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© 2022 ROHM Co., Ltd.
65UG028E Rev.001
2022.7
User's Guide
BD7F105EFJ-EVK-001
Figure 37. L_COMP voltage compensation example
Application Design Examples-continued
8.2
Setting Disable Voltage
Disable voltage V
IN_DISABLE
when the VIN pin voltage falls can be set by the following equation.
𝑉
𝐼𝑁_𝐷𝐼𝑆𝐴𝐵𝐿𝐸
= 𝑉
𝐸𝑁2
×
𝑅
1
+ (𝑅
2
//𝑅
𝑆𝐷𝑋/𝐸𝑁
)
𝑅
2
//𝑅
𝑆𝐷𝑋/𝐸𝑁
𝑉
𝐼𝑁_𝐷𝐼𝑆𝐴𝐵𝐿𝐸
: Intended operation stop VIN voltage
𝑉
𝐸𝑁2
: Enable volt2
9
Output voltage compensation function using L_COMP pin resistor
The IC can compensate for the voltage drop in the output voltage V
OUT
in response to the increase in I
P
of the primary
transformer peak current.
V
OUT
changes can be caused by V
F
variations in the secondary diodes or by leaking magnetic fluxes in the transformer.
An example of the output voltage compensation function is shown in Figure 35.
This function compensates the output voltage by adding a I
REFCOMP
current to the REF current that determines the
output voltage.
𝑉
𝑂𝑈𝑇
= 𝑅
𝐹𝐵
×
𝑁
𝑆
𝑁
𝑃
× (
𝑉
𝐼𝑁𝑇𝑅𝐸𝐹
𝑅
𝑅𝐸𝐹
+ 𝐼
𝑅𝐸𝐹𝐶𝑂𝑀𝑃
) − 𝑉
𝐹
𝑉
𝐼𝑁𝑇𝑅𝐸𝐹
𝑅
𝑅𝐸𝐹
= 200 𝜇𝐴 (𝑇𝑦𝑝)
Fixed value. I
REFCOMP
is incremented relative to the primary current.
As a result, the output voltage is compensated according to the load current on the secondary side.
I
REFCOMP
is determined by the following equation.
𝐼
𝑅𝐸𝐹𝐶𝑂𝑀𝑃
= 𝑅
𝐿_𝐶𝑂𝑀𝑃
× 𝐾
𝐿_𝐶𝑂𝑀𝑃
× 𝐼
𝑆𝑊(𝐴𝑣𝑒)
𝑅
𝐿_𝐶𝑂𝑀𝑃
:
Resistor connected to the L_COMP pin
𝐼
𝑆𝑊(𝐴𝑣𝑒)
:
Average current flowing through the SW pin
K
L_COMP
:
Fixed value inside the IC
[V]
[V]
[µA]
V
OUT
I
OUT
With Load compensation
No load compensation
