NCP1606 ON Semiconductor, NCP1606 Datasheet - Page 16

• Manufacturer Part Number: NCP1606
• Description: Cost Effective Power Factor Controller
• Manufacturer: ON Semiconductor

R
equilibrium
compensation capacitor (“C
•
where (V
•
•
Conversely when V
output of the error amplifier sinks or sources the current
necessary to maintain 2.5 V on pin 1. In particular, in the
case of an overvoltage condition:
•
•
I
OUT2
When the output voltage is in steady state, R
R
Under stable conditions, these equations are true.
where DV
The R
The R
And since no current flows through C
The error amplifier maintains 2.5 V on pin 1, and the
R
The R
I
OUT1
R
R
OUT2
R
OUT1
OUT1
OUT2
V
+I
regulate the FB voltage to 2.5 V. Also, during this
OUT
OUT1
OUT2
OUT1
OUT
+
current remains:
R
OUT2
V
OUT
)
OUT
state, no current flows through the
current is:
nom
current is:
current is:
I
R
R
å
OUT1
Control
OUT1
is the output voltage excess.
−2.5 V
is the nominal output voltage.
(V
C
OUT
COMP
FB
I
I
+
OUT
R
R
OUT2
OUT2
(V
+
)
R
is not at its nominal level, the
nom
OUT
OUT1
(V
+ 2.5 V
+ 2.5 V
COMP
OUT
* 2.5 V
)
R
R
R
nom
OUT1
OUT2
OUT2
” of Figure 1). Therefore:
)
nom
* 2.5 V
R
) DV
+ 2.5 V
V
+
OUT1
CONTROL
I
Figure 34. OVP and UVP Circuit Blocks
control
COMP
+
R
OUT2
OUT
300 mV
E/A
,
2.5 V
+
+
−
−
−2.5 V
OUT1
(eq. 10)
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UVP
(eq. 6)
(eq. 7)
(eq. 8)
(eq. 9)
and
Enable
(Enable EA)
16
•
simple expression of the current sunk by the error
amplifier:
proportional to the output voltage excess. The circuit
senses this current and disables the drive (pin 7) when
I
10.4 mA in NCP1606B). This gives the OVP threshold as:
set. Therefore, one can compute the R
resistances using the following procedure:
CONTROL
The combination of equations (4) and (7) leads to a very
Hence, the current absorbed by pin 2 (I
By simply adjusting R
Therefore, the error amplifier sinks:
Measure
I
I
R
control
Clamp
1. Select R
2. Select R
Clamp
OUT1
V
V
V
EAL
EAH
DD
For instance if implementing the NCP1606B, and
420 V is the maximum output level and 400 V is the
nominal output level, then
(V
−I
OUT
R
exceeds I
Static OVP
R
Static OVP is triggered
when clamp is activated.
OUT2
I
Dynamic OVP
PIN2
I
OUT1
control
)
R
OVP
OUT1
OUT1
OUT2
+
+ I
+
> I
+ (V
(V
OVP
R
ovp
+ 420 * 400
to set the desired overvoltage level:
(V
to adjust the regulation level:
OUT
OUT1
OUT
OUT
OUT1
)
(typically 40 mA in NCP1606A,
10.4 mA
nom
* I
)
)
OVP
nom
R
, the OVP limit can be easily
) DV
R
I
OUT1
OUT2
OVP
* (V
) (R
+ 1.9 MW
+
OUT
OUT
OUT1
DV
R
−2.5 V
OUT1
OUT1
)
OUT
nom
@ I
Fault
CONTROL
OVP
− 2.5 V
and R
R
)
OUT2
(eq. 12)
(eq. 11)
OUT2
) is