JP5571012B2 - Non-contact power transmission device - Google Patents

Description

  The present invention relates to a contactless power transmission apparatus that transmits power in a contactless manner.

  In recent years, a method for transmitting power in a contactless manner to an electronic device such as a mobile phone, a digital camera, or a laptop computer has become widespread. Electric power is transmitted to the power receiving coil built in the electronic device by an alternating magnetic field generated from the power transmitting coil built in the power transmitting device. The power supplied to the power receiving coil is supplied to a load such as a secondary battery via a rectifying and smoothing circuit. Since the load varies depending on the amount of power used by the electronic device, it is necessary to stabilize the output voltage by controlling the power transmitted from the power transmission coil to the power reception coil.

  Patent Document 1 describes a non-contact power transmission device including a power supply control circuit that controls a voltage supplied to a power transmission coil. FIG. 3 is a diagram illustrating a circuit diagram of a conventional non-contact power transmission apparatus. An AC-DC converter 50 to which an AC voltage AC is supplied from a power source such as a commercial power source, a power transmission device 60, and a power reception device 70 are provided.

  The power transmission device 60 includes a drive circuit 61, a power transmission coil 62, a voltage variable circuit 63, a communication unit 64, and a control circuit 65. The power receiving device 70 includes a power receiving coil 71, a rectifying / smoothing circuit 72, a detection circuit 73, and a communication unit 74.

  The AC-DC converter 50 converts AC power into DC power and supplies it to the voltage variable circuit 63. The voltage variable circuit 63 converts the voltage of the supplied DC power and supplies the converted voltage to the drive circuit 61. The drive circuit 61 converts the supplied voltage into AC power and supplies it to the power transmission coil 62. The power receiving coil 71 receives power from the power transmitting coil 62 by electromagnetic induction. The AC power induced in the power receiving coil 71 is rectified by the rectifying / smoothing circuit 32 to obtain the output voltage Vo. The detection circuit 73 compares the output voltage Vo with a reference voltage and transmits a detection signal to the control circuit 65 via the communication means 74 and 64. As an example, the communication unit 74 includes a light emitting diode, and the communication unit 64 includes a phototransistor. The control circuit 65 variably controls the DC power supplied from the voltage variable circuit 63 to the power transmission coil 62 so that the output voltage Vo is stabilized at a predetermined value based on the detection signal. In this way, the output voltage Vo is controlled.

JP 2009-65749 A

  However, in such a non-contact power transmission device, in addition to the loss of the AC-DC converter 50, the loss of the voltage variable circuit 63 occurs, and thus there is a problem that the efficiency is deteriorated. As a method of controlling the output voltage Vo, there is also a method of changing the oscillation frequency of AC power supplied to the power transmission coil 62. However, in order to stabilize the output voltage Vo, it is necessary to change the oscillation frequency significantly, so that the oscillation frequency falls within the frequency range of the noise terminal voltage standard, and it is necessary to enlarge the noise filter. In addition, there is a problem that the oscillation frequency deviates from the optimum condition and the power transmission efficiency is lowered.

  The present invention has been made in consideration of such a problem, and an object of the present invention is to provide a non-contact power transmission apparatus in which loss is reduced and efficiency is improved when an AC-DC converter is used.

  In order to achieve such an object, the present invention converts an AC voltage into a DC voltage and outputs it, a drive circuit to which the output of the AC-DC converter is supplied, a predetermined frequency from the drive circuit A power transmission coil to which AC power of the power transmission coil is supplied, a power reception coil to which power is transmitted from the power transmission coil in a non-contact manner using electromagnetic induction, and a detection circuit that detects an output voltage of the power reception coil. Control is performed so that the output of the AC-DC converter becomes constant based on a detection signal.

  According to the present invention, when an AC-DC converter is used, loss in the power transmission circuit can be reduced and efficiency can be improved.

1 is a circuit diagram of a non-contact power transmission apparatus according to a first embodiment of the present invention. The circuit diagram of the non-contact electric power transmission apparatus which concerns on 2nd Example of this invention. Circuit diagram of a conventional non-contact power transmission device

  FIG. 1 shows a circuit diagram of a non-contact power transmission apparatus according to a first embodiment of the present invention. An AC-DC converter 10 to which an AC voltage AC is supplied from a power source such as a commercial power source, a power transmission device 20 and a power reception device 30 are provided. The AC-DC converter 10 and the power transmission device 20 are each provided with a positive terminal V, a GND terminal G, and a signal terminal S, and the terminals are connected to each other by a cable.

  The AC-DC converter 10 includes a rectifying / smoothing circuit 11, a switch circuit 12, a transformer 13 having a primary winding and a secondary winding, a rectifying circuit 14, a detection unit 15, and a switch control circuit 16. The power transmission device 20 includes a drive circuit 21, a power transmission coil 22, a phototransistor 23, and a PNP type digital transistor 24. The power receiving device 30 includes a power receiving coil 31, a rectifying / smoothing circuit 32, a detection circuit 33, and a light emitting diode 34.

  The rectifying / smoothing circuit 11 rectifies and smoothes the AC voltage AC supplied from a power source such as a commercial power source. The switch circuit 12 converts the DC voltage supplied from the rectifying / smoothing circuit 11 into an AC voltage and supplies the AC voltage to the primary winding of the transformer 13. The voltage induced in the secondary winding of the transformer 13 is rectified by the rectifier circuit 14 to obtain a DC voltage Vi. The DC voltage Vi is supplied to the drive circuit 21 via each positive terminal V. The drive circuit 21 converts the DC voltage Vi into an AC voltage having a predetermined frequency and supplies the obtained AC voltage to the power transmission coil 22. The power receiving coil 31 receives power from the power transmitting coil 22 by electromagnetic induction. The AC power induced in the power receiving coil 31 is rectified and smoothed by the rectifying and smoothing circuit 32 to obtain the output voltage Vo. The output voltage Vo is supplied to a load (not shown) such as a secondary battery.

  The detection circuit 33 transmits a detection signal obtained by comparing the output voltage Vo and the reference voltage to the phototransistor 23 via the light emitting diode 34. The collector terminal of the phototransistor 23 is connected to the base terminal of the digital transistor 24, and the emitter terminal of the phototransistor 23 is connected to the collector terminal of the digital transistor 24. The emitter terminal of the digital transistor 24 is connected to the signal terminal S of the power transmission device 20, and the collector terminal of the digital transistor 24 is connected to the GND terminal G of the power transmission device 20.

  The configuration of the detection means 15 of the AC-DC converter 10 will be described. The detection means 15 includes a photocoupler including a light emitting diode LED and a phototransistor PT, a shunt regulator SR, and voltage dividing resistors R1, R2, and R3. The voltage dividing resistors R1, R2, and R3 are connected in series between the positive terminal V and the GND terminal G of the AC-DC converter 10. The anode terminal of the light emitting diode LED is connected to the positive terminal V of the AC-DC converter 10 via a resistor. The cathode terminal of the light emitting diode LED is connected to the cathode terminal of the shunt regulator SR. The anode terminal of the shunt regulator SR is connected to the GND terminal G of the AC-DC converter 10. The reference terminal of the shunt regulator SR is connected between the voltage dividing resistors R1 and R2. The signal terminal S of the AC-DC converter 10 is connected between the voltage dividing resistors R2 and R3. That is, both ends of the voltage dividing resistor R3 are connected to the main current path of the digital transistor 24 via each positive terminal V and each GND terminal G. The phototransistor PT is connected to the switch control circuit 16. The switch control circuit 16 controls the switch circuit 12 based on a signal supplied to the phototransistor PT.

  Next, the control operation of the output voltage Vo will be described. The detection circuit 33 compares and detects the output voltage Vo and the reference voltage. When the output voltage Vo becomes lower than a predetermined reference voltage, a signal is transmitted from the light emitting diode 34 to the phototransistor 23, and the digital transistor 24 is turned on. Then, since both ends of the voltage dividing resistor R3 are short-circuited, the voltage supplied to the reference terminal of the shunt regulator SR is lowered. This is detected by a photocoupler including a light emitting diode LED and a phototransistor PT, and the switch control circuit 16 controls the switch circuit 12 so that the DC voltage Vi that is the output of the AC-DC converter 10 increases. If the DC voltage Vi increases, the power transmitted from the power transmission coil 22 to the power reception coil 31 increases, so the output voltage Vo also increases.

  On the other hand, when the output voltage Vo becomes higher than a predetermined reference voltage, no signal is transmitted from the light emitting diode 34 to the phototransistor 23, and the digital transistor 24 is turned off. Then, since both ends of the voltage dividing resistor R3 are opened, the voltage supplied to the reference terminal of the shunt regulator SR is increased. This is detected by a photocoupler including a light emitting diode LED and a phototransistor PT, and the switch control circuit 16 controls the switch circuit 12 so that the DC voltage Vi that is the output of the AC-DC converter 10 decreases. If the DC voltage Vi decreases, the power transmitted from the power transmission coil 22 to the power reception coil 31 decreases, and the output voltage Vo also decreases. Even when the load fluctuates and the output voltage Vo of the power transmission device 30 fluctuates, such an operation is repeated to control the output voltage Vo to be stable.

  Thus, by directly controlling the output of the AC-DC converter 10 according to the change in the output voltage Vo, the voltage variable circuit in the power transmission device 20 can be omitted, and the power transmission device 20 can be reduced in size. . In addition, since the loss in the voltage variable circuit that has conventionally occurred can be eliminated, the efficiency of the entire circuit can be improved. In addition, the output voltage Vo can be controlled without significantly changing the oscillation frequency of the AC voltage supplied to the power transmission coil 22. Therefore, the fundamental frequency can be set to 150 kHz or less which is the lower limit value of the frequency range of the noise terminal voltage standard, and the increase in size of the noise filter can be suppressed. Further, since the third harmonic does not enter the AM radio frequency band, it is advantageous in terms of noise. Further, the oscillation frequency is not deviated from the optimum condition.

  Depending on the detection signal supplied from the detection circuit 33, a part of the voltage dividing resistor that detects the DC voltage Vi that is the output of the AC-DC converter 10 is changed. In accordance with this resistance change, the switch circuit 12 is controlled to change the DC voltage Vi that is the output of the AC-DC converter 10. The detection means 15 is provided with a photocoupler including a light emitting diode LED and a phototransistor PT, and the primary winding and the secondary winding of the transformer 13 are insulated from each other. Therefore, the detection signal is a control signal for the secondary circuit of the AC-DC converter 10 and is not restricted in terms of safety standards. Further, since only a part of the voltage dividing resistors R1 to R3 is changed, the circuit configuration is simple and additional components are reduced.

  Next, FIG. 2 shows a circuit diagram of a non-contact power transmission apparatus according to a second embodiment of the present invention. In addition, the same code | symbol is attached | subjected to the site | part which has the same function as a 1st Example, and description is abbreviate | omitted. The power transmission device 20 includes a drive circuit 21, a power transmission coil 22, a demodulation circuit 26, a microcomputer 27, and a control circuit 28. The power receiving device 30 includes a power receiving coil 31, a rectifying / smoothing circuit 32, a detection circuit 33, a microcomputer 36, and a modulation circuit 37.

  The detection circuit 33 transmits a detection signal obtained by comparing the output voltage Vo and the reference voltage to the microcomputer 36. The microcomputer 36 controls the modulation circuit 37 based on the detection signal. The modulation circuit 37 modulates the detection signal and superimposes it on the power receiving coil 31. The modulation signal superimposed on the power receiving coil 31 appears as a voltage change of the power transmitting coil 22. This voltage change is demodulated by a demodulation circuit 26 connected to one of the power transmission coils 22 to obtain a detection signal. The demodulated detection signal is transmitted to the microcomputer 27. The microcomputer 27 supplies the detection signal to the detection means 15 via the control circuit 28 and the signal terminal S.

  Next, when the output voltage Vo becomes lower than a predetermined reference voltage, the control circuit 28 shorts both ends of the voltage dividing resistor R3. Then, the voltage supplied to the reference terminal of the shunt regulator SR becomes low, and this is detected by a photocoupler composed of the light emitting diode LED and the phototransistor PT. The switch control circuit 16 controls the switch circuit 12 so that the DC voltage Vi that is the output of the AC-DC converter 10 increases.

  On the other hand, when the output voltage Vo becomes higher than a predetermined reference voltage, the control circuit 28 opens both ends of the voltage dividing resistor R3. Then, the voltage supplied to the reference terminal of the shunt regulator SR is increased, and this is detected by a photocoupler including a light emitting diode LED and a phototransistor PT. Then, the switch control circuit 16 controls the switch circuit 12 so that the DC voltage Vi that is the output of the AC-DC converter 10 decreases. Similar to the first embodiment, even when the output voltage Vo fluctuates, such an operation is repeated to control the output voltage Vo to be stable.

  In order to control the output voltage Vo, it is necessary to transmit a detection signal obtained by comparing the output voltage Vo and the reference voltage from the power receiving device 30 to the power transmitting device 20. In the first embodiment, the detection signal is transmitted and received using the light emitting diode 34 and the phototransistor 23, and in the second embodiment, the microcomputers 27 and 36, the modulation circuit 37, and the demodulation circuit 26 are used. The method for transmitting and receiving the detection signal is not limited to these, and any method may be used as long as it can be transmitted and received without contact.

  A detection signal supplied from the detection circuit 33 that detects the output voltage Vo is supplied to the AC-DC converter 10 via the power transmission device 20. Thereby, there is no need to directly exchange signals between the AC-DC converter 10 and the power receiving device 30. Further, the AC-DC converter 10 and the power transmission device 20 are provided with a positive terminal V and a GND terminal G for supplying a DC voltage Vi, and a signal terminal S for transmitting and receiving a detection signal. It is not necessary to prepare a plurality of cables between the terminals by configuring the terminals to be detachable with connectors and connecting the terminals together with a single cable.

DESCRIPTION OF SYMBOLS 10 AC-DC converter 11 Rectification smoothing circuit 12 Switch circuit 13 Transformer 14 Rectification circuit 15 Detection means 16 Switch control circuit 20 Power transmission apparatus 21 Drive circuit 22 Power transmission coil 23 Phototransistor 24 PNP type digital transistor 26 Demodulation circuit 27 Microcomputer 28 Control circuit 30 Power receiving device 31 Power receiving coil 32 Rectification smoothing circuit 33 Detection circuit 34 Light emitting diode 36 Microcomputer 37 Modulation circuit

Claims (3)

An AC-DC converter that converts an AC voltage into a DC voltage and outputs the DC voltage;
A power transmission device including a drive circuit to which an output of the AC-DC converter is supplied and a power transmission coil to which AC power of a predetermined frequency is supplied from the drive circuit;
Consists of a power receiving device and a detection circuit for detecting an output voltage obtained by the voltage derived from the sending coil to the receiving coil and the power receiving coil are power transmission in a non-contact manner using electromagnetic induction is rectified,
The AC-DC converter,
A rectifying and smoothing circuit to which the AC voltage is supplied,
A transformer having a primary winding and a secondary winding;
A switch circuit connected in series with the primary winding to the output of the rectifier circuit;
Detecting means for detecting the DC voltage obtained by rectifying the output of the secondary winding,
And a switch control circuit for driving the switching circuit based on a signal supplied from said detecting means,
Detection means,
A plurality of voltage detection resistors for dividing the DC voltage,
Based on the detection signal of the detection circuit ,
Output voltage controls the DC voltage to be stable,
The detection signal, by varying the part of the voltage detection resistor,
Based on the voltage divided by the voltage detection resistor,
A non-contact power transmission device that controls the switch circuit so that the DC voltage is variable . The detection signal is
Non-contact power transmission apparatus of claim 1 wherein the drive circuit and said power transmission coil is supplied to the AC-DC converter via the power transmission device provided. The non-contact power transmission apparatus according to claim 2 , wherein the AC-DC converter and the power transmission apparatus are detachable via a connector.

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