System and method for powering a switching converter
A circuit and method for regulating an internal power supply of a switching converter is presented. A switching converter with a depletion mode power switch coupled to an enhancement mode power switch via a switching node and an energy storing element coupled to the depletion mode power switch is provided. The energy storing element may be adapted to provide energy to the switching converter. For instance, the energy storing element may be a capacitor. Optionally, the switching converter may comprise an inductor coupled to the depletion mode transistor, the inductor being adapted to provide an inductor current.
1. A switching converter comprising:
a depletion mode power switch coupled to an enhancement mode power switch via a switching node;
an energy storing element coupled to the depletion mode power switch via a first path; wherein the first path comprises a resistance; and
a second path coupling the depletion mode power switch to the energy storing element, the second path comprising a coupling switch.
2. The switching converter as claimed in claim 1 , comprising an inductor coupled to the depletion mode transistor, the inductor being adapted to provide an inductor current.
3. The switching converter as claimed in claim 1 , wherein the first path comprises another coupling switch.
4. The switching converter as claimed in claim 3 , wherein the resistance comprises an internal resistance of the said another coupling switch.
5. The switching converter as claimed in claim 3 , wherein the said another coupling switch is a depletion mode transistor.
6. The switching converter as claimed in claim 1 , wherein the converter is adapted to charge the energy storing element via the first path in a first mode of operation, and via the second path in a second mode of operation.
7. The switching converter as claimed in claim 1 , wherein the enhancement mode power switch and the depletion mode power switch are arranged such that switching the enhancement mode power switch off turns the depletion mode power switch off, and switching the enhancement mode power switch on turns the depletion mode power switch on.
8. The switching converter as claimed in claim 1 , wherein the depletion mode power switch comprises a parasitic capacitance, and wherein when the enhancement mode power switch is switched off a capacitive current associated with the parasitic capacitance charges the energy storing element via the second path.
9. The switching converter as claimed in claim 6 , wherein when the enhancement mode power switch is switched on an inductor current charges the energy storing element via the second path.
10. The switching converter as claimed in claim 1 , comprising a capacitor connected in parallel to the depletion mode power switch.
11. The switching converter as claimed in claim 1 , comprising a control circuit coupled to the enhancement mode power switch, wherein the energy storing element is adapted to provide energy to the control circuit.
12. The switching converter as claimed in claim 1 , comprising a protection circuit adapted to limit a voltage across the depletion mode power switch.
13. The switching converter as claimed in claim 12 , wherein the protection circuit comprises a Zener diode or a depletion mode transistor couple to the energy storing element.
14. The switching converter as claimed in claim 1 , wherein the depletion mode power switch is based on a III/V semiconductor.
15. A method of powering a switching converter comprising an energy storing element, the method comprising the steps of:
providing a depletion mode power switch coupled to an enhancement mode power switch via a switching node;
charging the energy storing element via a first path coupling the depletion mode power switch to the energy storing element, wherein the first path comprises a resistance; and
providing a second path coupling the depletion mode power switch to the energy storing element, wherein the second path comprises a coupling switch.
16. The method as claimed in claim 15 , further comprising the steps of: charging the energy storing element via the first path in a first mode of operation, and charging the energy storing element via the second path in a second mode of operation.
17. The method as claimed in claim 15 , wherein the depletion mode power switch comprises a parasitic capacitance, the method comprising switching the enhancement mode power switch off to turn the depletion mode power switch off, and charging the energy storing element using a capacitive current associated with the parasitic capacitance via the second path.
18. The method as claimed in claim 15 , further comprising the steps of: providing an inductor current and switching the enhancement mode power switch on to turn the depletion mode power switch on, such that the inductor current charges the energy storing element via the second path.