The elevator system is a special equipment closely related to personal safety. It has its special electrical complexity. Emergency lighting is an important part of it. It is especially important to ensure the reliability of the elevator emergency lighting system. Traditional emergency lighting basically uses incandescent lamps, but it has some drawbacks, such as high power consumption, low energy efficiency, low illumination, and short service life.
With the improvement of LED performance, LED has gradually replaced incandescent lamps as emergency lighting for elevators due to its environmental protection, energy saving, shock resistance and long service life, which better overcomes these drawbacks of incandescent lamps. Due to the high requirements of LEDs for power supply, the choice of stable and reliable, durable emergency lighting solutions and optimized drive power can not only reduce the maintenance of emergency lighting systems, but more importantly, improve the operating efficiency and reliability of elevator systems. It is of great significance to ensure the safe operation of elevators.
1, LED emergency lighting drive power supply works
According to the basic working principle of the emergency backup power supply, the LED emergency lighting drive power supply should meet the following requirements: when there is mains supply, it is directly powered by the mains, and the AC/DC drive control circuit is used to provide low-voltage DC power supply, mainly for normal maintenance. The LED luminaire is powered, and the backup battery that comes with the system is charged; in the event of a fault, or when the utility power is cut off, the emergency backup battery is used to power the electrical equipment, including the LED emergency light.
According to this working principle, the LED emergency lighting driving power supply consists of four parts (as shown in Figure 1).
In Figure 1, the four dark modules are the basic functional modules of the LED emergency lighting drive power supply. Among them, the AC/DC constant voltage driving circuit is used for charging the battery by the mains, and also providing driving power for other DC power equipment. The input power selection auxiliary circuit is to control the battery to have no output when there is mains supply, and only the battery has a voltage output in the emergency state. The LED emergency drive circuit is used to drive the LED emergency light.
Since the LED requires a specific driving power supply to provide a stable current and voltage to work reliably, the design of the driving circuit for the LED emergency light is particularly important. In addition, the battery is an integrated component that is independent of the circuit design. Therefore, the circuit design is mainly AC/DC constant voltage driving circuit, input power selection auxiliary circuit, and LED emergency lighting driving circuit is composed of three modules. The circuit design of these three modules will be mainly introduced below.
2, LED emergency lighting drive power circuit design
This part focuses on the three circuit design parts of the LED emergency lighting drive power supply, namely AC/DC constant voltage drive circuit, input power supply selection auxiliary circuit and LED drive circuit. The AC/DC constant voltage driving circuit and the input power selection auxiliary circuit together provide a stable DC input voltage source for the LED emergency lighting driving circuit, and the LED emergency lighting driving circuit directly drives the LED emergency after the input power source is controlled by the constant current voltage regulator. light. In the emergency state, the battery is supplied with power to the LED emergency lighting drive circuit. The LED emergency lighting drive circuit with the battery of the special application as the input power source will be highlighted.
2.1 AC / DC constant voltage drive circuit design
Switching power supply is known as high-efficiency and energy-saving power supply. It is the most efficient in energy conversion, and it is small in size and light in weight. The use of switching power supplies in emergency backup power supplies is the best way to meet the elevator application environment. What is needed is to convert from AC220V voltage to DC12V voltage, so choose the switching power supply circuit of Buck topology.
Figure 2 is a schematic block diagram of the switching power supply principle of the Buck topology.
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