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