一個應用於駐極式耳機並整合於CMOS 之高電壓驅動器設計

An Integrated CMOS High Voltage Driver for Electret Earphone Applications

曾偉凱(Wei-Kai Tseng)

指導教授 ： 黃柏鈞

國立清華大學/電機資訊學院/電機工程學系/碩士(2008年)

摘要

在系統晶片的發展趨勢底下，由於考慮到功率消耗、速度及可靠度上的問題，所以降低操作電壓是一個發展的趨勢。但在許多應用當中仍舊是需要較高的操作電壓，例如：Flash Memory、EEPROM、LCD Driver...等。在本研究報告中，我們將介紹一個駐極式耳機驅動器，這是個需要較高電壓驅動之應用。有別於傳統需要靠大電流驅動之動圈式耳機，駐極式耳機不需要大電流的驅動，但卻需要以高振幅之電壓驅動。基於駐極式耳機不需要消耗大量電流的特性，所以切換電容式升壓電路非常適合提供此類應用之驅動器所需之電壓。
為了減少成本，在本研究報告中會將產生高電壓之電路及高電壓驅動器整合在一標準金氧半製程當中。當標準金氧半製程元件操作在高電壓的情況下，將會造成許多可靠度上的問題，所以在這次的設計中，我們將會對元件的可靠度做詳盡的考量。另外，由於MOS電容的單位面積電容值為MIM電容之八倍，為了減小面積的使用，我們將會以MOS電容取代MIM電容。為了確保MOS電容不會有可靠度上的問題，我們將提出一個令電容之跨壓皆小於標準電壓之架構。為了能夠提供穩定之電壓輸出，一個爆發式穩壓控制迴路將會被使用在我們的升壓電路當中。並且，這些電路將會被整合在一個標準的金氧半製程當中。
在我們所提出的架構中，升壓電路在最大負載350μA底下均能輸出穩定之6V電壓。在驅動器電路部份，輸出振幅可以高達6V而且不會有可靠度上的問題。以橋接方式來驅動耳機的話，最高能達到80dB之音壓輸出。

關鍵字

升壓電路 ； 高電壓驅動器電路

並列摘要

In this work, a special high voltage application, the electret earphone driver, will be presented. Instead of requiring high current, the electret earphone needs to be driven with high voltage swing. Since the characteristic of electrostatic earphone consumes no large current, the charge pump is a good solution to provide high voltage to the driver.
To reduce the cost, the high-voltage generator and driver circuit is fully integrated in standard CMOS process technology in this work. Devices in standard CMOS process technology operating with high voltage may cause several reliability problems, such as oxide breakdown and hot carrier effect. In this design, these reliability issues have been well considered. Morover, MOS capacitors are used instead of MIM capacitors to reduce chip area since the unit capacitance of MOS capacitor is greater than MIM capacitor. A new topology of voltage multiplier is proposed which makes the cross voltage of all capacitors less than standard power supply voltage to guarantee the reliability of MOS capacitor. To sustain stable voltage output, a burst mode control regulation loop around the voltage multiplier is implemented. To make system-on-chip possible, all these functions are integrated in a standard CMOS process technology.
The proposed regulated voltage multiplier can achieve 6V output voltage under the loading current from 100uA to 350uA. The output swing of the driver is up to 6V and the reliability of all transistors is well concerned. A bridge connected high-voltage driver can drive the electret earphone to almost 80dB sound pressure level.

並列關鍵字

High Voltage Generation ； High Voltage Driver

參考文獻

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