Reply by Klaus Kragelund April 13, 20202020-04-13
On Sunday, April 12, 2020 at 4:50:59 PM UTC+2, sea moss wrote:
> > I once did a digital SMPS with what Lasse suggest here. > > > > The error signal was fed into the ADC and DMA transferred the error voltage directly to the PWM timer (so not computation involved) > > > > Around that was looped a peak current limit and soft start > > > > In this can it only replaces the PWM part > > > > You can do more by adding the loop, but then you get phase problems if you loop is not fast, wrt to the PWM frequency > > > > Cheers > > > > Klaus > > Klaus, what was the advantage of using a microcontroller? Software-adjustable dead time?
We had a microcontroller there already, so it was just to save cost. Digital control is normally slower than analog, but can remove component tolerances and cut cost In that design it controlled a half bridge converter, a boost converter, a maximum power point tracker and a backlight LED. Oh, and then also the main purpose of the product, a Modbus controller Cheers Klaus Cheers Klaus
Reply by sea moss April 12, 20202020-04-12
> What does SED have to do with academia.edu? > > -- > > Rick C.
Never mind, I misunderstood what you were saying. Yeah I can use a throwaway for that.
Reply by Ricky C April 12, 20202020-04-12
On Sunday, April 12, 2020 at 4:49:53 PM UTC-4, sea moss wrote:
> > What you don't have a crap google account for stuff like this? > > > > -- > > > > Rick C. > > I do for youtube, but on SED I drive without a seatbelt.
What does SED have to do with academia.edu? -- Rick C. --+ Get 1,000 miles of free Supercharging --+ Tesla referral code - https://ts.la/richard11209
Reply by Hul Tytus April 12, 20202020-04-12
The attiny25 allows use of the comparator and a pwm timer/counter at the same time. A few pennies more, though.

Hul

bitrex <user@example.net> wrote:
> On 4/10/2020 7:59 PM, Ricky C wrote: > > On Friday, April 10, 2020 at 7:19:36 PM UTC-4, sea moss wrote: > >> Seems like every time I start a new power design, I waste a bunch of time looking for the ideal PWM controller. > >> > >> At the end of the day I'd really like to have the simplest IC possible to handle just the PWM function, and I provide my own error amp, gate driver, and reference externally. The ideal part would look like this: oscillator set by resistor, comparator non-inverting input, and pulse out. Plus Vdd and ground equals 5 pins only! Does anything like this exist? > >> > >> I've also been checking out the famous TL494, and MC34063 since I have never used them. Does anyone here have horror stories from these parts that I can't infer from the datasheets? > >> > >> Another one I discovered is MCP1632, pretty simple but not quite what I'm looking for. Vdd=6V max for example, kind of sucks. I do like how they use a 50uA current source as the reference pin, so you set Vref with a resistor or drive from low-impedance source, nice. > >> http://ww1.microchip.com/downloads/en/DeviceDoc/20005254A.pdf > > > > I can't get to a 5 pin device, but I bet I can do that in a 48 pin QFN using an FPGA. ICE5LP1K-SG48ITR50, under $3.00 qty 100. > > > > There's not much in the control world that can't be done primarily digitally these days. > >
> ATTiny13A, 1k program memory, two PWM channels, 10 bit ADC, 20MHz clock. > can do all sorts of stuff with that for 40 cent in 100s
Reply by sea moss April 12, 20202020-04-12
> What you don't have a crap google account for stuff like this? > > -- > > Rick C.
I do for youtube, but on SED I drive without a seatbelt.
Reply by Ricky C April 12, 20202020-04-12
On Sunday, April 12, 2020 at 10:39:25 AM UTC-4, sea moss wrote:
> > Sloman A.W., Buggs P., Molloy J., and Stewart D. &ldquo;A microcontroller-based driver to stabilise the temperature of an optical stage to 1mK in the range 4C to 38C, using a Peltier heat pump and a thermistor sensor&rdquo; Measurement Science and Technology, 7 1653-64 (1996) > > > > Describes an example of such a circuit. We got the the low frequency content of the PWM waveform down by playing around a small programmable logic device. The device is long obsolete, but there are plenty of more modern equivalents around. > > > > -- > > Bill Sloman, Sydney > > I found this paper online, but to read it I have to let academia.edu have access to my google contacts.. WTF?! I will email you for a copy. Thanks
What you don't have a crap google account for stuff like this? -- Rick C. --- Get 1,000 miles of free Supercharging --- Tesla referral code - https://ts.la/richard11209
Reply by Phil Hobbs April 12, 20202020-04-12
On 2020-04-12 14:09, Dimiter_Popoff wrote:
> On 4/12/2020 20:03, Phil Hobbs wrote: >> On 2020-04-12 11:09, Dimiter_Popoff wrote: >>> On 4/11/2020 2:19, sea moss wrote: >>>> Seems like every time I start a new power design, I waste a bunch of >>>> time looking for the ideal PWM controller. >>>> >>>> At the end of the day I'd really like to have the simplest IC >>>> possible to handle just the PWM function, and I provide my own error >>>> amp, gate driver, and reference externally.&nbsp; The ideal part would >>>> look like this: oscillator set by resistor, comparator non-inverting >>>> input, and pulse out.&nbsp; Plus Vdd and ground equals 5 pins only!&nbsp; Does >>>> anything like this exist? >>>> >>>> I've also been checking out the famous TL494, and MC34063 since I >>>> have never used them.&nbsp; Does anyone here have horror stories from >>>> these parts that I can't infer from the datasheets? >>>> >>>> Another one I discovered is MCP1632, pretty simple but not quite >>>> what I'm looking for.&nbsp; Vdd=6V max for example, kind of sucks.&nbsp; I do >>>> like how they use a 50uA current source as the reference pin, so you >>>> set Vref with a resistor or drive from low-impedance source, nice. >>>> http://ww1.microchip.com/downloads/en/DeviceDoc/20005254A.pdf >>>> >>>> >>>> >>> >>> I am really puzzled why I am the only one on the planet doing it but >>> the perfect chip for that exists and I have been using it in countless >>> designs for decades now.It is the 74HC123, earlier the 74LS123 and even >>> earlier the 74123. >>> You have to provide an oscillator but you get two PWMs using a 123 part >>> (using half of it as oscillator is doable but very unreliable, sometimes >>> it just won't start). I typically use a 555 to get something like >>> 500 kHz and it clocks all the 123-s. >>> A *significant* benefit over using the 123 instead of an MCU with >>> timers/pwm is that there is no clock granularity. >>> >> >> So you replace Rext with a variable current source or something like >> that? > > Sort of. If I can power the error opamp off something like 10-12 volts > its output drives directly Rext (instead of having Rext to +5V). I > usually use 1/2 LMC6482 for that purpose, last 25+ years at least. > But if all I have is the (quiet) 5V supply the output of the 6482 > drives the gate of a say 2N176 (SST176 really), source to +5V, drain > into some Rext (last time it was a 2k). > >> I'd be okay using something like that closed-loop, but I don't see any >> specified min/max pulse width specs, so I wouldn't be super confident >> using it open loop.&nbsp; AFAICT it could be as bad as the HC4046, i.e. 3:1 >> or worse. > > Oh I use it closed loop only of course. One can get 0 to say 80+% duty > (you can keep the 123 constantly on by pulling the RC pin to GND, handy > for protections, gating etc., obviously the power switch is off while > the 123 is on). > That said 123 parts are remarkably similar, even between vendors, have > been over the years. > The RC is specified for time and probably they all use the same > currents/thresholds or sort of. Or it is just the same design they > all use, no idea.
Good to know, thanks! Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by Dimiter_Popoff April 12, 20202020-04-12
On 4/12/2020 20:03, Phil Hobbs wrote:
> On 2020-04-12 11:09, Dimiter_Popoff wrote: >> On 4/11/2020 2:19, sea moss wrote: >>> Seems like every time I start a new power design, I waste a bunch of >>> time looking for the ideal PWM controller. >>> >>> At the end of the day I'd really like to have the simplest IC >>> possible to handle just the PWM function, and I provide my own error >>> amp, gate driver, and reference externally.&nbsp; The ideal part would >>> look like this: oscillator set by resistor, comparator non-inverting >>> input, and pulse out.&nbsp; Plus Vdd and ground equals 5 pins only!&nbsp; Does >>> anything like this exist? >>> >>> I've also been checking out the famous TL494, and MC34063 since I >>> have never used them.&nbsp; Does anyone here have horror stories from >>> these parts that I can't infer from the datasheets? >>> >>> Another one I discovered is MCP1632, pretty simple but not quite what >>> I'm looking for.&nbsp; Vdd=6V max for example, kind of sucks.&nbsp; I do like >>> how they use a 50uA current source as the reference pin, so you set >>> Vref with a resistor or drive from low-impedance source, nice. >>> http://ww1.microchip.com/downloads/en/DeviceDoc/20005254A.pdf >>> >>> >>> >> >> I am really puzzled why I am the only one on the planet doing it but >> the perfect chip for that exists and I have been using it in countless >> designs for decades now.It is the 74HC123, earlier the 74LS123 and even >> earlier the 74123. >> You have to provide an oscillator but you get two PWMs using a 123 part >> (using half of it as oscillator is doable but very unreliable, sometimes >> it just won't start). I typically use a 555 to get something like >> 500 kHz and it clocks all the 123-s. >> A *significant* benefit over using the 123 instead of an MCU with >> timers/pwm is that there is no clock granularity. >> > > So you replace Rext with a variable current source or something like that?
Sort of. If I can power the error opamp off something like 10-12 volts its output drives directly Rext (instead of having Rext to +5V). I usually use 1/2 LMC6482 for that purpose, last 25+ years at least. But if all I have is the (quiet) 5V supply the output of the 6482 drives the gate of a say 2N176 (SST176 really), source to +5V, drain into some Rext (last time it was a 2k).
> I'd be okay using something like that closed-loop, but I don't see any > specified min/max pulse width specs, so I wouldn't be super confident > using it open loop.&nbsp; AFAICT it could be as bad as the HC4046, i.e. 3:1 > or worse.
Oh I use it closed loop only of course. One can get 0 to say 80+% duty (you can keep the 123 constantly on by pulling the RC pin to GND, handy for protections, gating etc., obviously the power switch is off while the 123 is on). That said 123 parts are remarkably similar, even between vendors, have been over the years. The RC is specified for time and probably they all use the same currents/thresholds or sort of. Or it is just the same design they all use, no idea.
> > Cheers > > Phil Hobbs > >
Dimiter ====================================================== Dimiter Popoff, TGI http://www.tgi-sci.com ====================================================== http://www.flickr.com/photos/didi_tgi/
Reply by Phil Hobbs April 12, 20202020-04-12
On 2020-04-12 11:09, Dimiter_Popoff wrote:
> On 4/11/2020 2:19, sea moss wrote: >> Seems like every time I start a new power design, I waste a bunch of >> time looking for the ideal PWM controller. >> >> At the end of the day I'd really like to have the simplest IC possible >> to handle just the PWM function, and I provide my own error amp, gate >> driver, and reference externally.&nbsp; The ideal part would look like >> this: oscillator set by resistor, comparator non-inverting input, and >> pulse out.&nbsp; Plus Vdd and ground equals 5 pins only!&nbsp; Does anything >> like this exist? >> >> I've also been checking out the famous TL494, and MC34063 since I have >> never used them.&nbsp; Does anyone here have horror stories from these >> parts that I can't infer from the datasheets? >> >> Another one I discovered is MCP1632, pretty simple but not quite what >> I'm looking for.&nbsp; Vdd=6V max for example, kind of sucks.&nbsp; I do like >> how they use a 50uA current source as the reference pin, so you set >> Vref with a resistor or drive from low-impedance source, nice. >> http://ww1.microchip.com/downloads/en/DeviceDoc/20005254A.pdf >> >> >> > > I am really puzzled why I am the only one on the planet doing it but > the perfect chip for that exists and I have been using it in countless > designs for decades now.It is the 74HC123, earlier the 74LS123 and even > earlier the 74123. > You have to provide an oscillator but you get two PWMs using a 123 part > (using half of it as oscillator is doable but very unreliable, sometimes > it just won't start). I typically use a 555 to get something like > 500 kHz and it clocks all the 123-s. > A *significant* benefit over using the 123 instead of an MCU with > timers/pwm is that there is no clock granularity. >
So you replace Rext with a variable current source or something like that? I'd be okay using something like that closed-loop, but I don't see any specified min/max pulse width specs, so I wouldn't be super confident using it open loop. AFAICT it could be as bad as the HC4046, i.e. 3:1 or worse. Cheers Phil Hobbs -- Dr Philip C D Hobbs Principal Consultant ElectroOptical Innovations LLC / Hobbs ElectroOptics Optics, Electro-optics, Photonics, Analog Electronics Briarcliff Manor NY 10510 http://electrooptical.net http://hobbs-eo.com
Reply by Dimiter_Popoff April 12, 20202020-04-12
On 4/12/2020 19:15, Phil Hobbs wrote:
> On 2020-04-12 11:09, Dimiter_Popoff wrote: >> On 4/11/2020 2:19, sea moss wrote: >>> Seems like every time I start a new power design, I waste a bunch of >>> time looking for the ideal PWM controller. >>> >>> At the end of the day I'd really like to have the simplest IC >>> possible to handle just the PWM function, and I provide my own error >>> amp, gate driver, and reference externally.&nbsp; The ideal part would >>> look like this: oscillator set by resistor, comparator non-inverting >>> input, and pulse out.&nbsp; Plus Vdd and ground equals 5 pins only!&nbsp; Does >>> anything like this exist? >>> >>> I've also been checking out the famous TL494, and MC34063 since I >>> have never used them.&nbsp; Does anyone here have horror stories from >>> these parts that I can't infer from the datasheets? >>> >>> Another one I discovered is MCP1632, pretty simple but not quite what >>> I'm looking for.&nbsp; Vdd=6V max for example, kind of sucks.&nbsp; I do like >>> how they use a 50uA current source as the reference pin, so you set >>> Vref with a resistor or drive from low-impedance source, nice. >>> http://ww1.microchip.com/downloads/en/DeviceDoc/20005254A.pdf >>> >>> >>> >> >> I am really puzzled why I am the only one on the planet doing it but >> the perfect chip for that exists and I have been using it in countless >> designs for decades now.It is the 74HC123, earlier the 74LS123 and even >> earlier the 74123. >> You have to provide an oscillator but you get two PWMs using a 123 part >> (using half of it as oscillator is doable but very unreliable, sometimes >> it just won't start). I typically use a 555 to get something like >> 500 kHz and it clocks all the 123-s. >> A *significant* benefit over using the 123 instead of an MCU with >> timers/pwm is that there is no clock granularity. > > Plus all that phase noise smooths out the spectrum. ;) > > Cheers > > Phil Hobbs >
Not much phase noise if done right (it is sensitive to power supply noise, especially via the feedback network), our (up to) 5kV HV bias for HPGe detectors has really minimal noise, a few mV (this is just noise, no ripple to speak of, the current load is what goes into the 1G feedback resistor). But it can get noisy, many years ago I learned the "quiet power" lesson the hard way :-). Dimiter