KR20170025517A - Device and Method of using Piezoelectric Transformer for Wireless Power Transmission - Google Patents
Device and Method of using Piezoelectric Transformer for Wireless Power Transmission Download PDFInfo
- Publication number
- KR20170025517A KR20170025517A KR1020150122041A KR20150122041A KR20170025517A KR 20170025517 A KR20170025517 A KR 20170025517A KR 1020150122041 A KR1020150122041 A KR 1020150122041A KR 20150122041 A KR20150122041 A KR 20150122041A KR 20170025517 A KR20170025517 A KR 20170025517A
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- piezoelectric transformer
- wireless power
- power transmission
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- H02J17/00—
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- H01L41/044—
Abstract
Description
The present invention relates to a radio power transmission method and apparatus using a piezoelectric transformer.
Recently, wireless power transmission technology is attracting attention. 1 is a diagram illustrating a conventional wireless power transmission apparatus.
The present invention provides a method and apparatus for transmitting a wireless power using a piezoelectric transformer.
According to an aspect of the present invention, there is provided a piezoelectric transformer comprising: a piezoelectric transformer; And a transmission coil connected to the piezoelectric transformer for transmitting electric power.
According to the present invention, it is possible to reduce the size of the transmission portion of the wireless power transmission circuit system, reduce the electromagnetic disturbance noise, and reduce the power loss as compared with the conventional method.
It also reduces the number of components required for AC to DC power converters in existing wireless power transmission systems, reducing the overall number of components required. Piezoelectric transformers can be used regardless of shape or type (contour, radial, shear, etc.), resonant frequency, and so on.
1 is a diagram illustrating a conventional wireless power transmission apparatus.
2 to 17 are views for explaining a wireless power transmission apparatus and method according to the present invention.
While the invention is susceptible to various modifications and alternative forms, specific embodiments thereof are shown by way of example in the drawings and will herein be described in detail. It is to be understood, however, that the invention is not to be limited to the specific embodiments, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing.
Hereinafter, embodiments according to the present invention will be described in detail with reference to the accompanying drawings.
The present invention relates to a wireless power transmission system using a piezoelectric transformer by combining a conventional wireless power transmission system and a piezoelectric transformer using piezoelectric characteristics, and a method of designing the same.
The method proposed by the present invention is a method using a piezoelectric transformer, which is different from the conventional wireless power transmission system. The piezoelectric transformer according to the present invention generates electricity by an external force and transforms the voltage by using a piezoelectric element that vibrates according to the application of electric power.
Since the piezoelectric transformer has a capacitance at the output terminal, it can resonate to realize a clear sine waveform, so that it can be connected directly to the coil without additional capacitors. Additional matching is possible by connecting a matching circuit. Piezoelectric transformers are generally driven around a resonant frequency or region thereof for maximum efficiency power transmission. Piezoelectric transformers can be fabricated to operate at frequencies that are suitable for wireless power transmission systems, and additional coils can be connected to induction coils or other loads to form a matching circuit. A step-down piezoelectric transformer may be used if a low voltage is needed for wireless power transmission, and a step-up piezoelectric transformer if a high voltage is needed. The gain of the piezoelectric transformer and the gain of the magnetic induction coil can be independently varied to meet the required performance and standard. The " power transmission device " using the piezoelectric transformer corresponds to the transmission part of the wireless power transmission system, but it can be applied to the devices that are the reception part of the wireless power transmission system.
The piezoelectric transformer according to the present invention can be directly connected to the power transmission coil, as shown in Fig. Through this method, the power conversion step can be reduced and the total number of necessary parts can be reduced. Using the characteristics of the piezoelectric transformer, it is possible to reduce the power conversion stages to one level to convert the mains voltage to a high frequency signal required for the power transmission coil to generate a magnetic field.
Further, the piezoelectric transformer according to the present invention can connect the transmission coil using other techniques.
As shown in Fig. 3, a method of additionally connecting a capacitor ( Cres ) between the output terminal of the piezoelectric transformer and the power transmission coil may be used, or an impedance matching may be provided between the output end of the transformer and the power transmission coil A method of additionally connecting an impedance matching circuit for the impedance matching circuit may be used.
Piezoelectric transformers can transmit radio power by supplying voltage and current to the transmission coil using all the resonance modes of the piezoelectric transformer. For example, in a radial mode piezoelectric transformer, a resonance mode of a first fundamental resonance frequency is generally used for a large bandwidth and high efficiency.
5 is a graph illustrating the resonance modes of the piezoelectric transformer. The first resonance mode (fundamental resonance mode) is at 73 kHz. The second resonance mode (2 nd resonance mode) is at 102 kHz. The third resonance mode (3 rd resonance mode) is at 147 kHz. The fourth resonance mode (4 th resonance mode) is at 237 kHz.
The piezoelectric transformer can transmit and receive a receiver identification signal or a ping signal using all the resonance modes of the piezoelectric transformer. At this time, a resonance mode such as power transmission can be used. At this time, the same frequency can be used, and another frequency can be used. For example, a first resonance mode may be used for power transmission, and a third resonance mode with a higher resonance frequency may be used to generate the ping signal.
According to the present invention, one power conversion circuit with a piezoelectric transformer operating with zero voltage switching (ZVS) may be used and the inductor may not be used. This can reduce electromagnetic shield noise (EMI). Inductance can be eliminated by using zero voltage switching technology in a driving circuit for a piezoelectric transformer. In addition, inductors can be avoided by using multiple power conversion circuits with piezoelectric transformers.
According to the present invention, a transmission coil can be manufactured by using a specific material, or can be manufactured by changing the shape (length, number of windings, etc.), size, dimensions, and the like, and adding the output terminal of the piezoelectric transformer and the transmission coil Impedance matching between impedance matching circuits can be performed to obtain optimum efficiency and to improve performance and stability (heat generation, vibration, noise, etc.).
According to the present invention, a piezoelectric transformer can be manufactured by using a specific material, or by changing the shape (length, thickness, and the like), size, dimensions and the like so that the impedance of the output terminal of the piezoelectric transformer, Impedance matching between matching circuits can be used to improve the performance and stability (heat generation, vibration, noise, etc.), leading to optimum efficiency. And the output capacitance of the piezoelectric transformer and the transmission coil can be matched. A good quality piezoelectric transformer design limits the operating temperature to above the limit while operating at higher efficiency.
The wireless power charging system according to the present invention can use a plurality of transmission coils. Also, the wireless power charging system according to the present invention can be applied to a wireless power transmission receiving unit in reverse, and can be used in such a manner that power is received and then rectified and transmitted to a load.
As shown in FIG. 6, the wireless power charging system according to the present invention can easily modify and operate existing data transmission techniques. The output power of the circuit can be adjusted by adjusting the frequency and duty cycle. By measuring the current and voltage of the circuit, the frequency of the piezoelectric transformer or the driving circuit can be changed by analyzing and analyzing the signal transmitted by the receiver.
FIGS. 7 and 8 illustrate a transmitter block diagram of a wireless power charging apparatus according to an embodiment of the present invention, and FIG. 9 illustrates a wireless power charging system according to a specific embodiment of the present invention.
10 shows the output impedance and the phase curve when the input terminal of the piezoelectric transformer is short-circuited.
Figure 11 shows the phase and magnitude of the input of the measured piezoelectric transformer. Point -1 represents the resonance frequency, point-2 represents the anti - resonance frequency, and point-3 represents the maximum phase point. 11 is a diagram when the output of the piezoelectric transformer is in an open state, in a short-circuited state, and when a transmission coil is attached.
Fig. 12 shows the impedance, inductance, and series resistance curves (from 1 kHz to 200 kHz) of the measured transmission coil, and each point is indicated at 1 kHz, 73 kHz, 110 kHz and 175 kHz.
13 is a diagram showing operation data of the piezoelectric transformer when 220 Vrms is applied to the piezoelectric transformer driving circuit.
The four channels are the voltages input to the piezoelectric transformer. The two channels are the currents input to the piezoelectric transformer. One channel is a row switch (Vgs), and two channels are a high-switch (Vgs).
The applied input square wave has a frequency of 71.730 kHz, 50% duty cycle. This is the critical point at which zero voltage switching (ZVS) occurs. Frequencies below this frequency do not reach zero voltage switching (ZVS).
Vgs is the voltage between the gate and the source.
14 shows operation data of the piezoelectric transformer when 220 Vrms is applied to the piezoelectric transformer driving circuit.
The four channels are the voltages input to the piezoelectric transformer. The two channels are the currents input to the piezoelectric transformer. One channel is a row switch (Vgs), and two channels are a high-switch (Vgs).
The applied input square wave has a frequency of 71.940 kHz, 50% duty cycle. At frequencies above this frequency, zero voltage switching (ZVS) is not achieved.
15 shows a transmission coil voltage (1 channel) and a current (2 channels).
The applied input square wave has a frequency of 71.940 kHz, 50% duty cycle.
At frequencies above this frequency, zero voltage switching (ZVS) is not achieved.
16 shows the transmission coil voltage (1 channel) and the current (2 channels).
The applied input square wave has a frequency of 71.730 kHz, 50% duty cycle.
It is the critical point of zero voltage switching (ZVS).
FIG. 17 shows the received coil voltage (1 channel) and current (2 channels).
The input square wave applied to the transmission coil has a frequency of 71.730 kHz, 50% duty cycle.
It is the critical point of zero voltage switching (ZVS).
The receiving coil is attached with 40 Ω. The DC output voltage of the receiving rectifying circuit is 4.23 V.
The above-described technical features may be implemented in the form of program instructions that can be executed through various computer means and recorded in a computer-readable medium. The computer-readable medium may include program instructions, data files, data structures, and the like, alone or in combination. The program instructions recorded on the medium may be those specially designed and constructed for the embodiments or may be available to those skilled in the art of computer software. Examples of computer-readable media include magnetic media such as hard disks, floppy disks and magnetic tape; optical media such as CD-ROMs and DVDs; magnetic media such as floppy disks; Magneto-optical media, and hardware devices specifically configured to store and execute program instructions such as ROM, RAM, flash memory, and the like. Examples of program instructions include machine language code such as those produced by a compiler, as well as high-level language code that can be executed by a computer using an interpreter or the like. The hardware device may be configured to operate as one or more software modules to perform the operations of the embodiments, and vice versa.
As described above, the present invention has been described with reference to particular embodiments, such as specific constituent elements, and limited embodiments and drawings. However, it should be understood that the present invention is not limited to the above- And various modifications and changes may be made thereto by those skilled in the art to which the present invention pertains. Accordingly, the spirit of the present invention should not be construed as being limited to the embodiments described, and all of the equivalents or equivalents of the claims, as well as the following claims, belong to the scope of the present invention .
Claims (1)
A transmission coil connected to the piezoelectric transformer for transmitting electric power,
The wireless power transmission device comprising:
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020150122041A KR20170025517A (en) | 2015-08-28 | 2015-08-28 | Device and Method of using Piezoelectric Transformer for Wireless Power Transmission |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| KR1020150122041A KR20170025517A (en) | 2015-08-28 | 2015-08-28 | Device and Method of using Piezoelectric Transformer for Wireless Power Transmission |
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| Publication Number | Publication Date |
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| KR20170025517A true KR20170025517A (en) | 2017-03-08 |
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| KR1020150122041A KR20170025517A (en) | 2015-08-28 | 2015-08-28 | Device and Method of using Piezoelectric Transformer for Wireless Power Transmission |
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