Capacitor converter

1 . A converter, comprising:

an input terminal;

an output terminal;

a rectifier connected between the input terminal and the output terminal;

a first switch;

a second switch connected to the output terminal and connected in series with the first switch at a first node;

a third switch connected to the output terminal and connected in series with the second switch at a second node;

a first leg comprising:

a first capacitor coupled to the first node; and

a first isolation switch connected between the first capacitor and the rectifier;

a second leg comprising:

a second capacitor coupled to the second node; and

a second isolation switch connected between the second capacitor and the rectifier; and

a controller configured to:

in a first mode, control switching of the first switch, the second switch, and the third switch to generate an output at the output terminal; and

in a second mode, open the second isolation switch, control the third switch in an always-on condition, and control switching of the first switch and the second switch to generate the output at the output terminal.

2 . The converter of claim 1 , wherein:

the controller is configured to:

generate the output according to a first conversion ratio in the first mode; and

generate the output according to a second conversion ratio different than the first conversion ratio in the second mode.

3 . The converter of claim 1 , wherein:

the first leg has a first inductance;

a capacitance of the first capacitor is determined such that a switch frequency used by the controller to control the first switch and the second switch is a resonant frequency of the first capacitor and the first inductance;

the first inductance comprises parasitic inductances within a first power loop connecting the input terminal to the output terminal; and

the first power loop comprises the first switch, the first leg, a rectifier switch in the rectifier, and traces connecting the first switch, the first leg, and the rectifier switch.

4 . The converter of claim 1 , wherein:

the first isolation switch connects the first leg to a first branch of the rectifier; and

the second isolation switch connects the second leg to a second branch of the rectifier.

5 . The converter of claim 1 , comprising:

a compensation inductor connected between the first leg and the second leg.

6 . The converter of claim 1 , comprising:

a fourth switch connected in series with the second switch at a third node between the first node and the second node;

a flying leg comprising:

a flying capacitor coupled to the third node; and

a third isolation switch connected between the flying capacitor and the rectifier.

7 . The converter of claim 6 , wherein:

the first isolation switch connects the first leg to a first branch of the rectifier;

the third isolation switch connects the flying leg to a second branch of the rectifier; and

the second isolation switch connects the second leg to the first branch of the rectifier.

8 . The converter of claim 6 , comprising:

a compensation inductor connected between the first leg and the flying leg.

9 . The converter of claim 6 , wherein:

the controller is configured to:

in the first mode, control switching of the fourth switch to generate the output at the output terminal;

in the second mode, control switching of the fourth switch to generate the output at the output terminal;

in a third mode, open the third isolation switch, control the third switch and the fourth switch in an always-on condition, and control switching of the first switch and the second switch to generate the output at the output terminal.

10 . A converter, comprising:

an input terminal;

an output terminal;

a rectifier connected between the input terminal and the output terminal;

a first switch;

a second switch connected to the output terminal and connected in series with the first switch at a first node;

a first resonant leg comprising:

a first resonant capacitor coupled to the first node; and

a first isolation switch connected between the first resonant capacitor and a first branch of the rectifier;

a third switch connected to the output terminal and connected in series with the second switch at a second node;

a flying leg comprising:

a flying capacitor coupled to the second node; and

a second isolation switch connected between the flying capacitor and a second branch of the rectifier;

a compensation inductor connected between the first resonant leg and the flying leg; and

a controller configured to control the first switch, the second switch, the third switch, and the rectifier to generate an output at the output terminal, wherein:

the controller is configured to:

in a first mode, control switching of the first switch, the second switch, and the third switch to generate an output at the output terminal; and

in a second mode, open the second isolation switch, control the third switch in an always-on condition, and control switching of the first switch and the second switch to generate the output at the output terminal.

11 . The converter of claim 10 , wherein:

the controller is configured to close the first isolation switch and the second isolation switch to set the conversion ratio to 3:1;

the controller is configured to close the first isolation switch, open the second isolation switch, and control the third switch in an always on condition to set the conversion ratio to 2:1; and

the controller is configured to open the first isolation switch and the second isolation switch, and control the first switch, the second switch, and the third switch in an always on condition to set the conversion ratio to 1:1.

12 . The converter of claim 11 , comprising:

a fourth switch connected to the output terminal and connected in series with the third switch at a third node; and

a second resonant leg comprising:

a second resonant capacitor coupled to the third node; and

a third isolation switch connected between the second resonant capacitor and the first branch of the rectifier; wherein:

the controller is configured to control the first switch, the second switch, the third switch, the fourth switch, and the rectifier to generate the output at the output terminal; and

the controller is configured to control at least one of the first switch, the second switch, the third switch, the fourth switch, the first isolation switch, the second isolation switch, or the third isolation switch to set the conversion ratio of the converter, wherein at least one of the second switch, the third switch, or the fourth switch is controlled in an always on condition and the first switch is controlled according to a switching signal to reduce the conversion ratio.

13 . The converter of claim 12 , wherein:

the controller is configured to close the first isolation switch, the second isolation switch, and the third isolation switch to set the conversion ratio to 4:1;

the controller is configured to close the first isolation switch and the second isolation switch, open the third isolation switch, and control the fourth switch in an always on condition to set the conversion ratio to 3:1;

the controller is configured to close the first isolation switch, open the second isolation switch and the third isolation switch, and control the third switch and the fourth switch in an always on condition to set the conversion ratio to 2:1; and

the controller is configured to open the first isolation switch, the second isolation switch, and the third isolation switch, and control the first switch, the second switch, the third switch, and the fourth switch in an always on condition to set the conversion ratio to 1:1.

14 . A method of controlling a converter, comprising:

controlling a first switch, a second switch connected in series at a first node and connected between an input terminal and an output terminal, and a third switch connected to the output terminal and connected in series with the second switch at a second node and controlling a rectifier connected to the output terminal to generate an output at the output terminal; and

controlling a first isolation switch connected between the rectifier and a first capacitor of a first leg connected to the first node and a second isolation switch connected between the rectifier and a second capacitor of a second leg connected to the second node to set a conversion ratio of the converter, wherein:

controlling the first switch, the second switch, and the third switch comprises:

in a first mode, controlling switching of the first switch, the second switch, and the third switch to generate an output at the output terminal; and

in a second mode, opening the second isolation switch, controlling the third switch in an always-on condition, and controlling switching of the first switch and the second switch to generate the output at the output terminal.

15 . The method of claim 14 , wherein:

controlling the first isolation switch comprises controlling the first isolation switch to connect the first leg to a first branch of the rectifier that is connected to a compensation inductor; and

controlling the second isolation switch comprises controlling the second isolation switch to connect the second leg to a second branch of the rectifier that is connected to the compensation inductor.

16 . The method of claim 15 , comprising:

closing the first isolation switch and the second isolation switch to set the conversion ratio to 3:1;

closing the first isolation switch, opening the second isolation switch, and controlling the third switch in an always on condition to set the conversion ratio to 2:1; and

opening the first isolation switch and the second isolation switch, and controlling the first switch, the second switch, and the third switch in an always on condition to set the conversion ratio to 1:1.

17 . The method of claim 14 , comprising:

controlling the first switch, the second switch, the third switch, and a fourth switch connected in series with the third switch at a third node to generate the output at the output terminal; and

controlling the first isolation switch, the second isolation switch, and a third isolation switch connected between the rectifier and a third capacitor of a third leg connected to the third node to set the conversion ratio of the converter, wherein

at least one of the second switch, the third switch, or the fourth switch is controlled in an always on condition and the first switch is controlled according to a switching signal to reduce the conversion ratio.

18 . The method of claim 17 , comprising:

closing the first isolation switch, the second isolation switch, and the third isolation switch to set the conversion ratio to 4:1;

closing the first isolation switch and the second isolation switch, opening the third isolation switch, and controlling the fourth switch in an always on condition to set the conversion ratio to 3:1;

closing the first isolation switch, opening the second isolation switch and the third isolation switch, and controlling the third switch and the fourth switch in an always on condition to set the conversion ratio to 2:1; and

opening the first isolation switch, the second isolation switch, and the third isolation switch, and controlling the first switch, the second switch, the third switch, and the fourth switch in an always on condition to set the conversion ratio to 1:1.

19 . The method of claim 17 , wherein:

controlling the first isolation switch comprises controlling the first isolation switch to connect the first leg to a first branch of the rectifier that is connected to a compensation inductor;

controlling the second isolation switch comprises controlling the second isolation switch to connect the second leg to a second branch of the rectifier that is connected to the compensation inductor; and

controlling the third isolation switch comprises controlling the third isolation switch to connect the third leg to the first branch of the rectifier.

20 . The method of claim 14 , comprising:

controlling the first switch, the second switch, the third switch, and a fourth switch connected in series between the second switch and the third switch at a third node between the first node and the second node to generate the output at the output terminal; and

controlling the first isolation switch, the second isolation switch, and a third isolation switch connected between the rectifier and a flying capacitor of a flying leg connected to the third node to set the conversion ratio of the converter, wherein:

to reduce the conversion ratio, at least one of the second switch, the third switch, or the fourth switch is controlled in an always on condition and the first switch is controlled according to a switching signal.