JPH1083436A - Power supply system - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply system which can supply enough power with small electrodes. SOLUTION: In this system, a terminal unit 2 contains electrodes S3 and S4, load RL which is connected to the electrodes S3 and S4 and a capacitor C which is connected between the electrodes S3 and 84. A body system 1 is provided with electrodes S1 and S2 which confront with the electrodes S3 and S4 of the unit 2 respectively, a variable frequency oscillator OSC, a tuning coil L which is electranagnetically connected to the oscillator OSC and also connected to the electrodes S1 and 82 and a control circuit A. High voltage can be induced to a tuning circuit even without making the electrodes S1 to S4 so large by controlling the oscillation frequency of the oscillator OSC so that it may coincide with the tuning frequency of the tuning circuit that comprises the capacitor C, the coil L, the interelectrode capacitance of the electrodes S1 and S3 and the interelectrode capacitance of the electrodes S2 and S4 by the circuit A.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device, and more particularly to a power supply device applied to a non-contact IC card or the like which supplies power by bringing a power supply source and a power receiving side into close proximity. Things.

[0002]

2. Description of the Related Art Conventionally, as a method of supplying electric power to an IC card or the like, an electric contact is provided on the IC card or the like and the electric contact is connected to a power supply. On the other hand, it was weak and lacked reliability. In order to solve this, conventionally, as a device for supplying electric power in a non-contact manner, coils are provided on both an IC card and a power supply source,
A method of supplying power by electromagnetic coupling has been proposed.

However, in the method of supplying power by electromagnetic coupling, a magnetic field is naturally generated. Therefore, providing a power supply device by electromagnetic coupling to an index IC for identifying magnetic products such as video tapes and floppy disks has a problem in that magnetic products are adversely affected.

[0004]

As a method for supplying electric power in a non-contact manner without using the above-described electromagnetic coupling, for example, as described in Japanese Patent Application Laid-Open No. 63-9589, power is supplied using capacitive coupling. There was a way. However, the method described in this publication has a problem that the supplied power cannot be increased unless the size of the counter electrode is considerably increased. Therefore, an object of the present invention is to provide a power supply device capable of supplying a sufficiently large power with a small electrode.

[0005]

In order to achieve the above object, a power supply apparatus according to the present invention comprises a first and a second electrode and a first and a second electrode in a power supply such as a card. , And a capacitor connected between the first and second electrodes, and a third and a third electrode respectively facing the first and second electrodes on the power supply side in the power supply. And a tuning coil electromagnetically coupled to the variable frequency oscillator and connected to the third and fourth electrodes. The power supply further adjusts the oscillation frequency of the variable frequency oscillator to the tuning frequency of the tuning circuit including the capacitor, the tuning coil, the first and third inter-electrode capacitances, and the second and fourth inter-electrode capacitances. Control means.

[0006] Regarding the tuning circuit, the capacitance of the capacitor in the power supply is C1, the capacitance between the first electrode and the third electrode is C2, and the capacitance between the second electrode and the fourth electrode is C1. Assuming that the capacitance is C3, the total capacitance C of a series circuit of these three capacitances is 1 / C1 + 1 / C2 + 1 / C3 = 1 /
C. Here, C1 is constant, but C2 and C3 vary depending on the distance and inclination between the power-supplied body and the power-supplied body. Therefore, the value of the total capacitance C also varies.

Here, the tuning frequency f of the tuning circuit is expressed by the following (formula 1). f = 1 / 2π√LC (1) where L is the inductance of the tuning coil. As described above, since the value of the total capacitance C varies.
The value of the tuning frequency f also varies depending on the distance and the inclination between the power-supplied body and the power-supplied body.

In this state, when the control means controls the oscillation frequency of the variable frequency oscillator to tune to the tuning frequency f of the tuning circuit, a high voltage is induced in the tuning circuit,
Large current flows. Then, the capacitor in the power supply connected to the tuning circuit is charged by the large current, and a low impedance alternating current can be supplied to the load from both ends of the capacitor.

[0009]

FIG. 1 shows an embodiment of a power supply device according to the present invention. In FIG. 1, the power supply device of the present embodiment includes a main body device 1 and a terminal unit 2. The terminal unit 2 is a card-shaped unit that is mechanically coupled to the main unit 1 when in use and can be detached from the main unit 1 when not in use, and a plurality of types are prepared.

The main unit 1 includes an oscillator OSC having a variable oscillation frequency, a coil L electromagnetically coupled to the oscillator OSC, and a first electrode S1 and a second electrode S2 connected to both ends of the coil L, respectively. And a control circuit A. Further, the terminal unit 2 includes a third electrode S3 and a fourth electrode S4, a capacitor C having both ends connected to these electrodes S3 and S4, and a load RL connected to both ends of the capacitor C. ing.

First and second electrodes S1, S in main unit 1
2 and the third and fourth electrodes S3 and S4 in the terminal unit 2.
Are provided on surfaces facing each other when the terminal unit 2 is mechanically coupled to the main unit 1. Thereby, a capacitance CS1-3 is generated between the first electrode S1 provided in the main body device 1 and the third electrode S3 provided in the terminal unit 2, and the second electrode provided in the main body device 1 is formed. A capacitance CS2-4 is generated between S2 and the fourth electrode S4 provided in the terminal unit 2.

At this time, as shown in FIG. 2, a series circuit CS is formed by three capacitors: the above-mentioned capacitance CS1-3, the capacitor C provided in the terminal unit 2, and the above-mentioned capacitance CS2-4. Is configured. Further, a tuning circuit T is configured by the series circuit CS and the coil L provided in the main device 1. The above-described control circuit A controls the oscillation frequency of the oscillator OSC built in the main device 1 so as to match the oscillation frequency of the tuning circuit T.

The surfaces of the main unit 1 and the terminal unit 2 are made of an insulator, and the first to fourth electrodes S1 to S1 are formed.
The surface of S4 is also insulated.

FIG. 2 is a diagram showing a circuit configuration of the power supply device shown in FIG. In FIG. 2, the output of the oscillator OSC is extracted from a tuning coil L electromagnetically coupled to the oscillation coil. As described above, this tuning coil L,
The tuning circuit T is configured by the series capacitor CS including the first and third inter-electrode capacitances CS1-3, the capacitor C, and the second and fourth inter-electrode capacitances CS2-4.

The load RL in the terminal unit 2 is connected to the capacitor C in parallel. The capacitance value of the capacitor C can be selected to be a sufficiently large value compared to the first and third inter-electrode capacitances CS1-3 and the second and fourth inter-electrode capacitances CS2-4. Even when connected in parallel, the Q value of the tuning circuit T can be increased.

Further, the control circuit A detects a phase difference between the output voltage of the oscillator OSC and the output voltage of the tuning circuit T, and feeds back the oscillation frequency of the oscillator OSC so as to have a specific phase difference. Thereby, the oscillation frequency of the oscillator OSC is adjusted to the tuning frequency f of the tuning circuit T.

The following is a description of specific numerical examples. Here, it is assumed that the capacitance of the capacitor C is 100 pF and the inductance of the coil L is 63.3 μH. The area of each of the first to fourth electrodes S1 to S4 is 2 cm.
^{In 2} , it is assumed that the distance between the electrodes during use is 1 mm, and the relative permittivity of the insulator is 3. Therefore, the capacitances CS1-3 and CS2-4 between the two sets of electrodes are both 8.3 pF, and the total capacitance of the series circuit CS including the three capacitors is about 4 pF. Therefore, the tuning frequency f of the tuning circuit T is approximately 10
MHz.

In practice, the capacitance CS1 between two pairs of electrodes
-3 and CS2-4 vary ± 40%, so the tuning frequency f varies ± 20%. Further, when the temperature change and the variation of the tuning coil L are included, the variation width is ± 30%. In contrast, by setting the oscillation frequency variable range of the oscillator OSC sufficiently wide, the oscillation frequency can be adjusted to the tuning frequency f of the tuning circuit T.

As means for adjusting the oscillation frequency of the oscillator OSC by the control circuit A to tune to the tuning frequency f, the load of the oscillator OSC becomes heavy at the time of tuning and the oscillation amplitude decreases, or the current consumption of the oscillator OSC decreases. Or a means for detecting a change, a means for detecting a current flowing through the coil L, and controlling the current to be maximum.
There are means for detecting the voltage between terminals of the tuning circuit T and controlling the voltage to be maximum.

FIG. 3 shows an example of the configuration of the control circuit A. FIG. 3 corresponds to the third example described above, and detects the phase difference between the voltage between the terminals of the tuning circuit T (the voltage of the tuning coil L) and the oscillation waveform of the oscillator OSC. It shows an example in which control is performed so that the phase difference becomes a set value.

That is, when the voltage waveform of the oscillator OSC and the voltage waveform of the coil L are electromagnetically coupled to the polarity approaching the same phase when the oscillation frequency is too low, the polarity approaches the opposite polarity when the oscillation frequency is too high, and at the tuning point. The voltage waveform of the coil L has a phase delay of about 45 to 90 degrees with respect to the voltage waveform of the oscillator OSC.

The phase lag amount becomes small when the coupling between the oscillator OSC and the coil L is strengthened or the power supplied from both ends of the capacitor C is increased, and approaches 45 degrees. In addition, when the power supply is made smaller or the power supply power is reduced, the angle approaches 90 degrees. Practically, if the amount of phase lag is within this range, the difference between the voltage amplitudes induced in the coil L is small, so that there is no problem.

Further, in the example shown in FIG. 3, when the oscillation frequency deviates from the tuning frequency f, it is possible to determine whether to increase or decrease the oscillation frequency from the value of the phase shift.
There is an advantage that it is easy to control and can be configured with a simple feedback loop. As a phase detection circuit, a circuit having a phase difference of 90 degrees at the center point of the phase detection operation is known. For example, a bi-differential multiplication circuit and an exclusive OR (EXOR) circuit are typical examples. is there.

FIG. 3 shows an example in which the double differential type multiplying circuit D is used as a phase detecting circuit. The double differential type multiplication circuit D functions as a phase detection circuit, and the oscillator OS
The phase difference between the voltage waveform of C and the voltage waveform of coil L is detected.

In FIG. 3, first and second voltage dividing circuits AT
T1 and ATT2 are used to prevent the voltage obtained from the oscillator OSC and the coil L from being too large, so that the dual differential type multiplying circuit D used as a phase detection circuit becomes a load and does not lower the Q value of the circuit. It is.

The low-pass filter LP extracts a frequency control signal from the output of the bi-differential type multiplication circuit D as a phase detection circuit, converts it to a convenient DC level as a control signal for the oscillator OSC, and provides a feedback loop. Has the function of making the polarity of negative feedback.

A technique using a variable capacitance diode for changing the oscillation frequency of the oscillator OSC is known, but a detailed description thereof is omitted here.

Here, as an operation example, when a load of 10 KΩ is connected as a dummy load to both ends of the capacitor C,
A voltage of 100 Vp-p is induced at both ends of the coil L. As a result, a voltage of 4 Vp-p is obtained at both ends of the capacitor C, and power of 0.2 mW is supplied. That is, during one period of 10 MHz, 20 × 10 ^-12
Energy of J (J: joule) is supplied.

The current flowing through the tuning circuit T is 2
5 mAp-p. The energy stored in the tuning circuit T is 5000 × 10 ⁻¹² J, and the Q value of the tuning circuit T is about 50.
00 × 10 ⁻¹² J of energy is consumed during one cycle of 10 MHz. This can be alleviated by using a coil L having a lower loss, but in reality, the outer shape of the coil L becomes too large, and there is no problem particularly in this level of power supply.

Since the power supply device according to the present embodiment has the configuration as described in detail above, the counter electrode S
Inducing a high voltage in the tuning circuit T by controlling the oscillation frequency of the oscillator OSC to be tuned to the tuning frequency f of the tuning circuit T without increasing the size of 1, S3 and S2, S4 so much. Can be. For this reason,
Sufficiently large electric power can be supplied via the minute interelectrode capacitance.

[0031]

As described above, the power supply device of the present invention can supply power in a non-contact manner without relying on unstable contact between electrodes. At this time, by controlling the oscillation frequency of the variable frequency oscillator to be tuned to the tuning frequency of the tuning circuit, it is possible to supply a sufficiently large electric power without making the size of the electrodes so large. In addition, since it has a function of automatically adjusting the oscillation frequency with respect to a change in coupling capacitance caused by mechanical coupling, it can operate stably. Further, since the surface of the electrode can be covered with an insulator, protection of the electrode is easy. Further, according to another feature of the present invention, since the boosting is performed by using the high impedance utilizing the high Q value of the tuning circuit, the power consumption can be reduced. For this reason, it is hard to become an unnecessary radiation source, and shielding can also be made easily.

[Brief description of the drawings]

FIG. 1 is a diagram showing one embodiment of a power supply device according to the present invention.

FIG. 2 is a diagram illustrating an example of a circuit configuration of the power supply device illustrated in FIG. 1;

FIG. 3 is a diagram illustrating an example of a control circuit that can be used in the power supply device of the present invention.

[Explanation of symbols]

 Reference Signs List 1 main unit 2 terminal unit OSC oscillator T tuning circuit A control circuit L coil S1 to S4 electrode C capacitor CS1-3 first and third inter-electrode capacitance CS2-4 second and fourth inter-electrode capacitance RL load ATT1, ATT2 Voltage divider D Double differential type multiplication circuit LP Low-pass filter

Claims (3)

[Claims] 1. A power supply apparatus comprising: a power supply; and a power supply for supplying power to the power supply, wherein the power supply includes a first electrode and a second electrode. And the first,
A load connected to the second electrode; and a capacitor connected between the first and second electrodes, wherein the power supply body is connected to the third and the third electrodes respectively facing the first and second electrodes. A fourth electrode, a variable frequency oscillator, electromagnetically coupled to the variable frequency oscillator,
A tuning coil connected to a fourth electrode, and a tuning frequency of a tuning circuit including the capacitor, the tuning coil, the first and third interelectrode capacitances, and the second and fourth interelectrode capacitances. And a control means for controlling the oscillation frequency of the variable frequency oscillator to match. 2. The first and second electrodes, a load connected to the first and second electrodes, a capacitor connected between the first and second electrodes, and the first and second electrodes. A third and a fourth electrode respectively opposed to the second electrode; a variable frequency oscillator; a tuning coil electromagnetically coupled to the variable frequency oscillator and connected to the third and fourth electrodes; Control for controlling the oscillation frequency of the variable frequency oscillator to match the tuning frequency of a tuning circuit including the tuning coil, the first and third inter-electrode capacitances, and the second and fourth inter-electrode capacitances. Means for supplying power to the load via the tuning circuit. 3. The capacitance of the capacitor is set to a value sufficiently larger than the capacitance between the first and third electrodes and the capacitance between the second and fourth electrodes. 3. The power supply device according to 1 or 2.