230vAC - 12vdc problems?

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dannix

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Hi,

I am trying to get 12vdc from mains voltage.

I have the following setup using these components:

Transformer: dual 115v pri, dual 15v sec 300va **broken link removed**


Rectifier: **broken link removed**

i seriesed the primary for 230v mains each sec winding into a 35A rectifier and the dc paralleled then into a capacitor network of 8x 4700mf caps(35v) to a commercial dc-dc converter **broken link removed**

however I am reading 22v dc output not the expected 15vdc or thereabouts, when I put this into the dc-dc convertor that can take a 24v input max it does not work, when i turn the ac off as the caps discharge the dc-dc convertor finally fires up for a few seconds.

If I removed the cap network and just put the dc straight into the dc-dc convertor I again get nothing?

If I put a battery into the dc-dc convertor it works fine.

Where am I going wrong?


Cheers all
 
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Why have you paralled the transformer AFTER rectification? It is usual to parallel the transformer secondaries before the rectifier.. Make sure they are in phase, or you will let the magic fairy smoke get out!!!

The 22v you are getting from the rectifier is spot on for a 15v transformer..
1.414 x 15v = 21.21V, allowing for transformer tolerance, 22v is correct.
 
Hi, I paralleled after as per this design: **broken link removed**

So long as negative ar together and positive are together should not matter? If the voltage is correct it still does not explain why it does not supply the DC-DC convertor that takes 8-24vdc for 12vdc out.

For simplicity I just used one winding and same result.
 
dannix said:
so a sec 9vac transformer would be the suitable choice
Click to expand...
Try to use 4*47000uF instead of 8. Perhaps the Microcontroller in the dc - dc converter may not be coping up with the slow raise due to large cap effect.
 
I tried it with no smoothing caps, when I checked the terminal input voltage of the regulator the voltage was still 21-22v, so the onboard caps must be back feeding and smoothing voltage to almost peak as above, this would seem to be too much for the reguator so its not starting up, when you turn the ac off and measure the voltage as soon as its 16v the regulator fires up for a few sec's till it drops to 8v, I think the rectified AC voltage is too high.

If it was 9vac peak is 12.6. if it is 12vac peak is 16.8, so I think i need a 9vac sec transformer, I wish I had a scope to see more.
 
You are right
the voltage is crossing the high limit and coming back to 22V.
For observation sake, keep a 47 ohm resistor as dummy load across the 22v input to the converter with proper mounting.
 
dannix said:
do you mean the output of the regulator? there would never normally be a load on the input?
Click to expand...

No Dannix. At the regulator input. this help us to ensure that a momentary high voltage will not disable the entire system.

May be there is a provision for trimming the high voltage sense. try to turn it upwards, in case available.

try monitoring the unregulated voltage, and see at what voltage the system is getting just started.

If your DMM has a peak measurement switch, you may use it to know what peak voltage is building up before settling to 22V.
 

Paralleling after Bridge helps share the load by both bridges perhaps.


BTW, A bus/ train station may also be where from a bus/train Starts. now the logic works
 
I will try with a dummy load mvs, not sure if this will make any difference but I also tried to supply the dc regulator with the rectified voltage through a PWM circuit, to no avail.
 
dannix said:
I will try with a dummy load mvs, not sure if this will make any difference but I also tried to supply the dc regulator with the rectified voltage through a PWM circuit, to no avail.
Click to expand...

Please confirm that part of the first link is used for rectification and the device available in second linkis what you have used for DC-Dc conversion.

**broken link removed**

**broken link removed**

If possible try to indicate the chip used for DEC to DC conversion in the above design and also the Micro used therein.

You said that you gave used a PWM circuit, before connecting to converter. Can you upload the schamatic of the PWM indicated b you.
 
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dannix said:
I will try with a dummy load mvs, not sure if this will make any difference but I also tried to supply the dc regulator with the rectified voltage through a PWM circuit, to no avail.
Click to expand...

Please confirm that part of the first link is used for rectification and the device available in second linkis what you have used for DC-Dc conversion.

**broken link removed**

**broken link removed**

If possible try to indicate the chip used for DEC to DC conversion in the above design and also the Micro used therein.

You said that you gave used a PWM circuit, before connecting to converter. Can you upload the schematic of the PWM indicated b you.


By the way, an extract of the spec from link1 above is attached. we are to see the meaning if input at full load. item 1 there in appears ultimate limits, thereby it should work. However, you may check whether the caps you are using or not doing the job well and the ripple is more?

DSX12VD Overview:
Specifications:
Input Voltage (Operating) 6-24 Volts Non-Regulated
Input Voltage (Full Load) 8-16 Volts Non-Regulated
Input Current 15 Amps Max
Output Power 140 Watts Max
No Load Operating Current < 70mA
Sleep Current (All Rails Off) < 4mA
Efficiency > 95%
 
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mvs sarma said:
Please confirm that part of the first link is used for rectification and the device available in second linkis what you have used for DC-Dc conversion.

**broken link removed**

**broken link removed**
Click to expand...

Correct, however only used the first part for rectification in the schematic on that site upto the 40,000mF Caps the regulator etc was not required as the DC-DC convertor should do it.

If possible try to indicate the chip used for DEC to DC conversion in the above design and also the Micro used therein.
Click to expand...
Unsure what it is

You said that you gave used a PWM circuit, before connecting to converter. Can you upload the schematic of the PWM indicated b you.
Click to expand...

**broken link removed**
By: http://www.cpemma.co.uk


yea I was aware of them so it should work, but it only fires up at about 16-17v when the caps are discharging. It is designed for a car with nominal 13v ish maybe it can not handle prolonged high voltage. All testing been under no load.

Im not sure what I can do except try a smaller sec transformer output, tied with smoothing, without smoothing and PWM, I need a scope.
 
muhammad Azhar said:
Hello
I need 12vdc to 220vac Invortor Diagramme & all detail
Click to expand...

Then can I suggest you create your own thread with information spacific to your needs with a schematic of what you have so far so that people can help you.
 
muhammad Azhar said:
Hello
I need 12vdc to 220vac Invortor Diagramme & all detail
Click to expand...
Azhar bhai, please do create a new post so that your post would be handled independently.
Please go to section see at the top a button for new post.
 

Dannix, what all you are suffering is the behavior of the DC-DC converter and its specification.

Input Voltage (Operating) 6-24 Volts Non-Regulated
Input Voltage (Full Load) 8-16 Volts Non-Regulated
the first part is not clear. we have to analyze.

I was asking in the second part of my query, "If possible try to indicate the chip used for DC to DC converter you referred"

Please first try to reduce the voltage to 16V or 15.5 and let us see that it works there. I suggest a simple way. Try connecting the primaries in series and let it be ready for 230V. (Here you need to take care of connecting end of one winding to start of second. otherwise, it won,t work.). Now we will only supply 110V at the 230V primary. at the secondary you expect only 7.5V
The DC voltage would now be less. perhaps it will be 1,414 times 7.5V(minus two diode drops when you load it.) perhaps 11 0r 12V just.
As you have this equipment with you, perhaps you may have a schematic of the same. Is there a provision to adjust high voltage sense signal which may be causing this behavior. If so whether we can slightly adjust it ?





please try and let us see Dannix.
 
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