AN10881
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© NXP B.V. 2011. All rights reserved.
Application note
Rev. 2 — 26 September 2011
80 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
10.4.4 Dimensioning the timer function
The required restart time t
restart
determines the time constant t
RCPROT
made by the values
of R and C.
(38)
With this time constant and the required protection time t
protection
, the value of R and C can
be calculated as follows:
(39)
(40)
Example:
•
t
restart
= 500 ms
•
t
protection
= 30 ms
•
t
RCPROT
= 240 ms
•
R = 341 k
•
C = 705 nF
t
RCPROT
t
–
restart
1n
V
low RCPROT
V
high RCPROT
-----------------------------------
------------------------------------------------
t
–
restart
1n
0.5
4
-------
--------------------
0.48
t
restart
=
=
=
R
V
high RCPROT
I
slow RCPROT
1
e
t
protection
t
RCPROT
------------------------
–
–
-------------------------------------------------------------------------------
4
100
A
1
e
t
protection
t
RCPROT
------------------------
–
–
---------------------------------------------------------------
=
=
C
t
RCPROT
R
--------------------
=
