CMOS PWM CONTROL-CIRCUIT WITH PROGRAMMABLE DEAD-TIME

Some types of dc-dc power converters require a control circuit to prod uce two pulse width modulated (PWM) signals that are 180 degrees out o f phase. In many applications, a critical element of the control circu it is the capability to program a specified amount of dead time when b oth PWM signals are low. This paper presents an integrated circuit imp lementation of a control circuit that can be programmed with digital i nputs to produce variable dead times. The circuit was fabricated in 2- micron CMOS technology with a 1.7 mm x 1.7 mm die and tested to verify complete functionality. Control chips that are currently available re quire external capacitor/resistor combinations to produce the required dead time. A unique design of a Bi-CMOS buffer with an output current up to 1.4 A is also included, which enables the PWM circuit to direct ly drive the gates of power MOSFETs.