Switched-Inductor Boost Converter (LTspice Simulation)

1 year ago

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Open source license: Public Domain

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Description

(Please find the LTspice simulation .asc file in the doccuments section.) A switched-inductor type boost converter has multiple inductors that are charged in parallel but discharged in series, thereby putting multiple boost inductors in series to the input power supply. The two diodes above and below the inductors enable parallel charging of the inductors when the MOSFET is on and the two diodes in series with the inductors put them in series to the input when the MOSFET is off. This results in an increased "boost" for the same duty cycle compared to a single inductor type boost converter.

The output voltage of a boost converter is given by the formula

                    Vo = Vin*n/(1 - D)

This circuit runs at a duty cycle of 65% and outputs 48V. A normal boost converter with an efficiency of 90% would output

            Vo = 12*0.9/(1-0.65) = 30.85V

The output voltage of a two-inductor switched boost converter for the same duty cycle is

                 Vo = Vin*n*(1+D)/(1-D)

Substituting the appropriate values,

       Vo = 12 *0.9*(1+0.65)/(1-0.65) = 50V

This circuit, in reality, outputs 48V with an efficiency of 92% (for a load current of 1A).

Screenshot 48.pngScreenshot 39.png

Output voltage ripple

Screenshot 40.pngScreenshot 41.png

PWM signal Screenshot 42.pngScreenshot 43.png

Error voltage vs ramp Screenshot 44.png

Diode current waveforms Screenshot 45.png

Inductor and MOSFET voltages Screenshot 46.png

Efficiecy and power losses Screenshot 47.png

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