an led replaces the smoothing capacitor the internal capacitance of the led or an led array will act as smoothing capacitor when a proper switching frequency and duty cycle are chosen as shown in fig1 the capacitor less led drive circuit 100 rectifies an ac source vac using an ac dc rectifier circuit 101 the negative terminal of the rectifier circuit 101 is connected to the source of a switching transistor q 1 in parallel with a diode as shown at 104 a gate of the transistor q 1 is connected to a pulse source vpulse which switches the transistor q 1 on and off at a selected duty cycle the drain of q 1 is connected to the anode of diode d 1 and to a first lead of inductor l the cathode of diode d 1 is connected to the positive terminal of the ac dc rectifier circuit 101 an led 102 or an array of leds connected in parallel to each other is connected between the cathode of diode d 1 and a second lead of inductor l the anode of the led 102 being connected to cathode of diode d 1 and hence the positive terminal of the rectifier circuit 102 and the cathode of led 102 being connected to the second lead of the inductor l an led in conduction mode can be modeled using a resistor and an ideal diode for dc mode 200 and a capacitor and a resistor in parallel for ac mode 300 as shown in fig2 and 3 i e an led inherently exhibits capacitance which enables substitution of an led for an electrolytic capacitor in buck converter circuits in power supplies we have carried out many experimental tests to come.