At present, the LED power supply can satisfy the requirement of flicker free. Roughly:
1. increase the output electrolytic capacitor
2. using the valley filled passive PFC scheme 3, the first scheme (AC/DC, DC/DC) is the first scheme to "increase the output electrolytic capacitor". This scheme can theoretically use the AC ripple of the absorption part of the electrolytic capacitor, but the actual experience tells us that when the ripple control is within a certain range (10%), it is difficult to get in. Step down, unless the electrolytic capacitor does not cost more, it can not be fundamentally eliminated. The second way is "filling valley passive PFC", which is also the most mainstream way of processing. Non isolation schemes are commonly used in Shanghai Jingfeng Ming Yuan or Shanghai duty cycle. The isolation scheme can be implemented by core link or IWATT (the earliest scheme is now basically eliminated). The principle of the circuit is as follows. Two large capacitors and three diodes are used for power factor correction, because there is a large electrolytic capacitor behind the rectifier bridge, so the AC ripple is absorbed and the current of the inductor or transformer to the secondary part is DC.
3., the third way is to adopt the two level scheme, which can completely eliminate the influence of the AC ripple by adding a level of DC/DC on the basis of the existing isolated power supply. The electrical parameters can also be fully certified. However, the cost of this scheme has increased. It needs more power management chips and some peripheral circuits. The total cost will increase by about 7 yuan.