Rev. 1.6

2/2010

Page 13 of 19

V•I CHIP INC. (A VICOR COMPANY) 25 FRONTAGE RD. ANDOVER, MA 01810 800-735-6200

vicorpower.com

PRELIMINARY DATASHEET

VMB0004MFJ - VMB0004MFT

3.0 POWER, VOLTAGE, EFFICIENCY RELATIONSHIPS

Because of the high frequency, fully resonant SAC topology,

power dissipation and overall conversion efficiency of BCM

converters can be estimated as shown below.

Key relationships to be considered are the following:

1. Transfer Function

a. No load condition

Eq. 1

Where K (transformer turns ratio) is constant

for each part number

b. Loaded condition

Eq. 2

2. Dissipated Power

The two main terms of power losses in the

BCM module are:

used to power up the module with an enabled power

train at no load.

the BCM modeled as pure resistive impedance.

OUT

Eq. 3

~

Therefore, with reference to the diagram shown in Figure 16

OUT

Eq. 4

INPUT

POWER

OUTPUT

POWER

OUT

Figure 16 – Power transfer diagram

The above relations can be combined to calculate the overall module efficiency:

η =

=

OUT

=

=1 –

Eq. 5