PLP-60-48 Single Output LED Power Supply - "chirping" noise

[harp]

I read your '240v is fine - only the wattage matters' as 'voltage doesn't matter'

LOL, fearless logic...

[CapLeaker]

So you reused that same little board on the new PSU and it’s same thing what it was before? It’s the little board alright. I’d go for the MOSFET, the diode and the two large SMD caps first. If the mosfet is bad, you have to check the gate drive IC as well.

[sam_sam_sam]

I was thinking the same thing about the mosfet possibly being shorted I would agree with you about that

[stj]

deleted post

[tester001]

Based on the overview of the components and its placement within the device, can you tell what the little board does?





For example, if you say that the purpose of the little board is to conver 48V DC (constant current) to 40V DC (as the device specifies), I'd be tempted to replace the board with an equivalent that would bring down the voltage.

Thank you in advance.


EDIT:
I've done a bit of legwork online, and my guess is that the little board is a 48v -> 40v 60W buck converter

[sam_sam_sam]

Based on the overview of the components and its placement within the device, can you tell what the little board does?





For example, if you say that the purpose of the little board is to conver 48V DC (constant current) to 40V DC (as the device specifies), I'd be tempted to replace the board with an equivalent that would bring down the voltage.

Thank you in advance.


EDIT:
I've done a bit of legwork online, and my guess is that the little board is a 48v -> 40v 60W buck converter

Thank you for posting this because now it makes sense about what this little board does if the LED light fixture actually works on 40 volts because this not a standard voltage for a switching power supply

[CapLeaker]

It’s a converter all right, but I think it may be a boost converter, not a buck converter, as the inductive coil is before the mosfet, not after. Seeing the PSU itself without this little board is adjustable too, I think, the output voltage of the little board got to be out of range of the PSU itself?
Make a note of the PSU’s output, make a mark with a waterproof pen on the blue variable resistor right next to the secondary output caps and turn it. The voltage should go up and down. What is the voltage written on these caps on the little board?

[tester001]

It's a converter all right, but I think it may be a boost converter, not a buck converter, as the inductive coil is before the mosfet, not after.

Could be! I replaced the little board with this:

And set the adjustable power supply to output 40V with 1.5A max. The LED device sprung to life!
I ran it for a while in different modes and noted that it didn't draw more than 38W in power (as displayed at the adjustable power supply above).

Seeing the PSU itself without this little board is adjustable too, I think, the output voltage of the little board got to be out of range of the PSU itself?

I don't know. But I can confirm that the device works great when fed with 40V 1.5A max, as tested this morning.

Make a note of the PSU's output, make a mark with a waterproof pen on the blue variable resistor right next to the secondary output caps and turn it.
The voltage should go up and down. What is the voltage written on these caps on the little board?

This is an awesome idea! I can't see that it's allowed in the datasheet, but it might be. Let me try to get 40V out of it..

[tester001]

Turning the SVR1 knob on the PSU made absolutely no difference to the voltage read on the CN2 outputs - it stayed at 47.8 V


What does this resistor actually do?

[sam_sam_sam]

Turning the SVR1 knob on the PSU made absolutely no difference to the voltage read on the CN2 outputs - it stayed at 47.8 V


What does this resistor actually do?

If I read the data sheet correctly it would adjust the current not the voltage you would have to have a load on it when you adjust the pot control

[sam_sam_sam]

Could be! I replaced the little board with this:

And set the adjustable power supply to output 40V with 1.5A max. The LED device sprung to life!

Did you try adjusting the buck converter to a slight higher voltage than 40 volts I suspect that your current would go up somewhat as well but do not exceed the current rating of the LED light module otherwise you could damage it if pulls to much current
if It bright enough at 40 volts try it at a lower voltage until it gets real dim or LED light bulbs go dark and then increase the voltage until all of the LED lights bulbs are lighting and see what voltage that is then you can determine what is the best voltage to run it at with the least amount of current the LED light module will last longer in the long run

[tester001]

EDIT: duplicate post

[tester001]

Do you mean adjusting the output voltage on the adjustable power supply I have posted above?

I could, but I usually connect its output to the module that controls the LED - I'm worried that I might damage it if I supply, say, 48 volts instead of 40.

Not sure what to do really. I've ordered this buck converter https://www.aliexpress.com/item/1005004336673431.html but I suspect it would crumble when having to deliver 30 W to the LED, even if I install the heatsink.
There is no room within the case for a larger, more powerful buck converter or an adjustable Mean Well PSU model that outputs 40v.
Whoever designed this device felt that this little board was capable of acting as a reliable buck converter from 48v to 40v at 1.2A, but all models for such spec that I've seen online are much larger and have heatsinks. To make matters worse we can't even identify the mosfet model used - must be some noname chip that is no longer manufactured

[tester001]

To everyone who has been celebrating - Merry Christmas!

With help from colleagues I have desoldered the mosfet from the buck converter board and the resistance across the input terminals is now 159 Ohms.



Should it have increased after de-soldering the mosfet if that component was broken? Just trying to understand the logic behind questining the low resistance across the input terminals being a sign of the problem.

Thank you!

[CapLeaker]

Take that mlcc smd capacitor above the 2 pin prong out and check it out of circuit.

[tester001]

Take that mlcc smd capacitor above the 2 pin prong out and check it out of circuit.

Thank you for your suggestion!

I've taken the capacitor out of the circuit and the meter fails to get a capacitance reading (I gave it time!):


The resistance across the input prongs of the little board with one polarity is now 1.795 kOhm and if I switch the probes around it is 34 kOhm.

Does this mean anything?

[CapLeaker]

Shorted input capacitor. Check the resistance of that cap and you see it has the weird ohms you measured before between these 2 pins. You can just put a regular electrolytic capacitor in its place (keep the polarity of the cap in mind) like 63v or 100v at 10, 22 or 33uF. This circuit should work without this cap too.

[tester001]

Hi CapLeaker,
Sorry! I've not been very clear. The removed capacitor is showing resistance of 4-5 MOhm and counting. Unable to get capacitance reading.

The 1.795 kOhm and if I switch the probes around it is 34 kOhm resistance readings are now across the prongs with capacitor removed.

[CapLeaker]

Is that mosfet out too?

[tester001]

Is that mosfet out too?

Yes, Mosfet has been out (as pictured a few posts above) and the little yello cap that was above the prongs is now out too