U.S. patent application number 16/739702 was filed with the patent office on 2020-05-14 for wireless power transmitter circuit and control circuit and control method thereof.
The applicant listed for this patent is RICHTEK TECHNOLOGY CORPORATION. Invention is credited to Kuo-Chi Liu.
Application Number | 20200153285 16/739702 |
Document ID | / |
Family ID | 62906642 |
Filed Date | 2020-05-14 |
![](/patent/app/20200153285/US20200153285A1-20200514-D00000.png)
![](/patent/app/20200153285/US20200153285A1-20200514-D00001.png)
![](/patent/app/20200153285/US20200153285A1-20200514-D00002.png)
![](/patent/app/20200153285/US20200153285A1-20200514-D00003.png)
![](/patent/app/20200153285/US20200153285A1-20200514-D00004.png)
United States Patent
Application |
20200153285 |
Kind Code |
A1 |
Liu; Kuo-Chi |
May 14, 2020 |
WIRELESS POWER TRANSMITTER CIRCUIT AND CONTROL CIRCUIT AND CONTROL
METHOD THEREOF
Abstract
The present invention provides a wireless power transmitter
circuit which includes a power converter circuit, a power inverter
circuit, a resonant transmitter circuit and a power control
circuit. The power conversion circuit converts an input power to a
conversion output power which includes a conversion output voltage.
The power inverter circuit converts the conversion output power to
an AC output power. The resonant transmitter circuit converts the
AC output power to a resonant wireless power. The power control
circuit generates a current reference signal according to the
conversion output voltage, and generates a conversion control
signal according to a difference between the current reference
signal and a resonant current related signal, to control the power
converter circuit such that the resonant wireless power is
regulated substantially at a predetermined power level.
Inventors: |
Liu; Kuo-Chi; (Hsiinchu,
TW) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
RICHTEK TECHNOLOGY CORPORATION |
Zhubei City |
|
CN |
|
|
Family ID: |
62906642 |
Appl. No.: |
16/739702 |
Filed: |
January 10, 2020 |
Related U.S. Patent Documents
|
|
|
|
|
|
Application
Number |
Filing Date |
Patent Number |
|
|
15611210 |
Jun 1, 2017 |
10574092 |
|
|
16739702 |
|
|
|
|
Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H02M 7/48 20130101; H02M
7/44 20130101; H02J 50/12 20160201 |
International
Class: |
H02J 50/12 20060101
H02J050/12 |
Foreign Application Data
Date |
Code |
Application Number |
Jan 20, 2017 |
CN |
201710049465.X |
Claims
1-9. (canceled)
10. A wireless power transmitter circuit, comprising: a power
conversion circuit, configured to operably convert an input power
to a conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; a resonant transmitter circuit which includes at least a
transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; and a power control
circuit, configured to operably generate a voltage reference signal
according to a resonant current related signal, and generate a
conversion control signal according to a difference between the
voltage reference signal and the conversion output voltage, so as
to control the power conversion circuit by the conversion control
signal to regulate the resonant wireless power substantially at a
predetermined first power level.
11. The wireless power transmitter circuit of claim 10, wherein the
power control circuit includes: a voltage reference signal
generator circuit, configured to operably generate the voltage
reference signal according to a reference current signal and a
signal related to the resonant current (resonant current related
signal); and a conversion control signal generator circuit,
configured to operably generate the conversion control signal
according to a difference between the voltage reference signal and
the conversion output voltage.
12. The wireless power transmitter circuit of claim 10, wherein the
resonant current decreases when the conversion output voltage
increases, and the resonant current increases when the conversion
output voltage decreases.
13. The wireless power transmitter circuit of claim 10, wherein the
conversion control signal controls the power conversion circuit to
regulate the AC output power or the conversion output power
substantially at a predetermined second power level which is
related to the first power level.
14. The wireless power transmitter circuit of claim 10, wherein the
power conversion circuit is a switching buck converter circuit, a
switching boost converter circuit, a switching buck-boost converter
circuit, or an AC-DC converter circuit.
15. The wireless power transmitter circuit of claim 10, wherein the
power inverter circuit is a class D inverter circuit, or a class E
inverter circuit.
16. The wireless power transmitter circuit of claim 10, wherein the
conversion control signal controls the power conversion circuit to
regulate the resonant current or the AC output current
substantially at a predetermined current level when the conversion
output voltage is lower than a predetermined voltage threshold.
17-22. (canceled)
23. A power control circuit, configured to operably control a
wireless power transmitter circuit which comprises: a power
conversion circuit, configured to operably convert an input power
to a conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; and a resonant transmitter circuit which includes at least
a transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; the power control
circuit including: a voltage reference signal generator circuit,
configured to operably generate a voltage reference signal
according to a reference current signal and the resonant current
related signal; and a conversion control signal generator circuit,
configured to operably generate a conversion control signal
according to a difference between the voltage reference signal and
the conversion output voltage, so as to control the power
conversion circuit by the conversion control signal to regulate the
resonant wireless power substantially at a predetermined first
power level.
24. The power control circuit of claim 23, wherein the resonant
current decreases when the conversion output voltage increases, and
the resonant current increases when the conversion output voltage
decreases.
25. The power control circuit of claim 23, wherein the conversion
control signal controls the power conversion circuit to regulate
the AC output power or the conversion output power substantially at
a predetermined second power level which is related to the first
power level.
26. The power control circuit of claim 23, wherein the conversion
control signal controls the power conversion circuit to regulate
the resonant current or the AC output current substantially at a
predetermined current level when the conversion output voltage is
lower than a predetermined voltage threshold.
27-32. (canceled)
33. A control method, for use in controlling a wireless power
transmitter circuit which comprises: a power conversion circuit,
configured to operably convert an input power to a conversion
output power, wherein the conversion output power includes a
conversion output voltage; a power inverter circuit, configured to
operably convert the conversion output power to an AC output power,
wherein the AC output power includes an AC output current; and a
resonant transmitter circuit which includes at least a transmitter
coil, and is configured to operably convert the AC output power to
a resonant wireless power, wherein the resonant transmitter circuit
has a resonant current; the control method comprising: generating a
voltage reference signal according to a signal related to the
resonant current; generating a conversion control signal according
to a difference between the voltage reference signal and the
conversion output voltage; and controlling the power conversion
circuit by the conversion control signal to regulate the resonant
wireless power substantially at a predetermined first power
level.
34. The control method of claim 33, wherein the resonant current
decreases when the conversion output voltage increases, and the
resonant current increases when the conversion output voltage
decreases.
35. The control method of claim 33, further comprising: controlling
the power conversion circuit to regulate the AC output power or the
conversion output power substantially at a predetermined second
power level which is related to the first power level.
36. The control method of claim 33, further comprising: controlling
the power conversion circuit by the conversion control signal to
regulate the resonant current or the AC output current
substantially at a predetermined current level when the conversion
output voltage is lower than a predetermined voltage threshold.
Description
CROSS REFERENCE
[0001] The present invention claims priority to CN 201710049465.X,
filed on Jan. 20, 2017.
BACKGROUND OF THE INVENTION
Field of Invention
[0002] The present invention relates to a wireless power
transmitter circuit, and particularly to a constant power wireless
power transmitter circuit. The present invention also relates to a
control circuit and a control method for use in the wireless power
transmitter circuit.
Description of Related Art
[0003] In general, it is required for a wireless power transmitter
circuit to be able to operate under constant current control in
normal operation, and to be switched to operate under constant
power control when the input power or output power is overly high
to avoid damage to the wireless power transmitter circuit itself or
other circuits receiving power from it. FIG. 1 shows a prior art
wireless power transmitter circuit (wireless power transmitter
circuit 1) which comprises a DC-DC conversion circuit, a power
inverter circuit, a resonant transmitter circuit 11 and a MCU
(micro-controller unit) based controller. The DC-DC conversion
circuit converts a DC power to a conversion output voltage VDCO.
The power inverter circuit converts the conversion output voltage
to an AC output power. The resonant transmitter circuit 11 converts
the AC output power to a resonant wireless power to be transmitted
in a wireless manner. The MCU based controller generates a
conversion control signal CTRL according to the conversion output
voltage VDCO and a resonant current IRS, to control the DC-DC
conversion circuit such that the wireless power transmitter circuit
1 operates in a constant current mode or a constant power mode.
[0004] The prior art circuit in FIG. 1 has a drawback as thus. The
MCU based controller needs an ADC (analog-to-digital converter) to
convert the measured voltage and current to digital signals for
calculating the power or current, and the calculated result is
converted to a conversion control signal by a DAC
(digital-to-analog converter). As the demands of the accuracy, the
sampling rate and computation speed are getting higher and higher,
the requirements for the ADC, DAC and MCU are also getting higher,
which leads to higher cost and more complexity in circuit
design.
[0005] Compared to the prior art in FIG. 1, the present invention
is advantageous in that the present invention can operate in a
constant current mode or a constant power mode by analog control,
with advantages of simpler circuit architecture, faster response
and lower cost.
SUMMARY OF THE INVENTION
[0006] From one perspective, the present invention provides a
wireless power transmitter circuit, comprising: a power conversion
circuit, configured to operably convert an input power to a
conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; a resonant transmitter circuit which includes at least a
transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; and a power control
circuit, configured to operably generate a current reference signal
according to the conversion output voltage, and generate a
conversion control signal according to a difference between the
current reference signal and a signal related to the resonant
current (resonant current related signal), so as to control the
power conversion circuit by the conversion control signal to
regulate the resonant wireless power substantially at a
predetermined first power level.
[0007] In one embodiment, the power control circuit includes: a
current reference signal generator circuit, configured to operably
generate the current reference signal according to a reference
voltage and the conversion output voltage; and a conversion control
signal generator circuit, configured to operably generate the
conversion control signal according to a difference between the
current reference signal and the resonant current related
signal.
[0008] From one perspective, the present invention provides a
wireless power transmitter circuit, comprising: a power conversion
circuit, configured to operably convert an input power to a
conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; a resonant transmitter circuit which includes at least a
transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; and a power control
circuit, configured to operably generate a voltage reference signal
according to a resonant current related signal, and generate a
conversion control signal according to a difference between the
voltage reference signal and the conversion output voltage, so as
to control the power conversion circuit by the conversion control
signal to regulate the resonant wireless power substantially at a
predetermined first power level.
[0009] In one embodiment, the power control circuit includes: a
voltage reference signal generator circuit, configured to operably
generate the voltage reference signal according to a reference
current signal and the resonant current related signal; and a
conversion control signal generator circuit, configured to operably
generate the conversion control signal according to a difference
between the voltage reference signal and the conversion output
voltage.
[0010] In one embodiment, the resonant current decreases when the
conversion output voltage increases, and the resonant current
increases when the conversion output voltage decreases.
[0011] In one embodiment, the conversion control signal controls
the power conversion circuit to regulate the AC output power or the
conversion output power substantially at a predetermined second
power level which is related to the first power level.
[0012] In one embodiment, the power conversion circuit is a
switching buck converter circuit, a switching boost converter
circuit, a switching buck-boost converter circuit, or an AC-DC
converter circuit.
[0013] In one embodiment, the power inverter circuit is a class D
inverter circuit, or a class E inverter circuit.
[0014] In one embodiment, the conversion control signal controls
the power conversion circuit to regulate the resonant current or
the AC output current substantially at a predetermined current
level when the conversion output voltage is lower than a
predetermined voltage threshold.
[0015] In one embodiment, the power control circuit includes: a
transconductance amplifier circuit, configured to operably generate
a transconductance amplification output signal according to a
reference voltage and the conversion output voltage; a
unidirectional conductive device, having a current output terminal
which is coupled to the transconductance amplification output
signal, and having a current input terminal at which the current
reference signal is generated; and a signal amplifier circuit,
configured to operably generate the conversion control signal
according to a difference between the current reference signal and
the resonant current related signal.
[0016] In one embodiment, the predetermined voltage threshold is
the reference voltage.
[0017] In one embodiment, the conversion control signal controls
the power conversion circuit to regulate the resonant current or
the AC output current substantially at a predetermined current
level when the conversion output voltage is lower than a
predetermined voltage threshold.
[0018] From another perspective, the present invention provides a
power control circuit, configured to operably control a wireless
power transmitter circuit which comprises: a power conversion
circuit, configured to operably convert an input power to a
conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; and a resonant transmitter circuit which includes at least
a transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; the power control
circuit comprising: a current reference signal generator circuit,
configured to operably generate a current reference signal
according to a reference voltage and the conversion output voltage;
and a conversion control signal generator circuit, configured to
operably generate a conversion control signal according to a
difference between the current reference signal and a signal
related to the resonant current (resonant current related signal),
so as to control the power conversion circuit by the conversion
control signal to regulate the resonant wireless power
substantially at a predetermined first power level.
[0019] From another perspective, the present invention provides a
power control circuit, configured to operably control a wireless
power transmitter circuit which comprises: a power conversion
circuit, configured to operably convert an input power to a
conversion output power, wherein the conversion output power
includes a conversion output voltage; a power inverter circuit,
configured to operably convert the conversion output power to an AC
output power, wherein the AC output power includes an AC output
current; and a resonant transmitter circuit which includes at least
a transmitter coil, and is configured to operably convert the AC
output power to a resonant wireless power, wherein the resonant
transmitter circuit has a resonant current; the power control
circuit including: a voltage reference signal generator circuit,
configured to operably generate a voltage reference signal
according to a reference current signal and the resonant current
related signal; and a conversion control signal generator circuit,
configured to operably generate the conversion control signal
according to a difference between the voltage reference signal and
the conversion output voltage, so as to control the power
conversion circuit by the conversion control signal to regulate the
resonant wireless power substantially at a predetermined first
power level.
[0020] In one embodiment, the resonant current decreases when the
conversion output voltage increases, and the resonant current
increases when the conversion output voltage decreases.
[0021] In one embodiment, the current reference signal generator
circuit includes: a transconductance amplifier circuit, configured
to operably generate a transconductance amplification output signal
according to a reference voltage and the conversion output voltage;
a unidirectional conductive device, having a current output
terminal which is coupled to the transconductance amplification
output signal, and having a current input terminal at which the
current reference signal is generated; and a signal amplifier
circuit, configured to operably generate the conversion control
signal according to a difference between the current reference
signal and the resonant current related signal.
[0022] From another perspective, the present invention provides a
control method, for use in controlling a wireless power transmitter
circuit which comprises: a power conversion circuit, configured to
operably convert an input power to a conversion output power,
wherein the conversion output power includes a conversion output
voltage; a power inverter circuit, configured to operably convert
the conversion output power to an AC output power, wherein the AC
output power includes an AC output current; and a resonant
transmitter circuit which includes at least a transmitter coil, and
is configured to operably convert the AC output power to a resonant
wireless power, wherein the resonant transmitter circuit has a
resonant current; the control method comprising: generating a
current reference signal according to the conversion output
voltage; generating a conversion control signal according to a
difference between the current reference signal and a resonant
current related signal; and controlling the power conversion
circuit by the conversion control signal to regulate the resonant
wireless power substantially at a predetermined first power
level.
[0023] From another perspective, the present invention provides a
control method, for use in controlling a wireless power transmitter
circuit which comprises: a power conversion circuit, configured to
operably convert an input power to a conversion output power,
wherein the conversion output power includes a conversion output
voltage; a power inverter circuit, configured to operably convert
the conversion output power to an AC output power, wherein the AC
output power includes an AC output current; and a resonant
transmitter circuit which includes at least a transmitter coil, and
is configured to operably convert the AC output power to a resonant
wireless power, wherein the resonant transmitter circuit has a
resonant current; the control method comprising: generating a
voltage reference signal according to a signal related to the
resonant current; generating a conversion control signal according
to a difference between the voltage reference signal and the
conversion output voltage; and controlling the power conversion
circuit by the conversion control signal to regulate the resonant
wireless power substantially at a predetermined first power
level.
[0024] In one embodiment, the resonant current decreases when the
conversion output voltage increases, and the resonant current
increases when the conversion output voltage decreases.
[0025] In one embodiment, the step of generating the current
reference signal includes: generating an amplification output
signal according to a difference between a reference voltage and
the conversion output voltage; and generating the current reference
signal by unidirectionally conducting the amplification output
signal.
[0026] The objectives, technical details, features, and effects of
the present invention will be better understood with regard to the
detailed description of the embodiments below.
BRIEF DESCRIPTION OF THE DRAWINGS
[0027] FIG. 1 shows a schematic diagram of a prior art wireless
power transmitter circuit.
[0028] FIG. 2 shows a schematic diagram of an embodiment of the
wireless power transmitter circuit according to the present
invention.
[0029] FIG. 3 shows a schematic diagram of an embodiment of the
power control circuit of the wireless power transmitter circuit
according to the present invention.
[0030] FIG. 4 shows simulation characteristic curves corresponding
to the embodiments shown in FIGS. 2 and 3.
[0031] FIGS. 5A and 5B show simulation waveforms corresponding to
the embodiments shown in FIGS. 2 and 3.
[0032] FIG. 6 shows a schematic diagram of an embodiment of the
wireless power transmitter circuit according to the present
invention.
DESCRIPTION OF THE PREFERRED EMBODIMENTS
[0033] The drawings as referred to throughout the description of
the present invention are for illustration only, to show the
interrelations between the circuits and the signal waveforms, but
not drawn according to actual scale.
[0034] FIG. 2 shows one embodiment of the wireless power
transmitter circuit according to the present invention (wireless
power transmitter circuit 2), wherein the wireless power
transmitter circuit 2 comprises a power conversion circuit 20, a
power inverter circuit 30, a resonant transmitter circuit 40, and a
power control circuit 50. The power conversion circuit 20 converts
an input power PIN to a conversion output power, wherein the
conversion output power includes a conversion output voltage VDCO.
The input power PIN may be an AC power or a DC power, and the power
conversion circuit 20 may correspondingly be an AC-DC converter
circuit or a DC-DC converter circuit. The power inverter circuit 30
converts the conversion output power to an AC output power PACO,
wherein the AC output power PACO includes an AC output current IAC.
The resonant transmitter circuit 40 has a resonant current IRS. In
this embodiment, the resonant transmitter circuit 40 includes a
transmitter coil L and a resonant capacitor C which are connected
in series. Note that the resonant transmitter circuit structure is
not limited to the one shown in this embodiment, and may be
realized by resonant circuits in other forms, for example but not
limited to a parallel type resonant circuit, or combinations of
parallel and series type resonant circuits. The power control
circuit 50 generates a current reference signal IREF according to
the conversion output voltage VDCO, and generates a conversion
control signal CTRL according to a difference between the current
reference signal IREF and a signal related to the resonant current
IRS (resonant current related signal ITX), so as to control the
power conversion circuit 20 by the conversion control signal CTRL
to regulate the resonant wireless power POUT substantially at a
predetermined first power level such that the wireless power
transmitter circuit 2 operates in the constant power mode. The
resonant current related signal ITX can be obtained by a current
sensing circuit which senses the resonant current IRS.
[0035] The term "predetermined" as used in the context of this
invention, such as the "predetermined first power level" may be a
fixed value or an adjustable variable. Also note that, although it
is preferred to regulate the resonant wireless power POUT exactly
at the predetermined first power level, however due to
non-idealities caused by for example imperfection of components or
imperfect matching among components, the level of the actual
resonant wireless power POUT may not be exactly equal to the first
power level, but just close to the first power level, so the term
"substantially" means that there is an allowable tolerance
range.
[0036] Still referring FIG. 2, in one embodiment, the power control
circuit includes a current reference signal generator circuit 51,
and a conversion control signal generator circuit 52. The current
reference signal generator circuit 51 generates the current
reference signal IREF according to a reference voltage VREF and the
conversion output voltage VDCO. The conversion control signal
generator circuit 52 generates the conversion control signal CTRL
according to a difference between the current reference signal IREF
and the resonant current related signal ITX.
[0037] Still referring FIG. 2, in one embodiment, under control by
the power control circuit 50, the resonant current IRS decreases
when the conversion output voltage VDCO increases, and the resonant
current IRS increases when the conversion output voltage VDCO
decreases, whereby the constant power mode is achieved.
[0038] Still referring FIG. 2, in one embodiment, the conversion
control signal CTRL controls the power conversion circuit 20 to
regulate the AC output power PACO of the power inverter circuit 30
substantially at a predetermined second power level which is
related to the first power level. In one preferred embodiment, the
power loss of each circuit is ignorable or substantially a constant
value, so the level of the resonant wireless power POUT can also
maintains substantially at the first power level when the AC output
power is regulated substantially at the predetermined second power
level, whereby the wireless power transmitter circuit 2 operates in
the constant power mode. In another embodiment, the conversion
control signal CTRL controls the power conversion circuit 20 to
regulate the conversion output power substantially at a
predetermined third power level which is related to the first power
level. In one preferred embodiment, the power loss of each circuit
is ignorable or substantially a constant value, so the level of the
resonant wireless power POUT can also maintains substantially at
the first power level when the conversion output power is regulated
substantially at the predetermined third power level, whereby the
wireless power transmitter circuit 2 operates in the constant power
mode.
[0039] In some embodiments of the wireless power transmitter
circuit of the present invention, according to different
requirements such as the voltage ranges of the input power PIN and
the conversion output voltage VDCO, the power conversion circuit 20
may be a switching buck converter circuit, a switching boost
converter circuit, or a switching buck-boost converter circuit, for
converting the input power PIN with step-down conversion, step-up
conversion, or buck-boost conversion to generate the conversion
output voltage VDCO. In one embodiment, the power conversion
circuit 20 may be an AC-DC converter circuit for converting the
input power PIN in an AC form.
[0040] In some embodiments of the wireless power transmitter
circuit of the present invention, according to different
requirements, the power inverter circuit 30 may be a class D
inverter circuit, or a class E inverter circuit.
[0041] FIG. 3 shows one embodiment of the power control circuit
(power control circuit 50') of the wireless power transmitter
circuit according to the present invention, wherein the power
control circuit 50' includes a voltage reference signal generator
circuit 51, and a conversion control signal generator circuit 52.
The voltage reference signal generator circuit 51 includes a
transconductance amplifier circuit 511 and a unidirectional
conduction device Dl, which is a diode Dl in this embodiment. The
transconductance amplifier circuit 511 generates a transconductance
amplification output signal VGO according to a reference voltage
VREF and the conversion output voltage VDCO. A current output
terminal of the diode Dl is coupled to the transconductance
amplification output signal VGO. The diode Dl generates the current
reference signal IREF on a current input terminal of the diode Dl
by shunting the current input terminal of the diode Dl to a
current-voltage conversion circuit 512. The conversion control
signal generator circuit 52 includes a signal amplifier circuit
521. In this embodiment, by means of the unidirectional conduction
characteristic of the diode Dl, when the conversion output voltage
VDCO is lower than the reference voltage VREF, the current
reference signal IREF is a predetermined reference voltage, while
when the conversion output voltage VDCO is higher than the
reference voltage VREF, and the current reference signal IREF
varies according to the difference between the conversion output
voltage VDCO and the voltage reference VREF, wherein the current
reference signal IREF decreases when the difference between the
conversion output voltage VDCO and the voltage reference VREF
increases, and the current reference signal IREF increases when the
difference between the conversion output voltage VDCO and the
voltage reference VREF decreases. The signal amplifier circuit 521
generates the conversion control signal CTRL according to the
difference between the current reference signal IREF and the
resonant current related signal ITX, such that the resonant current
IRS is regulated substantially at a predetermined current level
when the conversion output voltage VDCO is lower than the reference
voltage VREF (in this case the current reference IREF is the
predetermined reference voltage), whereby the wireless power
transmitter circuit 2 operates in the constant current mode. On the
other hand, when the conversion output voltage VDCO is higher than
the reference voltage VREF, the resonant current IRS decreases when
the conversion output voltage VDCO increases and the resonant
current IRS increases when the conversion output voltage VDCO
decreases, therefore the resonant wireless power POUT is regulated
substantially at the aforementioned predetermined first power level
such that the wireless power transmitter circuit 2 operates in the
constant output power mode. Note that the reference voltage VREF
may be a fixed value, or an adjustable variable.
[0042] Note that the targets to be regulated are resonant current
IRS and the resonant wireless power POUT in the aforementioned
embodiment; however, it is not limited to regulating these targets
according to the spirit of the present invention. In one
embodiment, such as the embodiment shown in FIG. 3, the wireless
power transmitter circuit can alternatively regulate the AC output
current IAC substantially at a predetermined current level when the
conversion output voltage VDCO is lower than the reference voltage
VREF, such that the wireless power transmitter circuit operates in
the constant current mode, and regulate the AC output power PACO
substantially at the aforementioned predetermined second power
level when the conversion output voltage VDCO is higher than the
reference voltage VREF, such that the wireless power transmitter
circuit 2 operates in the constant power mode. Besides, the
reference voltage VREF is used as the threshold to switch (to
determine the boundary) between the constant power mode and the
constant current mode. However, the present invention is not
limited to this arrangement. In one embodiment, the power control
circuit 50' may determine whether the wireless power transmitter
circuit should operate in the constant power mode or the constant
current mode according to a predetermined voltage threshold
VTH.
[0043] Note that the wireless power transmitter circuit of the
present invention uses an analog control scheme, so compared to the
prior art circuits, the present invention is advantageous in
achieving the aforementioned operations in a continuous
(non-step-wise) and analog manner, with a faster response, and a
lower cost due to simpler circuitry.
[0044] Please refer to FIG. 4 which shows simulation characteristic
curves corresponding to the embodiments as shown in FIGS. 2 and 3.
In the embodiment shown in FIG. 4, when the reflected resistance
(i.e. the real part of the reflected impedance of the resonant
transmitter circuit, as represented by Req as shown in FIG. 2) of
the resonant transmitter circuit (e.g. the resonant transmitter
circuit 40 in FIG. 2) is lower than 25 ohm, the wireless power
transmitter operates in the constant current mode, wherein the
resonant current IRS (the short dashed line as shown in the figure)
is regulated substantially at a predetermined current level (e.g.
800 mA as shown in the figure). And when the reflected resistance
is higher than 25 ohm, the wireless power transmitter operates in
the constant power mode, wherein the resonant wireless power POUT
(the solid line as shown in the figure) is regulated substantially
at the aforementioned predetermined first power level (e.g. 16 W as
shown in the figure).
[0045] Note that in this embodiment, the reflected resistance is
the independent variable and the current and the power of the
wireless are measured and observed dependently, and the boundary
between the constant current mode operation and the constant power
mode operation is determined by a threshold of the reflected
resistance. Nevertheless, since the conversion output voltage VDCO
(the long dashed line shown in the figure) is substantially
proportional to the reflected resistance because of the control
scheme of the wireless power transmitter circuit of the present
invention, to determine the boundary between the constant current
mode operation and the constant power mode operation by a threshold
of the reflected resistance is equivalent to determining the
boundary by a predetermined voltage threshold (for example 25V,
which corresponds to the aforementioned reference voltage VREF, as
shown in FIG. 4). In this case, the embodiment shown in FIG. 4 can
be re-described accordingly as when the conversion output voltage
VDCO is lower than 25 V, the wireless power transmitter operates in
the constant current mode, wherein the resonant current IRS is
regulated substantially at a predetermined current level (e.g. 800
mA as shown in the figure), and when the conversion output voltage
VDCO is higher than 25V, the wireless power transmitter operates in
the constant power mode, wherein the resonant wireless power POUT
is regulated substantially at the aforementioned predetermined
first power level (e.g. 16 W as shown in the figure).
[0046] FIGS. 5A and 5B show simulation waveforms corresponding to
the embodiments of FIG. 2 or 3, wherein FIGS. 5A and 5B show
simulation waveforms, in time domain, of the reflected resistance
of the resonant transmitter circuit being 25 ohm and 55 ohm
respectively, wherein the voltages of the input power PIN are both
12V and the operating frequencies are both 6.78 MHz. In the
embodiments as shown in FIGS. 5A and 5B, the conversion output
voltage VDCO and the resonant current IRS are substantially inverse
proportional to each other as mentioned earlier, that is, the
resonant current IRS increases when the conversion output voltage
VDCO decreases (as shown in FIG. 5A), and the resonant current IRS
decreases when the conversion output voltage VDCO decreases (as
shown in FIG. 5B). The substantially inverse proportion
relationship between the conversion output voltage VDCO and the
resonant current IRS keeps the resonant wireless power POUT
substantially at a fixed power regardless whether the reflected
resistance of the resonant transmitter circuit is either 25 ohm or
55 ohm, thus the constant power mode is achieved (e.g. average
about 16 W both in FIGS. 5A and 5B).
[0047] Referring to FIG. 6 which shows a schematic diagram of
another embodiment of the wireless power transmitter circuit
(wireless power transmitter circuit 4) according to the present
invention, this embodiment is similar to the wireless power
transmitter circuit 2 in FIG. 2, but is different in that the power
control circuit 50'' generates a voltage reference signal VREF'
according to the resonant current related signal ITX, and generates
a conversion control signal CTRL according to a difference between
the conversion output voltage VDCO and the voltage reference signal
VREF'. The power conversion circuit 20 is controlled by the
conversion control signal CTRL and this embodiment is able to
achieve all the functions of the aforementioned embodiments,
including the constant power mode (i.e. regulating the AC output
power PACO or the conversion output power substantially at a
predetermined second power level), or the constant current mode
(i.e. regulating the resonant current IRS or the AC output current
IAC substantially at a predetermined current level).
[0048] More specifically, in this embodiment, the power control
circuit includes a voltage reference signal generator circuit 53
and a conversion control signal generator circuit 54. The voltage
reference signal generator circuit 53 generates a voltage reference
signal VREF' according to a reference current signal IREF' and the
resonant current related signal ITX. The conversion control signal
generator circuit 54 generates the conversion control signal CTRL
according to a difference between the voltage reference signal
VREF' and the conversion output voltage VDCO to control the power
conversion circuit 20 to achieve the aforementioned functions (e.g.
regulating the resonant wireless power POUT substantially at a
predetermined power level, etc.). In one embodiment, the conversion
control signal generator circuit 54 determines whether the wireless
power transmitter circuit should operate in the constant power mode
or the constant current mode operation according to a predetermined
voltage threshold VTH. For example, when the conversion output
voltage VDCO is lower than the predetermined voltage threshold VTH,
the resonant current IRS or the AC output current IAC is regulated
substantially at the a predetermined current level, and when the
conversion output voltage VDCO is higher than the predetermined
voltage threshold VTH, the conversion output power or the AC output
power PACO is regulated substantially at the a predetermined power
level.
[0049] The present invention has been described in considerable
detail with reference to certain preferred embodiments thereof. It
should be understood that the description is for illustrative
purpose, not for limiting the scope of the present invention. It is
not limited for each of the embodiments described hereinbefore to
be used alone; under the spirit of the present invention, two or
more of the embodiments described hereinbefore can be used in
combination. For example, two or more of the embodiments can be
used together, or, a part of one embodiment can be used to replace
a corresponding part of another embodiment. As an example, the
"constant current mode" and the "constant power mode" can be used
together, such that the wireless power transmitter circuit can have
these two functions at the same time. As another example, the
"constant current mode for the resonant current IRS" and the
"constant power mode for the AC output power PACO" can be used
together, such that the wireless power transmitter circuit can
operate in these two modes to meet corresponding requirements. Note
that the wireless power transmitter circuit may include the
corresponding circuits described in the aforementioned embodiments
to realize the combinations as above. Furthermore, those skilled in
this art can readily conceive variations and modifications within
the spirit of the present invention. For example, in the embodiment
shown in FIG. 3, though current mode circuits (for example but not
limited to the transconductance amplifier circuit 511 and the
current-voltage conversion circuit 512) are used as illustration,
voltage mode circuits can be used to realize the same functions
according to the spirit of the present invention. As another
example, to perform an action "according to" a certain signal as
described in the context of the present invention is not limited to
performing an action strictly according to the signal itself, but
can be performing an action according to a converted form or a
scaled-up or down form of the signal, i.e., the signal can be
processed by a voltage-to-current conversion, a current-to-voltage
conversion, and/or a ratio conversion, etc. before an action is
performed. The spirit of the present invention should cover all
such and other modifications and variations, which should be
interpreted to fall within the scope of the following claims and
their equivalents.
* * * * *