Bootstrap power supply circuit
A GaN half bridge circuit is disclosed. The circuit includes a bootstrap power supply voltage generator is configured to supply a first power voltage and includes a switch node. The circuit also includes a bootstrap transistor, a bootstrap transistor drive circuit, and a bootstrap capacitor connected to the switch node and to the bootstrap transistor. The bootstrap capacitor is configured to supply the first power voltage while the voltage at the switch node is equal to the second switch node voltage, the bootstrap transistor is configured to electrically connect the bootstrap capacitor to a power node at a second power voltage while the voltage at the switch node is equal to the first switch node voltage, and the bootstrap power supply voltage generator does not include a separate diode in parallel with the drain and source of the bootstrap transistor.
1. A half bridge circuit, comprising:
a bootstrap power supply voltage generator configured to supply a first power voltage, the bootstrap power supply voltage generator comprising:
a switch node, wherein a voltage at the switch node changes between first and second switch node voltages;
a bootstrap transistor comprising a gate;
a bootstrap capacitor connected to the switch node and to the bootstrap transistor, wherein the bootstrap capacitor is configured to supply the first power voltage while the voltage at the switch node is equal to the second switch node voltage; and
a bootstrap transistor drive circuit comprising one or more depletion mode switches configured to control the voltage at a gate of the bootstrap transistor, wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is less than the voltage at the voltage power supply, and wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are further configured to conditionally cause the bootstrap transistor to be non-conductive while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is greater than the voltage at the voltage power supply.
2. The half bridge circuit of claim 1 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a conduction drive voltage, wherein the one or more depletion mode switches are configured to generate the conduction drive voltage.
3. The half bridge circuit of claim 1 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a conduction drive voltage, wherein the one or more depletion mode switches are configured to pass the conduction drive voltage from a conduction drive voltage generator circuit to the gate of the bootstrap transistor.
4. The half bridge circuit of claim 1 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to be non-conductive between a voltage power supply and the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a non-conduction drive voltage, wherein the one or more depletion mode switches are configured to pass the non-conduction drive voltage from a non-conduction drive voltage supply to the gate of the bootstrap transistor.
5. The half bridge circuit of claim 1 , wherein the bootstrap transistor drive circuit is configured to cause the bootstrap transistor to turn off in response to an electronic event, wherein the electronic event causes the voltage at the switch node to change from a first node voltage to a second node voltage.
6. A bootstrap power supply voltage generator circuit configured to supply a first power voltage, the bootstrap power supply voltage generator circuit comprising:
a switch node, wherein a voltage at the switch node changes between first and second switch node voltages;
a bootstrap transistor comprising a gate;
a bootstrap capacitor connected to the switch node and to the bootstrap transistor, wherein the bootstrap capacitor is configured to supply the first power voltage while the voltage at the switch node is equal to the second switch node voltage; and
a bootstrap transistor drive circuit comprising one or more depletion mode switches configured to control the voltage at the gate of the bootstrap transistor, wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is less than the voltage at the voltage power supply, and wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are further configured to conditionally cause the bootstrap transistor to be non-conductive while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is greater than the voltage at the voltage power supply.
7. The bootstrap power supply voltage generator circuit of claim 6 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a conduction drive voltage, wherein the one or more depletion mode switches are configured to generate the conduction drive voltage.
8. The bootstrap power supply voltage generator circuit of claim 6 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a conduction drive voltage, wherein the one or more depletion mode switches are configured to pass the conduction drive voltage from a conduction drive voltage generator circuit to the gate of the bootstrap transistor.
9. The bootstrap power supply voltage generator circuit of claim 6 , wherein the bootstrap transistor drive circuit is configured to conditionally cause the bootstrap transistor to be non-conductive between a voltage power supply and the bootstrap capacitor by causing a voltage at the gate of the bootstrap transistor to have a non-conduction drive voltage, wherein the one or more depletion mode switches are configured to pass the non-conduction drive voltage from a non-conduction drive voltage supply to the gate of the bootstrap transistor.
10. The bootstrap power supply voltage generator circuit of claim 6 , wherein the bootstrap transistor drive circuit is configured to cause the bootstrap transistor to turn off in response to a signal, wherein the signal causes the voltage at the switch node to change from the first switch node voltage to the second switch node voltage.
11. A bootstrap power supply generator circuit comprising:
a monolithic GaN substrate;
a power transistor, comprising a power gate, a power drain, and a power source, wherein a voltage at the power drain changes between first and second power drain node voltages according to a power control signal at the power gate;
a bootstrap transistor, comprising a bootstrap gate;
a bootstrap capacitor connected to the power drain, wherein the bootstrap transistor is configured to charge the bootstrap capacitor while a voltage at the power drain is equal to the first power drain node voltage, and wherein the bootstrap capacitor is configured to supply power to a circuit having another source connected to the power drain while a voltage at the power drain is equal to the second power drain node voltage; and
a bootstrap transistor drive circuit comprising one or more depletion mode switches configured to generate a bootstrap control signal at the bootstrap gate, wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are configured to conditionally cause the bootstrap transistor to conduct current from a voltage power supply to the bootstrap capacitor while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is less than the voltage at the voltage power supply, and wherein the one or more depletion mode switches of the bootstrap transistor drive circuit are further configured to conditionally cause the bootstrap transistor to be non-conductive while the voltage at a connection between the bootstrap capacitor and the bootstrap transistor is greater than the voltage at the voltage power supply,
wherein the bootstrap transistor drive circuit, the bootstrap transistor, and the power transistor are each integrated on the GaN substrate.
12. The bootstrap power supply generator circuit of claim 11 , further comprising a power transistor drive circuit configured to generate the power control signal based on a drive signal, wherein the bootstrap transistor drive circuit is configured to control the bootstrap control signal in response to the drive signal.
13. The bootstrap power supply generator circuit of claim 11 , wherein the bootstrap transistor drive circuit is configured to cause the bootstrap transistor to be non-conductive in response to a signal occurring while the power transistor is in a non-conductive state.