I am using a bridge rectifier power supply with a 7805 regulator IC for a microcontroller application. A capacitor (2200uF) is used for removing additional ripple. But when the microcontroller uses more power the DC output shows some ripple, the entire circuit draws about 150mA. How can I remove it completely?
Electronic – Ripple in the power supply
linear-regulatorpower supplyripple
Related Topic
- Need circuit for 12 volt 2 Amp step down power supply from 18 volt 1.5 Amp Input
- Electrical – Removing ripple in DC supply
- Electronic – A question about sizing capacitor to mitigate the ripple of a DC-DC converter output
- Electronic – High Power Series Pass Regulator Design
- Electrical – Calculating the ripple voltage from a standard wall adapter power supply
Best Answer
A fullwave rectified power supply below will have ripple due to charging and discharging of the bulk capacitors.
(source)
(source)
where the ripple voltage is $$V_{pp}=\dfrac{I}{2fC}$$ and I is the load current, C is the capacitance and f is the mains frequency.
So as the load current increases so does the ripple. To reduce this ripple you need to increase the bulk capacitance.
This is followed by a 7805 which should reduce that ripple by its RR (ripple rejection), which is about 60dB for the 7805. So Vpp in your first calculation should be reduced by about 1000.
If this is not happening for you check the dropout of the 7805 is respected, i.e. you need the input to be at least 2.0V more than the output i.e 7V min and this needs to be the case even under full load because the transformer output voltage will reduce under load.