Vestel 17pw20 1 Smps Schematic Diagram A
Vestel 17PW20 1 SMPS Schematic Diagram
Vestel 17PW20 1 is a resonant mode switched-mode power supply (SMPS) that is used in many LCD TVs. It provides various output voltages, such as +5V, +12V, +24V, and +33V, to power the TV's main board, backlight, and audio amplifier. The SMPS also has a standby mode that reduces the power consumption when the TV is turned off or in sleep mode.
In this article, we will explain the main components and functions of the Vestel 17PW20 1 SMPS, and show its schematic diagram. We will also provide some tips on how to troubleshoot and repair common faults in this SMPS.
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Main Components and Functions of Vestel 17PW20 1 SMPS
The Vestel 17PW20 1 SMPS consists of four main sections: the input filter, the power factor correction (PFC) circuit, the resonant converter, and the output rectifier and filter. The schematic diagram of the SMPS is shown below:
The input filter section consists of a fuse (F800), a varistor (R801), an electromagnetic interference (EMI) filter (L802, C800, C802), and a bridge rectifier (D800). The input filter protects the SMPS from overcurrent, overvoltage, and noise from the AC mains. The bridge rectifier converts the AC input voltage to a DC voltage of about 310V.
The PFC circuit consists of a boost converter that uses an N-channel MOSFET (Q803), a diode (D805), an inductor (L810), and a capacitor (C819). The PFC circuit boosts the DC input voltage to about 400V and improves the power factor of the SMPS by making the input current follow the input voltage waveform. The PFC circuit is controlled by an integrated circuit (IC802), which uses a zero current detection (ZCD) pin to sense the current through the inductor and switch the MOSFET accordingly. The PFC circuit also has an overvoltage protection (OVP) circuit that uses an optocoupler (IC801) and a zener diode (D826) to monitor the output voltage and turn off the MOSFET if it exceeds a certain threshold.
The resonant converter consists of a half-bridge inverter that uses two N-channel MOSFETs (Q829 and Q830), two capacitors (C877 and C878), and a resonant transformer (TR806). The resonant converter converts the 400V DC voltage to a high-frequency AC voltage that drives the primary winding of the transformer. The resonant converter operates at a variable frequency that is determined by the feedback signal from the secondary winding of the transformer. The resonant converter is controlled by an integrated circuit (IC809), which uses a sync pin to synchronize with the ZCD signal from the PFC circuit and a feedback pin to adjust the switching frequency according to the load condition. The resonant converter also has an overcurrent protection (OCP) circuit that uses an optocoupler (IC811) and a resistor (R884) to sense the current through the MOSFETs and turn them off if it exceeds a certain limit.
The output rectifier and filter section consists of several diodes, capacitors, inductors, and regulators that rectify and filter the secondary voltages from the transformer and provide stable output voltages for different loads. The output voltages are as follows:
+5V: This voltage is used to power the TV's main board and audio amplifier. It is generated by a diode (D840) and a capacitor (C852). It also has a standby mode that reduces its current to about 0.5A when the TV is turned off or in sleep mode. The standby mode is controlled by a transistor (Q831) and a resistor (R956).
+12V: This voltage is used to power the TV's backlight. It is generated by a diode (D841) and a capacitor (C853). It also has a standby mode that reduces its current to about 0.2A when the TV is turned off or in sleep mode. The standby mode is controlled by a transistor (Q833) and a resistor (R958).
+24V: This voltage is used to power the TV's backlight. It is generated by a diode (D820) and a capacitor (C850). It also has a standby mode that reduces its current to about 0.1A when the TV is turned off or in sleep mode. The standby mode is controlled by a transistor (Q805) and a resistor (R893).
+33V: This voltage is used to power the TV's backlight. It is generated by a diode (D823) and a capacitor (C863). It also has a standby mode that reduces its current to about 0.05A when the TV is turned off or in sleep mode. The standby mode is controlled by a transistor (Q808) and a resistor (R914).
+3.3VSTBY: This voltage is used to power the TV's standby circuit. It is generated by a regulator (Q804) and a capacitor (C824). It is always on regardless of the TV's power state.
+2.5V: This voltage is used to power the IC809 and IC811. It is generated by a zener diode (D847) and a capacitor (C884).
Troubleshooting and Repairing Common Faults in Vestel 17PW20 1 SMPS
Some of the common faults that may occur in the Vestel 17PW20 1 SMPS are:
No power or no standby: This fault may be caused by a blown fuse, a shorted varistor, a defective bridge rectifier, a faulty PFC circuit, or a damaged resonant converter. To troubleshoot this fault, check the input voltage, the output voltage, and the components in each section with a multimeter and an oscilloscope. Replace any defective components with the same or equivalent ones.
Low or unstable output voltages: This fault may be caused by a bad capacitor, a leaky diode, a faulty regulator, or an incorrect feedback signal. To troubleshoot this fault, measure the output voltages and ripple voltages with a multimeter and an oscilloscope. Check the capacitors for bulging, leaking, or high ESR. Check the diodes for shorting or reverse leakage. Check the regulators for proper output and input voltages. Check the feedback signal for proper frequency and amplitude.
Overheating or burning components: This fault may be caused by an excessive load, a short circuit, or an improper cooling system. To troubleshoot this fault, check the load current and power consumption with an ammeter and a wattmeter. Check for any short circuits or loose connections in the output circuits. Check the cooling fan and heatsink for proper operation and ventilation.
When repairing the Vestel 17PW20 1 SMPS, always follow the safety precautions and use the appropriate tools and equipment. Always disconnect the power cord before opening the TV or touching any components. Always discharge the capacitors before handling them. Always use an isolation transformer when testing the SMPS with live voltage. Always wear protective gloves and goggles when soldering or desoldering components.
Conclusion
The Vestel 17PW20 1 SMPS is a resonant mode switched-mode power supply that provides various output voltages for LCD TVs. It has four main sections: the input filter, the PFC circuit, the resonant converter, and the output rectifier and filter. It also has several protection circuits and standby modes to improve its performance and efficiency. The SMPS can be troubleshooted and repaired by checking its input voltage, output voltage, components, and signals with appropriate tools and equipment.
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