# ripple voltage

Discussion in 'Homework Help' started by st98, May 27, 2010.

1. ### st98 Thread Starter Member

May 27, 2010
33
1
Hi,

Anyone can help me out please:

I've designed a 9v to 30V power supply using a comparator, a square wave generator and a step-up chopper circuit. I am a bit stuck completing the project because I can't find the ripple voltage.
Vout=30V
Vin=9V
IL=50mA
F=20KHz
T=50μ

I know ΔQ/C = IΔt/C but I haven't designed a value for the capacitor yet.
I am looking for the Vrip and C values

Thank You

2. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
You probably need to specify the permissible load voltage ripple then proceed with the design on that basis. What assumptions are you making re the blocking diode drop? Also are you considering only continuous or possibly discontinuous operating mode?

3. ### st98 Thread Starter Member

May 27, 2010
33
1
the load is connected to the power supply and it is also the output of the circuit. I need 30V output and to generate that I need a proper C value to be able to stop the increase in voltage at 30V. I have a 4:1 mark to space ratio. The voltage comes through a power transistor and the diode should drop the voltage 0.6V.I am not sure what diode i used. There is also a reference voltage of 5.6 produced by a zener diode. The zener is connected at the before the comparator through a resistor. The output of the schmitt trigger should then be 5.6V as well. It is continuous mode only

Thank you

4. ### t_n_k AAC Fanatic!

Mar 6, 2009
5,448
790
Hi st98,

You still didn't answer the question about permissible load ripple voltage which one would think is a key issue in solving the problem.

You didn't mention the converter topology you are using or intend to use. Is it the usual boost type?

Rather than trying to describe in words what you have it's a lot easier for forum members if you post a legible schematic.

May 27, 2010
33
1