This method utilizes linear regulator to regulate "220V Cooling Fan" DC voltage, which requires fans to work compared with the PWM control mode over a wide voltage range, the advantage of being able to use the speed and alarm sensors; drawback is power-hungry, start and stop the problem to be solved. In linear regulator control "220V Cooling Fan" when the DC voltage across, although the power consumption will generate heat, but at maximum refrigeration and refrigeration state minimum power consumption was approximately zero. Because the maximum refrigeration, adjust the voltage difference across the tube is approximately zero; adjust the current tube on the minimum refrigeration is approximately zero, so "220V Cooling Fan" power is approximately zero.