Phase-Shift PWM Controller

OZ964 is a high efficiency, Pulse Width Modulation (PWM) controller designed for both DC/DC and DC/AC High-Voltage applications. The average current mode control is suitable for DC/DC converters where both voltage and current feedback are required, as well as for Cold Cathode Fluorescent Lamp (CCFL)_ backlight applications for small and large Liquid Crystal Displays (LCD). OZ964 operates in a zero-voltage switching mode that minimizes electromagnetic interference (EMI). In addition, OZ964 achieves a high power-conversion efficiency resulting in a lower operating temperature and higher system reliability. OZ964 supports a wide input voltage range and provides a constant, user-defined, operating frequency, ensuring that the CCFLs operate at a fixed frequency. This eliminates interference among CCFLs and the LCD panel. Interference causes electromagnetic compatibility (EMC) problems and may create visual effects (waterfall) on LCD panels. The controller provides a phase-shift square wave output that is able to drive a full bridge power train. OZ964 utilizes a pulse width modulation (PWM) dimming method to achieve a wide dimming range. The IC performs the CCFL dimming function with an Analog or low frequency PWM control. The PWM frequency is user-defined. To avoid over-shoot and in-rush current to the CCFLs during ignition, a soft start function is provided for reliable CCFL operation. The controller provides open-lamp protection and over-voltage protection, while providing an appropriate response for either open-lamp ignition or removal of a CCFL during normal operation. Intelligent open-lamp protection and over voltage protection provides design flexibility with various transformer characteristics. Open- lamp protection time is user-defined. In addition, OZ964 provides a shutdown delay function that will keep the inverter module in normal operation for a short period of time if the input voltage suddenly drops and subsequently resumes to a normal level. The shutdown delay time is user-defined. By Unkown