LED night light factory: According to the LED drive cur […]
LED night light factory: According to the LED drive current output control classification, can be divided into three dimming modes, the control circuit can also be divided into analog control and PWM control, the control circuit is usually realized by the microcontroller.
First, the main dimming technology of LED night light
The first mode of dimming is to realize the dimming of the LED night light by adjusting the LED driving current, because the brightness of the LED chip is proportional to the LED driving current.
The second type of dimming is often referred to as analog dimming or linear dimming. The advantage of the dimming mode is that when the driving current is linearly increased or decreased, the influence of the driving current overshoot on the LED chip is relatively reduced, and the control circuit has strong anti-interference. The disadvantage is that the magnitude of the drive current will have a certain effect on the color temperature of the LED chip.
The third mode of dimming is pulse-light modulation. In this way, the driving current is square wave-shaped by a certain control, and the pulse width is variable. The pulse width adjustment changes the time during which the LED night light is continuously lit, and the output power is also changed, thereby achieving the purpose of energy saving. The frequency is generally controlled at 200 Hz to 10 kHz. Due to the retention of human eye vision, the flicker of the light source during the dimming process is not felt. The advantage of this type of dimming method is that who can improve the LED is to talk about heat dissipation. The disadvantage is that the overshoot of the driving current has a certain influence on the life of the LED chip.
Second, the composition and future development of the dimming system
Perfect intelligent control should have manual control, intelligent control, light control, time control and fault alarm control functions. When the sun goes down, the sky will automatically light up. After 12 o'clock in the middle of the night, the illumination of the lamp can be automatically halved. After dawn, the lamp can be automatically extinguished; in special cases, the person can manually control; and in the event of a malfunction of the lamp, the control system Can automatically alarm.
The intelligent dimming system is mainly composed of a server, a central controller, a single-chip controller and a signal detection circuit.
Server: It consists of upper computer and upper computer software, which mainly realizes monitoring operation and alarm function. The server is located in a control center such as street lamp management, and its connection with the central controller can be by power carrier, network or wireless.
The central controller is responsible for accepting the signal sent by the server, decoding it and sending it to the unit controller for control, and transmitting the result of the signal detection to the server.
Signal detection circuit: detects ambient brightness, drive power voltage, and current. The detected signal is sent to the unit controller or the central controller.
Unit controller: Each LED night light is equipped with a unit controller. By receiving the command from the central controller, the LED is dimmed or turned on and off, and the driving voltage and current of the LED night light are passed through the signal detecting circuit. Send to the central controller. The fault signal is transmitted to the central controller when the LED night light fails.
At present, in the field of road lighting, the application of LED is rapidly spreading. Long life and reliability are still the first considerations, but with the development of technology, when the problem of life and reliability has been solved to a certain extent, LED lighting applications are bound to move forward toward intelligent dimming systems.