Introduction to the Working Principle of the Inverter

How Inverters Work

1. Direct current can be converted into alternating current through the oscillating circuit;
2. The obtained alternating current is then boosted by the coil (at this time, the alternating current of square wave is obtained);
3. Rectify the obtained alternating current to obtain a sine wave.

AC-DC is relatively simple, we know that diodes have unidirectional conductivity. This characteristic of diodes can be used to form a bridge so that one end is always flowing in and the other end is always flowing out, which results in a DC voltage with a sinusoidal change in voltage. If you need smooth DC and rectification, the easy way is to connect a capacitor.

The inverter is a DC to AC transformer, which is actually a voltage inversion process with Adapter. The Adapter converts the AC voltage of the mains grid into a stable 12V DC output, and the Inverter converts the 12V DC voltage output by the Adapter into a high-frequency high-voltage AC; both parts also use the pulse width that is currently used more frequently. modulation (PWM) technology. Its core part is a PWM integrated controller, the Adapter uses the UC3842, and the Inverter uses the TL5001 chip. The working voltage range of TL5001 is 3.6~40V. 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:
The input part has 3 signals, 12V DC input VIN, work enable voltage ENB, and Panel current control signal DIM. VIN is provided by Adapter, ENB voltage is provided by 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 a normal working state; while the DIM voltage is provided by the motherboard, The variation range is between 0 and 5V. When different DIM values are fed back to the feedback terminal of the PWM controller, 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 a high voltage to light the backlight lamp of the Panel.

PWM controller:
It consists of the following functions: internal reference voltage, error amplifier, oscillator and PWM, overvoltage protection, under-voltage protection, short circuit protection, and output transistor.

DC conversion:
A 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 the AC voltage.

LC oscillation and output circuit:
Ensure the 1600V voltage required to start the lamp, 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 Inventer. Actually, you can imagine it. There are those electronic components that require positive and negative electrodes, resistors, and inductors generally not needed. If the diode is generally bad, it may be broken down. As long as the voltage is normal, there is generally no problem. The triode will not conduct. The Zener tube will be damaged if the positive and negative connections are reversed, but generally, some circuits are protected by the unidirectional conduction of the diode. It is the capacitor. The positive and negative points in the capacitor are electrolytic capacitors. If the positive and negative connections are serious, the shell will burst.

Main component diode. Switch tube oscillator transformer. sampling. Widen the tube. There is also the principle of the switching circuit such as the resistance and capacitance of the oscillation circuit.

The selection of the main power components of the inverter is very important. At present, the most used power components are Darlington power transistors (BJTs), power field effect transistors (MOSFETs), insulated gate transistors (IGBTs), and turn-off thyristors ( GTO), etc., MOSFETs are used more in small-capacity low-voltage systems. Because MOSFETs have a lower on-state voltage drop and higher switching frequency, IGBT modules are generally used in high-voltage and large-capacity systems. This is because As the voltage increases, the on-state resistance of MOSFET also increases, while IGBT has a greater advantage in medium-capacity systems. In extra-large-capacity (above 100KVA) systems, GTO is generally used as a large power component. : FET or IGBT, transformer, capacitor, diode, comparator, and master control such as 3525. The AC-DC-AC inverter also has rectification and filtering. The power size and accuracy are related to the complexity of the circuit. You can take a look at the mobile phone charger, this is a small switching power supply!

IGBT (Insulated Gate Bipolar Transistor), as a new type of power semiconductor field-controlled self-shutdown device, integrates the high-speed performance of power MOSFET and the low resistance of bipolar devices. It has high input impedance, low voltage control power consumption, and a simple control circuit. , high voltage resistance, high current resistance, and other characteristics, it has been widely used in various power conversions. At the same time, major semiconductor manufacturers continue to develop high-voltage, high-current, high-speed, low-saturated voltage drop, high-reliability, and low-cost technologies for IGBTs.

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