A brief introduction to the working principle of Inverter:
Inverter is a direct current to alternating current (DC to AC) transformer, as the name suggests, is a reverse voltage transformer, it is actually a voltage inversion process compared to the power adapter Adapter. Power adapter is the utility grid 220V AC voltage into a stable DC output, such as the USB power supply DC 5V, while the inverter is the power adapter output DC voltage into high-frequency high-voltage AC. Today's inverters generally use PWM (Pulse Width Modulation) technology to obtain a high-power, high-efficiency AC inverter output.
Inverter working principle block diagram
Input Interface Section:
The input section normally has 3 signals, 1) DC input voltage, 2) operating control voltage, and 3) Panel current control signal. The DC input voltage is provided by the DC output from the power adapter or power board, and the operating control voltage is provided by the control chip on the main board with the value of 0 or 3V, when the operating control voltage = 0, the inverter does not work, and when the operating control voltage = 3V, the inverter is in normal operation; and the current control signal voltage is provided by the main board with the range of 0-5V, which is fed back to the PWM controller with different current control signal values. signal value is fed back to the feedback terminal of PWM controller, the current provided by the inverter to the load is also different, the smaller the value of the current control signal is, then the larger the current output from the inverter is.
Voltage start circuit:
When the working control voltage is high, the output high voltage goes to light up the backlight tube of LCD Panel.
PWM controller:
Mainly consists of has the following parts: internal reference voltage, error amplifier, oscillator and PWM, protection circuit, output transistor.
DC Conversion:
Through the MOS switching tube and energy storage inductor to form a voltage conversion circuit, the input pulse is amplified through the amplifier to drive the MOS tube to do the switching action, so that the DC voltage is charged and discharged to the inductor, so that the other end of the inductor can get the AC voltage.
LC oscillation and output circuit:
Ensure the 1500V required for lamp startup and reduce the voltage to 800V after the lamp startup.
Output Voltage Feedback:
When the high-voltage lamp works, the feedback sampling voltage plays a role in stabilizing the voltage output of the inverter.
Inverter transformer is generally more than one input, a high-voltage output, if for large screen TV in the internal multiple lamps in the LCD Panel, generally using multiple inverter boards or multiple inverters separate output. For the inverter, because of its work will produce high voltage, the internal inverter transformer, PCB, output socket, etc. in the production process, many customers require the use of UL recognized or the corresponding flame-resistant level of materials and components, in order to ensure the safety of its products.
Now in the implementation process of China Compulsory Product Certification, the aspects of the inverter safety assessment are mainly in the following areas:
1) Temperature rise
Examination of the inverter in normal operation and the occurrence of a single fault, its internal inverter transformer, PCB board and other components will not have a personal safety or affect the normal operation of the surrounding devices too high a temperature.
(2) Fire requirements
Assessment of the internal inverter transformer, PCB boards and other internal components prone to high temperatures have a certain level of fire protection and ability to ensure that they will not occur when the fire risk, as well as when the other components of the fire on the spread of flames to slow down and stop the ability.
(3) Electrical strength.
Assessment of the inverter in the work of the high voltage generated by the inverter transformer insulation is not enough to make the high voltage generated by the low voltage input part and affect the safety of users.
4) Current limiting circuit
Because the inverter is a component that generates high voltage and supplies power to the lamps of the LCD panel, the user can touch the surface of the LCD screen, and in case of damage to the LCD screen, the user may come into contact with the high voltage generated by the inverter. In this case, can not directly reduce the output voltage, we must limit the inverter output current to ensure the safety of the user, in the product safety testing, in accordance with the requirements of the current-limiting circuit assessment is particularly important. In the product safety test, it is especially important to assess the current limiting circuit according to the requirement of the current limiting circuit. If the product reports the same specification of inverter, it is also necessary to add the current limiting circuit test to the reported inverter.
The above safety testing program is just a basic requirement for the product, through a simple analysis of the inverter mode of operation and principle, so that we have a simple understanding of its safety performance, a better grasp of the correct method of use, to avoid danger, so that home appliances to better serve us and improve our quality of life.
