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Re: [TCML] SSTC half bridge



In steady state, the 2 circuits behave exactly the same *assuming* there is
a capacitor from +340V to GND that is much bigger than the DC blocking cap,
and the stray inductances are small.

The difference between these 2 circuits, when functioning as intended, are
insignificant.  The current through the primary coil will be the same either
way, assuming the total DC blocking capacitance is the same (Cblock for a is
2X Cblock for b).  The only benefit i can see for b is that it establishes a
DC bias of 140V much faster than you would get with the leakage current of
the mosfets acting as an R-divider in case a, to charge up the DC blocker
cap to 170V.  Its a subtle difference that is not likely to matter.

Ive build drivers that use either setup, no notable differences.

Steve

On Fri, Jun 4, 2010 at 12:36 AM, Herwig Roscher <herwig.roscher@xxxxxx>wrote:

>
> Hello,
>
> I am planning on building a SSTC, driven by a half bridge of
> POWERMOSFETs. Searching the archives and the web, I found two
> topologies:
>
> a.          +340 V
>                 |
>         upper FET
>                 |
>                 *------ primary coil-----
>                 |                                    |
>          lower FET                         = dc blocking capacitor
>                 |                                    |
>             GND                             GND
>
>
> b.         +340 V
>                 |
>                 *----------------------------
>                 |                                    |
>          upper FET                        =  dc blocking capacitor
>                 |                                    |
>                 *------ primary coil-----*
>                 |                                    |
>           lower FET                        = dc blocking capacitor
>                 |                                    |
>             GND                            GND
>
> What are the pros and cons for these circuits? Could somebody please
> enlighten me?
>
> Regards,
>
> Herwig
>
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