Is it sufficient to use datasheet formulas to select SMPS component values?

[matrixofdynamism]

SMPS consists of a controller IC, switching element and diode (both of which might be present inside the controller IC) and some inductors and capacitors as energy storage elements and/or filter and some resistors. The resistors could be used to create some sort of analogue filter and might be used to create voltage divider to provide the feedback voltage to the controller IC.

Now, is it sufficient that we use the formulas and other data given in the datahseet to calculate the component values and then create the schematic, PCB layout and the final design for testing OR, is it also important to simulate the SMPS design in some sort of SPICE simulator tool?

 

[tepalia02]

It is important to simulate the SMPS design in a SPICE simulator tool to verify the performance of the design and ensure that it meets the desired specifications. While the datasheet may provide some guidance on component values and ratings, it may not take into account specific circuit layout and environmental factors that could affect the performance of the SMPS. Simulation can also help you optimize the design by testing different component values and configurations and evaluating the trade-offs between performance, cost, and size. This can help you achieve the best possible performance from your SMPS design.

In case you need suggestions on free online simulation software choices, you can take a look here:

https://www.theengineeringprojects....cuit-simulators-for-engineering-students.html

 

[KlausST]

Hi,

Now, is it sufficient that we use the formulas and other data given in the datahseet to calculate the component values and then create the schematic, PCB layout and the final design for testing OR, is it also important to simulate the SMPS design in some sort of SPICE simulator tool?

I didn´t expect this question.

The IC manufacturers want to sell their ICs. Thus they do all that the customers are satisfied.
--> Generally all important information is given in the datsheet to design the whole circuit.

Additionally the manufacturers provide application notes, design notes, example designs, software, simulation models...to ease the design.

It is important to simulate the SMPS design in a SPICE simulator tool

Honestly: I never did. I keep on the datasheet informations and get the expected result.

Klaus

 

[barry]

It is important to simulate the SMPS design in a SPICE simulator tool to verify the performance of the design and ensure that it meets the desired specifications. While the datasheet may provide some guidance on component values and ratings, it may not take into account specific circuit layout and environmental factors that could affect the performance of the SMPS. Simulation can also help you optimize the design by testing different component values and configurations and evaluating the trade-offs between performance, cost, and size. This can help you achieve the best possible performance from your SMPS design.

In case you need suggestions on free online simulation software choices, you can take a look here:

https://www.theengineeringprojects....cuit-simulators-for-engineering-students.html

I don't verify performance with a simulator; I verify performance by building the circuit. (That doesn't mean I don't do simulation).

Further, I don't think any of those simulators you linked to will simulate a complete circuit on a PCB or simulate environmental factors.

 

[crutschow]

Data sheets aren't always perfect.
I just simulated a Linear Technology (now Analog Devices) switching supply using their "test fixture" circuit provided with LTspice, which is similar to the data sheet circuit.
The simulation was stable but showed significant overshoot and ringing for a step load change with the recommended compensation components.
This was largely reduced by modification of one of the compensation values

So I think simulation can help improve the design and add confidence that the circuit will work as desired, but of course this must be verified with the real circuit.

 

[KlausST]

Hi,

But simulators aren't perfect either. Often they miss inductor saturation.
And usually they don't simulate PCB layout, but especially switch mode supplies are critical with PCB layout.

But simulators still are useful. Especially for newbies, they can play around, measure each voltage and current, while they don't cause smoke..

Klaus

 

[tepalia02]

Hi,

I didn´t expect this question.

The IC manufacturers want to sell their ICs. Thus they do all that the customers are satisfied.
--> Generally all important information is given in the datsheet to design the whole circuit.

Additionally the manufacturers provide application notes, design notes, example designs, software, simulation models...to ease the design.


Honestly: I never did. I keep on the datasheet informations and get the expected result.

Klaus

Thank you sir. So, what is the right approach to make an SMPS according to you? Making the PCB prototype directly?

 

[barry]

Thank you sir. So, what is the right approach to make an SMPS according to you? Making the PCB prototype directly?

All of the above. Read the data sheet. Read the app notes. Do simulations. Build a prototype.

You can't go from reading a datasheet to production in a single step.

 

[KlausST]

Hi,

I fully agree wuth Barry.
Reading the manufacturer instructions is essential.
Simulation or directly designing the PCB .. on your own taste.

Klaus

 

[crutschow]

But simulators aren't perfect either. Often they miss inductor saturation.

Nothings perfect, but Ltspice can show inductor saturation, if it is put in the inductor model.

And, of course, you can readily look at the inductor current to see what saturation current rating you need for the actual device, which may not always be apparent from just the calculations.