NCP1205P ON Semiconductor, NCP1205P Datasheet - Page 11

• Manufacturer Part Number: NCP1205P
• Description: IC CTRLR PWM CM OVP UVLO HV 8DIP
• Manufacturer: ON Semiconductor

Specifications of NCP1205P

• Output Isolation: Isolated
• Frequency Range: 90 ~ 125kHz
• Voltage - Input: 8 ~ 36 V
• Voltage - Output: 12V
• Operating Temperature: -25°C ~ 150°C
• Package / Case: 8-DIP (0.300", 7.62mm)
• Number Of Outputs: 1
• Output Current: 250 mA
• Mounting Style: Through Hole
• Switching Frequency: 125 KHz
• Operating Supply Voltage: 30 V
• Maximum Operating Temperature: + 125 C
• Fall Time: 30 ns
• Minimum Operating Temperature: - 25 C
• Rise Time: 30 ns
• Synchronous Pin: No
• Topology: Flyback, Forward
• Lead Free Status / RoHS Status: Contains lead / RoHS non-compliant
• Other names: NCP1205POS

moves with the output power demand. The components used
for the simulation were: Vin = 300 V, Lp = 6.5 mH,
Vout = 10 V, Np/Ns = 12.
clamped. At this time, the VCO takes over and decreases the
switching frequency to the minimum value.
VCO Operation
levels above 1.0 V, the VCO frequency remains unchanged
at 125 kHz. As soon as Verr starts to decrease below 1.0 V,
If we now enter this formula into a spreadsheet, we can easily plot the switching frequency versus the output power demand:
The typical above diagram shows how the frequency
The red line indicates where the maximum frequency is
The VCO is controlled from the Verr voltage. For Verr
Figure 12. When the Power Demand goes Low, the Peak Current is Frozen and the Frequency Decreases
V
is Fixed at 130 kHz
V
can Decrease
CO
CO
Frequency
Frequency
250000
200000
150000
100000
50000
Figure 11. A Typical Behavior of Free Running Systems
with a Smooth Frequency Foldback with the NCP1205
0
0
Internal V
Fmax
V
CO
Action
err
http://onsemi.com
5
Peak Current is Fixed
OUTPUT POWER (W)
BCM Mode
Fmax
Transition
BCM to VFM
11
10
the VCO frequency decreases with a typical small- -signal
slope of - -175 kHz/mV @ Verr = 500 mV down to
zero (typically at FB  3.3 V). The demagnetization
synchronization is however kept when the Toff expands.
The maximum switching frequency can be altered by
adjusting the Ct capacitor on pin 5. The 125 kHz maximum
operation ensures that the fundamental component stays
external
specification beginning.
the idea:
The following drawing explains the philosophy behind
Peak current
can change
from
15
the
international
20
3 V
1 V
0.75 V
EMI
CISPR- -22