A boost converter (shown in figure 1) is simply is a particular type of power converter with an output DC voltage greater than the input DC voltage. This circuit is used to ‘step-up’ a source voltage to a higher, regulated voltage, allowing one power supply to provide different driving voltages.
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| Figure 1 |
The key principle that drives a boost converter is the tendency of an inductor to resist change in the current.
Boost Converter operates in two in two modes, continuous and discontinuous mode. In discontinuous mode, the amount of energy required by the load is too small. Therefore, the current through the inductor falls to zero during that period.
In continuous mode, the current through the inductor never falls to zero.
- When the switch is open (shown in figure 2) the stored energy is transferred through the inductor to the voltage output in a controlled manner through the flyback diode D, the capacitor C and the load R
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| Figure 2 |
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| Eq. 1 |
- When the switch is closed (figure 3), current flows through the inductor in clockwise direction and the inductor stores the energy magnetically.
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| Figure 3 |
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| Eq. 2 |
The inductor current has to be the same at the start and end of the commutation cycle. This means the overall change in the current is zero.
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| Eq. 3 |
Using the voltage and current ripple, the value of Inductance and Capacitor values are calculated.
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