Receive end and transmit end of wireless charging system, method, electrical terminal, and system
Example wireless charging systems and methods are disclosed. One example system includes a receive end and a transmit end. The receive end includes a receive coil, a receive end compensation circuit, a rectifier, and a controller. The controller adjusts a phase difference between a first bridge arm and a second bridge arm of the rectifier, and adjusts a phase-shift angle between a bridge arm voltage of the rectifier and a fundamental component of an input current of the rectifier, so that zero-voltage switching is implemented for controllable switching transistors of the rectifier. An inductance compensation module may weaken a capacitive part of the equivalent impedance, and reduce reactive power of the wireless charging system.
1. A receive end of a wireless charging system, the receive end comprising a receive coil, a receive end compensation circuit, a rectifier, and a controller, wherein:
the receive coil is configured to receive an alternating magnetic field and output an alternating current;
the receive end compensation circuit is connected between the receive coil and the rectifier, wherein the receive end compensation circuit is configured to:
compensate the alternating current that is output by the receive coil; and
output a compensated alternating current to the rectifier;
the receive end compensation circuit and the receive coil form a receive end compensation network, wherein the receive end compensation network comprises a first branch, a second branch, and a third branch, wherein the first branch comprises the receive coil, wherein both the first branch and the second branch are inductive branches, wherein a reactance of the second branch is greater than that of the first branch, wherein the first branch is connected to a first input end of the rectifier through the second branch, wherein the third branch is a capacitive branch, wherein a first end of the third branch is connected to a common end of the first branch and the second branch, and wherein a second end of the third branch is connected to a second input end of the rectifier;
the rectifier comprises controllable switching transistors, wherein the rectifier is configured to rectify the alternating current to a direct current; and
the controller is configured to:
adjust a phase difference between a first bridge arm and a second bridge arm of the rectifier; and
adjust a phase-shift angle between a bridge arm voltage of the rectifier and a fundamental component of an input current of the rectifier, wherein zero-voltage switching is implemented for the controllable switching transistors of the rectifier.
2. The receive end of the wireless charging system according to claim 1 , wherein the controller is configured to:
control the phase difference between the first bridge arm and the second bridge arm of the rectifier to be a target phase difference α, and
control the phase-shift angle between the bridge arm voltage of the rectifier and the fundamental component of the input current of the rectifier to be π−α+σ, wherein σ is a target value, wherein α is used to adjust a resistance of an equivalent impedance of the rectifier, and wherein σ is used to adjust a reactance of the equivalent impedance of the rectifier.
3. The receive end of the wireless charging system according to claim 2 , wherein σ is obtained from an external instruction, and wherein σ is preset inside the controller.
4. The receive end of the wireless charging system according to claim 2 , wherein σ is obtained from an external instruction, and wherein α is preset inside the controller.
5. The receive end of the wireless charging system according to claim 1 , wherein the second branch comprises an inductance compensation module and an inductive sub-branch, wherein the first branch, the third branch, and the inductive sub-branch form an inductor-capacitor-inductor (LCL) compensation network, and wherein modulus values of the first branch, the third branch, and the inductive sub-branch are equal; and
wherein the inductance compensation module is configured to weaken a capacitive part of an equivalent impedance of the rectifier.
6. The receive end of the wireless charging system according to claim 5 , wherein the first branch, the inductive sub-branch, and the third branch satisfy the following formula:
jX L1 =−jX C =jX L2 , wherein:
jX L1 is a reactance of the first branch, −jX C is a reactance of the third branch, and jX L2 is a reactance of the inductive sub-branch.
7. The receive end of the wireless charging system according to claim 5 , wherein an inductance L 2_comp of the inductance compensation module is 0.3-3 times as great as a theoretical inductance L, and wherein the theoretical inductance L is obtained according to the following formula:
L
=
8
π
2
*
(
sin
α
2
)
2
*
R
d
c
*
cos
(
π
-
α
2
+
σ
)
*
sin
(
π
-
α
2
+
σ
)
ω
s
,
wherein:
ω s is an angular frequency of the fundamental component of the alternating current of the rectifier, and
R dc is a load equivalent resistance when the wireless charging system performs output at full power.
8. The receive end of the wireless charging system according to claim 7 , wherein when L is calculated,
α
=
2
π
3
and
σ
=
0
.
9. The receive end of the wireless charging system according to claim 8 , wherein L 2_comp =L.
10. The receive end of the wireless charging system according to claim 1 , wherein the second branch comprises one inductor.
11. The receive end of the wireless charging system according to claim 1 , wherein the second branch comprises two inductors: a first inductor and a second inductor; and
wherein the first branch is connected to a middle point of the first bridge arm of the rectifier through the first inductor, and wherein the second end of the third branch is connected to a middle point of the second bridge arm of the rectifier through the second inductor.
12. The receive end of the wireless charging system according to claim 11 , wherein a reactance of the first inductor is equal to a reactance of the second inductor.
13. The receive end of the wireless charging system according to claim 1 , wherein the second branch is used to weaken a capacitive part of the equivalent impedance of the rectifier.
14. The receive end of the wireless charging system according to claim 3 , wherein the controller is further configured to:
receive a compensation phase sent by a transmit end; and
adjust σ from the target value to the compensation phase after receiving the compensation phase, wherein the compensation phase is obtained by the transmit end based on a result of comparison between a reactive current that is output by an inverter of the transmit end and a preset reactive current.
15. A receive end control method used in a receive end of a wireless charging system, wherein the receive end comprises a receive coil, a receive end compensation circuit, a rectifier, and a controller, wherein:
the receive coil is configured to receive an alternating magnetic field and output an alternating current;
the receive end compensation circuit is connected between the receive coil and the rectifier, wherein the receive end compensation circuit is configured to:
compensate the alternating current that is output by the receive coil; and
output a compensated alternating current to the rectifier;
the receive end compensation circuit and the receive coil form a receive end compensation network, wherein the receive end compensation network comprises a first branch, a second branch, and a third branch, wherein the first branch comprises the receive coil, wherein both the first branch and the second branch are inductive branches, wherein a reactance of the second branch is greater than that of the first branch, wherein the first branch is connected to a first input end of the rectifier through the second branch, wherein the third branch is a capacitive branch, wherein a first end of the third branch is connected to a common end of the first branch and the second branch, and wherein a second end of the third branch is connected to a second input end of the rectifier;
the rectifier comprises controllable switching transistors, wherein the rectifier is configured to rectify the alternating current to a direct current; and
the control method comprises:
adjusting a phase difference between a first bridge arm and a second bridge arm of the rectifier; and
adjusting a phase-shift angle between a bridge arm voltage and a fundamental component of an input current of the rectifier, wherein zero-voltage switching is implemented for the controllable switching transistors of the rectifier.
16. The control method according to claim 15 , wherein the adjusting a phase difference between a first bridge arm and a second bridge arm of the rectifier, and adjusting a phase-shift angle between a bridge arm voltage and a fundamental component of an input current of the rectifier comprises:
controlling the phase difference between the first bridge arm and the second bridge arm of the rectifier to be a target phase difference α; and
controlling the phase-shift angle between the bridge arm voltage of the rectifier and the fundamental component of the input current of the rectifier to be π−α+σ, wherein σ is a preset value, wherein α is used to adjust a resistance of an equivalent impedance of the rectifier, and wherein σ is used to adjust a reactance of the equivalent impedance of the rectifier.
17. The control method according to claim 16 , wherein α is obtained from an external instruction, and wherein σ is preset inside the controller.
18. The control method according to claim 16 , wherein σ is obtained from an external instruction, and wherein α is preset inside the controller.
19. The control method according to claim 17 , further comprising:
receiving a compensation phase sent by a transmit end; and
making σ equal to the compensation phase, wherein the compensation phase is obtained by the transmit end based on a result of comparison between a reactive current that is output by an inverter of the transmit end and a preset reactive current.
20. A wireless charging system, comprising a transmit end and a receive end, wherein:
the transmit end comprises an inverter, a transmit end compensation circuit, and a transmit coil, wherein:
the inverter is configured to convert, to an alternating current, a direct current that is output by a direct current power supply;
the transmit end compensation circuit is configured to: compensate the alternating current, and output a compensated alternating current to the transmit coil;
the transmit coil is configured to transmit the alternating current in a form of an alternating magnetic field; and
the transmit coil and the transmit coil form a transmit end LCL compensation network; and
the receive end comprises a receive coil, a receive end compensation circuit, a rectifier, and a controller, wherein:
the receive coil is configured to receive an alternating magnetic field and output an alternating current;
the receive end compensation circuit is connected between the receive coil and the rectifier, wherein the receive end compensation circuit is configured to:
compensate the alternating current that is output by the receive coil; and
output a compensated alternating current to the rectifier;
the receive end compensation circuit and the receive coil form a receive end compensation network, wherein the receive end compensation network comprises a first branch, a second branch, and a third branch, wherein the first branch comprises the receive coil, wherein both the first branch and the second branch are inductive branches, wherein a reactance of the second branch is greater than that of the first branch, wherein the first branch is connected to a first input end of the rectifier through the second branch, wherein the third branch is a capacitive branch, wherein a first end of the third branch is connected to a common end of the first branch and the second branch, and wherein a second end of the third branch is connected to a second input end of the rectifier;
the rectifier comprises controllable switching transistors, wherein the rectifier is configured to rectify the alternating current to a direct current; and
the controller is configured to:
adjust a phase difference between a first bridge arm and a second bridge arm of the rectifier; and
adjust a phase-shift angle between a bridge arm voltage of the rectifier and a fundamental component of an input current of the rectifier, wherein zero-voltage switching is implemented for the controllable switching transistors of the rectifier.