Brightness adjustment circuit using gate-controlled switch

The brightness adjustment circuit using gate switch is shown in the figure. This circuit has the following characteristics: First, a CMOS gate circuit is used to control the on and off of the LX1970 power supply. The LX1970 is powered on only when the output of the gate circuit is high. Since the LX1970 is a micro-power device, the power supply voltage can be provided by the gate circuit; second, an isolation diode (VD) is connected in series at the SRC end. When the LX1970 is powered off, VD is cut off, which can play an isolation role, so that the brightness signal cannot be added to the LX1970, which can play a protective role; third, the 3.3V DC voltage signal and the PWM signal can be equivalent to the two input signals of the logic OR gate. Therefore, changing the DC voltage can also adjust the brightness. VD can choose 1N4148 high-speed switch silicon diode.