This design calculator tool is intended to help design engineers to speed up their decision making in selecting the right parts for buck converter during the design phase. This is made in excel so that all engineers or any user have access into it. The calculator is simple to understand as it has detailed notes on each line item.

This design calculator is for a non-synchronous buck converter. Non-synchronous means a combination of a switch and a diode. This is a conventional buck converter. The switch used in the calculator is a power MOSFET.

Sample Buck Converter Design Using Excel Calculator

Design Given:

Input voltage (Vin) = 24V, Output voltage (Vout) = 12V, Output current (Iout) = 10A, Switching frequency (Fsw) = 100 kHz

All the information above are inputted to the calculator. There is an assumption in the level of the voltage spike that caused by parasitic inductance and capacitance. This is useful in the sizing of the MOSFET in terms of voltage rating.

The next part of the calculator is Parameter Sizing. There are two input fields in this section. First is the %ripple allowance. The intention of this is to select an initial inductance value. The second one is the actual inductance value that the user will use. The rests are all calculated values wherein the duty cycle, the inductor currents, the MOSFET currents and voltage and the diode currents and voltage are displayed.

The next part of the calculator is the Power Losses. In this section, the user will supply the information in green field in order to get the power losses of each component. These values are provided in the datasheet. These are the only part in this template that require little effort but not really difficult since all these are provided by the component manufacturer.

The last section of this calculator is the Efficiency estimation. This is an estimation because the result of the calculation depends on the values provided above by the user. The more the values are near accurate, the calculated efficiency will also be near accurate.

Verify the Result Using a Separate Mathcad Calculation

The design calculator result above is verified using a separate calculation in Mathcad. Below is a screen shoot of the portion of the derivations made in Mathcad. The resulting equation of the duty cycle is Vout / Vin. The output and input voltage of the sample design above are 12V and 24V respectively. This will give a duty cycle of 0.5 or 50%.

The inductor ripple current value in a separate Mathcad calculation also coincides with the excel calculator above.

The inductor RMS and peak current are also matching between the two methods.

The calculated current values for MOSFET are also the same between the excel calculator and Mathcad.

Lastly, the computed values for the diode are also matching for both methods.

This design template is derived carefully and checked through other means like simulations and separate derivations using Mathcad. Actual past projects are also designed using this calculator.

After downloading this Buck Converter Design Using Excel Calculator and have trouble understanding, contact [email protected].

If you are interested to learn more details about how to design buck converter, read Buck Converter Design Tutorial.

There is another design template for buck converter design but in Mathcad format. It can be used for external switch and diode or switches for synchronous operations.

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