How to achieve the PWM dimming
Concrete realization of the PWM dimming method in series with a MOS switch is in the LED load, the anode of the LED dimming technology with a constant current power supply.
Then added to the gate of the MOS transistor with a PWM signal to quickly switch the led high bay in order to achieve dimming. Also a lot of constant current chip itself with a PWM led high bay interface, you can directly receive the PWM signal, and then output to control the MOS switch. PWM dimming method are the advantages and disadvantages?
Eliminate the dimming caused by whistling: 200Hz or above the human eye cannot detect, but until 20kHz are human auditory range. At this time it is possible to hear the slightest sound. To solve this problem there are two ways, Firstly, increasing the switching frequency above 20kHz, out of the human auditory range. However, the frequency of LED dimming technology is too high can also cause some problems, because the impact of various parasitic causes the pulse waveform distortion (along the front and rear).This reduces the accuracy of dimming. Another method is to identify the sound device to be addressed. In fact, the main sound device output ceramic capacitors, ceramic capacitors are usually made of high dielectric constant ceramic, these ceramics have piezoelectric properties. 200Hz pulse will produce a mechanical vibration and sound. The solution is the use of tantalum capacitors instead. However, the high voltage tantalum capacitors is difficult to obtain, but the price is very expensive, will increase the cost of LED dimming technology.