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What is Pure Sine Wave Inverter- You Need to Know ?

August 31,2023

What is inverter

The inverter converts DC power (battery, storage battery) into AC power (generally 220V, 50Hz sine wave). It consists of inverter bridge, control logic and filter circuit.

Simply put, an inverter is an electronic device that converts low voltage (12 or 24 volts or 48 volts) direct current into 220 volts alternating current. Because we usually use the 220-volt alternating current rectifier to turn it into direct current, and the inverter acts in the opposite direction, hence the name.

What is a sine wave inverter

Inverters can be classified according to their output waveforms, a. divided into square wave inverters, b. modified wave inverters and c. sine wave inverters.


Therefore, the definition of a sine wave inverter is an inverter whose output waveform is a sine wave.

Its advantage is that the output waveform is good, the distortion is very low, and its output waveform is basically consistent with the AC waveform of the mains grid. In fact, the quality of the AC power provided by the excellent sine wave inverter is higher than that of the grid. The sine wave inverter has little interference to radio, communication equipment and precision equipment, low noise, strong load adaptability, can meet the application of all AC loads, and the whole machine has high efficiency; its disadvantage is that the line and relative correction wave inversion The inverter is complex, has high requirements for control chips and maintenance technology, and is expensive.


How it works?

Before introducing the working principle of the sine wave inverter, first introduce the working principle of the inverter.The 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 a high-frequency high-voltage AC; both parts also use a more frequently used pulse width modulation (PWM) technique. Its core part is a PWM integrated controller, the Adapter uses UC3842, and the inverter uses TL5001 chip. The working voltage range of TL5001 is 3.6 ~ 40V, and it is equipped with 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.

Input interface part: There are 3 signals in the input part, 12V DC input VIN, work 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, 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; while DIM voltage Provided by the main board, its variation range is between 0 and 5V. Different DIM values are fed back to the feedback terminal of the PWM controller, and the current provided by the inverter to the load will also be different. The smaller the DIM value, the smaller the output current of the inverter. bigger.

Voltage startup circuit: When ENB is at high level, it outputs high voltage to light up the Panel's backlight tube.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 MOS switching tube and energy storage inductor. The input pulse is amplified by the push-pull amplifier and then drives the MOS tube to perform 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 circuit: ensure the 1600V voltage required for the lamp to start, and reduce the voltage to 800V after the lamp is started.

Output voltage feedback: When the load is working, the sampling voltage is fed back to stabilize the voltage output of the I inverter.


The difference between the sine wave inverter and the ordinary inverter is that its output waveform is a complete sine wave with low distortion rate, so there is no interference to the radio and communication equipment, the noise is also very low, the protection function is complete, and the overall efficiency is high.

The reason why the sine wave inverter can output a complete sine wave is because it uses SPWM technology which is more advanced than PWM technology.

The principle of SPWM is based on the equivalent principle that pulses act on time function devices: if the pulses act on time function devices, the product of the peak value and the action time is equal, and these pulses can be approximated to be equivalent.

SPWM compares the triangular wave with fixed frequency and fixed peak value (such as switching frequency 10k) with the reference sine wave (fundamental wave) of variable frequency and voltage, so as to pulse the DC voltage (pulse with changing duty cycle) to approximate the reference sine wave on the device. The amplitude and frequency of the reference sine wave are adjusted to generate DC voltage pulse width modulation waves equivalent to the reference sine wave with different amplitudes and frequencies.