Inverter knowledge: working principle of inverter

Inverter is a DC to AC transformer, which is actually a voltage inversion process with Adapter. Adapter converts the AC voltage of the mains power grid into a stable 12V DC output, while Inverter converts the 12V DC voltage output by Adapter into high-frequency high-voltage AC. Both parts use the pulse width modulation (PWM) technology which is currently more commonly used. The core part is a PWM integrated controller. The Adapter uses UC3842, while the Inverter uses TL5001 chip . The operating voltage range of TL5001 is 3.6~40V. It has an error amplifier, a regulator, an oscillator, a PWM generator with dead zone control, a low voltage protection circuit and a short circuit protection circuit. The following is a brief introduction to the working principle of Inverter:

Inverter working principle diagram

Input interface part:

The input part has three signals, 12V DC input VIN, working enable voltage ENB and Panel current control signal DIM. VIN is provided by the Adapter, 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; and the DIM voltage is provided by the motherboard, and its variation range is between 0 and 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:

When ENB is at a high level, it 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 :

The voltage conversion circuit is composed of a MOS switch tube and an energy storage inductor . The input pulse is amplified by a push-pull amplifier and then drives the MOS tube to perform a switching action, so that the DC voltage charges and discharges the inductor, so that the other end of the inductor can obtain an AC voltage.

LC oscillation and output circuit:

Ensure the 1600V voltage required for lamp starting, and reduce the voltage to 800V after the lamp starts.

Output voltage feedback:

When the load is working, the sampled voltage is fed back to stabilize the voltage output of the Inventer.