Resonant switched capacitor converter

1 . A DC-DC power converter having a ground terminal, an input terminal for receiving an input voltage and an output terminal for providing an output voltage with a target conversion ratio, the DC-DC power converter comprising:

a coupled inductor having a first winding and a second winding coupled to the output terminal;

a first flying capacitor coupled to a first inductor and to the second winding;

a second flying capacitor coupled to a second inductor and to the first winding;

an input capacitor coupling the input terminal to the ground terminal;

an output capacitor coupling the output terminal to the ground terminal;

a network of switches; and

a driver adapted to drive the network of switches with a sequence of states during a drive period, wherein the sequence of states forms a switching cycle comprising a first phase and a second phase,

wherein:

the first phase of the switching cycle comprises a first state and a second state;

in the first state of the first phase, the input terminal is coupled to the input terminal via a path comprising the first flying capacitor, the first inductor, the second winding, the output capacitor and the input capacitor; and the ground terminal is coupled to the ground terminal via two paths, a first path comprising the second inductor, the second flying capacitor, the second winding, and the output capacitor, and a second path comprising the first winding and the output capacitor;

in the second state of the first phase, the input terminal is coupled to the input terminal via a path comprising the second flying capacitor, the second inductor, the first winding, the output capacitor and the input capacitor; and the ground terminal is coupled to the ground terminal via two paths a first path comprising the first inductor, the first flying capacitor, the first winding, and the output capacitor, and a second path comprising the second winding and the output capacitor;

the second phase of the switching cycle comprises a third state and a fourth state;

in the third state of the second phase, the ground terminal is coupled to the ground terminal via a path comprising the first winding and the output capacitor;

in the fourth state of the second phase, the ground terminal is coupled to the ground terminal via a path comprising the second winding and the output capacitor;

the network of switches comprises:

a first input switch to couple the first flying capacitor to the input terminal;

a second input switch to couple the second flying capacitor to the input terminal;

a first capacitor switch to couple the first flying capacitor to the first winding;

a second capacitor switch to couple the second flying capacitor to the second winding;

a first ground switch to couple the first winding to the ground terminal; and

a second ground switch to couple the second winding to the ground terminal,

wherein each switch in the network of switches is configured to be in either an on-state or an off-state; and

in the third state of the second phase, the first ground switch is in the on-state and the other remaining switches are in the off-state.

2 . The DC-DC power converter as claimed in claim 1 , wherein in the first state the first input switch, the second capacitor switch and the first ground switch are in the on-state, while the second input switch, the first capacitor switch and the second ground switch are in the off-state.

3 . The DC-DC power converter as claimed in claim 1 , wherein in the second state, the first capacitor switch, the second input switch, and the second ground switch are in the on-state and the first input switch, the second capacitor switch and the first ground switch are in the off-state.

4 . The DC-DC power converter as claimed in claim 1 , wherein in the fourth state the second ground switch is in the on-state and the other remaining switches are in the off-state.

5 . The DC-DC power converter of claim 1 wherein the first flying capacitor coupled to the first inductor forms a first resonant tank; and wherein the second flying capacitor coupled to the second inductor forms a second resonant tank.

6 . The DC-DC power converter of claim 1 wherein the first inductor and the second inductor form a coupled inductor.

7 . The DC-DC power converter of claim 1 further comprising a third inductor connected in parallel to the coupled inductor.

8 . The DC-DC power converter as claimed in claim 1 , wherein the driver comprises at least a first control panel and a second control panel, the first control panel being configured to control a first portion of the network of switches using at least one pulse width modulation (PWM) signals, and the second control panel being configured to control a second portion of the network of switches using at least one resonant frequency associated with the DC-DC power converter.

9 . The DC-DC power converter as claimed in claim 1 , wherein the driver is configured to operate in a first mode during the first phase and a second mode during the second phase, wherein the first mode is a soft-switching mode and the second mode is a hard-switching mode.

10 . The DC-DC power converter as claimed in claim 9 , wherein the soft-switching mode is a resonant mode comprising at least one of a zero voltage and a zero current switching mode.

11 . The DC-DC power converter as claimed in claim 10 , wherein the driver is configured to drive the first input switch, the second input switch, the first capacitor switch, and the second capacitor switch using the zero voltage switching; and the first ground switch and the second ground switch using the zero current switching mode.

12 . The DC-DC power converter as claimed in claim 10 , wherein the hard-switching mode comprises a pulse width modulation mode.

13 . The DC-DC power converter as claimed in claim 10 ,

wherein the driver comprises a controller having a compensator circuit coupled to a pulse width modulation generator configured to generate two pulse width modulation signals, and

wherein the compensator circuit is configured to receive the output voltage and provide a compensated output voltage signal to the pulse width modulation generator.

14 . A method of operating a DC-DC power converter having a ground terminal, an input terminal for receiving an input voltage and an output terminal for providing an output voltage with a target conversion ratio; the method comprising:

providing a coupled inductor having a first winding and a second winding coupled to the output terminal;

providing a first flying capacitor coupled to a first inductor and the second winding;

providing a second flying capacitor coupled to a second inductor and the first winding;

providing an input capacitor coupling the input terminal to the ground terminal;

providing an output capacitor coupling the output terminal to the ground terminal;

providing a network of switches;

driving the network of switches with a sequence of states, wherein the sequence of states forms a switching cycle with a first phase and a second phase,

wherein:

the first phase of the switching cycle comprises a first state and a second state;

in the first state of the first phase, the method further comprising coupling the input terminal to the input terminal via a path comprising the first flying capacitor, the first inductor, the second winding, the output capacitor and the input capacitor; and the ground terminal is coupled to the ground terminal via two paths, a first path comprising the second inductor, the second flying capacitor, the second winding, and the output capacitor, and a second path comprising the first winding and the output capacitor;

in the second state of the first phase, the method further comprising coupling the input terminal to the input terminal via a path comprising the second flying capacitor, the second inductor, the first winding, the output capacitor and the input capacitor; and the ground terminal is coupled to the ground terminal via two paths a first path comprising the first inductor, the first flying capacitor, the first winding, and the output capacitor, and a second path comprising the second winding and the output capacitor;

the second phase of the switching cycle comprises a third state and a fourth state;

in the third state of the second phase, the method further comprising coupling the ground terminal to the ground terminal via a path comprising the first winding and the output capacitor;

in the fourth state of the second phase, the method further comprising coupling the ground terminal to the ground terminal via a path comprising the second winding and the output capacitor;

the network of switches comprises:

a first input switch to couple the first flying capacitor to the input terminal;

a second input switch to couple the second flying capacitor to the input terminal;

a first capacitor switch to couple the first flying capacitor to the first winding;

a second capacitor switch to couple the second flying capacitor to the second winding;

a first ground switch to couple the first winding to the ground terminal; and

a second ground switch to couple the second winding to the ground terminal;

the method further comprising configuring each switch in the network of switches to be in either an on-state or an off-state; and

in the third state of the second phase, the method further comprising configuring the first ground switch to the on-state and maintaining the other remaining switches in the off-state.

15 . The method as claimed in claim 14 , wherein driving the network of switches comprises:

controlling a first portion of the network of switches using at least one pulse width modulation (PWM) signals; and

controlling a second portion of the network of switches using at least one resonant frequency associated with the DC-DC power converter.

16 . The method as claimed in claim 14 comprising driving the network of switches using with a soft-switching mode during the first phase, and a hard-switching mode during the second phase.

17 . The method as claimed in claim 16 , wherein the soft-switching mode is a resonant mode, and the hard-switching mode is a pulse width modulation mode.