DPS-600 fast regulated smps for Wire-Amp

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I had some time at lunch today ... and drew this up quickly. So I need 2 inverters not the one I thought I needed last night. This allows the resistors to be selected for each bias level. Does not show decoupling caps to smooth switching transition on resistors or on logic lines. Low EMI optically coupled NC relays for switching bias resistors.


The attached obviously doesn't include the remote control section that you showed in your drawing Roberto, I have drawn that up at home already, and included opto isol NC relay (so I did not need the inverter on input of the relay). The part I am thinking of using there has 60V contact blocking voltage and 1500V input - output isolation. I am a bit concerned about the 60V rating, is that sufficient?
 

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Hi,
DPS-600->EN_Pin is float. independant of this, a simple small signal diode can offer a good isolation.
sure, you can do in this way for switch bias.
sorry if i modify your scheme, RC need for correct delay, you can play with low voltage smd caps eg. 1uF to 2,2uF.
becouse pin switch low after 250ms, it's not good for bias set.
Consider balanced time of caps filter and amplifier. a good value delay,i think 1,5-3 sec.
for remote control, it play in low current/voltage range, as i said before. obvius need high voltage ISO.

regards
 

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Thanks Roberto!

Sorry about asking the same question twice, was in a hurry and didn't think it through.


I had misunderstood the EN_Pin in the DPS600 datasheet, I had thought it switched low when voltages on output are stable. But with its operation at 250msec after power on, then like you have said, we can just add an additional delay with RC, so it is not a problem.

I'm not planning on using many through hole parts for this anyway. A few SOIC logic chips and a reg or power it all with battery since it will not require much current at all in standby, I am targeting less than 5mA for all the logic circuits. Probably MUCH less than this in standby. Xbee temp sensing and remote adds 50mA during transmit but that can be scheduled or left out entirely if not needed.

I have a few other jobs to do for the next few days. (I have a new DAC/headphone amp to finish assembling) I'll be back on the weekend with a more complete schema and in about a weeks time my first pcb layout hopefully ready for comments/suggestions.

I am trying to keep the design such that it should be easily applied for all DPS600 + LME49830 Wire users. As described in earlier drawing, I am targeting a 2 pcb solution: 1 mounted to front panel; other small pcb directly at the bias set trimmer position.


qusp and I have discussed what our needs/wants are offline and we are currently planning for:

- 1 x power momentary switch (latched and debounced)
- 1 x relay in parallel with power switch to allow remote on/off via xbee or a 12V trigger from other component (will need ~5V zener diode to drop voltage as logic chip I have in mind takes max 7V on input.)
- 1 x mute momentary switch (latched and debounced) - set bias low when output muted
- 1 x power down sequence to hold power on till after LME mute pin set; then power off so no power down transients.
- 3 x bias levels based on summer/winter setting and staged startup
- 4 or so temperature sensors from various heatsinks to xbee ADC pins
- 1 x case ambient temp sensor too


Cheers,
Chris
 
First of all...Ops! in your case not need delay becouse start ever with low bias. delay need if you use simple circuit for switch bias (auto after startup) in this case a simple bjt or mosfet or 555 (with delay 2 sec.) can drive a mini relay for bias. eg. start with 80mA and go to 400mA after 2 sec.

see startup timing, En_Pin switch to low and remaining low up to switch off smps.

This En_Pin is used in DPS-600/DA for enable driver in D Class.

I think is good if you and qusp shared complete your project.
maybe others see some solution.

Regards
 

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First of all...Ops! in your case not need delay becouse start ever with low bias. delay need if you use simple circuit for switch bias (auto after startup) in this case a simple bjt or mosfet or 555 (with delay 2 sec.) can drive a mini relay for bias. eg. start with 80mA and go to 400mA after 2 sec.

see startup timing, En_Pin switch to low and remaining low up to switch off smps.

This En_Pin is used in DPS-600/DA for enable driver in D Class.

I think is good if you and qusp shared complete your project.
maybe others see some solution.

Regards

Thanks again for the info and ideas Roberto, very helpful indeed. Having your involvement gives me more confidence that this control board for DPS600+lme49830 Wire will give optimal integration of what is IMO potentially amongst the best PSU and amp combo getting around in DIY.

We'll share the project when something more is worked out and worth sharing. Probably in a weeks time or so. For now a rough list of the targeted features for the control is in the list above, if anyone thinks that there is a glaring omission from the list then let me know!


Chris
 
qusp and I have discussed what our needs/wants are offline and we are currently planning for:

- 1 x power momentary switch (latched and debounced)
- 1 x relay in parallel with power switch to allow remote on/off via xbee or a 12V trigger from other component (will need ~5V zener diode to drop voltage as logic chip I have in mind takes max 7V on input.)
- 1 x mute momentary switch (latched and debounced) - set bias low when output muted
- 1 x power down sequence to hold power on till after LME mute pin set; then power off so no power down transients.
- 3 x bias levels based on summer/winter setting and staged startup
- 4 or so temperature sensors from various heatsinks to xbee ADC pins
- 1 x case ambient temp sensor too

Daydreaming at lunchtime again and I have just realised, we need to have feedback from bias setting relays such that the DPS600 remote on can only be triggered on when bias is at minimum. I have idea on using some of the spare logic gates in the hex-schmitt trigger inverter and hex and gate chips. No more chips needed to implement this logic.

This will mean that on power off, while RC discharge is happening, we must wait at least the period of high-bias power on delay period (1.5 - 3sec) before we're able to power amp on again.
 
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Good question, I've changed path a touch for a few reasons:


- very limited number of IO on xbee so trying to keep them for other stuff, later, rather than add an extra microcontroller (pic/arduino etc).
- comms may fail
- operating system/master controller device may fail (sd cards fail/config changes during updates ... )
- need to/want to use the amp later for something else entirely


The design goal I've added for myself is to have the remote control basically act the same as when someone presses front panel momentary switch. Then after that the remote acts as a monitoring tool primarily. It adds very little size to the board and only 3 or 4 dollars in parts (and uses spare inverter buffers from the chip that I am using for latch for momentary switches anyway so its only a few extra pcb traces in some cases to go from one set of controls to the next). This also means that the current demand of the controller circuit in 'standby' is microamps only.

Without the RC for bias delay we would have to have 2 inputs and 3 outputs (from the xbee) rather than just 1 pin for triggering the whole sequence, this starts cutting into the number of temp monitors we can have available because of the ADC pins being used in DI or DO mode. We would also still need almost the same number of resistors because the detection of OC state needs a pull up resistor before the input to the DI on a microcontroller. So the parts count has increased by a few caps and 1 x 30c SOIC14 hex AND chip. Hardware wise this addition is not a big impost and adds a fail-safe mode that is (hopefully) bulletproof.

EDIT: I'll try to have a draft schematic ready covering all of it before I visit tomorrow and we can have a chat about it while I'm there if you've got time?
 
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Hi,
Some simplifications:
analyze the logic states, assuming a cold start.
1-bias have preset to low;
2-Remote control switch to open (ON smps) (software reset bias condition to low).
this mean That Is not necessary hardware feedback with bias.
also, is good that smps switch off while the bias is high.
(this load, help to clean shunt down).
an idea may be (depending if you use the amp for a party).
Bias automatically switch to a low value, if the volume remains high more than 20 sec. (this should be a time of peaks).
however, I'm well available.:)

my curiosity .. what happened to Owen? I can not hear from him for a long time, even by email.

Well, i wait your scheme.

P.S. for circuit bias control, is better a solution with small pcb on amp.
signal on pins of trimmer is not DC current set, but critical ac in driver circuit of amp. is better not use long wired.

Regards
 
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Hi Roberto,

Later we will add temperature sensors to each heatsink as well as ambient case temp, and allow remote control to have logic to adjust bias/shutdown based on these values :) In our part of Australia, despite our terrific weather, we do get some VERY hot summer days, want to protect against high ambient temps taking amplifier out of design temperature range.

Interesting that high bias is better for turn off for smps, will not worry about altering that prior to switch off. Will keep this in mind.

The bias control circuit was always intended to be close to amp :)




I have attached my thoughts on what a preliminary schematic and layout for switched bias pcb might look like. Opto-isolated relays are to be NC.

The bias pot has 2.54mm pitch between leads and a 2.54mm pitch pin header can easily slot into this position and allow 'auto-bias' pcb to be swapped in on a socket or soldered in place with almost no difference in proximity to pcb. With opto-isolated relays with minimal/no EMI I think this is a drop in solution with almost no compromises on performance of Owen's circuit design. (that is provided we get the R and C layout correct to eliminate transient issues during switching)

What I am not certain about is where best to place caps for smoothing any transient when switching bias resistors.


Cheers,
Chris
 

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Hi,
I saw good your drawings are correct. for the solid side of the relay, can not produce that "tick" or other noise when it changes state, because the circuit is already under bias current.
regarding the side of logic gates, it is best to test the outcome.

Honestly, I am opposed to the classic capacitor that is present in almost all of the amp's, right in the bias circuit (connected between high side and low side),especially if large capacity.
 
Hi,
I saw good your drawings are correct. for the solid side of the relay, can not produce that "tick" or other noise when it changes state, because the circuit is already under bias current.
regarding the side of logic gates, it is best to test the outcome.

Honestly, I am opposed to the classic capacitor that is present in almost all of the amp's, right in the bias circuit (connected between high side and low side),especially if large capacity.


Thanks again!

I have sorted out the remainder of the logic side design and qusp and I have talked it through over the weekend. I will try to build a prototype on a breadboard in the next week or two and test it with an 8ch logic analyser to ensure that all of the different scenarios check out and timing is correct. After that we'll get a prototype pcbs made.

Once I know it works at least from timing and logic perspective I will put a write up in here about that part.

Regarding the capacitor in parallel, Owen's build recommend to not populate that position on the pcb. On the bias adjust side, I was only worried about using something to stop transients in the switching period. I might just leave positions for it on the pcb and can populate them if they are required based on testing.

Cheers,
Chris
 
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Noooo!!!

Not having much luck at the moment.

My second dps-600 has stopped working. Had the amp running for over an hour this morning. Set everything up again this evening to investgate the start-up noise.

I had been using 22Ohm resistors in series with the +/- 45V rails, but omitted them this time. Bias was set to 400mA. DMM connected to monitor.

1st, checked all wiring to make sure it was ok. Disconnected the O2 and turned on the dps-600. Everything ok, no start-up noise & slight LF oscillation noise on shut-down. DMM showed 400mA bias.

2nd, reconnected the O2 and turned on the dps-600. Same start up noise as this morning but after roughly 6 seconds the dps unit shut down with both green LEDs blinking on & off...

Turned everything off and disconnected everything, turned the dps on & both LEDs blink & unit fails to start... What have I managed to break this time?
 
How help you without photo or scheme of your connections? seem you have noise loop, is not simple i understand a reason. i know dps-600 have very low emission in all, no problem even with dsp very near. well.. switch on dps-600 without load, and see well led on small module. blink immediate from start? or running for one sec. and after blink?
 
ah .. well! This is a special extra protection in the event fails the power regulator, just not to damage the amp, or other devices associated with the DPS-600.
I honestly do not understand how it can happen.
If you are able to replace the one mosfet smps, I can send, or you buy it, and I will refund.
looks like you have some damaging loop. in this case it is preferable that lowers the bias current, just to investigate the noise.
have replaced the res-fuse on the first smps?
 
Maybe he can clarify some things.
Since every smps, has a sheet of the final test, these are some features that I recorded before shipping.
230Vac: resistive load (one per side, to gnd) 2x375mA at DC-output.
at switch-on (main switch), startup duration is very short (500ms duration), so it seems immediate, the green LED.
Since I know very well this smps, the load ran for 30min. in the end, I read a delta temperature of 20 ° (without add heatsink).
Now, I do not understand, the noise during the startup sequence, given that very little time. I'm missing something? perhaps LME voltage has a superior absorption? or have big capacitors on LME? this can slow down the startup sequence). other than that it does not make sense to put a large capacity, on the output of the regulator.
expect a few more turns on this smps with wire-amp,... I hope better than "BuildMeSomething" :D
Note: this project started for military use (i have some photos,mybe can send in private), then,if all mosfet blow, fault remaining only on mosfet. (the fault does not affect other parts).
Special protection include the monitoring of output dc voltage.
RFI test, produces the best low radiation possible in smps,consider it is without iron frame.

Of course anything can happen, even a wrong component from production. I do not want to say that this smps is the best in the world but it certainly is not a smps for lamps as others.
 
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AP2, the start up noise has nothing to do with 'the wire', or the DPS600, it is to do with 2 things

1. the amp he is using for preamp for testing is a battery powered headphone amp called the O2; it uses a virtual ground, as BMS is using the single ended input version of 'the wire' if he turns on the poweramp first before the O2 is on and stable, the input is effectively floating, so free to pick up any noise until the ground reference is stablised after turn on.
2. he is turning the poweramp on first in the sequence, not 'preamp/source first as is normal procedure.
 
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