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QuietProjects

Help With Off the Shelf Psu Design

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Hello everyone

I have been working on a slim xbox build and have it 95% working the way it should with some off the shelf parts that are not the pico psu. The only sticky issue that is pretty minor is the switched power requirements. I don't really understand electronics that well past what I call a "blackbox" understanding. You know, I understand that the boards I use say they will take a certain voltage in and output whatever but no knowledge to build a more complex circuit for switching the reset line for the smc.

I am using a meanwell psu that is rated for 5v20A that you can find in a lot of places on the internet. Then I am using two boards from Pololu.
One to step up the voltage to 12v:Please login or register to see this link. and another to knock the 5v down to 3.3v Please login or register to see this link.

I was wondering if you all could help me with a schematic or some understanding of how to switch on and off the 3.3v signals to help reset the smc. I have some idea that you could use some transistors maybe to accomplish this but I am not super sure. The goal here would be to use the above boards in custom pcb for future slim xbox builds.

Sorry if this isn't super clear


Here is the picture of my install and somewhat self evident why it could be better looking

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Edited by QuietProjects

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There's a small problem here.  You need a separate 3.3 Vdc power supply that is always on to provide the standby power source for the SMC/clock circuitry for v1.0-1.4 consoles.  And, for a 1.6/1.6b, you need an always on 5 Vdc source. Very little current is needed - I believe something like 50 to 75 milliAmps.

It is this standby power supply that provides the voltage and current necessary to power on/off the console via the soft switch mechanism controlled by the SMC (v1.0-1.4) or Xyclops chip (v1.6), power the clock circuitry to keep the time and date current when the rest of the console is OFF and charge the clock cap.

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Thank you for the reply Kaos, I appreciate your seemingly unending commitment to answering questions, here and on reddit. I was debating which place to put this question originally.

20 hours ago, KaosEngineer said:

You need a separate 3.3 Vdc power supply that is always on to provide the standby power source for the SMC/clock circuitry for v1.0-1.4 consoles.

Just so I understand, do you mean in addition to the one that I am using currently and that the output of which can't easily be switched?

20 hours ago, KaosEngineer said:

And, for a 1.6/1.6b, you need an always on 5 Vdc source. Very little current is needed - I believe something like 50 to 75 milliAmps.

A similar question here. I have 5vdc coming from the psu itself. I should take pictures of the way it is installed on the underside as I only have one of the 5v pins connected as the rest seem to be internally connected on the motherboard itself.

I should also mention that the little board I posted does work already. Everything boots fine, I just get some funny behavior once in a while like the console wont boot again after a soft shutdown unless the power is completely disconnected and reconnected. I assume this is mimicking the resetting behavior, I dunno I am probably wrong. This is installed on a 1.6.

I did read your post about the way the xbox boots in the other thread on here and I am not sure I totally understand the exact sequence of events that the xbox goes through to boot

 

Edited by QuietProjects

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9 minutes ago, QuietProjects said:

I just get some funny behavior once in a while like the console wont boot again after a soft shutdown unless the power is completely disconnected and reconnected. I assume this is mimicking the resetting behavior, I dunno I am probably wrong. This is installed on a 1.6.

I think you need switch the 12 volt supply off at shut down and back on using the power on pin in the power connector.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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1 hour ago, SS_Dave said:

I think you need switch the 12 volt supply off at shut down and back on using the power on pin in the power connector.

Okay, now this is where my ignorance of electronics comes in, Is it enough to temporarily ground out the 12v? Like if i where to connect some kind of transistor or maybe a reversed diode with a higher rating than 12v maybe?

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6 minutes ago, QuietProjects said:

Okay, now this is where my ignorance of electronics comes in, Is it enough to temporarily ground out the 12v? Like if i where to connect some kind of transistor or maybe a reversed diode with a higher rating than 12v maybe?

No it will probably damage the power supply

The 12 volt needs to be disconnected from the Xbox when it's in the standby state.

The 12 volt supply as far as I can work out is for the Fan and Hard Drive but I know a 1.6 will fail to boot if the 12 volt is not there, It's part of the protection of the CPU/GPU.

The reason for the 4 pins in the power plug is to handle the current drawn by the Xbox's 5 volt needs.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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Okay. I went poking around and found this article on hackaday: Please login or register to see this link.

I watched the video and the dude mentioned this ic in addition to the schematics:Please login or register to see this link.

Would this work?

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I would suggest a small circuit like this.

 

pnp-switch-motor_3.png.27f8027f0a541133d110957cb2ff640d.png

And the Xbox power supply has a similar switching for the 12 volt supply

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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Oh that is way more simple thank you. And what about the PowOk and PowOn stuff. I read Kaos's post about it and didn't totally understand. I know that as I have been putting this together you only seem to need one signal PowOn I think and the console will still boot. Would providing constant 3.3vdc to both cause goofy boot behavior? Could you also use a similar circuit but on the PowOn and connected to PowOk?

 

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The power ok is a 3.3 volt from the power supply to tell the Xbox the power supply is working and in my testing the Xbox will work without that signal.

The power on is from the Xbox to tell the power supply to fully operate or to enter standby mode.

The other thing on a version there is also a switched 5 volt supply that may need to be controlled as well.

 

A simple way would be a 250 watt Pico power supply and invert the power on signal and rewire the power outputs to suit the Xbox.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

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I did think about using a pico psu and even bought one and the stuff to do the conversion. I just seemed like there wasn't a ton of information about which caps to remove or how many.

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8 hours ago, QuietProjects said:

Just so I understand, do you mean in addition to the one that I am using currently and that the output of which can't easily be switched?

Yes, since the standby power supply has to always be on.  You don't want to run the 5Vdc 20Amp supply all the time just to provide the 3.3Vdc standby supply with the 3V, 6.5A Step-Down Voltage Regulator D36V50F3.

This addtional 3.3Vdc standby supply only needs to provide 50-75 milliamps of current.

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8 hours ago, QuietProjects said:

A similar question here. I have 5vdc coming from the psu itself. I should take pictures of the way it is installed on the underside as I only have one of the 5v pins connected as the rest seem to be internally connected on the motherboard itself.

I should also mention that the little board I posted does work already. Everything boots fine, I just get some funny behavior once in a while like the console wont boot again after a soft shutdown unless the power is completely disconnected and reconnected. I assume this is mimicking the resetting behavior, I dunno I am probably wrong. This is installed on a 1.6.

I did read your post about the way the xbox boots in the other thread on here and I am not sure I totally understand the exact sequence of events that the xbox goes through to boot

V1.6 Xbox's use 5Vdc instead of 3.3Vdc as the standby supply that is used to keep the clock circuitry and Xyclops SMC powered to enable soft-switching on / off the rest of the power supply.

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Okay so what I am understanding from the advice you both are giving me is that I need to add an additional 3.3v source for the standby and an additional bit of circuitry to switch the 12v right?

 

Also for more clarity here is a video of the booting behavior

 

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Try powering the HDD from the 5 volt on the DVD connector or from here.

406271639_20200820_221517.thumb.jpg.4cd974e75222afa8c347d8a351acd998(1).jpg.f44f46d0858c7618d969075f6fa23178.jpg

And you should always have a 5-10 second time between switching the power supply off and on 

36 minutes ago, QuietProjects said:

Okay so what I am understanding from the advice you both are giving me is that I need to add an additional 3.3v source for the standby and an additional bit of circuitry to switch the 12v right?

The 1.6 version does not need a 3.3 volt to operate, The 3.3 volt is from the motherboard to the OE power supply.

And yes you should be switching the 12 volt to the mainboard.

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

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Alright, so in your opinion the booting looks normal and I'm just getting uppity with the power cycling?

thanks for the tip on the ssd. I didn't even think to look for alternate sources to power it and the current connection is a bit fiddly and dumb.

Okay I will try to get something slapped together in kicad

Edited by QuietProjects

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Yes and try the SSD powered from the point in the pic I posted as it will need to reset at each Xbox power cycle.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

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I tried my hand at designing a PCB, naturally it did not work heh. I think my traces are too small for the 5v to pass enough current. I found a soft switch to use for the 12v but I wont use it in the redesign. Any feedback is appreciated

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Edited by QuietProjects

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The traces for the 5 volt are defantly to small.

I also noticed it looks like you have the "pow ok"( Blue wire)and the "pow on" (White wire)linked you should not have the "pow ok" connected .

The pow on signal is a low current supply properly around 2 -5 ma Max so don't use it to control a relay or the 2 switching transistors directly.

The 12 volt supply (Yellow wire) needs to be switched and a 500ma is fine as long as you're using a 2.5 inch HDD.

The is also a 5 volt supply (Red wire) that is shown on the original power supply as a switched supply.

If you were to use  2 switching cricuts along the lines of one I posted before (1 for the 12 volt and 1 for the 5 volt) you would be getting close.

 

psu16delta.gif.5f25e1567eac4e3c1d7b01a5d65839f6.gif.399fcae3b6605a2b8b3659daae55cd3a.gif

 

 


Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

 

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Okay. I think I need to find a suitable MOSFET. Im not sure though. I was doing some reading and it seems that BJTs only pass current while being controlled by current at the base? They dont seem suitable. And mosfets pass voltage and current while using voltage to trigger the pass through? Is this correct?

I did do a redesign (before your post) with the back of the pcb being a power plane and it did work. But my 12v reg failed and dumped 5v and a lot of current where it wasn't supposed to go and now the board wont turn on. I do have another 1.6 around so I will get the xenium moved over.

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Okay sorry for the double post. I am realizing how silly that last question was. I guess the better question is, given the stated amperage's on the dev wiki, would a regular transistor be able to pass enough current for each of the voltages without blowing up or should I use a different component? 

I have another question. How would the switching even work exactly? Because the psu when switched on is always providing 5vdc and wouldn't that always turn on the transistor/mosfet? Or am I not correctly understanding how this all works?

Edited by QuietProjects

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If it was a simple thing to design  multi voltage and multi switched power supply it would have been done years ago. I would look at the 300w to 400w Pico power supplies for a PC and mod one of them for Xbox use.

 

The 12 volt supply on a version 1.6 is to power the fan and hard drive. The Xbox will not boot without the 12 volt present as it's a safety thing (No fan).

The current required to run a fan would be less than 500ma (a stock fan is 210ma) so you could get away with a BC337 that has a collector current of 800ma  but as you have 2 fans on you testing board they may be drawing more current. so maybe a BD137 or a TIP31

I am not sure of the switched 5 volt for the motherboard current requirement it's something you would need to test and then you also need to workout the SSD 5 volt current requirements and as a guess you would need a peak of 1500ma so for that I would look at a TIP31 as that has a collector of 3000ma but would need a heatsink for it as well.

You should also have some current limit to the base of each transistor (That's what the PowOn is for) as well as some back feed protection for both switching transistors.

 

Cheers

SS Dave


Soft modding is like masturbating, It gets the job done but it's nothing like the real thing.

 

 

 

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