The LinkSwitch-TN supply shown in Figure 1 provides a constant current output of up to 9 W at a maximum output voltage of 70 VDC, ideal for driving LEDs. A passive valley-fill power factor correction (PFC) circuit gives the supply a power factor greater than 0.92, which meets requirements of ENERGY STAR SSL for commercial applications. Care has been taken such that the supply also meets EN55015B EMI requirements.Line fuse F1 protects the power supply in case of catastrophic failures. Capacitors C6 and C10 provide differential filtering. EMI is mitigated by inductors L1 and L2 along with resistors R15 and R16.Full wave rectification is accomplished by diodes D5-D8. Diodes D2, D3 and D4, along with capacitors C1 and C2, form the valley fill circuit and provide power factor correction.source

The schematic shown in Figure above is a 20 V, 14 W constant voltage (CV) and constant current (CC) output power supply. The light output from an LED array is proportional to the current fl owing through it. As such, LED drivers should have a constant current as opposed to a constant voltage output. In this design, the DC output is not isolated from the AC input, and therefore the LED array and enclosure must provide safety isolation from the user.The AC input is rectifi ed and fi ltered by BR1, C1 and C2. Inductor L1 forms a π fi lter with C1 and C2 and provides EMI filtering. Fuse F1 provides protection against catastrophic failure.To allow the supply to operate unloaded without damage, CV regulation at ~21 V is provided by Zener diode VR2.source

The schematic for a universal input 12 V, 350 mA CV/CC power supply for LED driver applications using the LinkSwitch-II product LNK605DG in a tapped-inductor nonisolated buck converter confi guration.A tapped buck topology is ideal for converters with a high ratio of voltage input to voltage output: It provides current multiplication on the output, making it possible to use this variant of a buck topology in applications requiring output currents greater than twice the device current limit.source

The schematic for a universal input, 7.6 V, 700 mA CV/CC power supply for LED driver applications, using the LinkSwitch-II product LNK606PG in a fl yback confi guration.The LNK606PG (U1) combines a power switching device,oscillator, CV/CC control engine, and startup and protection functions in one IC.source

The circuit to light LED with single 1.5V battery is usually based on a blocking oscillator or a charge-pumped voltage doubler.This is another (but similar to charge pump) way to flash LED with 1.5V battery. The base-R voltage becomes nearly double the Vcc while making oscillation timing of astable multivibrator. LED can be flashed if it is attached aside. Since the LED discharges the C electricity, oscillator timing is shortened.source