Introduction to Digital Power Conversion
XMC4000/1000 Family
Comparison of Power Conversion Methods
Application Guide
10
V1.0, 2015-01
Switch Mode Power Conversion Principle
– Compared to Linear Mode
In switch mode voltage conversion, portions of energy, divided by switching in time lengths (T
1
or T
2
),
are transferred from a voltage source to an inductor (L) current as magnetic energy, cyclic in periods
(T). During the rest of each period (T), the energy is moved into a capacitor (C), for the output voltage.
This principle is true for any DC/DC converter topology.
Interesting similarities with linear conversion can be seen in the output/input voltage ratios, when
replacing ‘R’ with ‘T’. This comparison is true as long as the magnetic energy of the inductor is never
emptied before the end of each period (T); i.e. Continuous Conduction Mode (CCM) is assumed.
Figure 3
Power Conversion Principles and Similarities - Demo Model
Power Loss Comparison
The voltage drop (V
1
–
V
2
) in linear mode is maintained by a resistor (R) and constant current, causing
active power loss.
The voltage (V
1
–
V
2
) in switch mode is reactive
by self-inductance (L) during rising or falling current in
the switch time intervals (T
1
or T
2
) respectively, resulting (ideally) in no power loss.
