NXP Semiconductors AN10881, Примечание к применению

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AN10881 All information provided in this document is subject to legal disclaimers. © NXP B.V. 2011. All rights reserved.
Application note Rev. 2 — 26 September 2011 28 of 102
NXP Semiconductors
AN10881
TEA1713 resonant power supply control IC with PFC
Example:
I
SUPIC(maximum measured)
= 18 mA
I
SUPREG(for IC circuits)
= I
SUPIC(maximum measured)
= 18 mA
I
SUPREG(for externals)
= 40 mA

I
SUPREG(for IC circuits)
= 40 mA

18 mA = 22 mA
Remark: SUPREG must remain above the undervoltage protection level of 10.3 V to
maintain full functionality. During start-up, high external current loads can lead to
problems.
5.6 Value of the capacitors on SUPIC, SUPREG and SUPHS
Some practical examples are provided in Section 12 .
5.6.1
Value of the capacitor on SUPIC
5.6.1.1 General
Use two types of capacitors on SUPIC. An SMD ceramic type with a smaller value located
close to the IC and an electrolytic type with the major part of the capacitance.
5.6.1.2 Start-up
When the supply is initially provided by an HV source, before being handled by an
auxiliary winding, a larger capacitor is needed. The capacitor value must be large enough
to handle the start-up before the auxiliary winding takes over the supply of SUPIC.
Example:
•
I
SUPIC(start-up)
= 10 mA
•

V
SUPIC(start-up)
= 22 V

15 V = 7 V
•

t
Vaux>15V
= 70 ms
(3)
5.6.1.3 Normal operation
The main purpose of the capacitors on SUPIC for normal operation is to keep the current
load variations (e.g. gate drive currents) local.
5.6.1.4 Burst mode operation
When Burst mode operation is applied, the supply construction often uses an auxiliary
winding and start-up from an HV source. While in Burst mode there is a long period during
which the auxiliary winding is not able to charge the SUPIC because there is no HBC
switching (time between two bursts). Therefore, the capacitor value on SUPIC must be
large enough to keep the voltage above 15 V to prevent activating the SUPIC
undervoltage stop level.
C
SUPIC
I
SUPIC start - up
 

t
Vaux 15 V


V
SUPIC start - up
 

------------------------------------------

10 mA
70 ms
7 V
---------------

100

F = =