High Performance Variable Ratio Switched Capacitor Power Converter

Abstract

An apparatus comprises a switch-capacitor network, a power-switch network and a controller. The switch-capacitor network has a plurality of control switches and a plurality of flying capacitors, where the control switches are configured to connect two of the flying capacitors in series in a first configuration and in parallel in a second configuration. The power-switch network has a plurality of power switches and is coupled between an input port having an input voltage and an output port having an output voltage, where the power switches are configured to couple the switch-capacitor network to the input port and the output port in different ways during a charging phase and a discharging phase. The controller is configured to operate the control switches to configure the switch-capacitor network into different configurations during the charging phase or the discharging phase such that a ratio of the output voltage over the input voltage is changed in an operation mode.

What is claimed is: 
     
         1 . An apparatus comprising:
 a switch-capacitor network comprising a plurality of control switches and a plurality of flying capacitors, wherein the control switches are configured to connect two of the flying capacitors in series in a first configuration and in parallel in a second configuration;   a power-switch network comprising a plurality of power switches and coupled between an input port having an input voltage and an output port having an output voltage, wherein the power-switch network is configured to couple the switch-capacitor network to the input port and the output port in different ways in a charging phase and in a discharging phase; and   a controller configured to operate the control switches to configure the switch-capacitor network into different configurations during the charging phase or during the discharging phase in an operation mode, such that a ratio of the output voltage over the input voltage is variable through changing configurations of the switch-capacitor network in the charging phase or in the discharging phase.   
     
     
         2 . The apparatus of  claim 1 , further comprising a plurality of auxiliary inductors coupled to the flying capacitors, wherein the power switches and the control switches are controlled with a phase shift and a current of at least one auxiliary inductor reverses a direction during a transition to enable some of the power switches or control switches to be switched in a soft-switching condition. 
     
     
         3 . The apparatus of  claim 2 , wherein the duration of the phase shift is adjusted when a load of the apparatus, the input voltage or the output voltage changes. 
     
     
         4 . The apparatus of  claim 1 , wherein the output voltage is adjusted by changing the switching frequency of the apparatus. 
     
     
         5 . The apparatus of  claim 1 , wherein a duty cycle of at least one of the power switches is adjusted to reduce a ripple current or a power loss of one of the flying capacitors or the power switches. 
     
     
         6 . The apparatus of  claim 1 , wherein some of the power switches and the control switches operate in a linear mode, and wherein the control switches are configured to reduce a power loss of the apparatus. 
     
     
         7 . The apparatus of  claim 1 , wherein the ratio of the output voltage and the input voltage is adjusted to improve a performance of a system employing the apparatus. 
     
     
         8 . The apparatus of  claim 1 , wherein the switch-capacitor network comprises a first switch-capacitor branch and a second switch-capacitor branch, and wherein:
 the first switch-capacitor branch comprises a first control switch of the plurality of control switches in series with a first flying capacitor of the plurality of flying capacitors through a first mid junction, wherein a first terminal of the first flying capacitor is coupled to a first flying power rail, a second terminal of the first flying capacitor is coupled to a first power terminal of the first control switch through the first mid junction, and a second power terminal of the first control switch is coupled to a second flying power rail;   the second switch-capacitor branch comprises a second control switch of the plurality of control switches in series with a second flying capacitor of the plurality of flying capacitors through a second mid junction, wherein a first power terminal of the second control switch is coupled to the first flying power rail, a second power terminal of the second control switch is coupled to a first terminal of the second flying capacitor through the second mid junction, and a second terminal of the second flying capacitor is coupled to the second flying power rail; and   a third control switch of the plurality of control switches is coupled between the first mid junction and the second mid junction.   
     
     
         9 . The apparatus of  claim 8 , wherein the switch-capacitor network further comprises a third switch-capacitor branch having a fourth control switch of the plurality of control switches in series with a third flying capacitor of the plurality of flying capacitors through a third mid junction, and wherein:
 a first power terminal of the fourth control switch is coupled to the first flying power rail;   a second power terminal of the fourth control switch is coupled to a first terminal of the third flying capacitor through the third mid junction;   a second terminal of the third flying capacitor is coupled to a third flying power rail;   a fifth control switch of the plurality of control switches is coupled between the second flying power rail and the third junction; and   a sixth control switch of the plurality of control switches is coupled between the second flying power rail and the third flying power rail.   
     
     
         10 . The apparatus of  claim 1 , wherein two of the power switches form a first half bridge between the input port and the output port, and another two of the power switches form a second half bridge across the input port or the output port, and wherein the switch-capacitor network is coupled between a switch node of the first half bridge and a switch node of the second half bridge. 
     
     
         11 . A system comprising:
 a switch-capacitor network comprising a plurality of control switches and a plurality of flying capacitors, wherein the control switches are configured to connect two of the flying capacitors in series in a first configuration and in parallel in a second configuration;   a power-switch network comprising a plurality of power switches and coupled between an input port having an input voltage and an output port having an output voltage, wherein the power-switch network is configured to couple the switch-capacitor network to the input port and the output port in different ways in a charging phase and in a discharging phase; and   a controller configured to operate the control switches to configure the switch-capacitor network into different configurations during the charging phase or during the discharging phase in an operation mode, such that a ratio of the output voltage over the input voltage is changed through changing configurations of the switch-capacitor network in the charging phase or in the discharging phase such that a performance of the system is improved.   
     
     
         12 . The system of  claim 11 , further comprising a plurality of auxiliary inductors coupled to the flying capacitors, wherein the power switches and the control switches are controlled with a phase shift and a current of at least one auxiliary inductor reverses a direction during a transition to enable a plurality of the power switches and control switches to be switched in a soft-switching condition. 
     
     
         13 . The system of  claim 11 , wherein the controller is configured to change a switching frequency of the power switches. 
     
     
         14 . The system of  claim 11 , wherein two of the power switches form a first half bridge between the input port and the output port, and another two of the power switches form a second half bridge across the input port or the output port, and wherein the switch-capacitor network is coupled between a switch node of the first half bridge and a switch node of the second half bridge. 
     
     
         15 . The system of  claim 11 , wherein the switch-capacitor network comprises a first switch-capacitor branch and a second switch-capacitor branch, and wherein:
 the first switch-capacitor branch comprises a first control switch of the plurality of control switches in series with a first flying capacitor of the plurality of flying capacitors through a first mid junction, wherein a first terminal of the first flying capacitor is coupled to a first flying power rail, a second terminal of the first flying capacitor is coupled to a first power terminal of the first control switch through the first mid junction, and a second power terminal of the first control switch is coupled to a second flying power rail;   the second switch-capacitor branch comprises a second control switch of the plurality of control switches in series with a second flying capacitor of the plurality of flying capacitors through a second mid junction, wherein a first power terminal of the second control switch is coupled to the first flying power rail, a second power terminal of the second control switch is coupled to a first terminal of the second flying capacitor through the second mid junction, and a second terminal of the second flying capacitor is coupled to the second flying power rail; and   a third control switch of the plurality of control switches is coupled between the first mid junction and the second mid junction.   
     
     
         16 . The system of  claim 11 , further comprises a first resonator having a first coil and a second resonator having a second coil magnetically coupled to the first coil, and wherein the second resonator is coupled to the input port, and the ratio of the output voltage over the input voltage is adjusted in response to a change of a system frequency, a magnetic coupling strength between the first coil and the second coil, a voltage or a current to the load of the system, or a power loss or temperature of a component in the system. 
     
     
         17 . A method comprising:
 arranging a plurality of control switches and a plurality of flying capacitors into a switch-capacitor network, wherein the control switches are configured to connect two of the flying capacitors in series in a first configuration and in parallel in a second configuration;   coupling a power-switch network with a plurality of power switches between an input port having an input voltage and an output port having an output voltage, and configuring the power-switch network to couple the switch-capacitor network to the input port and the output port in different ways in a charging phase and in a discharging phase; and   operating the control switches to configure the switch-capacitor network into different configurations during the charging phase or during the discharging phase in an operation mode, such that a ratio of the output voltage over the input voltage is changed through changing configurations of the switch-capacitor network in the charging phase or in the discharging phase.   
     
     
         18 . The method of  claim 17 , wherein the power-switches network comprises a first half bridge coupled between the input port and the output port, and a second half bridge coupled across the input port or the output port, and wherein the switch-capacitor network is coupled between a switch node of the first half bridge and a switch node of the second half bridge. 
     
     
         19 . The method of  claim 17 , further comprising coupling a plurality of auxiliary inductors to the flying capacitors in the switch-capacitor network, and controlling the power switches and the control switches with a phase shift such that a current of one of the auxiliary inductors reverses a direction during a transition to enable some of the power switches or the control switches to be switched in a soft-switching condition. 
     
     
         20 . The method of  claim 17 , wherein the switch-capacitor network comprises a first switch-capacitor branch and a second switch-capacitor branch, and wherein:
 the first switch-capacitor branch comprises a first control switch of the plurality of control switches in series with a first flying capacitor of the plurality of flying capacitors through a first mid junction, wherein a first terminal of the first flying capacitor is coupled to a first flying power rail, a second terminal of the first flying capacitor is coupled to a first power terminal of the first control switch through the first mid junction, and a second power terminal of the first control switch is coupled to a second flying power rail;   the second switch-capacitor branch comprises a second control switch of the plurality of control switches in series with a second flying capacitor of the plurality of flying capacitors through a second mid junction, wherein a first power terminal of the second control switch is coupled to the first flying power rail, a second power terminal of the second control switch is coupled to a first terminal of the second flying capacitor through the second mid junction, and a second terminal of the second flying capacitor is coupled to the second flying power rail; and   a third control switch of the plurality of control switches is coupled between the first mid junction and the second mid junction.