Switched capacitor converters for wireless power transfer
A wireless power receiver can include a receiver coil, with first and second rectifiers having respective inputs coupled respective terminals of the receiver coil, a first cascade of rectifier driven switched capacitor (RDSC) cells coupled between an output of the first rectifier and an output bus, and a second cascade of RDSC cells coupled between an output of the second rectifier and the output bus. A wireless power transmitter can include a first cascade of inverter driver switched capacitor (IDSC) cells coupled between a DC input bus and an input of a first inverter, a second cascade of one or more IDSC cells coupled between the DC input bus and an input of a second inverter, and a transmitter coil having a first terminal coupled to an output of the first inverter and a second terminal coupled to an output of the second inverter.
1 . A wireless power transmitter comprising:
a first cascade of two or more inverter driver switched capacitor (IDSC) cells coupled between a DC input bus and an input of a first inverter, each IDSC cell comprising a flying capacitor and a plurality of associated switching devices;
a second cascade of two or more IDSC cells coupled between the DC input bus and an input of a second inverter, each IDSC cell comprising a flying capacitor and a plurality of associated switching devices; and
a wireless power transmitter coil having a first terminal coupled to an output of the first inverter and a second terminal coupled to an output of the second inverter;
whereby the first and second cascades of IDSC cells allow selecting a voltage or current conversion ratio based on at least one of DC input bus voltage or other operating condition to reduce losses.
2 . The wireless power transmitter of claim 1 wherein for each IDSC cell:
the flying capacitor has a first terminal coupled to an input of the IDSC cell and a second terminal; and
the plurality of switching devices include:
a top switch having a first terminal coupled to the input of the IDSC cell and the first terminal of the flying capacitor and a second terminal coupled to a first output terminal of the IDSC cell, thereby allowing the top switch to selectively couple first terminal of the flying capacitor to the first output terminal of the IDSC cell;
a middle switch having a first terminal coupled to a second output terminal of the IDSC cell and a second terminal coupled to the second terminal of the flying capacitor, thereby allowing the middle switch to selectively couple the second terminal of the flying capacitor to the second output terminal of the IDSC cell; and
a bottom switch having a first terminal coupled to the second terminal of the flying capacitor and the second terminal of the middle switch and a second terminal coupled to ground, thereby allowing the bottom switch to selectively couple the second terminal of the flying capacitor to ground.
3 . The wireless power transmitter of claim 2 wherein each IDSC cell further comprises:
a diode having its anode coupled to the second terminal of the flying capacitor and its cathode coupled to the wireless power transmitter coil.
4 . The wireless power transmitter of claim 3 wherein:
the first cascade of two or more IDSC cells further comprises:
a first upstream IDSC cell having its input terminal coupled to the DC input bus and its first output terminal coupled to the input of the first inverter; and
a first downstream IDSC cell having its input terminal coupled to the second output terminal of the first upstream IDSC cell and its first and second output terminals coupled to the input of the first inverter; and
the second cascade of two or more IDSC cells further comprises:
a second upstream IDSC cell having its input terminal coupled to the DC input bus and its first output terminal coupled to the input of the second inverter; and
a second downstream IDSC cell having its input terminal coupled to the second output terminal of the second upstream IDSC cell and its first and second output terminals coupled to the input of the second inverter.
5 . The wireless power transmitter of claim 4 wherein the first and second cascades of IDSC cells each further comprise one or more intermediate IDSC cells, with each intermediate IDSC cell having its input terminal coupled to an immediately upstream IDSC cell, its first output terminal coupled to the input of either the first or second inverter, and its second output terminal coupled to an immediately downstream IDSC cell.
6 . The wireless power transmitter of claim 2 wherein:
the first cascade of two or more IDSC cells further comprises:
a first upstream IDSC cell having its input terminal coupled to the DC input bus and its first output terminal coupled to the input of the first inverter; and
a first downstream IDSC cell having its input terminal coupled to the second output terminal of the first upstream IDSC cell and its first and second output terminals coupled to the input of the first inverter; and
the second cascade of two or more IDSC cells further comprises:
a second upstream IDSC cell having its input terminal coupled to the DC input bus and its first output terminal coupled to the input of the second inverter; and
a second downstream IDSC cell having its input terminal coupled to the second output terminal of the second upstream IDSC cell and its first and second output terminals coupled to the input of the second inverter.
7 . The wireless power transmitter of claim 6 wherein the first and second cascades of IDSC cells each further comprise one or more intermediate IDSC cells, with each intermediate IDSC cell having its input terminal coupled to an immediately upstream IDSC cell, its first output terminal coupled to the input of either the first or second inverter, and its second output terminal coupled to an immediately downstream IDSC cell.
8 . A wireless power transmitter comprising:
first cascade of two or more inverter driver switched capacitor (IDSC) cells coupled between a DC input bus and an input of a first inverter;
a second cascade of two or more IDSC cells coupled between the DC input bus and an input of a second inverter; and
a wireless power transmitter coil having a first terminal coupled to an output of the first inverter and a second terminal coupled to an output of the second inverter; and
control circuitry that:
operates the first cascade of two or more IDSC cells in a series mode to cause the first and second inverters to produce a positive half cycle and in a parallel mode to cause the first and second inverters to produce a negative half cycle; and
operates the second cascade of two or more IDSC cells in a series mode to cause the first and second inverters to produce a negative half cycle and in a parallel mode to cause the first and second inverters to produce a positive half cycle.
9 . The wireless power transmitter of claim 8 wherein the control circuitry sequences switching of switching devices of each cascade of IDSC cells to achieve zero voltage switching.
10 . The wireless power transmitter of claim 9 wherein the control circuitry sequences switching of a cascade of IDSC cells undergoing a parallel mode to series mode transition to achieve zero voltage switching by:
simultaneously turning off all top and bottom switches of the cascade of IDSC cells undergoing a parallel mode to series mode transition;
turning off a low side switch of a corresponding inverter;
turning on a high side switch of a corresponding inverter; and
subsequently turning on middle switches of the IDSC cells in sequence from downstream to upstream.
11 . The wireless power transmitter of claim 10 wherein the control circuitry subsequently turns on middle switches of the IDSC cells upon their body diode conduction.
12 . The wireless power transmitter of claim 9 wherein the control circuitry sequences switching of a cascade of IDSC cells undergoing a parallel mode to series mode transition by:
turning off a low side switch of a corresponding inverter;
turning on a high side switch of a corresponding inverter; and
subsequently turning on middle switches of the IDSC cells in sequence from downstream to upstream.
13 . The wireless power transmitter of claim 9 wherein the control circuitry sequences switching of a cascade of IDSC cells undergoing a series mode to parallel mode transition by:
turning off a middle switch of a most upstream IDSC cell in the cascade of IDSC cells undergoing a series mode to parallel mode transition;
turning on a bottom switch of the most downstream IDSC cell upon its body diode conduction, and then turning on a top switch of the most downstream IDSC cell;
turning off a middle switch of an adjacent downstream IDSC cell;
turning on a bottom switch of the adjacent downstream IDSC cell upon its body diode conduction, and then turning on a top switch of the adjacent downstream IDSC cell; and
turning on a low side switch of a corresponding inverter.
14 . The wireless power transmitter of claim 9 wherein the control circuitry sequences switching of a cascade of IDSC cells undergoing a series mode to parallel mode transition by:
simultaneously turning off a middle switch of all IDSC cells in the cascade of IDSC cells undergoing a series mode to parallel mode transition and turning off a high side switch of an inverter corresponding to the cascade of IDSC cells;
simultaneously turning on a bottom switch and a top switch of each IDSC cell in the cascade of RDSC cells undergoing a series mode to parallel mode transition; and
turning on a low side switch of an inverter corresponding to the cascade of IDSC cells undergoing a series mode to parallel mode transition.
15 . The wireless power transmitter of claim 14 :
wherein waiting for the coil current to discharge a voltage on a second terminal of each flying capacitor through an auxiliary diode of each IDSC cell after simultaneously turning off the middle switch of all IDSC cells and turning off a high switch of the inverter; and
wherein simultaneously turning on the bottom switch and the top switch of each IDSC cell occurs upon completion of discharging the voltage on the second terminal of each flying capacitor.