(4) Power amplification circuit: A power amplification circuit is a type of amplification circuit designed to output higher power. It generally drives the load directly and has strong carrying capacity. The power amplification circuit adopts a simple ICL amplifier circuit.
(5) Step up transformer: The step up transformer is a common power frequency transformer, and the nominal value of the varistor is 220V. This resistor is an overvoltage protection resistor to prevent high voltage from harming personal safety.
(6) Output switching circuit: There is a double pole double throw relay with a coil working voltage of DC220V. When the input AC220V voltage is present, the double pole double throw relay will automatically switch to the common power supply by pulling in the output. When it is not present, the output will switch to the power supply provided by the boost circuit.
(7) Power detection: When the input power supply AC220V is present, the optocoupler conducts, the control relay is closed, and the boost circuit stops working. When there is no power supply input AC220V present, the voltage loss alarm circuit starts to alarm
(8) Voltage loss alarm circuit: The voltage loss alarm circuit consists of two multi harmonic oscillation circuits The audio frequency oscillation circuit has an oscillation frequency of about 2kH2 ° and a gap oscillation circuit cycle of 2Hz. It modulates the audio signal after isolation and has an alarm tone control circuit.
(9) Overcurrent protection circuit: The overcurrent protection current is composed of a sampling resistor, a transistor amplification circuit, a detection circuit, a voltage comparison circuit, and a latch circuit. The amplification circuit amplifies the voltage of the sampling resistor and adjusts the static point of the amplification circuit. The detection circuit converts the AC signal into a suitable current voltage. Overcurrent protection indicator circuit, overcurrent protection is activated when the LED lights up. The principle of overcurrent protection for APC UPS power supply is that excessive current can turn off the drive signal to protect the switch tube from burning out due to excessive current. This article uses the method of current transformer to measure current, using current transformer to measure current. Current transformers can linearly convert current into voltage, making it easy to measure current by measuring voltage. When used for measurement, current voltage transformers can be isolated from the tested circuit, resulting in minimal impact on the tested circuit. They also have low energy consumption, wide frequency band, and good signal reproducibility. The current transformer is chosen due to its advantages such as low price. The reference voltage is divided by a voltage divider circuit and connected to the same phase terminal of a voltage comparator as the given reference voltage. The inverter input current signal from the Hall current sensor is compared with the reference voltage through a filtering circuit, and the voltage comparator outputs a high level during normal operation. When a short circuit occurs, the input current of the inverter increases, causing the output voltage of the Hall current sensor to increase. The input voltage of the voltage comparator is greater than the reference voltage, and the output of the voltage comparator changes from high level to low level, thereby quickly turning off the driving signal through the control core.
(10) APC UPS power drive circuit: The drive circuit design adopts a drive chip, which has the advantages of optocoupler isolation and electromagnetic isolation, as well as fast and complete protection function and built-in dead zone. Therefore, it can improve the reliability of the control system and reduce the complexity of the circuit.