Noncontacting power transfer device

Abstract: A primary winding T 1 as anoscillation winding T 1 is intermittently oscillation-driven and the resultant driving signal is used as a signal for detecting an appliance body B. A power supply body A receives the response signal from the appliance body B to detect the appliance body B. An intermittent driving means M includes the induction winding T 2 wound on the same core as the oscillation winding T 1 and a diode D 1 and capacitor C 2 for rectifying/smoothing the voltage induced in the induction winding T 2 . A control transistor Q 2 operated by the output voltage V 1 of the intermittent driving means M is connected to the control end of an oscillation transistor Q 1 so that the oscillation transistor Q 1 is intermittently driven by an oscillation voltage V C .

Description: The present invention relates to a noncontacting power transfer device which can supply power from a power source body to an appliance body through electromagnetic induction therebetween in a small-sized electric appliance such as a charging device and electric tooth brush, in which the power source body for supplying power and the appliance body having load are designed so as to be removal from each other. An example of previously known noncontacting power transfer devices is disclosed in Japanese Patent Publication No. Hei. 6-311658. In such a device, a signal to be detected when an appliance is mounted on a power supply body is created by the signal produced from a primary coil in a state where the output from a primary side oscillation circuit is sufficiently suppressed. In the above conventional noncontacting power transfer device, the intermittent time of oscillation by an intermittent driving/oscillation means is set using a timer. But such time setting by the timer requires the means of a timer IC so that cost of components becomes expensive correspondingly. Further, since an oscillation period is always set constant irrespectively of a change in the input voltage, the level of a signal detected for an appliance body is not stable. Specifically, where only a low voltage is input owing to circumstances of power, the detected signal level is low, whereas a high input voltage leads to a high level of detected signal. Document US 4 761 724 discloses a transformer coupling for transmitting direct current through a barrier, wherein direct current from an energy source on one side of an electrical and mechanical barrier is transmitted to a load on the other side of the barrier by utilizing a transformer. The primary and secondary windings are arranged on respective cores of the transformer which are magnetically coupled. For effecting the magnetic coupling, the direct current input is fed through a self-excited oscillator circuit, connected to the winding of the primary transformer core so as to create a time varying magnetic field, which magnetic field is passed through the barrier to a winding on the secondary transformer core with the winding being tuned to the frequency of the field. The secondary side comprises a rectifying diode and a smoothing capacitor so that the output from the secondary winding is rectified, filtered and used to supply the output load. Furthermore, the voltage is subject to a specific voltage regulation. Accordingly, it is the object of the present invention to solve the above problem and to provide a stable intermittent driving/oscillation means economically. This object is accomplished according to the present invention by a noncontacting power transfer device for supplying power from a power supply body to an appliance body as claimed in appended claim 1. According to the present invention, in a noncontacting power transfer device a primary winding T 1 is intermittently oscillation-driven as an oscillation winding and a driving signal thus created is used as a signal for detecting the appliance body B, and a response signal receiving circuit X of a power supply body A receives a response signal from a response signal circuit Y of an appliance body B to detect the appliance body. An intermittently driving means M in said power supply body includes a secondary winding T2 wound on the same core as the primary winding T 1 and a diode D 1 and capacitor C 2 for rectifying/smoothing the voltage induced in the secondary winding as an induction winding, and a control transistor Q 2 operated by an output voltage from the intermittent driving means M is connected to the control end of an oscillation transistor Q 1 so that the oscillation transistor Q 1 is intermittently driven by the intermittent voltage. An explanation will be given of the operation of the noncontacting power transfer device according to the present invention. The output from a secondary winding T 2 induced by a primary winding T 1 is smoothed by a capacitor C 2 after its rectifying. When an output voltage V 1 reaches a predetermined voltage, a control transistor Q 2 turns on to stop oscillation. Then, since the voltage induced in the secondary winding T 2 disappears, the output voltage V 1 gradually decreases to turn off the control transistor Q 2 . When the control transistor Q 2 turns off, the capacitor C 1 stores charges through a resistor R 1 . Then, the base voltage V G of an oscillation transistor Q 1 increases so that it operates again to start oscillation. Such an operation is repeated successively to provide an intermittent driving state. Next, when an appliance body B is applied to a power source body A, energy by the above intermittent driving induces a voltage in the appliance body B. Thus, a response signal circuit Y for the appliance body B outputs a response signal. When the output from the response signal circuit Y is supplied to a response signal receiving circuit X of the power source body A, the transistor Q 3 turns on and the control transistor Q 2 turns off, thus resulting in continuous oscillation. Incidentally, a resistor R 3 serves to suppress the storage of charges into the capacitor C 2 to retard the increase in the output voltage V 1 , thereby controlling the oscillation period of the intermittent driving. Where the input voltage is low, the voltage induced in the secondary winding T 2 is low so that the output V 1 rises slowly. As a result, the oscillation period of the intermittent driving becomes long. Where the input voltage is high, the oscillation period of the intermittent driving becomes short, certain energy is sent out as a detection signal. In the accompanying drawings: Fig. 1 is an electric circuit diagram of the noncontacting power transfer device according to the present invention; and Figs. 2(A) to 2(C) are operation waveform charts according to the present invention, Fig. 2(A) shows the oscillation voltage V C of the oscillating winding T 1 , Fig. 2(B) shows output voltage V 1 , and Fig. 2(C) shows the base voltage V G of the oscillation transistor Q 1 for elapse of time, respectively. Now referring to the drawings, an explanation will be given of a concrete embodiment of the noncontacting power transfer device. Fig. 1 is an electric circuit diagram of the noncontacting power transfer device according to the present invention. In Fig. 1, symbol A denotes a power source body; B an appliance body; T 1 a primary winding (hereinafter referred to as "oscillation winding"; T 2 a secondary winding (hereinafter referred to as "induction winding") wound on the same core (not shown) as the primary winding; C 1 , C 2 capacitors; D 1 a diode; Q 1 an oscillation transistor; Q 2 a control transistor; Q 3 a transistor connected to the base of the control transistor Q 2 ; R 1 , R 2 , R 3 resistors; V G a base voltage of the oscillation transistor Q 1 ; X a response signal receiving circuit; and Y a response signal circuit. An explanation will be given of the operation of the noncontacting power transfer device according to the present invention. In the electric circuit diagram shown in Fig. 1, the basic oscillation operation, which is the same as in the prior art, will not be explained. For intermittent driving, the induction winding T 2 is wound on the same core (not shown) as the oscillation winding T 1 . The output from a secondary winding T 2 is rectified by the diode D 1 and smoothed by the capacitor C 2 . When the output voltage V 1 reaches a predetermined voltage, the control transistor Q 2 turns on to stop oscillation. Then, since the voltage induced in the secondary winding T 2 disappears, the output voltage V 1 gradually decreases to turn off the control transistor Q 2 . When the control transistor Q 2 turns off, the capacitor C 1 stores charges through the resistor R 1 . Then, the base voltage V G of an oscillation transistor Q 1 increases so that it operates again to start oscillation. Such an operation is repeated successively to provide an intermittent driving state. Next, when the appliance body B is applied to the power source body A, energy by the above intermittent driving induces a voltage in the appliance body B. Thus, the response signal circuit Y for the appliance body B outputs a response signal. When the output from the response signal circuit Y is supplied to a response signal receiving circuit X of the power source body, the transistor Q 3 turns on and the control transistor Q 2 turns off, thus resulting in continuous oscillation. Incidentally, the resistor R 3 serves to suppress the storage of charges into the capacitor C 2 to retard the increase in the output voltage V 1 , thereby controlling the oscillation period of the intermittent driving. Where the input voltage is low, the voltage induced in the secondary winding T 2 is low so that the output V 1 rises slowly. As a result, the oscillation period of the intermittent driving becomes long. Where the input voltage is high, the oscillation period of the intermittent driving becomes short, certain energy is sent out as a detection signal. Figs. 2(A) to 2(C) are operation waveform charts according to the present invention. Fig. 2(A) shows the oscillation voltage V C of the oscillating winding T 1 , Fig. 2(B) shows output voltage V 1 , and Fig. 2(C) shows the base voltage V G of the oscillation transistor Q 1 for elapse of time, respectively. As described above, in the noncontacting power transfer device according to the present invention, the oscillation winding T 1 is intermittently oscillation-driven and the resultant driving signal is used as a signal for detecting the appliance body B. The power supply body A receives the response signal from the appliance body B to detect the appliance body B. The intermittent driving means M includes the induction winding T 2 wound on the same core as the oscillation winding T 1 and the diode D 1 and capacitor C 2 for rectifying/smoothing the voltage induced in the induction winding T 2 . The control transistor Q 2 operated by the output voltage V 1 of the intermittent driving means M is connected to the control end of the oscillation transistor Q 1 so that the oscillation transistor Q 1 is intermittently driven by the oscillation voltage V C . In this way, a stabilized intermittent driving of the transistor can be executed. The noncontacting power transfer device according to the present invention, although it has a very simple circuit configuration, permits a stabilized driving operation and can effectively send certain energy as a detection signal according to an input voltage. A primary winding T 1 as anoscillation winding T 1 is intermittently oscillation-driven and the resultant driving signal is used as a signal for detecting an appliance body B. A power supply body A receives the response signal from the appliance body B to detect the appliance body B. An intermittent driving means M includes the induction winding T 2 wound on the same core as the oscillation winding T 1 and a diode D 1 and capacitor C 2 for rectifying/smoothing the voltage induced in the induction winding T 2 . A control transistor Q 2 operated by the output voltage V 1 of the intermittent driving means M is connected to the control end of an oscillation transistor Q 1 so that the oscillation transistor Q 1 is intermittently driven by an oscillation voltage V C .

Claims: A noncontacting power transfer device for supplying power from a power supply body (A) to an appliance body (B) having a response signal circuit, comprising: a primary winding (T 1 ) as an oscillation winding, said primary winding (T 1 ) having a core and being accomodated in the power supply body (A); an oscillation transistor (Q 1 ) for oscillation-driving said primary winding (T 1 ); and intermittently driving means (M) provided in said power supply body (A) for intermittently oscillation-driving said primary winding (T 1 ) so as to create a signal for detecting the appliance body (B), wherein said power supply body (A) receives a response signal which is output from the response signal circuit when the appliance body (B) receives the signal for detecting the appliance body (B); wherein said intermittently driving means (M) is characterized by: a secondary winding (T 2 ) wound on the same core as said primary winding (T 1 ); a diode (D 1 ) for rectifying voltage induced by said secondary winding (T 2 ); a capacitor (C 2 ) for smoothing the voltage induced by said secondary winding (T 2 ); and a control transistor (Q 2 ) operated by the voltage rectified and smoothed by said diode (D 1 ) and capacitor (C 2 ) so as to create an intermittent voltage, wherein said control transistor (Q 2 ) is connected to a control end of said oscillation transistor (Q 1 ) so that said oscillation transistor (Q 1 ) is intermittently driven by the intermittent voltage of said control transistor (Q 2 ).

Inventors: KATSURA YOSHINORI, TAMURA HIDEKI, YAMASHITA MIKIHIRO, KATSURA, YOSHINORI, TAMURA, HIDEKI, YAMASHITA, MIKIHIRO
Applicants: MATSUSHITA ELECTRIC WORKS LTD, MATSUSHITA ELECTRIC WORKS, LTD.
Application year: 1997
Main classification: H01F38
IPC codes: H02J17, H01F38, H02J5, H02J7