JP3283962B2 - Power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a non-contact type power supply for transmitting power by electromagnetic induction to a load portion detachable from a main body, and particularly to controlling power transmission in accordance with a state of a load. To a power supply that enables it.

[0002]

2. Description of the Related Art Conventionally, there has been known a power supply device in which a load side is detachable from a power supply main body. Particularly, in recent years, a connection between the power supply main body and the load side has been considered in consideration of operability on the load side. A so-called non-contact type power supply device that does not have a mechanical contact structure and transmits and supplies electric power to a load side by electromagnetic induction has been proposed (Japanese Patent Laid-Open No. 4-295284).

[0003]

In order to realize efficient power transmission in this type of power supply, a primary coil is disposed near the outer surface of the frame of the main body, and when the load is mounted, It is desired that the secondary coil on the load side be structurally magnetically coupled to the primary coil of the power supply body.

However, when the above-described structure is adopted in a power supply device using electromagnetic induction, the primary coil is disposed near the outer surface of the main body, and in the non-contact type, the state of the load side is changed by a mechanical switch or the load side. It is difficult to control the power transmission because there is no wiring to return the detection signal directly from the detection circuit to the main body side. When a metal such as a coin or a pin is placed on the metal, the metal is heated by electromagnetic induction. For this reason, there is a danger of burns, fires, and the like, and there is a problem that the frame of the power supply device is melted and deformed. In addition, when this type of power supply device is used as a battery charger, there is a problem that charge control is not sufficient because wiring for returning a storage battery voltage detection signal for full charge control to the main body side cannot be provided. .

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems, and has as its object to provide a power supply device in which the above-described state change on the load side is detected by the main body and power transmission control is performed. I do.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a power supply device for transmitting power by electromagnetic induction to a load portion detachable from a main body. The primary coil has a first coil and a second coil which is magnetically coupled to a secondary coil built in the load unit when the primary coil is mounted, and is connected in series. And the detection coil is connected to the first
It is magnetically coupled to the coil (claim 1).

Further, in the power supply device according to the first aspect,
Detecting means for detecting a level change in the induced voltage of the detection coil caused by the short-circuit of the second coil; and an oscillation stop circuit for stopping the oscillating operation of the primary coil when the detecting means detects the level change. (Claim 2).

Further, in the power supply device according to the first aspect,
Detecting means for detecting whether or not the load unit is attached to the main body from a level change of the induced voltage of the detection coil; and display means for performing a display operation based on the detection of the level change by the detecting means. (Claim 3).

Further, in the power supply device according to the first aspect,
The load unit is a rechargeable storage battery, based on a detection unit that detects whether or not the load unit is attached to the main body from a level change of the induced voltage of the detection coil, based on the detection of the level change by the detection unit. Timer means for oscillating the primary coil for a predetermined charging time (claim 4).

Further, in the power supply device according to claim 2,
An intermittent drive circuit for intermittently driving the oscillation stop circuit is provided.

[0011] In the power supply device according to claim 4,
Oscillation control means for intermittently driving the oscillation operation of the primary coil after the predetermined charging time is provided (claim 6).

[0012]

According to the first aspect of the present invention, the main body is turned on and the primary coil is driven to oscillate. In this state, when the load section is mounted on the main body, the main body is turned on.
The second coil of the next coil and the secondary coil on the load side are magnetically coupled, and power can be transmitted to the load side. If a metal foreign matter is erroneously placed in the vicinity of the second coil of the main body when the load unit is not mounted, the second coil is substantially short-circuited, and a voltage is generated in the first coil. This first
The level change of the voltage generated by the coil is detected as the level change of the induced voltage of the detection coil. Further, when the load portion is correctly mounted at a predetermined position of the main body, the voltage level generated by the second coil slightly changes (decreases) by an amount corresponding to the load. This change appears as a change in the first coil, and this level change is similarly detected by the detection coil. As described above, since the state change on the load side can be detected on the main body side, power transmission control according to the state on the load side can be performed.

According to the second aspect of the present invention, if the metal is erroneously mounted near the second coil of the main body and the second coil is substantially short-circuited when the load portion is not mounted, the first coil is thereby disconnected.
Voltage is generated in the coil. When the level change of the generated voltage is detected by the detecting means, the oscillation drive of the primary coil is stopped. When the oscillation drive is stopped, the voltage generated by the first coil returns to the original level, and the oscillation restarts.
As described above, when the metal foreign matter is erroneously placed, the oscillation operation is performed intermittently.

According to the third aspect of the present invention, when the load portion is correctly mounted on the predetermined position of the main body, the voltage level generated by the second coil slightly changes (decreases) by an amount corresponding to the load.
This change appears as a change in the first coil. When this level change is detected by the detection means, it is determined that charging of the load unit has been started, and a display indicating that fact is displayed.

According to the fourth aspect of the present invention, when the load portion is correctly mounted on the predetermined position of the main body, the voltage level generated by the second coil slightly changes (decreases) by an amount corresponding to the load.
This change appears as a change in the first coil. When this level change is detected by the detecting means, it is determined that the charging of the load section has started, and the oscillation drive is continued for a predetermined charging time.

According to the invention described in claim 5, the second of the main body is provided.
If the oscillating operation is performed intermittently as a result of a metal foreign matter being erroneously placed near the coil, the intermittent oscillating operation will be performed more intermittently. The oscillation time is further reduced.

According to the sixth aspect of the present invention, after the load portion is correctly mounted on the predetermined position of the main body and charging is performed for a predetermined charging time, the charging operation is continuously performed intermittently. And auxiliary charging (trickle charging).

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of a power supply device according to the present invention will be described with reference to FIGS. FIG. 3 is a perspective view showing a cordless telephone as an example of an electric device to which the present invention is applied. The load unit 2 as a receiver is mounted on the power supply unit 1 as shown in FIG. 3, so that the load unit 2 having a built-in storage battery is mounted on the power supply unit 1. Thus, power transmission and its control are performed as described later. The load built in the load unit 2 is:
It is not limited to a storage battery, but may be a motor or the like.

Next, the circuit configuration of the power supply unit 1 and the load unit 2 will be described. 1 and 2 are circuit diagrams showing a first embodiment of a power supply device according to the present invention. FIG.
3 is a circuit diagram of the load unit 2. FIG.

An AC power source such as a commercial power source can be connected between the input terminals via a cord K. This AC power is rectified and smoothed by the rectifier diode BD and the capacitor C1 to obtain a DC power supply. This DC power supply has a second
A coil LC, a first coil L1, and a switching element field effect transistor (FET) 3 are connected in series.

In the FET 3, resistors R22 and R23 are connected in series between the source and ground, a series oscillation circuit including a feedback coil L2 and a capacitor C2 is connected between the gate and drain, and a diode D2 and a transistor are connected between the gate and ground. A series circuit consisting of Q1 is connected.

The detecting coil L3 includes a rectifying diode D1.
And the smoothing capacitor V3, and the generated smoothing voltage V
3 are produced. Further, it is connected to a connection point between the resistors R22 and R23 via a Zener diode ZD and a resistor. The Zener diode ZD has a predetermined Zener voltage. That is, the Zener voltage is set to a value that turns on when the generated smoothed voltage V3 reaches Vx as described later. When the Zener diode ZD turns on, the transistor Q1
Is turned on to drop the gate of FET3 to ground.

The positive electrode of the DC power supply and the feedback coil L
An activation resistor R21 for activating the FET3 is connected between the connection point of the capacitor 2 and the connection point of the capacitor C1.

On the other hand, in the load section 2, a secondary coil L0 is provided.
As will be described later, it is disposed so as to be magnetically coupled to the second coil LC, and is connected in parallel with a storage battery (load) B via a diode D0 and a smoothing capacitor C0.

Next, the positional relationship between the coils will be described with reference to FIGS. FIG. 4 is a perspective view showing each coil inside the power supply unit 1 and the load unit 2, and FIG. 5 is a partial cross-sectional view showing a state where the load unit 2 is mounted on the power supply unit 1.

Inside the power supply unit 1, a printed wiring board PB on which the above-described circuit components are mounted is provided. The first coil L1 is in close contact with the printed wiring board PB.
A core around which the feedback coil L2 and the detection coil L3 are wound is arranged. On the other hand, the second coil LC is disposed in a state of being wound around the core at a protruding portion 12 provided substantially at the center of the upper surface of the frame 11 of the power supply unit 1, away from the printed wiring board PB. Thus, the first coil L1, the feedback coil L2, and the detection coil L3 are magnetically coupled to each other,
The second coil LC is disposed so as not to be magnetically coupled to each of these coils.

As shown in FIG. 5, the lower surface of the frame 21 of the load portion 2 is provided with a recess 22 having a diameter slightly larger than at least the peripheral diameter of the projecting portion 12. The secondary coil L0 is wound around the concave portion 22. Then, when the concave portion 22 of the load portion 2 is loosely fitted to the projecting portion 12 of the power supply portion 1 and the load portion 2 is mounted on the power supply portion 1,
The second coil LC and the secondary coil L0 are magnetically coupled.

Next, the operation of this circuit will be described with reference to FIGS. FIG. 6 shows the protruding portion 1 of the power supply unit 1.
2 is a diagram showing a state where a metal object such as a ring is placed on 2,
(A) is a perspective view, (b) is a partial cross-sectional view. FIG. 7 is a voltage waveform diagram of each part showing the operation of the first embodiment.

When the cord K of the power supply unit 1 is connected to an AC power supply, a gate voltage is applied by the charging voltage of the capacitor C1 by the starting resistor R21, and the FET 3 starts to turn on.
The feedback coil L based on the voltage between both ends of the first coil L1
The FET3 is rapidly turned on by the induced voltage of 2. When the source current of the FET 3 increases and the voltage generated at the resistor R23 rises to a predetermined level, the transistor Q
1 turns on, the gate voltage of FET3 decreases,
3 turns off. Due to such oscillation of the FET 3, a voltage as shown in FIG. 7 is generated at both ends of the second coil LC.

Here, as shown in FIG.
When a metal object 5 such as a ring or a coin is placed around the protruding portion 12 of the power supply unit 1 where C is disposed, the second coil LC
7 is constrained by the metal object 5 to be in a short circuit state, and as shown in FIG. 7, the voltage across the second coil LC is suppressed to a low level substantially similar to the short circuit state.
Due to the energy on the primary side due to the oscillation of T3, the voltage across the first coil L1 connected in series to the second coil LC increases. Accordingly, the voltage generated in the detection coil L3 magnetically joined to the first coil L1 also increases, and this detection coil L3
3, the generated smoothed voltage V3 after smoothing is changed from Va to Vx
To exceed the sum of the Zener voltage of the Zener diode ZD and the generated voltage of the resistor connected to the anode side (hereinafter, this sum of voltages is referred to as Zener voltage for convenience of explanation), and the transistor Q1 Is turned on, and the oscillation of the FET 3 stops.

When the oscillation of the FET 3 stops, no voltage is generated in the detection coil L3, and the capacitor C3 discharges. However, while the voltage of the capacitor C3 is higher than the Zener voltage, the oscillation of the FET 3 continues to stop. You.
When the voltage of the capacitor C3 falls below the Zener voltage, the transistor Q1 is turned off, and F
ET3 starts oscillating.

As described above, when the metal object 5 is placed around the protruding portion 12 of the power supply unit 1 in which the second coil LC is provided, the FET 3 is switched to intermittent oscillation.
Can be relatively suppressed. Accordingly, it is possible to prevent burns, fires, and the like, and also prevent deformation of the frame 11 of the power supply unit 1 due to heat.

Next, a second embodiment will be described with reference to FIG. The positional relationship between the coils is the same as in the first embodiment. FIG. 8 is a circuit diagram of the power supply unit 1 according to the second embodiment. The same components as those in the first embodiment are denoted by the same reference numerals.

In the second embodiment, as in the first embodiment, power transmission control is performed when a metal object is placed. A comparator IC1 comprising an operational amplifier is provided in place of the Zener diode ZD and the transistor Q1. Things.

That is, a series circuit of voltage dividing resistors R1 and R2 is connected to the positive electrode of the capacitor C3.
The connection point between R1 and R2 is a comparator IC via a resistor R6.
1 is connected to the-input terminal.

On the other hand, the dividing resistors R3 and R4 are added to the reference voltage Vcc.
Are connected, and the connection point of the voltage dividing resistors R3 and R4 is a resistor R
5 is connected to the + input terminal of the comparator IC1. The output terminal of the comparator IC1 is connected to the cathode of the diode D2.

The smoothed voltage V generated by the detection coil L3
3 is a voltage V2 divided by the voltage dividing resistors R1 and R2, and a voltage Vref2 obtained by dividing the reference voltage Vcc by the voltage dividing resistors R3 and R4.
Are compared by the comparator IC1.

Then, at the voltage Va under no load, V2 <Vr
Each voltage dividing resistance value is set so as to be ef2, and a high level signal is output from the comparator IC1 to turn off the diode D2. On the other hand, when the metal object
2 and the smoothed voltage V3 generated by the detection coil L3 is V
When the voltage rises to x, V2> Vref2, and a low level signal is output from the comparator IC1 to turn on the diode D2, so that the gate of the FET3 becomes low level and oscillation stops.

Next, a third embodiment will be described with reference to FIGS. The positional relationship between the coils is the same as in the first embodiment. FIG. 9 is a circuit diagram of the power supply unit 1 according to the third embodiment. The same components as those in the first embodiment are denoted by the same reference numerals.

In the third embodiment, in addition to the circuit of the first embodiment, a comparator IC2 comprising an operational amplifier and a light emitting diode (LED) 6 are provided. That is,
A series circuit of voltage dividing resistors R7 and R8 is connected to the positive electrode of the capacitor C3.
12 is connected to the-input terminal of the comparator IC2.

The voltage dividing resistors R9 and R1 are added to the reference voltage Vcc.
0 is connected, and the connection point of the voltage dividing resistors R9 and R10 is connected to the + input terminal of the comparator IC2 via the resistor R11. Further, the reference voltage Vcc and the comparator I
LED6 is connected to the output terminal of C2 via a resistor R13.
Is connected. The LED 6 is disposed at an appropriate position on the outer surface of the frame 12.

Then, the smoothed voltage V generated by the detection coil L3
3 is a voltage V1 divided by the voltage dividing resistors R7 and R8 and a voltage Vref obtained by dividing the reference voltage Vcc by the voltage dividing resistors R9 and R10.
Are compared by the comparator IC2.

Next, the operation of this circuit will be described with reference to FIG. The oscillation operation of the FET 3 and the operation when the metal object is placed on the protruding portion 12 of the power supply unit 1 are the same as those in the first embodiment.

When the load section 2 is correctly mounted at a predetermined position of the power supply section 1, the voltage corresponding to the load on the secondary coil L0 side, that is, the voltage across the second coil LC decreases by ΔVc. Then, the voltage across the first coil L1 connected in series with the second coil LC increases by ΔV1 by an amount corresponding to the energy reduction in the second coil LC.
The voltage V3 induced in the detection coil L3 magnetically coupled to the first coil L1 also slightly increases (in FIG. 10, the generated smoothing voltage V3 is Va to Vx1).

Then, the generated smoothed voltage V3 at no load is V
In a, if each voltage dividing resistance value is set so that V1 <Vref, a high level signal is output from the comparator IC2 to turn off the LED6. On the other hand, the load 2
When the smoothing voltage V3 generated by the detection coil L3 rises to Vx1, if the voltage dividing resistance values are set so that V1> Vref, a low level signal is output from the comparator IC1 to turn on the LED6. To

Therefore, when the load unit 2 is mounted on the power supply unit 1, the LED 6 is turned on to indicate that the load unit 2 is correctly mounted. Also, the load unit 2 is
When it is not properly mounted on the LED, the LED 6 does not light up, so that the user can be notified.

Next, a fourth embodiment will be described with reference to FIGS.
It will be described based on. The positional relationship between the coils is the same as in the first embodiment. FIG. 11 is a circuit diagram of the power supply unit 1 of the fourth embodiment. The same components as those in the third embodiment are denoted by the same reference numerals.

In the fourth embodiment, a timer circuit T is added to the circuit of the third embodiment. That is, the timer circuit T has its reset input terminal RESET connected to the output terminal of the comparator IC2, and its output terminal P1 connected to the cathode of the diode D2.

When a low-level signal is input to a reset input terminal RESET, the timer circuit T starts a counting operation for timing, outputs a high-level signal from an output terminal P1, and sets a predetermined charge. When a predetermined time is measured, a low level signal is output from the output terminal P1.

The operation of this circuit will be described with reference to the timing chart of FIG. When the load section 2 is mounted on the power supply section 1, as described in the third embodiment, the low level signal is output from the comparator IC2 to turn on the LED 6, and the timer circuit T starts counting operation. When a predetermined time has elapsed, the output terminal P1
Outputs a low-level signal, turns on the diode D2, and stops the oscillation operation of the FET3.

When the oscillation of the FET 3 stops, no voltage is generated in the detection coil L3, so that the input voltage V = 0 to the minus input terminal of the comparator IC2, and a high level signal is output from the comparator IC2. , LED 6 is turned off.

As described above, in the fourth embodiment, it is possible to perform charging control for charging for a predetermined time by the timer circuit T in order to perform full charging. In addition, the mounting of the load unit 2 can be displayed by turning on the LED 6, and the completion of charging can be displayed by turning off the LED 6.

Next, a fifth embodiment will be described with reference to FIGS.
It will be described based on. The positional relationship between the coils is the same as in the first embodiment. FIG. 13 is a circuit diagram of the power supply unit 1 of the fifth embodiment. The same components as those in the fourth embodiment are denoted by the same reference numerals.

In the fifth embodiment, a pulse control circuit PC is added to the circuit of the fourth embodiment.
A charge display circuit 7 is provided instead of the resistor R13 and the LED 6. The pulse control circuit PC is interposed between the timer circuit T and the diode D2, and the charging display circuit 7 is connected to the output terminal P1 of the timer circuit T.

The timer circuit T normally outputs a high-level signal from the output terminal P1, and outputs a reset input terminal R
When a low-level signal is input to the ESET, a counting operation for timing starts, and the output signal from the output terminal P1 is switched to a low-level signal. Then, when a predetermined time for charging set in advance is counted, the output signal from the output terminal P1 is switched to a high-level signal again.

The charging display circuit 7 has a plurality of display elements such as LEDs arranged at appropriate locations on the outer surface of the frame 12, and a low level signal is input from the output terminal P1 of the timer circuit T to the input terminal P4. During the period, the display element is turned on to indicate that the battery is being charged. Further, when the input signal to the input terminal P4 is switched from a low level signal to a high level signal, a different display element is turned on by this switching to indicate that charging is completed.

The pulse control circuit PC outputs a pulse signal having a preset duty ratio from the output terminal P2 only during the period when the low level signal is being input to the input terminal P3.

Next, the operation of this circuit will be described with reference to the timing chart of FIG.

When there is no load, the timer circuit T
A high-level signal is output from the output terminal P1, and during this time, the charging display circuit 7 is not operating. Further, the pulse control circuit PC outputs a pulse signal from the output terminal P2, and the FET 3 oscillates intermittently.

Therefore, in the load standby state, intermittent oscillation occurs, so that power consumption can be reduced during this period.

Next, when the load section 2 is mounted on the power supply section 1, the charging operation is started and the comparator IC is started.
2, a low-level signal is input to the reset input terminal RESET of the timer circuit T, and the counting operation of the timer circuit T is started. In addition, the charging display circuit 7 indicates that charging is in progress.

When a predetermined time for charging has elapsed and the storage battery B is fully charged, the pulse control circuit P
A pulse signal is output from the output terminal P2 of C, and FET3
Intermittently oscillates.

Therefore, by the intermittent oscillation, after the charging of the storage battery B is completed, the supplementary charging by the trickle charging current can be performed.

Next, the operation when a metal object is placed near the second coil LC of the power supply unit 1 will be described with reference to the timing chart of FIG. FIG. 15 is a timing chart showing the range of FIG. 14 in detail.

When a metal object is placed near the second coil LC in the no-load state, the electromotive force generated in the first coil L1 increases during the Ton period when the high level signal is being output from the output terminal P2. The electromotive force generated in the detection coil L3 also increases. The voltage V generated in the detection coil L3
3, the transistor Q1 is turned on via the Zener diode ZD, and the oscillation of the FET3 is stopped.

When the oscillation stops, the detection coil L
3, the generated smoothing voltage V3 decreases, and the Zener diode Z
The transistor Q1 that has been turned on via D is turned off, and the FET3 starts oscillating again. This is repeated to perform intermittent oscillation. On the other hand, the intermittent oscillation is stopped during the Toff period when the low level signal is being output from the output terminal P2.

As described above, when a metal object is placed at the time of intermittent oscillation in a no-load state, the intermittent oscillation is caused by the output terminal P2.
Because of the output of, further intermittent oscillation occurs.
3 is further shortened. Therefore,
Heating of the metal object can be further suppressed.

[0068]

As described above, according to the present invention, when the voltage level of the second coil changes due to a change in the state of the load, the change in the voltage level of the first coil caused by this change is detected by the detection coil. Is detected as a change in the level of the induced voltage, so that the state on the load side can be known by the power supply unit on the primary side, even though the power supply device is an electromagnetic induction type, so that the power according to the load state Transmission control can be enabled.

When the metallic foreign matter is erroneously placed in the vicinity of the second coil of the main body, the switching operation is performed so that the primary coil oscillates intermittently. Can be.

When the detection coil detects that the voltage level of the second coil slightly changes by an amount corresponding to the load of the load section, the display means is displayed, so that the load section is correctly positioned at a predetermined position in the main body. It can be notified that it is attached.

Further, since the oscillating operation of the primary coil is performed only for a predetermined time after the load portion having the storage battery is correctly mounted at a predetermined position of the main body, it is possible to control the full charge of the storage battery.

Further, when the metal foreign matter is erroneously placed near the second coil of the main body and the oscillation operation is performed intermittently, the intermittent oscillation operation is further performed intermittently. In addition, the heating of the foreign metal can be further suppressed.

Further, after the load section is correctly mounted on the predetermined position of the main body and charging is performed for a predetermined charging time, the charging operation is performed intermittently, so that auxiliary charging (trickle charging) is performed. It can be performed.

[Brief description of the drawings]

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

FIG. 2 is a circuit diagram showing a load unit of the first embodiment of the power supply device according to the present invention.

FIG. 3 is a perspective view showing a cordless telephone as an example of an electric device to which the present invention is applied.

FIG. 4 is a perspective view showing each coil inside a power supply unit and a load unit.

FIG. 5 is a partial cross-sectional view showing a state where a load unit is mounted on a power supply unit.

6A and 6B are diagrams showing a state in which a metal object is placed on a protruding portion of a power supply unit, wherein FIG. 6A is a perspective view and FIG. 6B is a partial cross-sectional view.

FIG. 7 is a voltage waveform diagram of each part showing the operation of the first embodiment.

FIG. 8 is a circuit diagram showing a power supply unit of a second embodiment of the power supply device according to the present invention.

FIG. 9 is a circuit diagram showing a power supply unit of a power supply device according to a third embodiment of the present invention.

FIG. 10 is a voltage waveform diagram of each part showing the operation of the third embodiment.

FIG. 11 is a circuit diagram showing a power supply unit of a fourth embodiment of the power supply device according to the present invention.

FIG. 12 is a timing chart showing the operation of the fourth embodiment.

FIG. 13 is a circuit diagram showing a power supply unit of a power supply device according to a fifth embodiment of the present invention.

FIG. 14 is a timing chart showing the operation of the fifth embodiment.

FIG. 15 is a timing chart showing the range of FIG. 14 in detail.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply part 2 Load part 3 Field effect transistor (FET) 5 Metallic object 6 Light emitting diode (LED) 7 Charging display circuit 11, 21 Frame 12 Projection part 22 Depression B Storage battery BD Rectifier diode C0, C1, C2, C3 Capacitor D0, D1, D2 Diode IC1, IC2 Comparator L1 First coil L2 Feedback coil L3 Detection coil LC Second coil L0 Secondary coil PC Pulse control circuit P1, P2 Output terminal P3, P4 Input terminal Q1 Transistor R1-R13, R21-R23 Resistance T timer circuit ZD Zener diode

Continuation of the front page (58) Field surveyed (Int. Cl. ⁷ , DB name) H02M 3/28 H02J 7/00 301 H02J 17/00 H02M 7/537 H04M 19/08

Claims (6)

(57) [Claims] 1. A power supply device for transmitting power to a load unit detachable from a main body by electromagnetic induction, a primary coil driven to oscillate upon receiving power and a detection coil detecting a state of the load unit. The primary coil includes a first coil and a second coil magnetically coupled to a secondary coil built in the load unit when mounted, and the second coil is connected in series. A power supply device magnetically coupled to one coil. 2. A power supply device according to claim 1, wherein said detecting means detects a level change of an induced voltage of said detecting coil caused by a short circuit of said second coil, and said detecting means detects said level change. A power supply device comprising: an oscillation stop circuit that stops the oscillation operation of the primary coil. 3. The power supply device according to claim 1, wherein detecting means for detecting whether or not the load unit is mounted on the main body from a level change of the induced voltage of the detection coil, and detecting the level change by the detecting means. And a display means for performing a display operation based on the power supply. 4. The power supply device according to claim 1, wherein the load section is a rechargeable storage battery, and detects whether or not the load section is attached to the main body from a change in the level of an induced voltage of the detection coil. And a timer means for oscillating the primary coil for a predetermined charging time based on the detection of the level change by the detection means. 5. The power supply device according to claim 2, further comprising an intermittent drive circuit for intermittently driving said oscillation stop circuit. 6. The power supply device according to claim 4, further comprising an oscillation control means for intermittently driving an oscillation operation of said primary coil after said predetermined charging time.