Inverter It is a converter that transforms DC power (from batteries or accumulators) into AC power with fixed frequency and voltage, or adjustable frequency and voltage (typically 220 V, 50 Hz sine wave). It consists of an inverter bridge, control logic, and a filtering circuit. It is widely used in air conditioners, home theater systems, electric grinders, power tools, sewing machines, DVD players, VCD players, computers, televisions, washing machines, range hoods, refrigerators, video recorders, massagers, fans, lighting, and more. Abroad, where car ownership is widespread, inverters can be connected to vehicle batteries to power appliances and various tools while traveling or on the road. Car‑mounted inverters available via the cigarette lighter socket come in power ratings ranging from 20 W, 40 W, 80 W, 120 W up to 150 W. For higher‑power applications, the inverter must be connected directly to the battery using appropriate cables. By plugging household appliances into the inverter’s output, you can operate them inside your vehicle. Compatible devices include mobile phones, laptops, digital camcorders, still cameras, lamps, electric shavers, CD players, game consoles, handheld computers, power tools, car refrigerators, as well as a wide range of portable equipment for travel, camping, and emergency medical use.
Working principle
Inverter It is a DC-to-AC transformer, which essentially performs a voltage inversion process.
The converter transforms the AC voltage from the mains into a stable 12 V DC output, while the inverter converts the 12 V DC output of the adapter into high‑frequency, high‑voltage AC; both stages employ pulse‑width modulation (PWM), a widely used technique. At their core, each utilizes a PWM integrated controller: the adapter employs the UC3842, whereas the inverter uses the TL5001 chip. The TL5001 operates over a supply voltage range of 3.6 to 40 V and incorporates an error amplifier, a regulator, an oscillator, a PWM generator with dead‑time control, as well as low‑voltage protection and short‑circuit protection circuits.
Input Interface Section: The input section comprises three signals: the 12 V DC input VIN, the enable voltage ENB, and the panel current control signal DIM. VIN is supplied by the adapter, while the ENB voltage is generated by the MCU on the motherboard and can be either 0 V or 3 V. When ENB = 0 V, the inverter remains off; when ENB = 3 V, the inverter operates normally. The DIM voltage, also provided by the motherboard, varies between 0 and 5 V. By feeding different DIM values to the feedback terminal of the PWM controller, the inverter adjusts the current it delivers to the load: a lower DIM value results in a higher output current.
Voltage start-up circuit: When ENB is at a high level,
The output high voltage is used to illuminate the panel’s backlight lamp tube.
PWM controller: It comprises the following functional blocks: an internal reference voltage, an error amplifier, an oscillator and PWM circuitry, overvoltage protection, undervoltage protection, short-circuit protection, and output transistors.
DC conversion: A voltage‑conversion circuit composed of MOS switching transistors and an energy‑storage inductor. The input pulse is amplified by a push‑pull amplifier and then used to drive the MOS transistors, causing them to switch. This results in the charging and discharging of the inductor from the DC supply, thereby generating an AC voltage across the other terminal of the inductor.
LC Oscillation and Output Circuit: It ensures the 1600 V required for lamp ignition and, once the lamp has started, reduces the voltage to 800 V.
Output voltage feedback: When the load is operating, the sampled voltage is fed back to stabilize the inverter’s output voltage.
