HVDC Capacitor Charger Help

[Goature]

Hello! I'm working on a HVDC capacitor charger. I've made it work, and it charges the capacitors to around 400V. This is the circuit:



... and here's my problem:

When i discharge the capacitors over a large inductor (you can probably figure out what i'm doing here ) different parts of the circuit fails; specially the 555 and the mosfet. I've concluded that it's probably caused by a large negative ripple the second the inductor is discharging. How can i protect my circuit from this ripple, and still get it to charge as it sould? (U2 and U3 are connected to the capacitors)

Bonus round: Do you have other improvements for the circuit?

Thanks!

[johansen]

you have to disconnect the capacitor from the charging circuit.
when you discharge a capacitor into an inductor, the energy is conserved, the current will continue to flow through the boost diode and the mosfet body diode.

most likely neither of which can handle the current, and the leakage inductance of the circuitry means some of that voltage will blow up everything else as well.

[Goature]

...the current will continue to flow through the boost diode and the mosfet body diode.

That's true! I forgot to mention that the diode also blows up often. I guess a hefty relay of some sort would help? Maybe a smaller contactor? Got to look into that!

[tautech]

Glaring omissions to manage the Back EMF are:
Snubber
Diode ratings ?
Series diode before L1
IC de-coupling cap

EDIT
And R3 4R7
R4 1K

[Goature]

Diode ratings ?

D1 is a MUR1560 (http://www.onsemi.com/pub_link/Collateral/MUR1520-D.PDF):
VRRM: 600V
Average current: 15A

D2 is a simple 1N4007 (1000V, 1A)

Thanks for the suggestions!

[max_torque]

For anything like this^^ you can't beat a proper physical "disconnect".  Use a relay with suitable rating (and contact gap!) to break both the +ve and ground lines to the HVDC cap and firing circuit

[doktor pyta]

Hi
If You want to obtain high efficiency it's better to have current- control SMPS IC.
Similar thread was discussed few years ago on a Polish forum.
Below link.
http://www.elektroda.pl/rtvforum/topic556770-0.html
The guys are helping each other and the final schematic is the "schemat4.gif".
You should use Google translator, but basically schematics are universal language. Like music...

[Goature]

Similar thread was discussed few years ago on a Polish forum.
Below link.
http://www.elektroda.pl/rtvforum/topic556770-0.html
The guys are helping each other and the final schematic is the "schemat4.gif".

Very interessting! I'm going to have a look at that!