Cascode Power Switch for use in a High-Frequency Power MESFET Buck Switching Power Supply
A cascode power switch for use in a MESFET based switching regulator includes a MOSFET in series with a normally-off MESFET. The cascode power switch is typically connected in between a power source and a node Vx. The node Vx is connected to an output node via an inductor and to ground via a Schottky diode or a second MESFET or both. A control circuit drives the MESFET (and the second MESFET) so that the inductor is alternately connected to the battery and to ground. The MOSFET is switched off during sleep or standby modes to minimize leakage current through the MESFET. The MOSFET is therefore switched at a low frequency compared to the MESFET and does not contribute significantly to switching losses in the converter.
1 . A cascode power switch comprising a MOSFET in series with a normally-off MESFET.
2 . The cascode power switch of claim 1 where the MOSFET is N-channel.
3 . The cascode power switch of claim 1 where the drain of the MOSFET connects to the source of the MESFET.
4 . The cascode power switch of claim 1 where the source of the MOSFET connects to the drain of the MESFET.
5 . The cascode power switch of claim 1 where the MOSFET is P-channel.
6 . The cascode power switch of claim 5 where the drain of the MOSFET connects to the source of the MESFET.
7 . The cascode switch of claim 5 where the source of the MOSFET connects to the drain of the MESFET.
8 . The cascode switch of claim 1 where the MOSFET has a lower on-state resistance than the MESFET.
9 . The cascode switch of claim 1 where the MESFET is used in circuitry where the MOSFET switches at a lower frequency from the MESFET.
10 . The cascode switch of claim 1 where the MOSFET and MESFET gates are driven from different gate buffers.
11 . The cascode switch of claim 1 where the MESFET is made of GaAs.
12 . The cascode switch of claim 1 where the MESFET and the MOSFET are assembled in the same package.
13 . A protected MESFET device comprising a normally-off MESFET in parallel with a Zener diode, the Zener diode having an avalanche voltage lower than the avalanche voltage of the MESFET.
14 . A clamped cascode switch comprising a series connection of a normally off MESFET and a MOSFET, where the MESFET is connected in parallel with a Zener diode, where furthermore, the Zener diode has an avalanche voltage lower than the avalanche voltage of the MESFET.
15 . The clamped cascode switch of claim 14 where the source of the MESFET is connected to the drain of the MOSFET.
16 . The clamped cascode switch of claim 14 where the drain of the MESFET is connected to the source of the MOSFET.
17 . The clamped cascode switch of claim 14 where the MOSFET is N-channel.
18 . The clamped cascode switch of claim 14 where the MOSFET is P-channel.
19 . The clamped cascode switch of claim 14 where the MESFET is made of GaAs.
20 . A clamped cascode switch comprising a series connection of a normally off MESFET and a MOSFET, where the series connected MESFET and MOSFET is connected in parallel with a Zener diode, where furthermore, the Zener diode has an avalanche voltage lower than the avalanche voltage of the MESFET.
21 . The clamped cascode switch of claim 20 where the source of the MESFET is connected to the drain of the MOSFET.
22 . The clamped cascode switch of claim 20 where the drain of the MESFET is connected to the source of the MOSFET.
23 . The clamped cascode switch of claim 20 where the MOSFET is N-channel.
24 . The clamped cascode switch of claim 20 where the MOSFET is P-channel.
25 . The clamped cascode switch of claim 20 where the MESFET is made of GaAs.
26 . A cascode switch comprising a series connection of a normally off N-channel MESFET and an N-channel MOSFET, where the source of N-channel MOSFET is connected to the drain of the MESFET, and where the body of the N-channel MOSFET is connected to the source of the MESFET; and where the MOSFET includes a drain-to-body diode.
27 . The cascode switch of claim 26 where the avalanche voltage of the drain-to-body diode of the MOSFET is lower than that of the avalanche voltage of the MESFET.
28 . The cascode switch of claim 26 where a Zener diode is connected in parallel to the series combination of the MESFET and the MOSFET; having its cathode connected to the drain of the N-channel MOSFET and its anode connected to the source of the MESFET.
29 . The cascode switch of claim 26 where the MESFET is made of GaAs.
30 . A cascode switch comprising a series connection of a normally off N-channel MESFET and a P-channel MOSFET, where the source of P-channel MOSFET is connected to the drain of the MESFET, and where the body of the P-channel MOSFET is connected to the source of the MESFET; and where the MOSFET includes a drain-to-body diode.
31 . The cascode switch of claim 30 where the avalanche voltage of the drain-to-body diode of the MOSFET is lower than that of the avalanche voltage of the MESFET.
32 . The cascode switch of claim 30 where a Zener diode is connected in parallel to the series combination of the MESFET and the MOSFET; having its cathode connected to the source of the MESFET and its anode connected to the drain of the P-channel MOSFET.
32 . The cascode switch of claim 30 where the MESFET is made of GaAs.