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TL494 Inverter CCFL LCD Schematic.JPG

TL494 Inverter CCFL LCD schematic.JPG

The TL494 is a versatile and widely used integrated circuit for the control of switching power supplies. It can generate pulse-width-modulated (PWM) signals that regulate the output voltage and current of the power supply. One of the applications of the TL494 is to drive cold cathode fluorescent lamps (CCFLs) that are used as backlight sources for liquid crystal displays (LCDs).

TL494 Inverter CCFL LCD schematic.JPG


A CCFL is a type of gas-discharge lamp that emits light when an electric current passes through a tube filled with mercury vapor and argon gas. The mercury atoms are excited by the electric field and emit ultraviolet radiation, which is converted into visible light by a phosphor coating on the inner wall of the tube. A CCFL requires a high voltage (typically 600 to 1500 V) and a high frequency (typically 20 to 100 kHz) to operate, which cannot be supplied directly by the mains power source. Therefore, an inverter circuit is needed to convert the low voltage and low frequency input into a high voltage and high frequency output.

A TL494 inverter CCFL LCD schematic.JPG is a diagram that shows how to use the TL494 to design an inverter circuit for driving a CCFL LCD. The schematic can be found on various websites that provide service manuals, datasheets, and repair information for electronics enthusiasts. For example, one such schematic can be seen [here].

The schematic shows the basic components and connections of the inverter circuit. The input voltage (VCC) is filtered by a capacitor (C1) and fed into the TL494 chip (IC1). The TL494 has two error amplifiers (EA1 and EA2), an oscillator (OSC), a dead-time control (DTC), a PWM comparator (PWM), and two output transistors (Q1 and Q2). The error amplifiers are used to sense and regulate the output voltage and current of the inverter. The oscillator generates a sawtooth waveform that determines the switching frequency of the output transistors. The dead-time control sets the minimum off-time between the switching cycles of the output transistors. The PWM comparator compares the sawtooth waveform with the control signals from the error amplifiers and modulates the pulse width of the output transistors.

The output transistors alternately switch on and off, creating a square wave output that drives a transformer (T1). The transformer steps up the voltage and isolates the output from the input. The output of the transformer is rectified by a diode bridge (D1-D4) and filtered by a capacitor (C2). The rectified output is connected to two series resistors (R1 and R2) that limit the current through the CCFL. The CCFL is connected across the resistors, forming a resonant circuit with a capacitor (C3). The resonant circuit enhances the efficiency and brightness of the CCFL by matching its impedance with the output impedance of the inverter.

The TL494 inverter CCFL LCD schematic.JPG is a useful reference for anyone who wants to learn how to use the TL494 to design an inverter circuit for driving a CCFL LCD. The schematic illustrates the basic principles and functions of the TL494 and its components. However, it should be noted that different CCFLs may have different specifications and requirements, such as voltage, current, frequency, and size. Therefore, some modifications and adjustments may be needed to optimize the performance and safety of the inverter circuit for a specific CCFL LCD.


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