Double-Sided LCLC-Compensated Topology For Capacitive Power Transfer

• US 20160294217A1
• Filed: 04/01/2016
• Published: 10/06/2016
• Est. Priority Date: 04/01/2015
• Status: Active Grant

• Current Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Original Assignee: Board of Regents of the University of Michigan (University of Michigan)
• Inventors: MI, Chris, ZHANG, Hua, LU, Fei
• Granted Patent: US 10,298,057 B2
• Time in Patent Office: Days
• US Class Current: 1/1
• CPC Class Codes: H02J 2207/20 Charging or discharging characterised by the power electronics converter
• CPC Class Codes: H02J 50/05 using capacitive coupling
• CPC Class Codes: H02J 50/90 involving detection or optimisation of position, e.g. alignment
• CPC Class Codes: H02J 7/00 Circuit arrangements for charging or depolarising batteries or for supplying loads from batteries
• CPC Class Codes: H02J 7/00034 Charger exchanging data with an electronic device, i.e. telephone, whose internal battery is under charge

Abstract

A double-sided LCLC-compensated network is proposed for a capacitive power transfer (CPT) system. In one design, four metal plates are used to form two power transmitting and receiving capacitors and the LCLC network is used to compensate the capacitors. In the second design, two extra metal plates are used to couple with the previous four plates at the transmitting and receiving side, respectively, which forms the capacitor-integrated structure. The circuit parameter values are tuned to achieve zero voltage switching (ZVS) of the input side switches. There is also a CLLC topology proposed, which is a similar variation of LCLC circuit. A 3.3 kW input power capacitive power transfer prototype is designed and built. The experiment results show that the proposed CPT system can transfer 3.1 kW output power through an air gap distance of 70 mm with a dc-to-dc efficiency of 92.1%.

Claims

1. A wireless power transfer system, comprising:

a pair of coupling capacitors, each coupling capacitor having an input terminal and an output terminal;

a send unit configured to transfer power capacitively through the pair of coupling capacitors, wherein the send unit includes;

an inverter configured to receive a DC input signal and convert the DC input signal to an AC input signal at a desired resonant frequency;

a send side compensation circuit interconnecting the inverter with the pair of coupling capacitors, wherein the send side compensation circuit is comprised of two bypass capacitors and each bypass capacitor is connected in parallel between input terminals of the pair of coupling capacitors; and

a receive unit configured to receive power via the pair of coupling capacitors from the send unit, wherein the receive unit includes

a receive side converter configured to receive an AC charging signal from the pair of coupling capacitors and convert the AC charging signal to a DC charging signal; and

a receive side compensation circuit interconnecting the pair of coupling capacitors with the receive side converter, wherein the receive side compensation circuit is comprised of two bypass capacitors and each bypass capacitor is connected is connected in parallel between output terminals of the pair of coupling capacitors, wherein capacitance of each of the bypass capacitors is at least five times larger than capacitance of each of the coupling capacitors.

2. The wireless power transfer system of claim 1 wherein the four bypass capacitors are at least ten times larger than the coupling capacitors.

3. The wireless power transfer system of claim 1 wherein the send side compensation circuit is defined as two LC circuits coupled in series.

4. The wireless power transfer system of claim 3 wherein the receive side compensation circuit is symmetric with the send side compensation circuit.

5. The wireless power transfer system of claim 1 wherein the inverter is further defined as a full bridge converter circuit comprised of four switches or a half-bridge converter circuit comprised of two switches.

6. The wireless power transfer system of claim 5 further comprises a controller electrically coupled to the four switches and operates to turn the switches on and off at a zero voltage switching condition.

7. The wireless power transfer system of claim 1 wherein the receive side converter is further defined as a full wave rectifier circuit.

8. The wireless power transfer system of claim 7 further comprises a battery configured to receive the DC charging signal from the receive side converter.

9. The wireless power transfer system of claim 8 wherein the receive unit is integrated into a vehicle.

10. A compensation circuit for a capacitive power transfer system having a first coupling capacitor and a second coupling capacitor, comprising:

a first bypass capacitor electrically coupled in parallel between input terminals of the first and second coupling capacitors;

a first inductor having an input terminal and an output terminal, wherein the output terminal of the first inductor is electrically coupled at a first node to the input terminal of the first coupling capacitor;

a second inductor having an input terminal and an output terminal, wherein the output terminal of the second inductor is electrically coupled at a second node to the input terminal of the first inductor; and

a second bypass capacitor electrically coupled in parallel with the first bypass capacitor, wherein one terminal of the second bypass capacitor is electrically coupled to the second node.

11. The compensation circuit of claim 10 wherein capacitance of the first bypass capacitor and capacitance of the second bypass capacitor are at least five times larger than capacitance of each of the coupling capacitors.

12. The compensation circuit of claim 10 further comprises

a third bypass capacitor electrically coupled in parallel between output terminals of the first and second coupling capacitors;

a third inductor having an input terminal and an output terminal, wherein the input terminal of the third inductor is electrically coupled at a third node to the output terminal of the first coupling capacitor;

a fourth inductor having an input terminal and an output terminal, wherein the input terminal of the fourth inductor is electrically coupled at a fourth node to the output terminal of the third inductor; and

a fourth bypass capacitor electrically coupled in parallel with the third bypass capacitor, wherein one terminal of the fourth bypass capacitor is electrically coupled to the fourth node.

13. A wireless power transfer system, comprising:

a pair of coupling capacitors, each coupling capacitor having an input terminal and an output terminal;

a send unit configured to transfer power capacitively through the pair of coupling capacitors, wherein the send unit includes;

an inverter configured to receive a DC input signal and operates to convert the DC input signal to an AC input signal at a desired resonant frequency;

a send side compensation circuit interconnecting the inverter with the pair of coupling capacitors, wherein the send side compensation circuit includes;

a first bypass capacitor electrically coupled in parallel between input terminals of the pair of coupling capacitors;

a first inductor having an input terminal and an output terminal, wherein the output terminal of the first inductor is electrically coupled at a first node to the input terminal of one of the pair of coupling capacitors;

a second inductor having an input terminal and an output terminal, wherein the output terminal of the second inductor is electrically coupled at a second node to the input terminal of the first inductor; and

a second bypass capacitor electrically coupled in parallel with the first bypass capacitor, wherein one terminal of the second bypass capacitor is electrically coupled to the second node.

14. The wireless power transfer system of claim 13 wherein capacitance of the first bypass capacitor and capacitance of the second bypass capacitor are at least five times larger than capacitance of each of the coupling capacitors.

15. The wireless power transfer system of claim 13 wherein the inverter is further defined as a full bridge converter circuit comprised of four switches or a half-bridge converter circuit comprised of two switches.

16. The wireless power transfer system of claim 15 further comprises a controller electrically coupled to the four switches and operates to turn the switches on and off at a zero voltage switching condition.

17. The wireless power transfer system of claim 13 further comprises

a receive unit configured to receive power via the pair of coupling capacitors from the send unit, wherein the receive unit includes

a receive side converter configured to receive an AC charging signal from the pair of coupling capacitors and convert the AC charging signal to a DC charging signal;

and

a receive side compensation circuit interconnecting the receive coil with the receive side converter.

18. The wireless power transfer system of claim 17 wherein the receive side converter is further defined as a full wave rectifier circuit.

19. The wireless power transfer system of claim 17 wherein the receive unit is integrated into a vehicle.

20. The wireless power transfer system of claim 17 wherein the receive side compensation circuit includes

a third bypass capacitor electrically coupled in parallel between output terminals of the first and second coupling capacitors;

a third inductor having an input terminal and an output terminal, wherein the input terminal of the third inductor is electrically coupled at a third node to the output terminal of the first coupling capacitor;

a fourth inductor having an input terminal and an output terminal, wherein the input terminal of the fourth inductor is electrically coupled at a fourth node to the output terminal of the third inductor; and

a fourth bypass capacitor electrically coupled in parallel with the third bypass capacitor, wherein one terminal of the fourth bypass capacitor is electrically coupled to the fourth node.