Forums

Emerson LPS-10x-M Alternatives

Started by Tim Wescott April 9, 2013
On Tue, 9 Apr 2013 21:59:16 -0700 (PDT), Bill Sloman
<bill.sloman@ieee.org> wrote:

>On 10 Apr, 13:08, John Larkin ><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott <t...@seemywebsite.please> wrote:
[snip].
>> >> >When the motor starts to draw power the motor rail drops: when it drops >> >down to match the power supply voltage things are switched on again and >> >it draws power from the supply. >> >> That sounds a little tricky. You could just hang an active zener across the >> power supply output to clamp at, say, 25 volts. That might keep the ps from >> crowbarring, too. >> >> I'm sure Jim would be delighted to design an accurate, 10 amp active zener >> circuit for you.
More demented snarkiness. But rather trivial to design, even with off-the-shelf discrete's... think a TL431 plus a power PNP.
> >He'd probably expect to get paid,
I've provided tons of schematics here, without remuneration (for Larkin and the other low life here, "remuneration" means "paid" ;-)
>and application specific integrated >circuits used to need potential sales in excess of 100,000 units back >when I knew anything about it.
The admission price has nothing to do with unit count... figure at least $ 1Million annually to the foundry. [snip] ...Jim Thompson -- | James E.Thompson | mens | | Analog Innovations | et | | Analog/Mixed-Signal ASIC's and Discrete Systems | manus | | Phoenix, Arizona 85048 Skype: Contacts Only | | | Voice:(480)460-2350 Fax: Available upon request | Brass Rat | | E-mail Icon at http://www.analog-innovations.com | 1962 | I love to cook with wine. Sometimes I even put it in the food.
> > >> That sounds a little tricky. You could just hang an active zener across the > >> power supply output to clamp at, say, 25 volts. That might keep the ps from > >> crowbarring, too. >
agreed, if a small SW error is fatal to the hardware, you are asking for trouble.. you said efficiency is not an issue, why not a big old diode, Shottky if you prefer, in series with the PS output, that is fail safe. and I guess you need the zener also Mark
On Wed, 10 Apr 2013 08:37:19 -0700, Jim Thompson wrote:

> On Tue, 9 Apr 2013 21:59:16 -0700 (PDT), Bill Sloman > <bill.sloman@ieee.org> wrote: > >>On 10 Apr, 13:08, John Larkin >><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >>> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott >>> <t...@seemywebsite.please> wrote: > [snip]. >>> >>> >When the motor starts to draw power the motor rail drops: when it >>> >drops down to match the power supply voltage things are switched on >>> >again and it draws power from the supply. >>> >>> That sounds a little tricky. You could just hang an active zener >>> across the power supply output to clamp at, say, 25 volts. That might >>> keep the ps from crowbarring, too. >>> >>> I'm sure Jim would be delighted to design an accurate, 10 amp active >>> zener circuit for you. > > More demented snarkiness. > > But rather trivial to design, even with off-the-shelf discrete's... > think a TL431 plus a power PNP. > > >>He'd probably expect to get paid, > > I've provided tons of schematics here, without remuneration (for Larkin > and the other low life here, "remuneration" means "paid" ;-) > >>and application specific integrated >>circuits used to need potential sales in excess of 100,000 units back >>when I knew anything about it. > > The admission price has nothing to do with unit count... figure at least > $ 1Million annually to the foundry.
Well, yes. Which means that the per-piece price is pretty much (admission price) / (volume) until the volume gets pretty damned big. Unless someone wants to pay you $2e6 for one chip, if you want to make a profit on it you have to sell lots and lots. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Tue, 09 Apr 2013 20:08:37 -0700, John Larkin wrote:

> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott > <tim@seemywebsite.please> wrote: > >>On Tue, 09 Apr 2013 16:51:46 -0700, John Larkin wrote: >> >>> On Tue, 09 Apr 2013 18:17:07 -0500, Tim Wescott <tim@seemywebsite.com> >>> wrote: >>> >>>>On Tue, 09 Apr 2013 15:52:40 -0700, John Larkin wrote: >>>> >>>>> On Tue, 09 Apr 2013 17:37:22 -0500, Tim Wescott >>>>> <tim@seemywebsite.com> wrote: >>>>> >>>>>>So, I'm working on a motor drive board for a customer. Due to a >>>>>>desire for performance improvements within the existing space, we're >>>>>>going from the traditionally-accepted brute-force power supply to a >>>>>>switcher. >>>>>> >>>>>>I have this nice board and software set that's carefully designed to >>>>>>treat the power supply with kid gloves -- and it works very well >>>>>>with the power supply that we used for prototyping. >>>>>> >>>>>>But for space reasons they went out and found what appears to be the >>>>>>smallest possible power supply with the apparent specifications >>>>>>needed (24V and 10A): >>>>>> >>>>>>http://www.powerconversion.com/assets/lps200-m_ds_1226129797.pdf >>>>>> >>>>>>It's not that this power supply sucks, per se. It's just that >>>>>>things that work just fine with the original supply (A TDK/Lambda >>>>>>SWS300-24) make the Emerson supply either exceedingly unhappy or >>>>>>downright dead. Worse, I'm not sure what's taking out the power >>>>>>supplies. >>>>>> >>>>>>So -- >>>>>> >>>>>>Does anyone have any mileage with these Emerson supplies? After I >>>>>>told the customer "why yes, that should do" I began to notice the >>>>>>name "Emerson" on this group, and the view of their stuff seems to >>>>>>be pretty dim. I'd like to know if you feel these are OK, or >>>>>>comprehensively bad, >>>>>>or what. >>>>>> >>>>>>Also, I've carefully designed things so that any time the motor is >>>>>>generating the power goes into a resistor and not into raising the >>>>>>motor supply rail (and thus backfeeding the supply). But I did >>>>>>notice that doing so kills one of these Emerson supplies (the TDK >>>>>>supply mostly takes it in stride, or if you're really egregious >>>>>>about things it turns off until you cycle power). >>>>>> >>>>>>Do you know of anything else that would kill one of these supplies? >>>>>>While I've eliminated the backfeeding problem, the board still has a >>>>>>current draw that can vary from a few tens of milliamps to ten amps >>>>>>over the space of less than a second -- if it would make the supply >>>>>>happier I can change this so that whenever the motor is turning the >>>>>>board is always drawing some minimum power. Efficiency will suffer >>>>>>-- but we're not after efficiency, we're after performance in a >>>>>>small space. >>>>>> >>>>>>Also, if anyone knows of a supply that's the same size or not much >>>>>>bigger, but comes from a manufacturer that's known to make >>>>>>bulletproof stuff, I'd appreciate it. >>>>> >>>>> The Emerson has OVP, namely a crowbar. Maybe you're glitching that, >>>>> or it trips from a big downward load step. Maybe it's a suicide load >>>>> protector. >>>> >>>>I did have a bug in the software that was allowing the motor to >>>>back-feed into the power supply rail without disconnecting as it >>>>should. >>>> So it could have been that. >>>> >>>>I've got more supplies on the way, I may do some testing with >>>>resistors and a switch to see if it can stand simply switching a load >>>>on and off. One would _hope_ that would be the case. >>> >>> Don't count on it! >>> >>> If you are decelerating a motor, where does the energy go? Mechanical >>> systems can store a bunch of joules. >> >>If the system is working right, it all goes straight into a resistor. >>As soon as the motor goes into regeneration the motor rail gets >>disconnected from the power supply (via a FET) and is allowed to float >>up. Then as soon as it gets above a set voltage the resistor gets >>switched in. There's a healthy amount of capacitance at the motor rail >>and the whole shebang gets sampled at the motor PWM rate, so it makes a >>self- oscillating voltage regulator that holds the motor rail close >>enough to the set point for things to work smoothly. >> >>When the motor starts to draw power the motor rail drops: when it drops >>down to match the power supply voltage things are switched on again and >>it draws power from the supply. > > > That sounds a little tricky. You could just hang an active zener across > the power supply output to clamp at, say, 25 volts. That might keep the > ps from crowbarring, too. > > I'm sure Jim would be delighted to design an accurate, 10 amp active > zener circuit for you.
I'm sure I could design an accurate, 10 amp active voltage clamp circuit, too -- it just wouldn't all be on one piece of silicon. And with such a part -- whether it came from me or from Jim -- I'd still have the issue that if it didn't work then the power supply wouldn't be protected. It is, to quote, "tricky". So I may as well fix what I have, and make sure that I'm using a power supply that doesn't have any unexpected gotchas (which is what this thread is trying to find out about -- whether my power supply is going to cut me off at the knees). -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Wed, 10 Apr 2013 09:17:35 -0700, Mark wrote:


>> >> That sounds a little tricky. You could just hang an active zener >> >> across the power supply output to clamp at, say, 25 volts. That >> >> might keep the ps from crowbarring, too. >> >> > agreed, if a small SW error is fatal to the hardware, you are asking > for trouble..
Well, it was only small in physical size, spanning perhaps four or five words of flash. Once I noticed it, it was about as large and as glaring as two diodes in parallel, where the obvious circuit intent was two diodes in anti-parallel.
> you said efficiency is not an issue, why not a big old diode, Shottky > if you prefer, in series with the PS output, that is fail safe. and I > guess you need the zener also
I may do that. If the power supply is well behaved I don't see the need for the clamp, but I'm going to at least see what the series diode does to me. The power consumption isn't an issue, true -- but if I introduce a 10W hot-spot into the design it'll stick out of the overall thermal management landscape like a sore thumb. -- My liberal friends think I'm a conservative kook. My conservative friends think I'm a liberal kook. Why am I not happy that they have found common ground? Tim Wescott, Communications, Control, Circuits & Software http://www.wescottdesign.com
On Wed, 10 Apr 2013 08:37:19 -0700, Jim Thompson
<To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote:

>On Tue, 9 Apr 2013 21:59:16 -0700 (PDT), Bill Sloman ><bill.sloman@ieee.org> wrote: > >>On 10 Apr, 13:08, John Larkin >><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >>> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott <t...@seemywebsite.please> wrote: >[snip]. >>> >>> >When the motor starts to draw power the motor rail drops: when it drops >>> >down to match the power supply voltage things are switched on again and >>> >it draws power from the supply. >>> >>> That sounds a little tricky. You could just hang an active zener across the >>> power supply output to clamp at, say, 25 volts. That might keep the ps from >>> crowbarring, too. >>> >>> I'm sure Jim would be delighted to design an accurate, 10 amp active zener >>> circuit for you. > >More demented snarkiness. > >But rather trivial to design, even with off-the-shelf discrete's... >think a TL431 plus a power PNP.
Show us. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
On Wed, 10 Apr 2013 11:44:00 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

>On Tue, 09 Apr 2013 20:08:37 -0700, John Larkin wrote: > >> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott >> <tim@seemywebsite.please> wrote: >> >>>On Tue, 09 Apr 2013 16:51:46 -0700, John Larkin wrote: >>> >>>> On Tue, 09 Apr 2013 18:17:07 -0500, Tim Wescott <tim@seemywebsite.com> >>>> wrote: >>>> >>>>>On Tue, 09 Apr 2013 15:52:40 -0700, John Larkin wrote: >>>>> >>>>>> On Tue, 09 Apr 2013 17:37:22 -0500, Tim Wescott >>>>>> <tim@seemywebsite.com> wrote: >>>>>> >>>>>>>So, I'm working on a motor drive board for a customer. Due to a >>>>>>>desire for performance improvements within the existing space, we're >>>>>>>going from the traditionally-accepted brute-force power supply to a >>>>>>>switcher. >>>>>>> >>>>>>>I have this nice board and software set that's carefully designed to >>>>>>>treat the power supply with kid gloves -- and it works very well >>>>>>>with the power supply that we used for prototyping. >>>>>>> >>>>>>>But for space reasons they went out and found what appears to be the >>>>>>>smallest possible power supply with the apparent specifications >>>>>>>needed (24V and 10A): >>>>>>> >>>>>>>http://www.powerconversion.com/assets/lps200-m_ds_1226129797.pdf >>>>>>> >>>>>>>It's not that this power supply sucks, per se. It's just that >>>>>>>things that work just fine with the original supply (A TDK/Lambda >>>>>>>SWS300-24) make the Emerson supply either exceedingly unhappy or >>>>>>>downright dead. Worse, I'm not sure what's taking out the power >>>>>>>supplies. >>>>>>> >>>>>>>So -- >>>>>>> >>>>>>>Does anyone have any mileage with these Emerson supplies? After I >>>>>>>told the customer "why yes, that should do" I began to notice the >>>>>>>name "Emerson" on this group, and the view of their stuff seems to >>>>>>>be pretty dim. I'd like to know if you feel these are OK, or >>>>>>>comprehensively bad, >>>>>>>or what. >>>>>>> >>>>>>>Also, I've carefully designed things so that any time the motor is >>>>>>>generating the power goes into a resistor and not into raising the >>>>>>>motor supply rail (and thus backfeeding the supply). But I did >>>>>>>notice that doing so kills one of these Emerson supplies (the TDK >>>>>>>supply mostly takes it in stride, or if you're really egregious >>>>>>>about things it turns off until you cycle power). >>>>>>> >>>>>>>Do you know of anything else that would kill one of these supplies? >>>>>>>While I've eliminated the backfeeding problem, the board still has a >>>>>>>current draw that can vary from a few tens of milliamps to ten amps >>>>>>>over the space of less than a second -- if it would make the supply >>>>>>>happier I can change this so that whenever the motor is turning the >>>>>>>board is always drawing some minimum power. Efficiency will suffer >>>>>>>-- but we're not after efficiency, we're after performance in a >>>>>>>small space. >>>>>>> >>>>>>>Also, if anyone knows of a supply that's the same size or not much >>>>>>>bigger, but comes from a manufacturer that's known to make >>>>>>>bulletproof stuff, I'd appreciate it. >>>>>> >>>>>> The Emerson has OVP, namely a crowbar. Maybe you're glitching that, >>>>>> or it trips from a big downward load step. Maybe it's a suicide load >>>>>> protector. >>>>> >>>>>I did have a bug in the software that was allowing the motor to >>>>>back-feed into the power supply rail without disconnecting as it >>>>>should. >>>>> So it could have been that. >>>>> >>>>>I've got more supplies on the way, I may do some testing with >>>>>resistors and a switch to see if it can stand simply switching a load >>>>>on and off. One would _hope_ that would be the case. >>>> >>>> Don't count on it! >>>> >>>> If you are decelerating a motor, where does the energy go? Mechanical >>>> systems can store a bunch of joules. >>> >>>If the system is working right, it all goes straight into a resistor. >>>As soon as the motor goes into regeneration the motor rail gets >>>disconnected from the power supply (via a FET) and is allowed to float >>>up. Then as soon as it gets above a set voltage the resistor gets >>>switched in. There's a healthy amount of capacitance at the motor rail >>>and the whole shebang gets sampled at the motor PWM rate, so it makes a >>>self- oscillating voltage regulator that holds the motor rail close >>>enough to the set point for things to work smoothly. >>> >>>When the motor starts to draw power the motor rail drops: when it drops >>>down to match the power supply voltage things are switched on again and >>>it draws power from the supply. >> >> >> That sounds a little tricky. You could just hang an active zener across >> the power supply output to clamp at, say, 25 volts. That might keep the >> ps from crowbarring, too. >> >> I'm sure Jim would be delighted to design an accurate, 10 amp active >> zener circuit for you. > >I'm sure I could design an accurate, 10 amp active voltage clamp circuit, >too -- it just wouldn't all be on one piece of silicon. > >And with such a part -- whether it came from me or from Jim -- I'd still >have the issue that if it didn't work then the power supply wouldn't be >protected. It is, to quote, "tricky".
Well, design a circuit that always works! So I may as well fix what I have,
>and make sure that I'm using a power supply that doesn't have any >unexpected gotchas (which is what this thread is trying to find out about >-- whether my power supply is going to cut me off at the knees).
How are you disconnecting the PS from the h-bridge rail? That needs a bidirectional switch, not just one mosfet, I think. -- John Larkin Highland Technology, Inc jlarkin at highlandtechnology dot com http://www.highlandtechnology.com Precision electronic instrumentation Picosecond-resolution Digital Delay and Pulse generators Custom laser drivers and controllers Photonics and fiberoptic TTL data links VME thermocouple, LVDT, synchro acquisition and simulation
mroberds@att.net wrote:

> Tim Wescott <tim@seemywebsite.com> wrote: > >>Due to a desire for performance improvements within the existing >>space, we're going from the traditionally-accepted brute-force power >>supply to a switcher. > > > A few years back, I was doing software for a device that had some small > (50 W or so) motors with integrated controllers; one end of the motor > had a shaft and the other end had connections for 24 V DC and a serial > port. These motors would try to regenerate into the power supply when > slowing. > > Version 0 of the assembly, for bench testing only, had a 120 VAC to > 24 VDC switching power supply, which I think was a Triad AWSP series, > a foot or two of wire, and the motors. The motors "liked" this power > supply; I could command them from 0 to full speed to 0 again as fast as > I liked without any trouble. > > Version 1 of the assembly had a 120 VAC to 30-60 VDC adjustable > rackmount supply by Sorensen, a long wire, a DC-DC converter brick to > make 24 V DC, a foot or two of wire, and the motors. I don't remember > the brand of the brick; it was about 0.5" x 2" x 3", and rated about > 150 W or so. (Because of where the long wire had to live, there were > safety concerns with bringing line voltage AC directly to the device.) > At first, the motors were just connected directly to the output of the > brick, but that didn't work very well; starting the motors worked, but > slowing or stopping them would cause the DC-DC converter brick to shut > down. Cycling the input power to the DC-DC brick would bring it back. > > The short-term fix, so I could keep working on the software, was to put > a few 1000 uF or so capacitors on the 24 V DC rail. I know for sure > there was one directly on the output pins of the brick and I think > there was one at each motor as well. These seemed to soak up enough of > the regeneration energy that the DC-DC brick *usually* didn't shut down. > I don't know what the final production fix was. > > >>http://www.powerconversion.com/assets/lps200-m_ds_1226129797.pdf >>[...] >>Does anyone have any mileage with these Emerson supplies? > > > I have no experience with them. > > >>While I've eliminated the backfeeding problem, the board still has a >>current draw that can vary from a few tens of milliamps to ten amps >>over the space of less than a second -- if it would make the supply >>happier I can change this so that whenever the motor is turning the >>board is always drawing some minimum power. > > > The Emerson data sheet says "minimum load 0 A" but data sheets have been > known to lie before. What happens if you just slap a plain old power > resistor across the output of the supply, such that it always draws 5 > or 10 W or so at 24 V DC? This is more to find out if the supply needs > a minimum load than a production fix. On the other hand, maybe you can > provide the minimum load with a lamp and sell it as a high-visibility > power indicator. :) > > The data sheet also says it has a 12 V DC, 0.5 A fan power output. > Maybe loading that output helps the regulation or behavior? > > This also appears to be a "medical" power supply. I *think* this mostly > has to do with isolation voltages (higher), leakage currents (lower), > and more numbers and squiggles on the rating plate. These probably > don't have a direct effect on your problem, but if there is a non- > medical version of the same supply, it might be worth a try. > > Matt Roberds >
2 things, regenerative technology and a DBr circuit. Of course if you don't have a full bridge and regen circuit I guess you would have to rely on a DBr circuit to switch in a burden R on the DC buss when it over does it. A basic active clamp with R in series with it works well. Jamie
On Tue, 09 Apr 2013 17:37:22 -0500, Tim Wescott <tim@seemywebsite.com>
wrote:

>So, I'm working on a motor drive board for a customer. Due to a desire=20 >for performance improvements within the existing space, we're going from=
=20
>the traditionally-accepted brute-force power supply to a switcher. > >I have this nice board and software set that's carefully designed to=20 >treat the power supply with kid gloves -- and it works very well with =
the=20
>power supply that we used for prototyping. > >But for space reasons they went out and found what appears to be the=20 >smallest possible power supply with the apparent specifications needed=20 >(24V and 10A): > >http://www.powerconversion.com/assets/lps200-m_ds_1226129797.pdf > >It's not that this power supply sucks, per se. It's just that things=20 >that work just fine with the original supply (A TDK/Lambda SWS300-24)=20 >make the Emerson supply either exceedingly unhappy or downright dead. =20 >Worse, I'm not sure what's taking out the power supplies. > >So -- > >Does anyone have any mileage with these Emerson supplies? After I told=20 >the customer "why yes, that should do" I began to notice the name=20 >"Emerson" on this group, and the view of their stuff seems to be pretty=20 >dim. I'd like to know if you feel these are OK, or comprehensively bad,=
=20
>or what. > >Also, I've carefully designed things so that any time the motor is=20 >generating the power goes into a resistor and not into raising the motor=
=20
>supply rail (and thus backfeeding the supply). But I did notice that=20 >doing so kills one of these Emerson supplies (the TDK supply mostly =
takes=20
>it in stride, or if you're really egregious about things it turns off=20 >until you cycle power). > >Do you know of anything else that would kill one of these supplies? =20 >While I've eliminated the backfeeding problem, the board still has a=20 >current draw that can vary from a few tens of milliamps to ten amps over=
=20
>the space of less than a second -- if it would make the supply happier I=
=20
>can change this so that whenever the motor is turning the board is =
always=20
>drawing some minimum power. Efficiency will suffer -- but we're not=20 >after efficiency, we're after performance in a small space. > >Also, if anyone knows of a supply that's the same size or not much=20 >bigger, but comes from a manufacturer that's known to make bulletproof=20 >stuff, I'd appreciate it.
I have seen problems before when a load has a serious content at the switcher frequency, or one of them is a near harmonic of the other. Both tend to misbehave. The available fixes are a different switcher, a different motor controller frequency, or a heavy LC trap. YMMV ?-)
On Wed, 10 Apr 2013 10:11:36 -0700, John Larkin
<jlarkin@highlandtechnology.com> wrote:

>On Wed, 10 Apr 2013 08:37:19 -0700, Jim Thompson ><To-Email-Use-The-Envelope-Icon@On-My-Web-Site.com> wrote: > >>On Tue, 9 Apr 2013 21:59:16 -0700 (PDT), Bill Sloman >><bill.sloman@ieee.org> wrote: >> >>>On 10 Apr, 13:08, John Larkin >>><jjlar...@highNOTlandTHIStechnologyPART.com> wrote: >>>> On Tue, 09 Apr 2013 21:43:44 -0500, Tim Wescott =
<t...@seemywebsite.please> wrote:
>>[snip]. >>>> >>>> >When the motor starts to draw power the motor rail drops: when it =
drops
>>>> >down to match the power supply voltage things are switched on again=
and
>>>> >it draws power from the supply. >>>> >>>> That sounds a little tricky. You could just hang an active zener =
across the
>>>> power supply output to clamp at, say, 25 volts. That might keep the =
ps from
>>>> crowbarring, too. >>>> >>>> I'm sure Jim would be delighted to design an accurate, 10 amp active=
zener
>>>> circuit for you. >> >>More demented snarkiness. >> >>But rather trivial to design, even with off-the-shelf discrete's... >>think a TL431 plus a power PNP. > >Show us.
Crikey Larkin, even i can see how to do that. Just how dumb are you? ?-)