A power supply with a serial capacitor is used to power the LED. The current flowing through the LED is limited by the reactance of the capacitor. The connection is suitable for luminaires with a larger number of LEDs connected in series and a current of up to 50 mA. It can be used to implement luminaires up to a power input of several watts.
Losses occur in the circuit only on the protective resistor R1, the discharging resistor R2 and the rectifier diodes, the efficiency of the source is over 90%. Capacitor C2 should be 630 VDC, or you can use a 250 or 275 VAC suppression capacitor (usually labeled X2).
The table shows the current for different numbers of LEDs and for several capacitors of capacitor C2. Resistor R1 and capacitor C1 protect the LED from current pulses that can occur during sudden changes in supply voltage. C1 also reduces the ripple of the current flowing through the LED, but its effect on the mean current of the LED is small.
|1 LED||10 LED||20 LED||30 LED||50 LED||70 LED|
|C2 = 1000nF||64 mA||57 mA||47 mA||42 mA||32 mA||20 mA|
|C2 = 680nF||44 mA||39 mA||34 mA||29 mA||22 mA||17 mA|
|C2 = 470nF||30 mA||27 mA||24 mA||20 mA||15 mA|
|C2 = 330nF||21 mA||19 mA||17 mA||14 mA|
|C2 = 220nF||14 mA||13 mA||11 mA|
|LED voltage||3,5 V||35 V||70 V||105 V||165 V||230 V|
The module is designed to connect 10 LEDs in series. A current of 19 mA flows through the circuit.
Printed circuit board:
|C1||470uF/35V (voltage according to the number of LEDs)|
|C2||330n/275VAC (in table)|
|M1||graetz bridge round 1A|
|X1, X2||screw terminal for PCB, RM=5mm, 2 pin|