HP HSTNS-PL11 psu Over Voltage Protection voltage increase?

[innkeeper]

I am trying to figure out how to increase the Over Voltage Protection voltage on this supply as I want to modify it for running at 13.8V with quickly varying loads (transmit/recieve) for ham radio operation and I do not want to trigger the OVP.

I have the schematic and a pic of the mainboard, both are attached.

Others have modified this for higher voltage, and that seems pretty straight forward from the schematic. However, they can't reach 13.8V for actual use under quickly varying loads without the OVP kicking in,  They end up dropping the voltage down some to like 13v to keep it from happening.  it would seem there is a little overshoot when the load drops quickly. This would seem to be resolvable if the OVP voltage could be raised a little.

I've been studied the schematic for the way the supply does OVP is not apparent to me.  Anyone have an idea of how it works?

[eblc1388]

I have looked through the schematic and I may have good news for you.

Apparently the power supply is using a microcontroller to monitor the +12V voltage level via its ADC input to provide the OVP function. In the attached photo, the +12V is divided down to below 3.3V and fed into the uP2 pin15. Thus reducing R901 would do the trick. You can do this by parallelling another high value resistor across R901 via trial and error.

A better method is to measure the pin15 voltage along with the actual +12V output voltage and work out the divider ratio. Then it is a simple matter to increase the OVP to say 14.5V or 15V by changing the divisor ratio.

Initially I couldn't find the MC9S08QG8 on the circuit board but then I noted from a chinese website that it is listed together with MQ64CDTE so they are equivalent. Hope all these helps in solving your problem. Do let us know of the result.

[innkeeper]

eblc1388,  Thanks, The Chinese version of the uP is a great find, I was assuming that was a uP but couldn't prove it out.

I also saw that voltage divider going into the uP after i posted.  That makes sense and I agree thats likely the place it gets detected, and glad that you think the same. I think that is the right track to go for. it also matches the flow diagram for what they call uP1

There are 2 uP's on the board, one MC9S08QG4 and one MC9S08QG8.  From the information you found, the MC9S08QG4 is the one we can see in the picture and the MC9S08QG8 is the one that the voltage divider of interest is connected to seems to be on another board in the PS that i do not have a picture of.  I belive i found the board and it looks like that board is hard to see without removing the PS completely from the chassis.  So that will be my next step.

I've also made some sense of the labeling on the schematic of things like MB1 SB1
SB2 etc. those indicate the board the components are on and the letters may mean the side of the board so SB1A is one side and SB1B is the other.

The MC9S08QG8 would then be on board and side SB2A which judging form the number of components on the board would be that small board i don't have a picture of yet. unfortunately the boards are only labeled that way on the schematic and not the silk screen as best i can see. I did further conform the small board by finding the programming header jpm900 which is visible with a silk screen label on the that same small board.

This looks very promising, I'll post my progress.

[neuzpisk]

hi, i have same issue, but mine different MQG4CDTE

did you OVP voltage ?

[eblc1388]

The location of uP2 in my Reply#1 is wrong. The correct location is as follow. Noted that these power supplies have had many revisions and the actual position or MCU type might be different. Mine is PIC16F883 while others have reported PIC16F886. even getting the correct part numbers are difficult as most are blocked by other components.

Once you have found this MCU, then you can carry out the OVP mod as in my reply#1.

[neuzpisk]

i even can't see what is tipe MCU is

[ubrain]

Hi guys, new here and to be honest, not very expert in the field, so apologies in advance for not being likely to be able to offer much advice... although I've got lots of enthusiasm if anyone needs any of that!

I was wondering whether anyone did successfully manage to tweak the Over Voltage Protection of the HSTNS-PL11 in the end?

I've managed to get the output voltage up to about 14v by winding it up gently. However, it won't start up with a voltage of over 13.75, and with a load in place, 13.4v is about the limit.

I'd so love to push it up to about 14-14.4 but the OVP is getting in the way!

[mamujim]

Hi All,

Just purchased one of these and hoping to get the output voltage up to about 13.8v.

Can someone please show how to adjust this psu to get it outputting around 13.8v.

Many thanks

[ubrain]

Ha - well after thinking I'd be no help to anyone here... I can answer that 

Open the box up: usual caveats about not being plugged in, and still watching out for inconvenient discharge from big capacitors.
Add a 6.8K resistor between these 2 points. (don't copy me - I made a mess because I didn't have the right resistor handy)
Turn the VR fully to the right (cw) before you start up, it should give about 13.2v. Slowly wind it up (ccw) until the over voltage protection kicks in.
As I said above, I got it up to 14v but that was without a load so pretty useless. With a load on it, I'm getting it starting up OK at about 13.4v.

I'd still really like to know if anyone managed to solve the OVP issue though.

[mamujim]

Excellent, many thanks, will give it a go and see how i get on.

EDIT:thanks mate, got it working  added a VR set to 6.8k across the points you mentioned

[eblc1388]

I'd still really like to know if anyone managed to solve the OVP issue though.

Try this and report back.

[ubrain]

Wow!
It's a shame there's only one thanks button because I actually need to say it twice - in 2 different voices.

Firstly: "Thanks for that eblc1388! " That was the biggest PITA fiddly messed up soldering job I've done in my life! Not being experienced with componentry this small, nor having a decent workbench, I broke and repaired 2 other things during the course of the job. Actually I appear to have broken 3 things as the power LED doesn't come on now - but I'll live with that.

Secondly:  "Thanks for that eblc1388! " It works! The tweaked VR now takes the voltage up to a max 14.41v so no idea if or when OVP would now cut in. It's now purring away, pumping a nice consistent 80A at 14v into the batteries. 
Win!

It's worth noting, anyone else planning to try this: with the OVP out of the way, there's nothing to stop this box getting quite out of hand. At 14.4v it brazenly tried to chuck 150A at an empty battery and being LiFePO4, the battery was happy to take it. Fortunately the BMS was only willing to put up with that for a few seconds as I'm not sure how long a 1200w rated PSU would last pumping out over 2000w.

[paulzedx636]

 I have two HP HSTNS-PL11 and was wondering if anyone has done the voltage adjustment mod with the 6.8k resistor on the voltage adjust pot. And has someone also put the 12k resistor on the voltage regulators to override the OVP at the same time. Looking to find the max working output voltage before the OVP kicks in. 

[innkeeper]

Try this and report back.

thanks

[eblc1388]

There's a lot of attentions on the HSTNS-PL11 with its small size but hefty 100A 12V output. As I've just put together an electronic 'wattmeter' (see image) using an AliExpress bought module, I might as well measure how these supplies perform on standby and idle. The following are my findings.

The no load wattage shown are in the range of 42~44W for PL11, double checked with several PL11 power supplies. What it means is the power supply is consuming 44W with 12V but no load attached. This figure seems exceptionally high and unreasonable compares to different models of server power supply.

It would be helpful if anyone with a HSTNS-PL11 and wattmeter can either confirm or rebute the figure using other makes of wattmeter.

If it turns out to be correct, then it is definitely not a good choice if your application is mostly placing the supply on standby or very lightly loaded. However, its efficiency is still very good when loaded.

The C7000 supply shows the best result. Before you even consider to go out and buy a C7000 power supply, be warned that there is no trim POT inside the power supply for output voltage trimming and access to circuitry is severely blocked by large components. Unless you are contented with 12.2V output, there is'nt any mention of voltage increase modification or OVP mod anywhere on the whole internet.

Test Results: Server Power Supply Measurement
==============================
Measured with electronic wattmeter module
AC mains voltage = 243V

Test Conditions:
AC ON: Supply +12V output disabled
DC ON: Supply +12V output available, no Load
Loaded: Supply +12V output loaded

1. 2450W Blade C7000 Power supply
   ==============================
   AC On: 3.9W
   DC On: 14.6W
   Loaded: 12.2V 60.5A =738W
   Wattmeter: 790W, PF=1
   Efficiency: 738/790 = 93.4%
 
2. HSTNS-PL11 1200W supply
   =======================
   AC On: 8.12W
   DC On: 42.3W
   Loaded: 12.3V 60A =738W
   Wattmeter: 787W, PF=1
   Efficiency: 738/787 = 93.8%
   
3. DPS-650EB 665W
   ==============
   AC On: 9.7W
   DC On: 18.32W
   Loaded: 12.13V 59.3A =719W (overloaded, max 54A)
   Wattmeter: 823W, PF=1
   Efficiency: 719/823 = 87.4%

[ubrain]

An update on my report above.
This PSU seems highly resilient to abuse. It's not that I'm actively trying to blow it but I've really not been trying very hard not to blow it and despite some quite bad treatment, it's still going strong.

It was briefly pumping out 2000w (at about 12.8v) today slowly dropping to about 1300w over the course of 10mins as the battery took on charge. I've had it doing >1300w for over an hour with no sign of problems - yes the fan's running full pelt but nothing seems to be getting overly hot.

My current issue though, is that there's not a perfect voltage to set it at, to cover the full range of the charge cycle. Set too high, then at the start, when the batteries are empty, we're trying to pump out 170A (or more) however, a voltage that gives a civilised output at this end, leaves us with, in effect, a trickle charge as we approach the 'full' end of the cycle.

So there is a little bit of circuitry I'd like to build but I really don't know enough to design it myself as my knowledge is basic - for example: I know, in theory how transistors work but don't have a clue how to implement them in a circuit.

Anyway...
Everyone knows pins 33+36, bridged with <500R activates the PSU.
Less well known is that pin 34, emits an 'indicator voltage' that represents the current output.
For an output >20A the indicator voltage is roughly I x 0.032 - 0.4
So 2.8v represents 100A, 2.0v is 75A

As above in this thread, I have a 'control resistance' between the trim pot and ground which, as it reduces, increases the output voltage (and hence the current) of the PSU.

What I'd like to do is to automagically manage the control resistance based on this indicator voltage.
eg. As the indicator starts to exceed 2.5v, increase the control resistance to bring the output back down.

The thing is, I can think of ways to reduce the resistance as a result of increased voltage (eg. an LDR/optoisolator) but I don't know how to do the opposite. I assume this would be childsplay for many folk on this forum but I'm afraid I am 'enthusiastic but relatively clueless'.

btw. if the answer is, "why are you even bothering? It would be much simpler to your simple solution here" please do fire away...

[MickeeYay]

I'd still really like to know if anyone managed to solve the OVP issue though.

Try this and report back.

Brilliant. Worked for me. Thanks..

[MickeeYay]

There's a lot of attentions on the HSTNS-PL11 with its small size but hefty 100A 12V output. As I've just put together an electronic 'wattmeter' (see image) using an AliExpress bought module, I might as well measure how these supplies perform on standby and idle. The following are my findings.

The no load wattage shown are in the range of 42~44W for PL11, double checked with several PL11 power supplies. What it means is the power supply is consuming 44W with 12V but no load attached. This figure seems exceptionally high and unreasonable compares to different models of server power supply.

It would be helpful if anyone with a HSTNS-PL11 and wattmeter can either confirm or rebute the figure using other makes of wattmeter.

I don't have a wattmeter but I measured the current draw on the mains side of my PL11 with DC on and I got 0.17A @ 230V = 39.1W

That is very high for idle use. The 6 LED downlights in my living room use less power.

Surely it's not the fan drawing that much current?

[eblc1388]

I don't have a wattmeter but I measured the current draw on the mains side of my PL11 with DC on and I got 0.17A @ 230V = 39.1W

That is very high for idle use. The 6 LED downlights in my living room use less power.

Surely it's not the fan drawing that much current?

Thanks for the measurement. However, with DC ON and no load, the power factor is not unity, therefore a wattmeter is required to measure the actual power consumption.

I don't think the fan would draw that much power, all other power supplies I tested have fans too.
 

[eblc1388]

What I'd like to do is to automagically manage the control resistance based on this indicator voltage.
eg. As the indicator starts to exceed 2.5v, increase the control resistance to bring the output back down.

The thing is, I can think of ways to reduce the resistance as a result of increased voltage (eg. an LDR/optoisolator) but I don't know how to do the opposite.

Actually you've have got a very good idea and it might work, it just need a little twist in your thinking. Simply put, the power supply output voltage is sampled via a voltage divider, consists of a top and bottom resistor in series. You've already known how to change the sampled voltage by changing the value of the bottom resistor element. However, you can also do the same with the top element too. By reducing the value of the top element, you can mimic an increase in output voltage as the sampled voltage is now larger. The control circuit will then works to reduce the power supply output voltage as a result.

However, will it actually works? Well one won't know if one don't try. I rigged up the few parts needed and tried it on my supply. In the schematic below, the current signal from edge connector pin#34 is fed to an emitter follower made up of NPN 2N3904, with the 470R trim POT as load. It is advisable to make sure the wiper is at the NPN emitter position before testing the circuit. This current limit can be totally disabled by setting the wiper to the fully clockwise(i.e. to GND) position. The parts like NPN, optocoupler and POT values are not critical. Mine works with a 5K POT but the control range is small.

Yes, I can limit the current to 40A as the output voltage reduces from 12.2V down to 9.8V, with the POT wiper set at the fully anti-clockwise(i.e. at the NPN emiter) position. However, the current limit is gradual and it is difficult to conduct a proper test without an electronic load.

[ubrain]

Uh! eblc1388, You are an absolute legend!
I had spent quite a lot of time researching and learning, trying to figure this out from basics, but at a certain point my brain was feeling a bit full, I wasn't sure I was getting anywhere and I was using time that I should really have been spending on work and well, one needs to be careful not to get obsessed 
However... thank you for your reassurance and actually I was getting pretty close - it is fair to say that I have understood your explanation much better for the learning that I've done over the past few days so it's a WIN after all 

I need to get the bits ordered - annoyingly, having just discovered I had an electronics store within easy reach, within 48hrs it had closed for lockdown!
If only Amazon did 2hr delivery on transistors.

[ubrain]

I have two HP HSTNS-PL11 and was wondering if anyone has done the voltage adjustment mod with the 6.8k resistor on the voltage adjust pot. And has someone also put the 12k resistor on the voltage regulators to override the OVP at the same time. Looking to find the max working output voltage before the OVP kicks in. 

I did both changes. The voltage goes up to 14.41v (which was my target) and the OVP doesn't kick in by then.
How far did you want to go?

[paulzedx636]

 Thanks for the reply I've done both mods too. I'm trying to get 14.41v I'm getting 14.32 under load without shutting down. I think it may be since my 6.8k resistor measures at 6.9k I'm not sure if I need to go a little lower or higher in resistance to get get to 14.41v. 😅

[ubrain]

Yes, reduce it a little to go up further.
I didn't have a 6k8 handy so actually used a 5k7 + 1k in series and got exactly what you're trying to get to.
btw. I was experimenting last night and wound the voltage up to 15.5v without OVP kicking in. There was no load at the time though so I don't know how much use that info is.

[paulzedx636]

 Thank you for the information, I will try it on the one l haven't modded yet. I think 16.68v is the upper limit without further mods, as I had solder grounding on the pot where you place the 6.8k resistor. In this scenario I had no adjustability and have corrected the problem. If someone was to take the voltage that high they would have to change the output capacitors to 25v as their only rated for 16v. 😁