I. Working Principle of Inverters
An inverter is a DC-to-AC transformer; it essentially performs a voltage inversion process, similar to a converter. A converter transforms the AC voltage from the grid into a stable 12V DC output, while an inverter transforms the 12V DC output from the adapter into high-frequency, high-voltage AC. Both components utilize pulse-width modulation (PWM) technology. Their core component is a PWM integrated controller; the adapter uses the UC3842, while the inverter uses the TL5001 chip. The TL5001 operates within a voltage range of 3.6–40V and internally includes an error amplifier, a regulator, an oscillator, a PWM generator with dead-time control, low-voltage protection circuits, and short-circuit protection circuits.
Input Interface Section: The input section has three signals: 12V DC input VIN, operating enable voltage ENB, and panel current control signal DIM. VIN is provided by the adapter, and the ENB voltage is provided by the MCU on the motherboard. Its value is 0 or 3V. When ENB=0, the inverter does not work, and when ENB=3V, the inverter is in normal working condition. The DIM voltage is provided by the motherboard, and its range is between 0 and 5V. Different DIM values are fed back to the PWM controller feedback terminal, and the current supplied by the inverter to the load will also be different. The smaller the DIM value, the larger the inverter output current.
Voltage-activated circuit: When ENB is high, it outputs high voltage to light up the panel's backlight tubes.
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-DC conversion: The voltage conversion circuit consists of a MOS switch and an energy storage inductor. The input pulse is amplified by a push-pull amplifier and drives the MOS switch to perform switching action, so that the DC voltage charges and discharges the inductor, and the other end of the inductor can obtain the AC voltage.
LC oscillation and output circuit: ensures the 1600V voltage required for lamp startup, and reduces 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 inverter voltage output.
II. The function of an inverter
An inverter converts direct current (DC) energy (from batteries or storage devices) into alternating current (AC) (typically 220V 50Hz sine or square wave). In simpler terms, an inverter is a device that converts direct current (DC) to alternating current (AC). It consists of an inverter bridge, control logic, and filter circuitry.
Simply put, an inverter is an electronic device that converts low-voltage (12, 24, or 48 volts) direct current into 220 volt alternating current. It gets its name from the fact that 220 volt alternating current is usually rectified into direct current for use, while an inverter does the opposite. In a mobile era, with mobile offices, mobile communications, and mobile leisure and entertainment, not only is low-voltage direct current supplied by batteries or accumulators needed, but also the indispensable 220 volt alternating current found in everyday environments. Inverters can meet these needs.
