The working principle and function of the inverter

DC power (battery, storage battery) is converted into AC (generally 220V, 50Hz sine wave). It consists of inverter bridge, control logic and filter circuit. Widely used in air conditioners, home theaters, electric grinding wheels, electric tools, sewing machines, DVD, VCD, computers, TVs, washing machines, range hoods, refrigerators, VCRs, massagers, fans, lighting, etc.

How the inverter works

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, over voltage protection, under voltage 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 role of the inverter

1. Maximum power tracking function to ensure maximum output power

The current and voltage of the solar panel change with the intensity of solar radiation and the temperature of the solar module itself, so the output power will also change. In order to ensure the maximum output power, it is necessary to obtain the maximum output power of the solar panel as much as possible. The MPPT tracking function of the inverter is designed for this characteristic. MPPT tracking is also called maximum power point tracking. According to calculations, the power generation of the system configured with MPPT tracking can be 50% higher than that of the system without MPPT tracking. Therefore, if you want the photovoltaic system to generate more electricity, don’t just look at the solar panels. How much of the electricity generated by the solar panels can be effectively output in the end depends on the inverter.

2. Anti-individual operation function to ensure the safety of the power grid

When installing a photovoltaic system, many people hold the mentality of "even if the power grid fails, their home can still use electricity. As everyone knows, when the power grid fails, the photovoltaic system of their home will also stop operating. The reason for this phenomenon is that now The inverter is generally equipped with an anti-islanding device. When the grid voltage is 0, the inverter will stop working. Do you feel trapped when you hear this? Don’t worry, let me explain to you. The island device is a necessary device for all photovoltaic grid-connected inverters. The reason for this is mainly for the safety of the power grid. Imagine that the power grid is out of power, and the grid staff has already gone into battle to overhaul the circuit, and your photovoltaic system It is still uploading electricity continuously...it is easy to cause safety accidents.

3. According to the output power of solar panels, automatic operation and shutdown

After sunrise in the morning, the intensity of solar radiation increases gradually, and the output of solar cells increases accordingly. When the output power required by the inverter is reached, the inverter starts to run automatically. After starting to run, the inverter will monitor the output of the solar cell components all the time. As long as the output power of the solar cell components is greater than the output power required by the inverter, the inverter will continue to run; it will stop until sunset, even on cloudy and rainy days. The inverter also works. When the output of the solar cell module becomes smaller and the output of the inverter is close to 0, the inverter will form a standby state.