Introduction
Valley switching converters, also known as
quasi?resonant (QR) converters, allow designing flyback
Switch?Mode Power Supplies (SMPS) with reduced
Electro?Magnetic Interference (EMI) signature and
improved efficiency. Thanks to the low level of generated
noise, valley switching SMPS converters are therefore very
well suited to applications dealing with RF and video
signals, such as TVs.
ON Semiconductor NCP1337 is a powerful valley
switching controller, which eases the design of an
EMI?friendly TV power supply with only a few surrounding
components. Moreover, very low standby power (less than
1 W) can be achieved without any noise.
Main Features of the Controller
? Automatic Valley Switching
? Current?Mode
? Soft Ripple Mode with Minimum Switching Frequency
for Noise?Free Standby
? Auto?Recovery Short?Circuit Protection Independent
of Auxiliary Voltage
? Over Voltage Protection
? Brown?Out Protection
? 2 Externally Triggerable Fault Comparators
(Auto?Recovery or Permanent Latch)
? Internal 5 ms Soft?Start
? 500 mA Peak Current Source/Sink Capability
? 130 kHz Max Frequency
? Internal Leading Edge Blanking
? Internal Temperature Shutdown
? Direct Optocoupler Connection
? Dynamic Self?Supply