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VB409 / VB409SP

1

AVERAGE POWER CALCULATION IN WORST

CASE

As before explained, the device also senses the

capacitor reaches its maximum voltage, the

trilinton reduces the current so limiting furtherly

power dissipation. On the contrary if the capacitor

doesn’t reach the maximum value, the trilinton

whole conduction angle. This is obviously the

worst

case,

in

which

the

average

power

dissipation is maximum.

t

Assuming that

are the conduction angles, it results:

As for t1:

it follows:

Where

0

t1

[,

]

t2 T

2

---

[, ]

=

1

T

--

⋅

() t

d

0

T

=

=

1

T

--

()

⋅

() t

d

0

t1

∫

()

⋅

() t

d

t2

T

2

--

∫

+

⋅

()

⋅

T

---------------------------

2

π

T

⋅

()

sin

t

d

0

t1

∫

2

π

T

⋅

()

sin

t

d

t2

T

2

---

∫

+

⋅

==

()

⋅

T

---------------------------

2

2

π

T

⋅

()

sin

t

d

0

t1

∫

⋅

=

2

()

⋅

T

---------------------------

T

2

π

-----

2

π

T

⋅

()

cos

–

0

cos

+

[]

⋅⋅

=

=

=

()

⋅

π

2

π

T

⋅

()

sin

2

–

–

()

⋅

π

---------------------------

11

----------





2

–

–

⋅

----------

2

π

T

⋅

()

sin

=

0

t1

t2

T/2

T

t

2

π

T

⋅

()

sin

⋅







=

0

t

T

2

---

≤≤

T

2

---

tT

≤≤

0

()

⋅







=

0

tt1

≤≤

t2

t

T

2

--

≤≤

0

elsewhere

1

R1

R2

--------

+

()

⋅

=

=

Figure 3a

Figure 3b

t