Device and Circuit Design for Improving the Freewheeling Characteristics of High Voltage Monolithic Integrated Circuit

Abstract

In this article, a new freewheeling circuit with a junction field-effect transistor (JFET) structure is developed to replace the traditional high voltage diode for freewheeling in the high voltage monolithic IC for the first time. The JFET structure has its pinch-off voltage lower than 40 V, and it can sustain the reverse voltage higher than 500 V in off-state. Adopting the new freewheeling circuit, the reverse recovery charge (Q <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RR</sub> ) and the peak reverse recovery current (I <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">RRM</sub> ) is decreased boffy about 89.5% and 33.6%, respectively, when the load current is 0.5 A. Based on the proposed freewheeling circuit, a deadtime control circuit is also developed in this article. By employing that control circuit, it is no need to detect the output signal state of the counter channel before controlling the deadtime, therefore the deadtime could be designed as small as possible to decrease the freewheeling loss. In this article, the high voltage monolithic IC is implemented by thick layer silicon on insulator technology. All the new devices and circuits are compatible with the technology for the traditional monolithic IC without any additional process.