An inverter is a DC to AC transformer, which is actually a process of voltage inversion with the converter. The converter converts the AC voltage of the power grid into a stable 12V DC output, while the inverter converts the 12V DC voltage output by the adapter into high-frequency high-voltage AC; Both parts also use the commonly used Pulse Width Modulation (PWM) technology. The core part is all a PWM integrated controller, with the adapter using UC3842 and the inverter using TL5001 chip. The working voltage range of TL5001 is 3.6-40V, and it is equipped with an error amplifier, a regulator, oscillator, PWM generator with dead zone control, low voltage protection circuit, and short circuit protection circuit.
Input interface part: The input part has 3 signals, 12V DC input VIN, working enable voltage ENB, and panel current control signal DIM. The VIN is provided by the adapter, and the ENB voltage is provided by the MCU on the motherboard, with a value of 0 or 3V. When ENB=0, the inverter does not work, while when ENB=3V, the inverter is in normal working state; The DIM voltage is provided by the motherboard, with a variation range of 0-5V. Different DIM values are fed back to the feedback end of the PWM controller, and the current provided by the inverter to the load will also be different. The smaller the DIM value, the greater the current output by the inverter.
Voltage start circuit: ENB is a high voltage circuit that outputs high voltage to light up the backlight tube of the Panel.
PWM controller: It consists of the following functions: internal reference voltage, error amplifier, oscillator and PWM, overvoltage protection, undervoltage protection, short circuit protection, and output transistor.
DC conversion: A voltage conversion circuit composed of MOS switch tubes and energy storage inductors. The input pulse is amplified by a push-pull amplifier to drive the MOS tube to perform switching actions, causing DC voltage to charge and discharge the inductor, so that the other end of the inductor can receive AC voltage.
LC oscillation and output circuit: Ensure the required voltage of 1600V for lamp start, and reduce the voltage to 800V after lamp start.
Output voltage feedback: When the load is working, the feedback sampling voltage plays a role in stabilizing the voltage output of the I inverter.