The voltage rating of the 47uf capacitor should be 50 volts.
Check that you didn't install it backwards.
Check that you didn't install it backwards.
I recommend you do remove the 47uF tantalum. It is overshadowed by the 6800uF electrolytic, and does not really add to hi-freq noise cancellation. Replace it with one or two 100nF ceramics.
Some tantalum types (like solid tantalum) are not very good with high ripple currents. I have seen some self-healing tantalums explode violently in some (test) conditions. They seem to be limited in esr dissipation.
Bouke
Some tantalum types (like solid tantalum) are not very good with high ripple currents. I have seen some self-healing tantalums explode violently in some (test) conditions. They seem to be limited in esr dissipation.
Bouke
- yes i use 50V 47uF tamtalum capacitor. At first, i have a 3A fuse attach in the circuit before the voltage pass through the 47uF capacitor, when i turn on the power, the fuse blow! And then i bypass the fuse, turn on the power again, and this time the 47uF capacitor blow!
- Is there anything to do with the diode(1N5402) and the 6800uF 50V capacitor?? Maybe i should change the diode bridge rectifier and change the capacitor to >20,000uF???
- See, i attach the schematic into multisim, and it seems like not really stabil when i view the osciloscope.
- Any other suggestion for the schematic???more reliable......??
- Is there anything to do with the diode(1N5402) and the 6800uF 50V capacitor?? Maybe i should change the diode bridge rectifier and change the capacitor to >20,000uF???
- See, i attach the schematic into multisim, and it seems like not really stabil when i view the osciloscope.
- Any other suggestion for the schematic???more reliable......??
It oscillates -- this is a switching regulator design -- and you have to pay very careful attention to the current handling capabilities of the capacitors --
Tantalum capacitors are polarized. Are you sure that you are not connecting them backwards? They usually have a small '+' sign printed near the positive leg.
Jennice said:
Yes, the schematic is identical to the one found on National Semiconductor's website --
An externally hosted image should be here but it was not working when we last tested it.
jamesbooi said:
Tantal caps have bad habit to go dead-short and if availlable current is big enough they explode. They dont like heat, overvoltage(spikes?!) and especially not reverse-polarity. Ripple-current handling capacity varies wildly depending on manufacturer and series. Try something like 470uF 50v al-electrolytic + 100nF ceramics.
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