Please advise how to choose the input filter capacitor of the flyback power supply

灞波儿奔

Please advise how to choose the input filter capacitor of the flyback power supply [Copy link]

I would like to ask you teachers, with an AC input of 180~270VAC and an output power of 24V/2A, how should I choose the filter electrolytic capacitor at the input end of such a small flyback switching power supply? What capacity should I choose?

Is there any simple calculation or experience value you can recommend?
Thank you

luck_gfb

How many watts is the total output power? This kind of high voltage input is basically 1W about 1UF, and the full voltage range is 1W about 2UF. In addition, the customer's requirements for output voltage ripple, this capacitor will affect the low-frequency ripple of the output voltage. If you require low output ripple, you need to select a larger capacitor capacity.

qwqwqw2088

Experience value calculation

Capacitance: 24*2*2=96, select between 68uF--100uF with a margin
Withstand voltage: 270*1.414=382, select 400V

PowerAnts

qwqwqw2088 posted on 2022-3-22 20:59 Calculate the capacitance based on experience: 24*2*2=96uF Choose 100uF Withstand voltage: 270*1.414=382 Choose 400V ...

If you choose such a big one, your boss will cry to death!!!

The brand desktop 250W power supply of the last century has a 110V/230V toggle switch. The 230V is a bridge rectifier and the 110V is a series half-cycle rectifier. The filter capacitor after rectification is basically two 220uF/250V electrolytics connected in series as a half-bridge.

220V 2W 1uF, 110V 1W 2uF, these are the evidence!

maychang

luck_gfb posted on 2022-3-22 10:49 How many watts is the total output power? This kind of high voltage input is basically 1W about 1UF, and the full voltage range is 1W about 2UF. In addition, the customer's output voltage ripple...

"This capacitor will affect the low-frequency ripple of the output voltage. If you require low output ripple, you need to choose a larger capacitor."

The low-frequency ripple output by the switching power supply cannot be reduced by increasing the input filter capacitor capacity. The low-frequency component (power frequency) in the output ripple of this type of switching power supply is reduced by strong negative feedback.