Led driver and dimmer switch

LED (Light Emitting Diode) is a semiconductor electronic component that can emit light, and in the early days, it could only emit low luminosity red light. With technological innovation, today's LEDs are capable of emitting visible light, infrared, and ultraviolet light, and their luminosity has also significantly increased. However, the PN junction conduction characteristics of LED determine its ability to adapt to a very narrow range of power supply voltage and current fluctuations. A slight deviation may lead to inability to light up, serious reduction in luminous efficiency, shortened service life, and even chip burnout. The current power supply and common battery power supply are not suitable for directly supplying power to LEDs, and LED drivers solve this problem. LED driver is a power adjustment electronic device that drives the LED to emit light or ensure the normal operation of LED module components. It can drive the LED to work stably under voltage or current conditions.

There are two main technical solutions for LED drivers: linear drive and switch type drive, each with its own advantages and disadvantages, suitable for different scenarios. The switch type drive can achieve good current control accuracy and high overall efficiency, and its application methods are mainly divided into two categories: step-down and step-up. The step-down switch driver is suitable for situations where the power supply voltage is higher than the LED terminal voltage, while the step-up switch driver is suitable for scenarios where the power supply voltage is lower than the LED terminal voltage. Generally speaking, isolated drivers have high safety but relatively low efficiency; Non isolated drivers have higher efficiency, but slightly lower safety. In practical applications, the selection needs to be based on specific requirements. Linear driving is a simpler and more direct way of driving applications. In the application of lighting grade white LED, although there are problems such as low efficiency and poor adjustability, due to its simple circuit and small size, it still has many applications in some specific situations. With the increasing maturity of high power factor (PF) efficient linear LED driving technology, the performance of linear driving is also constantly improving.

Dimming technology allows users to adjust the brightness of lights according to their needs and environment, creating a suitable atmosphere and significantly saving energy. There are two main methods for LED dimming: analog dimming and PWM (pulse width modulation) dimming. PWM dimming controls the average current of the LED by adjusting the duty cycle of the pulse signal, thereby changing the brightness. The HX3143 driver supports PWM dimming frequencies between 100Hz and 50kHz, with adjustable duty cycles from 0% to 100%. The advantage of this method is that it can accurately control the average current of the LED, with high dimming efficiency. While maintaining efficient driving, it can provide stable color output and avoid color temperature drift. But PWM dimming also has its disadvantages: it is easy to produce audible noise during dimming. Analog dimming is achieved by adding an adjustable DC voltage to the control pin for dimming. The method is simple and the peripheral cost is relatively low, but it is not suitable for applications that require constant color temperature.

LED dimming faces some unique challenges. Due to the relatively small load current of LED, ordinary three terminal bidirectional thyristor switches may encounter difficulties in blocking and maintaining current characteristics. The power of LED lamps used in home lighting may be 7.5W (such as A19 bulbs -450 lumens) or more, but the steady-state current is much lower than incandescent lamps, and there will be a current peak at the beginning of each AC voltage half cycle (up to 6-8A peak, while the steady-state current is less than 100mA). Innovative solutions continue to emerge in response to these challenges. A wide dimming range LED dimming driver circuit uses a microprocessor controlled constant current circuit and current shaping circuit to divide the dimming brightness into a preset brightness range and two parts below the preset brightness range for combined control. This design expands the lower limit of the conventional brightness range, solves the limitation of ripple on brightness adjustment, and achieves a wider brightness range adjustment for LEDs. There is also patented technology that solves the problem of flashing lights during dimming. By using a unique dimming control circuit, the adjustment unit is enabled to pull down the voltage value of the reference voltage when the reference voltage is lower than the DC dimming voltage. This results in a lower DC dimming voltage required when dimming is turned off compared to when dimming is turned on, thereby achieving a delay between dimming on and off and solving the problem of flashing lights.