JP2002209344A - Noncontact power transmission apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly safe noncontact power transmission apparatus which does not heat foreign matters such as a metal piece even if it is placed on a coil in its power supply side. SOLUTION: The noncontact power transmission apparatus arranges, in the secondary side of a transformer in which a primary coil 10 and a secondary coil 20 are structured in a separated loading/unloading manner, a rectifying means, secondary battery B, load circuit Z, signal-generating circuit 4 for generating a signal for load detection and antenna coil 22 for a transmission connected to the output of the signal generator 4, and also arranges, in the primary side of the transformer, a high-frequency inverter, antenna coil 12 for receiving a signal from the transmission antenna 22 and load-detecting circuit 5 for detecting a loading or unloading condition with a signal from the reception antenna coil 12. In this noncontact power transmission apparatus, the load- detecting circuit 5 controls the output of an inverter in synchronization with the detecting operation of the signal from the signal-generating circuit 4.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact power transmission device, for example, in a state where a lighting equipment body which has a built-in secondary battery and can be used without a commercial power supply is electrically insulated from a power supply unit. It is suitable for a luminaire for both use which is supplied with electric power.

[0002]

2. Description of the Related Art (Conventional Example 1) Conventional Example 1 will be described with reference to FIG. FIG. 19 shows the configuration of a lighting stand for dual use. The lighting stand includes a circuit block 31 including a power supply circuit, a lighting circuit, a charging circuit, and a control circuit;
And a switch 33 for switching on / off of the lamp 32
And a power supply cord 37 comprising a pair of conducting wires and the other 35b of the connector, and has a function of charging the secondary battery. With commercial power
The lamp can be turned on even with a secondary battery, and this is an example of a lighting fixture for both use and charging that can be used even without a commercial power supply.

When used in a place where there is a commercial power supply, the power supply cord 37 connects the instrument body 36 to the commercial power supply, and the commercial power supply charges the secondary battery 34 and turns on the lamp 32 via the circuit block 31. When used in a place where there is no commercial power supply, the instrument body 36 and the power cord 37 are separated and used. In this case, the lamp 3
Light 2

The lighting stand includes a mode in which a lamp is turned on by a commercial power source, a mode in which a secondary battery is charged while the lamp is turned on in a commercial power source, a mode in which a secondary battery is charged by a commercial power source, There are five modes: a mode in which the lamp is turned on by the secondary battery, and a mode in which the lamp is not turned on and the secondary battery is not charged. In each mode, the current value supplied from the connector 35 to the appliance body 36 is different. . That is, the appliance body 36 viewed from the connector 35
There is a load fluctuation on the side. Generally, since the contacts of the connector 35 are made of metal, the required current can be supplied to the instrument body 36 regardless of the current. However, when the power cord 37 is removed, the contact of the connector electrically connected to the live line is exposed, so that there is a problem that it is difficult to ensure safety.

(Conventional Example 2) FIG. 20 shows a circuit configuration of Conventional Example 2 (see JP-A-7-46848). This conventional example is an example of a non-contact power supply system for transmitting power in an electrically insulated state using a transformer in which a primary winding and a secondary winding can be separated and joined. In FIG. 20, L1 is the primary winding of the transformer T1, and L2 is the secondary winding of the transformer T1, which are magnetically coupled to each other but can be separated and joined. C0 is a capacitor for impedance matching. The primary winding L1 is connected to the output of a single-type inverter 1a that converts a DC power supply E into a high-frequency power supply.

As an example of use of the non-contact power supply system, as shown in FIG. 21, there is charging of a secondary battery B built in a main body of an electric toothbrush from a commercial power supply. The electric toothbrush body is used separately from the power supply side, but the transformer for transmitting and receiving power is electrically insulated from the housing, so there is no danger of electric shock even when used around water, Is easy to make waterproof structure. However, when the metal piece M is placed on the power supply side coil L1, a magnetic flux loop is formed by the power supply side coil L1 and the metal piece M as shown by a dotted line in FIG. There is a problem that the metal piece M is sent and heated.

(Conventional Example 3) FIG. 23 shows a conventional example in which electric power is not supplied to a metal piece placed on a coil on a power supply side in non-contact power supply. This is the Japanese
FIG. 23 shows a non-contact power transmission device disclosed in Japanese Patent Application Publication No. 0-215530. In FIG. 23, a high-frequency current flows from a DC voltage source E of a power supply unit 1 to a primary coil 10 of a power supply transformer by an inverter circuit 1a. A high frequency voltage is generated in the secondary coil 20 of the load unit 2 magnetically coupled with
The basic configuration of non-contact power supply for charging the secondary battery B is the same as that of the second conventional example. In this conventional example, the power supply circuit 6, the signal generation circuit 7, and the transmission antenna coil 22 are added to the load unit 2, and the reception antenna coil 12, the load detection circuit 8, and the intermittent oscillation control circuit 9 are added to the power supply unit 1. It is provided. The receiving antenna coil 12 is shown in FIGS.
As shown in FIG. 6, the power transmission coils 10 and 20 are wound outside the power transmission magnetic flux loop so as not to be affected by the magnetic flux of the power transmission coils 10 and 20 wound around the cores 11 and 21. They are arranged in the vicinity, thereby reducing the size of the signal transmission / reception circuit.

When the load unit 2 is not mounted on the power supply unit 1, the receiving antenna coil 12 of the power supply unit 1 does not receive a signal from the signal generation circuit 7 of the load unit 2, and the output of the load detection circuit 8 Accordingly, the intermittent oscillation control circuit 9 causes the inverter circuit 1a to operate intermittently. Therefore, since the power supply primary coil 10 is intermittently excited, the metal piece is
Even if it is placed on zero, power is constantly sent and the metal piece does not heat up. On the other hand, when the load unit 2 is mounted on the power supply unit 1, the signal generation circuit 7 of the load unit 2 operates, a high-frequency current flows through the transmission antenna coil 22, and the reception antenna coil 12 coupled thereto is connected. Received as a signal, and the intermittent oscillation control circuit 9 operates the inverter circuit 1a continuously according to the output of the load detection circuit 8. Therefore, the load unit 2 can continuously receive power via the secondary coil 20.

As described above, in this conventional example, almost no power is supplied by the intermittent oscillation of the inverter circuit 1a unless the load section 2 is mounted on the power supply section 1. The pieces hardly heat up.

[0010]

In the conventional example 1, power can be supplied to a load whose supply current changes between lighting and charging, such as a lighting fixture for charging and discharging.
When the power cord is removed, the contacts of the connector are exposed, and there is a problem that it is difficult to ensure safety.

In the second prior art, there is no danger of electric shock because the metal part connected to the live line is not exposed, but when the metal piece is placed on the coil L1 on the power supply side, power is sent to the metal piece. However, there is a problem that the metal piece is heated.

In the conventional example 3, the antenna coils 12 and 2
2 is installed outside the power transmission magnetic flux loop so as not to be affected by the magnetic flux of the power transmission coils 10 and 20, but the primary coil 10 and the secondary coil 20 are detachable and the load is reduced. If it is not installed or the coupling state is bad, magnetic flux will leak. Leaked magnetic flux is transmitted to power transmission coil 10
And 20 are detected as signals by the receiving antenna coil 12 when the antenna coil 12 or 22 is linked to the antenna coil 12 or 22 installed near the receiving antenna coil 20. Particularly, in a load in which the power supply current changes, such as a lighting fixture for mixed use, the metal piece is connected to the primary coil 1.
When placed on zero, a large amount of power may be supplied. In this case, there is a problem that the magnetic flux leaking is large, the signal is detected as a signal equivalent to a normal load to the receiving antenna coil 12, and power is continuously supplied to the metal piece to heat it.

The present invention has been made in view of the above points, and provides a highly safe non-contact power transmission device which does not heat even if a foreign substance such as a metal piece is placed on a power supply side coil. As an issue.

[0014]

According to the present invention, in order to solve the above-mentioned problems, as shown in FIG. 1, an inverter for converting a commercial power supply to a high-frequency power supply and an output of the inverter are applied. It has a primary winding 10 and a secondary winding 20 magnetically coupled to the primary winding 10.
And a transformer in which the secondary winding 20 is configured to be detachable, a rectifier for obtaining a DC voltage from the output of the secondary winding 20, and a secondary battery B charged by the output of the rectifier. A load circuit Z fed from the output of the rectifier or the secondary battery B, a signal generation circuit 4 for generating a load detection signal using the output of the secondary winding as a power supply, and an output of the signal generation circuit 4 Transmitting antenna coil 2 connected to
2, a receiving antenna coil 12 for receiving a signal from the transmitting antenna coil 22, and a load detecting circuit 5 for detecting the presence or absence of a load based on a signal from the receiving antenna coil 12. In the transmission device, the load detection circuit 5 controls an output of the inverter in synchronization with a signal detection operation from the signal generation circuit 4. Further, as another means for solving the same problem, the frequency of the signal generated by the signal generation circuit 4 may be set lower than the switching frequency of the inverter. Furthermore, a means may be provided for detecting a temperature rise immediately below a portion where the magnetic flux of the primary winding interlinks, and the inverter may be stopped or intermittently oscillated when the temperature rise is detected.

[0015]

Embodiments of the present invention will be described with reference to the drawings. (Embodiment 1) A circuit configuration diagram of Embodiment 1 of the present invention is shown in FIG.
Shown in The power supply section 1 performs full-wave rectification of the commercial power supply AC with a diode bridge DB, and smoothes it with a smoothing capacitor C0 to obtain a DC voltage. The DC voltage obtained at the smoothing capacitor C0 is applied to the switching elements Q1,
It is applied to the series connection circuit of Q2. The switching elements Q1 and Q2 are turned on / off at a high frequency complementarily by the output of the control circuit 5. Therefore, the switching element Q1
The potential at the connection point between Q2 and Q2 vibrates at a high frequency. A series circuit of a resonance capacitor C1 and a primary coil 10 of a non-contact power supply transformer is connected between a connection point of the switching elements Q1 and Q2 and one end of the smoothing capacitor C0. An antenna coil 12 for load detection is connected to the control circuit 5 of the switching elements Q1 and Q2. The load detecting antenna coil 12 is a primary coil 1 of a non-contact power supply transformer.
0 is wound around the same core 11.

Next, the load unit 2 converts the high frequency output of the secondary coil 20 of the non-contact power supply transformer into diodes D1 and D2.
, And smoothed by the capacitor C2 to obtain a DC voltage. A secondary battery B is connected to both ends of the capacitor C2 via a charge / discharge control circuit 3, and a secondary coil 2
The secondary battery B is charged with power supplied from 0. A series circuit of the secondary battery B and the charge / discharge control circuit 3 is connected to a load Z via a switch S. A diode D3 for rectifying and smoothing the output of the secondary coil 20 and a smoothing capacitor C3 are connected between one end of the secondary coil 20 and the ground of the load section 2, and the signal oscillation circuit 4 is connected to the smoothing capacitor C3. The output of the signal oscillation circuit 4 is the transmission antenna coil 22
It is connected to the. The transmitting antenna coil 22 transmits a signal to the power supply unit 1 and is wound around the same core 21 as the secondary coil 20 of the non-contact power feeding transformer.

As shown in FIG. 2 or FIG. 3, the configuration of the transformer for non-contact power supply is to perform non-contact power supply in a form in which C-shaped cores 11 and 21 are connected to each other, and a primary coil 10 for power transmission and The secondary coil 20 is attached to both arms of the core,
They are wound in the same number of times so that the magnetic flux in the core is in the same direction and connected in series. The signal transmission antenna coils 12 and 22 are wound around the power transmission cores 11 and 21, and the winding is not affected by the magnetic flux loop of the power transmission.
The coil is wound around the outside of the core as shown in FIG. 2 and the coil is arranged outside the magnetic flux loop. As shown in FIG. 3, the coil is divided and wound around both arms of the core by the same number of times as in the power transmission coil. However, there is a type in which magnetic fluxes passing through divided coils are wound in opposite directions so as to cancel each other and are connected in series. In any case, if there is no leakage in the magnetic flux of the power supply coil, no voltage is generated in the load detection antenna coil.

FIG. 4 shows a block diagram of the control circuit 5 for the switching elements Q1 and Q2. a1 to a5 and b1 to b4 represent connection points of the same symbols in FIG. The control circuit 5 includes a controller 51, a timer 52, and a sampling circuit 53, and periodically detects the presence or absence of a load by signal transmission, and operates to stop the power transmission inverter when detecting the load. Here, the signal of the load detection antenna coil 12 is V12, and the output of the sampling circuit 53 is V12.
53, the output of the transmitting antenna coil 22 on the load side is V2
Let it be 2.

The operation of this embodiment will be described with reference to FIG. The voltage applied to the power supply coil 10 is V10.
First, the operation when the load is at a predetermined position will be described. The controller 51 operates the inverter only for a relatively short period T11. Then, the smoothing capacitor C3 in the load unit 2 is charged, and the oscillation circuit 4 starts oscillating within the period T11. Next, the inverter constituted by the switching elements Q1 and Q2 is stopped for a relatively short load detection period T12. During this time, the sampling circuit 53 samples the signal V12 of the load detecting antenna coil 12, and the controller 51 determines the presence or absence of a load from the output V53 of the sampling circuit 53. By the way, the oscillation circuit 4 keeps oscillating by the voltage charged in the smoothing capacitor C3. Therefore, the output V53 of the sampling circuit 53 is V53 = V
The controller 51 determines that there is a load.

Then, during the next relatively long period T13,
The inverter continues to operate. The operation from T11 to T13 is repeated for one cycle. At the same time as the end of the period T13, a short operation period T21 at the beginning of the next cycle starts.
Therefore, when there is a load, intermittent oscillation with a long inverter operation period occurs.

Next, an operation when the load is removed is shown in a cycle T4. If the load is removed in the middle of the previous cycle, the output V53 of the sampling circuit 53 becomes V53 = 0 in the load detection period T42 because the oscillation circuit of the load section does not exist even if the inverter oscillates in the period T41 at the beginning of the cycle. , The controller determines that there is no load. Then, the inverter keeps stopping for the next relatively long period T43. This T
The operations from 41 to T43 are repeated for one cycle. At the same time as the end of the period T43, the short operation period T at the beginning of the next cycle
51 starts. Therefore, when there is a load, intermittent oscillation with a long inverter stop period occurs.

In this embodiment, when the load is detected,
Since the power transmission inverter is stopped, the sampling signal for load detection is not affected by noise generated by the inverter. Therefore, there is an effect that it is possible to accurately determine the presence or absence of a load.

(Embodiment 2) The circuit configuration of this embodiment is the same as that of FIGS. 1 to 4 of Embodiment 1, but the operation of the controller 51 of the power supply section 1 is different from that of FIG. FIG. 6 shows operation waveforms of each unit in the present embodiment. This embodiment is different from the first embodiment in that the duty ratio of the switching elements Q1 and Q2 is controlled so that the operation of the switching elements Q1 and Q2 is not stopped during the load detection period but the output of the inverter is reduced. . As described above, by reducing the output V11 of the inverter during the load detection period, the ratio of the sampling signal for load detection to the noise generated by the inverter can be increased without interrupting the power transmission by the non-contact power supply. Accordingly, since the influence of noise can be reduced, it is possible to accurately determine the presence or absence of a load. If the DC voltage is variable using a chopper circuit as the DC power supply circuit serving as the power supply of the inverter, the output may be reduced by lowering the DC power supply voltage during the load detection period.

(Embodiment 3) In the present embodiment, the load detection signal is set lower than the frequency of the power transmission inverter to facilitate load detection. Generally, when a load detecting antenna coil is installed near a power transmission transformer as shown in FIG. 2, a signal leaking from the power transmission transformer to the antenna coil is a harmonic of an inverter signal. Accordingly, the load detection signal is a signal having a frequency lower than the frequency of the inverter, and the load detection signal V60 is transmitted to the controller 51 via the high-frequency cutoff filter 60 as shown in FIG.
Send. In this embodiment, without stopping the inverter,
There is an effect that the influence of noise can be reduced by frequency discrimination and a reliable load detection can be performed.

(Embodiment 4) The circuit configuration of this embodiment is the same as that of FIGS. 1 to 4 of Embodiment 1, but the operation of the controller 51 of the power supply unit 1 is different from that of FIG. FIG. 8 shows operation waveforms of each unit in the present embodiment. This embodiment is different from the first embodiment in that the drive frequency of the switching elements Q1 and Q2 is reduced during the load detection period. The frequency of the communication signal for load detection is set higher than the inverter drive frequency. During the load detection period, the inverter drive frequency is lowered and the difference from the oscillation frequency of the load-side oscillation circuit 4 is increased. Then, the influence of noise generated by the inverter can be reduced without interrupting power transmission by non-contact power supply, and accurate determination of the presence or absence of a load can be performed.

(Embodiment 5) This embodiment is an example in which information other than the presence / absence of a load is added to a communication signal for load detection. The signal oscillation circuit 4 of the load section differs from the first embodiment in that the signal oscillation circuit 4 detects the voltage VB of the secondary battery B as shown in FIG. 9 and outputs an AM-modulated signal based on the detected value. In this case, the reception signal V12 of the load detection coil is
Has a peak value proportional to the voltage VB. Therefore, the output V53 of the sampling circuit 53 also becomes an output proportional to the voltage VB of the secondary battery B. Therefore, when the output V53 of the sampling circuit 53 is low, that is, when the voltage VB of the secondary battery B is low, the controller 51 can control the frequency and the duty ratio of the switching elements Q1 and Q2 so as to increase the charging current. Conversely, when the voltage VB of the secondary battery B is high, the switching element Q
1 and Q2.

As shown in FIG. 10, even if the digital value obtained by A / D converting the voltage VB of the secondary battery B is AM-modulated and transmitted to the control circuit 5, the D / A conversion is performed in the control circuit 5. Good. The modulation method is not limited to AM modulation.
M modulation or another modulation method may be used.

In the present embodiment, by adding the voltage information of the secondary battery to the communication signal for load detection, it is possible to detect the different load and to control the overcharge and the overdischarge of the secondary battery. Having.

(Embodiment 6) Referring to FIGS.
The arrangement of the contactless power supply transformer will be described. For applications that are usually installed on a wall, such as bracket lighting,
The power supply unit 1 is fixedly installed on the wall, and the load unit 2 with a built-in rechargeable battery is usually used by attaching it to the power supply unit 1. When moving and using it, remove it from the power supply unit 1 and turn on the secondary battery. I do. In this case, the method of mounting the power supply unit 1 and the load unit 2 and the method of installing the power supply transformer are as follows.
When the foreign object is placed, the metal piece M stays on the power supply unit 1. However, when the contact surface of the transformer is vertical as shown in FIG. 12, the metal piece M falls down, and does not stay on the power supply unit 1. In the present embodiment, the possibility that foreign matters such as metal pieces are placed can be reduced by making the contact surface of the transformer vertical.

If the contact surface of the transformer is curved as shown in FIG. 13, even if a foreign matter such as a metal piece M touches the contact surface between the power supply unit 1 and the load unit 2, the foreign material can be prevented from being caught. .
Further, in the case of a pot core in which the transformer cores are arranged concentrically as shown in FIG. 14, if the contact surface of the transformer is dome-shaped, it is possible to prevent foreign matter from being caught.

(Embodiment 7) FIG. 15 shows a circuit configuration diagram of Embodiment 7 of the present invention. In the present embodiment, a metal piece placed on the primary coil 10 of the power supply unit 1 is not determined by the presence or absence of a signal, but is detected by detecting a temperature near the primary coil 10 of the power supply transformer. Things. FIG.
As shown in FIG. 6, a temperature sensing element 30 such as a thermistor is installed immediately below a portion where the magnetic flux of the primary coil interlinks. When the temperature sensing element 30 detects a temperature rise, the inverter stops oscillating or intermittently oscillates. This is to prevent the metal foreign matter M from being heated.

Further, even when power is supplied to the load section 2, the power supply transformer has a certain temperature rise. Therefore, when the period during which the temperature rise is lower than when a normal load is connected continues, it is determined that there is no load, and the oscillation of the inverter is not continued, so that the safety can be further increased.
Although the present embodiment may be implemented alone, the safety can be increased by combining the detection control with the power supply unit 1 and the load unit 2 by signal transmission / reception.

(Eighth Embodiment) FIG. 17 shows a circuit diagram of an eighth embodiment of the present invention. The configuration of this embodiment is the same as that of the first embodiment except for a communication method for load detection.
The communication method according to the present embodiment is characterized in that a light emitting diode LED is used for signal transmission on the load side and a phototransistor Ptr is used on the reception side. Light transmissive resin is used in a portion where the phototransistor Ptr of the power supply unit 1 and the light emitting diode LED of the load unit 2 face each other.
In this embodiment, without being affected by electromagnetic noise,
There is an effect that the load can be detected.

(Embodiment 9) FIG. 18 shows a circuit configuration diagram of Embodiment 9 of the present invention. This embodiment relates to a load form, and uses a series circuit of a light emitting diode LED and a resistor R as a load Z. A constant current circuit may be used instead of the resistor R. Since the light emitting diode LED can be stably lighted with a simpler stabilizing circuit than the discharge lamp load FL as a lighting load for lighting with the secondary battery B, the device can be reduced in size and weight.

[0035]

According to the first to fourth aspects of the present invention, the effect of noise received from the power transmission inverter at the time of receiving a signal from the signal generating circuit is reduced, so that accurate signal reception can be achieved. According to the fifth aspect of the present invention, since the frequency of the signal of the signal generation circuit is lower than the switching frequency of the inverter, the signal generation circuit is less susceptible to the noise generated by the inverter, and has an effect of performing accurate signal reception. According to the invention of claim 6, by detecting the temperature rise immediately below the portion where the magnetic flux of the primary winding interlinks, it is possible to detect that the metal piece is placed near the primary winding. Have.

[Brief description of the drawings]

FIG. 1 is a circuit diagram according to a first embodiment of the present invention.

FIG. 2 is a perspective view showing one configuration example of a transformer used in the first embodiment of the present invention.

FIG. 3 is a perspective view illustrating another configuration example of the transformer used in the first embodiment of the present invention.

FIG. 4 is a block circuit diagram illustrating a configuration of a signal transmission unit according to the first embodiment of the present invention.

FIG. 5 is a waveform chart for explaining the operation of the first embodiment of the present invention.

FIG. 6 is a waveform chart for explaining the operation of the second embodiment of the present invention.

FIG. 7 is a block circuit diagram illustrating a configuration of a signal transmission unit according to a third embodiment of the present invention.

FIG. 8 is a waveform chart for explaining the operation of the fourth embodiment of the present invention.

FIG. 9 is a block circuit diagram illustrating one configuration example of a signal transmission unit according to a fifth embodiment of the present invention.

FIG. 10 is a block circuit diagram illustrating another configuration example of the signal transmission unit according to the fifth embodiment of the present invention.

FIG. 11 is a perspective view showing one arrangement example of a power transmission transformer used in Embodiment 6 of the present invention.

FIG. 12 is a perspective view showing another arrangement example of the power transmission transformer used in the sixth embodiment of the present invention.

FIG. 13 is a perspective view showing still another arrangement example of the power transmission transformer used in the sixth embodiment of the present invention.

FIG. 14 is a perspective view showing another arrangement example of the power transmission transformer used in Embodiment 6 of the present invention.

FIG. 15 is a circuit diagram according to a seventh embodiment of the present invention.

FIG. 16 is a perspective view showing one arrangement example of a power transmission transformer used in Embodiment 7 of the present invention.

FIG. 17 is a circuit diagram according to an eighth embodiment of the present invention.

FIG. 18 is a circuit diagram according to a ninth embodiment of the present invention.

FIG. 19 is an explanatory diagram showing the configuration of Conventional Example 1.

FIG. 20 is a circuit diagram of a second conventional example.

FIG. 21 is an explanatory diagram showing a configuration of an electric toothbrush using the power transmission device of Conventional Example 2.

FIG. 22 is an explanatory diagram for explaining a problem of Conventional Example 2.

FIG. 23 is a circuit diagram of a third conventional example.

FIG. 24 is a perspective view showing one arrangement example of a power transmission transformer used in Conventional Example 3.

FIG. 25 is a perspective view showing another arrangement example of the power transmission transformer used in Conventional Example 3.

FIG. 26 is a perspective view showing still another arrangement example of the power transmission transformer used in Conventional Example 3.

[Description of Signs] 1 power supply unit 2 load unit 3 charge / discharge control circuit 4 signal oscillation circuit 5 control circuit

Claims (6)

[Claims] An inverter for converting a commercial power supply to a high-frequency power supply; a primary winding to which an output of the inverter is applied;
A transformer having a secondary winding magnetically coupled to the secondary winding, the primary winding and the secondary winding being configured in a detachable manner, and a DC voltage from an output of the secondary winding. A rectifier, a secondary battery charged by an output of the rectifier, a load circuit supplied from the output of the rectifier or the secondary battery, and a load detection circuit using the output of the secondary winding as a power supply. A signal generation circuit that generates a signal; a transmission antenna coil connected to an output of the signal generation circuit; a reception antenna coil for receiving a signal from the transmission antenna coil; and a reception antenna coil. A non-contact power transmission device having a load detection circuit that detects the presence or absence of a load based on the signal of (b), wherein the load detection circuit controls an output of the inverter in synchronization with a signal detection operation from the signal generation circuit. Non-contact power transmission apparatus characterized by. 2. The wireless power transmission device according to claim 1, wherein the load detection circuit stops the oscillation of the inverter in synchronization with an operation of detecting a signal from the signal generation circuit. 3. The wireless power transmission device according to claim 1, wherein the load detection circuit reduces the output of the inverter in synchronization with a detection operation of a signal from the signal generation circuit. 4. The wireless power transmission device according to claim 1, wherein the load detection circuit lowers a switching frequency of the inverter in synchronization with a detection operation of a signal from the signal generation circuit. 5. An inverter for converting commercial power to high-frequency power, a primary winding to which the output of the inverter is applied,
A transformer having a secondary winding magnetically coupled to the secondary winding, the primary winding and the secondary winding being configured in a detachable manner, and a DC voltage from an output of the secondary winding. A rectifier, a secondary battery charged by an output of the rectifier, a load circuit supplied from the output of the rectifier or the secondary battery, and a load detection circuit using the output of the secondary winding as a power supply. A signal generation circuit that generates a signal; a transmission antenna coil connected to an output of the signal generation circuit; a reception antenna coil for receiving a signal from the transmission antenna coil; and a reception antenna coil. A non-contact power transmission device having a load detection circuit for detecting the presence or absence of a load based on the signal of (1), wherein a frequency of a signal generated by the signal generation circuit is lower than a switching frequency of the inverter. Non-contact power transmission device according to. 6. An inverter for converting commercial power to high-frequency power, a primary winding to which an output of the inverter is applied,
A transformer having a secondary winding magnetically coupled to the secondary winding, the primary winding and the secondary winding being configured in a detachable manner, and a DC voltage from an output of the secondary winding. A non-contact power transmission device comprising: a rectifying unit to be obtained; a secondary battery charged by an output of the rectifying unit; and a load circuit supplied with power from the output of the rectifying unit or the secondary battery. A non-contact power transmission device comprising: means for detecting a temperature rise immediately below a portion where a magnetic flux interlinks.