NCP1028 ON Semiconductor, NCP1028 Datasheet - Page 13

• Manufacturer Part Number: NCP1028
• Description: High?voltage Switcher For Medium Power Offline Smps
• Manufacturer: ON Semiconductor

Fault Condition – Output Short-Circuit
internally enabled. If everything is correct, the auxiliary
winding increases the voltage on the V
voltage rises. During the start-sequence, the controller
smoothly ramps up the peak current to Imax setting, e.g.
Ipeak_HI, which is reached after a typical period of 1.0 ms.
As soon as the peak current setpoint reaches its maximum
(during the startup period but also anytime an overload
occurs), an internal error flag is asserted, Ipflag, indicating
As soon as V
Figure 26. In case of short-circuit or overload, the NCP1028 protects itself and the power supply via a low
frequency burst mode. The V
CC
reaches VCC
ON
CC
CC
, drive pulses are
pin as the output
is maintained by the current source and self-supplies the controller.
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NCP1028
13
that the system has reached its maximum current limit set
point (Ip = Ip max). The assertion of this flag triggers a
55 ms counter. If at counter completion Ipflag remains
asserted, all driving pulses are stopped and the part stays off
during eight periods of 55 ms (440 ms). A new attempt to
restart occurs and will last 55 ms providing the fault is still
present. If the fault still affects the output, a safe burst mode
is entered, affected by a low duty-cycle operation (11%).
When the fault disappears, the power supply quickly
resumes operation. Figure 26 depicts this particular mode.