JP7015744B2 - Transmission equipment and power transmission system - Google Patents

Description

Embodiments of the present invention relate to power transmission devices and power transmission systems.

Non-contact power transmission (contactless power supply) from a power transmitting device to a power receiving device is becoming widespread. In the non-contact power supply, the power transmission circuit generates a high frequency current of a predetermined frequency, the power transmission coil is excited by the high frequency current, and electric power is transmitted by the magnetic field generated by the excitation. However, in non-contact power supply, there is a concern that the magnetic field leaked to the outside (leakage magnetic field) interferes with broadcasting, wireless communication, and the like. Therefore, in non-contact power supply, it is necessary to suppress the leaked magnetic field so as to satisfy the limit on the upper limit of the leaked magnetic field set by international standards and the like.

With existing technology, it is possible to reduce one of the fundamentals or specific harmonics. However, when a large-capacity battery such as an electric vehicle needs to be supplied with a large amount of non-contact power in a short time, both the fundamental wave and the harmonics have a strong influence. Therefore, it is necessary to reduce the leakage magnetic field for both the fundamental wave and the harmonics. It is conceivable to use a filter to reduce the leakage magnetic field of both the fundamental wave and the harmonics, but high suppression performance is required, which causes problems such as an increase in the size of the filter and an increase in the manufacturing cost of the device. .. Therefore, a new technique for suppressing the leakage magnetic field is required for both the fundamental wave and the harmonics.

JP-A-2010-193598 Japanese Patent No. 4671515

One embodiment of the present invention provides a device that suppresses a leakage magnetic field for both fundamental and harmonic waves.

One aspect of the present invention is a power transmission device that transmits electric power by a magnetic field, wherein an inverter that generates a high frequency current from a direct current, a drive signal output unit that outputs a drive signal that drives the inverter, and the high frequency current are used. It is equipped with a power transmission coil that generates a magnetic field by flowing. The inverter periodically changes the frequency of the high frequency current to one of a plurality of predetermined values based on the drive signal. Further, the inverter changes the waveform of the high frequency current so as to maintain the conduction angle of the inverter as the frequency of the high frequency current is changed based on the drive signal.

The block diagram which shows an example of the power transmission system which concerns on 1st Embodiment. The figure explaining frequency hopping. The figure which shows an example of the transition of the frequency of time series. The figure which shows an example of the waveform of the drive signal and the output signal of an inverter. The figure which shows the other example of the waveform of the drive signal and the output signal of an inverter. The figure explaining the change of the drive signal with the transition of a frequency. The figure which shows the amplitude characteristic of a fundamental wave and a harmonic with respect to a conduction angle. The block diagram which shows an example of the power transmission system which concerns on 2nd Embodiment. The figure which shows the schematic flow chart of the process in the case of controlling the start of frequency hopping and conduction angle control. The figure which shows the transition of the current of a coil unit when the start of frequency hopping and conduction angle control is controlled.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.

(First Embodiment)
FIG. 1 is a block diagram showing an example of a power transmission system according to the first embodiment. The electric power transmission system according to the first embodiment includes a power transmission device 1 that transmits electric power by a magnetic field and a power receiving device 2 that receives the electric power.

The power transmission device 1 includes an AC power supply 11, an AC / DC converter 12, an inverter 13, a drive signal output unit 14, and a power transmission coil unit (resonator) 15. The power receiving device 2 includes a power receiving coil unit (resonator) 21 and a rectifying unit 22.

In the power transmission system of the present embodiment, power is received from the power transmission device 1 by using the magnetic field generated from the high frequency current by electromagnetic induction and obtaining power from the magnetic field generated by the power transmission device 1 by the power reception device 2 by electromagnetic coupling. Power is transmitted to the device 2. That is, in the power transmission system of the present embodiment, the power receiving device 2 is supplied with power in a non-contact manner.

However, the magnetic field generated in the power transmission device 1 of the non-contact power supply system is not only used for power transmission to the power receiving device 2, but a part of the magnetic field interferes with surrounding devices as a leakage magnetic field. Therefore, in the power transmission system of the present embodiment, power energy is spread to a predetermined bandwidth (spread spectrum) on the frequency axis by frequency hopping.

For example, the frequency of the high frequency current is changed by changing the switching frequency when the high frequency current that generates the magnetic field is generated. It is known that this expands the frequency band of the magnetic field and reduces its intensity as compared to the case where the frequency of the high frequency current is not changed. That is, frequency hopping is to change the frequency of the magnetic field, that is, the frequency of the high frequency current. As a result, the strength of the leakage magnetic field can be suppressed.

FIG. 2 is a diagram illustrating frequency hopping. FIG. 2A is a diagram showing the relationship between frequency and magnetic field strength when frequency hopping is not performed, that is, when power is transmitted at only one frequency. In the example of FIG. 2A, it is assumed that power transmission is performed only at 85 kHz. Therefore, a graph with one peak (maximum point) is shown at the point of 85 kHz.

FIG. 2B is a diagram showing the relationship between frequency and magnetic field strength in the case of frequency hopping, that is, in the case of power transmission at a plurality of frequencies. In the example of FIG. 2B, power transmission is performed at 20 frequencies centered on 85 kHz, and a graph having 20 peaks is shown. Specifically, the smallest frequency Fss_START (f ₁ ) is set to 81.2 kHz, the frequency interval used is set to 400 Hz, and the number of frequencies is 20, which is the highest. The frequency Fss_END (f ₂₀ ) is set to 88.8 kHz.

Hereinafter, when frequency hopping is performed, the value at which the frequency transitions is simply referred to as a transition value. Further, numbers are assigned in order from the smallest transition value, and the i ( _i is an integer of 1 or more) th transition value is represented as fi. That is, the first transition value f ₁ is the minimum transition value, the transition value fi is the _i -th largest transition value, and _{fi + 1} > _fi is established. Further, the number of transition values is described as the number of transitions. In the example of FIG. 2B, the number of transitions is 20.

In frequency hopping, at a certain timing, the frequency transitions from one of the transition values to any of the other transition values. By performing the transition many times, the frequency is diffused and the strength of the leakage magnetic field is reduced. Further, the difference in frequency per frequency change, that is, the difference between the frequency after the change and the frequency before the change (fi _{+ 1} - _fi ) is described as the transition width.

The electric power when such frequency hopping is performed is the same as the electric power when frequency hopping is not performed in the long term. Therefore, the power per frequency (power density) is smaller in the case of frequency hopping than in the case of no frequency hopping. When the diffusion bandwidth is described as Bss, the average electric energy over a long period of time is reduced by a function of 1 / Bss. In this way, by performing frequency hopping, power energy is diffused at a plurality of frequencies, and the power density measured as a leakage magnetic field is reduced. The effect of reducing the leakage magnetic field by frequency hopping is described as the frequency spread effect.

The diffusion bandwidth may be larger than the interval between the minimum frequency and the maximum frequency. In other words, when the diffusion bandwidth is predetermined, the maximum frequency and the minimum frequency may be determined so that the interval between the maximum frequency and the minimum frequency is smaller than the diffusion bandwidth. This is because if the interval between the maximum frequency and the minimum frequency is made the same as the spread bandwidth, the spread bandwidth may be exceeded due to the frequency spread during frequency hopping. In the example of FIG. 2B, the diffusion bandwidth is defined as the number of frequencies × the transition width, and the diffusion bandwidth is 8 kHz (20 × 400 Hz), so that the interval between the maximum frequency and the minimum frequency (Fss_END-Fss_START =). It is larger than 7.6 kHz). That is, half the bandwidth of the transition width is given as a buffer at both ends of the band between the maximum frequency and the minimum frequency.

In the present embodiment, the frequency spreading effect is obtained by such frequency hopping, that is, by sequentially shifting the frequency of the high frequency current at regular time intervals. However, while the frequency diffusion effect is effective for fundamental waves, it is limited for harmonics. This is due to the pass band (RBW) of the filter set by a measuring instrument such as a spectrum analyzer when measuring the leakage magnetic field.

The RBW of the filter is regulated by laws and regulations based on those standards such as international standards such as CISPR. For example, the transmission frequency (frequency of the fundamental wave) for which international standardization is being considered in the field of electric vehicles is the 85 kHz band. The frequency band of the low frequency harmonics generated by the signal of the fundamental wave 85 kHz band is the 255 kHz band for the third harmonic and the 425 kHz band for the fifth harmonic. In the CISPR standard, the frequency band division including the fundamental wave 85 kHz band is defined as 9 kHz to 150 kHz (band A), and the pass band RBW of the measuring instrument is defined as 100 to 300 Hz (reference bandwidth is 200 Hz). .. On the other hand, the division including the 255 kHz band of the third harmonic and the 425 kHz band of the fifth harmonic is defined as 150 kHz to 30 MHz (band B), and the pass bandwidth RBW is 8 kHz to 10 kHz (reference bandwidth 9 kHz). .. As described above, since the passband RBW of the harmonics is much larger than the passband RBW of the fundamental wave, the frequency diffusion effect on the harmonics is significantly smaller than that of the fundamental wave.

なお、上式において、記号Ｂｓｓは基本波の拡散帯域幅［ｋＨｚ］を、記号Ｎは高調波の次数を、記号ＲＢＷは測定器の６ｄＢ通過帯域幅［ｄＢ］を表す。基本波の拡散帯域幅が８．０ｋＨｚの場合、基本波、３次高調波、５次高調波、および７次高調波に対する周波数ホッピングによる漏洩磁界の低減量は、それぞれ、１３．０ｄＢ、１．３ｄＢ、３．５ｄＢ、４．９ｄＢとなる。また、基本波の拡散帯域幅が５．０ｋＨｚの場合、基本波、３次高調波、５次高調波、および７次高調波に対する周波数ホッピングによる漏洩磁界の低減量は、それぞれ、１１．０ｄＢ、０ｄＢ、１．４ｄＢ、２．９ｄＢとなる。このことから分かるように、高調波に対する周波数拡散効果は小さく、特に、３次高調波の周波数拡散効果はほとんど得られないことが分かる。そのため、給電の電力が非常に大きい場合では、高調波の漏洩磁界により、漏洩磁界の上限に関する制限を満たすことができなくなる恐れがある。 For example, it is assumed that frequency hopping is performed with a diffusion bandwidth of 8 kHz for a fundamental wave in the 85 kHz band. In this case, the diffusion bandwidth of the third harmonic is tripled to 24 kHz, and the diffusion bandwidth of the fifth harmonic is quintupled to 40 kHz. That is, the diffusion bandwidth of the N (N is an odd number of 1 or more) harmonics is equal to the diffusion bandwidth of the fundamental wave × N. The amount of reduction in the leakage magnetic field during diffusion is expressed by the following equation under the optimum conditions.

In the above equation, the symbol Bss represents the diffusion bandwidth [kHz] of the fundamental wave, the symbol N represents the order of the harmonics, and the symbol RBW represents the 6 dB passband bandwidth [dB] of the measuring instrument. When the diffusion bandwidth of the fundamental wave is 8.0 kHz, the amount of reduction of the leakage magnetic field by frequency hopping for the fundamental wave, the third harmonic, the fifth harmonic, and the seventh harmonic is 13.0 dB, 1. It becomes 3 dB, 3.5 dB, and 4.9 dB. When the diffusion bandwidth of the fundamental wave is 5.0 kHz, the amount of reduction of the leakage magnetic field by frequency hopping for the fundamental wave, the third harmonic, the fifth harmonic, and the seventh harmonic is 11.0 dB, respectively. It becomes 0 dB, 1.4 dB, and 2.9 dB. As can be seen from this, the frequency diffusion effect on the harmonics is small, and in particular, the frequency diffusion effect on the third harmonic is hardly obtained. Therefore, when the power supply is very large, the leakage magnetic field of harmonics may make it impossible to satisfy the limitation on the upper limit of the leakage magnetic field.

It is also conceivable to insert a filter between the inverter 13 and the power transmission coil unit 15 in order to suppress the harmonics. However, in a general filter, the higher the harmonic, the larger the amount of suppression, so the effect on the third harmonic is small. Further, since the frequency of the third harmonic is close to that of the fundamental wave, the filter may affect the fundamental wave. Therefore, it is technically difficult to suppress the third harmonic by the filter.

Therefore, in the power transmission system of the present embodiment, the leakage magnetic field for a specific harmonic is reduced by adjusting the conduction angle of the inverter 13. The details of the conduction angle, the method of adjusting the conduction angle, and the effect thereof will be described together with the components.

The internal configuration of the power transmission device 1 will be described.

The AC power supply 11 supplies an alternating current to the AC / DC converter 12. The AC power supply 11 may be a three-phase power supply or a single-phase power supply. Further, a power factor improving circuit, a rectifier, or the like may be connected to the AC power supply 11.

The AC / DC converter 12 converts the supplied alternating current into a direct current. Then, a direct current is sent from the AC / DC converter 12 to the inverter 13.

The inverter 13 generates a high frequency current from the direct current from the AC / DC converter 12. Specifically, the inverter 13 includes a plurality of switching elements (hereinafter referred to as switches) as constituent elements, and the input DC current is designated as an alternating current (high frequency current) of a desired frequency by switching by each switch. Convert at the timing that was done. The conversion timing is based on the drive signal (switching signal) from the drive signal output unit 14. That is, high-frequency current generation and frequency hopping are performed based on the drive signal.

In the example of FIG. 1, the switch A1 and the switch A2 are connected in series, and a leg A having the switch A1 as an upper arm and the switch A2 as a lower arm is configured. Further, the switch B1 and the switch B2 are connected in series, and a leg B having the switch B1 as an upper arm and the switch B2 as a lower arm is configured. Then, leg A and leg B are connected in parallel. The connection node between the switch A1 and the switch A2 is connected to one end of the power transmission coil unit 15. The connection node between the switch B1 and the switch B2 is connected to the other end of the power transmission coil unit 15. Further, a direct current is input to one end of the switch A1 that is not connected to the switch A2 and one end that is not connected to the switch B1 and the switch B2. As a result, a high-frequency current is generated from the direct current of the AC / DC converter 12 and flows into the power transmission coil unit 15.

The drive signal output unit 14 generates the above-mentioned drive signal and outputs it to each switch in the inverter 13. By inputting the drive signal corresponding to each switch, each switch switches and an alternating current (high frequency current) is generated from the direct current. That is, the drive signal output unit 14 controls the inverter 13. In the example of FIG. 1, it is assumed that the drive signal A1 is input to the switch A1, the drive signal A2 is input to the switch A2, the drive signal B1 is input to the switch B1, and the drive signal B2 is input to the switch B2.

The drive signal is given to each switch as a square wave. The square wave is generated based on predetermined set values for the duty ratio, dead time, and the like. By sequentially transitioning the frequency of this rectangular wave, the frequency of the magnetic field of power transmission changes.

The timing of the frequency transition can be instructed by dividing the clock signal to generate a drive signal. It is assumed that the transition values, the order in which the transition values are instructed, the transition time interval (the period during which the frequency is maintained), and the like are registered in advance in the drive signal output unit 14. That is, the drive signal output unit selects one circumferential transition value from a plurality of predetermined transition values based on a predetermined rule, and outputs a drive signal adjusted to indicate the selected transition value. do. For example, as in the example of FIG. 2B, it is assumed that 20 transition values from f ₁ to f ₂₀ are registered in the drive signal output unit 14. In that case, the drive signal output unit 14 selects one frequency from the 20 transition values based on a predetermined rule, and outputs the drive signal so as to be the selected frequency. The rule determines, for example, the transition values from f ₁ to f ₂₀ in ascending order (order toward the maximum transition value) or descending order (order toward the minimum transition value), and is the terminal transition value. After f ₁ or f ₂₀ is determined, it may be determined in the reverse order of the previous order.

FIG. 3 is a diagram showing an example of a time-series frequency transition. In FIG. 3, the horizontal axis represents time and the vertical axis represents transition value numbers. The example of FIG. 3 shows the frequency transition when the transition based on a predetermined rule is repeated using the 20 transition values from f ₁ to f ₂₀ shown in the example of FIG. 2 (B). The predetermined rule is that the transition value is changed from the minimum transition value f ₁ in ascending order, and after reaching the maximum transition value f ₂₀ , the transition value is changed in descending order and returned to the minimum transition value f ₁ . As shown in FIG. 3, when the frequency of the magnetic field is periodically transitioned to a plurality of transition values, the frequency diffusion effect can be stably obtained. That is, in order to make the frequency a periodic transition, it is preferable to control the transition so as to repeatedly transition to the same transition value at a constant cycle.

Note that one cycle in a periodic transition as shown in FIG. 3 is again from the time when the frequency transitions from the transition value f _{k + 1} or f _k-1 to the transition value f k when k is defined by an integer larger than 1. It is until the time when the transition from the same transition value f _{k + 1} or f _k-1 to the transition value f _k . For example, one cycle is from the time when the transition value f ₁₁ is changed to the transition value f ₁₂ to the time when the transition value f ₁₁ is changed to the transition value f ₁₂ again.

In the present embodiment, the transition value at the start of frequency hopping, that is, the initial value may be any transition value, and the transition order may be descending first or ascending first. .. For example, frequency hopping may start at line position _f5 and then transition to _f6 or then to _f4 .

Further, the frequency maintenance time is not strictly constant and may be appropriately determined according to the specifications. Further, the maintenance time may be different for each transition value. For example, in FIG. 3, the maintenance time of the transition values f ₁ and f ₂₀ is doubled. This is realized by lengthening the timing until the drive signal output unit 14 adjusts the drive signal so as to transition to the next transition value when the drive signal for transitioning to the transition values f ₁ and f ₂₀ is output. You may. Alternatively, when the drive signal for transitioning to the transition values f ₁ and f ₂₀ is output, the drive signal for transitioning to the transition values f ₁ and f ₂₀ is output again at the next timing for adjusting the drive signal. You may.

As shown in FIG. 3, when the frequencies first transition in ascending or descending order and then in the reverse order, the shape of the graph becomes a triangle. Therefore, such a transition situation is called "triangular wave transition". Define.

In this way, the drive signal output unit 14 periodically changes the frequency of the drive signal in order to perform frequency hopping. As a result, the inverter 13 periodically changes the frequency of the high frequency current based on the drive signal. Further, the drive signal output unit 14 also changes the waveform of the drive signal so as to maintain the conduction angle of the inverter 13 when the frequency is changed. The inverter changes the waveform of the high frequency current according to the change of the frequency of the high frequency current based on the drive signal. This keeps the leakage magnetic field for a particular harmonic reduced. The conduction angle represents the ratio of the continuity period of the inverter 13 to one cycle of the output waveform of the inverter 13 as an angle.

A method of adjusting the conduction angle will be described with reference to FIGS. 4 and 5. FIG. 4 is a diagram showing an example of waveforms of the drive signal and the output signal of the inverter 13. FIG. 4 shows that the conduction angle can be changed by changing the duty ratio of the drive signal.

In the following description, it is assumed that the voltage VIN input from the AC / DC converter 12 is constant. Further, the drive signals supplied to the four switches are all pulse signals having the same duty ratio and the same period _ti . The period ti is the reciprocal of the transition value _fi at that time ( ₌ 1 / _fi ).

In FIG. 4A, each drive signal is adjusted so that the fundamental wave component of the output voltage of the inverter 13 becomes the maximum, that is, the same as the input voltage VIN. Specifically, in FIG. 4A, the duty ratio of each drive signal is 1/2 (T3 / T2). Further, the drive signal A2 has a phase difference (corresponding to T1) of 180 degrees with respect to the drive signal A1. That is, the drive signal A1 is a signal obtained by inverting the drive signal A2, and the switch A1 and the switch A2 are driven complementarily. The drive signal A2 can be said to be a signal obtained by inverting the drive signal A1.

The phase difference means the time difference of the waveform between the periodic signals. When the period of the drive signal is _ti , it means that the phase difference of P degree has a time difference of about "P / 360 × _ti ".

Further, the drive signal B1 and the drive signal B2 have a phase difference of 180 degrees. That is, the drive signal B1 is a signal obtained by inverting the drive signal B2, and the switch B1 and the switch B2 are also driven complementarily. The drive signal B2 can be said to be a signal obtained by inverting the drive signal B1. Further, the drive signal B1 and the drive signal A1 have a phase difference of 180 degrees. Therefore, the drive signal A1 and the drive signal B2 can be said to be the same signal, and the drive signal A2 and the drive signal B1 can be said to be the same signal.

When each drive signal has such a phase relationship, the output voltage of the inverter 13 becomes a rectangular wave as shown in FIG. 4A. The period during which the output power is ON, that is, the period during which the entire inverter 13 is conducting is T4. Since the conduction angle represents the ratio of the continuity period of the inverter 13 to one cycle of the output waveform of the inverter 13 as an angle, in this case, it is represented by 360 × T4 / T2, and the conduction angle is represented by 360 × T4 / T2. It is calculated as 180 degrees.

In FIG. 4A, the broken line waveform displayed overlaid on the square wave represents the fundamental wave component of the output voltage. The fundamental wave component can be obtained by frequency-decomposing the output voltage signal at the transition value _fi of the frequency at that time and extracting only the fundamental wave component.

In FIG. 4B, the duty ratio of each drive signal is changed to 1/3 (T5 / T2). As a result, the conduction angle is changed to 120 degrees (360 × T6 / T2). Further, in FIG. 4C, the duty ratio of each drive signal is adjusted to 1/4 (T7 / T2). Thereby, the conduction angle is adjusted to 90 degrees (360 × T8 / T2).

By adjusting the duty ratio of each drive signal in this way, the waveform of the high-frequency current is changed, and the conduction angle can be arbitrarily adjusted. The amplitude of the fundamental wave component of the output voltage is lower than that of the input voltage VIN.

When the duty ratio of the drive signal is 50%, if the timing of the drive signal varies, the switch A1 and the switch A2 may be turned on at the same time, and the switch B1 and the switch B2 may be turned on at the same time. .. When such a situation occurs, the output of the AC / DC converter 12 is short-circuited, and a large current may be generated. In order to prevent this, generally, the duty ratio is adjusted so as not to be 50% by setting the dead time or the like. Therefore, even in this embodiment, the duty ratio does not have to be completely 50%.

FIG. 5 is a diagram showing another example of waveforms of the drive signal and the output signal of the inverter 13. FIG. 5 shows that the conduction angle can be adjusted by adjusting the phase difference between leg A and leg B.

In FIG. 5A, the drive signal and the output signal of the inverter 13 are in the same situation as in FIG. 4A. The phase difference between the leg A and the leg B is, that is, the phase difference between the drive signal A1 and the drive signal B1 is 180 degrees, and the phase difference between the drive signal A2 and the drive signal B2 is also 180 degrees.

On the other hand, in FIG. 5B, the phase difference between the pair of the drive signal A1 and the drive signal A2 and the pair of the drive signal B1 and the drive signal B2 is the same as in FIG. The phase difference of the pair of the signal B1 and the phase difference of the pair of the drive signal A2 and the drive signal B2 are adjusted from 180 degrees.

With reference to the drive signal A1, the drive signal B1 is P degrees (corresponding to T5) ahead of the drive signal A1. With reference to the drive signal B1, the drive signal A1 is delayed by P degrees (corresponding to T5) from the drive signal B1. Here, the P degree is set to 120 degrees. At this time, as shown in FIG. 5B, the output voltage waveform has a period (corresponding to T6) in which the output voltage becomes 0. The conduction angle decreases from 180 degrees due to the period during which the output voltage becomes 0. By adjusting the phase difference of the drive signal in this way, the conduction angle can be arbitrarily adjusted. The period during which the entire inverter 13 is conducting (corresponding to T7) is a period from when the drive signal B1 is turned off until the drive signal A1 is turned off. Since the drive signal A1 is delayed by P degrees (corresponding to T5) from the drive signal B1, the conduction angle in FIG. 5B is 120 degrees.

In FIG. 5C, the phase difference P degree between the drive signal B1 and the drive signal A1 is 240 degrees (corresponding to T8), which is larger than that in FIG. 5B. Even in this case, as in FIG. 5B, a period (corresponding to T9) in which the output voltage becomes 0 occurs. The conduction angle decreases from 180 degrees due to the period during which the output voltage becomes 0. The period during which the entire inverter 13 is conducting (corresponding to T10) is a period from when the drive signal A1 is turned on until the drive signal B1 is turned on. Although the drive signal A1 is delayed by P degrees from the drive signal B1, it can be said that the drive signal A1 is 360-P degrees ahead of the drive signal B1 because the drive signal has periodicity. Therefore, the conduction angle in FIG. 5 (C) is also 120 degrees, which is the same as in FIG. 5 (B).

As shown in FIGS. 5 (B) and 5 (C), when it is desired to adjust the conduction angle to the angle P, the drive signal A1 may be delayed by P degrees or 360-P degrees from the drive signal B1. good. Alternatively, the drive signal A1 may be advanced by 360-P degrees or P degrees from the drive signal B1.

By changing the phase difference of each drive signal in this way, the waveform of the high-frequency current is changed, and the conduction angle can be arbitrarily adjusted. The amplitude of the fundamental wave component of the output voltage is lower than that of the input voltage VIN.

FIG. 6 is a diagram illustrating a change in the drive signal due to a frequency transition. FIG. 6A shows the waveforms of the drive signal and the output signal of the inverter 13 when the frequency transition value is 80 kHz. FIG. 6B shows the waveforms of the drive signal and the output signal of the inverter 13 when the frequency transition value is 88 kHz. Here, when the frequency changes from 80 kHz to 88 kHz, the case where the conduction angle is controlled by using the phase difference of the drive signal will be described. Also, the conduction angle should be kept at 120 degrees.

When the frequency is 80 kHz, the period T1 is 12.5 μsec. At this time, the phase difference between the legs (the phase difference between the drive signals A1 and B1) St1 is set to 120 degrees in order to make the conduction angle 120 degrees. That is, the delay time of the drive signal B1 with respect to the drive signal A1 is adjusted to be T1 × 120/360 = 4.2 μsec. In other words, the drive signal output unit 14 generates the drive signal A1 and the drive signal B1 having a phase difference of 4.2 μsec. The conduction time Ct1 is also 4.2 μsec.

Next, at the timing when the frequency is changed to 88 kHz, the drive signal output unit 14 changes the frequency division number of the clock division cycle for generating the drive signal, for example, so that the cycle of the high frequency signal is T2 = 11. Change to a drive signal that takes 4 μs. Further, in order to keep the conduction angle at 120 degrees, the drive signal output unit 14 changes the phase difference (leg time) between the drive signal A1 and the drive signal B1. Since the delay time St2 for setting the conduction angle to 120 degrees is obtained by the period × conduction angle / 360, it may be T2 × 120/360 = 3.8 μsec. Therefore, the drive signal output unit 14 generates the drive signal A1 and the drive signal B1 having a phase difference of 3.8 μsec at the timing of the frequency transition.

If the frequency of the high frequency signal is changed without any control, the conduction angle is not maintained. However, in this way, the conduction angle can be kept constant by adjusting the phase difference or duty ratio of the drive signal at the timing of transitioning the frequency of the high frequency signal.

Then, by keeping the conduction angle at an appropriate value, the leakage magnetic field due to the high frequency signal can be suppressed. FIG. 7 is a diagram showing the amplitude characteristics of the fundamental wave and the harmonic with respect to the conduction angle. The vertical axis represents the amplitude, that is, the strength of the magnetic field, and the horizontal axis represents the conduction angle. The conduction angle at which the amplitude is zero is shown. As shown in FIG. 7, the value of the conduction angle at which the amplitude becomes zero differs depending on the target harmonic. The amplitude is zero at 120 degrees for the 3rd harmonic, 72 degrees and 144 degrees for the 5th harmonic, and 51 degrees, 103 degrees, and 154 degrees for the 7th harmonic. As described above, in principle, it can be seen that the conduction angle at which the Nth harmonic amplitude is zero is an integral multiple of 360 / N. Therefore, for example, when the purpose is to reduce the leakage magnetic field of the third harmonic, it is possible to reduce the leakage magnetic field of the third harmonic most by keeping the conduction angle at 120 degrees.

As described in the previous example, when frequency hopping is performed for the fundamental wave in the 85 kHz band with a spread bandwidth of 8 kHz, the fundamental wave, the third harmonic, the fifth harmonic, and the seventh harmonic are subjected to. The amount of reduction of the leakage magnetic field by frequency hopping is 13.0 dB, 1.3 dB, 3.5 dB, and 4.9 dB, respectively. In this frequency hopping, if the conduction angle is kept at 120 degrees, the amount of reduction of the third harmonic, which was minute in the frequency hopping, can be increased.

As can be seen from FIG. 7, power transmission mainly depends on the fundamental wave having a large amplitude. Therefore, when there are a plurality of conduction angles at which the harmonics are zero, it is preferable to use the conduction angle having the larger amplitude of the fundamental wave in order to transmit as large a power as possible. For example, when the leakage magnetic field of the 5th harmonic is targeted for reduction, the amplitude of the 5th harmonic is minimized when the conduction angles are 72 degrees and 144 degrees, but it is better to set the conduction angle to 144 degrees. It can transmit a large amount of power. That is, assuming that 0 to 180 degrees is a range in which the conduction angle can be taken, when there are a plurality of conduction angle candidates, it is preferable to use the larger conduction angle from the viewpoint of the amount of power transmission. That is, when suppressing the Nth harmonic, by maintaining the conduction angle at 180 × (N-1) / N degree, it is possible to suppress the target harmonic and transmit a larger power. ..

On the other hand, if the required reduction amount can be obtained, it is not always necessary to maintain the conduction angle at an angle at which the leakage magnetic field can be most reduced. For example, when it is desired to reduce the third harmonic, it is not necessary to accurately adjust the conduction angle to 120 degrees, and if the required reduction amount can be obtained even if the conduction angle is adjusted to 135 degrees, adjust it to 135 degrees. May be good. Comparing 120 degrees and 135 degrees, the amplitude of the fundamental wave is higher at 135 degrees. Since the larger the amplitude of the fundamental wave, the larger the power can be transmitted, it is conceivable to set the conduction angle to 135 degrees from the viewpoint of power efficiency when transmitting power.

Further, the conduction angle may be kept within a predetermined range instead of being maintained at a fixed value. For example, if the required reduction amount can be obtained even if the conduction angle is adjusted to 135 degrees, the conduction angle may be maintained within the allowable range with the allowable range from 120 degrees to 135 degrees. By doing so, the power to be transmitted can be increased or decreased by adjusting the conduction angle within the allowable range. In this way, the control content for the conduction angle may be determined in consideration of various factors such as the transmitted power, the power efficiency, and the amount of reduction of the leakage magnetic field. For example, when it is desired to suppress the third harmonic to 1/3 or less of the maximum value, as can be seen from FIG. 7, the object can be achieved if the conduction angle is in the range of 10 degrees before and after 120 degrees. Therefore, the conduction angle may be maintained within the permissible range with the permissible range of 110 degrees to 130 degrees. In this way, how much the conduction angle is maintained may be adjusted according to the surrounding environment and the like.

The permissible range of fluctuation of the conduction angle may be predetermined according to the permissible reduction amount of the leakage magnetic field. As shown in FIG. 7, since the harmonic has a plurality of amplitude peaks, the allowable range is the angle from one of the amplitude peaks to the next amplitude peak at the maximum. That is, assuming that the symbol M is an odd number less than N, the allowable range of the conduction angle is in the range from M × 180 / N to (M + 2) × 180 / N.

The frequency transition interval due to frequency hopping depends on the number of transitions, the diffusion bandwidth, and the like, but it is assumed that the frequency transition interval is approximately every 50 μs to 500 μs. Therefore, it is preferable to calculate the set values such as the transition value, the transition timing, and the phase difference of the drive signal in advance in order to avoid complicated control. These settings may be calculated each time during frequency hopping, but in that case the main at intervals very short for the processing power of the general purpose computer device 1 equipped with the power transmission device 1 of this embodiment. Writing from the CPU (Central Processing Unit) to the hardware register frequently occurs. Changing the register each time during frequency hopping is not preferable because most of the processing power of the CPU and the bandwidth for writing to the memory are devoted to the frequency hopping process.

For example, values such as the transition value, the period length for maintaining the frequency, the clock division ratio when changing the frequency, and the phase difference of the drive signal when changing the frequency are stored in the memory table, and the transition of the transition value is stored. The order may be implemented on the hardware. When writing the set value from the main CPU to the memory table, it is desirable that the setting value is written in a state where the load on the main CPU is light, such as before the start of power transmission. By doing so, it is possible to automatically perform frequency hopping and conduction angle control processing by the hardware, using the signal instructing the execution of frequency hopping from the main CPU as a signal.

Alternatively, a dedicated circuit for controlling frequency hopping and conduction angle, for example, a DSP (Digital Signal Processor), may be installed in the power transmission circuit separately from the main CPU. As described above, it is preferable that the processing of frequency hopping and conduction angle control is executed by an arithmetic unit composed of hardware, DSP, memory, etc., which is independent of the main CPU.

In this way, the drive signal output unit 14 can output a drive signal for performing frequency hopping and maintaining the conduction angle of the inverter 13.

The power transmission coil unit 15 generates a magnetic field by flowing a high frequency current. When the magnetic field generated from the power transmission coil unit 15 reaches the power reception coil unit 21, interconnection occurs between the power transmission coil unit 15 and the power reception coil unit 21. As a result, the power receiving coil unit 21 can receive electric power from the power transmission coil unit 15. In this way, power is transmitted in a non-contact manner. The type of coil of the power transmission coil unit 15 may be either a solenoid type or a helical type.

The power transmission coil unit 15 may have only a coil, but may include a capacitor as shown in FIG. The capacitor connected between the coil and the inverter 13 operates as a compensation circuit. That is, the capacitor compensates for the high frequency current for the purpose of improving the power factor before the high frequency current is sent to the coil, reducing the phase difference between the current and the voltage, and the like. Although the capacitors are connected in series to the coil in FIG. 1, they may be connected in parallel. Further, a filter may be inserted between the inverter 13 and the power transmission coil unit 15 for the purpose of reducing a higher-order leakage magnetic field.

As described above, the power transmission device 1 performs both frequency hopping and maintenance of the conduction angle of the inverter 13. If only frequency hopping is performed, the conduction angle may change and the strength of the leakage magnetic field of the target Nth harmonic may exceed the upper limit. However, before and after frequency hopping, the conduction angle may be fixed or allowed. By keeping it within the range, the strength of the leakage magnetic field of the Nth harmonic can be kept suppressed. In this way, the power transmission device 1 can transmit power to the power receiving device 2 while suppressing the leakage magnetic field for both the fundamental wave and the harmonics.

The power receiving device 2 receives the electric power generated in the power receiving coil by mutual induction. Specifically, a high frequency current is generated in the power receiving coil unit 21. The type of coil of the power receiving coil unit 21 may be any type as in the power transmission coil unit 15.

The rectifying unit 22 rectifies the high frequency current from the power receiving coil 21. Although FIG. 1 shows an example configured by a full-bridge diode, the configuration is not limited to this example. Further, the current after rectification contains a large amount of ripple components. Therefore, in order to eliminate ripple, the rectifying unit 22 may include a ripple removing circuit including a capacitor, an inductor, or a combination thereof. Further, a DC-DC converter that performs voltage conversion after rectification may be connected to the rectification unit 22.

Then, the direct current output from the rectifying unit 22 is supplied to the power supply destination. The power supply destination is assumed to be a battery or other electric device. The power supply destination may be inside or outside the power receiving device 2.

As described above, according to the first embodiment, the phase difference or duty of the drive signal is maintained at the same timing as the frequency transition so that the conduction angle of the inverter 13 is kept constant even if the frequency hopping is performed. The ratio is adjusted. As a result, the effect of reducing the leakage magnetic field can be obtained for both the fundamental wave and the harmonics.
(Second embodiment)

FIG. 8 is a block diagram showing an example of the power transmission system according to the second embodiment. The power transmission device 1 of the second embodiment further includes a power transmission control unit 16 and a DC / DC converter 17. The power transmission control unit 16 improves the accuracy of the reduction effect in the second embodiment as compared with the first embodiment.

Further, as described in the first embodiment, the power transmission device 1 and the power receiving device 2 further include a notch filter in order to reduce the leakage magnetic field of harmonics other than the harmonics for which the conduction angle is controlled. May be. FIG. 8 shows an example provided with a notch filter. The notch filter 18 of the power transmission device 1 is provided between the output side of the inverter 13 and the power transmission coil unit 15. The notch filter 23 of the power receiving device 2 is provided between the power receiving coil unit 21 and the rectifying unit 22. The first embodiment may include the notch filters 18 and 23.

The notch filters 18 and 23 suppress the leakage magnetic field of a predetermined harmonic. Therefore, the harmonics not targeted by the notch filter 18 may be suppressed by controlling the conduction angle. For example, when the target of suppression of the notch filter 18 is the third harmonic, the fifth harmonic may be suppressed by setting the conduction angle of the inverter 13 to 144 degrees. In this way, it is possible to evenly reduce the leakage magnetic fields of the fundamental wave and all harmonics.

The power transmission control unit 16 instructs the drive signal output unit 14 whether or not frequency hopping and conduction angle control can be performed. In other words, the power transmission control unit 16 instructs the drive signal output unit 14 to periodically change the frequency of the high frequency current and change the waveform of the high frequency current at least one of them. This makes it possible to deal with the case where either frequency hopping or conduction angle control is performed and the other is not performed.

For example, the power transmission control unit 16 receives an electric signal from a switch provided on the outside of the housing of the power transmission device 1 and operated by the user, and determines whether or not frequency hopping and conduction angle control can be performed based on the electric signal. You may judge. Alternatively, it may be determined whether or not the implementation is possible from the value of the high frequency current based on a predetermined power threshold value or the like described later. Then, the process start signal (start instruction) or stop signal (stop instruction) is output to the drive signal output unit 14 based on the determination result of whether or not the implementation is possible. Upon receiving the signal, the drive signal output unit outputs a drive signal having a frequency or waveform according to the instruction content of the power transmission control unit 16. As a result, at least one of the periodic change of the frequency of the high frequency current and the change of the waveform of the high frequency current is started or stopped in the inverter.

Further, the power transmission control unit 16 instructs the DC / DC converter 17 to increase or decrease the power transmission power. The DC / DC converter 17 is provided between the AC / DC converter 12 and the inverter 13. The DC / DC converter 17 can step up or down the direct current to a desired voltage value by adjusting the duty ratio of the direct current flowing through it. Maintaining the conduction angle as described above reduces the output power of the inverter 13. However, the power transmission control unit 16 can compensate the power transmission power by instructing the DC / DC converter 17 to increase or decrease the output power, that is, the value VIN of the input voltage to the inverter 13. For convenience of explanation, the second embodiment includes the DC / DC converter 17, but the first embodiment may include the DC / DC converter 17.

The power transmission device 1 normally transmits power in a predetermined dynamic range. In the present embodiment, this dynamic range can be divided into two, a power increase / decrease by the AC / DC converter 12 and a power increase / decrease by the inverter 13. As a result, the individual dynamic range can be narrowed and the circuit design can be facilitated.

As described above, the increase / decrease of the output power can be controlled by adjusting the conduction angle. For example, if the conduction angle may be adjusted between 15 and 180 degrees, the amplitude of the fundamental wave can be controlled in the range of approximately 0.1 to 1.0, which is the output power of the inverter 13. Is controllable in the corresponding range.

For example, when power transmission is performed in a dynamic range of 0 to 120 kW as a whole, a dynamic range of 70 kW (including a margin of 10 kW) is assigned to the AC / DC converter 12, and a dynamic range of 70 kW (including a margin of 10 kW) is assigned to the inverter 13. do. In this case, the load on the inverter 13 element is lighter than ensuring a dynamic range of 120 kW for the inverter 13 alone, and the circuit design becomes easier. Further, in order to maximize the reduction amount of the leakage magnetic field, even if the power cannot be adjusted by the inverter 13, the power can be increased or decreased by the AC / DC converter 12.

Further, in general, a non-contact power feeding system transmits power by using a resonance characteristic in the vicinity of the fundamental frequency, and has an amplitude characteristic having a different amplitude for each frequency. Therefore, when frequency hopping is performed, the output power obtained at each frequency depends on the frequency amplitude characteristic, and the high frequency current received by the power receiving coil unit 21 may increase or decrease as the frequency changes, causing ripples and ripples. be.

After the output power is stable, the ripple can be identified and compensated by a method such as applying feedback control. However, in the ascending process before the output power stabilizes, it is difficult to distinguish between the increase in the output power itself and the increase / decrease fluctuation of the power due to the ripple, and the removal of the ripple requires complicated control.

Therefore, in the present embodiment, control is performed so that ripples do not occur as much as possible when the electric power is started up. Specifically, a power threshold value for starting frequency hopping is provided, and the power transmission control unit 16 instructs the drive signal output unit 14 to execute frequency hopping after the output power exceeds the power threshold value. Upon receiving the instruction, the drive signal output unit 14 outputs a drive signal for frequency hopping. As a result, frequency hopping is started.

Also. Similarly, for the control of the conduction angle, a power threshold value for starting the conduction angle control is provided, and the power transmission control unit 16 drives the drive signal so that the conduction angle is set to a predetermined value after the output power exceeds the power threshold value. You may instruct the output unit 14. If the conduction angle is fixed from the beginning, the power cannot be adjusted by the inverter 13. Therefore, even when the conduction angle is fixed to a predetermined value, the power may be adjusted until the output power exceeds the threshold value.

Rather than determining whether or not the output power exceeds the power threshold value, it may be determined using a current value or the like that has a correlation with the electric power and is easy to measure. For example, as shown in FIG. 8, the current of the inverter 13 may be input to the power transmission control unit 16, and the power transmission control unit 16 may measure the current value.

The flow of processing when controlling the start of frequency hopping and conduction angle control will be described. FIG. 9 is a diagram showing a schematic flowchart of processing in the case of controlling the start of frequency hopping and conduction angle control. FIG. 10 is a diagram showing a transition of the current of the coil unit when the start of frequency hopping and conduction angle control is controlled. Here, the current value is used for control. Further, the target current value is set to 120 A, and the power threshold value for frequency hopping is set to 60 A, which is half of the target current value. The power threshold value for the conduction angle is set to a current value of 80 A when the conduction angle is 120 degrees, assuming that the suppression of the third harmonic is maximized. Further, the initial value of the conduction angle at the start of power transmission is set to 15 degrees. These values are not particularly limited and may be changed as appropriate.

The power transmission control unit 16 instructs the drive signal output unit 14 to start power transmission (S101), and the drive signal output unit 14 starts output of the drive signal (S102). As a result, a current starts to flow from the inverter 13 to the power transmission coil unit 15. The drive signal output unit 14 changes the waveform of the drive signal so that the conduction angle continues to increase from the initial value until the current reaches the power threshold value of the conduction angle. As a result, the current value of the high frequency current continues to rise. The amount of increase in the conduction angle may be predetermined. Further, the start of frequency hopping has not been instructed by the power transmission control unit 16, and frequency hopping has not yet been performed. Therefore, no ripple occurs.

When it is detected that the current value of the high frequency current has reached the power threshold of 60A for frequency hopping, the power transmission control unit 16 instructs the drive signal output unit 14 to start frequency hopping (frequency hopping ON) (S103). According to the instruction, the drive signal output unit 14 starts changing the cycle of each drive signal at predetermined intervals (S104). As a result, frequency hopping is started. As the conduction angle continues to increase, the current continues to rise.

When it is detected that the current value of the high-frequency current reaches 80 A, which is the power threshold value for controlling the conduction angle, the power transmission control unit 16 instructs the drive signal output unit 14 to maintain the conduction angle (S105). Upon receiving the instruction, the drive signal output unit 14 adjusts the drive signal so that the conduction angle remains at 120 degrees (S106). In this way, the conduction angle is maintained.

When the conduction angle is fixed, the increase in the current due to the inverter 13 is eliminated, so that the power transmission control unit 16 controls the output power of the AC / DC converter 12 to increase (S107). As a result, the increase in the current value of the high frequency current is maintained.

When it is detected that the current value of the high frequency current has reached the target current value of 120 A, the power transmission control unit 16 controls the output power of the AC / DC converter 12 to be a constant value (S108). In this way, it is possible to obtain a current with a target current value while performing both frequency hopping and maintaining the conduction angle.

After the current value of the high frequency current reaches the target current value, the power transmission control unit 16 changes (increases or decreases) the conduction angle of the inverter 13 based on the difference between the actual value of the high frequency current and the target value. , May be instructed to the drive signal output unit 14. When the drive signal output unit receives the instruction, the drive signal output unit increases or decreases the conduction angle of the inverter in the range from M × 180 / N to (M + 2) × 180 / N in the direction in which the difference disappears. As described above, the waveform of the drive signal is changed. As a result, fluctuations in high-frequency current are suppressed, and stable power transmission can be performed.

The increase / decrease in power after reaching the target current value may be performed by the AC / DC converter 12. However, in that case, if there is a difference in time constant between the converter that controls the increase / decrease in power and the inverter 13 that controls frequency hopping, even if both controls are synchronized, the response will be different due to the difference in time constant. It ends up. Further, since the time constant changes according to the temperature change of the device, the state of the coil, etc., it is necessary to perform control in consideration of the time constant that changes from moment to moment for stabilization. Therefore, after the output power reaches the target power, it is preferable to adjust the power value by controlling the conduction angle without the AC / DC converter 12. Further, if the target current value cannot be maintained unless the conduction angle is set outside the permissible range, the AC / DC converter 12 may be used, and in other cases, the power value may be adjusted by controlling the conduction angle. ..

As described above, according to the second embodiment, the power transmission control unit 16 can determine the implementation period of frequency hopping and control of the conduction angle according to the electric power and the like. As a result, it is possible to prevent the occurrence of ripple at the time of starting up the electric power.

It is assumed that each process of the present embodiment is realized by a dedicated circuit, but the CPU executes a program stored in the memory for the process related to the circuit control such as the specification of the timing to change the frequency. It may be realized by doing.

Although one embodiment of the present invention has been described above, these embodiments are presented as examples and are not intended to limit the scope of the invention. These novel embodiments can be implemented in various other embodiments, and various omissions, replacements, and changes can be made without departing from the gist of the invention. These embodiments and variations thereof are included in the scope and gist of the invention, and are also included in the scope of the invention described in the claims and the equivalent scope thereof.

1 Power transmission device 11 AC power supply 12 AC / DC converter 13 Inverter 14 Drive signal output unit 15 Power transmission coil unit (resonator)
16 Power transmission control unit 17 DC / DC converter 18 Power transmission side notch filter 2 Power receiving device 21 Power receiving coil unit (resonator)
22 Rectifier 23 Notch filter on the power receiving side

Claims (15)

A power transmission device that transmits electric power by a magnetic field.
Inverters that generate high-frequency current from direct current and
A drive signal output unit that outputs a drive signal for driving the inverter,
A power transmission coil that generates the magnetic field when the high-frequency current flows,
Equipped with
The inverter periodically changes the frequency of the high frequency current based on the drive signal.
A power transmission device in which the inverter changes the waveform of the high-frequency current based on the drive signal so that the conduction angle before the frequency of the high-frequency current is changed and the conduction angle after the change are constant . By periodically changing the frequency of the drive signal by the drive signal output unit, the frequency of the high frequency current is periodically changed.
The power transmission device according to claim 1, wherein the drive signal output unit changes the waveform of the high-frequency current by changing the duty ratio of the drive signal. By periodically changing the frequency of the drive signal by the drive signal output unit, the frequency of the high frequency current is periodically changed.
The power transmission device according to claim 1, wherein the drive signal output unit changes the waveform of the high-frequency current by changing the phase difference of the drive signal. When N is defined as an odd number,
Claim 1 to reduce the leakage magnetic field of the Nth harmonic by maintaining the conduction angle of the inverter at an angle of 180 × (N-1) / N before and after the frequency of the high frequency current is changed. Or the power transmission device according to any one of 3. Any one of claims 1 to 3 in which the third harmonic of the magnetic field is reduced by maintaining the conduction angle of the inverter at around 120 degrees before and after the frequency of the high frequency current is changed. The power transmission device described in. The inverter is a single-phase full-bridge inverter composed of first to fourth switching elements.
The first switching element and the second switching element are connected in series to form a first leg.
The third switching element and the fourth switching element are connected in series to form a second leg.
A connection node between the first switching element and the second switching element is connected to one end of the power transmission coil .
A connection node between the third switching element and the fourth switching element is connected to the other end of the power transmission coil .
The direct current is input to one end of the first switching element that is not connected to the second switching element and one end of the third switching element that is not connected to the fourth switching element.
The power transmission according to any one of claims 1 to 5, wherein the high frequency current is generated from the direct current by switching based on the drive signals corresponding to the first to fourth switching elements. Device. The first drive signal for the first switching element is a signal obtained by inverting the second drive signal for the second switching element.
The third drive signal for the third switching element is a signal obtained by inverting the fourth drive signal for the fourth switching element.
The power transmission device according to claim 6, wherein the drive signal output unit adjusts the conduction angle of the inverter by changing the difference in the duty ratio between the first drive signal and the third drive signal. The first drive signal for the first switching element is a signal obtained by inverting the second drive signal for the second switching element.
The third drive signal for the third switching element is a signal obtained by inverting the fourth drive signal for the fourth switching element.
The power transmission device according to claim 6, wherein the drive signal output unit adjusts the conduction angle of the inverter by changing the phase difference between the first drive signal and the third drive signal. Further provided with a power transmission control unit that instructs the drive signal output unit to start or stop at least one of the periodic change of the frequency of the high frequency current and the change of the waveform of the high frequency current based on the high frequency current. ,
The drive signal output unit outputs a drive signal having a frequency or a waveform according to the content of the instruction, whereby the frequency of the high-frequency current is periodically changed by the inverter and the waveform of the high-frequency current is changed. The power transmission device according to any one of claims 1 to 8, wherein at least one of the above is started or stopped. When the transmission control unit detects that the value of the high-frequency current has reached the first threshold value, the drive signal output unit is instructed to start periodically changing the frequency of the high-frequency current. The power transmission device according to claim 9, wherein the drive signal output unit starts changing the cycle of the drive signal at a predetermined timing after receiving the start instruction. When the power transmission control unit detects that the value of the high frequency current has reached the second threshold value, the drive signal output unit is instructed to stop changing the waveform of the high frequency current.
The power transmission device according to claim 9 or 10, wherein the waveform of the drive signal is changed so that the conduction angle of the inverter is continuously increased until the drive signal output unit receives the stop instruction. When N is defined as an odd number and M is defined as an odd number less than N, the conduction angle of the inverter is set within the range from M × 180 / N to (M + 2) × 180 / N in the drive signal output unit. The power transmission device according to any one of claims 9 to 11, wherein the waveform of the drive signal is changed. When N is defined as an odd number and M is defined as an odd number less than N, the power transmission control unit determines the conduction angle of the inverter with respect to the drive signal output unit based on the difference between the high frequency current value and the target value. Instruct to increase or decrease
When the drive signal output unit receives the increase / decrease instruction, the conduction angle of the inverter is increased or increased in the direction in which the difference disappears within the range from M × 180 / N to (M + 2) × 180 / N. The power transmission device according to any one of claims 9 to 11, wherein the waveform of the drive signal is changed so as to decrease. Further provided with a DC power supply generator for generating the DC current,
The power transmission device according to any one of claims 9 to 13, wherein the power transmission control unit instructs the DC power generation unit to increase or decrease the voltage of the DC current. It is a power transmission system that is equipped with a power transmission device and a power receiving device and transmits power in a non-contact manner.
The power transmission device
Inverters that generate high-frequency current from direct current and
A drive signal output unit that outputs a drive signal for driving the inverter,
A power transmission coil that generates a magnetic field due to the flow of the high-frequency current,
Equipped with
The power receiving device is
A power receiving coil unit that generates a high-frequency current from the magnetic field is provided.
The inverter periodically changes the frequency of the high frequency current of the inverter based on the drive signal.
Power transmission in which the inverter changes the waveform of the high-frequency current of the inverter based on the drive signal so that the conduction angle before the frequency of the high-frequency current is changed and the conduction angle after the change are constant. system.

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