DC-DC converter and method for minimizing battery peak pulse loading

1. An electronic device, comprising a regulated DC-DC converter for converting a primary supply voltage into an output voltage at an output node to be coupled to a super capacitor and a control stage for operating the regulated DC-DC converter in a forward direction in a boost mode providing a boost voltage level at the output node and for operating the regulated DC-DC converter in a reverse direction, in which voltage at the output node is an input voltage, in a buck mode providing a buck voltage level at an auxiliary node which is between a primary voltage supply providing the primary supply voltage and the output node, wherein the control stage is adapted to control the regulated DC-DC converter when operating in reverse direction to provide a current to the auxiliary node using the super capacitor as power source.

2. The electronic device according to claim 1 , wherein the DC-DC converter operating in reverse direction is adapted to provide an amount of current to the auxiliary node sufficient for supplying a light-emitting semiconductor device coupled to the auxiliary node to produce a flash light.

3. The electronic device according to claim 2 , further comprising a current regulator coupled to the auxiliary node for regulating current through the light-emitting semiconductor device.

4. The electronic device according to claim 3 , wherein the control stage is further adapted to control the auxiliary voltage at the auxiliary node so as to minimize power losses, in particular so as to minimize voltage drop across the current regulator.

5. The electronic device according to claim 1 , further comprising a first switch coupled between the primary voltage supply and the auxiliary node for switching the path between auxiliary node and the primary voltage supply on for operating in forward direction and switching the path off for operating in reverse direction.

6. The electronic device according to claim 5 , wherein the first switch is a PMOS transistor, and the electronic device further comprises a fourth and a fifth switch for switching alternately the bulk of the first switch to either the voltage level at the auxiliary node or to the voltage level of the primary voltage supply.

7. A method of driving a load with a regulated DC-DC converter, the method comprising:

operating the regulated DC-DC converter in a forward direction in a boost mode for charging a super capacitor coupled to an output node, and wherein a control stage operates the regulated DC-DC converter in a reverse direction in a buck mode in which voltage at the output node is an input voltage for supplying the load connected at a point between an input voltage and the super capacitor with the super capacitor as a power source.

8. The method of claim 7 comprising providing an amount of current to the point sufficient for supplying a light-emitting semiconductor device coupled to the point to produce a flash light.

9. The method of claim 7 comprising coupling a first switch between the input voltage and the point for switching the path between point and the input voltage on for operating in forward direction and switching the path off for operating in reverse direction.

10. The method of claim 7 wherein the first switch is a PMOS transistor, and further comprising providing a fourth and a fifth switch for switching alternately the bulk of the first switch to either the voltage level at the point or to the voltage level of the input voltage.

11. The method of claim 7 comprising providing a current regulator coupled to the point for regulating current through a light-emitting semiconductor device.

12. The method of claim 11 wherein the control stage is further adapted to control an auxiliary voltage at the point so as to minimize power losses, in particular so as to minimize voltage drop across the current regulator.