Input protection setting for DC-DC converter

Thread Starter

Hasan2019

Joined Sep 5, 2019
62
Hi there,

This post is very easy one for you who know better.
:-//

I am confused to set some values.
My DC-DC conveters input is 250-650VDC and output is 24V/5A. Its use for PV battery charger.
Take a look here,


TI_1.PNG

I have few more query,

1. My boss want me to put some common ground ZNR” Transient/Surge Absorbers, in folloing manner, https://www.farnell.com/datasheets/2244565.pdf

2. Dont think he needs it unnecessary for protection since there is 2 cap, 1 noise suppreser and rersistors are available.

3. He wants to add a fuse in pin 1 to R24, not sure why?

4 Can you imagine any idea to use R1-3? Those are 1 Mohms.

6. He wants to add a LED indecator for power output, for 5A current whats your idea?
 

MisterBill2

Joined Jan 23, 2018
11,579
What sort of surges are anticipated on the output of a solar-cell array? Lightning comes to mind and at that point I suggest suitable lightning protection hardware. Lightning protection is a mature field and the suppliers of such hardware can provide much better application information.
Fuses on both input pins 1 and 4 will be appropriate to protect external wiring when components inside the converter fail.
 

Papabravo

Joined Feb 24, 2006
18,073
Component selection, should involve specific requirements, which appear to be lacking. Throwing components without reason on a schematic is likely to result in disappointment. The requirements are essential so that you can tell what "DONE" means.

Q: Is L1 a common mode choke or a differential mode choke? Demanding applications could require one of each kind in series.

I too am puzzled by R1, R2, & R3, they do not appear to have a useful purpose.
 

MisterBill2

Joined Jan 23, 2018
11,579
I am also puzzled by D4 and D5, opposite connected in series with R23. The symbols do not indicate either is a zener or other reverse breakdown device. The 3 resistors? Discharge the cap eventually. 63 mFD @700 volts is a bit uncommon. Perhaps it is two 350 volt caps in series.
The bifilar choke is to keep inverter noise out of the solar cell wires, to avoid RFI radiation. And I am not at all comfortable with "ground" on one of the leads like shown.
And really, solar cells do not produce spikes. Lightning is a different case.And rooftop solar arrays might get lightning, hence the second reason for input fuses in both lines. And they will need to be higher voltage fuses, not the 250 volt little glass ones.
 

Thread Starter

Hasan2019

Joined Sep 5, 2019
62
I am also puzzled by D4 and D5, opposite connected in series with R23. The symbols do not indicate either is a zener or other reverse breakdown device. The 3 resistors? Discharge the cap eventually. 63 mFD @700 volts is a bit uncommon. Perhaps it is two 350 volt caps in series.
The bifilar choke is to keep inverter noise out of the solar cell wires, to avoid RFI radiation. And I am not at all comfortable with "ground" on one of the leads like shown.
And really, solar cells do not produce spikes. Lightning is a different case.And rooftop solar arrays might get lightning, hence the second reason for input fuses in both lines. And they will need to be higher voltage fuses, not the 250 volt little glass ones.
Can you mention high voltage relay range? It is still needed to keep D4 and D5 since they are used to absorb VDS spike during MOSFET switching.
 

MisterBill2

Joined Jan 23, 2018
11,579
Can you mention high voltage relay range? It is still needed to keep D4 and D5 since they are used to absorb VDS spike during MOSFET switching.
I see no MOSFET in the drawing supplied, nor indication of MOSFET presence.
The "ground" connection immediately after the dual input choke does not seem like a good idea.
As for surge suppression, where would surges come from in a solar cell array? That is a puzzle indeed. Solar arrays tend to not have instant response, although nearby lightning strikes can induce high voltages. So perhaps, for lightning protection, some high voltage protection would be in order. But Zener diode protection for a high voltage circuit does not seem reasonable.
AND, fusing the ground lead of a protective device R24 is nonsense.
What does make some sense is fusing both lines from the solar array at the entrance point to this assembly.
 

MisterBill2

Joined Jan 23, 2018
11,579
Adding an LED to indicate at least 5 amps pf battery charging current is a reasonable concept. But ince we see none of that portion of the circuit there is no way to offer a reasonable suggestion a to how that may best be done.
 
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