[SOLVED] Swiching Regulator PCB design

[amayilsamy]

I think to design switching regulator for 5V using MC34063 buck converter...




the given pcb dimensions 45 X 65 mm.

What is my doubt in this pcb .. Why it is make it as above dimensions?

Why we reduce PCB size?

If we reduce the PCB size what problem occurred in regulator?

 

[ec_nisarg]

pcb size you have mentioned seems optimum. why do you want to reduce it more?

 

[tpetar]

I think to design switching regulator for 5V using MC34063 buck converter...

View attachment 89481


the given pcb dimensions 45 X 65 mm.

What is my doubt in this pcb .. Why it is make it as above dimensions?

Why we reduce PCB size?

If we reduce the PCB size what problem occurred in regulator?

Size can be reduced, recently I make compact PCB in SMD for voltage boost from Li-Ion/Li-Po to 5V. If PCB is small you can put it into smaller devices.

There is no problems with smaller PCB size, only take in mind power dissipation for DIP and SO8 cases according to manufacturer datasheet, and provide additional copper square area to IC pins for better cooling.

 

[amayilsamy]

I need small size power supply. My product very small.

Power supply occupy more space. That's what I want reduce that..

 

[tpetar]

See my album for voltage boost, the same can be done for buck converter:



I place parts only on one side, second side I leave empty and that side is sticked to phone Li-Po battery, all is very thick and small. With usage of tantal capacitors and other side of PCB all can be even smaller.



What currrent needs and voltage are involved in your project?


Currently I making miniature 220V to 12V or 5V SMPS. It will be small as 30mm x 30mm.

 

[ec_nisarg]

Size can be reduced, recently I make compact PCB in SMD for voltage boost from Li-Ion/Li-Po to 5V. If PCB is small you can put it into smaller devices.

There is no problems with smaller PCB size, only take in mind power dissipation for DIP and SO8 cases according to manufacturer datasheet, and provide additional copper square area to IC pins for better cooling.

also we have to calculate track width for ampere capacity.

 

[amayilsamy]

Here I pasted bottom side of that PCB this from ONSEMI mc34063 datasaheet.

There is no ground fill.

 

[tpetar]

Its no problem with track, you need to use external transistor-MOSfet for that current, because 34063 IC supports max up to 1,5A in any conditions. For 1A output current, you will have more then 1,5A in peaks. Also efficiency is very important, specially if you use battery for power source.

What input and output voltage you need?

- - - Updated - - -

Here I pasted bottom side of that PCB this from ONSEMI mc34063 datasaheet.

There is no ground fill.

View attachment 89491

What you mean under ground fill?

 

[ec_nisarg]

does we need external mosfet at all?

 

[tpetar]

does we need external mosfet at all?

If 34063 have Ipk (peak current) higher then 1,5A (1,5A maximum allowed), then you should use external transistor-MosFET.

Will be useful to read 34063 datasheet.

 

[ec_nisarg]

See my album for voltage boost, the same can be done for buck converter:



I place parts only on one side, second side I leave empty and that side is sticked to phone Li-Po battery, all is very thick and small. With usage of tantal capacitors and other side of PCB all can be even smaller.



What currrent needs and voltage are involved in your project?


Currently I making miniature 220V to 12V or 5V SMPS. It will be small as 30mm x 30mm.

can you tell me about this project? sorry for side tracking, but this seems something useful to me.

 

[tpetar]

Nothing special, I post PCB in my album, I make this for voltage boost from Li-based battery to 5V. This also can be made for step down regulation, and can be even smaller. That variant with charger MCP73832 and MC34063 have around 7mm in heigh, and all can have lower profile with Tantal capacitors. I made this for one night from parts what I have in my home stock, I save Tantals for other projects. :smile:

I will make step down on 15mm x 23mm, parts on both side, and with Tantal capacitors. I start designing PCB, but some other project take priority.

 

[amayilsamy]

My I/P Voltage= 12 V (max) to 6.5 V (min) From SMPS and Battery.

O/P Voltage = 5 V @ 600 mA (max)

In the MC34063 datasheet Step down Converter typical application circuit there is no external switch.

I think for 600 mA current its no need external switch.

How to we make a smaller size PCB for the above design?

 

[ec_nisarg]

as tpetar suggested use SMD device. also use SMD resistors, you can reduce the size of your pcb.

also why don't you use just 7805, its simple and can source up-to 1A.
does your system need critical voltage?

 

[tpetar]

Yes current in peak is about 1,2A and you dont need external switching for your parameters.

 

[amayilsamy]

I need avoid heat from the power supply.

And its also more quiescent current like near 8 mA.

So, I can't use Linear regulator.

That what I'm choosing switching regulator?

 

[tpetar]

You will not have heat. Quiescent current can be around 4,2mA. Select good 220uH inductor with enough current support.

 

[amayilsamy]

7805 total power dissipation around 4.2 W.

Its switched on all days in a year.

This is in a Plastic box. That what I'm avoiding heat sink.

 

[tpetar]

Its no problem to linear regulator to run long time and to be hot, its normal for linear, and its not problem to run this type of regulator in plastic box. Adequate heatsink is needed for cooling regulator and there is no problems. One problem can be in power loss if power source is battery. In any case 34063 IC will not generate heat like linear regulator.
I use often linear 78M05 and 7805 in SMD and I dont have problems with that, for heatsink I use copper on PCB (SMD parts), when I need power saving I use switching tech.

 

[FvM]

I need avoid heat from the power supply.

And its also more quiescent current like near 8 mA.

So, I can't use Linear regulator.

That what I'm choosing switching regulator

O.K., so what's the remaining problem? You can use 34063 or another suitable switching regulator, you can reduce the PCB size.

Other switchers are probably smaller and offer higher efficiency, but are more expensive. 34063 is still one of the cheapest switching regulators, you shouldn't expect mind blowing performance.