FIP4F8S datasheet(31/33 Pages) FUJI

31 / 33 page

AN-087E Rev.1.0

April-2011

FA5526/5527/5528/5536/5537/5538

Fuji Electric Co., Ltd.

http://www.fujielectric.co.jp/products/semiconductor/

(12) Loss calculation

IC loss shall be determined to use the IC within its rating.

Since it is hard to directly measure IC loss, an example of

calculating approximate IC loss is given below.

Total IC loss, Pd, is obtained by the following equation:

Pd = Vcc * ( Iccop1 + Qg * f ) + VVH * IHrun

Where Vcc is the supply voltage to the IC, Iccop1 is

consumption current of the IC, Qg is total gate charge of

the MOSFET, f is switching frequency, VVH is VH pin

voltage and IHrun is a current flowing into the VH pin when

the IC operates.

This equation gives an approximate value of Pd, which

is a little greater than the actual loss. Take into

consideration variation and temperature characteristics of

each value

(Example)

When the VH pin is connected to half-wave rectification

waveform at power supply of 264Vac, the average VH pin

voltage is approximately 119V.

Under above condition, let us suppose Vcc = 18V and

Qg = 80nC at Tj = 25 degree.

When using FA5528 or FA5538, according to the

specifications IHrun = 25uA = 0.025mA ( typ. ), Iccop1 =

1.4mA ( typ. ) and f = 60kHz = 0.06MHz ( typ.).

Thus, typical IC loss Pd:

Pd = 18V * ( 1.4mA + 80nC * 0.06MHz ) + 119V * 0.025mA

= 115mW ( typ. )

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