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Китайцы уже пару лет Step-Down используют собственной разработки. В лампах малой мощности могут применять даже без конденсатора после выпрямителя сетевого напряжения. https://mysku.ru/blog/china-stores/47986.html

BP9916C is a high precision Buck constant current LED driver. The device operates in critical conduction mode and is suitable for 85Vac~265Vac universal input offline LED lighting. The BP9916C integrates a 500V power MOSFET. With patent pending MOSFET driving technique, the operating current of the IC is as low as 180uA. It doesn’t need the auxiliary winding for VCC supply. It can achieve excellent constant current performance with very few external components, so the system cost and size are minimized. BP9916C utilizes patent pending current control method. It can achieve precise output current and excellent line regulation. The driver operates in critical conduction mode, the output current does not change with the inductance and output voltage. The BP9916C offers rich protections to improve the system reliability, including LED short circuit protection, VCC under voltage protection and thermal regulation function.