creation method
If the input is unstable, add a PFC voltage regulator first, and then connect the full bridge inverter, power frequency transformer, filter circuit can be it. To 220VAC mainly depends on the control waveform of the inverter.
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operating principle
The inverter is a DC to AC transformer, which is actually a voltage inverter process 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 more widely used pulse width modulation (PWM) technology. The core part is a PWM integrated controller, the Adapter uses UC3842, and the inverter uses TL5001 chip. The operating voltage range of TL5001 is 3.6 ~ 40V, which is equipped with an error amplifier, a regulator, an oscillator, a 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, the ENB voltage is provided by the MCU on the motherboard, and its value is 0 or 3V. When ENB=0, the inverter does not work, and when ENB=3V, the inverter is in normal working state. The DIM voltage is provided by the motherboard, and its variation range is between 0 and 5V, the different DIM values are fed back to the PWM controller feedback terminal, the current provided by the inverter to the load will also be different, the smaller the DIM value, the larger the inverter output current.
Voltage starting loop: ENB is high voltage, output high voltage to light the backlight tube of the Panel.
PWM controller: consists of the following functions: internal reference voltage, error amplifier, oscillator and PWM, overvoltage protection, undervoltage protection, short circuit protection, output transistor.
Dc conversion: The MOS switch tube and the energy storage inductor are composed of voltage conversion circuit, and the input pulse is amplified by the push-pull amplifier to drive the MOS tube to do switching action, so that the DC voltage charges and discharges the inductor, so that the other end of the inductor can get AC voltage.
LC oscillation and output loop: Ensure the lamp to start the required 1600V voltage, and after the lamp to start the voltage down to 800V.
Output voltage feedback: When the load is working, the feedback sampling voltage plays a role in stabilizing the voltage output of the I inverter.