Bootstrap supply for switched mode power converter
View Patent ↗A power converter controller is operable to control power provided to a load circuit coupled between a first voltage supply terminal and a first switching element by controlling the first switching element and to control power provided to an energy storage element coupled to the first switching element. The energy storage element is operable to provide a power supply. A first control terminal couples to a control input of the first switching element. A first load terminal couples to the first switching element and the charge storing element. A second switching element couples between the first load terminal and a second voltage supply terminal. Timing logic is operable to selectively provide a control signal at the first control terminal to control the first switching element and to selectively control the second switching element to supply power to the load circuit during a load powering phase by enabling the first and second switching elements, charge the energy storage element during a bootstrap charging phase by enabling the first switching element and disabling the second switching element, and allowing the load circuit to operate in isolation during a passive phase by disabling at least the first switching element.
1. A power converter controller operable to control power provided to a load circuit coupled between a first voltage supply terminal and a first switching element by controlling the first switching element and to control power provided to an energy storage element coupled to the first switching element, the energy storage element being operable to provide a power supply, comprising:
a first control terminal for coupling to a control input of the first switching element;
a first load terminal coupled to the first switching element and the charge storing element;
a second switching element coupled between the first load terminal and a second voltage supply terminal; and
timing logic operable to selectively provide a control signal at the first control terminal to control the first switching element and to selectively control the second switching element to supply power to the load circuit during a load powering phase by enabling the first and second switching elements, charge the energy storage element during a bootstrap charging phase by enabling the first switching element and disabling the second switching element, and allowing the load circuit to operate in isolation during a passive phase by disabling at least the first switching element, wherein the timing logic comprises a first latch coupled to enable the first switching element and a second latch operable to enable the second switching element.
2. The power converter of claim 1 , further comprising a third switching element coupled between the energy storage element and the node.
3. The power converter of claim 2 , wherein the third switching element comprises a diode.
4. The power converter of claim 2 , wherein the timing logic is operable to enable the third switching element during the bootstrap charging phase.
5. The power converter of claim 1 , wherein the first switching element comprises an enhancement mode transistor.
6. The power converter of claim 1 , wherein the first switching element comprises a depletion mode transistor.
7. The power converter of claim 1 , wherein the timing logic implements the load powering phase after the bootstrap charging phase during a switching cycle of the power converter.
8. The power converter of claim 1 , wherein the timing logic comprises a pre-charge circuit for charging the energy storage element during a start-up period of the power converter.
9. The power converter of claim 8 , wherein the pre-charge circuit includes a resistor coupled between the first voltage supply terminal and the energy storage element.
10. The power converter of claim 9 , further comprising:
a switch coupled between the resistor and the energy storage element, the switch being closed when the start-up period initiates; and
an undervoltage lockout operable to open the switch responsive to a voltage on the energy storage element exceeding a first predetermined threshold.
11. The power converter of claim 1 , wherein the timing logic comprises a pre-charge circuit including a resistor coupled between the first voltage supply terminal and a control terminal of the first switching element.
12. The power converter of claim 1 , further comprising a load feedback unit operable to reset at least one of the first or second latches responsive to a load feedback parameter matching a predetermined threshold to initiate the bootstrap charging phase, wherein the load feedback unit is operable to determine current flowing through the second switching element to generate the load feedback parameter.
13. The power converter of claim 1 , wherein the first switching element comprises an enhancement mode transistor, and the timing logic further comprises:
an oscillator operable to set the second latch to initiate the load powering phase;
a load feedback unit operable to reset the first and second latches responsive to a load feedback parameter matching a predetermined threshold to initiate the bootstrap charging phase; and
a comparator operable to set the first latch responsive to a voltage on the energy storage element exceeding a first predetermined threshold to terminate the bootstrap charging phase and disable the first switching element to initiate the passive phase.
14. The power converter of claim 1 , wherein the first switching element comprises a depletion mode transistor, and the timing logic further comprises:
an oscillator operable to set the first and second latches to initiate the load powering phase;
a load feedback element operable to reset the second latch responsive to a load feedback parameter matching a predetermined threshold to initiate the bootstrap charging phase; and
a comparator operable to reset the first latch responsive to a voltage on the energy storage element exceeding a first predetermined threshold to terminate the bootstrap charging phase and disable the first switching element to initiate the passive phase.
15. The power converter of claim 1 , wherein the first switching element comprises a depletion mode transistor, and the timing logic further comprises:
an oscillator operable to set the first latch and initiate the bootstrap charging phase;
a comparator operable to set the second latch responsive to a voltage on the energy storage element exceeding a first predetermined threshold to terminate the bootstrap charging phase and enable the second switching element to initiate the load powering phase; and
a load feedback element operable to reset the first and second latches responsive to a load feedback parameter matching a predetermined threshold to disable the first and second switching elements and initiate the passive phase.
16. The power converter of claim 1 , wherein the second voltage supply terminal comprises a ground terminal.
17. The power converter of claim 1 , wherein the load circuit includes one of an inductor, a transformer, or a piezoelectric device.
18. The power converter of claim 1 , wherein the energy storage element comprises one of a capacitor or a battery.
19. A power converter controller operable to control power provided to a load circuit coupled between a first voltage supply terminal and a first switching element by controlling the first switching element and to control power provided to an energy storage element coupled to the first switching element, the energy storage element being operable to provide a power supply, comprising:
a first control terminal for coupling to a control input of the first switching element;
a first load terminal coupled to the first switching element and the charge storing element;
a second switching element coupled between the first load terminal and a second voltage supply terminal;
timing logic operable to selectively provide a control signal at the first control terminal to control the first switching element and to selectively control the second switching element to supply power to the load circuit during a load powering phase by enabling the first and second switching elements, charge the energy storage element during a bootstrap charging phase by enabling the first switching element and disabling the second switching element, and allowing the load circuit to operate in isolation during a passive phase by disabling at least the first switching element, wherein the timing logic comprises a pre-charge circuit for charging the energy storage element during a start-up period of the power converter, wherein the pre-charge circuit includes a resistor coupled between the first voltage supply terminal and the energy storage element;
a switch coupled between the resistor and the energy storage element, the switch being closed when the start-up period initiates; and
an undervoltage lockout operable to open the switch responsive to a voltage on the energy storage element exceeding a first predetermined threshold.
20. The power converter of claim 19 , further comprising a third switching element coupled between the energy storage element and the node.
21. The power converter of claim 20 , wherein the third switching element comprises a diode.
22. The power converter of claim 20 , wherein the timing logic is operable to enable the third switching element during the bootstrap charging phase.
23. The power converter of claim 19 , wherein the first switching element comprises an enhancement mode transistor.
24. The power converter of claim 19 , wherein the first switching element comprises a depletion mode transistor.
25. The power converter of claim 19 , wherein the timing logic implements the load powering phase after the bootstrap charging phase during a switching cycle of the power converter.
26. A power converter controller operable to control power provided to a load circuit coupled between a first voltage supply terminal and a first switching element by controlling the first switching element and to control power provided to an energy storage element coupled to the first switching element, the energy storage element being operable to provide a power supply, comprising:
a first control terminal for coupling to a control input of the first switching element;
a first load terminal coupled to the first switching element and the charge storing element;
a second switching element coupled between the first load terminal and a second voltage supply terminal; and
timing logic operable to selectively provide a control signal at the first control terminal to control the first switching element and to selectively control the second switching element to supply power to the load circuit during a load powering phase by enabling the first and second switching elements, charge the energy storage element during a bootstrap charging phase by enabling the first switching element and disabling the second switching element, and allowing the load circuit to operate in isolation during a passive phase by disabling at least the first switching element, wherein the timing logic comprises a pre-charge circuit including a resistor coupled between the first voltage supply terminal and a control terminal of the first switching element.
27. The power converter of claim 26 , further comprising a third switching element coupled between the energy storage element and the node.
28. The power converter of claim 27 , wherein the third switching element comprises a diode.
29. The power converter of claim 27 , wherein the timing logic is operable to enable the third switching element during the bootstrap charging phase.
30. The power converter of claim 26 , wherein the first switching element comprises an enhancement mode transistor.
31. The power converter of claim 26 , wherein the first switching element comprises a depletion mode transistor.
32. The power converter of claim 26 , wherein the timing logic implements the load powering phase after the bootstrap charging phase during a switching cycle of the power converter.