555 charge pump circuit for hi-side?

[jwagnerhki]

Hi,

I've read several mentions in this forum about using a 555 to create a charge pump which provides the ~15VDC supply necessary for high-side mosfet gate drive.

Couldn't find a single schematic here, though :-| Also tried googling for "555 charge pump high side" also, no useable results.

My intended use would be for a IR2110 and DC rail of 100V..350VDC. Already used bootstrap schottky diode setups in several designs, usually too glitchy and requires just too careful PCB layout design.

Would anyone be able to help me out with pointers to a schematic?

Many thanks!
- Jan

[Jaka Racman]

IR AN 978 Fig 16

[sivan_and]

Why not use high side drivers from Elantec (Intersil)..

[classd4sure]

Originally posted by sivan_and
Why not use high side drivers from Elantec (Intersil)..

You still need to power them, but I think they can be used.

[jwagnerhki]

Thanks for your fast answers!

Hmm, for Intersil/Elantec, which high side drivers exactly?

http://www.intersil.com/product_tree...ET_Drivers.asp where few I see there go only to abs max 125VDC and ~100kHz (except HIPxxx at 1..2MHz), and are bootstrap designs. For my case, IR2110 has better specs than these... :-(

The charge pump in the app note, fig 16. Is that really /the/ circuit? It looks interesting, but, isn't this just a voltage doubler that hangs on the high side (with x watts of dissipation in zener and series resistor)? And even unfortunately has a mandatory bootstrap diode to work at all :-| The bootstrap setup is what I wanted to get rid of.

Any ideas if there any charge pump circuits that would work without bootstrap diode?

- Jan

[classd4sure]

How about just a floating astable mutlivibrator... well that'd pretty well require it's own floating supply, in which case, just use a floating supply?

[sivan_and]

What abt a small flyback PSU that operates off the Vcc of

IR2110 (15volts) ..can be implemented with miniature

shielded SMD/pot ferrite core...Can't understand how can u

experience glitches with 2110 bootstrap PSU.Couple of years

ago I've built one sine wave inverter having 5KW o/p

operating off 120 volts battery driving power mosfets (6 #

IRF240 per arm of H bridge..a pair of complimentary mosfets

was used to drive power mosfets...

[jwagnerhki]

sivan_and: ok maybe a mini flyback is the way to go... or I guess I'll first try a 555 outputting 50% duty square into a small ferrite xfmr.

IR2110 has been working fine for me in apps with <100kHz, but in this class-D amp, Vs undershoots ground so Cb overcharges a bit. Also there's some mess that causes it to undercharge - the /audio/ waveform (weak) can be seen across Vb<->Vs.

Hmm maybe this is because of crappy PCB design... (?)

Here's a PCB pic from above, with components, it's the proto version (definitely not 1kW ) with IR2110 problems, mosfets have G<->S zeners, the two other TO220 parts are TC4422 non-inverting 9Ap drivers:

http://users.tkk.fi/~jwagner/electr/...halfbridge.jpg

Logic gnd joins power gnd at only one node, = lower mosfet source pin.

Spot any obvious faults there? Need top ground plane?

Thanks a lot!
(i'll try to put up a .gif of the Eagle PCB as well...)
- Jan