Buck converter with III-nitride switch for substantially increased input-to-output voltage ratio
View Patent ↗According to one exemplary embodiment, a buck converter for converting a high voltage at an input of the buck converter to a low voltage at an output of the buck converter includes a III-nitride switch interposed between the input and the output of the buck converter and a low resistance switch interposed between the output of the buck converter and a ground. The buck converter further includes a control circuit configured to control a duty cycle of the III-nitride switch. The III-nitride switch has a sufficiently high switching speed so as to allow a ratio of the input high voltage to the output low voltage of the buck converter to be substantially greater than 10.
1. A buck converter for converting a high voltage at an input of said buck converter to a low voltage at an output of said buck converter, said buck converter comprising:
a fast III-nitride switch interposed between said input and said output and a low resistance switch interposed between said output and a ground, wherein said fast III-nitride switch and said low resistance switch form a half-bridge directly coupled between said input of said buck converter and said ground;
wherein said fast III-nitride switch comprises a first depletion-mode (D-mode) III-nitride device coupled to a silicon transistor and a first diode coupled across said silicon transistor;
wherein said low resistance switch comprises a second D-mode III-nitride device coupled in series with a second diode;
a control circuit configured to control a duty cycle of said fast III-nitride switch in response to a feedback signal from said output;
said low resistance switch having a low on-state resistance and reduced charge storage;
said fast III-nitride switch having a sufficiently high switching speed so as to allow a ratio of said input high voltage to said output low voltage to be approximately 100 or higher.
2. The buck converter of claim 1 , wherein said first diode comprises a Schottky diode.
3. The buck converter of claim 2 , wherein said first D-mode III-nitride device is a GaN device.
4. The buck converter of claim 2 , wherein an anode of said Schottky diode is coupled to a source of said silicon transistor and a cathode of said Schottky diode is coupled to a drain of said silicon transistor.
5. The buck converter of claim 1 , wherein said second diode comprises a Schottky diode.
6. The buck converter of claim 5 , wherein said second D-mode III-nitride device is a GaN device.
7. The buck converter of claim 1 further comprising a buck inductor coupled between said fast HI-nitride switch and said output of said buck converter.
8. A voltage conversion circuit including a buck converter for converting a high voltage at an input of said buck converter to a low voltage at an output of said buck converter, said input of said buck converter being coupled to a full-bridge rectifier, said buck converter comprising:
a fast III-nitride switch interposed between said input and said output of said buck converter and a low resistance switch interposed between said output of said buck converter and said full-bridge rectifier, wherein said fast III-nitride switch and said low resistance switch form a half-bridge directly coupled between said input of said buck converter and said full-bridge rectifier;
wherein said fast III-nitride switch comprises a first depletion-mode (D-mode) III-nitride device coupled to a silicon transistor and a first diode coupled across said silicon transistor;
wherein said low resistance switch comprises a second D-mode III-nitride device coupled in series with a second diode;
a control circuit configured to control a duty cycle of said fast III-nitride switch in response to a feedback signal from said output;
said low resistance switch having a low on-state resistance and reduced charge storage;
said fast III-nitride switch having a sufficiently high switching speed so as to allow a ratio of said input high voltage to said output low voltage to be approximately 100 or higher.
9. The voltage conversion circuit of claim 8 , wherein a load is coupled between said output of said buck converter and said full-bridge rectifier.
10. The voltage conversion circuit of claim 9 , wherein said load comprises at least one high-power LED.
11. The voltage conversion circuit of claim 9 , wherein said buck converter further comprises a current sensor coupled between said load and said full-bridge rectifier.
12. The voltage conversion circuit of claim 8 , wherein said first diode comprises a Schottky diode.
13. The voltage conversion circuit of claim 8 , wherein said second diode comprises a Schottky diode.
14. The voltage conversion circuit of claim 8 further comprising an electromagnetic interference filter coupled to AC inputs of said full-bridge rectifier.
15. The voltage conversion circuit of claim 8 , wherein said buck converter further comprises a buck inductor coupled between said fast III-nitride switch and said output of said buck converter.