I. What is the working principle of an inverter?
The core components are all integrated PWM controllers. 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. The input interface has three signals: a 12V DC input VIN, an enable voltage ENB, and a 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 either 0 or 3V. When ENB=0, the inverter does not work, and when ENB=3V, the inverter is in normal operating condition. The DIM voltage is provided by the motherboard, and its range is between 0~5V. Different DIM values are fed back to the PWM controller, and the current supplied by the inverter to the load will also vary. The smaller the DIM value, the larger the inverter output current.
Voltage-start circuit: When the ENB is high, the inverter outputs high voltage to power 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: A voltage conversion circuit consisting of a MOSFET switch and an energy storage inductor. The input pulse is amplified by a push-pull amplifier and drives the MOSFET to switch, causing the DC voltage to charge and discharge the inductor, thus providing AC voltage to the other end of the inductor. LC Oscillation and Output Circuit: Ensures the 1600V voltage required for lamp startup and reduces the voltage to 800V after lamp startup. Output Voltage Feedback: When the load is operating, the sampled voltage is fed back to stabilize the inverter's voltage output.
II. What are the differences between a sine wave inverter and a regular inverter?
1. Pure sine wave inverters are suitable for any inductive and resistive loads, including various devices with AC motors such as refrigerators and washing machines. Square wave and modified wave inverters are suitable for resistive loads such as lights, televisions, and electric heaters. Pure sine wave inverters require a controllable boost function at the output stage, which significantly increases their cost.
2. Pure sine wave inverters have strict functional parameter requirements and are more expensive. They are used in electronic circuits with high requirements for waveform parameters. General inverters produce a hybrid waveform with components such as sine waves, square waves, and noise. They can be used for general electrical appliances and are less expensive.
3. The difference between a pure positive sine wave inverter and a regular inverter is that the output voltage waveform is different. A pure positive sine wave inverter is suitable for all electrical appliances, while a regular inverter is suitable for purely resistive electrical appliances such as electric furnaces.
III. How to Choose the Right Inverter
An inverter is a device that converts direct current (DC) to alternating current (AC), ensuring the output current meets our requirements. Inverters can be categorized by waveform into square wave inverters, modified wave inverters, and sine wave inverters; and by whether they are connected to the power grid into grid-connected inverters and off-grid inverters.
To help you choose the right inverter, Mr. Wang from Yufan Electric suggests the following: First, does the inverter you need need to connect to the national power grid? If not, it's an off-grid inverter. Second, what is your load? If it's an inductive load, you should choose an inverter with a power rating 2-3 times the load's power. Third, are there strict requirements for the inverter's waveform? If current requirements are strict, you must use a sine wave inverter, as square wave inverters generate more harmonics and have higher power losses.
Sine wave inverters are generally more expensive, but they offer better value for money compared to square wave inverters. Currently, solar inverters and photovoltaic inverters are in high demand, driven by this year's economic recovery and rapid development of the new energy industry, leading to increased market demand.
