APPLICATION NOTE
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Figure 12: Static Line & Load Regulation
You can also configure measurement expressions to quickly and easily perform these measurements. To
measure maximum variation in output voltage, you can use the Swing_XRange measurement expression.
For this example, the expression should be Swing_XRange (V(out),20m,40m). You can also directly
calculate the regulation in percentage (%) by using
Swing_XRange(v(out),20m,40m)*100/YatLastX(avg(v(out))). Using this expression the calculated value
for load or line regulation comes out to be < 2%.
Switching Losses in MOSFETs
Estimation of accurate switch loss is a very crucial aspect of a successful VRM design. This directly
influences the reliability of power supply under various operating conditions, and also drives the heat
sinks selection and thermal design.
In hard switching topologies the switching losses are crucial factor and cannot be ignored. There is no
direct method to obtain these accurately from datasheets and losses are very sensitive to circuit
parameters and parasitic. You need to first understand the switching loss in MOSFET. Switching loss in
MOSFETs is due to simultaneous application of high voltage and high current through the device. As
shown in picture below, the MOSFET drain current has been building up while voltage across drain to
source is yet to drop, leading to a finite loss across the switch. Amount of switch loss can be estimated by
area enclosed by voltage and current (RED & BLUE) waveforms as shown in following diagram.
