1

3

1 +

x

2

D =

D =

LM2830

www.ti.com

SNVS454D – AUGUST 2006 – REVISED APRIL 2013

Conduction losses usually dominate at higher output loads, whereas switching losses remain relatively fixed and

dominate at lower output loads. The first step in determining the losses is to calculate the duty cycle (D):

(16)

(17)

becomes:

(18)

The conduction losses in the free-wheeling Schottky diode are calculated as follows:

(19)

Often this is the single most significant power loss in the circuit. Care should be taken to choose a Schottky

diode that has a low forward voltage drop.

Another significant external power loss is the conduction loss in the output inductor. The equation can be

simplified to:

DCR

(20)

The LM2830 conduction loss is mainly associated with the internal PFET:

(21)

If the inductor ripple current is fairly small, the conduction losses can be simplified to:

(22)

Switching losses are also associated with the internal PFET. They occur during the switch on and off transition

periods, where voltages and currents overlap resulting in power loss. The simplest means to determine this loss

is to empirically measuring the rise and fall times (10% to 90%) of the switch at the switch node.

Switching Power Loss is calculated as follows:

(23)

(24)

(25)

Another loss is the power required for operation of the internal circuitry:

(26)

Copyright © 2006–2013, Texas Instruments Incorporated

Submit Documentation Feedback

13

Product Folder Links: LM2830