Jul 22, 2020
Sine wave inverter
The working principle of sine wave inverter
The working principle of a sine wave inverter is a DC to AC transformer, which is actually a voltage inversion process with the converter.
The converter converts the AC voltage of the grid into a stable 12V DC output, and the inverter converts the 12V DC voltage output by the Adapter into high-frequency high-voltage AC; both parts also use a more used pulse width Modulation (PWM) technology. The core part is a PWM integrated controller, Adapter uses UC3842, and the inverter uses TL5001 chip. The operating voltage range of TL5001 is 3.6~40V. There is an error amplifier, a regulator, oscillator, PWM generator with dead zone control, low voltage protection circuit and short circuit protection circuit.
Input interface part: The input part has 3 signals, 12V DC input VIN, working 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, and 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; and the DIM voltage Provided by the main board with a range of 0～5V. 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 current output by the inverter. The bigger.
2. Voltage start circuit: When ENB is at high level, it outputs high voltage to light the panel's backlight tube.
3, PWM controller: It has the following functions: internal reference voltage, error amplifier, oscillator and PWM, overvoltage protection, undervoltage protection, short circuit protection, output transistor.
4. DC conversion: The voltage conversion circuit is composed of MOS switch tube and energy storage inductor. The input pulse is amplified by the push-pull amplifier and then drives the MOS tube to switch, so that the DC voltage can charge and discharge the inductor, so that the other end of the inductor can be Obtain AC voltage.
5. LC oscillation and output circuit: to ensure the 1600V voltage required for the lamp to start, and to reduce the voltage to 800V after the lamp is started.
6. Output voltage feedback: When the load is working, the sampled voltage is fed back to stabilize the voltage output of the I inverter.
How to distinguish between sine wave inverter and general inverter
1, modified sine wave inverter
shows the output voltage waveform of the modified wave inverter. Compared with the square wave, the waveform of the correction wave is significantly improved, and the content of higher harmonics is also reduced. The traditional modified wave inverter is produced by stepwise superposition of square wave voltage. This method has complicated control circuits, more power switch tubes used in superimposed lines, and larger volume and weight of the inverter. Many problems. In recent years, with the rapid development of power electronics technology, the PWM pulse width modulation method has been widely used to generate the corrected wave output. At present, the modified sine wave inverter has been widely used in user systems in remote areas, because these user systems do not require high power quality, and it can meet the needs of most electrical equipment, but it still has a 20% harmonic Wave distortion will cause problems when operating precision equipment, and will also cause high-frequency interference to communication equipment. Therefore, a sine wave inverter must be used at this time.
Sine wave inverter
2, square wave inverter
shows the output voltage waveform of the square wave inverter. Although the square wave inverter has the advantages of simple structure and low cost, it also has disadvantages such as low efficiency, high loss, large harmonic components, and restricted load. When the load is a high-power motor load or an electrical load with a transformer, the saturation flux of the load is designed according to the rising rate of the sine wave, and the rising speed of the square wave is too fast, which causes the iron core to saturate. The load will have problems such as difficulty in starting, overheating of the iron core and noise. Moreover, the efficiency of square wave inverters is much lower than that of modified wave and sine wave inverters, generally less than 60%. Due to the high power generation cost of solar PVS, the advantage of solar PVS power system is that the square wave inverter is rarely used.
The choice of sine wave inverter power device
At present, the domestic photovoltaic power generation system (PhotoVoltaic Sys-tem, PVS for short) is mainly based on the DC system, but the most common electrical load is the AC load, which makes it difficult to popularize the DC-powered photovoltaic power supply as a commodity. At the same time, because solar photovoltaic grid-connected power generation does not require batteries and is simple to maintain, saving investment is the development trend of photovoltaic power generation. All these must adopt AC power supply, so the application of inverter in PVS is becoming more and more important. Inverter is a power conversion device that converts direct current into alternating current. Inverter technology is relatively mature in power electronics technology. For example: inverters in UPS power supply, inverter technology in frequency conversion technology, inverter technology in special power supplies, and inverter technology in power conditioners, etc. These have all been introduced to the market in the form of products and have been well received by the society. Widely recognized.