Hi

We have to build a AC to DC PSU on friday, using the following schematics

The AC input is 15 V 50Hz, and the output must be: 9V 100mA

I need help with these problems:

1) Dimension of the Capacitor.

2) What voltage should the zenierdiode be on

3 How big should R1 be

4) Effekt lost in Q1

1) Now for the capacitor i found the 10% ripple is fine (Power Supplies)

But if i want 5% is this the right way to do it:

Vc=Vs*(1-e^(-t/RC))

15*5% = 15*(1-e^(-0.01sec/x) that gives

2) Q1 needs 0.7 volts to work, so the zenier should be able to handle output + VQ1

Thats 9v + 0.7V = 9.7V

Is this right?

3) R1 = (15V - 9.7)/(Izenier + IQ1) Or is it 15V - (9.7 + 0.7V)/(Izenier + IQ1) 0.7V for the zenier?

4) Im lost on this one :S

Thx for your time

We have to build a AC to DC PSU on friday, using the following schematics

The AC input is 15 V 50Hz, and the output must be: 9V 100mA

I need help with these problems:

1) Dimension of the Capacitor.

2) What voltage should the zenierdiode be on

3 How big should R1 be

4) Effekt lost in Q1

1) Now for the capacitor i found the 10% ripple is fine (Power Supplies)

But if i want 5% is this the right way to do it:

Vc=Vs*(1-e^(-t/RC))

15*5% = 15*(1-e^(-0.01sec/x) that gives

**x=0,00244 F**The 0.01 sec is from the 50Hz AC to 100Hz DC.2) Q1 needs 0.7 volts to work, so the zenier should be able to handle output + VQ1

Thats 9v + 0.7V = 9.7V

Is this right?

3) R1 = (15V - 9.7)/(Izenier + IQ1) Or is it 15V - (9.7 + 0.7V)/(Izenier + IQ1) 0.7V for the zenier?

4) Im lost on this one :S

Thx for your time