KR102251590B1 - Non-contact feeder system - Google Patents

Abstract

The present invention relates to a non-contact power feeding system including a power feeding device and a power receiving device. The power supply device includes a power supply coil and an AC power supply for supplying AC power to the power supply coil. A power receiving device includes a power receiving coil that magnetically couples when facing the power supply coil to receive AC power in a non-contact manner, a power receiving-side resonance capacitor connected to the receiving coil to form a power receiving-side resonance circuit, and AC power received by the receiving coil. A power reception circuit that converts the power reception voltage to generate a power reception voltage and outputs it to the inverter; and an overvoltage protection circuit that shifts the power reception side resonance frequency of the power reception side resonance circuit when the reception voltage exceeds a threshold voltage for determining an overvoltage condition. It is equipped with.

Description

Non-contact feeding system {NON-CONTACT FEEDER SYSTEM}

The present invention relates to a non-contact power supply system, and in particular, to a non-contact power supply system for supplying power non-contact to a moving object such as an electric transport vehicle.

A technology is being developed that transmits the power output from the power source to the load in a non-contact manner without directly connecting the load and the power source. This technology is commonly referred to as contactless power transmission or wireless power supply. The technology is being applied to power transmission in mobile phones, home appliances, electric vehicles, and automated guided vehicles (AGVs).

In the non-contact power transmission, power is supplied from a power supply device connected to a high-frequency power supply device to a power receiving device connected to a load in a non-contact manner. The power supply device is provided with a power supply coil, and the power supply device is provided with a power reception coil. The power supply coil and the power receiving coil are magnetically coupled to each other to perform non-contact power supply.

In the non-contact power supply system disclosed in Patent Document 1 (Japanese Patent Laid-Open No. 2013-172507), a power receiving device on the vehicle side includes a control unit, a communication unit, and a voltage detection unit in addition to the secondary coil and the power receiving circuit. Further, the power supply device on the side of the parking area is provided with a control unit, a communication unit and a notification unit in addition to the primary coil and the power supply circuit. When an overvoltage occurs in the power receiving device, the power supply circuit is stopped by performing overvoltage communication to the power supply device using the communication unit.

In the non-contact power supply system disclosed in Patent Document 2 (Japanese Patent Laid-Open Publication No. 2012-044762), an overvoltage protection unit is installed in a power receiving device. This overvoltage protection unit protects the power receiving device by shorting the secondary coil of the power receiving device when it detects the occurrence of an overvoltage in the power receiving device. At this time, the power transmission device detects a change in current or voltage due to a short circuit, and turns off the power.

In the technique of Patent Document 1, a communication unit for performing overvoltage communication is required for the power receiving device and the power supply device, respectively. For this reason, the power receiving device and the power feeding device are enlarged. In addition, the power supply circuit cannot be stopped unless overvoltage communication has been performed. For this reason, in the power receiving device, the time in the overvoltage state is prolonged, which causes a great stress on the power receiving device.

In the technique of Patent Document 2, it is possible to protect the power receiving device in a short time when an overvoltage is detected by the power receiving device. However, if the secondary coil is short-circuited and protected, the electric load of the power receiving device is immediately stopped, so it cannot be said that it is always desirable. That is, after detecting the occurrence of the overvoltage, if the overvoltage is lowered and the operation of the electric load can be continued even for a very short time, the reliability of the system can be improved.

In addition, in the technique of Patent Document 2, after the protection in the power receiving device is ended, the power supply circuit of the power supply device is stopped. For this reason, the non-contact power supply system cannot automatically recover, and a human hand is required for the recovery operation. In practice, the overvoltage of the power receiving device is often temporarily generated when the device starts up or when the power receiving device deviates from the positional relationship with the power supply device. That is, the occurrence of a temporary overvoltage is not caused by a failure, so it is not necessary to stop the entire non-contact power supply system even though it is necessary to protect it.

Patent Document 1. Japanese Patent Laid-Open Publication No. 2013-172507 Patent Document 2. Japanese Patent Laid-Open Publication No. 2012-044762

An object of the present invention is to provide a non-contact power supply system having high operational reliability while implementing miniaturization without having a communication unit, which has been derived to solve the problems of the prior art.

In addition, another object of the present invention is to provide a non-contact power supply system capable of automatically recovering while protecting the system in case of a temporary overvoltage occurrence.

The non-contact power supply system of the present invention for solving the above problem is a non-contact power supply system having a power supply device and a power receiving device, wherein the power supply device includes a power supply coil and an AC power supply for supplying AC power to the power supply coil, and the power reception The device converts a power receiving coil that is opposite to the power supply coil and magnetically coupled to receive AC power in a non-contact manner, a receiving-side resonance capacitor connected to the receiving coil to form a receiving-side resonance circuit, and the AC power received by the receiving coil. And a power receiving circuit that generates a receiving voltage and outputs it to the electric load, and an overvoltage protection circuit that changes the receiving side resonance frequency of the receiving side resonance circuit when the receiving voltage exceeds a threshold voltage determining that the overvoltage state is over. do.

Preferably, the overvoltage protection circuit includes a voltage detection circuit for detecting a voltage at a specific point of the power receiving device, a first capacitor connected to one end of the rectifying circuit, and a first capacitor connected between the first capacitor and the ground. 1 switch, and a switch operation unit configured to operate the first switch in a turned-on state when the voltage detected by the voltage detection circuit is equal to or higher than a predetermined voltage.

Preferably, the overvoltage protection circuit further includes a second capacitor connected to the other end of the rectifying circuit, and a second switch connected between the second capacitor and ground, and the voltage detected by the voltage detection circuit is When the voltage is higher than a predetermined voltage, the switch operation unit operates the second switch in a turned-on state.

In the non-contact power supply system of the present invention, the overvoltage protection circuit of the power receiving device changes the resonance frequency of the power receiving side resonance circuit when determining the overvoltage condition. As a result, the receiving side resonant frequency greatly deviates from the frequency of the AC power source, so that the receiving voltage is lowered, the overvoltage condition is eliminated, and the system is protected. That is, in the present invention, since the communication unit is not provided, miniaturization is realized, protection for a short time is possible and operation reliability is high. In addition, the present invention enables automatic recovery in the case of a temporary overvoltage occurrence.

1 is a diagram schematically illustrating a configuration of a non-contact power supply system according to an embodiment of the present invention.
FIG. 2 is a diagram qualitatively showing the frequency characteristics of the power supply performance in the non-contact power supply system of FIG. 1.
FIG. 3 is a diagram of a time chart for explaining an operation of overvoltage protection in the non-contact power supply system of FIG. 1.
FIG. 4 is a diagram of a time chart for explaining the operation of the overcurrent protection circuit in the non-contact power supply system of FIG. 1.

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

1 is a diagram schematically illustrating a configuration of a non-contact power supply system 100 according to an embodiment of the present invention. In Fig. 1, the broken arrows indicate the flow of control. The non-contact power supply system 100 shown in FIG. 1 includes a power supply device 100S and a power reception device 100R. The power supply device 100S is disposed at a certain position. The position of the power receiving device 100R can be changed with respect to the power supply device 100S. As shown, when the power receiving device 100R is disposed at a position opposite to the power supply device 100S, the non-contact power supply system 100 performs non-contact power supply in a magnetic coupling method.

The power supply device 100S includes an AC power supply 120, a power supply side resonance capacitor 132, a power supply coil 131, and an overcurrent protection circuit 133. In detail, the high-voltage output terminal 121 of the AC power supply 120 is connected to one end of the power supply side resonance capacitor 132. The other end of the power supply side resonance capacitor 132 is connected to one end of the power supply coil 131. The other end of the power supply coil 131 is connected to one end of the overcurrent protection circuit 133. The other end of the overcurrent protection circuit 133 is connected to the low voltage output terminal 122 of the AC power supply 120.

The AC power supply 120 supplies AC power to the feeding coil 131. The AC power supply 120 can be configured using, for example, a DC power supply unit that supplies a DC voltage and a known bridge circuit that converts the DC voltage to AC. The frequency f0 of the AC power supply 120 is several 10 kHz to several 100 kHz, but is not limited thereto.

The feed-side resonance capacitor 132 and the feed coil 131 constitute a feed-side resonance circuit. The power supply side resonance circuit becomes a series resonance circuit when viewed from the AC power supply 120. The feed side resonance frequency fs of the feed side resonance circuit is expressed by Equation 1. Here, π is the circumferential ratio, Ls is the inductance value of the power supply coil 131, and Cs is the capacitance value of the power supply side resonance capacitor 132.

The overcurrent protection circuit 133 detects the power supply current IS flowing through the power supply coil 131, and compares the threshold current IF for determining the overcurrent state with a magnitude. The overcurrent protection circuit 133 outputs a stop signal Soff to the AC power supply 120 when the supply current IS exceeds the threshold current IF over a predetermined failure determination time TF. As a result, the AC power supply 120 is stopped. In addition, the failure determination time TF is set longer than the return time TR to be described later.

The power receiving device 100R includes a power receiving coil 141, a power receiving side series resonance capacitor 142, a receiving side parallel resonance capacitor 143, a power receiving circuit, and an overvoltage protection circuit. The power receiving circuit includes a rectifying circuit 150 and a smoothing capacitor 155. The overvoltage protection circuit includes a voltage detection unit 161, a switch control unit 164, capacitors 146 and 148, and switches 147 and 149.

One end of the receiving coil 141 is connected to one end of the receiving-side resonance capacitor 142. The other end of the receiving-side resonance capacitor 142 is connected to one end 144 of the receiving-side resonance capacitor 143. The other end of the receiving coil 141 is connected to the other end 145 of the receiving-side resonance capacitor 143. The terminal 144 is connected to one end of the capacitor 146 and the first input terminal 151 of the rectifier circuit 150. The terminal 145 is connected to one end of the capacitor 148 and the second input terminal 152 of the rectifying circuit 150. The first output terminal 153 and the second output terminal 154 of the rectifier circuit 150 are connected to one end and the other end of the smoothing capacitor 155, the voltage detector 161, and the inverter 162.

One end of the switch 147 is connected to the other end of the capacitor 146, and the other end is grounded. One end of the switch 149 is connected to the other end of the capacitor 148, and the other end is grounded.

When the power receiving coil 141 faces the power supply coil 131, it is magnetically coupled to receive AC power in a non-contact manner. The receiving coil 141 and the receiving-side resonance capacitors 142 and 143 constitute a receiving-side resonance circuit. The power receiving side resonance circuit becomes a series-parallel resonance circuit when viewed from the inverter 162 side. The receiving-side resonant frequency fr of the receiving-side resonant circuit is expressed by Equation (2). Here, π is the circumference ratio, Lr is the inductance value of the receiving coil 141, and Cr is the composite capacitance value of the receiving-side resonance capacitors 142 and 143.

The rectifier circuit 150 may be configured as a known full-wave rectifier circuit in which four rectifier diodes are bridge-connected. The rectifier circuit 150 and the smoothing capacitor 155 generate a DC receiving voltage VR and output to the inverter 162. The inverter 162 performs work on the power receiving device 100R, and its type, power consumption, and the like are not limited. The inverter 162 is a power supply circuit for a drive motor installed in a carrier vehicle or the like, and converts the output of the rectifier circuit 150 into alternating current of an appropriate frequency.

The voltage detection unit 161 detects the received voltage VR and outputs it to the switch control unit 164. The switch control unit 164 compares the power reception voltage VR with a threshold voltage VF for determining an overvoltage state. The switches 147 and 149 are used in a turn-off state during normal operation. The switch control unit 164 outputs a turn-on signal to the switches 147 and 149 when the receiving voltage VR exceeds the threshold voltage VF. As a result, the switches 147 and 149 are operated in a turned-on state, whereby the power-receiving-side resonant frequency fr shown in Equation 2 is shifted. When the switches 147 and 149 are turned on, the resonant frequency is, for example, several tens of times higher than the original, so that the voltage is induced to be small in the power receiving device 100R.

The switch control unit 164 has a timer that measures the elapsed time after operating the switches 147 and 149 to turn off. When the elapsed time reaches a predetermined return time TR, the switch control unit 164 performs a magnitude comparison of the receiving voltage VR and the threshold voltage VF again. When the receiving voltage VR exceeding the threshold voltage VF falls below the threshold voltage VF, the turn-on signal is eliminated. Thereby, the switches 147 and 149 are operated in a turned-off state, and the resonant frequency on the receiving side returns to its original value. On the other hand, the return time TR is set shorter than the failure determination time TF of the overcurrent protection circuit 133.

The voltage detection unit 161 may be configured as, for example, a resistance divider circuit that divides and detects the received voltage VR with a plurality of resistors connected in series. The switch control unit 164 includes, for example, an AD converter that converts the divided voltage value of the receiving voltage VR into a digital voltage value, and an electronic control device that controls the switches 147 and 149 by performing predetermined arithmetic processing on the digital voltage value. It can be configured in combination. For the switches 147 and 149, for example, a power semiconductor having a switching function, an electronic switching relay, or the like can be used.

2 is a diagram qualitatively showing the frequency characteristics of the power supply performance of the non-contact power supply system 100. The horizontal axis of FIG. 2 represents the frequency f, and the vertical axis represents the receiving voltage VR. As shown, the frequency characteristic of the power feeding performance becomes a double characteristic having peaks at the power receiving side resonant frequency fr and the power feeding side resonant frequency fs. At a frequency between the receiving side resonance frequency fr and the feed side resonance frequency fs, the receiving voltage VR is relatively high and stable at the same time. Accordingly, the frequency f0 of the AC power supply 120 is set between the power receiving side resonance frequency fr and the power supply side resonance frequency fs. Thereby, it is less affected by the frequency fluctuation, and at the same time, it is possible to obtain a relatively high receiving voltage VR. In addition, the magnitude relationship between the resonant frequency fr on the receiving side and the resonant frequency fs on the power supply side may be opposite.

Next, the operation of the non-contact power supply system 100 will be described. 3 is a diagram of a time chart schematically illustrating an operation of overvoltage protection of the non-contact power supply system 100. The horizontal axis of FIG. 3 represents the passage of time t, the upper graph represents the power reception voltage VR, and the lower graph represents the power supply current IS, respectively.

In Fig. 3, before time t1, the power receiving device 100R is at an appropriate position with respect to the power feeding device 100S, and non-contact power supply is satisfactorily performed. At this time, the receiving voltage VR is Vn, and the feed current IS is In. At the time point t1, when the receiving voltage VR starts to rise for some reason, the feed current IS also starts to increase at the same time.

As the first cause of the rise in the power reception voltage VR, a change in the position of the power reception device 100R can be considered. That is, when the relative position of the power reception device 100R with respect to the power supply device 100S is changed, the power reception voltage VR may temporarily increase. As the second cause, a sharp fluctuation of the load connected to the inverter 162 can be considered. For example, when the load is a motor, the receiving voltage VR may temporarily increase according to a change in the number of rotations of the motor. As the third cause, failure of circuit components can be considered. For example, if any of the power supply side resonance capacitor 132, the power supply coil 131, the power reception coil 141, and the power reception side resonance capacitor 142, 143 fails, the power reception voltage VR may increase. It is often due to the first or second cause.

At time t2, when the power reception voltage VR exceeds the threshold voltage VF, the switches 147 and 149 are operated in the turn-on state by the switch control unit 164. As a result, the receiving-side resonance frequency fr changes, and the receiving voltage VR starts to decrease. At this time, since the power receiving coil 141 and the inverter 162 are in a closed state, the current flowing through the inverter 162 does not disappear in an instant. If the operation of the switches 147 and 149 to the turn-on state is not performed, the power reception voltage VR continues to increase as indicated by the broken line Vx, and a danger arises. On the other hand, the feed current IS continues to increase after the time t2 and exceeds the threshold current IF at the time t3.

The power reception voltage VR that decreases at time t4 is lower than the voltage value Vn when it is good. At time t5 after the return time TR has elapsed from time t2 when the switches 147 and 149 are operated in the turn-on state, the switch control unit 164 performs a magnitude comparison of the receiving voltage VR and the threshold voltage VF again. At this time, since the receiving voltage VR is less than or equal to the threshold voltage VF, the switches 147 and 149 are operated in a turn-off state by the switch control unit 164. Thereby, the resonant frequency fr on the receiving side is restored, and the receiving voltage VR starts to rise. If the switches 147 and 149 are not operated in the turn-off state, the power reception voltage VR is lowered as indicated by the dashed line, and thus it is not automatically recovered.

When the rise of the receiving voltage VR is due to the first or second cause, the cause is often resolved at the time t5. In this case, the receiving voltage VR is stabilized at the voltage value Vn when it is good. Further, after the time t5, the feed current IS begins to decrease, and stabilizes at the current value In at a good time. That is, when the receiving voltage VR temporarily increases due to the first or second cause, the overvoltage protection circuit not only protects the system by reducing the receiving voltage VR, but also performs automatic recovery.

If the rise of the receiving voltage VR is due to the third cause, the cause is not resolved at time t5. In this case, the receiving voltage VR rises again steeply as indicated by the broken line Vz. Accordingly, when the power reception voltage VR exceeds the threshold voltage VF at time t6, the switches 147 and 149 are again operated in a turn-on state. Further, even after time t5, as indicated by the broken line Iz, the feed current IS exceeds the threshold current IF. From time t3 to time t6, the feed current IS exceeds the threshold current IF, but the failure determination time TF has not yet been reached. Therefore, the overcurrent protection circuit 133 does not output the stop signal Soff at the time point t6.

4 is a diagram of a time chart briefly explaining the operation of the overcurrent protection circuit 133 of the non-contact power supply system 100. FIG. 4 illustrates a case in which the power reception voltage VR increases at time t1 as shown in FIG. 3 and the power supply current IS starts to increase at the same time due to the third cause. The lapse of time t on the horizontal axis in FIG. 4 indicates a period longer than that in FIG. 3. If the third cause occurs, the feed current IS exceeds the threshold current IF after time t3. The failure determination time TF elapses while the operation of the switches 147 and 149 to the turn-on state and the operation to the turn-off state are repeated several times. At time t8 after the failure determination time TF has elapsed from time t3, the overcurrent protection circuit 133 outputs a stop signal Soff. As a result, the AC power supply 120 stops and the feed current IS does not flow.

The non-contact power supply system 100 has the following inherent effects compared to the prior art. As a first effect, the inverter 162 can continue to operate between the time t2 and the time t4. In the prior art, since both ends of the power reception coil 141 are short-circuited at time t2, the power reception voltage VR acting on the inverter 162 disappears in an instant.

As a second effect, if the receiving voltage VR temporarily increases due to the first or second cause, it is possible to perform automatic recovery while protecting the system. In the prior art, when an increase in the power reception voltage VR is detected at the side of the power reception device 100R, the AC power supply 120 is stopped, and a human hand is required for the recovery operation. In the case of a third cause, that is, when the power reception voltage VR increases due to a failure of a circuit component, the AC power supply 120 is stopped as in the prior art, and the entire non-contact power supply system 100 can be reliably protected.

As a third effect, it is possible to prevent the elements constituting the power receiving device 100R from being damaged by the turn-off of the switches 147 and 149 and the operation of the turn-on state. In the prior art, the resonant frequency of the receiving side is also changed by separating the capacitor 143 from the receiving device 100R. However, in this case, a large current flows through the capacitor 143 at the moment of separation, so that the capacitor 143 may be damaged. In the non-contact power supply system 100, when the resonant frequency of the power receiving side is changed, the switches 147 and 149 are operated in a closed state to discharge current to the ground, so that the element of the power receiving device 100R is less likely to be damaged.

Specific structural or functional descriptions presented in the embodiments of the present invention are exemplified only for the purpose of describing the embodiments according to the concept of the present invention, and embodiments according to the concept of the present invention may be implemented in various forms. In addition, it should not be construed as limited to the embodiments described in the present specification, and should be understood to include all modifications, equivalents, and substitutes included in the spirit and scope of the present invention.

Claims (1)

In a non-contact power supply system comprising a power supply device and a power receiving device,
The power supply device includes a power supply coil and an AC power supply for supplying AC power to the power supply coil,
The power receiving device,
A power receiving coil that magnetically couples when facing the power supply coil and receives AC power in a non-contact manner;
A receiving-side resonance capacitor connected to the receiving coil to form a receiving-side resonance circuit,
A power receiving circuit for converting the AC power received by the receiving coil to generate a receiving voltage and outputting it to an inverter;
When the receiving voltage exceeds a threshold voltage for determining an overvoltage state, an overvoltage protection circuit for changing a receiving-side resonance frequency of the receiving-side resonance circuit is provided, and
The overvoltage protection circuit includes a voltage detection circuit for detecting a voltage at a specific point of the power receiving device, a first capacitor connected to one end of a rectifier circuit, a first switch connected between the first capacitor and a ground, and the A second capacitor connected to the other end of the rectifier circuit, a second switch connected between the second capacitor and the ground, and a voltage detected by the voltage detection circuit are used to compare the received voltage VR and the threshold voltage VF. And a switch control unit for operating the first and second switches in a turn-on or turn-off state,
The switch control unit includes a timer that measures the elapsed time after the operation of the first and second switches, and when the elapsed time reaches a predetermined return time TR, the magnitude comparison of the receiving voltage VR and the threshold voltage VF is performed again. Thus, the first and second switches are repeatedly controlled, but the return time TR is set shorter than the failure determination time TF of the overcurrent protection circuit,
The overcurrent protection circuit outputs a stop signal Soff when the overcurrent receiving voltage VR rises after the failure determination time (TF) has elapsed, and the supply current IS exceeds the threshold current IF over a predetermined failure determination time TF. Non-contact power supply system, characterized in that to stop the power supply.

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