JP2022069069A - Magnetic field resonance power supply device - Google Patents

Abstract

To provide a magnetic field resonance power supply device capable of suppressing reduction in transmission efficiency at a low load.SOLUTION: A magnetic field resonance power supply device includes: a first power supply unit 110 having a first transmission coil L1, a first resonance capacitor C1, a first switching element Q1, and a first diode D1; a second power supply unit 120 having a second transmission coil L2, a second resonance capacitor C2, a second switching element Q2, and a second diode D2; a phase shift control circuit (142, 144, 145) for controlling a first phase shift time that is time difference between turn-off of the first switching element Q1 and turn-off of the second switching element Q2 according to a power value of transmission power; and an on-time control circuit (132, 133) for controlling turn-off of the first switching element Q1 so as to shorten an on-time of the first switching element Q1 when the power value of the transmission power decreases.SELECTED DRAWING: Figure 1

Description

The present invention relates to a magnetic field resonance power supply device that performs power transmission using magnetic field resonance.

As a magnetic field resonance power supply device that performs power transmission using magnetic field resonance, for example, in the case of a wireless charger having a non-contact transmission coil, it is possible to supply a non-contact transmission power of about several kilowatts to an electric vehicle. .. In this magnetic field resonance power supply device, it has been proposed that the power transmission side power supply unit and the power reception side power supply unit are each composed of a single endd converter that operates with a single switching element, and the transmission power is controlled by phase shift control. (For example, see Patent Document 1).

By performing phase shift control, it is not necessary to perform voltage control in the front stage of the power transmission side power supply unit and the rear stage of the power reception side power supply unit. As a result, a DC / DC converter (for example, a buck-boost chopper circuit) provided in the front stage of the power transmission side power supply unit and the rear stage of the power reception side power supply unit is not required, so that the cost of the entire power supply device can be reduced.

However, there is a problem that the transmission efficiency of the transmission power is greatly lowered when the load is low by performing the phase shift control. For example, as the load decreases to 3 [kW] and 1.5 [kW] with respect to the rated load of 6 [kW], the transmission efficiency decreases to 81% and 50%.

In the magnetic resonance power supply device described in Patent Document 1, a very large resonance current is generated between the resonance capacitor and the transmission coil of the power feeding unit on the transmission side and between the resonance capacitor and the transmission coil of the power supply unit on the power receiving side regardless of the transmission power. It flows as an invalid current. When this resonance current flows through the resonance circuit including the resonance capacitor and the transmission coil, a loss occurs as heat due to the resistance component of the resonance circuit. For example, if the resonance current is 80 [A] and the resistance of the resonance circuit is 50 [mΩ], a loss of 320 [W] occurs, and if the transmission power is 6 [kW], the loss is about 5%. When the output voltage is 350 [V], the active current is 17 [A] when the transmission power is 6 [kW], so that the resonant current, which is the reactive current, is about 5 times the active current.

Moreover, since the magnitude of the resonance current is irrelevant to the magnitude of the load, the influence of the loss of the resonance current becomes large at the time of low load when the transmission power becomes small. For example, when the transmission power is 1.5 [kW], the loss is about 21%. Since the active current at this time is 3 [A], the resonant current, which is the reactive current, is about 27 times the active current. As described above, when the load is low, the influence of the loss of the resonance current becomes larger, and there is a problem that the transmission efficiency is greatly lowered. Further, when the resonance current flows through the transmission coil, there is a problem that abnormal heat generation is generated in the transmission coil due to the influence of the proximity effect, which causes a problem that cost is required for countermeasures.

In addition, Patent Document 2 proposes a method of improving the transmission efficiency of transmission power by controlling the frequency so as to increase the effective current on the primary side. However, when phase shift control is performed as in the magnetic field resonance power supply device, the magnitude of the resonance current does not change even if the frequency is changed by the method described in Patent Document 2 to increase the effective current, so that the load is low. It is not possible to suppress the decrease in transmission efficiency over time.

Japanese Unexamined Patent Publication No. 2020-7823 Japanese Unexamined Patent Publication No. 2013-17256

The present invention has been made in view of the above circumstances, and an object thereof is to provide a magnetic field resonance power supply device capable of suppressing a decrease in transmission efficiency at a low load.

In order to solve the above problems, the magnetic field resonance power supply device according to the embodiment of the present invention is
A first feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element.
A second feeding unit including a second transmission coil, a second resonant capacitor, a second switching element, and a second diode connected in parallel to the second switching element.
With a control unit,
A magnetic field resonance power supply device that supplies transmission power from the first feeding unit to the second feeding unit by magnetic field resonance.
The control unit
A phase shift control circuit that controls the first phase shift time, which is the time difference between the turn-off of the first switching element and the turn-off of the second switching element, according to the power value of the transmission power.
An on-time control circuit that controls the on-time of the first switching element by controlling the turn-off of the first switching element according to the power value of the transmission power.
It is characterized by having.

According to this configuration, the on-time of the first switching element is controlled by controlling the turn-off of the first switching element according to the power value of the transmission power, so that the first switching element is turned on when the transmission power becomes small. The resonance current can be reduced by shortening the time. As a result, it is possible to suppress an increase in loss due to the influence of the resonance current at a low load when the transmission power becomes small, and it is possible to suppress a large decrease in transmission efficiency.

Further, in order to solve the above problems, the magnetic field resonance power supply device according to another embodiment of the present invention is provided.
A first feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element.
A second feeding unit including a second transmission coil, a second resonant capacitor, and a second diode,
With a control unit,
A magnetic field resonance power supply device that supplies transmission power from the first feeding unit to the second feeding unit by magnetic field resonance.
The second diode is turned off after the lapse of the first phase shift time, which is a predetermined time difference from the turn-off of the first switching element due to the magnetic field resonance.
The control unit
It is characterized by comprising an on-time control circuit for controlling the on-time of the first switching element by controlling the turn-off of the first switching element according to the power value of the transmission power.

According to this configuration, the on-time of the first switching element is controlled by controlling the turn-off of the first switching element according to the power value of the transmission power, so that the first switching element is turned on when the transmission power becomes small. The resonance current can be reduced by shortening the time. As a result, it is possible to suppress an increase in loss due to the influence of the resonance current at a low load when the transmission power becomes small, and it is possible to suppress a large decrease in transmission efficiency.

In the above magnetic field resonance power supply device
The on-time control circuit is
The first arithmetic processing for calculating the phase margin time, which is the difference between the maximum phase shift time, which is the time difference at the time of the maximum transmission power at which the transmission power is maximum, and the first phase shift time,
A second arithmetic process for calculating the first on-time, which is the difference between the maximum on-time, which is the on-time of the first switching element at the time of the maximum transmission power, and the phase margin time, is performed.
The first switching element can be configured to be turned off after the first on time has elapsed since the first switching element was turned on.

In the above magnetic field resonance power supply device
The control unit
A current detection circuit that detects the current value of the current flowing through the second transmission coil, and
A zero-cross detection circuit that outputs a zero-cross signal at the timing when the zero-cross point when the current value changes from negative to positive is detected.
Further prepare
The on-time control circuit is
The first switching element can be configured to be turned off at the timing when the zero cross signal is input.

In the above magnetic field resonance power supply device
The on-time control circuit has data showing the relationship between the transmission power and the on-time of the first switching element, and can be configured to determine the turn-off timing of the first switching element based on the data.

In the above magnetic field resonance power supply device
In the data, when the transmission power is from the maximum value to a predetermined first threshold value, the on-time of the first switching element becomes shorter as the transmission power becomes smaller, while the transmission power is smaller than the first threshold value. May indicate a relationship in which the on-time of the first switching element becomes a constant value.

In the above magnetic field resonance power supply device
When the transmission power is equal to or higher than a predetermined second threshold value, the on-time control circuit controls the turn-off of the first switching element so that the on-time of the first switching element becomes shorter as the transmission power becomes smaller. On the other hand, when the transmission power is smaller than the second threshold value, the turn-off of the first switching element can be controlled so that the on time of the first switching element becomes a constant value.

According to the present invention, it is possible to provide a magnetic field resonance power supply device capable of suppressing a decrease in transmission efficiency at a low load.

It is a figure which shows the magnetic field resonance power supply device which concerns on 1st Embodiment. It is a timing chart of each part of the magnetic field resonance power supply device which concerns on a comparative example. It is a figure which shows the current path in each operation mode (modes 1 and 2) of the magnetic field resonance power supply device which concerns on a comparative example. It is a figure which shows the current path in each operation mode (modes 3 and 4) of the magnetic field resonance power supply device which concerns on a comparative example. It is a timing chart of each part of the magnetic field resonance power supply device which concerns on 1st Embodiment. It is a figure which shows the magnetic field resonance power supply device which concerns on 2nd Embodiment. It is a timing chart of each part of the magnetic field resonance power supply device which concerns on 2nd Embodiment. It is a figure which shows the magnetic field resonance power supply device which concerns on 3rd Embodiment. It is a timing chart of each part of the magnetic field resonance power supply device which concerns on 3rd Embodiment. It is a figure which shows the magnetic field resonance power supply device which concerns on 4th Embodiment. It is a figure which shows the relationship between the transmission power (the signal value of a reference voltage signal), and the on time (the first on time) of a 1st switching element.

Hereinafter, embodiments of the magnetic field resonance power supply device according to the present invention will be described with reference to the accompanying drawings.

[First Embodiment]
FIG. 1 shows a magnetic field resonance power supply device 100A according to the first embodiment of the present invention. The magnetic field resonance power supply device 100A includes a first power supply unit 110 connected to the first power supply unit E ₁ , a second power supply unit 120 connected to the second power supply unit E ₂ , a first control unit 130, and a second. A control unit 140 is provided. The first control unit 130 and the second control unit 140 correspond to the "control unit" of the present invention.

The first power feeding unit 110 and the first control unit 130 are installed in, for example, a home. The second power feeding unit 120 and the second control unit 140 are mounted on, for example, an electric vehicle such as an electric vehicle or a plug-in hybrid vehicle. The magnetic field resonance power supply device 100A supplies transmission power from the first feeding unit 110 to the second feeding unit 120 by magnetic field resonance (synonymous with magnetic field resonance, magnetic resonance, magnetic resonance).

The first power supply unit E ₁ is a DC power supply, and the first power supply unit E ₁ is, for example, a DC output of an AC / DC converter (AC / DC conversion power supply) connected to a power system or a storage battery installed at home. This is the DC output of the connected DC / DC converter. An LC filter circuit including a coil and a capacitor may be provided between the first power supply unit E ₁ and the first power supply unit 110.

The second power supply unit E ₂ is, for example, a storage battery or a load mounted on an electric vehicle. An LC filter circuit including a coil and a capacitor may be provided between the second power supply unit E ₂ and the second power supply unit 120.

The first feeding unit 110 is a single-ended converter (one-stone converter) including a first transmission coil L ₁ , a first resonance capacitor C ₁ , and a first switch SW ₁ . The first switch SW ₁ includes a first switching element Q ₁ and a first diode D ₁ connected in parallel to the first switching element Q ₁ in the opposite direction.

One end of the first transmission coil L ₁ is connected to the high potential side of the first power supply unit E ₁ , and the other end is connected to the low potential side of the first power supply unit E ₁ via the current path of the first switching element Q ₁ . Be connected. The first resonance capacitor C ₁ is connected in parallel to at least one of the first transmission coil L ₁ and the first switch SW ₁ (in this embodiment, the first transmission coil L ₁ ).

Although the first switching element Q ₁ uses an IGBT (insulated gate transistor), a semiconductor switching element for power such as a MOSFET (metal oxide semiconductor type field effect transistor), a bipolar transistor, or a SiC (silicon carbide) semiconductor can be used. You may use it. The first diode D ₁ is a built-in (parasitic) diode of the first switching element Q ₁ or an external diode independent of the first switching element Q ₁ . The connection relationship between the first switching element Q ₁ and the first diode D ₁ can be appropriately changed according to the capacity and transmission power of each element.

The second feeding unit 120 is a single-ended converter (one-stone converter) including a second transmission coil L ₂ , a second resonance capacitor C ₂ , and a second switch SW ₂ . The second switch SW ₂ includes a second switching element Q ₂ and a second diode D ₂ connected in parallel to the second switching element Q ₂ in the opposite direction. Since the configuration of the second feeding unit 120 is the same as the configuration of the first feeding unit 110, detailed description of the configuration will be omitted.

The first control unit 130 includes a first resonance voltage detection circuit 131, a first synchronization circuit 132, a turn-off control circuit 133, and a first communication circuit 134. In the present embodiment, the first synchronization circuit 132 and the turn-off control circuit 133 correspond to the "on-time control circuit" of the present invention.

The second control unit 140 includes a second resonance voltage detection circuit 141, a second synchronization circuit 142, a power detection circuit 143, a comparison circuit 144, a phase difference control circuit 145, and a second communication circuit 146. In the present embodiment, the second synchronization circuit 142, the comparison circuit 144, and the phase difference control circuit 145 correspond to the "phase shift control circuit" of the present invention.

The first resonance voltage detection circuit 131 measures the voltage V _R1 across the first transmission coil L ₁ (first resonance capacitor C ₁ ), so that the first transmission coil L ₁ and the first resonance capacitor C ₁ can be used for the first. Obtain the voltage value of the resonance voltage. The first resonance voltage detection circuit 131 outputs a detection signal corresponding to the voltage value of the first resonance voltage to the first synchronization circuit 132.

The first synchronization circuit 132 controls the turn-on / turn-off of the _first switching element Q1. The first synchronization circuit 132 controls the turn-on of the first switching element Q ₁ in synchronization with the first resonance voltage so that the first switching element Q ₁ performs a zero voltage switching operation. Further, the first synchronization circuit 132 controls the turn-off of the _first switching element Q1 based on the on-time control signal from the turn-off control circuit 133.

The turn-off control circuit 133 is a first switching element so that the on-time of the _first switching element Q1 becomes shorter when the power value of the transmission power becomes smaller due to the information regarding the phase shift time notified from the second control unit 140 described later. Generates an on-time control signal to control the turn-off of _Q1 . Specifically, the turn-off control circuit 133 performs a first arithmetic process for calculating the phase margin time and a second arithmetic process for calculating the first on-time to generate an on-time control signal.

In the first arithmetic processing, the turn-off control circuit 133 has the "first phase shift time", which is the time difference between the turn-off of the first switching element Q ₁ and the turn-off of the second switching element Q ₂ , and the maximum transmission power. The difference (= phase margin time) from the "maximum phase shift time", which is the time difference at the time of transmission power, is calculated. That is, the phase margin time is set as the absolute value of the difference between the maximum phase shift time and the first phase shift time.
Phase margin time = | Maximum phase shift time-First phase shift time |
It can be expressed as.

The turn-off control circuit 133 acquires a signal regarding the first phase shift time from the second control unit 140. Further, the turn-off control circuit 133 stores the maximum phase shift time in advance. The maximum transmission power and the maximum phase shift time are determined by, for example, the specifications of the magnetic field resonance power supply device 100A.

In the second arithmetic processing, the turn-off control circuit 133 calculates the first on-time, which is the difference between the "maximum on-time", which is the on-time of the _first switching element Q1 at the time of maximum transmission power, and the "phase margin time". Then, an on-time control signal for the first on-time is generated. The turn-off control circuit 133 stores the maximum on-time in advance. The maximum on-time is determined by, for example, the specifications of the magnetic field resonance power supply device 100A, and is a time during which the maximum phase shift time can be secured.

The turn-off control circuit 133 outputs the generated on-time control signal to the first synchronization circuit 132. The first synchronization circuit 132 turns off the first switching element Q1 at the timing when the first on time has elapsed from the turn-on of the _first switching element _Q1 based on the on-time control signal. Further, the first synchronization circuit 132 transmits a first timing signal regarding the timing for turning off the first switching element Q ₁ to the second control unit 140 via the first communication circuit 134.

The first communication circuit 134 is configured to transmit and receive a predetermined signal by light or radio waves to and from the second communication circuit 146. The first communication circuit 134 can be composed of, for example, a light emitting diode for transmission and a phototransistor for reception.

The second resonance voltage detection circuit 141 measures the voltage V _R2 across the second transmission coil L ₂ (second resonance capacitor C ₂ ), so that the second transmission coil L ₂ and the second resonance capacitor C ₂ provide a second voltage. Obtain the voltage value of the resonance voltage. The second resonance voltage detection circuit 141 outputs a detection signal corresponding to the voltage value of the second resonance voltage to the second synchronization circuit 142.

The second synchronization circuit 142 controls the turn-on / turn-off of the _second switching element Q2. The second synchronization circuit 142 controls the turn-on of the second switching element Q ₂ in synchronization with the second resonance voltage so that the second switching element Q ₂ performs the zero voltage switching operation. Further, the second synchronization circuit 142 controls the turn-off of the _second switching element Q2 based on the second timing signal from the phase difference control circuit 145.

The power detection circuit 143 measures the current and voltage flowing between the second power supply unit 120 and the _second power supply unit E2 to measure the transmission power supplied from the first power supply unit 110 to the second power supply unit 120. The power value is acquired, and a signal (for example, a voltage signal) corresponding to the power value is output to the comparison circuit 144. The transmission power supplied from the first power supply unit 110 to the second power supply unit 120 has a predetermined relationship with the current and voltage flowing between the second power supply unit 120 and the _second power supply unit E2.

The comparison circuit 144 compares the power value of the transmission power acquired by the power detection circuit 143 with a predetermined target value, and outputs a difference signal corresponding to the difference between the power value and the target value to the phase difference control circuit 145. In the present embodiment, the comparison circuit 144 is composed of a differential amplifier, a reference voltage signal Vref corresponding to a target value of transmission power is input to the inverting input terminal of the differential amplifier, and power is input to the non-inverting input terminal of the differential amplifier. The signal from the detection circuit 143 is input, and the difference signal is output from the output terminal of the differential amplifier.

The phase difference control circuit 145 turns off the _first switching element Q1 and the _second switching element Q2 so that the power value of the transmission power approaches the target value based on the difference signal input from the comparison circuit 144. The first phase shift time, which is the time difference from the turn-off of, is calculated. The phase difference control circuit 145 transmits a signal relating to the first phase shift time to the turn-off control circuit 133 via the second communication circuit 146 and the first communication circuit 134. The relationship between the power value of the transmission power and the first phase shift time can be clarified by measuring in advance, and the target value can be calculated by storing the relationship.

Further, the phase difference control circuit 145 includes a first timing signal relating to a timing for turning off the _first switching element Q1 received from the first synchronization circuit 132 via the first communication circuit 134 and the second communication circuit 146, and the above-mentioned first timing signal. The second timing for turning off the _second switching element Q2 is determined based on the first phase shift time, and the second timing signal is output to the second synchronization circuit 142. The second synchronization circuit 142 turns off the _second switching element Q2 based on the second timing signal.

The second communication circuit 146 is configured to transmit and receive a predetermined signal by light or radio waves to and from the first communication circuit 134. The second communication circuit 146 can be composed of, for example, a light emitting diode for transmission and a phototransistor for reception.

Next, the operation of the magnetic field resonance power supply device 100A will be described with reference to FIGS. 2 to 5. However, FIGS. 2 to 4 relate to a magnetic field resonance power supply device (hereinafter, referred to as “comparative example”) according to a comparative example for explaining the conventional operation.

The comparative example has the configuration described in Patent Document 1, and is different in that the magnetic field resonance power supply device 100A according to the present embodiment does not have the turn-off control circuit 133. The first synchronization circuit 132 of the comparative example turns on the first switching element _Q1 and then turns off the _first switching element Q1 after the preset on-time _Ton1 has elapsed. Therefore, in the comparative example, the on-time _Ton1 of the _first switching element Q1 is constant regardless of the power value of the transmission power. The other operations of the comparative example are the same as the operations of the magnetic field resonance power supply device 100A according to the present embodiment.

In FIG. 2, (A) is the waveform of the voltage V _SW1 across the _first switch SW ₁ , (B) is the waveform of the current I _SW1 flowing through the first switch SW ₁ , and (C) is the waveform of the current I SW1 flowing through the first switch SW 1. The waveform of the voltage V _R1 , (D) is the waveform of the gate voltage V _g1 of the _first switching element Q1, (E) is the waveform of the gate voltage V _g2 of the _second switching element Q2, and (F) is the second transmission coil. _{The waveform} of the voltage _{V R2 across} L ₂ ; _The waveform of the current IL1 flowing through the transmission coil _L1 and (J) are the waveforms of the current IL2 flowing through the _second transmission coil _L2 .

During the period when the first switch SW ₁ is off T _OFF 1, a first resonance voltage (voltage V _R1 ) is generated by the first transmission coil L ₁ and the first resonance capacitor C ₁ at both ends of the first transmission coil L ₁ . .. When the first resonance voltage detection _circuit 131 detects a zero cross point t ₀ at which the voltage VR1 intersects zero, the first synchronization circuit 132 synchronizes with the zero cross point t ₀ (a predetermined synchronization time elapses from the zero cross point t ₀ ). At time t2, the gate voltage _Vg1 of the _first switching element _Q1 is switched from the low level to the high level, and the first switching element _Q1 is turned on by the zero voltage switching operation.

In the period T _{OFF 1} , the voltage V _SW1 across the first switch SW1 draws a resonance arc, rises slowly, then falls slowly to reach zero. When the voltage V _SW 1 reaches zero at time t ₁ , the first diode D ₁ is automatically turned on, and the first switch SW ₁ is turned on (conducting state).

During the period when the first switch _{SW 1} is ON, the DC voltage of the first power supply unit E ₁ is applied to the first transmission coil L ₁ , so that the current I _{SW 1} flowing through the first switch SW 1 is It increases linearly. When the current I _SW 1 is commutated from negative to positive, the current flowing through the first diode D ₁ smoothly flows to the first switching element Q ₁ , and the on state of the first switch SW ₁ continues.

The first synchronization circuit 132 switches the gate voltage V _g1 of the _first switching element Q1 from the high level to the low level at the time t ₆ when the on time _{Ton 1} of the preset fixed period has elapsed from the time t ₂ . , The first switching element _Q1 is turned off. As a result, the first switch SW ₁ is turned off (cut-off state), and the current stored in the first transmission coil L ₁ flows into the first resonance capacitor C ₁ to be in a resonance state. The on-time _{Ton1 is set to a time (maximum on-time) in which the maximum phase shift time T ΦM can} be secured.

During the period T _OFF 2 when the second switch SW ₂ is off, a second resonance voltage (voltage VR ₂ ) is generated by the second transmission coil L ₂ and the second resonance capacitor C ₂ at both ends of the second transmission coil L ₂ . .. When the second resonance voltage detection circuit 141 detects the zero cross point t ₃ at which the voltage VR ₂ intersects zero, the second synchronization circuit 142 synchronizes with the zero cross point t ₃ (a predetermined synchronization time elapses from the zero cross point t ₃ ). _At time t5, the gate voltage _Vg2 of the _second switching element Q2 is switched from the low level to the high level, and the _second switching element Q2 is turned on by the zero voltage switching operation.

In the period T _OFF 2, the voltage across the second switch SW ₂ V _SW 2 draws a resonance arc, rises slowly, and then slowly falls to reach zero. When the voltage V _SW2 reaches zero at time t4, the _second diode D2 automatically turns on and the _second switch SW2 turns _on (conducting state).

During the period when the second switch SW ₂ is _ON , the energy stored in the second transmission coil L ₂ is supplied to the second power supply unit E ₂ through the second switch SW ₂ , so that the second switch SW 2 is switched on. The current I _SW2 flowing through ₂ increases linearly. When the current I _SW2 commutates from negative to positive, the current flowing through the second diode D ₂ smoothly flows to the second switching element Q ₂ , and the on state of the second switch SW ₂ continues.

When the first switching element _Q1 is turned off at time _t6 , the first timing signal is sent from the first synchronization circuit 132 to the phase difference control circuit 145. The phase difference control circuit 145 calculates the first phase shift time T _Φ and synchronizes the second timing signal with the second timing signal at a time t ₇ delayed by the first phase shift time T _Φ from the time t ₆ of the first timing signal. Output to circuit 142. The second synchronization circuit 142 _changes the gate voltage _Vg2 of the _second switching element Q2 from high level to low level at time _{t7, which is delayed by the first phase shift time TΦ from} time t6 according to the second timing signal. It is switched to turn off the _second switching element Q2. As a result, the second switch SW ₂ is turned off (cutoff state), and the current stored in the second transmission coil L ₂ flows into the second resonance capacitor C ₂ to be in a resonance state.

By the above operation, the first switching element Q ₁ and the second switching element Q ₂ maintain the zero voltage switching with a small switching loss, and the turn-off phase of the second switching element Q ₂ is changed to the turn-off of the first switching element Q ₁ . It can be shifted by the time T _Φ (only Φ = 2πT _Φ / To (To: operation cycle) at the phase angle Φ) from the phase of.

In FIGS. 3 and ₄ , the time t1 to t4 shown in FIG. ₂ is the mode ₁ period, the time t4 to t6 is the mode ₂ period, the time t6 to _t7 is the mode ₃ period, and the time t. It is a figure which shows typically the current flowing through the 1st feeding part 110 and the 2nd feeding part 120 in each mode period when the time between ₇ and t ₈ is a mode 4 period. However, FIG. 3B shows a period (between time t ₅₁ and t ₅₂ ) in which the current _IL1 is positive and the current _IL2 is negative in the mode 2 period. FIG. 4B shows a period in which the current _IL1 is negative and the current _IL2 is positive in the mode 4 period.

At time t1, when the voltage V _SW1 reaches zero, the mode ₁ period starts. In the first feeding unit 110 during the mode 1 period shown in FIG. 3A, the first diode D ₁ is turned on and the first switch SW ₁ is turned on, and the negative current flowing through the first transmission coil L ₁ is turned on. Flows to the first switch SW ₁ and returns to the first power supply unit E ₁ . At time t2, the _first switching element _Q1 is turned on, and the DC voltage of the _first power supply unit E1 is applied to the _first transmission coil L1. Therefore, the current I _SW1 and the current _IL1 increase linearly. In the second feeding unit 120 during the mode 1 period, since the second switch SW ₂ is turned off and becomes a resonance state, the current I _SW 2 does not flow, and the current IL 2 gradually increases after _reaching a negative peak.

At time t4, when the voltage V _SW2 reaches zero, the mode ₂ period starts. In the first feeding unit 110 of the mode 2 period, the current I _SW1 and the current _IL1 increase linearly as in the mode 1 period. In the second feeding unit 120 during the mode 2 period, the second diode D ₂ is turned on and the second switch SW ₂ is turned on, and the energy stored in the second transmission coil L ₂ is passed through the second switch SW ₂ . 2 It is supplied to the power supply unit E ₂ . Therefore, the current I _SW2 and the current _IL2 increase linearly. Of the mode 2 periods, the length of the period (between times t ₅₁ and t ₅₂ ) that contributes to power transmission shown in FIG. 3B coincides with the length of the first phase shift time T _Φ .

At time t6, when the first switching element _Q1 is turned off, the mode ₃ period starts. As shown in FIG. 4A, in the first feeding unit 110 during the mode 3 period, the first switch SW ₁ is turned off, and the current stored in the first transmission coil L ₁ is the first resonance capacitor C. It flows into ₁ and becomes a resonance state. The current _IL1 is a resonance current, which reaches a positive peak and then gradually decreases. In the second feeding unit 120 during the mode 3 period, the current I _SW2 and the current IL 2 increase _linearly as in the mode 2 period.

At time _t7 , when the second switching element _Q2 is turned off, the mode 4 period starts. As shown in FIG. 4B, in the second feeding unit 120 during the mode 4 period, the second switch SW ₂ is turned off, and the current stored in the second transmission coil L ₂ is the second resonance capacitor C. It flows into ₂ and becomes a resonance state. Therefore, the current I _SW2 does not flow, and the current IL 2 _reaches a positive peak and then gradually decreases. In the first power feeding unit 110 during the mode 4 period, since the first switch SW ₁ remains in the resonance state in the off state, the current I _SW 1 does not flow, and the current IL ₁ gradually increases after reaching a negative peak. .. When the voltage V _SW1 reaches zero at time t8, the mode ₄ period ends and the mode 1 period starts again.

In this way, the peak value of the current _IL1 is not determined by the transmission power, that is, the first phase shift time T _Φ , but by the maximum transmission power, that is, the maximum phase shift time T _ΦM , in other words, the maximum phase shift time T _ΦM . It is determined by the on-time _Ton1 which is the time that can be secured. Therefore, in the comparative example, for example, when the load of the second power supply unit E ₂ is low and the load is low, the current _IL1 which is the resonance current becomes a large reactive current which is not necessary for the second power supply unit E ₂ . Further, since the peak value of the current _IL2 also depends on the on-time _Ton1 , the current _IL2 which is a resonance current becomes a large reactive current which is not necessary when the load is low.

FIG. 5 is a timing chart of each part of the magnetic field resonance power supply device 100A according to the present embodiment. The signals (A) to (J) of each part in FIG. 5 are the same as the signals (A) to (J) of each part in FIG. Further, the modes 1 to 4 in FIG. 5 are the same as the modes 1 to 4 in FIG. Therefore, the description of the part of the operation of the magnetic field resonance power supply device 100A that is common to the comparative example will be omitted.

In the magnetic field resonance power supply device 100A, when the power value of the transmission power is small and the load is low, the turn-off control circuit 133 uses the first switching element Q according to the power value so that the on-time of the first switching element Q ₁ is shortened. An on-time control signal for controlling the on-time of ₁ is generated.

Specifically, the turn-off control circuit 133 calculates the phase margin time as the absolute value of the difference between the maximum phase shift time T _ΦM and the first phase shift time T _Φ (first arithmetic processing), and the maximum on-time _Ton1 The first on-time _Ton1 ', which is the difference between the phase margin time and the phase margin time, is calculated to generate an on-time control signal for the first on-time _Ton1 '(second arithmetic processing).

The first synchronization circuit 132 turns off the first switching element _Q1 at the time t ₆₁ when the first on time _{Ton 1'elapses} from the time t ₂ based on the on time control signal. Therefore, the first on-time _Ton1'is shorter than the on-time _Ton1 (= maximum on-time _Ton1 ) of the comparative example.

When the first switching element _Q1 is turned off at time t ₆₁ , the first timing signal is sent from the first synchronization circuit 132 to the phase difference control circuit 145. The phase difference control circuit 145 outputs the first timing signal and the second timing signal generated based on the first phase shift time T _Φ to the second synchronization circuit 142. The second synchronization circuit 142 turns off the _second switching element Q2 at the time t ₇₁ , which is delayed by the first phase shift time T _Φ from the time t ₆₁ according to the second timing signal. Therefore, the second on-time _Ton2 ', which is the on-time of the _second switching element Q2, is shorter than the on-time _Ton2 of the comparative example.

When the first on-time _Ton1'and the second on-time _Ton2'are shortened, the peak values of the current I _SW1 and the current I _SW2 become smaller, and the peak values of the currents _IL1 and the current _IL2 also become smaller.

That is, since the phase shift time (first phase shift time T _Φ ) of the magnetic field resonance power supply device 100A in the case of FIG. 5 is the same as that of the comparative example, the power value of the transmission power is the same as that of the comparative example, but the resonance occurs. Since the magnitude of the peak value of the current (current IL1 and current _IL2 ) is smaller than that of the comparative example, the first transmission coil _L1 and the _first resonance capacitor C1 and the _second transmission coil L2 and the _second resonance capacitor C are used. The loss at the resistance component of ₂ is smaller than that of the comparative example.

Therefore, the magnetic field resonance power supply device 100A can suppress a large loss due to the resistance component of the resonance circuit due to the influence of the resonance current at a low load when the transmission power becomes small, and can suppress a large decrease in the transmission efficiency. Further, the magnetic field resonance power supply device 100A generates heat from the first transmission coil L ₁ and the first resonance capacitor C ₁ and the second transmission coil L ₂ and the second resonance capacitor C ₂ due to the resonance current (current _IL1 and current _IL2 ). Can be reduced, and the cost for measures against heat generation can be reduced.

[Second Embodiment]
FIG. 6 shows the magnetic field resonance power supply device 100B according to the second embodiment of the present invention. The magnetic field resonance power supply device 100B includes a first feeding unit 110, a second feeding unit 120, and a first control unit 130B and a second control unit 140B corresponding to the "control unit" of the present invention.

The first feeding unit 110 and the second feeding unit 120 have the same configuration as that of the first embodiment. The first control unit 130B has the same configuration as that of the first embodiment except for the turn-off control circuit 133B. The second control unit 140B has the same configuration as that of the first embodiment except that the current detection circuit 147B and the zero cross detection circuit 148B are further provided.

The current detection circuit _147B measures the current IL2 flowing through the _second transmission coil _L2 , and outputs a signal (for example, a voltage signal) corresponding to the measured current value of the current IL2 to the zero-cross detection circuit 148B.

The zero-cross detection circuit 148B monitors the signal of the current detection circuit _147B and detects the zero-cross point when the current value of the current IL2 changes from negative to positive. The zero-cross detection circuit 148B transmits a zero-cross signal to the turn-off control circuit 133B via the second communication circuit 146 and the first communication circuit 134 at the timing when the zero-cross point is detected.

The turn-off control circuit 133B outputs a turn-off control signal for turning off the first switching element Q ₁ to the first synchronization circuit 132 at the timing when the zero cross signal is received. The first synchronization circuit 132 turns off the first switching element _Q1 based on the turn-off control signal.

FIG. 7 is a timing chart of each part of the magnetic field resonance power supply device 100B according to the present embodiment. The signals (A) to (J) of each part in FIG. 7 are the same as the signals (A) to (J) of each part in FIG. 5 (first embodiment). Further, the modes 1 to 4 in FIG. 7 are the same as the modes 1 to 4 in FIG.

As shown in FIG. 7 (J), when the zero cross detection circuit _148B detects the zero cross point of the current IL2 at time t ₅₂ , the zero cross detection circuit 148B sends a zero cross signal to the second communication circuit 146 and the first communication circuit 134. It is transmitted to the turn-off control circuit 133B via. Upon receiving the zero-cross signal, the turn-off control circuit 133B outputs the turn-off control signal to the first synchronization circuit 132, and at time _t62 , the first synchronization circuit 132 turns off the _first switching element Q1. The time t ₆₂ corresponds to the same timing as the time t ₆₁ of the first embodiment.

The length of the period (between time t ₅₁ and t ₅₂ ) that contributes to power transmission in the mode 2 period matches the length of the first phase shift time T _Φ , and at least the maximum phase at a low load of less than the maximum transmission power. The shift time is shorter than T _ΦM . Therefore, as in the first embodiment, the first on-time _Ton1'is shorter than the on-time _Ton1 (= maximum on-time _Ton1 ) of the comparative example, and the second on-time _Ton2'is also on in the comparative example. It will be shorter than the time _Ton2 .

When the first on-time _Ton1'and the second on-time _Ton2'are shortened, the peak values of the current I _SW1 and the current I _SW2 become smaller, and the peak values of the resonance currents (current _IL1 and current _IL2 ) also become smaller. ..

Therefore, the magnetic field resonance power supply device 100B can suppress an increase in loss due to the influence of the resonance current at a low load when the transmission power becomes small, and can suppress a large decrease in the transmission efficiency. Further, the magnetic field resonance power supply device 100B generates heat from the first transmission coil L ₁ and the first resonance capacitor C ₁ and the second transmission coil L ₂ and the second resonance capacitor C ₂ due to the resonance current (current _IL1 and current _IL2 ). Can be reduced, and the cost for measures against heat generation can be reduced.

[Third Embodiment]
FIG. 8 shows the magnetic field resonance power supply device 100C according to the third embodiment of the present invention. The magnetic field resonance power supply device 100C includes a first feeding unit 110, a second feeding unit 120C, and a first control unit 130 and a second control unit 140C corresponding to the "control unit" of the present invention.

The first power feeding unit 110 and the first control unit 130 have the same configuration as that of the first embodiment. The second feeding unit 120C has the same configuration as that of the first embodiment except that the second switch SW ₂ is composed of only the second diode D ₂ . The second control unit 140C has the same configuration as that of the first embodiment except that the second resonance voltage detection circuit 141 and the second synchronization circuit 142 are not provided and the phase difference control circuit 145C is provided.

The phase difference control circuit 145C turns off the _first switching element Q1 and the second switch SW ₂ (second) so that the power value of the transmission power approaches the target value based on the difference signal input from the comparison circuit 144. The first phase shift time T _Φ , which is the time difference from the turn-off of the diode D ₂ ), is calculated. The phase difference control circuit 145C transmits a signal relating to the first phase shift time _TΦ to the turn-off control circuit 133 via the second communication circuit 146 and the first communication circuit 134.

Unlike the first embodiment, the phase difference control circuit 145C does not receive the first timing signal regarding the timing for turning off the first switching element Q ₁ , but the second timing regarding the timing for turning off the second switching element Q ₂ . It also does not generate a signal.

Similar to the first embodiment, the turn-off control circuit 133 calculates the phase margin time as the absolute value of the difference between the maximum phase shift time T _ΦM and the first phase shift time T _Φ (first arithmetic processing), and the maximum on. The first on-time _Ton1 ', which is the difference between the time _Ton1 and the phase margin time, is calculated to generate an on-time control signal for the first on-time _Ton1 '(second arithmetic processing).

The first synchronization circuit 132 turns off the first switching element Q1 when the first on-time _Ton1'has elapsed since the _first switching element _Q1 was turned on based on the on-time control signal. Therefore, the first on-time _Ton1'is shorter than the maximum on-time _Ton1 .

FIG. 9 is a timing chart of each part of the magnetic field resonance power supply device 100C according to the present embodiment. The signals (A) to (D) and (G) of each part in FIG. 9 are the same as the signals (A) to (D) and (I) of each part in FIG. 5 (first embodiment).

FIG. 9E is a waveform of the current I _SW2 flowing through the second switch SW ₂ (second diode D ₂ ). In the first embodiment, the second switching element Q ₂ of the second switch SW ₂ is turned on by the zero cross signal of the voltage _{VR 2} , but in the present embodiment, the second switch SW ₂ is from only the second diode D ₂ . Therefore, the second diode D ₂ is not controlled (automatically turns on and off). In the second diode D ₂ , the period of mode 2 and mode 3 is turned on, and the period of mode 4 and mode 1 is turned off.

FIG. 9F is a waveform of the voltage V _SW2 across the second switch SW ₂ (second diode D ₂ ). In the present embodiment, the voltage V _{SW 2} across the second switch SW 2 is induced by the current IL 1 flowing through the first transmission coil _{L 1} .

FIG. 9H is a waveform of the current IL2 flowing through the _second transmission coil _L2 . The current _IL2 has a phase difference (first phase shift time T _Φ ) corresponding to the transmission power with respect to the current _IL1 . Further, during the period in which the current _IL1 is positive and the current _IL2 is negative in the mode 2 period, power is transmitted from the first feeding unit 110 to the second feeding unit 120C.

In the present embodiment, control is performed to turn off the first switching element Q ₁ when the first on time _{Ton 1'has} elapsed after the first switching element Q ₁ is turned on (for example, at time t ₆₁ ). The second switch SW ₂ (second diode D ₂ ) is not controlled and is automatically set when the first phase shift time T _Φ elapses after the first switching element Q ₁ is turned off (for example, time t ₇₁ ). Turn off to.

Therefore, as in the first embodiment, the first on-time _Ton1'is shorter than the on-time _Ton1 (= maximum on-time _Ton1 ) of the comparative example, and the second on-time _Ton2'is also on in the comparative example. It will be shorter than the time _Ton2 . When the first on-time _Ton1'and the second on-time _Ton2'are shortened, the peak values of the current I _SW1 and the current I _SW2 become smaller, and the peak values of the resonance currents (current _IL1 and current _IL2 ) also become smaller. ..

Therefore, the magnetic field resonance power supply device 100C can suppress an increase in loss due to the influence of the resonance current at a low load when the transmission power becomes small, and suppresses a large decrease in the transmission efficiency, as in the first embodiment. can. Further, the magnetic field resonance power supply device 100C generates heat from the first transmission coil L ₁ and the first resonance capacitor C ₁ and the second transmission coil L ₂ and the second resonance capacitor C ₂ due to the resonance current (current _IL1 and current _IL2 ). Can be reduced, and the cost for measures against heat generation can be reduced.

[Fourth Embodiment]
FIG. 10 shows a magnetic field resonance power supply device 100D according to a fourth embodiment of the present invention. The magnetic field resonance power supply device 100D includes a first feeding unit 110, a second feeding unit 120, and a first control unit 130D and a second control unit 140D corresponding to the "control unit" of the present invention.

The first feeding unit 110 and the second feeding unit 120 have the same configuration as that of the first embodiment. The first control unit 130D has the same configuration as that of the first embodiment except for the turn-off control circuit 133D. The second control unit 140D has the same configuration as that of the first embodiment except that the reference voltage signal Vref is input to the comparison circuit 144 and transmitted from the second communication circuit 146. The reference voltage signal Vref is transmitted to the turn-off control circuit 133D via the second communication circuit 146 and the first communication circuit 134.

The turn-off control circuit 133D determines the relationship between the transmission power (in this embodiment, the voltage value of the reference voltage signal Vref) and the on-time of the _first switching element Q1 (in this embodiment, the first on-time _Ton1 '). Has the data shown. The turn-off control circuit 133D determines the turn-off timing of the _first switching element Q1 based on the reference voltage signal Vref and the above data without acquiring the signal relating to the first phase shift time T _Φ from the second control unit 140D. Determine and generate an on-time control signal.

FIG. 11 shows an example of the relationship between the reference voltage signal Vref included in the above data and the first on-time _Ton1 '. In FIG. 11, the signal value (voltage value) of the reference voltage signal Vref at the maximum transmission power is Xmax, and the maximum value (maximum on-time _Ton1 ) of the first on-time _Ton1'is Ymax.

In the data shown in FIG. 11, when the reference voltage signal Vref is Xmax, the first on-time _Ton1'is Ymax. When the reference voltage signal Vref is from a predetermined first threshold value X ₁ (however, X ₁ <Xmax) to Xmax, the smaller the signal value of the reference voltage signal Vref (that is, the smaller the transmission power), the smaller the first on-time _Ton1 . 'Becomes shorter. On the other hand, when the signal value of the reference voltage signal Vref is smaller than the first threshold value X ₁ , the first on-time _{Ton 1'is} a constant value Y ₁ (however, Y ₁ <Y max).

The first threshold value X ₁ is set to, for example, a signal value (voltage value) of the reference voltage signal Vref corresponding to the transmission power when the load is about 1/3 of the rated load. The constant value Y ₁ is set to, for example, a time during which the resonance current required to supply the transmission power can be secured.

Similar to other embodiments, the magnetic field resonance power supply device 100D can suppress an increase in loss due to the influence of a resonance current at a low load when the transmission power becomes small, and can suppress a large decrease in transmission efficiency. Further, the magnetic field resonance power supply device 100D generates heat from the first transmission coil L ₁ and the first resonance capacitor C ₁ and the second transmission coil L ₂ and the second resonance capacitor C ₂ due to the resonance current (current _IL1 and current _IL2 ). Can be reduced, and the cost for measures against heat generation can be reduced.

Further, the magnetic field resonance power supply device 100D controls so that the _first on-time _Ton1'is a constant value Y1 when the reference voltage signal Vref is smaller than the _first threshold value X1, so that the resonance current becomes small. It is possible to avoid the operation becoming unstable because of too much. That is, the magnetic field resonance power supply device 100D can be operated stably even in the case of a very low load of about 1/3 or less of the rated load.

[Modification example]
Although the embodiment of the magnetic field resonance power supply device according to the present invention has been described above, the present invention is not limited to each of the above embodiments.

The magnetic field resonance power supply device according to an embodiment of the present invention includes a first power feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element. A second power supply unit including a second transmission coil, a second resonance capacitor, a second switching element, and a second diode connected in parallel to the second switching element, and a turn-off of the first switching element and a turn-off of the second switching element. A phase shift control circuit that controls the first phase shift time, which is the time difference between the two, according to the power value of the transmission power, and a first switching element that controls the turn-off of the first switching element according to the power value of the transmission power. If the on-time control circuit for controlling the on-time is provided, the configuration can be appropriately changed.

The magnetic field resonance power supply device according to another embodiment of the present invention includes a first power feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element. , A second power supply unit including a second transmission coil, a second resonance capacitor, and a second diode, and a control unit. The second diode has a predetermined time difference after the first switching element is turned off. Since the turn-off is performed after the phase shift time has elapsed and the control unit controls the turn-off of the first switching element according to the power value of the transmission power, the on-time control circuit for controlling the on-time of the first switching element is provided. If so, the configuration can be changed as appropriate.

For example, in the first embodiment, the phase difference in the phase shift control is controlled on the assumption that the phase difference is controlled in the range of 90 ° around 0 °, but the description is not limited to this, and the phase difference is not limited to −180 ° to −. It may be controlled in the range of 90 °. In that case, since the maximum phase shift time T _ΦM is the minimum, the phase margin time is obtained by subtracting the maximum phase shift time T _ΦM from the first phase shift time T _Φ .

In the third embodiment, the second switch SW ₂ is configured to include only the second diode D ₂ , but the second switch SW ₂ is parallel to the second switching element Q ₂ and the second switching element Q ₂ in the opposite direction. The configuration may include the connected second diode D ₂ and the second switching element Q ₂ may be always off.

In the first embodiment and the second embodiment, in order to simplify the explanation, a configuration in which power is transmitted in one direction from the first feeding unit 110 to the second feeding unit 120 has been described, but the control circuit (first). It can also be applied to a configuration in which power is transmitted in both directions by appropriately supporting both the 1 control unit and the 2nd control unit).

In the first embodiment and the second embodiment, when power is transmitted from the first feeding unit 110 to the second feeding unit 120, the second switching element _Q2 is turned off and diode rectification by the _second diode D2 is performed. It may be used for power transmission.

In the first to fourth embodiments, the first communication circuit 134 and the second communication circuit 146 are used as non-contact communication means, but in an environment where a wired connection is possible, the communication means may be a wired connection.

In the fourth embodiment, when the reference voltage signal Vref is smaller than the first threshold value X ₁ , the turn-off of the first switching element Q ₁ is controlled so that the first on-time _{Ton 1'is} a constant value Y ₁ . Also in the first to third embodiments, when the load is low and the transmission power is smaller than the predetermined second threshold value X ₂ , for example, when the load is very low such that the load is less than 1/3 of the rating, It is preferable to control the turn-off of the _first switching element Q1 so that the _first on-time _Ton1'is a constant value (for example, Y1). Further, when the transmission power is equal to or higher than the second threshold value X ₂ , the turn-off of the first switching element Q ₁ may be controlled so that the first on-time _{Ton 1'is} shortened as the transmission power becomes smaller.

In the first embodiment, the first power feeding unit 110, the second power feeding unit 120, the first control unit 130, and the second control unit 140 can be configured as one device, and can be installed in a home, for example. can. When one device is used, the first communication circuit 134 and the second communication circuit 146 can be simplified or omitted as communication circuits in the device.

In the first embodiment, the mutual phase detection control method for notifying the turn-off timing of the _first switching element Q1 on the power transmission side to the phase difference control circuit 145 on the power reception side has been described, but the power transmission power is transmitted on the power transmission side or the power reception side. It can also be applied to a self-phase detection control method that detects a phase difference (first phase shift time) by detecting it. In the case of the self-phase detection control method, phase information may be transmitted to the power receiving side or the power transmitting side, and control may be performed to shorten the on-time of the _first switching element Q1 by the phase margin time.

100A, 100B, 100C, 100D Magnetic field resonance power supply 110 1st power supply unit 120, 120C 2nd power supply unit 130, 130B, 130D 1st control unit 131 1st resonance voltage detection circuit 132 1st synchronous circuit 133, 133B, 133D Turn-off Control circuit 134 1st communication circuit 140, 140B, 140C, 140D 2nd control unit 141 2nd resonance voltage detection circuit 142 2nd synchronous circuit 143 Power detection circuit 144 Comparison circuit 145, 145C Phase difference control circuit 146 2nd communication circuit 147B Current detection circuit 148B Zero cross detection circuit

Claims (7)

A first feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element.
A second feeding unit including a second transmission coil, a second resonant capacitor, a second switching element, and a second diode connected in parallel to the second switching element.
With a control unit,
A magnetic field resonance power supply device that supplies transmission power from the first feeding unit to the second feeding unit by magnetic field resonance.
The control unit
A phase shift control circuit that controls the first phase shift time, which is the time difference between the turn-off of the first switching element and the turn-off of the second switching element, according to the power value of the transmission power.
An on-time control circuit that controls the on-time of the first switching element by controlling the turn-off of the first switching element according to the power value of the transmission power.
A magnetic field resonant power supply comprising. A first feeding unit including a first transmission coil, a first resonance capacitor, a first switching element, and a first diode connected in parallel to the first switching element.
A second feeding unit including a second transmission coil, a second resonant capacitor, and a second diode,
With a control unit,
A magnetic field resonance power supply device that supplies transmission power from the first feeding unit to the second feeding unit by magnetic field resonance.
The second diode turns off after the lapse of the first phase shift time, which is a predetermined time difference from the turn-off of the first switching element.
The control unit
A magnetic field resonance power supply device comprising an on-time control circuit that controls the on-time of the first switching element by controlling the turn-off of the first switching element according to the power value of the transmission power. The on-time control circuit is
The first arithmetic processing for calculating the phase margin time, which is the difference between the maximum phase shift time, which is the time difference at the time of the maximum transmission power at which the transmission power is maximum, and the first phase shift time,
A second arithmetic process for calculating the first on-time, which is the difference between the maximum on-time, which is the on-time of the first switching element at the time of the maximum transmission power, and the phase margin time, is performed.
The magnetic field resonance power supply device according to claim 1 or 2, wherein the first switching element is turned off after the first on time has elapsed from the turn on of the first switching element. The control unit
A current detection circuit that detects the current value of the current flowing through the second transmission coil, and
A zero-cross detection circuit that outputs a zero-cross signal at the timing when the zero-cross point when the current value changes from negative to positive is detected.
Further prepare
The on-time control circuit is
The magnetic field resonance power supply device according to claim 1 or 2, wherein the first switching element is turned off at the timing when the zero cross signal is input. The on-time control circuit has data showing the relationship between the transmission power and the on-time of the first switching element, and is characterized in that the turn-off timing of the first switching element is determined based on the data. The magnetic field resonance power supply device according to claim 1 or 2. In the data, when the transmission power is from a predetermined first threshold value to the maximum value, the on-time of the first switching element becomes shorter as the transmission power becomes smaller, while the transmission power is smaller than the first threshold value. The magnetic field resonance power supply device according to claim 5, wherein the first switching element has a constant on-time relationship. When the transmission power is equal to or higher than a predetermined second threshold value, the on-time control circuit controls the turn-off of the first switching element so that the on-time of the first switching element becomes shorter as the transmission power becomes smaller. On the other hand, according to claim 1, when the transmission power is smaller than the second threshold value, the turn-off of the first switching element is controlled so that the on time of the first switching element becomes a constant value. 4. The magnetic field resonance power supply device according to any one of 4.

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