TL494: TL494- DC-DC converter -metal core constant current 200W module

This is the moduel I am referring to. Does nyone have the electric diagram of it?

This is the chinese module I am referring to . Does anyone have the electric diagram available?

Hello Mario,
Do you mean that the set current is higher than expected and that it corrects itself after 0.5 seconds ?
It sounds like something in the circuit is not accurately sensing the current and takes time to correct itself.
This is unlikely to be the TL494.
It may be that there is a bad solder joint on the current sense circuit or some other mechanical issue with the power supply.
I suggest you visually inspect the pcb and reflow the solder wherever you see poor workmanship.
Have you contacted your supplier of the power supply and asked for their suggestions ?

Regards
John

When i start up the module, there is an undesireble peak of current that takes 0,5 second to corect itself. However when I reduce 1-2 Volts of the input voltage and start up the module again, the circuit cannot correct itself and the current stays in the maximal value , compromising the module. As I do not have the diagram available, the first thing I did was re-soldering all components. Unfortunately it did not produce any effect. I only was succesfull when replaced the TL494. But again, I cannot say it is the TL494 the responsible for the problem.

Hi John
I just re-soldered all component of the module, but it did not work. then I replaced the TL494(without extension) by a TL494C and it worked back. another point to be considered: I tested 50 modules. 100% presented the same behavior.(start up current peak is present). the difference is that the majoriry self correct themselves, but some not and the current grow up to the sky...any light at the end of the tunnel?

Hi Mario,
If the part is made by TI marked either TL494C (a D or N package) or TL494 (an NS or PW package)
But a TL494C part will not fit on a TL494 pad.
You can check the packaging detail on the datasheet:
www.ti.com/.../tl494.pdf

The TL494 is one of the very first PWM controllers and there are many manufacturers of the "TL494".
I think the parts on your boards are not TI parts but are either some other manufacturers or a counterfeit.
The replacements parts are TI but the parts on the board are suspect.
Regards
John

Hi John

Both are package soic 16. Despite the operation temperature I did not see any difference. Why did you say TL494C part will not fit on a TL494 pad. In practice, all modules of this manufacturer came with TL494 and in all modules there is a same behavior: peak of current when stat up the module. I purchased two modules of different manufacturer . Both came with TL494 C and both worked. I replaced the tl494 by a tl494c in the module with strange bahavior, and it started working.

please see the pictures below.  TL494C works, TL494, which came with the module doesnot work. Perhaps the TL 494 can be conterfeit as you mentioned .

Hi John

Sorry to insist in asking you support. I ordered new TL494-C and replaced all from the 600 pcs I bought . Most of them are working properly, but I still have this peak of current when startup the module. I noticed a better behavior , howeverÇ

1- some modules still present the peak of current ,,but 100% return to the adjusted numbers

2- the module specs are shown below, the moduel was designed to work from 10VDC input on, but this peak occurs around 11,5VDC input.

Unfortunately I do not have the electric diagram to make a better analysis, so if anyone have it and could make it available, I would be thankfull.

【Operating temperature】: -40 ~ + 85 ℃ (Please strengthen

the heat when the ambient temperature is too high)

【Working frequency】: 150KHz

【 Conversion efficiency 】 : 96% high (efficiency and input, output voltage, current, pressure-related)

Over current protection: Yes (input over 13A, automatically reduce the output voltage, a range of errors.)

【Input reverse connection protection】: Yes, (less than 5A, if

you need more reverse current, please input string into the diode)

[Installation]: 4 3mm screw holes

【Wiring】: wiring output

【Module Size】: Length 70mm Width 36mm Height 13mm

【Single module】: 50 grams

Hi Mario,
The reason I think the parts are suspect is because the units came with a part marked TL494 which if a TI part would be an SO16 package (NS drawing in TI datasheet and part width of 7.8mm)
You fitted a part marked TL494C which is an SOIC16 package (D drawing in the TI datasheet and 6mm wide)
If both parts are genuine then one should be much narrower than the other.

Sorry but this is all I can suggest.
Regards
John

Hi John

I finaly decided to get the electric diagram by using reengineering way. I firstly removed the layer from the aluminium  and made a negative of the layout. As result i could re-draw the circuit. I measured the capacitor values and the diagram was finaly in hands. Analysing it and the documentation you recomended , I modified the soft start circuit, changing c10 to 10UF and R8 to 100k. The startup is very slow(around 0,5s) and the peak doesnot hapen anymore . As I am  using the module as source to led strings, I do not see any problem if the start up occurs  slowly. Do you see problem if I configura the soft start to around 0,5s instead the recomended 50-100 cycles of clock:? If not , my problem is solved. Please see the diagram below:

just for the people who are interested in having such diagram , follows the bom:
Location Value Case
C1 220uF 50V
C2 220uF 50V
C3 1uF
C4 220uF 50V
C5 220uF 50V
C6 1uF
C7 1uF
C8 100nF
C9 100nF
C10 1uF(recommended to increase it to improve soft start)
C11 Not Applicable
C12 100nF
C13 1nF
C14 100nF
C15 100nF
C16 100nF
C17 1nF
D1 SS54
D2 MBR20100CS
G1 NCE6075
L1 47uH
Q1 D884
Q2 Y1
Q3 Y2
R1 Not Applicable
R2 4K3
R3 15K
R4 Not Applicable
R5 1K5
R6 10K
R7 10K
R8 10K (recommended to increase it to improve soft start)
R9 10K
R10 22R
R11 1K
R12 4R7
R13 240K
R14 Not Applicable
R15 22R
R16 10K
R17 1K
R18 0R
R19 0R01
RV1 10K
RV2 5K
U1 TL494C
ZD1 WL