High Voltage Bipolars from STMicroelectronics to Aid CRT Revival
STMicroelectronics has introduced a new family of high-voltage power bipolar transistors, the HD1 family, specifically designed to meet the requirements for horizontal deflection in new high-definition and 'Super-Slim' CRT (Cathode Ray Tube) displays.
Although traditional CRT displays have lost ground in recent years to flat-screen displays based on LCD (Liquid Crystal Display) or PDP (Plasma Display Panel) technologies that take up significantly less space on the desk or in the living room, CRT technology continues to offer better display quality and lower costs. The CRT display is making a fight back with a new breed of so-called 'Super-Slim' CRT displays in which the depth of the display is reduced by typically 30%, resulting in a footprint comparable to that of LCD displays.
Because these new displays employ pictures tubes of significantly reduced depth, the angle through which the electron beam must be deflected during each horizontal scan is increased from 110 degrees to typically 124 degrees, which places stringent new demands on the bipolar power transistors that control the flow of current through the horizontal deflection coils.
To meet this requirement, the HD1 devices are built with a new, proprietary high-voltage bipolar technology, EHVS1 (Enhanced High Voltage Structure), which features a float-zone collector on a diffused substrate with a redesigned high voltage edge structure. Due to the reduction of capacitance in the base-collector junction by the use of a special deep-base process, the new HD1 devices are able to sustain very high breakdown voltages (up to 1700V), while simultaneously offering both high-current capability and high switching speeds.
A major benefit of the EHVS1 technology is that HD1 devices offer a wider range of optimum drive conditions, typically allowing up to 15% variation in base current around the optimum value. This allows power losses to be minimized over a wider range of operating conditions.
For example, under worst-case conditions in a wide-screen 100Hz TV application the HD1750FX device consumes only 10W, about 1W less than the best competitive solution. The HD1 devices also exhibit a lower sensitivity to operating temperature variations and an extended RBSOA (Reverse Bias Safe Operating Area) for more reliable and consistent switching performance, as well as reduced saturation voltage at high current.
Both reduced power losses and its very high switching frequency (over 100kHz) also make the HD1 series ideal for high-end digital TVs, rear-projection TVs as well as for professional monitor displays such as those required for working station and medical applications.
