is measured to be +300V, it means that the PFC circuit is not working, and the main check is the PFC oscillation integrated circuit. !
2. When overhauling the LCD power supply, first confirm the status of the fuse, and the fuse is in good condition. Usually, the switch tube in the PFC correction circuit has not failed. Then measure whether there is a short circuit between the large electrolytic capacitor and the ground, and there is a charging resistance of more than tens of thousands of ohms, indicating that the power supply has not broken down. If the fuse is damaged, the first one should check the switch tube of the PFC correction circuit, and the second one should check the auxiliary power IC.
3. General output voltages of +5V, +12V, +24V for units below 40 inches; four voltages of +5V, +12V, +18V, and +24V for general outputs above 40 inches. Among them, +5 V is the standby voltage, +12V is used for the digital board, +18V is used for the audio, and +24V is used for the backlight board. In practical maintenance, as long as each group of power boards with the same voltage and power can be replaced.
4. The power board can be removed from the TV for independent maintenance. During maintenance, you only need to short-circuit the transistors C and E of the switch control circuit (or connect a resistor of about 1.5K to the +5V output of the auxiliary power supply). The machine is in the power-on state, and each voltage is output. In the switching power supply of some LCD color TVs, only the +12V or +24V output terminal has a certain power load, and the main switching power supply can work normally. So on the +24V output end you can connect a 36V light bulb of an electric bicycle as a dummy load (or connect a motorcycle bulb on the +12V output end as a dummy load).
5. After the LCD power supply is powered on, the auxiliary power supply works first, and outputs +5V voltage to the CPU on the digital board. At this time, the whole machine is in a standby state. When the "standby" button is pressed, the CPU outputs the power-on level, the PFC circuit works first, and after the +300V pulsating DC voltage is converted into a normal DC voltage (+380V), then the pulse width oscillator of the main switching power supply starts to work. , and then the secondary output of the main switching transformer +12V, +24V voltage, the whole machine enters the normal working state.
6. Protection circuit, in the LCD color TV switching power supply, in addition to the common peak absorption protection circuit, it is also set in the overvoltage and overload protection circuits of +24V, +12V and +5V voltage, and its protection circuit mostly adopts four operational amplifiers LM324, quad voltage comparator LM339, dual voltage comparator LM393 or dual op amp LM358. The overcurrent and overvoltage protection circuit can be disconnected during maintenance. If the voltage returns to normal, it means that the protection circuit is caused. At this time, it is necessary to disconnect it step by step. Then perform repairs. )
7. Before starting the machine, first confirm whether there is any explosion or capacitor bulge. If so, replace it first and measure all related components. It is recommended that when testing the machine after replacing all damaged components, it is best to remove the fuse of the original machine and connect a 220V/100W light bulb, which can effectively prevent the parts from being fried again.
8. The output current of the main switch voltage +24V or +12V is relatively large, and the requirements for rectifier diodes are relatively high. Generally, high-power Schottky diodes with low dropout are used, which cannot be replaced by ordinary rectifier diodes. In addition, after the load is connected, the voltage rises instead, which is mostly caused by poor power supply filtering.
9. The power supply has poor load capacity. First, check whether the PFC voltage is normal (380 V). If it is normal, the problem lies in the power supply thick film, which is usually caused by the poor load capacity of the power supply thick film. Please pay attention to this.
10. On the power board, the heat sink marked with the ** triangle mark and the circuit under the heat sink are all hot ground. Rigorous and direct hand contact! Note that any testing equipment cannot be directly connected between the hot ground and the cold ground.
1. What is a PFC circuit? To put it bluntly, the PFC circuit is to raise the +300V voltage after rectification of the bridge stack to +375V----+400V. This is also the first point of the difference between the power supply of the LCD TV and the power supply of the CRT TV. The second point of the difference is that the secondary voltage is lower than that of the CRT. In other places, the principle is the same as that of the ordinary switching power supply. If the voltage across the large filter capacitor 330U/450V is measured to be +375V---+400V, it indicates that the power factor correction circuit is working normally; if the voltage across the capacitor is measured to be +300V, it means that the PFC circuit is not working, and the main check is the PFC oscillation integrated circuit. !
2. When overhauling the LCD power supply, first confirm the status of the fuse, and the fuse is in good condition. Usually, the switch tube in the PFC correction circuit has not failed. Then measure whether there is a short circuit between the large electrolytic capacitor and the ground, and there is a charging resistance of more than tens of thousands of ohms, indicating that the power supply has not broken down. If the fuse is damaged, the first one should check the switch tube of the PFC correction circuit, and the second one should check the auxiliary power IC.
3. General output voltages of +5V, +12V, +24V for units below 40 inches; four voltages of +5V, +12V, +18V, and +24V for general outputs above 40 inches. Among them, +5 V is the standby voltage, +12V is used for the digital board, +18V is used for the audio, and +24V is used for the backlight board. In practical maintenance, as long as each group of power boards with the same voltage and power can be replaced.
4. The power board can be removed from the TV for independent maintenance. During maintenance, you only need to short-circuit the transistors C and E of the switch control circuit (or connect a resistor of about 1.5K to the +5V output of the auxiliary power supply). The machine is in the power-on state, and each voltage is output. In the switching power supply of some LCD color TVs, only the +12V or +24V output terminal has a certain power load, and the main switching power supply can work normally. So on the +24V output end you can connect a 36V light bulb of an electric bicycle as a dummy load (or connect a motorcycle bulb on the +12V output end as a dummy load).
5. After the LCD power supply is powered on, the auxiliary power supply works first, and outputs +5V voltage to the CPU on the digital board. At this time, the whole machine is in a standby state. When the "standby" button is pressed, the CPU outputs the power-on level, the PFC circuit works first, and after the +300V pulsating DC voltage is converted into a normal DC voltage (+380V), then the pulse width oscillator of the main switching power supply starts to work. , and then the secondary output of the main switching transformer +12V, +24V voltage, the whole machine enters the normal working state.
6. Protection circuit, in the LCD color TV switching power supply, in addition to the common peak absorption protection circuit, it is also set in the overvoltage and overload protection circuits of +24V, +12V and +5V voltage, and its protection circuit mostly adopts four operational amplifiers LM324, quad voltage comparator LM339, dual voltage comparator LM393 or dual op amp LM358. The overcurrent and overvoltage protection circuit can be disconnected during maintenance. If the voltage returns to normal, it means that the protection circuit is caused. At this time, it is necessary to disconnect it step by step. Then perform repairs. )
7. Before starting the machine, first confirm whether there is any explosion or capacitor bulge. If so, replace it first and measure all related components. It is recommended that when testing the machine after replacing all damaged components, it is best to remove the fuse of the original machine and connect a 220V/100W light bulb, which can effectively prevent the parts from being fried again.
8. The output current of the main switch voltage +24V or +12V is relatively large, and the requirements for rectifier diodes are relatively high. Generally, high-power Schottky diodes with low dropout are used, which cannot be replaced by ordinary rectifier diodes. In addition, after the load is connected, the voltage rises instead, which is mostly caused by poor power supply filtering.
9. The power supply has poor load capacity. First, check whether the PFC voltage is normal (380 V). If it is normal, the problem lies in the power supply thick film, which is usually caused by the poor load capacity of the power supply thick film. Please pay attention to this.
10. On the power board, the heat sink marked with the ** triangle mark and the circuit under the heat sink are all hot ground. Rigorous and direct hand contact! Note that any testing equipment cannot be directly connected between the hot ground and the cold ground.
Package List:
1x Switching power supply module
1x Switching power supply module
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