Ultra Bright LED Lamp

Ultra Light Led is the future. The Ultra Bright LEDs works at a voltage between 3 and 3.6 V and current between 10 and 30mA. This circuit limits the current through a reactance, if instead of a reactance was used resistance need dissipate between 2 and 4 watts to produce the voltage drop necessary for the proper functioning of the circuit.
XC= 1/(2pfC) ohms
XC= Vrms /I ohms

XC: Capacitive Reactance (ohm) Ω
I: LED current (ampere)A
f: Frequency (Hertz)Hz
Vrms: Input Voltage (volt) V

Circuit A – 16 LEDS serie

Circuit with 16 LEDs (A) give a luminance equivalent of a 12W.
CX: 0.22µF/630V
C1: 22µF/100V
ZD: 48V (leds 3 V)

Circuit B – 23 + 23 LEDS

Circuito with 2 series of 23 LEDs (B) give a luminance equivalentt of a 35W bulb.
CX: 0.47mF/630V
C1: 33µF/100V
ZD: 69V/1watt (leds 3 V)
Nota- Luminance depends of LED type, can change with diferent leds.

Source:  http://www.electronica-pt.com/circuitos/en/lights/76-led-lamp-circuit.html