Familiar with the LED products of the people know: LED life is inversely proportional to the PN junction temperature, and high power LED lamps in the limited space, can not rely on the use of larger heat sink volume to achieve the control of the temperature of LED. For example, LED track light, using DC electric fan forced cooling has become a necessity choice.

In recent years, with the continuous improvement of the level of manufacturing technology, cooling fan increased life, and even some manufacturers claim LED fan life longer than the lifetime of LED, but no matter what, cooling fan is always rely on mechanical contact is high power LED lamp can't let people rest assured that the use of the high reliability requirements in addition, an electric fan running state monitoring circuit, automatically cut off the main circuit is turned off in the fan failure, the protection of LED to prevent it from overheating damage, this idea for evaluation. Circuit of the ideas developed a fan based detection.

Through the work waveform fan we can know that the DC voltage waveforms of DC voltage capacitance coupling the rectified and filtered values are above 3 volts differential pressure, the differential pressure is applied to the comparator input can be an amplified signal can be obtained at the output end of the comparator, and then to control the opening and closing of the electronic switch.