Contactless power supply device

Abstract

To provide a non-contact power feeding device capable of detecting a power feeding value.SOLUTION: A non-contact power feeding device comprises: a drive circuit 122 that includes a power feeding coil L1 for performing non-contact power feeding, a resonance capacitor C1 connected to the power feeding coil, and a drive unit 123 for driving the power feeding coil; a power source 119 that feeds operative power to the drive circuit; feed power computation units 111 and 115 that compute a power feeding value of the power source on the basis of a voltage value of the power source and a current value of the power source; loss power computation units 112, 113 and 116 that compute a loss power value of the drive circuit on the basis of the current value of the power source and a loss resistance value of the drive circuit; and a subtraction unit 117 that outputs a power feeding value by subtracting the loss power value from the power feeding value of the power source.SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a contactless power supply device.

Background Art

[0002] Patent Document 1 describes a contactless power supply device that has a power supply unit including a power supply coil connected to a power source, and the power supply coil and a power receiving coil connected to a load are electromagnetically coupled to supply power from the power source to the load. The power supply unit includes a socket unit having an AC application circuit and a power supply unit mounting portion, and a power supply coil unit having a power supply coil. The power supply coil unit is detachably mounted on the power supply unit mounting portion.

[0003] Patent Document 2 describes a power transmission device that has an inverter that outputs high-frequency power, a control unit that controls the inverter, a power transmission-side capacitor connected to the output of the inverter to which high-frequency power is supplied, and a power transmission coil connected to the power transmission-side capacitor. The power transmission device has an input power detection unit that detects the input power of the inverter, and a phase difference detection unit that detects the phase difference between the output voltage and output current of the inverter. The control unit changes the drive frequency and output duty of the inverter so as to make the phase difference zero while keeping the input power of the inverter constant based on the input power of the inverter and the phase difference detected by the phase difference detection unit.

[0004] Patent Document 3 describes a power reception control device that charges a secondary battery, in which a power reception unit that is electromagnetically energized through a space by a power supply unit installed at a charging location and power is transmitted from the power supply unit is provided in an electric vehicle. The power reception control device has a power reception unit drive means that moves the power reception unit closer to and away from the power supply unit, a power supply power detection means that detects the power supply power output from the power supply unit, and a control means that drives the power reception unit drive means to move the power reception unit to a power reception possible range when the power supply power exceeds the power reception capacity of the secondary battery.

[0005] Patent Document 4 describes a contactless power supply system that supplies high-frequency power from a power transmission device to a power reception device in a contactless manner. The power transmission device includes high-frequency generation means for generating high-frequency power, a power transmission coil, and a resonance capacitor connected to the power transmission coil, and a power transmission unit that transmits the high-frequency power input from the high-frequency generation means in a contactless manner, power detection means for detecting the reflected wave power reflected by the power reception device, and power transmission device side control means for stopping the transmission of high-frequency power based on the reflected wave power. The power reception device includes a power reception coil magnetically coupled to the power transmission coil, and a resonance capacitor connected to the power reception coil, and a power reception unit that receives the high-frequency power transmitted from the power transmission unit in a contactless manner, a rectifier circuit that converts the high-frequency power received by the power reception unit into DC power, power storage means charged by the DC power output from the rectifier circuit, a switch that switches between supplying and blocking the DC power output from the rectifier circuit to the power storage means, and power reception device side control means for switching the switch so as to block the DC power from the rectifier circuit to the power storage means when the charging of the power storage means is completed based on the charging status of the power storage means, and stopping the charging of the power storage means.

Prior Art Documents

Patent Documents

[0006]

Patent Document 1

Patent Document 2

Patent Document 3

Patent Document 4

Summary of the Invention

Problems to be Solved by the Invention

[0007] The power supply device can perform non-contact power supply to the power receiving device. The power supply power that the power supply device supplies to the power receiving device varies depending on the distance between the power supply device and the power receiving device, etc. The power receiving device can detect the power supply power. However, the power supply device does not know the distance between the power supply device and the power receiving device, and it is difficult to detect the power supply power.

[0008] An object of the present invention is to provide a non-contact power supply device that can detect a power supply power value.

Means for Solving the Problems

[0009] The non-contact power supply device includes a power supply coil for performing non-contact power supply, a resonance capacitor connected to the power supply coil, a drive circuit having a drive unit for driving the power supply coil, a power supply for supplying operating power to the drive circuit, a supply power calculation unit for calculating the supply power value of the power supply based on the voltage value and current value of the power supply, a loss power calculation unit for calculating the loss power value in the drive circuit based on the current value of the power supply and the loss resistance value of the drive circuit, and a subtraction unit for outputting a power supply power value by subtracting the loss power value from the supply power value of the power supply.

Effects of the Invention

[0010] It is possible to provide a non-contact power supply device that can detect a power supply power value.

Brief Description of the Drawings

[0011]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Figure 7

[0012] (First Embodiment) FIG. 1 is a diagram showing a configuration example of a power feeding system 100 according to the first embodiment. The power feeding system 100 is a non-contact power feeding system and includes a power feeding device 101 and a power receiving device 102.

[0013] The power feeding device 101 is a non-contact power feeding device and includes multiplication circuits 111 to 113, a DC bias source 114, low-pass filters 115 and 116, a subtraction circuit 117, a control unit 118, a variable DC power supply 119, a drive signal source 120, a differential amplifier 121, a drive circuit 122, and a current detection resistor Rs. The drive circuit 122 includes a drive unit 123, a magnetic material 124, a loss resistor Ra, a power feeding coil L1, and a resonance capacitor C1. The drive unit 123 is a half-bridge drive circuit and includes switches SW1 and SW2.

[0014] The loss resistor Ra is an equivalent loss resistor. The loss resistor Ra represents the sum of the on-resistance of the switches SW1 and SW2, the equivalent series resistance of the power feeding coil L1, and the resistance component that equivalently increases the equivalent series resistance of the power feeding coil L1 due to the induced current flowing through the surrounding structures.

[0015] The variable DC power supply 119 is connected to a reference potential node (ground potential node) and outputs a DC power supply voltage V1 from an output terminal OUT in accordance with a control signal of the control unit 118. The power supply voltage V1 changes in accordance with the control signal. The drive signal source 120 receives the supply of the power supply voltage V1 from the variable DC power supply 119 and outputs a control signal to the switches SW1 and SW2.

[0016] The current detection resistor Rs is connected between the output terminal OUT of the variable DC power supply 119 and the switch SW1. The switch SW1 is connected between the current detection resistor Rs and the switch SW2, and turns on or off according to the control signal of the drive signal source 120. The switch SW2 is connected between the switch SW1 and the reference potential node, and turns on or off according to the control signal of the drive signal source 120. The loss resistor Ra is an equivalent loss resistor and is connected between the interconnection point of the switches SW1 and SW2 and the power supply coil L1. The magnetic material 124 is provided on the back of the power supply coil L1. The resonance capacitor C1 is connected between the power supply coil L1 and the reference potential node. The power supply coil L1 and the resonance capacitor C1 form a resonance circuit.

[0017] The state where the switch SW1 is on and the switch SW2 is off, and the state where the switch SW1 is off and the switch SW2 is on are alternately repeated. The drive unit 123 supplies a high-frequency AC voltage to the power supply coil L1 and the resonance capacitor C1. FIG. 3(A) shows an example of the voltage VL1 of the power supply coil L1 and the current I1 supplied from the output terminal OUT of the variable DC power supply 119 to the drive circuit 122. The voltage VL1 becomes a sine wave due to the resonance of the power supply coil L1 and the resonance capacitor C1. The current I1 corresponds to a waveform obtained by half-wave rectifying a sine wave. During the period when the switch SW1 is on and the switch SW2 is off, the current I1 becomes a sine wave. During the period when the switch SW1 is off and the switch SW2 is on, the current I1 becomes 0 [A].

[0018] The power receiving device 102 has a power receiving coil L2 and a load RL. The load RL is, for example, 60 Ω and is connected to the power receiving coil L2. The power supply coil L1 and the power receiving coil L2 are magnetically coupled with a coupling coefficient K. The power supply coil L1 supplies non-contact power to the power receiving coil L2 by magnetic coupling.

[0019] The coupling degree K between the power supply coil L1 and the power receiving coil L2 varies depending on the distance between the power supply coil L1 and the power receiving coil L2, as well as the positional deviation or inclination of the power supply coil L1 or the power receiving coil L2. For example, when the distance between the power supply coil L1 and the power receiving coil L2 moves away from the reference value, the coupling degree K decreases, and the power supply power that the power supply device 101 supplies to the power receiving device 102 decreases. Conversely, when the distance between the power supply coil L1 and the power receiving coil L2 approaches the reference value, the coupling degree K increases, and the power supply power that the power supply device 101 supplies to the power receiving device 102 increases. The power supply device 101 needs to supply a constant power supply power to the power receiving device 102. The variable DC power supply 119 controls the power supply voltage V1 so that the power supply power value Pout becomes constant. Specifically, when the power supply power value Pout is smaller than the target value, the variable DC power supply 119 increases the power supply voltage V1, and when the power supply power value Pout is larger than the target value, the variable DC power supply 119 decreases the power supply voltage V1. Therefore, the power supply device 101 needs to detect the power supply power value Pout that is supplying power to the power receiving device 102. Hereinafter, a method for detecting the power supply power value Pout will be described.

[0020] The power supply power value Pout is represented by the following formula based on the supplied power value Pin, the loss power value Ploss, and the radiated power value Pant. Pout = Pin - Ploss - Pant

[0021] The supplied power value Pin is the supplied power value of the variable DC power supply 119 and is the power value that the variable DC power supply 119 supplies to the drive circuit 122. The supplied power Pin is represented by the average value of the product of the voltage V1 and the current I1 supplied by the variable DC power supply 119.

[0022] The loss power value Ploss is the sum of the loss power value in the drive circuit 122 and the loss power value generated by the current induced in the surrounding structures. The loss power value Ploss is represented by the average value of the product of the square of the current flowing through the loss resistance Ra and the loss resistance Ra.

[0023] The loss resistance Ra is the equivalent loss resistance. The loss resistance Ra is the equivalent resistance that represents the sum of the on-resistances of the switches SW1 and SW2, the equivalent series resistance of the power supply coil L1, and the increased resistance component of the equivalent series resistance of the power supply coil L1 that equivalently represents the loss power generated due to the induced current flowing through the surrounding structures.

[0024] The radiated power value Pant is the power value radiated as radio waves from the power supply coil L1. The power supply power value Pout is the power value supplied by the power supply device 101 to the power receiving device 102 by magnetic field coupling. The power supply power value Pout is the same value as the power consumption value of the power receiving device 102.

[0025] Next, it is explained that the radiated power value Pant is a minute value that can be ignored. When the frequency of the power supply power is 100 kHz, the wavelength of the power supply power is about 3000 m. The dimensions of the power supply coil L1 are sufficiently smaller than this wavelength of the power supply power. Therefore, the radiated power value Pant can be ignored.

[0026] The radiated power value Pant is represented by the product of the square of the current flowing through the power supply coil L1 and the radiation resistance Rr. The radiation resistance Rr is the resistance that equivalently represents the loss power due to the current flowing through the power supply coil L1 being radiated as radio waves, and is represented by the following formula. Rr = Zo × Ko 4 × N 2 × π × r 4 / 24

[0027] Here, Zo is the impedance of space and is 120π Ω. Ko is the wave number (propagation constant) and is 2π / λ. λ is the wavelength and is, for example, 3000 m. N is the number of turns of the power supply coil L1. r is the radius (m) of the power supply coil L1. In this case, the radiation resistance Rr is represented by the following formula. Rr = 5π × (2π / 3000) 4 × N 2 × π × r 4

[0028] Here, when the number of turns N is 30 and the radius r is 1 m, the radiation resistance Rr is 0.85 μΩ. In this case, when a current of 10 A (rms value) flows through the power supply coil L1, the radiation power value Pant is only 85 μW. Therefore, the radiation power value Pant can be ignored. In that case, the power supply power Pout is expressed by the following equation. Pout = Pin - Ploss

[0029] Next, an example of the power supply device 101 controlling the power supply so that the power supply power value Pout is constant at 5 W will be described. The variable DC power supply 119 supplies a DC power supply voltage V1 from the output terminal OUT. The current detection resistor Rs is, for example, 1 mΩ. During the period when the switch SW1 is on, the current flowing through the current detection resistor Rs is the same as the current flowing through the loss resistor Ra. The variable DC power supply 119 can supply a DC power supply voltage V1 in the range of 3 to 15 V according to the control signal of the control unit 118. The frequency of the control signal of the drive signal source 120 is 120 kHz.

[0030] The switch SW1 is a high-side switch and has an on-resistance of several mΩ or less. The switch SW2 is a low-side switch and has an on-resistance of several mΩ or less. The on-resistances of the switches SW1 and SW2 are sufficiently smaller than the equivalent series resistance of the power supply coil L1.

[0031] The output terminal of the drive unit 123 is connected to the reference potential node via a series circuit of the power supply coil L1 and the resonance capacitor C1. The power receiving coil L2 faces the power supply coil L1. The power supply coil L1 and the power receiving coil L2 are planar coils so that the distance between the power supply coil L1 and the power receiving coil L2 can be shortened to increase the coupling degree K between the power supply coil L1 and the power receiving coil L2.

[0032] The magnetic material 124 is provided on the back surface of the power supply coil L1 and can concentrate the magnetic field of the power supply coil L1 toward the power receiving coil L2 side. The power supply coil L1 uses Litz wire in order to keep the loss resistance of the power supply coil L1 low. The Q value of the power supply coil L1 is about 200. The power supply coil L1 is 23.87 μH. The loss resistor Ra is 180 mΩ.

[0033] Even when the coupling degree K varies in the range of 0.05 to 0.95, the capacitance value of C1 of the resonance capacitor remains fixed. The power receiving coil L2 is not tuned. The resonance capacitor C1 is configured such that the resonance frequency is the same as the frequency (120 kHz) of the control signal of the drive signal source 120 in the case of loose coupling where the coupling degree K between the power feeding coil L1 and the power receiving coil L2 is 0.05 or less. The resonance capacitor C1 is 0.07368 μF. The resonance capacitor C1 has a high withstand voltage. The loss power of the resonance capacitor C1 is sufficiently smaller than the loss power of the power feeding coil L1.

[0034] The power receiving coil L2 is 23.87 μH and has a loss resistance of 500 mΩ. The Q value of the power receiving coil L2 is 36. The load RL is 60 Ω.

[0035] The drive signal source 120 drives the drive unit 123. The current I1 flowing through the current detection resistor Rs is, for example, as shown in FIG. 3(E), a positive current flowing out from the output terminal OUT of the variable DC power supply 119 to the drive circuit 122, or a negative current returning from the drive circuit 122. The voltage across both ends of the current detection resistor Rs is proportional to the current I1 flowing through the current detection resistor Rs and is represented by the product of the current I1 and the current detection resistor Rs. The differential amplifier 121 amplifies the voltage across both ends of the current detection resistor Rs and outputs a voltage proportional to the voltage across both ends of the current detection resistor Rs. For example, the current detection resistor Rs is 1 mΩ and the amplification factor of the differential amplifier 121 is 1000. The output voltage value of the differential amplifier 121 corresponds to the value of the current I1 flowing through the current detection resistor Rs.

[0036] The multiplication circuit 111 multiplies the output voltage value of the differential amplifier 121 and the value of the power supply voltage V1 of the variable DC power supply 119, and outputs a voltage indicating the supply power value. The low-pass filter 115 outputs a voltage indicating the supply power value Pin obtained by averaging the output voltage of the multiplication circuit 111 by performing low-pass filtering on the output voltage of the multiplication circuit 111.

[0037] The multiplication circuit 112 inputs the output voltage of the differential amplifier 121 to the two input terminals IN1 and IN2, and outputs a voltage indicating the square value of the output voltage value of the differential amplifier 121. The output voltage value of the multiplication circuit 112 corresponds to the square value of the value of the current I1.

[0038] The DC bias source 114 outputs a DC voltage indicating a value twice that of the loss resistance Ra. The multiplication circuit 113 multiplies the output voltage value of the multiplication circuit 112 and the output voltage value of the DC bias source 114, and outputs a voltage indicating the loss power. For example, one cycle of the current I1 in Fig. 3(A) is divided into a period when the current I1 flows and a period when the current I1 does not flow. Since the internal resistance of the variable DC power supply 119, the current detection resistance Rs, the on-resistance of the switch SW1, and the on-resistance of the switch SW2 are sufficiently smaller than the loss resistance Ra, the waveform of the current IL1 flowing through the power supply coil L1 is symmetric in the period when the current flows through the current detection resistance Rs and the period when it does not flow. During the period when the current flows through the current detection resistance Rs, the current from the variable DC power supply 119 flows through the current detection resistance Rs and the switch SW1 to the series circuit of the loss resistance Ra, the power supply coil L1, and the resonance capacitor C1, so the current flowing through the current detection resistance Rs and the loss resistance Ra is equal. The loss power in the loss resistance Ra is I1 2 ×Ra = IL1 2 It is represented by ×Ra.

[0039] Since the waveform of the current IL1 flowing through the power supply coil L1 is symmetric in the period when the current flows through the current detection resistance Rs and the period when it does not flow, the loss power in the loss resistance Ra during the period when the current does not flow through the current detection resistance Rs is the same as the loss power during the period when the current flows through the current detection resistance Rs. Therefore, the loss power in the loss resistance Ra is 2×I1 2 ×Ra. The output voltage value of the multiplication circuit 113 outputs a voltage indicating the loss power of 2×I1 2 ×Ra.

[0040] The low-pass filter 116 outputs a voltage indicating the loss power value Ploss obtained by averaging the output voltage value of the multiplication circuit 113 by performing low-pass filtering on the output voltage of the multiplication circuit 113.

[0041] The subtraction circuit 117 subtracts the voltage value indicating the loss power value Ploss from the voltage value indicating the power supply power value Pin, and outputs the voltage indicating the power supply power value Pout to the control unit 118. The power supply power value Pout is represented by Pin - Ploss.

[0042] The control unit 118 is, for example, a CPU, and based on the voltage indicating the power supply power value Pout, outputs a control signal to the variable DC power supply 119 so that the power supply power value Pout becomes 5W. The variable DC power supply 119 controls the power supply voltage V1 so that the supplied power value Pout becomes 5W. Specifically, when the power supply power value Pout is smaller than 5W, the variable DC power supply 119 increases the power supply voltage V1. Also, when the power supply power value Pout is larger than 5W, the variable DC power supply 119 decreases the power supply voltage V1.

[0043] Note that the amplification factor of the differential amplifier 121 may be reduced, and the multiplication circuits 111 and 112 may multiply the output voltage of the differential amplifier 121 by a coefficient. The current I1 is a value obtained by dividing the voltage across both ends of the current detection resistor Rs by the value of the current detection resistor Rs. Therefore, it suffices to make the sum of the amplification factor of the differential amplifier 121 and the coefficient multiplication of the multiplication circuits 111 and 112 equal to a value corresponding to the value of 1 / Rs.

[0044] FIG. 2 is a diagram showing an example of the parameters of the power supply device 101 when controlling so that the power supply power value Pout becomes 5W, and shows the parameters of the power supply device 101 when the coupling degree K changes.

[0045] First, the case where the coupling coefficient K is 0.05 will be described. In order to set the power supply power value Pout to 5W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 8.4V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(A). The peak value of the current I1 is 27.4A, and the average value of the current I1 is 8.8A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(A). The difference between the maximum value and the minimum value of the voltage VL1 is 1020V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(A). The difference between the maximum value and the minimum value of the current IL1 is 54.8A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(A). The difference between the maximum value and the minimum value of the voltage VL2 is 48.4V. The supply power value Pin is V1×I1 = 8.4V×8.8A ≈ 74W. The loss power value Ploss is 69W. The efficiency is Pout / Pin = 5W / 74W ≈ 6.7%.

[0046] Next, the case where the coupling coefficient K is 0.1 will be described. In order to set the power supply power value Pout to 5W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 5V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(B). The peak value of the current I1 is 13.8A, and the average value of the current I1 is 4.5A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(B). The difference between the maximum value and the minimum value of the voltage VL1 is 510V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(B). The difference between the maximum value and the minimum value of the current IL1 is 27.6A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(B). The difference between the maximum value and the minimum value of the voltage VL2 is 48.6V. The supply power value Pin is V1×I1 = 22.7W. The loss power value Ploss is 17.7W. The efficiency is Pout / Pin = 22%.

[0047] Next, the case where the coupling coefficient K is 0.2 will be described. In order to set the power supply power value Pout to 5 W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 4.2 V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(C). The peak value of the current I1 is 6.8 A, and the average value of the current I1 is 2.2 A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(C). The difference between the maximum value and the minimum value of the voltage VL1 is 260 V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(C). The difference between the maximum value and the minimum value of the current IL1 is 14 A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(C). The difference between the maximum value and the minimum value of the voltage VL2 is 48 V. The supply power value Pin is V1 × I1 = 9.2 W. The loss power value Ploss is 4.2 W. The efficiency is Pout / Pin = 54%.

[0048] Next, the case where the coupling coefficient K is 0.5 will be described. In order to set the power supply power value Pout to 5 W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 6.5 V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(D). The peak value of the current I1 is 2.76 A, and the average value of the current I1 is 0.86 A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(D). The difference between the maximum value and the minimum value of the voltage VL1 is 102 V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(D). The difference between the maximum value and the minimum value of the current IL1 is 5.52 A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(D). The difference between the maximum value and the minimum value of the voltage VL2 is 48.4 V. The supply power value Pin is V1 × I1 = 5.59 W. The loss power value Ploss is 0.6 W. The efficiency is Pout / Pin = 90%.

[0049] Next, the case where the coupling coefficient K is 0.8 will be described. In order to set the power supply power value Pout to 5 W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 9.7 V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(E). The peak value of the current I1 is 1.7 A, and the average value of the current I1 is 0.53 A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(E). The difference between the maximum value and the minimum value of the voltage VL1 is 63 V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(E). The difference between the maximum value and the minimum value of the current IL1 is 3.4 A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(E). The difference between the maximum value and the minimum value of the voltage VL2 is 52 V. The supply power value Pin is V1×I1 = 5.17 W. The loss power value Ploss is 0.2 W. The efficiency is Pout / Pin = 97%.

[0050] [[ID=...]] Next, the case where the coupling coefficient K is 0.95 will be described. In order to set the power supply power value Pout to 5 W, the power supply voltage V1 of the variable DC power supply 119 is controlled to 11.2 V. The waveform of the current I1 flowing through the current detection resistor Rs is as shown in Fig. 3(F). The peak value of the current I1 is 1.44 A, and the average value of the current I1 is 0.45 A. The waveform of the voltage VL1 across both ends of the power supply coil L1 is as shown in Fig. 3(F). The difference between the maximum value and the minimum value of the voltage VL1 is 53 V. The waveform of the current IL1 flowing through the power supply coil L1 is as shown in Fig. 4(F). The difference between the maximum value and the minimum value of the current IL1 is 2.88 A. The waveform of the voltage VL2 across both ends of the power receiving coil L2 is as shown in Fig. 4(F). The difference between the maximum value and the minimum value of the voltage VL2 is 58 V. The supply power value Pin is V1×I1 = 5.07 W. The loss power value Ploss is 0.1 W. The efficiency is Pout / Pin = 99%.

[0051] As shown in Fig. 3(A), when the coupling degree K is low, since the power supply coil L1 and the resonance capacitor C1 are in resonance, the current I1 supplied by the variable DC power supply 119 has a waveform obtained by half-wave rectifying a sine wave. The current I1 is only the positive current flowing out from the variable DC power supply 119, and there is no negative current returning from the drive circuit 122. The waveforms of the voltage VL1 in Fig. 3(A), the current IL1 and the voltage VL2 in Fig. 4(A) are approximately sine waves with little distortion.

[0052] As shown in Fig. 3(F), when the coupling degree K is high, since the resonance of the power supply coil L1 is shifted due to the coupling with the power receiving coil L2, the current I1 supplied by the variable DC power supply 119 has a distorted waveform. The current I1 is not only the positive current flowing out from the variable DC power supply 119 but also has a negative current returning from the drive circuit 122. The waveforms of the voltage VL1 in Fig. 3(F), the current IL1 and the voltage VL2 in Fig. 4(F) have large distortion.

[0053] Since the on-resistances of the switches SW1 and SW2 are sufficiently lower than the loss resistance of the power supply coil L1, the waveform of the current IL1 flowing through the power supply coil L1 is symmetric in the positive and negative directions. During the period when the switch SW1 is on and the switch SW2 is off, the loss power due to the current IL1 flowing through the power supply coil L1 is the same as the loss power due to the current IL1 flowing through the power supply coil L1 during the period when the switch SW1 is off and the switch SW2 is on. Therefore, the multiplication circuit 113 calculates a loss power value obtained by doubling the loss power value during the period when the switch SW1 is on and the switch SW2 is off. Thereby, the low-pass filter 116 can output an appropriate loss power value Ploss.

[0054] As described above, the power supply device 101 includes a power supply coil L1 for performing non-contact power supply, a resonance capacitor C1 connected to the power supply coil L1, a drive circuit 122 having a drive unit 123 for driving the power supply coil C1, and a variable DC power supply 119 for supplying operating power to the drive circuit 122. The switch SW1 is connected between one end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the variable DC power supply 119. The switch SW2 is connected between one end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the reference potential node. The other end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 is connected to the reference potential node.

[0055] The supplied power calculation unit includes a multiplication circuit 111 and a low-pass filter 115, and calculates the supplied power value Pin of the variable DC power supply 119 based on the value of the power supply voltage V1 of the variable DC power supply 119 and the value of the current I1 of the variable DC power supply 119. The loss power calculation unit includes multiplication circuits 112 and 113, a DC bias source, and a low-pass filter 116, and calculates the loss power value Ploss in the drive circuit 122 based on the value of the current I1 of the variable DC power supply 119 and the value of the loss resistance Ra of the drive circuit 122. The subtraction circuit 117 is a subtraction unit that outputs the supplied power value Pout by subtracting the loss power value Ploss from the supplied power value Pin.

[0056] The current detection resistor Rs is connected between the variable DC power supply 119 and the drive unit 123. The differential amplifier 121 outputs a signal proportional to the voltage value between both ends of the current detection resistor Rs. The signal output by the differential amplifier 121 indicates the value of the current I1 of the variable DC power supply 119 or a value proportional to the value of the current I1.

[0057] The multiplication circuit 111 is a multiplication unit that multiplies the signal output by the differential amplifier 121 and a value corresponding to the power supply voltage V1. The low-pass filter 115 outputs a signal indicating the supplied power value Pin by performing low-pass filtering (averaging) on the output signal of the multiplication circuit 111.

[0058] The multiplication circuit 112 is a multiplication unit that outputs a signal corresponding to the square of the signal output by the differential amplifier 121. The multiplication circuit 113 is a multiplication unit that multiplies the output signal of the multiplication circuit 112 by a value corresponding to twice the value of the loss resistor Ra. The low-pass filter 116 outputs a signal indicating the loss power value Ploss by performing low-pass filtering (averaging) on the output signal of the multiplication circuit 113.

[0059] The subtraction circuit 117 outputs a signal indicating the power supply power value Pout by subtracting the signal indicating the loss power value Ploss from the signal indicating the supplied power value Pin. The variable DC power supply 119 controls the power supply voltage V1 based on the signal indicating the power supply power value Pout.

[0060] According to the present embodiment, even if the ripple voltage included in the power supply voltage V1 from the variable DC power supply 119 is large, since the power supply voltage V1 and the current I1 are multiplied and then averaged, the power supply device 101 can detect the power supply power value Pout and control the power supply voltage V1 based on the power supply power value Pout, thereby supplying power with a constant power supply power value Pout.

[0061] (Second Embodiment) FIG. 5 is a diagram showing a configuration example of the power supply system 100 according to the second embodiment. The power supply system 100 in FIG. 5 is obtained by deleting the multiplication circuit 113, the low-pass filter 115, the DC bias source 114, and the differential amplifier 121 from the power supply system 100 in FIG. 1 and adding a low-pass filter 501 and differential amplifiers 502 and 503. Hereinafter, the differences between the second embodiment and the first embodiment will be described.

[0062] The second embodiment is an example applicable when the ripple of the power supply voltage V1 of the variable DC power supply 119 is small. While the ripple of the power supply voltage V1 of the variable DC power supply 119 is small, only the fluctuation of the current I1 is large. Therefore, the low-pass filter 501 averages the voltage across the current detection resistor Rs. The differential amplifier 502 outputs a voltage proportional to the difference between the output potential of the low-pass filter 501 and the potential of the output terminal OUT of the variable DC power supply 119. The multiplication circuit 111 multiplies the output voltage value of the differential amplifier 502 by the value of the power supply voltage V1 of the variable DC power supply 119 and outputs a voltage indicating the power supply power value Pout. Since the ripple of the power supply voltage V1 of the variable DC power supply 119 is small, this is an example where it is not necessary to connect a low-pass filter to the output of the multiplication circuit 111.

[0063] The differential amplifier 503 and / or the multiplication circuit 112 also perform the multiplication of the value of the loss resistor Ra instead of the multiplication circuit 113 in FIG. 1. The value of the loss resistor Ra is constant. The amplification of the differential amplifier 503 and / or the coefficient multiplication of the multiplication circuit 112 correspond to the multiplication by twice the value of the loss resistor Ra. The differential amplifier 503 outputs a voltage proportional to the voltage across the current detection resistor Rs. The multiplication circuit 112 outputs a value obtained by multiplying the squared value of the output voltage value of the differential amplifier 503 by a coefficient. This coefficient corresponds to, for example, twice the value of the loss resistor Ra. The multiplication circuit 112 outputs a signal indicating the loss power of 2×I1 2 ×Ra. The low-pass filter 116 outputs a signal indicating the loss power value Ploss by performing low-pass filtering (averaging) on the output signal of the multiplication circuit 112.

[0064] As described above, the supply power calculation unit includes the low-pass filter 501, the differential amplifier 502, and the multiplication circuit 111. The low-pass filter 501 performs low-pass filtering (averaging) on the voltage across the current detection resistor Rs. The differential amplifier 502 outputs a signal proportional to the output signal of the low-pass filter 501. The multiplication circuit 111 outputs a signal indicating the supply power value Pin by multiplying the signal output by the differential amplifier 502 by a value corresponding to the power supply voltage V1 of the variable DC power supply 119.

[0065] The power loss calculation unit includes a differential amplifier 503, a multiplication circuit 112, and a low-pass filter 116. The differential amplifier 503 outputs a signal proportional to the voltage value across both ends of the current detection resistor Rs. The multiplication circuit 112 outputs a signal corresponding to a value obtained by multiplying a signal corresponding to the square of the signal output by the differential amplifier 503 by a value corresponding to twice the value of the loss resistance Ra of the drive circuit 122. The low-pass filter 116 outputs a signal indicating the power loss value Ploss by performing low-pass filtering (averaging) on the output signal of the multiplication circuit 112.

[0066] The subtraction circuit 117 outputs a signal indicating the power supply power value Pout by subtracting the signal indicating the power loss value Ploss from the signal indicating the supply power value Pin. The variable DC power supply 119 controls the power supply voltage V1 based on the signal indicating the power supply power value Pout.

[0067] According to the present embodiment, the power supply device 101 can detect the power supply power value Pout and supply power with a constant power supply power value Pout by controlling the power supply voltage V1 based on the power supply power value Pout.

[0068] (Third Embodiment) FIG. 6 is a diagram showing a configuration example of the power supply system 100 according to the third embodiment. The power supply system 100 in FIG. 6 is obtained by deleting the current detection resistor Rs, the low-pass filter 501, and the differential amplifiers 502 and 503 from the power supply system 100 in FIG. 5 and adding a current probe 601 and a low-pass filter 602. Hereinafter, the differences between the third embodiment and the second embodiment will be described. This example is also an example applicable when the ripple of the power supply voltage V1 of the variable DC power supply 119 is small.

[0069] The output terminal OUT of the variable DC power supply 119 is connected to the switch SW1 via the current probe 601. The current probe 601 detects the current I1 flowing between the variable DC power supply 119 and the switch SW1 and outputs a voltage proportional to the current I1. The low-pass filter 602 performs low-pass filtering (averaging) on the output voltage of the current probe 601. The output voltage of the low-pass filter 602 is equivalent to the output voltage of the differential amplifier 502 in FIG. 5 and indicates the average value of the current I1. The multiplication circuit 111 multiplies the output voltage value of the low-pass filter 602 by the value of the power supply voltage V1 of the variable DC power supply 119 and outputs a signal indicating the supply power value Pin.

[0070] The output voltage of the current probe 601 is equivalent to the output voltage of the differential amplifier 503 in FIG. 5 and indicates the value of the current I1. The multiplication circuit 112 outputs a signal indicating a value that is a coefficient multiple of the squared value of the output voltage value of the current probe 601. The coefficient corresponds to the value of 2×Ra. The low-pass filter 116 performs low-pass filtering on the output signal of the multiplication circuit 112 and outputs a signal indicating the loss power value Ploss.

[0071] As described above, the current probe 601 outputs a signal proportional to the current I1 of the variable DC power supply 119. The supply power calculation unit includes the low-pass filter 602 and the multiplication circuit 111. The low-pass filter 602 performs low-pass filtering on the output signal of the current probe 601. The multiplication circuit 111 multiplies the output signal of the low-pass filter 602 by a value corresponding to the power supply voltage V1 of the variable DC power supply 119 to output a signal indicating the supply power value Pin.

[0072] The loss power calculation unit includes the multiplication circuit 112 and the low-pass filter 116. The multiplication circuit 112 outputs a signal corresponding to a value obtained by multiplying a signal corresponding to the square of the output signal of the current probe 601 by a value corresponding to twice the value of the loss resistance Ra of the drive circuit 122. The low-pass filter 116 performs low-pass filtering on the output signal of the multiplication circuit 112 to output a signal indicating the loss power value Ploss.

[0073] The subtraction circuit 117 outputs a signal indicating the power supply value Pout by subtracting a signal indicating the loss power value Ploss from a signal indicating the supplied power value Pin. The variable DC power supply 119 controls the power supply voltage V1 based on the signal indicating the power supply value Pout.

[0074] Note that this embodiment can also be applied to the first embodiment. That is, in the power supply system 100 of FIG. 1, a current probe 601 can be provided instead of the current detection resistor Rs and the differential amplifier 121.

[0075] In that case, the supplied power calculation unit includes a multiplication circuit 111 and a low-pass filter 115. The multiplication circuit 111 multiplies the output signal of the current probe 601 by a value corresponding to the power supply voltage V1 of the variable DC power supply 119. The low-pass filter 115 outputs a signal indicating the supplied power value Pin by performing low-pass filtering on the output signal of the multiplication circuit 111.

[0076] The loss power calculation unit includes a multiplication circuit 112, a multiplication circuit 113, and a low-pass filter 116. The multiplication circuit 112 outputs a signal corresponding to the square of the output signal of the current probe 601. The multiplication circuit 113 multiplies the output signal of the multiplication circuit 112 by the voltage value of the DC bias source 114 (a value corresponding to twice the value of the loss resistance Ra). The low-pass filter 116 outputs a signal indicating the loss power value Ploss by performing low-pass filtering on the output signal of the multiplication circuit 113.

[0077] The subtraction circuit 117 outputs a signal indicating the power supply value Pout by subtracting a signal indicating the loss power value Ploss from a signal indicating the supplied power value Pin. The variable DC power supply 119 controls the power supply voltage V1 based on the signal indicating the power supply value Pout.

[0078] According to this embodiment, even if the ripple voltage included in the power supply voltage V1 from the variable DC power supply 119 is large, since the power supply voltage V1 and the current I1 are multiplied and then averaged, the power supply device 101 can detect the power supply power value Pout and control the power supply voltage V1 based on the power supply power value Pout, thereby supplying power with a constant power supply power value Pout.

[0079] (Fourth Embodiment) FIG. 7 is a diagram showing a configuration example of the power supply system 100 according to the fourth embodiment. The power supply system 100 in FIG. 7 is obtained by adding switches SW3 and SW4 to the power supply system 100 in FIG. 5. Hereinafter, the differences between the fourth embodiment and the second embodiment will be described.

[0080] The drive unit 123 is a full-bridge drive circuit and has switches SW1, SW2, SW3, and SW4. The switch SW1 is connected between one end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the variable DC power supply 119. The switch SW2 is connected between one end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the reference potential node. The switch SW3 is connected between the other end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the variable DC power supply 119. The switch SW4 is connected between the other end of the series connection circuit of the power supply coil L1 and the resonance capacitor C1 and the reference potential node.

[0081] The drive unit 123 alternately repeats a first state in which switches SW1 and SW4 are on and switches SW2 and SW3 are off, and a second state in which switches SW1 and SW4 are off and switches SW2 and SW3 are on. In both the first state and the second state, the same current as the current IL1 flowing through the power supply coil L1 flows through the current detection resistor Rs. Therefore, the multiplication circuit 112 outputs a signal indicating the loss power value of I1 × Ra instead of the loss power value of 2 × I1 2 × Ra. 2 × Ra outputs a signal indicating the loss power value.

[0082] The low-pass filter 116 outputs a signal indicating the loss power value Ploss by performing low-pass filtering on the output signal of the multiplication circuit 112. The subtraction circuit 117 outputs a signal indicating the power supply power value Pout by subtracting the signal indicating the loss power value Ploss from the signal indicating the supplied power value Pin. The variable DC power supply 119 controls the power supply voltage V1 based on the signal indicating the power supply power value Pout.

[0083] Note that this embodiment can be applied to the first embodiment. That is, in the power supply system 100 of FIG. 1, instead of the switches SW1 and SW2, switches SW1 to SW4 can be provided. In that case, the multiplication circuit 112 outputs a signal corresponding to the square of the signal output by the differential amplifier 121. The DC bias source 114 outputs a DC voltage indicating the value of the loss resistance Ra. The multiplication circuit 113 multiplies the output signal of the multiplication circuit 112 by the output voltage value of the DC bias source 114 (a value corresponding to the value of the loss resistance Ra). The low-pass filter 116 outputs a signal indicating the loss power value Ploss by performing low-pass filtering on the output signal of the multiplication circuit 113. Even if the ripple voltage included in the power supply voltage V1 from the variable DC power supply 119 is large, since the power supply voltage V1 and the current I1 are multiplied and then averaged, the supplied power value Pin can be detected. Also, the fourth embodiment can be applied to the second and third embodiments.

[0084] The power supply device 101 of the fourth embodiment can perform non-contact power supply of high power to the power receiving device 102 by using the switches SW1 to SW4.

[0085] Next, the effects of the power supply system 100 of the first to fourth embodiments will be described. Since the power supply device 101 can detect the power supply power value Pout, there is an advantage that the magnitude of the power supply power can be controlled only by the power supply device 101 regardless of the coupling degree K. The power supply device 101 has an advantage that the amount of power supplied to the power receiving device 102 can be controlled only by the power supply device 101.

[0086] In addition, the power supply device 101 can detect that the power receiving coil L2 of the power receiving device 102 has approached and is in a favorable coupling orientation by detecting the power supply power value Pout being supplied from the power supply coil L1. Since the power supply device 101 is waiting in a continuous power supply operation or an intermittent operation of low-power driving, even if something other than the power supply target approaches, the power supply power value Pout does not increase, so there is an advantage that it can detect the approach of the power supply target.

[0087] Note that the power supply device 101 can approximately detect the current flowing through the resonance circuit by detecting the voltage of the resonance circuit of the drive coil L1 and the resonance capacitor C1. However, when the coupling degree K is high, the voltage waveform is distorted, so it is necessary to correct the distortion component of the voltage waveform, which requires complex processing. According to the first to fourth embodiments, the power supply device 101 has the advantage of being able to detect the power supply power value Ploss regardless of the voltage waveform of the resonance circuit.

[0088] Note that the above-described embodiments are merely specific examples for implementing the present disclosure, and the technical scope of the present disclosure is not limitedly interpreted by these. That is, the present disclosure can be implemented in various forms without departing from its technical idea or its main features.

Explanation of Reference Numerals

[0089] 100 Power supply system 101 Power supply device 102 Power receiving device 111~113 Multiplication circuits 114 DC bias source 115, 116 Low-pass filters 117 Subtraction circuit 118 Control unit 119 Variable DC power supply 120 Drive signal source 121 Differential amplifier 122 Drive circuit 123 Drive unit 124 Magnetic material

Claims

1. a power supply coil for contactless power supply, a resonance capacitor connected to the power supply coil, and a drive circuit including a drive unit that drives the power supply coil; a power supply that supplies operating power to the drive circuit; a power supply calculation unit that calculates a power supply value of the power supply based on a voltage value of the power supply and a current value of the power supply; a power loss calculation unit that calculates a power loss value in the drive circuit based on a current value of the power supply and a loss resistance value of the drive circuit; a subtraction unit that outputs a power supply value by subtracting the loss power value from the power supply value of the power source; A contactless power supply device comprising:

2. Furthermore, a current detection resistor between the power supply and the drive unit; a first amplifier that outputs a signal proportional to a voltage value between both ends of the current detection resistor; The supply power calculation unit a first multiplier that multiplies the signal output from the first amplifier by a value corresponding to the voltage value of the power supply; 2. The contactless power supply device according to claim 1, further comprising: a first low-pass filter that outputs a signal indicating an average value of the power supply by low-pass filtering an output signal of the first multiplication unit.

3. Further, a current detection resistor is provided between the power supply and the drive unit, The supply power calculation unit a first low-pass filter that low-pass filters the voltage across the current detection resistor; a first amplifier that outputs a signal proportional to the output signal of the first low-pass filter; 2. The contactless power supply device according to claim 1, further comprising: a first multiplier that outputs a signal indicating an average value of the power supply supply power value by multiplying the signal output by the first amplifier by a value corresponding to the voltage value of the power supply.

4. Furthermore, a current detection resistor between the power supply and the drive unit; a first amplifier that outputs a signal proportional to a voltage value between both ends of the current detection resistor; The power loss calculation unit a second multiplier that outputs a signal corresponding to the square of the signal output by the first amplifier; a third multiplier that multiplies the output signal of the second multiplier by a value corresponding to the loss resistance value or twice the value of the loss resistance value; 2. The contactless power supply device according to claim 1, further comprising: a second low-pass filter that outputs a signal indicating an average value of the loss power value by low-pass filtering an output signal of the third multiplication unit.

5. Furthermore, a current detection resistor between the power supply and the drive unit; a first amplifier that outputs a signal proportional to a voltage value between both ends of the current detection resistor; The power loss calculation unit a second multiplier that outputs a signal corresponding to a value obtained by multiplying a signal corresponding to the square of the signal output from the first amplifier by a loss resistance value of the drive circuit or a value twice the loss resistance value; 2. The contactless power supply device according to claim 1, further comprising: a second low-pass filter that outputs a signal indicating an average value of the loss power value by low-pass filtering an output signal of the second multiplication unit.

6. further comprising a current probe for outputting a signal proportional to the current of the power supply; The supply power calculation unit a first low-pass filter that low-pass filters the output signal of the current probe; 2. The contactless power supply device according to claim 1, further comprising: a first multiplier that multiplies an output signal of the first low-pass filter by a value corresponding to a voltage value of the power supply, and outputs a signal indicating an average value of the supply power value of the power supply.

7. further comprising a current probe for outputting a signal proportional to the current of the power supply; The supply power calculation unit a first multiplier that multiplies the output signal of the current probe by a value corresponding to the voltage value of the power supply; 2. The contactless power supply device according to claim 1, further comprising: a first low-pass filter that outputs a signal indicating an average value of the power supply by low-pass filtering an output signal of the first multiplication unit.

8. further comprising a current probe for outputting a signal proportional to the current of the power supply; The power loss calculation unit a second multiplier that outputs a signal corresponding to a value obtained by multiplying a signal corresponding to the square of the output signal of the current probe by a loss resistance value of the drive circuit or a value twice the loss resistance value; 2. The contactless power supply device according to claim 1, further comprising: a second low-pass filter that outputs a signal indicating an average value of the loss power value by low-pass filtering an output signal of the second multiplication unit.

9. further comprising a current probe for outputting a signal proportional to the current of the power supply; The power loss calculation unit a second multiplier that outputs a signal corresponding to the square of the output signal of the current probe; a third multiplier that multiplies the output signal of the second multiplier by a value corresponding to the loss resistance value or twice the value of the loss resistance value; 2. The contactless power supply device according to claim 1, further comprising: a second low-pass filter that outputs a signal indicating the loss power value by low-pass filtering an output signal of the third multiplication unit.

10. The drive unit is a first switch connected between one end of a series-connected circuit of the power supply coil and the resonant capacitor and the power supply; 10. The contactless power supply device according to claim 1, further comprising: a second switch connected between one end of a series connection circuit of the power supply coil and the resonant capacitor and a reference potential node.

11. The drive unit further includes: a third switch connected between the other end of the series-connected circuit of the power supply coil and the resonant capacitor and the power supply; 11. The contactless power supply device according to claim 10, further comprising a fourth switch connected between the other end of the series-connected circuit of the power supply coil and the resonant capacitor and the reference potential node.

12. 12. The contactless power supply device according to claim 1, wherein the power supply controls a voltage of the power supply based on the power supply value.

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