IntroductionValley switching converters, also known asquasi−resonant (QR) converters, allow designing flybackSwitch−Mode Power Supplies (SMPS) with reducedElectro−Magnetic Interference (EMI) signature andimproved efficiency. Thanks to the low level of generatednoise, valley switching SMPS converters are therefore verywell suited to applications dealing with RF and videosignals, such as TVs.ON Semiconductor NCP1337 is a powerful valleyswitching controller, which eases the design of anEMI−friendly TV power supply with only a few surroundingcomponents. Moreover, very low standby power (less than1 W) can be achieved without any noise.Main Features of the Controller• Automatic Valley Switching• Current−Mode• Soft Ripple Mode with Minimum Switching Frequencyfor Noise−Free Standby• Auto−Recovery Short−Circuit Protection Independentof 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