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|  | Anonymous
on 11/19/2008 at 01:00 AM
| Category(s): | Technical Questions, power.national.com |
| Subject: | Problem with inductive loads SEPIC LM3488 |
| Message: (Notified via email on every direct response) |
Hello everybody, I need your help.
I am designing a SEPIC converter with IC LM3488. Here there are my requeriments:
Vin -> 23 ~ 25V
Vout -> 24V
Iout -> 1A
The squematic used is attacked in this post
Calculated and used components:
Cin = 10uF / 50V
Q1 = IRFB23N15D
L1 = L2 = 40uH / 2A
Cs = 2,2uF / 25V / Ceramic
D1 = http://es.farnell.com/vishay/ss3p5-e3-84a/diode-rectifier-schottky-3a-50v/dp/1570281
Cout =
1-. 0,47 uF / 50 V ceramic capacitor to reduce spikes at the output
2-. 470 uF / 25V electrolitic for bulk capacitance
Rsense = 0.05 Ohm
R1 = 20 kOhm
R2 = roughly 1kOhm (24v output)
This is the problem:
When this circuit works without load, the output voltage is good (24v)
But when I connect a strong solenoid (coil), the output voltage decrease to 19V, and there are some resonances each time the MOSFET switches.
I guess that the problem can be resolved configuring the compensation design. Could it be?
How would you develop this desing?
Thank you very much.
Attached File - sepic.JPG
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