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Old 11-05-2018, 10:22 AM   #21
budm
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Default Re: I Don't Understand

Is it really pulsing? What is the ON time and OFF time of the pulse being applied to the LED's?
And are you using that constant current source circuit as you have shown to drive the LED's?
What did you use to limit the current to the LED's? Just remember that LED is current device, you have to manage the current flowing through it, you do not hook them up to constant Voltage source and hoping it will not blow up, you use constant current source to drive LED.
That power supply board looks like capacitive dropper type.
Are there any parts on the bottom side of the board.
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Last edited by budm; 11-05-2018 at 10:28 AM..
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Old 11-05-2018, 01:25 PM   #22
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Default Re: I Don't Understand

Quote:
Originally Posted by budm View Post
Is it really pulsing? What is the ON time and OFF time of the pulse being applied to the LED's?
So this is kind of interesting ... here is the voltage with the stock circuit powering the new LEDs with no other modifications:



and here is the same exact thing with an added 400Ω resistor in series



it definitely pulses on and off with the resistor in series ... by the way I tested this earlier with my ammeter and it still draws 170ma even with a series resistor in place and even when it flashes...

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And are you using that constant current source circuit as you have shown to drive the LED's?
NO I canned that circuit.

Quote:
Originally Posted by budm View Post
What did you use to limit the current to the LED's? Just remember that LED is current device, you have to manage the current flowing through it, you do not hook them up to constant Voltage source and hoping it will not blow up, you use constant current source to drive LED.
That power supply board looks like capacitive dropper type.
Are there any parts on the bottom side of the board.
I am well aware that LEDs are a current sourcing device and that exceeding the rated current is bad juju and I know that you should never run them without a limiting resistor OR a constant current power supply.

and NO there is nothing on the underside of the board.
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File Type: jpg originalcircuitnewleds.jpg (125.0 KB, 1 views)
File Type: jpg originalwithresistor.jpg (147.7 KB, 1 views)
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Old 11-05-2018, 02:25 PM   #23
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Default Re: I Don't Understand

I do not understand the 'ORIGINAL CIRCUIT', what is the ORIGINAL CIRCUIT? The power supply module? You should also shows the bottom side of the board so we can see how the output section is setup, it may be setup as constant current source already.
So the second picture shows ripple (5V P-P) riding on top of 12.5VDC. at what test point is that?
15V source (based on you scope showing 5V per division with compensation with x10 PROBE) with 400 Ohms so the max shorted current will be 15V/400 Ohms = 37.5mA so how many LED's are connected in series with that resistor?

Last edited by budm; 11-05-2018 at 02:38 PM..
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Old 11-05-2018, 04:15 PM   #24
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Default Re: I Don't Understand

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I do not understand the 'ORIGINAL CIRCUIT', what is the ORIGINAL CIRCUIT? The power supply module? You should also shows the bottom side of the board so we can see how the output section is setup, it may be setup as constant current source already.
So the second picture shows ripple (5V P-P) riding on top of 12.5VDC. at what test point is that?
15V source (based on you scope showing 5V per division with compensation with x10 PROBE) with 400 Ohms so the max shorted current will be 15V/400 Ohms = 37.5mA so how many LED's are connected in series with that resistor?
ORIGINAL CIRCUIT = Driver circuit installed in the lamp from the factory ... the "original" ... no modifications, and no additions to the output etc.

OK, so when I said there was nothing on the underside of this board, I made a mistake ... I was thinking of my other thread about the flashlight circuit ... this one does have stuff on the bottom ... here is the picture... I reversed one of the images so that the components line up properly ... you'll see what I mean ...

I have NINE LEDs in series but only 4 are working now ... here are the exact LEDs that I'm using:

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Old 11-05-2018, 04:42 PM   #25
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Default Re: I Don't Understand

Hey Budm,

What do you think about replacing this circuit with a capacitive dropper as STJ suggested?
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Old 11-05-2018, 10:20 PM   #26
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Default Re: I Don't Understand

That looks to be non-isolated constant current power supply (HOT chassis, so I hope you are using scope without the safety connected which is dangerous or connect this board to isolation transformer), what are the P/N of IC U1, U2?

Last edited by budm; 11-05-2018 at 10:44 PM..
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Old 11-06-2018, 06:41 AM   #27
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Default Re: I Don't Understand

recap that psu - the small ones anyway.
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Old 11-06-2018, 02:12 PM   #28
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Default Re: I Don't Understand

Quote:
OK, so when I said there was nothing on the underside of this board, I made a mistake ...
offcourse you did, there were no semiconductors on the top side, so nothing to rectify mains ac etc.

that small smps pos(like "cheap chinese piece of shit") has no power and that's why it starts to pulse as soon as you (over)load it, and it doesn't take much.

can you power it from pc psu?

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Old 11-06-2018, 04:57 PM   #29
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Default Re: I Don't Understand

Quote:
Originally Posted by budm View Post
That looks to be non-isolated constant current power supply (HOT chassis, so I hope you are using scope without the safety connected which is dangerous or connect this board to isolation transformer), what are the P/N of IC U1, U2?
Look at the attached image ... the power comes in through that ... im assuming thats an isolation transformer?

U1
BP2326A
16D30A
DEG26 or OEG26 or CEG26

U2
BP5602
16C14A
BRG23
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Old 11-06-2018, 05:38 PM   #30
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Default Re: I Don't Understand

looks like a connector block ..
p.s there seems to be a stray bare wire melted into the wire nut .
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Old 11-06-2018, 05:40 PM   #31
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Default Re: I Don't Understand

unless i am thinking wrong the isolation transformer goes before the scope . or is the DUT ?
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Old 11-06-2018, 09:53 PM   #32
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Default Re: I Don't Understand

You will plug the device to be tested into the Isolation transformer (L and N are floated).
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Old 11-06-2018, 09:56 PM   #33
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Default Re: I Don't Understand

https://www.badcaps.net/forum/attach...8&d=1541545003
Looks like line filter, rated at 3A 12VAC.
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Old 11-06-2018, 10:15 PM   #34
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Default Re: I Don't Understand

U1 BP2326:
http://www.chinesechip.com/files/201...a12c881995.pdf

U2 BP5602: http://bpsemi.com.cn/uploads/file/20...170036_863.ppt


Looking at the board layout, it looks like U1 (BP2326) is set up as the Buck converter to supply the Voltage to run the U2 (BP5602) LED driver.
Resistors (R13/R13 1 (2R20 Ohms in parallel = 1.1 Ohms) connected in parallel) at CS pins 7 & 8 of BP5602 determine the LED current setting.
Formula: Rcs = 0.2V/Iout, that means it is set for about 180mA (Iout = 0.2V/1.1 Ohms) of constant current which is what you have found out in the earlier test. So when you put 400 Ohms in series, there is no way the circuit can force 180mA through 400 Ohms resistor + the LED's, the power supply does not have enough Voltage to force 180mA through, 400 Ohms x 0.18A = 72V so no way it will happen.
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File Type: pdf BP2326A.pdf (368.9 KB, 2 views)

Last edited by budm; 11-06-2018 at 11:32 PM..
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Old 11-07-2018, 07:12 AM   #35
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Default Re: I Don't Understand

Quote:
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looks like a connector block ..
p.s there seems to be a stray bare wire melted into the wire nut .
Actually, it ended up being the on off switch...
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Old 11-07-2018, 07:13 AM   #36
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Quote:
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https://www.badcaps.net/forum/attach...8&d=1541545003
Looks like line filter, rated at 3A 12VAC.
Ended up being the on off switch ... I'll take a BIG FAT ZERO for that one ...
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Old 11-07-2018, 07:26 AM   #37
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Default Re: I Don't Understand

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So when you put 400 Ohms in series, there is no way the circuit can force 180mA through 400 Ohms resistor + the LED's, the power supply does not have enough Voltage to force 180mA through, 400 Ohms x 0.18A = 72V so no way it will happen.
When I dropped the series resistor down low enough to make it stop blinking, it still drew 170ma ... and when I had the 400 in there, it drew 170ma ... just not constantly (obviously) ... its as if a series resistor didn't do Diddley squat for limiting current ... which kind of makes sense if the power supply is a CC at 180ma .... what respectable CC power supply would give two craps about a pesky series resistor ... just another obstacle to overcome for the power supply is all ... it's gonna deliver 180ma come hell or high water ... or pulse on and off like a whiney two year old if the load is too heavy ... but at least it's putting forth a valiant effort...

So all of this analysis of the circuit was fun and all ... but the question is still on the table: How do I take 120V AC and kick out some decent DC voltage at roughly 100 to 120 milliamps in the small space I have to work in? Remember STJ recommended the capacitive dropper ... what are your thoughts on that option?

OR, are you thinking we could modify the existing power source to put out less current so my LEDs don't go belly up? .... THAT actually sounds like FUN!

Last edited by EasyGoing1; 11-07-2018 at 07:31 AM.. Reason: Added a thought...
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Old 11-07-2018, 10:34 AM   #38
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Default Re: I Don't Understand

It cannot force 180mA through 400 Ohms resistor if the power supply cannot go up high enough to force 180mA through the resistor, the Voltage across the load is varied to maintain constant current.
"How do I take 120V AC and kick out some decent DC voltage at roughly 100 to 120 milliamps in the small space I have to work in? Remember STJ recommended the capacitive dropper ... what are your thoughts on that option?"
First question will be what is the load? 1 LED? 10 LEDs, 100 LED's? You need to know what the load requirement is first, you already know what the required current but now you need to know the load requirement is so you can make power supply that puts out enough Voltage to force 120mA through the load.
So what are you going to do with that power supply? It is a good CC power supply that should be re-capped with good caps.

Last edited by budm; 11-07-2018 at 10:36 AM..
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Old 11-07-2018, 01:42 PM   #39
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Default Re: I Don't Understand

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First question will be what is the load?
I was thinking 9 LEDs in series ... rated at 3v / 150ma so I'm thinking the power supply should be able to supply roughly 30 volts at 150ma?

Quote:
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So what are you going to do with that power supply? It is a good CC power supply that should be re-capped with good caps.
What's your definition of "good caps"? and where would I get them?
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Old 11-07-2018, 10:09 PM   #40
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Default Re: I Don't Understand

I would run constant current of 120mA (80% of the max spec.).
The VF of the LED will vary withe current flwoing through the LED, temperature all affect Vf, that is why you should use constant current source, 30V may be OK it depends on the Vdrops of the Constant current active control element at the needed current and variation of the total Vf of the LED string, you want it to have head room for the Output Voltage to go up and down as needed to maintain constant current.
See page 12 of the graph which is typical spec provided by the LED manufacturer which I doubt if you have it for your LED. If you have constant current power supply then you do the measurement and see what you get with your LEDs you will be using.

https://www.bridgelux.com/sites/defa...%20Rev%20B.pdf

Good caps: I.E. Panasonic FM/FC/FR series, and many other Japanese manufacturer.

Last edited by budm; 11-07-2018 at 10:11 PM..
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