High Speed FET Drivers

CogniPower is demonstrating next generation high speed FET switch drivers at APEC 2012. The evaluation board shown below is designed to run at up to 10 MHz while driving moderate sized FETs or IGBTs. Enhance and deplete voltages can be selected to best fit the application. The demo system produces 24 volt transitions at the output with switching times of about 2 ns.

    High Speed FET Driver Demonstration Board
The three heat sinks to the right are the load.
The crucial circuitry is within the outline labeled DRIVER. It occupies only 0.75 square inches, including filter capacitors.

The input is a logic signal, lightly loaded. The gate driver provides current gain of about 500 with a latency under 20 ns. This proprietary gate drive approach, when combined with CogniPower's patent pending common mode switch drive, will result in totem pole switching that is even faster than CogniPower's previous generation devices.

The demonstration system drives a 40 volt FET that has a little over 1nf gate capacitance, and is rated at 30 Amps continuous drain current. The FET is switching an 8 ohm load, in this case, on a 24 VDC power rail. When driving less capacitive switches, the frequency can be increased. More capacitive power switches can be run at lower frequencies.

The simplicity and flexibility of these drivers suit them for the latest process technologies and the fastest FET power switches. CogniPower switch drivers can be built in modular form for ease of implementation. This technology can be extended for up to 20 MHz operation. Enhance and deplete voltages can be set as desired. Contact us for more information.

    Block Diagram of CogniPower High Speed FET Driver Demonstration Board

    The green trace is the drain voltage of the power FET switching 24 volts at 1 MHz. The yellow trace is the gate drive waveform with 7 volts enhancement and -3 volts depletion.

    Expanded view of turn on shows voltage slew of 24 volts in 2 ns.