Direct drive cascoded switching circuit

A half-bridge circuit, comprising:

• a first cascoded switch system forming an high-side switch of the half-bridge circuit;
• and
• a second cascoded switch system forming a low-side switch of the half-bridge circuit;
• and
• wherein each of the first cascoded switch system and the second cascoded switch system comprises:
• a cascoded switch including:
• a JFET coupled between a drain terminal and a cascode node of the cascoded switch;
• and
• a MOSFET coupled between the cascode node and a source terminal of the cascoded switch;
• and
• a drive circuit comprising:
• a JFET driver configured to receive an input signal and to output a JFET-drive signal to a capacitor coupled in series between the JFET driver and a gate of the JFET;
• a switch coupled between the gate of the JFET and the source terminal, the switch configured to be responsive to the input signal;
• a comparator configured to compare a JFET gate voltage against a threshold;
• and
• a MOSFET driver circuit configured to:
• drive the MOSFET in a MOSFET on-state during an on-state of the input signal;
• and
• drive the MOSFET in one of a MOSFET off-state and the MOSFET on-state in response to a comparison signal from the comparator during an off-state of the input signal.

A method, comprising:

• receiving a turn-on command;
• driving a JFET in a JFET on-state in response to the turn-on command;
• driving a MOSFET in a MOSFET on-state in response to the turn-on command;
• charging a capacitor coupled in series with a gate of the JFET in response to the turn-on command;
• receiving a turn-off command;
• driving the JFET, in response to the turn-off command, with a voltage stored across the capacitor;
• comparing a JFET gate voltage to a threshold to generate a comparison signal;
• and
• driving the MOSFET in response to the comparison signal.