Gate drive apparatus and method thereof

1. An apparatus comprising:

a plurality of pull-up switches connected in parallel between a first voltage bus and a gate of a power switch, wherein the plurality of pull-up switches is configured such that in a turn-on process of the power switch, a gate current of the power switch changes twice so that a low turn-on gate current flows into the gate of the power switch after a first high turn-on gate current and before a second high turn-on gate current; and

a plurality of pull-down switches connected in parallel between the gate of the power switch and a second voltage bus, wherein the plurality of pull-down switches is configured such that in a turn-off process of the power switch, the gate current of the power switch changes twice so that a low turn-off gate current flows out of the gate of the power switch after a first high turn-off gate current and before a second high turn-off gate current.

2. The apparatus of claim 1 , further comprising:

a plurality of pull-up resistors, each of which is connected in series with a corresponding pull-up switch; and

a plurality of pull-down resistors, each of which is connected in series with a corresponding pull-down switch.

3. The apparatus of claim 1 , wherein:

the first voltage bus is connected to a bias voltage source; and

the second voltage bus is connected to ground.

4. The apparatus of claim 1 , wherein:

a current value of the first high turn-on gate current is equal to a current value of the second high turn-on gate current; and

a current value of the first high turn-off gate current is equal to a current value of the second high turn-off gate current.

5. The apparatus of claim 1 , wherein:

at least one gate drive voltage applied to one of the plurality of pull-up switches is modulated so as to adjust the gate current of the power switch; and

at least one gate drive voltage applied to one of the plurality of pull-down switches is modulated so as to adjust the gate current of the power switch.

6. The apparatus of claim 1 , wherein:

the gate current of the power switch changes from a first predetermined pull-up current level to a second predetermined pull-up current level once a signal on a switching node changes over a first turn-on threshold; and

the gate current of the power switch changes from the second predetermined pull-up current level to the first predetermined pull-up current level once a gate drive voltage exceeds a second turn-on threshold, and wherein the signal on the switching node is a variable selected from the group consisting of a switching node voltage difference over time, a slew rate of the switching node voltage difference over time and a current flowing through the power switch.

7. The apparatus of claim 1 , wherein:

the gate current of the power switches changes from a first predetermined pull-down current level to a second predetermined pull-down current level once a signal on a switching node changes over a first turn-off threshold; and

the gate current of the power switches changes from the second predetermined pull-down current level to the first predetermined pull-down current level once the gate drive voltage drops below a second turn-off threshold, and wherein the signal on the switching node is a variable selected from the group consisting of a switching node voltage difference over time, a slew rate of the switching node voltage difference over time and a current flowing through the power switch.

8. The apparatus of claim 1 , wherein:

during the turn-on process of the power switch, a slew rate of a voltage on a switching node is configured to be adjustable through adjusting at least one of the first high turn-on gate current and the second high turn-on gate current.

9. The apparatus of claim 1 , wherein:

during the turn-off process of the power switch, a slew rate of a voltage on a switching node is configured to be adjustable through adjusting at least one of the first high turn-off gate current and the second high turn-off gate current.

10. The apparatus of claim 1 , wherein:

the low turn-on gate current occurs in a Miller plateau phase of the turn-on process of the power switch.

11. The apparatus of claim 1 , wherein:

the low turn-off gate current occurs in a Miller plateau phase of the turn-off process of the power switch.

12. A method comprising:

in a turn-on process of a power switch, configuring a plurality of pull-up switches so that a first high turn-on gate current, a low turn-on gate current and a second high turn-on gate current occur in a phase prior to a turn-on Miller plateau phase, the turn-on Miller plateau phase, and a phase after the turn-on Miller plateau phase, respectively; and

in a turn-off process of the power switch, configuring a plurality of pull-down switches so that a first high turn-off gate current, a low turn-off gate current and a second high turn-off gate current occur in a phase prior to a turn-off Miller plateau phase, the turn-off Miller plateau phase, and a phase after the turn-off Miller plateau phase, respectively.

13. The method of claim 12 , further comprising:

detecting a voltage on a switching node connected to the power switch;

detecting a gate drive voltage of the power switch;

during the turn-on process of the power switch, reducing the gate current from the first high turn-on gate current to the low turn-on gate current once the voltage on the switching node changes over a first turn-on threshold; and

during the turn-on process of the power switch, increasing the gate current from the low turn-on gate current to the second high turn-on gate current once the gate drive voltage exceeds a second turn-on threshold.

14. The method of claim 13 , wherein:

during the turn-on process of the power switch, once the voltage on the switching node changes over the first turn-on threshold, the power switch enters into the turn-on Miller plateau phase; and

during the turn-on process of the power switch, once the gate drive voltage exceeds the second turn-on threshold, the power switch leaves the turn-on Miller plateau phase.

15. The method of claim 12 , wherein:

the plurality of pull-up switches is connected between a bias voltage source and a gate of the power switch; and

the plurality of pull-down switches is connected between the gate of the power switch and ground.

16. The method of claim 12 , further comprising:

detecting a voltage on a switching node connected to the power switch;

detecting a gate drive voltage of the power switch;

during the turn-off process of the power switch, reducing the gate current from the first high turn-off gate current to the low turn-off gate current once the voltage on the switching node changes over a first turn-off threshold; and

during the turn-off process of the power switch, increasing the gate current from the low turn-off gate current to the second high turn-off gate current once the gate drive voltage drops below a second turn-off threshold.

17. The method of claim 16 , wherein:

during the turn-off process of the power switch, once the voltage on the switching node changes over the first turn-off threshold, the power switch enters into the turn-off Miller plateau phase; and

during the turn-off process of the power switch, once the gate drive voltage drops below the second turn-off threshold, the power switch leaves the turn-off Miller plateau phase.

18. A controller comprising:

a first sensing circuit configured to receive a gate drive voltage of a power switch;

a second sensing circuit configured to receive a voltage on a switching node connected to the power switch; and

an adaptive slew rate control apparatus comprising a plurality of pull-up switches and a plurality of pull-down switches, wherein:

the plurality of pull-up switches is connected in parallel between a bias voltage source and a gate of the power switch, wherein the plurality of pull-up switches is configured such that a turn-on gate current changes twice in a turn-on process of the power switch; and

the plurality of pull-down switches is connected in parallel between the gate of the power switch and ground, wherein the plurality of pull-down switches is configured such that a turn-off gate current changes twice in a turn-off process of the power switch.

19. The controller of claim 18 , wherein:

at least one gate drive voltage applied to one of the plurality of pull-up switches is modulated so as to adjust the turn-on gate current flowing through the plurality of pull-up switches; and

at least one gate drive voltage applied to one of the plurality of pull-down switches is modulated so as to adjust the turn-off gate current flowing through the plurality of pull-down switches.

20. The controller of claim 18 , wherein:

during the turn-on process of the power switch, a first turn-on gate current change occurs when the power switch enters into a Miller plateau phase of the turn-on process;

during the turn-on process of the power switch, a second turn-on gate current change occurs when the power switch leaves the Miller plateau phase of the turn-on process;

during the turn-off process of the power switch, a first turn-off gate current change occurs when the power switch enters into a Miller plateau phase of the turn-off process of the power switch; and

during the turn-off process of the power switch, a second turn-off gate current change occurs when the power switch leaves a Miller plateau phase of the turn-off process of the power switch.