NCP1602 Datasheet, PDF (31/32 Pages) ON Semiconductor – Enhanced, High-Efficiency Power Factor Controller

NCP1602
Generally speaking, the circuit turns off when the
conditions are not proper for desired operation. In this mode,
the controller stops operating. The major part of the circuit
sleeps and its consumption is minimized.
More specifically, when the circuit is in OFF state:
• The drive output is kept low
• All the blocks are off except:
♦ The UVLO circuitry that keeps monitoring the V_CC
voltage and controlling the start−up current source
accordingly.
♦ The TSD (thermal shutdown)
♦ The Under−Voltage Protection (“UVP”)
♦ The brown−out circuitry
• V_ctrl is grounded so that when the fault is removed, the
device starts−up under the soft start mode (version XB).
• The internal “PFCOK” signal is grounded.
• The output of the “V_ton processing block” is grounded
Failure Detection
When manufacturing a power supply, elements can be
accidentally shorted or improperly soldered. Such failures
can also happen to occur later on because of the components
fatigue or excessive stress, soldering defaults or external
interactions. In particular, adjacent pins of controllers can be
shorted; a pin can be grounded or badly connected. Such
open/short situations are generally required not to cause fire,
smoke nor big noise. NCP1602 integrate functions that ease
meet this requirement. Among them, we can list:
• Floating feedback pin
A special internal circuitry detects the floating feedback
pin and stops the operation of the IC.
• Fault of the GND connection
If the GND pin is not connected, internal circuitry
detects it and if such a fault is detected for 200 ms, the
circuit stops operating.
• Detection the CS/ZCD pin improper connection
If the CS/ZCD pin is floating or shorted to GND it is
detected by internal circuitry and the circuit stops
operating.
• Boost or bypass diode short
The controller addresses the short situations of the
boost and bypass diodes (a bypass diode is generally
placed between the input and output high−voltage rails
to divert this inrush current). Practically, the overstress
protection is implemented to detect such conditions and
forces a low duty−cycle operation until the fault is gone.
Refer to application note ANDxxxx for more details.
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