Inside the Owon P4603/P4305 linear PSU

[Pnoxi]

Today I bought a new power supply Owon P4603 60V/3A, 180W, resolution 1mV/1mA, 3.7 inch TFT LCD display, RS232 - 137.55€ (My version does not have USB and Voltage/Current Curve)



Some components:
4xNPN - NJW0281G
CPU - GD32F103 + C8051F350 (ADC,DAC?)
Op-amp - SGMOP17C ?
Toroid 250VA ?

Pros:
60V/3A (P4603), 30V/5A (P4305)
Linear PSU
Nice, clear display shows all the necessary information
Simple, intuitive control
Response time <100uS (I can't verify it!)
Adjustment accuracy 1mV/1mA
Power measurement
Backlit button (Output On/Off)

Cons:
The Keylock button must be held for at least 10 seconds
Unable to switch off OVP, OCP (maximum set value 3.1A / 61V)
The changed settings are not saved immediately (system settings, stored values), the PSU must be left on for some time
It is noisy at maximum load
It does not have a USB only RS232


Manual:
http://files.owon.com.cn/probook/Single_Output_Power_Supply_USER_MANUAL.pdf

Site:
https://www.owon.com.hk/products_owon_1ch_liner_dc_power_supply

Few photos:

[Kleinstein]

The shunt and the power transistors look good. However the current rating on the transformer is somewhat suspicious, as I don't see a switched mode part. Normally a 3 A transformer is good for some 1.8-2 A of DC current (if the filter cap is no too large). So I would be a little careful using the full 3 A current for an extended time, especially at higher voltage.

The ratings on the transformer could be about 220-250 VA: 3 A at some 65 V + some smaller windings.
The 65 V value is rather high - lots of spare voltage for ripple.

THE C8051F350 sound like a µC with integrated high resolution ADC.

[Pnoxi]

A weak transformer is a problem for most cheap power supplies.
Behind the cooler are two relays for connecting the transformer winding.

I made a video review, you can find it in the first post. (I don't have an oscilloscope for a more accurate review...)

[Pnoxi]

Here are some images from oscilloscope. I'll do a more thorough test later.

Set voltage is 3.3V.

Power On (Main Power 230V)


Short (CV -> CC):

[Cliff Matthews]

Good review. If Owon could drop the price another $50, these would fly off the shelves! I like the vertical layout and deeper cabinet, it makes for more bench room (perhaps they could have tilted the display up 10-15 degrees). One thing about your changes not being saved (eg: at 3:52 you were supposed to hit OK to confirm changes).

[Pnoxi]

Hello,
My changes will not be saved even if I press OK.
It must go some time on to save it. Probably the changes are stored in the EEPROM through the task at regular intervals.

And see the results from the oscilloscope measurement, it doesn't look nice.
https://www.eevblog.com/forum/testgear/inside-the-owon-p4603p4305-linear-psu/msg2298918/#msg2298918

[tooki]

Ugh, the fonts! Why use a nice TFT, only to make it simulate crappy 7-segment LCD? Why not use a proper font (and a nicer font for the labels, hotkeys and stuff)… Seems like a slow update rate on the meter, too. (The set voltage seems to update quickly, but the actual measured output seems to lag significantly.)

And that buzzer would make me want to kill myself. It can't be THAT hard to make pleasant-sounding beeps instead of the sound of squeaky toys being tortured.

Pity, it's just software issues on what seems like decent hardware.

[Phildem]

Hi,

I just tested one. Not so bad but the OVP and OCP are useless, and NOT SAFE.
If you set OVP to 6V and set output to 25V, there is 25V at the output and after a delay, it switch off.
The delay is long enough to kill any electronics...
I'll mad a video on it tomorrow and show it.

[Pnoxi]

Yes, OVP and OCP are slow. I do not understand why they did not solve it software in order to limit the maximum voltage and current setting according to the set OVP and OCP

What is your software version? I have 1.4.0

[Phildem]

Hi, Yes me too but more of that it's inefficient.

Example : OVP Set to 13V Output set to 22V, if I enable the output, I got 22V for near 400ms ! greatly enough to kill any electronics. (see scope screenshot)

It's not a bad PSU but for me OVP and OCP are useless and should be ignored

My Firmware is 1.4.0 too.
I haven't seen any upgrade available, but the manual on OWON website show enhancement.

[exe]

Why use a nice TFT, only to make it simulate crappy 7-segment LCD?

I actually like it this way.

The ratings on the transformer could be about 220-250 VA: 3 A at some 65 V + some smaller windings.

I see "300" on the photo. Of course it's not granted the rating is real. Only load testing and temperature measurement can tell the truth.

[exe]

I see the psu allows setting separate CV/CC and OVP/OCP. I don't get why OVP/OCP are needed.

[Phildem]

Hi,

My video review about this supply (In French)

https://youtu.be/lUjqdLF8L-8

[M1ch4L]

Hello everyone.

I'm thinking about to buy this power supply. Owners ... after a few months of use … are you satisfied with this?
I am new in electronics and I want learn about repairing notebooks, phones, etc ... one important question is: Can I find the short on the circuit with this supply?   … or if the short is there the output is turned off fast and automatically?

[RedSky]

I note there is now a rebadged Owon P4603 model on the market:

Multicomp MP710087
https://au.element14.com/multicomp-pro/mp710087/dc-power-supply-1ch-60v-3a-180w/dp/3227421

I have bought one, looks almost identical inside and out to the Owon.  Edit: Except this one has USB connectivity as well as RS232, and newer firmware

At $315 it's fairly well priced for us Aussies, even with its noted issues.

[vutt]

27.08.2020 update: Added inside pic. It looks like 30V version is using lower  temp rated (only 85C) caps. Also brand is different.

Well I pulled the trigger on 30V Multicomp PRO version . In my Country in EU it cost 154 EUR +VAT.
I was hoping that some of the shortcomings have been fixed because newer SW version.

But no. Same spikes when turning AC power on

And O.V.P. is as slow as with OWON version (OVP was set at 13V)


Also any changes in parameters will require up to 25 sec wait time before actual memory save will happen.

However I'm quite happy with it regardless. It is step up from my Gophert NPS-1601. Well except in noise department.

[John B]

I'm looking at purchasing the Multicomp Pro rebranded version of this unit, the 60V 3A model with USB/RS232 specifically. Am I right in thinking that the issues are still present in the unit?

The other slightly cheaper option is the Tenma branded lineup which I think is a Korad unit:

https://au.element14.com/tenma/72-2550/power-supply-1ch-60v-3a-prog/dp/244541402

My only experience with them is that Dave Jones blew up one like 8 years ago, so I have no info on whether the design has been improved enough over the years. I'm just looking to add another channel with 60V output natively, I don't absolutely need the extra features on the Multicomp unit (power reading is nice), but I'm willing to spend a bit extra if the unit has less issues than the Korad/Tenma units.

[MarkF]

At that price, I would sooner have the Siglent SPD1305X for $20 more instead of the Owon.
30 volts, 5 amps, USB interface and sense lines.



Defpom did a review: 

[rdl]

They did make changes to fix the Korad power supply. There was a video posted on Dave's "Altzone" youtube channel.

https://youtu.be/uecvB4U1fps

[tautech]

At that price, I would sooner have the Siglent SPD1305X

Defpom did a review:  ...................

Then he ordered the 16V 8A unit from us.

Thread:
https://www.eevblog.com/forum/testgear/new-spd1168x-siglent-psu/

[MarkF]

At that price, I would sooner have the Siglent SPD1305X

Defpom did a review:  ...................

Then he ordered the 16V 8A unit from us.

Thread:
https://www.eevblog.com/forum/testgear/new-spd1168x-siglent-psu/

Yes, I remember watching his reviews of both models and that he bought one of them.

Some day I'll break down and get a Silent.
However, I have four of the little HP-6216A power supplies.  They were in my electronics lab in college and I instantly fell in love with them.  Only are 0.5 amp but you can parallel or series them together.

[Old Printer]

[/quote]
However, I have four of the little HP-6216A power supplies.  They were in my electronics lab in college and I instantly fell in love with them.  Only are 0.5 amp but you can parallel or series them together.
[/quote]

I have several of these as well, they are great for light duty bench work and can be found on eBay for $30-$50 if you wait a bit. Dead quiet, stackable and compact. I am working on an add-on digital volt & amp meter as the analog meter scales are a bit small fo my old eyes 😀

[Hydron]

Can anyone confirm if the turn-on spike occurs with any meaningful load attached? Spike seems very short, so I'm wondering a) if it's even real and b) if it has any significant energy. I can live with the OCP/OVP being worthless - never really use these anyway, so this seems to be the biggest concern left.

[John B]

Can anyone confirm if the turn-on spike occurs with any meaningful load attached? Spike seems very short, so I'm wondering a) if it's even real and b) if it has any significant energy. I can live with the OCP/OVP being worthless - never really use these anyway, so this seems to be the biggest concern left.

Just a warning that from the videos I saw, it looks like the voltage at the output doesn't update immediately with turning the rotary encoder. Owners of the unit can confirm it's functionality, but that was enough to turn me off buying it.

[GeorgeLouis]

Will this work in 120V 60Hz AC power line. Is there any way to change it's input voltage range.

[Pnoxi]

The manual says:

110 VAC ± 10% or 220 VAC ± 10% (Power is suppliedaccording to the marking on the left side of the powerinput socket on the rear panel of the instrument); ACinput 50/60 Hz

My version is 230V 50Hz. Since it is a linear source with a transformer, it is possible that the transformer will be different in the 110V version, so you have to buy the 110V version (If it exists).

[james38]

I know that this is an old Thread but i found an interesting info on how to calibrate this thing.
I have seen in this video where someone calibrate the current on the PSU.


To enter the special Menu do the folllowing:
Enter Calibration Menu:
System -> Up -> Ok -> Right -> Down

Be aware that the output is automatically ON!

For voltage calibration choose MAN VOLT.
You see a smal chart. Heading volt and then a number
You can navigate with up/down.
The small arrow dedicates which vale you can update.
The value can be updated with the rotary knob.

On the first rown you see under Volt a value which designates the voltage which should be on the Output. Check the voltage with an accurate multimeter.
Adjust the Value with the rotary knob until you get an nearly close value.

The second row  you see also a voltage but this is the measured voltage from the PSU. If you adjust the first row you will see that this value will be show another value.
Adjust the value with the rotary knob until you get an nearly close value to the voltage in the first row.

The P4305 hast in this Menu 4 calibration voltages which should be checked.
To change the calibration voltages got to the header row and
change the other values with the rotary knob.

On Cal-Menu 0 you adjust 50mV
On Cal-Menu 1 you adjust 100mV
On Cal-Menu 2 you adjust 1V
On Cal-Menu 3 you adjust 30V

To save the adjusted values do the following:
Save the Values:
System -> Up -> Ok -> Right -> Down

Thats all.
The same procedure are for MAN CURR.

The Menu VOLT,CURR AND ALL

Writes this on screen:
Start PSU wave from rectify
Meter communication failure
rebuf:

Don't know whats this meant.

Hope this info helps someone.

Regards Chris

[dietert1]

Recently we got 2x P4305 mainly because they are easy to automate using their serial interface. I found a "ODP Series DC Power Supply Programming Manual" on the CD that came with it. There are no manuals for this product, but manuals for similar OWON products.
Fan has temperature control, toroidal mains transformer. Wideband output noise is about 40 mVpp.
The incomplete overvoltage/overcurrent implementation mentioned above can be completed on the host side. I mean the host can clip the set voltage and current to be inside the limits before setting them.
Appended linearity tests are sweeps of measured output voltage deviation from set voltage, 0.1 V steps every 2 seconds. With and without load the average deviation is about -1 mV, for both units out of the box.
Comparison with a Keithley 2700 gave good results, too. I mean the built-in meters of the power supplies are well calibrated and agree to their last digit, e.g. 4,998 V was 4,99797 V on the K2700 with about +/- 20 uV short term stability. On the other unit 30.000 or 29.999 V was displayed and gave 30.0003 V on the K2700.

Best regards, Dieter

[dietert1]

Meanwhile i repeated the linearity test of one unit, using a Keithley 2700 to measure the output voltage (100 V range, Autorange off). And i extended the sweep scanning down after scanning up. Now it gets a little more interesting:

- Looks like they use the same voltage reference for the DAC generating the output voltage and the built-in meter. This way they hide most of the reference drift with temperature. It amounts to about -2.7 mV per 2 °C at 30 V out (45 ppm/K)

- The temperature dependence is also visible when scanning with load. Then the fan starts running at medium output voltages. That apparently affects the voltage reference. There is no such effect when running without load.

- While the measurements are rather smooth up to 17.5 V, above that there is a pattern in steps of 2 V. That DAC is somewhat "hybrid". The other unit doesn't have this, yet it has lost about 10 mV at 30 V.

On a closer look i can't really confirm the pretended "1 mV" quality.

Regards, Dieter

Edit: The voltage reference U4 sits near C8051F350 reference input pin 31. It is a TI REF3025 with device marking: R30C and specified with +/- 50 ppm/K. Chip appeared to be hand soldered.

[dietert1]

Another circuit common to the voltage regulator and the built-in DVM is the output sense amplifier, see appended schematic. In heating tests it appeared more sensitive than the reference. First i suspected leakage in the MLCC caps C152/C153 and replaced them by film caps. This did not help.
Will try with better divider resistors (100K 39K, 10K).
By the way, Agilent 6632B programming accuracy is +/- 10 mV. It may have other advantages, though.

Regards, Dieter

[dietert1]

Thinking about how to proceed, i decided to wire a Keithley 2700 with three channels of a 7706 multiplexer to record the P4305 output voltage, the reference voltage and the output of the output voltage measurement (schematic above). The diagrams once more show an up and then down scan of the P4305 set voltage from 0.01 to 30 V and then back. With a 8.25 Ohm load the fan starts running at about 15 V and doesn's stop until the end of the down scan.
Apparently the voltage reference is rather stable even with the fan running. The voltage measurement stage is the culprit and its deviations explain more than 80 or 90 % of the behaviour i reported above. Maybe the SMD resistors they used for the voltage divider aren't good enough.
Also note the P4305 output voltage deviations are now half of what i saw before when measuring voltage on its output terminals, with the load taking up to 3 A. Of course, in order to have the unit perform to 1 mV under load, it will need to operate in four wire mode. I will probably try to add a 4-pin socket on the front panel to support 2-wire mode with a shorting plug and 4-wire mode using external sense lines.

Regards, Dieter

[dietert1]

When i took out the rear RS232 interface to fit the missing buffer cap, it was already there.
Meanwhile i took out the six sense amplifier gain resistors and characterized them to be 0.1% 50ppm/K type. The 10K resistors were about 36 ppm/K while the 100k+39k gave -18 ppmm/K. So this explains the 50 ppm/K output deviation seen before.
I inserted 10K, 2 ppm/K and 47K, 5 ppm/K SMD resistors (3x 47K = 141K) and they solved the temperature dependence. Using the description above (by james38) i could calibrate the unit with the new resistors, except below 1 V. There remains some deviation of up to 12 mV. Note that 912 mV / 900 mV * 139,2 KOhm = 141 KOhm.
I also added the 4W connector. It's a small 4 pin connector (binder 719 09-9764-70-04), in order to support 2W mode with a shorting plug. Now i can say it's a 1 mV unit.

Regards Dieter

[dietert1]

In order to reduce the residual deviations below 1 V output voltage i ordered some 0.1 % resistors 1M and 57K6. They change a 47K precision resistor to 45K, so one gets closer to the original: 100K + 39K = 2 * 47K + 45K. Now the linearity sweep stays within +/- 1 mV.
The no load case has a minor deviation between upward and downward scan. During the downward scan the 5 sec delay time after each 0.1 V adjustment leaves charge in the output caps to settle.

Regards, Dieter