What is the purpose of C1 and L1? If you want to filter anything, it
should be AFTER you rectify the signal to DC. A series cap is going to
remove low frequencies... like DC which is attenuated very highly. So
much in fact that you can't draw a DC signal through a capacitor. That
is why your circuit is not working.
If you remove C1 and L1 the circuit will work the way you want it to I
believe. Also, with an input frequency of 15 kHz or higher, you won't
be needing 100 uF output filter capacitors for a light load. How many
mA is your load? How much ripple can you allow? Use those two values
to calculate the value of output filter capacitor you need. Once I fix
your circuit by removing the input "filter" I measure 19.14 volts out
and 38.2 mA of current into a 500 ohm load. Is that what you are
shooting for? The 100 uF cap gives around 10 mV of ripple. With
lighter loads or more ripple the cap can be smaller.
Rick
On 6/17/2011 4:44 AM, myken wrote:
Yeap, it should be a very low power power supply. Vx is not important
Vcc and Vss are.
Vin can be anything from 15Khz to 28Khz so a transformer is not the
most desired option.
I have designed two SMPS for Vcc and Vss but there load to the
rectifier are not the same, with the described result.
I will try the options suggested in this list today.
Robert.
On 17/06/11 04:13, gene glick wrote:
On 06/16/2011 02:30 PM, myken wrote:
Hello all,
I would appreciate some expert advice.
Are you trying to make a low current power supply?
I agree with DJ - the unequal loading on + and - cycle will average
to something other than zero (unequal capacitors, unequal diodes,
etc) If Vx must always be average zero - you'll need to do something
else.
If you can handle a little voltage drop, don't care what happens to
Vx, and don't mind adding a few parts, make a cheapo regulator with a
zener and BJT? (Or maybe use TL31 instead of zener)
What about a small transformer, one winding on primary, center tapped
on secondary. Add a diode and a cap for each leg - and there you go!
Anyway, there's lots of ways to do this. If regulated output is what
you want, a little more work is required.
gene
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