The TPS68000 device provides a power supply controller solution for CCFL backlight applications in a large variety of applications. The wide input voltage range of 8 V to 30 V makes it suitable to be powered directly from regulated 12-V or 24-V rails, or any other source with output voltages in this range. When using a 10% accurate regulated 5-V rail, it also can be used in notebook computers or other portable battery-powered equipment having lower minimum supply voltages. The controller is capable of driving the gates of all 4 NMOS switches directly without the need for any additional circuitry, like dedicated gate drivers or gate-drive transformers. The wide input voltage range also makes it easy to design CCFL converters with higher input voltages like 120 V or 400 V available at the output of a power factor correction unit. The TPS68000 also supports CCFL converter circuits driving multi-lamp applications, either by using higher power-rated switches and transformers, or using several TPS68000s synchronized. When synchronized, they can be operated either at the same frequency and phase, or phase shifted to minimize RMS input current. Already implemented smart dimming features, such as support of distributed dimming, also help to optimize the performance of multi-controller applications.

To start the lamp, an automatic strike control is implemented. It smoothly increases the lamp voltage by sweeping the operating frequency across the self resonance frequency of the transformer-series capacitor resonant circuit. During this time the maximum lamp voltage is limited and regulated by a voltage control loop until the lamp current increases to a value allowing the current control loop to take over control. The lamp current is regulated over a wide current range. To set the lamp brightness, analog and PWM dimming circuits are implemented. Analog and PWM dimming can be used independent of each other to control lamp brightness over a wide range.

To protect the circuit during fault conditions, for example broken, disconnected, or shorted lamps, overvoltage protection and overcurrent protection circuits are implemented. To protect the TPS68000 from overheating, an internal temperature sensor is implemented that triggers controller turn-off at an excessive device temperature.Read more