JP6915264B2 - Power supply device and wireless power transmission device using this - Google Patents

Description

The present invention relates to a power supply device that wirelessly transmits electric power to a power receiving device equipped with a power receiving coil, and a wireless power transmission device using the same.

Wireless power transmission technology, which transmits power without using a power cord or power cable, is attracting attention. Since wireless power transmission technology can wirelessly supply power from the power supply side to the power reception side, it can be applied to various products such as transportation equipment such as trains and electric vehicles, home appliances, electronic equipment, wireless communication equipment, toys, and industrial equipment. Is expected.

As a method of wireless power transmission, there is a method in which a current is passed through a power feeding coil to generate a magnetic flux, and the magnetic flux interlinks with the power receiving coil to generate a voltage in the power receiving coil to transmit power. In the case of such a method, the electromagnetic field generated around the power feeding coil and the power receiving coil may cause electromagnetic noise to other electric devices, which may cause a malfunction of the electric devices. Against this background, in wireless power transmission technology, how to reduce electromagnetic noise has become an issue.

For example, Patent Document 1 uses a frequency variable means for dispersing the frequency of generated noise by varying the frequency of the voltage output by the inverter circuit to the induction coil (feeding coil) discretely or continuously. Noise countermeasures have been proposed.

Further, in Patent Document 2, a plurality of drive frequencies of an inverter that outputs AC power to a power transmission coil (feeding coil) are set, and the frequency at the time of driving the inverter is repeatedly changed by a plurality of drive frequencies that are discrete frequencies. Therefore, it has been proposed to reduce the leakage magnetic field.

Japanese Unexamined Patent Publication No. 2006-278602 International Publication No. 2016/006066 Pamphlet

However, in the technique disclosed in Patent Document 1, in order to reduce noise, the frequency of the voltage output to the induction coil (feeding coil) is varied discretely or continuously on the power receiving side. There was a problem that the power that could be received changed.

On the other hand, in the technique disclosed in Patent Document 2, since the discrete frequencies when the output current matches the current value corresponding to the required power are changed as a plurality of drive frequencies, the drive frequencies that can be set are limited. Therefore, the dispersion of the noise is also limited, and the problem that the noise cannot be reduced as desired still remains.

The present invention has been made in view of the above problems, and an object of the present invention is to suppress fluctuations in received power while reducing electromagnetic noise.

In order to solve the above problems, the power supply device according to the present invention is a power supply device that wirelessly transmits power to a power receiving device equipped with a power receiving coil, and has a power supply unit that outputs a DC voltage and converts the DC voltage into an AC voltage. Invert, a power supply coil that receives the AC voltage to generate magnetic flux, a frequency variable unit that repeatedly changes the frequency of the AC voltage during power transmission, and a DC voltage output level that is repeatedly changed during power transmission. The voltage variable unit includes a voltage variable unit, and the voltage variable unit uses the DC voltage as the received power so as to suppress fluctuations in the received power on the power receiving device side caused by a frequency change of the AC voltage by the frequency variable unit. It is characterized in that it is changed in a complementary manner to.

According to the present invention, by repeatedly changing the drive frequency (power transmission frequency) of the power feeding coil during power transmission, the frequency of the noise of the magnetic field component or the electric field component generated from the power feeding device is dispersed, and thus the average of the noise. The value and quasi-peak value can be reduced. Therefore, the influence of electromagnetic noise on other devices can be reduced as compared with the case where the drive frequency of the feeding coil is set to a single frequency. Further, by changing the DC voltage supplied from the power supply unit to the inverter during power transmission in a complementary manner with respect to the received power, it is possible to suppress fluctuations in the received power due to a change in the drive frequency of the power feeding coil. Therefore, it is possible to suppress fluctuations in the received power while reducing electromagnetic noise. In addition, according to the present invention, since electromagnetic noise is reduced by a relatively simple method of changing the drive frequency of the feeding coil, the number of parts required for noise countermeasures can be significantly reduced. It is also possible to reduce the size and cost.

In the present invention, the voltage variable unit raises the DC voltage when the frequency of the AC voltage changes in the direction of decreasing the received power, and changes the frequency of the AC voltage in the direction of increasing the received power. Sometimes it is preferable to lower the DC voltage. When wireless power transmission is realized by using a resonance circuit consisting of a pair of coil feeding coil and power receiving coil, if the driving frequency of the feeding coil, that is, the frequency (output frequency) of the AC voltage output from the inverter is changed, Since the amount of power that can be sent from the power supply side to the power reception side changes, it is not possible to stably supply power. However, since the DC voltage output from the power supply unit is controlled so as to suppress the fluctuation of the received power generated by changing the output frequency of the inverter, it is possible to suppress the fluctuation of the received power while reducing the electromagnetic noise.

In the present invention, it is preferable that the voltage variable unit changes the DC voltage based on the frequency of the drive signal output from the frequency variable unit to the inverter in order to control the frequency of the AC voltage. The change in the received power is caused by the change in the drive frequency of the power feeding coil, and since there is a certain correlation between the received power level and the output frequency of the inverter, the drive signal for controlling the output frequency of the inverter By changing the DC voltage based on the frequency, it is possible to suppress the change of the received power without directly monitoring the change.

In the present invention, it is preferable that the voltage variable unit changes the DC voltage based on a conversion formula or a conversion table representing the change in the received power due to the change in the frequency of the AC voltage. According to this, the DC voltage level can be controlled without directly monitoring the change in the received power.

In the present invention, it is preferable that the voltage variable unit changes the DC voltage based on the received power information provided from the power receiving device side. According to this, even if the positional relationship between the power feeding coil and the power receiving coil changes, the fluctuation of the received power can be reliably detected and suppressed.

In the present invention, it is preferable that the frequency variable unit changes the frequency of the AC voltage within a range in which the current phase of the inverter is slower than the voltage phase. When the current phase of the inverter is phase-advancing with respect to the voltage phase, a through current may flow through the switching element of the inverter, which may increase noise or damage the switching element. However, it is possible to avoid the generation of noise and the damage of the switching element by operating the inverter when the current phase is slower than the voltage phase. Therefore, when the phase of the output current of the inverter is slower than the phase of the output voltage, it is possible to suppress the damage of the circuit element due to the through current flowing through the circuit element of the inverter.

In the present invention, it is preferable that the frequency variable unit continuously changes the frequency of the AC voltage during power transmission. In this case, the number of frequency points to be dispersed increases, the average value and the quasi-peak value of the noise are further lowered, and the influence of the noise on other devices can be further reduced. Further, by continuously changing the drive frequency, the stress applied to the circuit element can be reduced.

In the present invention, it is preferable that the frequency variable unit discretely changes the frequency of the AC voltage during power transmission. In this case, the drive frequency can be changed by digital control, and the frequency variable unit can be easily configured. For example, the frequency variable unit can be configured at low cost by setting the frequency to be changed discretely using software.

In the present invention, the power supply unit preferably includes a non-isolated DCDC converter. According to this configuration, the power supply unit can be constructed at low cost.

Further, the power supply device according to the present invention is a power supply device that wirelessly transmits power to a power receiving device equipped with a power receiving coil, and includes a power supply unit that outputs a DC voltage, an inverter that converts the DC voltage into an AC voltage, and the above. A power feeding coil that receives an AC voltage to generate a magnetic flux, a frequency variable unit that repeatedly changes the frequency of the AC voltage during power transmission, and a voltage variable unit that repeatedly changes the output level of the DC voltage during power transmission. The voltage variable unit increases the DC voltage when the frequency variable unit changes the frequency of the AC voltage in a direction of decreasing the received power, and the frequency variable unit increases the received power. It is characterized in that the DC voltage is lowered when the frequency of the AC voltage is changed.

According to the present invention, it is possible to reduce the influence of electromagnetic noise on other devices as compared with the case where the drive frequency of the feeding coil is set to a single frequency. Moreover, since the DC voltage output from the power supply unit is controlled so as to suppress the fluctuation of the received power generated by changing the output frequency of the inverter, the received power due to the change of the drive frequency of the power feeding coil is reduced while reducing the electromagnetic noise. Fluctuations can be suppressed.

Further, the wireless power transmission device according to the present invention includes a power supply device according to the present invention having the above characteristics, a power receiving device equipped with a power receiving coil that receives at least a part of the magnetic flux generated by the power feeding coil and generates an AC voltage. It is characterized by having.

According to the present invention, by repeatedly changing the power transmission frequency during power transmission, the frequency of electromagnetic noise generated from the power feeding device can be dispersed, and the power feeding coil is electromagnetic as compared with the case where the power feeding coil is driven by a single frequency. The influence of noise on other devices can be reduced. Further, by changing the DC voltage supplied from the power supply unit to the inverter during power transmission in a complementary manner with respect to the received power, it is possible to suppress fluctuations in the received power due to a change in the drive frequency of the power feeding coil. Therefore, it is possible to suppress fluctuations in the received power while reducing electromagnetic noise. In addition, electromagnetic noise can be reduced by a relatively simple method, and miniaturization and cost reduction can be achieved.

In the present invention, it is preferable that each of the power receiving device and the power feeding device includes a communication unit that performs data communication with each other, and the power receiving device provides power received power information to the power feeding device via the communication unit. According to this, since the relative position of the power receiving coil with respect to the power feeding coil changes, even when it is difficult to use the conversion formula or the conversion table, the fluctuation of the received power can be surely suppressed.

According to the present invention, it is possible to provide a wireless power receiving device and a wireless power transmission system capable of suppressing fluctuations in received power while reducing electromagnetic noise.

FIG. 1 is a block diagram showing a configuration of a wireless power transmission device according to the first embodiment of the present invention. FIG. 2 is a graph showing an example of time change of the frequency signal output from the frequency signal generation circuit 41. FIG. 3 is a graph showing the frequency characteristics of the EMI of the power feeding device 2 when the frequency signal of FIG. 2 is given. FIG. 4 is a diagram for explaining the relationship between the output voltage of the power supply unit 10 and the received power. FIG. 4A shows the frequency characteristics of the output voltage of the power supply unit 10 and FIG. 4B shows the frequency characteristics of the received power. Each is shown. 5A and 5B are diagrams for explaining the relationship between the output voltage of the power supply unit 10 and the received power. FIG. 5A shows the frequency characteristics of the output voltage of the power supply unit 10 and FIG. 5B shows the frequency characteristics of the received power. Each is shown. FIG. 6 is a graph showing the time change of the output voltage of the power supply unit 10 controlled by the voltage variable unit 50, in which (a) is the frequency of the drive signal and (b) is the power supply unit corresponding to the frequency of the drive signal. The output voltages of 10 are shown respectively. FIG. 7 is a graph showing another example of the time change of the frequency signal output from the frequency signal generation circuit 41. FIG. 8 is a graph showing the frequency characteristics of the EMI of the power feeding device 2 when the frequency signal of FIG. 7 is given. FIG. 9 is a block diagram showing in detail the configuration of the wireless power transmission device 1A on the power supply device 2 side. FIG. 10 is a circuit diagram showing in detail an example of the configuration of the power feeding device 2 in FIG. FIG. 11 is a diagram for explaining another example of the frequency signal control method in the power feeding device 2. FIG. 12 is a block diagram showing a configuration of a wireless power transmission device according to a second embodiment of the present invention. FIG. 13 is a block diagram showing a configuration of a conventional wireless power transmission device that does not change the output voltage level of the power supply unit 10.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a block diagram showing a configuration of a wireless power transmission device according to the first embodiment of the present invention.

As shown in FIG. 1, the wireless power transmission device 1A comprises a combination of the power supply device 2 and the power receiving device 3, and wirelessly transmits power from the power supply device 2 to the power receiving device 3.

The power supply device 2 converts the AC voltage supplied from the AC power supply 4 into a power supply unit 10 that converts the AC voltage into a predetermined DC voltage, and the power supply unit 10 that converts the predetermined DC voltage output by the power supply unit 10 into an AC voltage (rectangular wave) of, for example, 100 kHz. The inverter 20, the power feeding coil 30 that receives the AC voltage and generates the magnetic flux, the frequency variable unit 40 that outputs the drive signal (AC voltage) for controlling the change in the frequency of the AC voltage output by the inverter 20, and the frequency. The voltage variable unit 50 that controls the DC voltage output by the power supply unit 10 based on the frequency of the drive signal from the variable unit 40, and the drive circuit 60 that drives the inverter 20 based on the drive signal from the frequency variable unit 40. I have. The frequency variable unit 40 includes a frequency signal generation circuit 41 that generates a predetermined frequency signal, and an oscillation circuit 42 that oscillates according to a frequency signal supplied from the frequency signal generation circuit 41.

The power receiving device 3 includes a power receiving coil 70 that receives at least a part of the magnetic flux generated by the power feeding coil 30 to generate an AC voltage, and an output circuit unit 80 that converts the AC voltage generated from the power receiving coil 70 into a DC voltage of, for example, 24V. And have. The output voltage of the output circuit unit 80 is supplied to the load 90.

The power feeding coil 30 constitutes a resonance circuit together with a capacitor 31 provided in series with the power feeding coil 30 in the power feeding device 2. Similarly, the power receiving coil 70 constitutes a resonance circuit together with a capacitor 71 provided in series with the power receiving coil 70 in the power receiving device 3. The configuration of the feeding side resonance circuit including the feeding coil 30 is not particularly limited, and capacitors may be provided in parallel to the feeding coil 30 or may be provided in series and parallel. Similarly, the configuration of the power receiving side resonance circuit including the power receiving coil 70 is not particularly limited, and the power receiving coil 70 may be provided with a capacitor in parallel or may be provided in series and parallel. It is not essential to provide a capacitor as a mounting component in order to form the power feeding side resonance circuit and the power receiving side resonance circuit.

The output voltage level of the power supply unit 10 is controlled by a drive signal (control voltage) output from the voltage variable unit 50. The voltage variable unit 50 controls the output voltage level of the power supply unit 10 according to a change in the frequency of the drive signal output from the frequency variable unit 40, thereby controlling the amplitude level of the AC voltage output from the inverter 20. .. Therefore, for example, when the output voltage level of the power supply unit 10 is increased, the amplitude level of the AC voltage output from the inverter 20 is also increased, and when the output voltage level of the power supply unit 10 is decreased, the output is output from the inverter 20. The amplitude level of the AC voltage is also reduced.

As described above, when the frequency (output frequency) of the AC voltage output by the inverter 20 is changed, even if the amplitude level of the AC voltage of the inverter 20 is kept constant, the magnetic coupling between the power feeding coil 30 and the power receiving coil 70 is performed. The degree changes, which in turn changes the received power. However, when a change in the output frequency of the inverter 20 reduces the received power, the input voltage of the inverter 20 is increased so as to compensate for the decrease in the received power, and conversely, a change in the output frequency of the inverter 20 increases the received power. In this case, if the input voltage of the inverter 20 is reduced so that the received power does not increase, the fluctuation of the received power can be reduced even if the output frequency of the inverter 20, that is, the drive frequency of the power feeding coil 30 is changed. can. As described in detail below, the wireless power transmission device 1A according to the present embodiment suppresses fluctuations in the received power by performing such control.

FIG. 2 is a graph showing an example of a time change of a frequency signal output from the frequency signal generation circuit 41, in which the horizontal axis represents time and the vertical axis represents frequency. Further, FIG. 3 is a graph showing the frequency characteristics of the EMI of the power feeding device 2 when the frequency signal of FIG. 2 is given, and the horizontal axis shows the frequency and the vertical axis shows the EMI level.

As shown in FIG. 2, this frequency signal is a triangular wave that continuously changes between the lower limit value (f1) and the upper limit value (f2) of the frequency range. The frequency signal can be repeatedly changed, for example, within the range of 100 ± 10 kHz. When such a frequency signal is given, the EMI of the power feeding device 2 is widely generated within the frequency band (f1 to f2) of the frequency signal as shown in FIG. 3, but the EMI level can be suppressed low. ..

When the inverter 20 is operating at a single drive frequency (switching frequency), electromagnetic noise of the frequency component and its harmonic components is generated from the power feeding device 2. The energy of the electromagnetic noise is an integrated value, but when the drive frequency of the inverter 20 is fixed to a single frequency (for example, 100 KHz) and operated, the electromagnetic noise is concentrated on the frequency and the energy becomes large. .. It is desirable to suppress the peak value of electromagnetic noise, but by dispersing the noise in time, the energy of electromagnetic noise at a specific frequency can be reduced, which makes it difficult for surrounding electronic devices to malfunction. Can be done.

4 and 5 are diagrams for explaining the relationship between the output voltage of the power supply unit 10 and the received power, in which (a) is the frequency characteristic of the output voltage of the power supply unit 10 and (b) is. The frequency characteristics of the received power are shown respectively.

As shown in FIG. 4A, when the output voltage of the power supply unit 10 is constant, the received power changes as shown in FIG. 4B due to a change in the frequency of the frequency signal, and the received power becomes high. Sometimes it gets lower. Such a change in the received power is due to the influence of the frequency characteristic of the electromagnetic coupling between the feeding coil 30 and the power receiving coil 70, and the drive frequency of the feeding coil 30 is the resonance of the feeding side resonance circuit including the feeding coil 30. The received power level becomes maximum when it matches the frequency and the resonance frequency of the power receiving side resonance circuit including the power receiving coil 70, and the received power decreases when it deviates from these resonance frequencies. Normally, the range in which the drive frequency of the feeding coil 30 is variable is set to a range including this resonance frequency in order to improve the power transmission efficiency. Therefore, for example, when the resonance frequency is 100 kHz, the received power level is maximized at this frequency, and the range of the drive frequency of the power feeding coil 30 is set to 100 ± 10 kHz. Further, as will be described later, from the viewpoint of preventing damage to the switching element, a range higher than the resonance frequency (inductive region) may be set as the control range of the drive frequency. Then, the power received level decreases as the drive frequency of the power feeding coil 30 deviates from 100 kHz.

In order to prevent such fluctuations in the received power, as shown in FIG. 5A, the output voltage of the power supply unit 10 is changed complementarily with the received power. That is, when the drive frequency of the power feeding coil 30 changes in the direction in which the received power level becomes lower than the desired value (maximum value), the output voltage of the power supply unit 10 is increased, and conversely, the received power level becomes the desired value (maximum value). ), When the drive frequency of the power feeding coil 30 changes, the output voltage level of the power supply unit 10 is lowered. According to such control, as shown in FIG. 5B, fluctuations in the received power can be suppressed and maintained as constant as possible.

How the received power level changes with respect to the change in the drive frequency of the power feeding coil 30 is uniquely determined if the positional relationship between the power feeding coil 30 and the power receiving coil 70 is constant. The change in the received power level when the frequency is swept is measured in advance, and the change in the received power level due to the change in the drive frequency of the power feeding coil 30 as shown in FIG. 4B obtained from the measurement result is measured. The output voltage level of the power supply unit 10 can be determined based on the conversion formula or conversion table represented.

FIG. 6 is a graph showing the time change of the output voltage of the power supply unit 10 controlled by the voltage variable unit 50, in which (a) is the frequency of the drive signal and (b) is the power supply unit corresponding to the frequency of the drive signal. The output voltages of 10 are shown respectively.

As shown in FIG. 6A, when the frequency signal is a triangular wave that continuously changes between the lower limit value (f1) and the upper limit value (f2) of the frequency range, the output voltage of the power supply unit 10 is FIG. (B) is obtained, and a pattern that repeats a reciprocating voltage change between the lower limit value (f1) and the upper limit value (f2) of the frequency range of the output voltage of the power supply unit 10 shown in FIG. 5 is supplied. Since this output voltage pattern has a complementary relationship with the received power level in the frequency range from f1 to f2, it is possible to suppress fluctuations in the received power caused by changing the drive frequency of the power feeding coil 30.

As shown in FIG. 13, in the conventional wireless power transmission device 1X in which the output voltage level of the power supply unit 10 is not changed according to the change of the output frequency of the inverter 20 (the drive frequency of the power feeding coil 30), the output frequency of the inverter 20 is set. Although the EMI level could be reduced by repeatedly changing the power, fluctuations in the received power could not be suppressed. However, in the wireless power transmission device 1A according to the present embodiment, the power supply unit 10 is provided in front of the inverter 20 and the output voltage level of the power supply unit 10 is changed according to the output frequency of the inverter 20, so that fluctuations in the received power are suppressed. be able to. That is, power is stably supplied to the power receiving device 3 side by changing the output voltage of the power supply unit 10 in a complementary manner to the received power so that the received power becomes constant even if the output frequency of the inverter 20 changes. can do.

FIG. 7 is a graph showing another example of the time change of the frequency signal output from the frequency signal generation circuit 41, in which the horizontal axis represents time and the vertical axis represents frequency. Further, FIG. 8 is a graph showing the frequency characteristics of the EMI of the power feeding device 2 when the frequency signal of FIG. 7 is given, and the horizontal axis shows the frequency and the vertical axis shows the EMI level.

As shown in FIG. 7, this frequency signal is a triangular wave that changes stepwise between the lower limit value (f1) and the upper limit value (f2) of the frequency range. When such a frequency signal is given, the EMI of the power feeding device 2 is generated discretely within the frequency band (f1 to f2) of the frequency signal as shown in FIG. 8, and is not as high as the EMI level of FIG. There is no such thing, but it can be kept low to some extent. Further, in this case, the frequency signal can be changed by digital control, and the frequency variable unit 40 can be easily configured. For example, the frequency variable unit 40 can be inexpensively configured by setting the frequency to be changed discretely by using software.

9 and 10 are block diagrams showing in detail the configuration of the wireless power transmission device 1A on the power supply device 2 side.

As shown in FIG. 9, in the wireless power transmission device 1A, the power supply unit 10 in the power supply device 2 is configured by using a non-isolated DCDC converter 11 and a PFC (power factor improving circuit) 12. The AC power supplied from the AC power supply 4 is converted into a DC voltage by the PFC 12, and further converted into a predetermined voltage level by the non-isolated DCDC converter 11. When the external power supply is a DC power supply instead of the AC power supply 4, the PFC 12 may be omitted and the non-isolated DCDC converter 11 may directly take in the DC power from the DC power supply. In this way, when the power supply unit 10 is configured by the non-isolated DCDC converter 11, the power supply unit 10 can be configured at low cost.

As shown in FIG. 10, the non-isolated DCDC converter 11 is, for example, a buck converter, which is a first switching element SW ₁ connected in series to one of a pair of balanced lines and a second switching connected in parallel to the balanced lines. an element SW _2, a power supply circuit switching elements control portion 11a for controlling the first and second on-off switching element _SW 1, SW _2, connected in parallel to the front of the first and second switching elements _SW 1, SW ₂ It includes a bypass capacitor C ₁ and a low-pass filter composed of a series inductor L ₁ and a parallel capacitor C ₂ provided after the first and second switching elements SW ₁ and SW _2. The power supply circuit switching element control unit 11a controls the DC voltage level supplied to the subsequent inverter 20 by controlling the cycle of _{turning on / off the switching elements SW 1} and SW ₂ based on the control signal from the voltage variable unit 50. ..

Inverter 20 includes a bridge circuit the third to sixth switching elements _SW 3 to SW _6, and a voltage converter circuit switching element control section 20a for controlling the third to off of the sixth switching element _SW 3 to SW ₆ The predetermined DC voltage supplied from the power supply unit 10 is converted into, for example, a 100 kHz rectangular wave AC voltage by the inverter 20 and then input to the power supply coil 30.

The control signal output from the voltage variable unit 50 is input to the power supply circuit switching element control unit 11a in the non-isolated DCDC converter 11. The non-isolated DCDC converter 11 generates a DC voltage based on the control signal and supplies it to the inverter 20. That is, the non-isolated DCDC converter 11 raises the DC voltage level so that the received power level becomes high when the power supply coil 30 is driven at a drive frequency at which the received power level becomes relatively low, and conversely, the received power. When the power feeding coil 30 is driven at a drive frequency at which the level is relatively high, the DC voltage level is lowered so that the received power level is low. Therefore, even if the drive frequency of the feeding coil 30 is continuously or discretely changed in order to reduce the EMI noise, the received power level can be kept constant.

FIG. 11 is a diagram for explaining another example of the frequency signal control method in the power feeding device 2.

When the output voltage of the power supply unit 10 is changed according to the change of the output frequency of the inverter 20 as shown in FIG. 11A, the current phase of the inverter 20 is relative to the voltage phase as shown in FIG. 11B. There are cases where the phase is advanced and cases where the phase is slow. Here, when the current phase of the inverter 20 is phase-advancing with respect to the voltage phase, a through current may flow through _{the switching elements (SWs 3 to 6 in FIG. 10) constituting the inverter 20.} For example, in a frequency band in which the phase of the output current of the inverter 20 is phase-advancing with respect to the phase of the output voltage, when the switching element SW ₃ turns from off to on and a current flows, the switching element SW ₄ turns from on to off. However, the switching element SW ₄ cannot suddenly block the current in the reverse direction from the switching element SW ₃ , which causes a through current to flow through the _{switching element SW 4.} Such a phenomenon occurs in all switching elements SW _{3 to SW 6} . The through current not only causes EMI noise, but also causes damage to the body diode in the switching element.

On the other hand, when the current phase of the inverter 20 is slower than the voltage phase, no through current is generated and the above problem can be avoided. Therefore, as shown in FIG. 11B, the frequency variable unit 40 according to the present embodiment changes the output frequency of the inverter 20 within a frequency range in which the current phase of the inverter 20 is slower than the voltage phase. According to this control method, it is possible to prevent an increase in EMI noise and damage to the switching element due to a through current flowing through _{the switching elements SW 3 to SW 6 in the inverter 20.}

As described above, since the wireless power transmission device 1A according to the present embodiment repeatedly changes the output frequency of the inverter 20 during power transmission, the noise (EMI noise) of the magnetic field component or the electric field component generated from the power supply device 2 is generated. The frequency is dispersed, and the average value and quasi-peak value of noise are reduced. Therefore, it is possible to reduce the influence of electromagnetic noise on other devices as compared with the case where the drive frequency is a single frequency. Further, by changing the DC voltage level supplied from the power supply unit 10 to the inverter 20 during power transmission according to the frequency of the drive signal from the frequency variable unit 40, the received power due to the change in the drive frequency of the power feeding coil 30 Fluctuations can be suppressed. Therefore, it is possible to suppress fluctuations in the received power while reducing electromagnetic noise. In addition, in the present embodiment, since electromagnetic noise is reduced by a relatively simple method of changing the frequency of the output voltage of the inverter 20 supplied to the power feeding coil 30, the number of parts required for noise countermeasures is increased. Can be significantly reduced, and miniaturization and cost reduction can be achieved.

FIG. 12 is a block diagram showing a configuration of a wireless power transmission device according to a second embodiment of the present invention.

As shown in FIG. 12, a feature of the wireless power transmission device 1B according to the present embodiment is that the voltage variable unit 50 operates based on a control signal from the received power detection unit 100. The received power detection unit 100 supplies the voltage variable unit 50 with a control signal according to the received power level provided from the power receiving device 3 side. The transmission of the received power information from the power receiving device 3 side to the power feeding device 2 side can be performed by, for example, wireless communication. In the present embodiment, the power feeding device 2 and the power receiving device 3 include communication units 101a and 101b that perform data communication with each other, respectively, and the output circuit unit 80 of the power receiving device 3 is on the power feeding device 2 side via the communication units 101a and 101b. The received power information is transmitted to the received power detection unit 100 of the above.

In the first embodiment, the voltage variable unit 50 converts (estimates) the received power level from the output frequency of the inverter 20 and sets the output voltage level of the power supply unit 10 so that the received power level becomes constant. However, in the case where the relative position of the power receiving coil 70 with respect to the power feeding coil 30 is not always constant, the power received power level is not uniquely determined with respect to the drive frequency of the power feeding coil 30, and the power supply unit 10 uses a conversion formula or a conversion table. It is difficult to determine the output voltage level of. In the present embodiment, since the output voltage level of the power supply unit 10 is set so that the received power level becomes constant based on the received power level which is more direct information, more accurate control of the received power becomes possible. ..

Although the preferred embodiments of the present invention have been described above, the present invention is not limited to the above embodiments, and various modifications can be made without departing from the gist of the present invention, and these are also the present invention. Needless to say, it is included in the range.

For example, the waveforms of the frequency signals shown in FIGS. 2 and 7 are examples, and various waveform patterns can be adopted. Further, the variable range of the power transmission frequency does not necessarily have to be set to include the resonance frequency at which the maximum power can be obtained, and can be set arbitrarily. Further, the frequency control method for preventing the through current of the switching element shown in FIG. 11 is not always necessary when the through current is prevented by another method.

1A, 1B, 1X Wireless power transmission device 2 Power supply device 3 Power supply device 4 AC power supply 10 Power supply unit 11 Non-isolated DCDC converter 11a Power supply circuit Switching element control unit 20 Inverter 20a Voltage conversion circuit Switching element control unit 30 Power supply coil 31 Capacitor 40 Frequency variable unit 41 Frequency signal generation circuit 42 Oscillation circuit 50 Voltage variable unit 60 Drive circuit 70 Power receiving coil 71 Condenser 80 Output circuit unit 90 Load 100 Power receiving power detection unit 101a, 101b Communication unit C ₁ Bypass capacitor C ₂ Parallel capacitor L ₁ Series Capacitor SW _{1 to SW 6} Switching element

Claims (12)

A power supply device that wirelessly transmits power to a power receiving device equipped with a power receiving coil.
Power supply unit that outputs DC voltage and
An inverter that converts the DC voltage into an AC voltage,
A feeding coil that receives the AC voltage and generates magnetic flux,
A frequency variable unit that repeatedly changes the frequency of the AC voltage during power transmission,
A voltage variable unit that repeatedly changes the output level of the DC voltage during power transmission is provided.
The voltage variable unit changes the DC voltage in a complementary manner to the received power so as to suppress fluctuations in the received power on the power receiving device side caused by the frequency change of the AC voltage caused by the frequency variable unit. Let me
The frequency variable unit changes the frequency of the AC voltage within a range in which the current phase of the inverter is delayed with respect to the voltage phase, and the lower limit value of the range in which the frequency of the AC voltage is changed is the received power. A power feeding device characterized in that it is higher than the maximum value of the resonance frequency. The voltage variable unit raises the DC voltage when the frequency of the AC voltage changes in the direction of decreasing the received power, and raises the DC voltage when the frequency of the AC voltage changes in the direction of increasing the received power. The power supply device according to claim 1, which is lowered. The voltage variable unit according to claim 1 or 2, wherein the voltage variable unit changes the DC voltage based on the frequency of a drive signal output from the frequency variable unit to the inverter in order to control the frequency of the AC voltage. Power supply device. The power supply device according to claim 3, wherein the voltage variable unit changes the DC voltage based on a conversion formula or a conversion table representing a change in the received power with a change in the frequency of the AC voltage. The power feeding device according to claim 1 or 2, wherein the voltage variable unit changes the DC voltage based on the received power information provided from the power receiving device side. The power feeding device according to any one of claims 1 to 5 , wherein the frequency variable unit continuously changes the frequency of the AC voltage during power transmission. The power feeding device according to any one of claims 1 to 5 , wherein the frequency variable unit discretely changes the frequency of the AC voltage during power transmission. The power supply device according to any one of claims 1 to 7 , wherein the power supply unit includes a non-isolated DCDC converter. A power supply device that wirelessly transmits power to a power receiving device equipped with a power receiving coil.
Power supply unit that outputs DC voltage and
An inverter that converts the DC voltage into an AC voltage,
A feeding coil that receives the AC voltage and generates magnetic flux,
A frequency variable unit that repeatedly changes the frequency of the AC voltage during power transmission,
A voltage variable unit that repeatedly changes the output level of the DC voltage during power transmission is provided.
The voltage variable unit is
When the frequency variable unit changes the frequency of the AC voltage in a direction of reducing the power received on the power receiving device side, the DC voltage is increased.
When the frequency variable unit changes the frequency of the AC voltage in the direction of increasing the received power, the DC voltage is lowered.
The frequency variable unit changes the frequency of the AC voltage within a range in which the current phase of the inverter is delayed with respect to the voltage phase, and the lower limit value of the range in which the frequency of the AC voltage is changed is the received power. A power feeding device characterized in that it is higher than the maximum value of the resonance frequency. The power supply device according to claim 9, wherein the voltage variable unit changes the DC voltage based on the frequency of a drive signal output from the frequency variable unit to the inverter in order to control the frequency of the AC voltage. .. The power supply device according to any one of claims 1 to 10.
A wireless power transmission device including a power receiving device equipped with a power receiving coil that receives at least a part of magnetic flux generated by the power feeding coil to generate an AC voltage. The wireless power transmission according to claim 11, wherein each of the power receiving device and the power feeding device includes a communication unit that performs data communication, and the power receiving device provides power received power information to the power feeding device via the communication unit. Device.

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