LEDs need power when rectified ac-mains voltage drops during its cycle. The circuit in Figure 1 lets you use an inductorless, switching, offline power supply as an LED driver for emergency-exit signs and neon-light replacements. The design uses off-the-shelf components, offers efficient operation without an inductor in the dc side of the circuit, has no high-voltage capacitors, operates directly from either 120 or 230V ac, has minimal power dissipation, and has adjustable output voltage.
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