Are you given a ripple voltage by chance?Can someone please tell me, whats the value of this capacitor?
"Generally for DC power supply circuits the smoothing capacitor is an Aluminium Electrolytic type that has a capacitance value of 100uF or more with repeated DC voltage pulses from the rectifier charging up the capacitor to peak voltage. However, their are two important parameters to consider when choosing a suitable smoothing capacitor and these are its Working Voltage, which must be higher than the no-load output value of the rectifier and its Capacitance Value, which determines the amount of ripple that will appear superimposed on top of the DC voltage. Too low a value and the capacitor has little effect but if the smoothing capacitor is large enough (parallel capacitors can be used) and the load current is not too large, the output voltage will be almost as smooth as pure DC. As a general rule of thumb, we are looking to have a ripple voltage of less than 100mV peak to peak."no ripple voltage
@ jegues: You really cannot say that you should generally have less than 100mV pk-pk ripple. In many cases this would result in an uneconomic capacitor value, but as importantly it would result in very high peak currents in the transformer, diodes and capacitor."Generally for DC power supply circuits the smoothing capacitor is an Aluminium Electrolytic type that has a capacitance value of 100uF or more with repeated DC voltage pulses from the rectifier charging up the capacitor to peak voltage. However, their are two important parameters to consider when choosing a suitable smoothing capacitor and these are its Working Voltage, which must be higher than the no-load output value of the rectifier and its Capacitance Value, which determines the amount of ripple that will appear superimposed on top of the DC voltage. Too low a value and the capacitor has little effect but if the smoothing capacitor is large enough (parallel capacitors can be used) and the load current is not too large, the output voltage will be almost as smooth as pure DC. As a general rule of thumb, we are looking to have a ripple voltage of less than 100mV peak to peak."
You can read more about the significance of the capictor value here: http://www.electronics-tutorials.ws/diode/diode_6.html
They demonstrate it's effects in a Bridge Rectifier, similiar to a Full Wave Rectifier.
Hopefully this helps.
Thank you Adjuster, you make a very good point. I am still learning on such a topic and your comments are always provide new insight.@ jegues: You really cannot say that you should generally have less than 100mV pk-pk ripple. In many cases this would result in an uneconomic capacitor value, but as importantly it would result in very high peak currents in the transformer, diodes and capacitor.
We can illustrate this by calculating the value of capacitor needed to achieve 100mV ripple in the OPs case. We now know that his output voltage is supposed to be 9.5V, so we can estimate the load current.
Load current I = 9.5V / 330Ω = 28.8mA. Ripple voltage Vpp = 100mV, so C = 0.0288A/(2*60Hz*0.1V) = 2.4E-3F or 2400μF.
That's quite a big capacitor for just 29mA of load current. At this rate, a 1A supply would need over 80,000μF, which is pretty enormous.
@ wil321: You may be able to find the capacitor value given a (mean?) output voltage requirement, but you would also need more information, such as the transformer secondary voltage and the diode voltage drop.
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