Component Layout of SMPS Design

[codex653]

ok so tomorrow is Christmas everybody!! anyone excited?! It's Jesus's birthday! wooo! hahaha

anyways on to my question

so tomorrow i will be getting the parts (finally) for the 2 SMPS offline converters that i am making for my amp. 1 Buck Converter and 1 Buck-Boost Converter...both of them will have an average current draw of around 3-5A with a peak of about 8A...the switching frequency is going to be between 80-100Khz.

now this is my first time building any circuit that can have alot of EMI coming from it, so i'm not so sure about the "rules" when it comes to component layout design...i know that where you place the components is pretty critical so that you don't cause oscillations or many other problems, but as for HOW to lay them out i become a bit confused...

 

[crutschow]

Don't the data sheets for the converters show a suggested layout?

 

[codex653]

haha dude this is a discrete smps there is no datasheet lol

heres the "schematic" for the buck and buck boost converters...i just want to know if there is a certain way i should lay out the components...i've already worked out the values for each component, and i was just gonna lay the parts on the board just kinda like how it shows in the schematic..atleast for the power portion of it...the gate drive chip and all that will be in its own little section of the board.

https://www.electro-tech-online.com/custompdfs/2010/12/slyt286.pdf

 

[crutschow]

So, "dude", why would you not use an IC for the PWM modulator? It's a lot easier than rolling your own, and you are much more likely to end up with a circuit that works.

What type of PMW modulator circuit are you using?

As far as the layout, one important thing is to keep all the devices that carry high currents as close together as possible including the power transistors, the inductors, and the capacitors. You also should have a ground plane for all the common connections. Here's a layout guide that should be helpful.

 

[codex653]

crap, another thing i should have clarified...i reallly must have lost my mind when i posted all of this my bad man...the pwm is in an IC,specifically the 555 timer, and despite what other people have said, i was talking to an electrical engineer friend of mine and with some math he did he found out that the 555 timer puts out more than enough current and voltage to drive the gate of the mosfet for my circuit..it's only gonna take like 6mA..way less than the 200 mA that the 555 can supply i know it's not gonna give the absolute best switching times, but that's not what i'm worried about right now.

OH WOW! that looks like a GREAT article you have there! thanks!! i'm gonna go read that like right now)