STD150NH02L View Datasheet(PDF) - STMicroelectronics

Part Name

Description

Manufacturer

STD150NH02L

N-channel 24V - 0.003Ω- 150A - ClipPAK™ - IPAK STripFET™ IlI Power MOSFET

STMicroelectronics 

STD150NH02L

Buck converter - power losses estimation

Appendix A Buck converter - power losses estimation

Figure 18. Buck converter: power losses estimation

The power losses associated with the FETs in a synchronous buck converter can be

estimated using the equations shown in the table below. The formulas give a good

approximation, for the sake of performance comparison, of how different pairs of devices

affect the converter efficiency. However a very important parameter, the working

temperature, is not considered. The real device behavior is really dependent on how the

heat generated inside the devices is removed to allow for a safer working junction

temperature.

● The low side (SW2) device requires:

● Very low RDS(on) to reduce conduction losses

● Small Qgls to reduce the gate charge losses

● Small Coss to reduce losses due to output capacitance

● Small Qrr to reduce losses on SW1 during its turn-on

● The Cgd/Cgs ratio lower than Vth/Vgg ratio especially with low drain to source

● voltage to avoid the cross conduction phenomenon;

● The high side (SW1) device requires:

● Small Rg and Ls to allow higher gate current peak and to limit the voltage feedback on

the gate

● Small Qg to have a faster commutation and to reduce gate charge losses

● Low RDS(on) to reduce the conduction losses.

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