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High voltage pnp's (250 volts)

Started by Hul Tytus April 14, 2020
James - I should have used ATTINY13 (Atmel's AVR series microcontroller in an 
8 pin package) rather than AT13. The output, with 3 (cmos) pin's wired together, 
is, by spec, +/- 75ma. To alter your schematic a bit, the base of the fzt957 
is connected to the emiter through a 10k resister and a diode. It's connected 
to the ATTINY13's output with 1 3300pf cap directly and another 3300pf cap in 
series with a 580 ohm resistor.
   Along the lines you suggest, checking with a more powerful driver might
provide some insight. I'm hoping though to find a more effective pnp device, 
probably one designed as a switcher. 
   That's a nice looking drawing you made, truely an artist.

Hul

dagmargoodboat@yahoo.com wrote:
> On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: > > I've been ... driving the transistor from 3 pal'd AT13 > > outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias.
> I'm having trouble understanding exactly what that looks like, > but it sounds way too wimpy to drive a FZT957. Turning it on and > off quickly will take a short hefty burst, hundreds of mA at least.
> Here's my best guess at your drive (I don't know what an AT13 is).
> (view in Courier) > +250V > 3.3nF -+- > .--||--. | > | | D1 |<' Q1 > AT13 |--+--R1--+-->|--+----| FZT957A > x3 | 580 | | |\ > '--R2--' | > 10K |
> Cheers, > James Arthur
James - about your "super nice p channel fets". Know of any 250volt versions
that can be driven by 5 volts ("logic level")? That would be an attractive
direction.

Hul

dagmargoodboat@yahoo.com wrote:
> On Wednesday, April 15, 2020 at 9:26:11 AM UTC-4, piglet wrote: > > On 15/04/2020 2:16 pm, dagmargoodboat@yahoo.com wrote: > > > On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: > > >> I've been ... driving the transistor from 3 pal'd AT13 > > >> outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias. > > > > > > I'm having trouble understanding exactly what that looks like, > > > but it sounds way too wimpy to drive a FZT957. Turning it on and > > > off quickly will take a short hefty burst, hundreds of mA at least. > > > > > > Here's my best guess at your drive (I don't know what an AT13 is). > > > > > > (view in Courier) > > > C2 +250V > > > 3.3nF -+- > > > C1 .--||--. | > > > 3.3n | | D1 |<' Q1 > > > AT13 |--||--+--R1--+-->|--+----| FZT957A > > > x3 | 580 | | |\ > > > '--R2--' | > > > 10K | > > > > > > > > > > > > > I took AT13 to mean an Atmel AT-Tiny 13?
> That makes sense. So maybe the 2nd 3.3nF is a level-shift? I've > added it (C1) to the sketch. Looks wayyy too wimpy.
> > As my earlier reply to Win shows I assumed he was driving the PNP base > > from 5V levels around ground and the load was at negative HV below > > ground but your interpretion also makes sense! I wonder if a simple > > capacitive bootstrap N-ch FET would do? > > > > piglet
> There are super nice P-FETs that are easy to drive, without a BJT's > pesky saturation or storage time.
> Cheers, > James Arthur
On 15/04/2020 4:50 pm, Hul Tytus wrote:
> James - I should have used ATTINY13 (Atmel's AVR series microcontroller in an > 8 pin package) rather than AT13. The output, with 3 (cmos) pin's wired together, > is, by spec, +/- 75ma. To alter your schematic a bit, the base of the fzt957 > is connected to the emiter through a 10k resister and a diode. It's connected > to the ATTINY13's output with 1 3300pf cap directly and another 3300pf cap in > series with a 580 ohm resistor. > Along the lines you suggest, checking with a more powerful driver might > provide some insight. I'm hoping though to find a more effective pnp device, > probably one designed as a switcher. > That's a nice looking drawing you made, truely an artist. > > Hul
OK Hul, so is this your circuit? (view in Courier) +250V --+----+-------+- C1 3.3nF | | | .--||-------. 10k R2 - D1 | | | | ^ |<' Q1 AT13 |--+--R1---||--+------+----+-----| FZT957A x3 | 580 C2 3.3nF |\ | | (Adapted from Klaus and James previous ascii art). If this is now the correct circuit my observation is there is nothing to limit the peak base current except the mcu port drivers? piglet
> > dagmargoodboat@yahoo.com wrote: >> On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: >>> I've been ... driving the transistor from 3 pal'd AT13 >>> outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias. > >> I'm having trouble understanding exactly what that looks like, >> but it sounds way too wimpy to drive a FZT957. Turning it on and >> off quickly will take a short hefty burst, hundreds of mA at least. > >> Here's my best guess at your drive (I don't know what an AT13 is). > >> (view in Courier) >> +250V >> 3.3nF -+- >> .--||--. | >> | | D1 |<' Q1 >> AT13 |--+--R1--+-->|--+----| FZT957A >> x3 | 580 | | |\ >> '--R2--' | >> 10K | > > >> Cheers, >> James Arthur
On Wednesday, April 15, 2020 at 11:59:06 AM UTC-4, Hul Tytus wrote:
> > dagmargoodboat@yahoo.com wrote: > > On Wednesday, April 15, 2020 at 9:26:11 AM UTC-4, piglet wrote: > > > On 15/04/2020 2:16 pm, dagmargoodboat@yahoo.com wrote: > > > > On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: > > > >> I've been ... driving the transistor from 3 pal'd AT13 > > > >> outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias. > > > > > > > > I'm having trouble understanding exactly what that looks like, > > > > but it sounds way too wimpy to drive a FZT957. Turning it on and > > > > off quickly will take a short hefty burst, hundreds of mA at least. > > > > > > > > Here's my best guess at your drive (I don't know what an AT13 is). > > > > > > > > (view in Courier) > > > > C2 +250V > > > > 3.3nF -+- > > > > C1 .--||--. | > > > > 3.3n | | D1 |<' Q1 > > > > AT13 |--||--+--R1--+-->|--+----| FZT957A > > > > x3 | 580 | | |\ > > > > '--R2--' | > > > > 10K | > > > > > > > > > > > > > > > > > > I took AT13 to mean an Atmel AT-Tiny 13? > > > That makes sense. So maybe the 2nd 3.3nF is a level-shift? I've > > added it (C1) to the sketch. Looks wayyy too wimpy. > > > > As my earlier reply to Win shows I assumed he was driving the PNP base > > > from 5V levels around ground and the load was at negative HV below > > > ground but your interpretion also makes sense! I wonder if a simple > > > capacitive bootstrap N-ch FET would do? > > > > > > piglet > > > There are super nice P-FETs that are easy to drive, without a BJT's > > pesky saturation or storage time.
> > James - about your "super nice p channel fets". Know of any 250volt versions > that can be driven by 5 volts ("logic level")? That would be an attractive > direction. > > Hul
"Logic level" cuts down the candidates. At Digikey, there's only one (!). https://www.infineon.com/dgdl/Infineon-BSP317P-DS-v02_04-en.pdf?fileId=db3a30433b47825b013b604df1d959f2 We don't know enough about your duty cycle and such to know if the BSP317 (or two or three in parallel, if you'd rather) will fit your needs, though. Cheers, James Arthur
On Wednesday, April 15, 2020 at 12:17:43 PM UTC-4, piglet wrote:
> On 15/04/2020 4:50 pm, Hul Tytus wrote: > > James - I should have used ATTINY13 (Atmel's AVR series microcontroller in an > > 8 pin package) rather than AT13. The output, with 3 (cmos) pin's wired together, > > is, by spec, +/- 75ma. To alter your schematic a bit, the base of the fzt957 > > is connected to the emiter through a 10k resister and a diode. It's connected > > to the ATTINY13's output with 1 3300pf cap directly and another 3300pf cap in > > series with a 580 ohm resistor. > > Along the lines you suggest, checking with a more powerful driver might > > provide some insight. I'm hoping though to find a more effective pnp device, > > probably one designed as a switcher. > > That's a nice looking drawing you made, truely an artist. > > > > Hul > > > OK Hul, so is this your circuit? > > (view in Courier) > +250V > --+----+-------+- > C1 3.3nF | | | > .--||-------. 10k R2 - D1 | > | | | | ^ |<' Q1 > AT13 |--+--R1---||--+------+----+-----| FZT957A > x3 | 580 C2 3.3nF |\ > | > | > > > (Adapted from Klaus and James previous ascii art). > > If this is now the correct circuit my observation is there is nothing to > limit the peak base current except the mcu port drivers? > > piglet
I think you've gotten it piglet. And yes, the uC port pins are the peak current limiters, and given the FZT957's dismal switching, we know it's not getting enough. Cheers, James Arthur
The schematic you drew is as intended. The current from the at13 to the base via the
2 caps & 1 resistor is limited by all the components mentioned in this sentence. 

Hul

piglet <erichpwagner@hotmail.com> wrote:
> On 15/04/2020 4:50 pm, Hul Tytus wrote: > > James - I should have used ATTINY13 (Atmel's AVR series microcontroller in an > > 8 pin package) rather than AT13. The output, with 3 (cmos) pin's wired together, > > is, by spec, +/- 75ma. To alter your schematic a bit, the base of the fzt957 > > is connected to the emiter through a 10k resister and a diode. It's connected > > to the ATTINY13's output with 1 3300pf cap directly and another 3300pf cap in > > series with a 580 ohm resistor. > > Along the lines you suggest, checking with a more powerful driver might > > provide some insight. I'm hoping though to find a more effective pnp device, > > probably one designed as a switcher. > > That's a nice looking drawing you made, truely an artist. > > > > Hul
> OK Hul, so is this your circuit?
> (view in Courier) > +250V
> --+----+-------+- > C1 3.3nF | | | > .--||-------. 10k R2 - D1 | > | | | ^ |<' Q1 > AT13 |--+--R1---||--+------+----+-----| FZT957A > x3 | 580 C2 3.3nF |\ > | > |
> (Adapted from Klaus and James previous ascii art).
> If this is now the correct circuit my observation is there is nothing to > limit the peak base current except the mcu port drivers?
> piglet
> > > > dagmargoodboat@yahoo.com wrote: > >> On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: > >>> I've been ... driving the transistor from 3 pal'd AT13 > >>> outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias. > > > >> I'm having trouble understanding exactly what that looks like, > >> but it sounds way too wimpy to drive a FZT957. Turning it on and > >> off quickly will take a short hefty burst, hundreds of mA at least. > > > >> Here's my best guess at your drive (I don't know what an AT13 is). > > > >> (view in Courier) > >> +250V > >> 3.3nF -+- > >> .--||--. | > >> | | D1 |<' Q1 > >> AT13 |--+--R1--+-->|--+----| FZT957A > >> x3 | 580 | | |\ > >> '--R2--' | > >> 10K | > > > > > >> Cheers, > >> James Arthur
Thanks - I'll take a look.

Hul

dagmargoodboat@yahoo.com wrote:
> On Wednesday, April 15, 2020 at 11:59:06 AM UTC-4, Hul Tytus wrote: > > > > dagmargoodboat@yahoo.com wrote: > > > On Wednesday, April 15, 2020 at 9:26:11 AM UTC-4, piglet wrote: > > > > On 15/04/2020 2:16 pm, dagmargoodboat@yahoo.com wrote: > > > > > On Tuesday, April 14, 2020 at 5:29:20 PM UTC-4, Hul Tytus wrote: > > > > >> I've been ... driving the transistor from 3 pal'd AT13 > > > > >> outputs through 3300 pf parrallel with 3300pf in series w/580 ohms along with a diode & 10k resistor to maintain bias. > > > > > > > > > > I'm having trouble understanding exactly what that looks like, > > > > > but it sounds way too wimpy to drive a FZT957. Turning it on and > > > > > off quickly will take a short hefty burst, hundreds of mA at least. > > > > > > > > > > Here's my best guess at your drive (I don't know what an AT13 is). > > > > > > > > > > (view in Courier) > > > > > C2 +250V > > > > > 3.3nF -+- > > > > > C1 .--||--. | > > > > > 3.3n | | D1 |<' Q1 > > > > > AT13 |--||--+--R1--+-->|--+----| FZT957A > > > > > x3 | 580 | | |\ > > > > > '--R2--' | > > > > > 10K | > > > > > > > > > > > > > > > > > > > > > > > I took AT13 to mean an Atmel AT-Tiny 13? > > > > > That makes sense. So maybe the 2nd 3.3nF is a level-shift? I've > > > added it (C1) to the sketch. Looks wayyy too wimpy. > > > > > > As my earlier reply to Win shows I assumed he was driving the PNP base > > > > from 5V levels around ground and the load was at negative HV below > > > > ground but your interpretion also makes sense! I wonder if a simple > > > > capacitive bootstrap N-ch FET would do? > > > > > > > > piglet > > > > > There are super nice P-FETs that are easy to drive, without a BJT's > > > pesky saturation or storage time.
> > > > James - about your "super nice p channel fets". Know of any 250volt versions > > that can be driven by 5 volts ("logic level")? That would be an attractive > > direction. > > > > Hul
> "Logic level" cuts down the candidates. At Digikey, there's only one (!).
> https://www.infineon.com/dgdl/Infineon-BSP317P-DS-v02_04-en.pdf?fileId=db3a30433b47825b013b604df1d959f2
> We don't know enough about your duty cycle and such to know if the BSP317 > (or two or three in parallel, if you'd rather) will fit your needs, > though.
> Cheers, > James Arthur
piglet wrote...
> > On 15/04/2020, Winfield Hill wrote: >> piglet wrote... >>> Hul Tytus wrote: >>>> sci.electronics.design, comp.arch.embedded >>>> high voltage pnp's (250v) >>>> >>>> Anyone know of a good pnp transistor spec'd >>>> up to 250 volts, a probable current limit of >>>> 1 amp and designed as a switching device. >>> >>> Have you checked if the MJE5731 fits? But a >>> p-channel MOSFET may work better. These ... >> >> Folks usually use n-channel MOSFETs, with a >> flying high-side driver. IR (now Infineon), >> Fairchild (now ON), and ST have good parts >> in SO8. E.g., FAN7362, $0.70. Some parts >> include current-limiting. And for higher >> efficiency, we like to use the half-bridge >> configuration with both hi and low MOSFETs, >> and there are loads of driver ICs for that. >> See AoE x-Chapters Table 3x.5, on page 250. > >Thanks Win, I get the impression from the OP description that his load >is at 250V below ground and that is why he went for PNP? He also said it >was fixed pulses so perhaps he could use an NPN or Nch FET either >transformer or capacitively coupled?
Dunno, there's a +250V rail in one drawing. An SO8 package FAN7362 driver would work well with any of dozens of 400V n-channel MOSFETs, like a 1-ohm 70-watt DPak STD7NK40Z, for $1. -- Thanks, - Win
On Wednesday, April 15, 2020 at 11:06:54 PM UTC+2, Winfield Hill wrote:
> piglet wrote... > > > > On 15/04/2020, Winfield Hill wrote: > >> piglet wrote... > >>> Hul Tytus wrote: > >>>> sci.electronics.design, comp.arch.embedded > >>>> high voltage pnp's (250v) > >>>> > >>>> Anyone know of a good pnp transistor spec'd > >>>> up to 250 volts, a probable current limit of > >>>> 1 amp and designed as a switching device. > >>> > >>> Have you checked if the MJE5731 fits? But a > >>> p-channel MOSFET may work better. These ... > >> > >> Folks usually use n-channel MOSFETs, with a > >> flying high-side driver. IR (now Infineon), > >> Fairchild (now ON), and ST have good parts > >> in SO8. E.g., FAN7362, $0.70. Some parts > >> include current-limiting. And for higher > >> efficiency, we like to use the half-bridge > >> configuration with both hi and low MOSFETs, > >> and there are loads of driver ICs for that. > >> See AoE x-Chapters Table 3x.5, on page 250. > > > >Thanks Win, I get the impression from the OP description that his load > >is at 250V below ground and that is why he went for PNP? He also said it > >was fixed pulses so perhaps he could use an NPN or Nch FET either > >transformer or capacitively coupled? > > Dunno, there's a +250V rail in one drawing. > An SO8 package FAN7362 driver would work well > with any of dozens of 400V n-channel MOSFETs, > like a 1-ohm 70-watt DPak STD7NK40Z, for $1. >
Gatedrivers can be had for below 0.2 USD at volume But the OP is going for a cheaper solution. The level shift cap solution is about 10 times cheaper The levelshift idea is more susceptable to noise, voltage dips and surges on the 250V rail Cheers Klaus
Klaus Kragelund wrote...
> > Gatedrivers can be had for below 0.2 USD at volume > > But the OP is going for a cheaper solution. The > level shift cap solution is about 10 times cheaper
He's going for a $0.02 solution? A p-channel part will more than wipe out that savings, compared to n-channel. Maybe not compared to bipolar, but I'd check what LCSC and the Pacific rim has to offer. -- Thanks, - Win