i want to convert 240v ac to 12v dc i have transformer, bridge rectifier,load given, load=100ohms, load current=0.12a peak voltage of secondary=16.970v rms voltage of secondary=12v output of bridge rectifier=16.970-1.4=15.57v dc how can calculate capacitor for circuit plz explain with formula and ripple voltage of capacitor thanks.....
The simple conservative estimate for the filter capacitor is f is the input mains frequency [Hz]. Vr is the allowed peak-to-peak ripple voltage. Iload=Vdc/Rload. Vdc≈Vpk-Vr/2 where Vpk is the rectifier output peak value. This is based on the 'crude' assumption that over each rectified half wave cycle, the capacitor rapidly (instantaneously) charges to the rectified peak voltage then discharges at a constant rate into the load over the rectified cycle interval T/2 where T=1/f.
Take another look at my post. If Vdc=12V and Vpk=15.57V and Vdc≈Vpk-Vr/2 then what is Vr? You also need to state the operating frequency. A word of caution: The ripple voltage will be so high that the simple relationship for calculating the capacitance will over-estimate the required value quite significantly. In this case one might be forced to consider a more accurate estimation method.
In such circumstances one would better estimate the capacitance as Where ω is the input frequency [radians/sec] NB:The arcsin() function result would be calculated in radians rather than degrees.
Simply solve for 1V peak to peak ripple and then select a larger, standard value capacitor--that will be good for most applications
In post#1 the OP specifies that the DC output is to be 12V. If the ripple is 1V p-p the (mean) output would be ~15V DC. Selecting 1V p-p therefore doesn't meet the OP's stated spec. To obtain ~12V average output the ripple would have to be more like ~7.1V. I understand this would be a poor outcome in terms of the overall performance and that a 1V p-p ripple would be more acceptable. In the end it depends on what the OP is actually required to achieve in answering the question - assuming this actually is homework.
i want to convert 240v ac to 12v dc i have transformer, bridge rectifier,load given, load=100ohms, load current=0.12a peak voltage of secondary=16.970v rms voltage of secondary=12v output of bridge rectifier=16.970-1.4=15.57v dc need correct equations for my smoothing cap can you show calculation of capacitor for this circuit please explain with this data
Curious and probably annoying that you've re-posted #1 post. If you are not getting the answers you think you need then re-stating the question in another way often helps.