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Zener turn-on question

Started by bitrex December 8, 2017
I was playing around with the CD4093 boost converter circuit someone 
posted a while back:

<https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0>

What's the point in simulate, it's simple enough that I can just 
"simulate" on a breadboard.

Related questions: there's some relation between the Zener quiescent 
current, the inductor DCR, max output current, and number of sections I 
use to drive the inductor.

On the breadboard right now I'm using 56k resistors with a 4.7 volt 
Zener and the oscillator fed thru a second inverter with two more ganged 
sections after that to drive the inductor, trying to push about 3 volts 
in up to ~5 volts out. Even lightly loaded the Zener is turning on early 
and very sloppy-like and I'm not hitting the target.

The only small 1mH inductors I could find in stock seem to have a fairly 
high DCR, ~70 ohms, probably too high.

Any suggestions for improvement?
On 2017-12-08 13:16, bitrex wrote:
> I was playing around with the CD4093 boost converter circuit someone > posted a while back: > > <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> > > What's the point in simulate, it's simple enough that I can just > "simulate" on a breadboard. > > Related questions: there's some relation between the Zener quiescent > current, the inductor DCR, max output current, and number of sections I > use to drive the inductor. > > On the breadboard right now I'm using 56k resistors with a 4.7 volt > Zener and the oscillator fed thru a second inverter with two more ganged > sections after that to drive the inductor, trying to push about 3 volts > in up to ~5 volts out. Even lightly loaded the Zener is turning on early > and very sloppy-like and I'm not hitting the target. >
CD4000 logic is, as Jim says, like molasses at 5V. In addition only 30uA of zener current are required to turn on the NPN and unless it is a very tiny zener its leakage current will make that "sloppy". If you never need more than 5V you'd be better off with 74HC.
> The only small 1mH inductors I could find in stock seem to have a fairly > high DCR, ~70 ohms, probably too high. >
Depends on the expected load.
> Any suggestions for improvement?
A lower DCR inductor :-) And you might want to reduce the bottom 22k (would be nice to write in designators). -- Regards, Joerg http://www.analogconsultants.com/
On 12/08/2017 04:47 PM, Joerg wrote:
> On 2017-12-08 13:16, bitrex wrote: >> I was playing around with the CD4093 boost converter circuit someone >> posted a while back: >> >> <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> >> >> What's the point in simulate, it's simple enough that I can just >> "simulate" on a breadboard. >> >> Related questions: there's some relation between the Zener quiescent >> current, the inductor DCR, max output current, and number of sections I >> use to drive the inductor. >> >> On the breadboard right now I'm using 56k resistors with a 4.7 volt >> Zener and the oscillator fed thru a second inverter with two more ganged >> sections after that to drive the inductor, trying to push about 3 volts >> in up to ~5 volts out. Even lightly loaded the Zener is turning on early >> and very sloppy-like and I'm not hitting the target. >> > > CD4000 logic is, as Jim says, like molasses at 5V. In addition only 30uA > of zener current are required to turn on the NPN and unless it is a very > tiny zener its leakage current will make that "sloppy". > > If you never need more than 5V you'd be better off with 74HC.
Ok, I'm trying to recall the 74HC equivalent of the 4093..74HC132 yeah?
>> The only small 1mH inductors I could find in stock seem to have a fairly >> high DCR, ~70 ohms, probably too high. >> > > Depends on the expected load.
Was hoping for around 5 mA.
>> Any suggestions for improvement? > > > A lower DCR inductor :-)
Can do
> And you might want to reduce the bottom 22k (would be nice to write in > designators).
Hey, that schematic wasn't MY handiwork (though my penmanship probably isn't that much better)
On 12/08/2017 04:55 PM, bitrex wrote:
> On 12/08/2017 04:47 PM, Joerg wrote: >> On 2017-12-08 13:16, bitrex wrote: >>> I was playing around with the CD4093 boost converter circuit someone >>> posted a while back: >>> >>> <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> >>> >>> What's the point in simulate, it's simple enough that I can just >>> "simulate" on a breadboard. >>> >>> Related questions: there's some relation between the Zener quiescent >>> current, the inductor DCR, max output current, and number of sections I >>> use to drive the inductor. >>> >>> On the breadboard right now I'm using 56k resistors with a 4.7 volt >>> Zener and the oscillator fed thru a second inverter with two more ganged >>> sections after that to drive the inductor, trying to push about 3 volts >>> in up to ~5 volts out. Even lightly loaded the Zener is turning on early >>> and very sloppy-like and I'm not hitting the target. >>> >> >> CD4000 logic is, as Jim says, like molasses at 5V. In addition only >> 30uA of zener current are required to turn on the NPN and unless it is >> a very tiny zener its leakage current will make that "sloppy". >> >> If you never need more than 5V you'd be better off with 74HC. > > Ok, I'm trying to recall the 74HC equivalent of the 4093..74HC132 yeah? > >>> The only small 1mH inductors I could find in stock seem to have a fairly >>> high DCR, ~70 ohms, probably too high. >>> >> >> Depends on the expected load. > > Was hoping for around 5 mA. > >>> Any suggestions for improvement? >> >> >> A lower DCR inductor :-) > > Can do >
Seems I can't go too low, though, I tried a significantly (physically) larger 680 uH L with a DC resistance of only a couple ohms and it doesn't appear to want to start up with that load.
On 2017-12-08 13:58, bitrex wrote:
> On 12/08/2017 04:55 PM, bitrex wrote: >> On 12/08/2017 04:47 PM, Joerg wrote: >>> On 2017-12-08 13:16, bitrex wrote: >>>> I was playing around with the CD4093 boost converter circuit someone >>>> posted a while back: >>>> >>>> <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> >>>> >>>> What's the point in simulate, it's simple enough that I can just >>>> "simulate" on a breadboard. >>>> >>>> Related questions: there's some relation between the Zener quiescent >>>> current, the inductor DCR, max output current, and number of sections I >>>> use to drive the inductor. >>>> >>>> On the breadboard right now I'm using 56k resistors with a 4.7 volt >>>> Zener and the oscillator fed thru a second inverter with two more >>>> ganged >>>> sections after that to drive the inductor, trying to push about 3 volts >>>> in up to ~5 volts out. Even lightly loaded the Zener is turning on >>>> early >>>> and very sloppy-like and I'm not hitting the target. >>>> >>> >>> CD4000 logic is, as Jim says, like molasses at 5V. In addition only >>> 30uA of zener current are required to turn on the NPN and unless it >>> is a very tiny zener its leakage current will make that "sloppy". >>> >>> If you never need more than 5V you'd be better off with 74HC. >> >> Ok, I'm trying to recall the 74HC equivalent of the 4093..74HC132 yeah? >>
Yup. Though I usually do those with simple Schmitt inverters, not NAND. Then the transistor tugs across the cap.
>>>> The only small 1mH inductors I could find in stock seem to have a >>>> fairly >>>> high DCR, ~70 ohms, probably too high. >>>> >>> >>> Depends on the expected load. >> >> Was hoping for around 5 mA. >>
That isn't going to fly with 3V -> 5V and CD series logic.
>>>> Any suggestions for improvement? >>> >>> >>> A lower DCR inductor :-) >> >> Can do >> > > Seems I can't go too low, though, I tried a significantly (physically) > larger 680 uH L with a DC resistance of only a couple ohms and it > doesn't appear to want to start up with that load. >
I am surprised the CD4093 starts with anything at 3V. It would also be good to reduce the 100k to less than 50k and increase the 100pF if you can stomach the slight increase in idle power. -- Regards, Joerg http://www.analogconsultants.com/
On 12/08/2017 05:31 PM, Joerg wrote:
> On 2017-12-08 13:58, bitrex wrote: >> On 12/08/2017 04:55 PM, bitrex wrote: >>> On 12/08/2017 04:47 PM, Joerg wrote: >>>> On 2017-12-08 13:16, bitrex wrote: >>>>> I was playing around with the CD4093 boost converter circuit someone >>>>> posted a while back: >>>>> >>>>> <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> >>>>> >>>>> What's the point in simulate, it's simple enough that I can just >>>>> "simulate" on a breadboard. >>>>> >>>>> Related questions: there's some relation between the Zener quiescent >>>>> current, the inductor DCR, max output current, and number of >>>>> sections I >>>>> use to drive the inductor. >>>>> >>>>> On the breadboard right now I'm using 56k resistors with a 4.7 volt >>>>> Zener and the oscillator fed thru a second inverter with two more >>>>> ganged >>>>> sections after that to drive the inductor, trying to push about 3 >>>>> volts >>>>> in up to ~5 volts out. Even lightly loaded the Zener is turning on >>>>> early >>>>> and very sloppy-like and I'm not hitting the target. >>>>> >>>> >>>> CD4000 logic is, as Jim says, like molasses at 5V. In addition only >>>> 30uA of zener current are required to turn on the NPN and unless it >>>> is a very tiny zener its leakage current will make that "sloppy". >>>> >>>> If you never need more than 5V you'd be better off with 74HC. >>> >>> Ok, I'm trying to recall the 74HC equivalent of the 4093..74HC132 yeah? >>> > > Yup. Though I usually do those with simple Schmitt inverters, not NAND. > Then the transistor tugs across the cap. > > >>>>> The only small 1mH inductors I could find in stock seem to have a >>>>> fairly >>>>> high DCR, ~70 ohms, probably too high. >>>>> >>>> >>>> Depends on the expected load. >>> >>> Was hoping for around 5 mA. >>> > > That isn't going to fly with 3V -> 5V and CD series logic.
Does buffered vs. unbuffered 4000 series make a difference? Currently on the breadboard is the "B" variant.
>>>>> Any suggestions for improvement? >>>> >>>> >>>> A lower DCR inductor :-) >>> >>> Can do >>> >> >> Seems I can't go too low, though, I tried a significantly (physically) >> larger 680 uH L with a DC resistance of only a couple ohms and it >> doesn't appear to want to start up with that load. >> > > I am surprised the CD4093 starts with anything at 3V. > > It would also be good to reduce the 100k to less than 50k and increase > the 100pF if you can stomach the slight increase in idle power. >
Heh, into only the IC itself and a 100nF bypass cap as a load the circuit as it is now starts up and oscillates all the way down to ~1.7 volts
On 2017-12-08 14:38, bitrex wrote:
> On 12/08/2017 05:31 PM, Joerg wrote: >> On 2017-12-08 13:58, bitrex wrote: >>> On 12/08/2017 04:55 PM, bitrex wrote: >>>> On 12/08/2017 04:47 PM, Joerg wrote: >>>>> On 2017-12-08 13:16, bitrex wrote: >>>>>> I was playing around with the CD4093 boost converter circuit someone >>>>>> posted a while back: >>>>>> >>>>>> <https://www.dropbox.com/s/q0jiimbllgiuew0/micropowerBoost.pdf?dl=0> >>>>>> >>>>>> What's the point in simulate, it's simple enough that I can just >>>>>> "simulate" on a breadboard. >>>>>> >>>>>> Related questions: there's some relation between the Zener quiescent >>>>>> current, the inductor DCR, max output current, and number of >>>>>> sections I >>>>>> use to drive the inductor. >>>>>> >>>>>> On the breadboard right now I'm using 56k resistors with a 4.7 volt >>>>>> Zener and the oscillator fed thru a second inverter with two more >>>>>> ganged >>>>>> sections after that to drive the inductor, trying to push about 3 >>>>>> volts >>>>>> in up to ~5 volts out. Even lightly loaded the Zener is turning on >>>>>> early >>>>>> and very sloppy-like and I'm not hitting the target. >>>>>> >>>>> >>>>> CD4000 logic is, as Jim says, like molasses at 5V. In addition only >>>>> 30uA of zener current are required to turn on the NPN and unless it >>>>> is a very tiny zener its leakage current will make that "sloppy". >>>>> >>>>> If you never need more than 5V you'd be better off with 74HC. >>>> >>>> Ok, I'm trying to recall the 74HC equivalent of the 4093..74HC132 yeah? >>>> >> >> Yup. Though I usually do those with simple Schmitt inverters, not >> NAND. Then the transistor tugs across the cap. >> >> >>>>>> The only small 1mH inductors I could find in stock seem to have a >>>>>> fairly >>>>>> high DCR, ~70 ohms, probably too high. >>>>>> >>>>> >>>>> Depends on the expected load. >>>> >>>> Was hoping for around 5 mA. >>>> >> >> That isn't going to fly with 3V -> 5V and CD series logic. > > Does buffered vs. unbuffered 4000 series make a difference? Currently on > the breadboard is the "B" variant. >
Normally you'd want the buffered one. Non-buf is for crystal oscillators and when using CD-logic for analog purposes.
>>>>>> Any suggestions for improvement? >>>>> >>>>> >>>>> A lower DCR inductor :-) >>>> >>>> Can do >>>> >>> >>> Seems I can't go too low, though, I tried a significantly (physically) >>> larger 680 uH L with a DC resistance of only a couple ohms and it >>> doesn't appear to want to start up with that load. >>> >> >> I am surprised the CD4093 starts with anything at 3V. >> >> It would also be good to reduce the 100k to less than 50k and increase >> the 100pF if you can stomach the slight increase in idle power. >> > > Heh, into only the IC itself and a 100nF bypass cap as a load the > circuit as it is now starts up and oscillates all the way down to ~1.7 > volts
Without an inductor? I wouldn't do that, it could fry the load and the IC. -- Regards, Joerg http://www.analogconsultants.com/
On 12/08/2017 05:44 PM, Joerg wrote:

>>>>>>> Any suggestions for improvement? >>>>>> >>>>>> >>>>>> A lower DCR inductor :-) >>>>> >>>>> Can do >>>>> >>>> >>>> Seems I can't go too low, though, I tried a significantly (physically) >>>> larger 680 uH L with a DC resistance of only a couple ohms and it >>>> doesn't appear to want to start up with that load. >>>> >>> >>> I am surprised the CD4093 starts with anything at 3V. >>> >>> It would also be good to reduce the 100k to less than 50k and increase >>> the 100pF if you can stomach the slight increase in idle power. >>> >> >> Heh, into only the IC itself and a 100nF bypass cap as a load the >> circuit as it is now starts up and oscillates all the way down to ~1.7 >> volts > > > Without an inductor? I wouldn't do that, it could fry the load and the IC. >
No, no, that's with the L connected and the bench voltage connected to the inductor as shown in the diagram.
On 12/08/2017 06:19 PM, bitrex wrote:
> On 12/08/2017 05:44 PM, Joerg wrote: > >>>>>>>> Any suggestions for improvement? >>>>>>> >>>>>>> >>>>>>> A lower DCR inductor :-) >>>>>> >>>>>> Can do >>>>>> >>>>> >>>>> Seems I can't go too low, though, I tried a significantly (physically) >>>>> larger 680 uH L with a DC resistance of only a couple ohms and it >>>>> doesn't appear to want to start up with that load. >>>>> >>>> >>>> I am surprised the CD4093 starts with anything at 3V. >>>> >>>> It would also be good to reduce the 100k to less than 50k and increase >>>> the 100pF if you can stomach the slight increase in idle power. >>>> >>> >>> Heh, into only the IC itself and a 100nF bypass cap as a load the >>> circuit as it is now starts up and oscillates all the way down to ~1.7 >>> volts >> >> >> Without an inductor? I wouldn't do that, it could fry the load and the >> IC. >> > > No, no, that's with the L connected and the bench voltage connected to > the inductor as shown in the diagram.
I'll draw a schematic of exactly how I have things connected for clarity/specific advice as soon as I get a chance and double-check all the component values, I understand it's hard to know exactly what's going on when what I've built is not exactly the same as the original schematic
On 2017-12-08 15:29, bitrex wrote:
> On 12/08/2017 06:19 PM, bitrex wrote: >> On 12/08/2017 05:44 PM, Joerg wrote: >> >>>>>>>>> Any suggestions for improvement? >>>>>>>> >>>>>>>> >>>>>>>> A lower DCR inductor :-) >>>>>>> >>>>>>> Can do >>>>>>> >>>>>> >>>>>> Seems I can't go too low, though, I tried a significantly >>>>>> (physically) >>>>>> larger 680 uH L with a DC resistance of only a couple ohms and it >>>>>> doesn't appear to want to start up with that load. >>>>>> >>>>> >>>>> I am surprised the CD4093 starts with anything at 3V. >>>>> >>>>> It would also be good to reduce the 100k to less than 50k and increase >>>>> the 100pF if you can stomach the slight increase in idle power. >>>>> >>>> >>>> Heh, into only the IC itself and a 100nF bypass cap as a load the >>>> circuit as it is now starts up and oscillates all the way down to ~1.7 >>>> volts >>> >>> >>> Without an inductor? I wouldn't do that, it could fry the load and >>> the IC. >>> >> >> No, no, that's with the L connected and the bench voltage connected to >> the inductor as shown in the diagram. > > I'll draw a schematic of exactly how I have things connected for > clarity/specific advice as soon as I get a chance and double-check all > the component values, I understand it's hard to know exactly what's > going on when what I've built is not exactly the same as the original > schematic
Good idea. A scanned hand sketch is fine and it doesn't have to be pretty. Even beer or coffee stains are ok on this newsgroup :-) -- Regards, Joerg http://www.analogconsultants.com/