JP2008104319A - Noncontact power transmission device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a noncontact power transmission device which suppresses currents flowing through a power transmission coil and a receiving coil, downsizes the power transmission/receiving coils, and uses inexpensive electronic components without using special electronic components. <P>SOLUTION: The noncontact power transmission device supplies electric power through electromagnetic induction to the receiving coil L2 of a receiving unit from the power transmission coil L1 of the power transmission device, wherein the receiving unit is arranged in a housing of electronic equipment using a low voltage. In the power transmission device, a voltage step-up circuit 12 is provided to change a DC low-voltage input into a high voltage, and the current flowing through the power transmission coil L1 is suppressed to a predetermined current, then a voltage generated in the receiving coil L2 is changed by a voltage step-down circuit 22 to obtain a predetermined low voltage. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a non-contact power transmission device for portable electronic equipment.

  In recent years, various portable digital devices such as mobile phones, digital cameras, and liquid crystal televisions are frequently used on a daily basis. Such portable devices usually have a built-in low voltage rechargeable battery and need to be charged appropriately. Various methods are used for this charging, but non-contact power using electromagnetic induction that can be easily charged just by placing it on a charging stand without connecting a charging adapter or cord to a portable device. Transmission devices have been proposed.

  FIG. 1 shows a general contactless power transmission circuit. In the figure, the power transmission device 10 has a resonance capacitor C1 connected in parallel with the power transmission coil L1, and a control switching element Q1 connected in series with the power transmission coil L1. Further, an oscillation circuit 11 and a drive coil L3 are connected to the switching element Q1.

The power receiving device 20 includes a resonant capacitor C2 connected in parallel with the power receiving coil L2, and has a rectifying and smoothing circuit 21 at both ends thereof. And it is the non-contact electric power transmission apparatus which makes the power receiving coil L2 mounted in the housing | casing different from the power transmission coil L1 oppose, and transmits electric power from the power transmission coil L1 to the power receiving coil L2.
For example, a conventional circuit diagram in Patent Document 1.

In the power transmission device 10, when the DC input voltage DC is low, the current flowing through the power transmission coil L1 increases.
Further, since the power receiving device 20 uses a resonant circuit with the power receiving coil L2 and the resonant capacitor C2, the output current increases when a low voltage output is obtained, and the current flowing through the power receiving coil L2 is more than twice the output current. Effective current flows.

As described above, in the case of a low voltage input or a low voltage output, heat is generated because a large current flows through the power transmission coil or the power reception coil. In order to reduce this heat generation, a coil using a multi-core wire such as a litz wire or a braided wire is generally required.
However, when a multi-core wire is used, it is difficult to reduce the size of the coil. In addition, the coupling between the power transmission coil and the power reception coil is also deteriorated and the characteristics are deteriorated.

In the case of the AC wide input specification, the current flowing through the power transmission coil becomes large at low voltage input, and the current flowing through the power transmission coil is small at high voltage input, but a high voltage is applied to the resonance capacitor and control switching element on the power transmission side. Therefore, a special electronic component with a high withstand voltage is required.
JP-A-2005-278400

  In view of the above-described problems, the present invention provides a non-contact power transmission device that suppresses current flowing in a power transmission coil and a power reception coil, reduces the size of the power transmission / reception coil, and uses inexpensive electronic components without using special electronic components. It is to provide.

In order to solve the above-described problem, the present invention provides a non-contact power transmission device that supplies power to a power receiving coil of a power receiving device disposed in a casing of an electronic device using a low voltage by electromagnetic induction from a power transmitting coil of the power transmitting device. A step-up circuit is provided for raising the DC low voltage input to a high voltage, the current flowing through the power transmission coil is suppressed to a predetermined current, and the voltage generated in the power receiving coil is obtained by the step-down circuit.
Furthermore, a step-up / step-down circuit is provided for the AC wide input, a current flowing in the power transmission coil is suppressed to a predetermined current, and a voltage generated in the power receiving coil is obtained by a step-down circuit to obtain a predetermined low voltage. A non-insulated ON / OFF type flyback converter is used for the booster circuit or the step-up / step-down circuit.

  With the above configuration, it is possible to realize a non-contact power transmission device that can reduce power loss in an electronic device using a low voltage and can obtain a stable output in a power receiving device without using a large and expensive electronic component.

FIG. 2 is a circuit block diagram showing a first embodiment of the non-contact power transmission apparatus of the present invention.
2 is different from FIG. 1 in that a booster circuit 11 is provided between the low-voltage DC input power source DC and the power transmission device 10, and a step-down circuit 22 is provided between the power reception device 20 and the output Vout. It is. The same circuits as those in FIG. The dot (•) in the circuit diagram indicates the polarity of the coil.

  In FIG. 2, a low-voltage DC input power source DC is boosted to a predetermined boosted voltage required by the booster circuit 12, a stable high voltage is applied to the power transmission device 10, and a current flowing through the power transmission coil L <b> 1 of the power transmission device 10 is increased. The power is transmitted to the power receiving apparatus 20 by reducing the power. And since the high receiving voltage is obtained in the receiving coil L2 of the receiving device 20, the output of a rectification smoothing circuit also becomes a high voltage. A step-down circuit 22 is provided to obtain a predetermined low stable DC voltage (large current) Vout required by a portable device or the like.

FIG. 3 is a circuit block diagram showing a second embodiment of the non-contact power transmission apparatus of the present invention.
In FIG. 3, the difference from FIG. 1 is the case of AC wide input, and the rectifying and smoothing circuit 15 for converting AC to DC between the input AC and the power transmission device 10 and the wide input are set to a predetermined high voltage. The step-up / step-down circuit 14 is provided, and the step-down circuit 22 is provided between the power receiving device 20 and the output Vout. The same circuits as those in FIG. The dot (•) in the circuit diagram indicates the polarity of the coil.

  In FIG. 3, the AC wide input AC increases the DC output voltage of the rectifying and smoothing circuit 15 for converting AC to DC to a predetermined voltage required by the step-up / down circuit 14 for setting the wide input to a predetermined high voltage. High voltage is applied, a stable high voltage is applied to the power transmission device 10, the current flowing through the power transmission coil L <b> 1 of the power transmission device 10 is reduced, and power is transmitted to the power reception device 20. And since the high receiving voltage is obtained in the receiving coil L2 of the receiving device 20, the output of a rectification smoothing circuit also becomes a high voltage. A step-down circuit 22 is provided to obtain a predetermined low stable DC voltage (large current) Vout required by a portable device or the like.

  Thus, in the power transmission device, since a high voltage is applied by the booster circuit or the step-up / step-down circuit, the current flowing through the power transmission coil can be reduced and self-heating can be suppressed. Further, since the power receiving device can also receive a high voltage and reduce the current flowing through the power receiving coil, self-heating in the power receiving coil can be suppressed. Furthermore, a low voltage and large current output can be obtained by reducing the high voltage output of the power receiving device to a low voltage of a portable device that requires a high voltage circuit.

Next, examples of each circuit are shown in the drawings.
FIG. 4 shows an example of a booster circuit that obtains a predetermined high DC voltage Vout from a low DC output Vin provided in the previous stage of the power transmission device used in the first embodiment.
The booster circuit in FIG. 4 is a basic booster chopper circuit, and a series circuit of an inductor L and a diode D is connected so that a current flows from the input terminal Vin to the output terminal Vout. And GND, a switching element Q is connected, and a capacitor C is connected between the output terminal Vout and GND.

  FIG. 5 shows an example of a non-insulated ON / OFF type flyback converter circuit used in place of the step-up chopper circuit. A series circuit of the primary coil Lp of the transformer T and the switching element Q is connected between the input terminal Vin and GND, and a series circuit of the secondary coil Ls of the transformer T and the diode D is connected between the output terminal Vout and GND. Further, a capacitor C is connected between the output terminal Vout and GND.

FIG. 6 shows an example of a step-up / step-down circuit that obtains a predetermined DC voltage Vout from the AC wide voltage input Vin provided in the previous stage of the power transmission device used in the second embodiment.
The step-up / step-down circuit in FIG. 6 is a basic step-up / step-down chopper circuit. A series circuit of a switching element Q and an inductor L is connected between the input terminal Vin and the output side GND, and a connection point between the switching element Q and the inductor L is A diode D is connected between the output terminals Vout, and a capacitor C is connected between the output terminal Vout and the input side GND.
As the step-up / down circuit, the non-insulated ON / OFF type flyback converter circuit shown in FIG. 5 may be used.

  FIG. 7 shows an example of a step-down circuit for setting the high DC output Vin of the power receiving device used in the first and second embodiments to a predetermined low DC voltage Vout. The step-down circuit in FIG. 7 is a basic step-down chopper circuit, in which a series circuit of a switching element Q and an inductor L is connected between input terminals Vin and Vout, and a diode is connected between a connection point of the switching element Q and the inductor L and GND. D is connected, and a capacitor C is connected between the output terminal Vout and GND.

  The feedback circuit for stabilizing the output in the booster circuit, non-isolated ON / OFF type flyback converter circuit, step-up / step-down circuit, and step-down circuit described above applies a control signal to the control terminal of the switching element Q. Since it is obtained by driving, it is not described here.

  As mentioned above, although one form of the non-contact electric power transmission apparatus of this invention has been described, it is not restricted to this. In the embodiment, the RCC resonant converter is shown, but other self-excited oscillation and separately-excited oscillation circuits may be used. The resonance capacitor on the power transmission side uses parallel resonance connected in parallel with the power transmission coil, but may use series resonance in series connection. Further, a synchronous rectification method may be used for the step-down circuit on the power receiving side.

Block circuit diagram showing a conventional non-contact power transmission device The block circuit diagram which shows the 1st form of the non-contact electric power transmission apparatus of this invention The block circuit diagram which shows the 2nd form of the non-contact electric power transmission apparatus of this invention Example of a booster circuit used in the non-contact power transmission device of the present invention Non-isolated ON / OFF flyback converter circuit example used in the non-contact power transmission apparatus of the present invention Example of a step-up / down circuit used in the non-contact power transmission apparatus of the present invention Example of step-down circuit used in the non-contact power transmission apparatus of the present invention

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Power transmission apparatus 11 Oscillation circuit 12 Boosting circuit 14 Buck-boost circuit 15, 21 Rectification smoothing circuit 20 Power receiving apparatus 22 Buck circuit L1 Power transmission coil L2 Power reception coil L3 Drive coil C1, C2 Resonance capacitor Q1 Switching element

Claims (3)

In a non-contact power transmission device that supplies power from a power transmission coil of a power transmission device to a power reception coil of a power reception device disposed in a casing of an electronic device that uses low voltage by using electromagnetic induction, a booster circuit that makes a DC low voltage input a high voltage A non-contact power transmission apparatus characterized in that a current flowing through the power transmission coil is suppressed to a predetermined current, and a predetermined low voltage is obtained from the voltage generated in the power receiving coil by a step-down circuit. In a non-contact power transmission device that supplies power by electromagnetic induction from a power transmission coil of a power transmission device to a power reception coil disposed in a casing of an electronic device that uses low voltage, a step-up / step-down circuit is provided for an AC wide input, A non-contact power transmission device characterized in that a current flowing through the power transmission coil is suppressed to a predetermined current, and a voltage generated in the power receiving coil is obtained by a step-down circuit. 3. The non-contact power transmission device according to claim 1, wherein a non-insulated ON / OFF flyback converter is used for the booster circuit or the step-up / step-down circuit.

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