Switch drive controller, method of operation thereof and power converter employing the same

DETAILED DESCRIPTION To overcome the deficiencies of the prior art, the present invention provides, for use with a power converter coupled to a regulation circuit and having a power switch and an auxiliary switch coupled thereto, a controller, method of operating the power switch and auxiliary switch and a power converter employing the controller and method.
In one embodiment, the controller includes a voltage conditioning network, parallel-coupled to the power switch, capable of sensing a voltage across the power switch and developing a conditioned voltage.
The controller further includes a drive circuit, coupled to the voltage conditioning network, adapted to provide a drive signal to control the auxiliary switch as a function of the conditioned voltage and a regulation control signal from the regulation circuit.
The present invention, therefore, introduces the broad concept of developing a conditioned voltage associated with the power switch and controlling the auxiliary switch as a function thereof.
In an embodiment to be illustrated and described, the voltage conditioning network reduces the sensed voltage across the power switch for use by the drive circuit to control the auxiliary switch.
More specifically, a resistance across the drain and source terminals when the power switch is biased conducting may have a negative effect on the controller controlling the power and auxiliary switches.
To minimize the deleterious effects of the power switch's ON resistance (Rdson), and, ultimately, the drain-source voltage across the power switch device on the drive circuit, the voltage conditioning network reduces the sensed drain-source voltage of the power switch.
The conditioning of the sensed voltage across the power switch, prior to its introduction in the drive circuit, not only minimizes its effects on the drive circuit, but also allows the use of a less complex and least costly controller.
In one embodiment of the present invention, the drive circuit is adapted to provide another drive signal to control the power switch