If Psync is the wasted power on the input capacitor with synchronized PWMs, given by :

Psync = ESR

and Pmulti is the wasted power with multiphased PWMs, given by :

Pmulti = ESR

the power saved using the multiphase instead of the synchronized method for various duty cycle is :

Psaved (

Psaved

(δ) =











ESR

2

if

δ

ESR

2

)

if

For example considering an input capacitor ESR of 0.1 Ohm and an output current of 7A the power

saved using the multiphase instead of the synchronized method for different duty cycle is shown in fig.8.

0

0.1

0.2

0.3

0.4

0.5

0.6

0.7

0.8

0.9

1

0

0.5

1

1.5

2

Psaved (

δ)

Psync

Pmulti

δ

[W]

Psaved

Psync

Pmulti

(

δ)

(

δ)

Figure 8. Power saved using the multiphase instead of the synchronized method for various

duty cycle.

ESR=60m

Ω

Iout=7A

Iout=10A

Iout=5A

Vin=12V

3

3.5

4

4.5

5

5.5

6

6.5

7

7.5

8

0

0.5

1

1.5

2

Vout [ V ]

Psaved

[W]

[W]

ESR=50m

Ω

ESR=75m

Ω

ESR=100m

Ω

Vin=12V

Iout=7A

Psaved

33.544.555.566.5

7

7.5

8

0

0.5

1

1.5

2

Vout [ V ]

Figure 9. Power saved vs. Vout

AN1126 APPLICATION NOTE

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