JP2022086784A - High-frequency inverter, rectification circuit, and wireless power transmission system - Google Patents

Abstract

To provide an inverter circuit and a rectification circuit that can output a constant voltage or a constant current, and a wireless power transmission system including these.SOLUTION: An inverter circuit 100 includes: a switching circuit 10 including a switching element 13; and a passive circuit 30 for converting an output impedance of the switching circuit. The passive circuit sets, as a reference impedance, the output impedance when a switching voltage determined based on a set value and a structure of each element provided in an output side circuit including the switching circuit and an actual load 21 achieves ZVS and ZVDS, converts the output impedance in the actual load into the reference impedance, and converts the output impedance so that the switching voltage is in the range of achieving ZVS in the varying range of the load. The rectification circuit has a structure of inverting the inverter circuit. A wireless power transmission system is formed by coupling the inverter circuit and the rectification circuit with a coupler.SELECTED DRAWING: Figure 1

Description

The present invention relates to a high frequency inverter and a rectifier circuit that can output a constant voltage or a constant current even when the load resistance fluctuates, and a wireless power transmission system using these.

High frequency inverters have been adopted for induction heaters, plasma generators or wireless power transfer due to their high efficiency and high power. High-output and high-efficiency inverters are caused by achieving zero voltage switching (ZVS) and zero voltage derivative switching (ZVDS), as in class E inverters. However, since the class E inverter is realized with the load resistance assumed by the above ZVS and ZVDS, if the load resistance fluctuates, ZVS is not achieved and the efficiency is lowered. rice field. Therefore, an inverter method that achieves ZVS at a constant voltage (CV) output has been developed (see Non-Patent Document 1).

Japanese Unexamined Patent Publication No. 2020-010414 Japanese Unexamined Patent Publication No. 2015-023686 Japanese Unexamined Patent Publication No. 2013-013288

R.E.Zulinski and K.J.Grady, “Load-independent class E power inverter. I. Theoretical development”, IEEE Trans. Circuits Syst. I, vol. 37, No.8, pp.1010-1018, Aug. 1990.

The technique disclosed in Non-Patent Document 1 described above achieves ZVS in an inverter output by a constant voltage, but its design theory is complicated, and a voltage is generated when converting a DC voltage source to a high frequency voltage. The conversion ratio had to be large. Therefore, it was not practical. Therefore, a method has been proposed in which ZVS is achieved in a high-frequency switching circuit by using two switching elements and correcting the dead time from the off state of one switching element to the on state of the other switching element. (See Patent Document 1).

The technique disclosed in Patent Document 1 provides a control circuit including a capacitor capable of charging and discharging, turns off two switching elements when the capacitor voltage reaches the upper limit set voltage, and sets the capacitor voltage to the lower limit set voltage. In this case, one or the other switching element is alternately turned on, and a control unit for that purpose is required. Further, a correction unit for increasing the amount of discharge per unit time in the discharge period for discharging the capacitor to quickly set the capacitor voltage to the lower limit setting voltage is also required. However, the above switching circuit has not reached the point where ZVS is achieved when the load resistance fluctuates.

On the other hand, depending on the type of load, a switching power supply device capable of obtaining a constant voltage output has been developed where a constant voltage power supply or a constant current power supply is desired (see Patent Document 2). A current power supply device has also been developed (see Patent Document 3).

The technique disclosed in Patent Document 2 controls the output voltage of the boost converter, and corrects an error between the input voltage and the measured value (detection signal) of the output voltage when the input voltage is converted into a predetermined voltage. As a result, it was configured to convert to a predetermined output voltage. Therefore, the above technique is a switching power supply device including a boost converter, and cannot be applied to a class E inverter or a rectifier circuit.

Further, the technique disclosed in Patent Document 3 is a constant current circuit having a switch element, in which the switch element is controlled by a control unit according to the drain current of the switch element, and an object thereof is to suppress an output current ripple. It is something to do. Therefore, the above technique cannot be applied to a class E inverter or a rectifier circuit.

The present invention has been made in view of the above points, and an object thereof is to provide an inverter circuit and a rectifier circuit capable of outputting a constant voltage or a constant current even when a load resistance changes, and these. Is to provide a wireless power transmission system using.

Therefore, the present invention relating to a high-frequency inverter circuit is a high-frequency inverter circuit that supplies electric power with a constant voltage or a constant current to a load having a fluctuating load resistance, and a switching element that is switched by a predetermined duty ratio and this switching. A switching circuit including an output capacitor connected in parallel to the element and a passive circuit for converting the output impedance of the switching circuit are provided, and the passive circuit is provided in each of the switching circuit and the output side circuit including the actual load. The switching voltage determined based on the configuration and set value of the element uses the output impedance when achieving ZVS and ZVDS as the reference impedance, converts the output impedance in the actual load to the reference impedance, and changes the load. It is characterized in that the output impedance is converted so that the switching voltage is within the range in which ZVS is achieved within the range.

According to the above configuration, the DC voltage can be converted into a high-frequency AC voltage and output by operating the switching element, but the switching voltage at this time rises in the off state and then falls. , It is preferable that the voltage is zero (V) at the moment when the switch is switched on (achieving ZVS), and it is more preferable that the slope of the voltage change curve is zero (achieving ZVDS). Is. This is the same even when the load resistance changes and the switching voltage changes according to the fluctuating load. Therefore, by providing the passive circuit, at least ZVS can be achieved when the load resistance fluctuates.

The passive circuit assumes an inverter (hereinafter, may be referred to as a class E inverter) whose switching voltage achieves ZVS and ZVDS in the configuration of the output side circuit including the actual load (optimal load) in advance, and then. The output impedance of the above is used as a reference impedance, and the output impedance in an actual load is converted into the reference impedance, and the output impedance within the range of the fluctuating load is converted so as to be within the range of achieving ZVS. As a result, ZVS can be achieved even when the load resistance fluctuates. At this time, an impedance parameter suitable for impedance conversion by a passive circuit is obtained, and the impedance parameter is constructed so as to satisfy the impedance parameter.

By converting the impedance to the output side circuit including the load in this way, ZVS is achieved even when the load resistance fluctuates. Therefore, the switching voltage is measured at the timing when the switching element is switched from the off state to the on state. Is zero (V), and switching loss can be significantly reduced. Since the switching loss is small, it can be a constant voltage source when it is output as an AC voltage source, and it can be a constant current source when it is output as an AC current.

In the invention of the above configuration, the passive circuit is an impedance capable of impedance conversion from the real axis fluctuation geodesic of the load drawn on the Smith chart to the ZVS geodesic that achieves the ZVS drawn on the Smith chart. The parameters can be obtained and constructed as a circuit satisfying the impedance parameters.

Here, the geodetic line is a line connecting the shortest distances of two points (geometric length by Poancare measurement using non-Euclidean geometry), and may be a straight line, a circle, or an arc. .. Impedance conversion can be Mobius transformation, which converts from a circle to a circle, but a straight line can be regarded as a circle with a radius of ∞ and converted. The actual axis fluctuation geodesic of the load is the ZVS geodesic of 0Ω to ∞Ω when a constant voltage is output at an impedance value in the range of 0Ω to ∞Ω including the impedance that achieves ZVS and ZVDS at the optimum load. To output a constant current, the impedance parameters for converting ∞Ω to 0Ω to the ZVS geodesic are obtained. Therefore, although the impedance parameters are different between the case of constant voltage output and the case of constant current output, a passive circuit having a circuit configuration satisfying these parameters is provided.

According to the above configuration, when either constant voltage or constant current is selectively output, an appropriate passive circuit can be provided according to the selected output. Regarding constant current output, when focusing on switching current, it is known to reduce switch loss by zero current switching (ZCS), but here, the switch is used for the purpose of outputting constant current. It is decided to obtain the impedance parameter that achieves ZVS while paying attention to the voltage. As a result, a constant current can be output even when the load fluctuates.

The present invention relating to a rectifying circuit is a rectifying circuit that rectifies AC power supplied by a constant voltage or a constant current and outputs DC as a constant voltage or a constant current to a load having a fluctuating load resistance. A switching circuit including a switching element that is switched by a predetermined duty ratio while adjusting the phase with the AC voltage input from the source, an output capacitor connected in parallel to the switching element, and an input impedance to the switching circuit. In the passive circuit, the rising voltage of the switching voltage determined based on the configuration and set value of each element provided in the switching circuit and the output side circuit including the actual load is ZVS and ZVDS. The input impedance at the time of achievement is set as the reference impedance, the input impedance in the actual load is converted to the reference impedance, and the falling voltage of the switching voltage is within the range of achieving ZVS within the range of the fluctuating load. It is characterized in that it converts the input voltage as described above.

According to the above configuration, it is possible to rectify the supplied AC voltage source by operating the switching element with a suitable duty ratio. At this time, since the falling voltage of the switch voltage does not achieve ZVS due to the fluctuation of the load of the output side circuit, a passive circuit is provided so as to achieve at least ZVS for the falling voltage. The configuration of the passive circuit is the same as that of the passive circuit in the high-frequency inverter circuit described above, but basically, the configuration of the switching element, the output capacitor, and the passive circuit is also symmetrical to that of the inverter circuit. It is built to be. This is because the achievement of ZVS in the inverter circuit was an event when the switching voltage converged to zero (V), whereas in the rectifier circuit, it was an event at the falling voltage of the switching voltage. be. By providing the passive circuit configured in this way, the rectified voltage or current becomes a constant voltage or a constant current.

Then, in the invention of the above configuration, the passive circuit is an impedance parameter capable of impedance conversion from the real axis fluctuation geodesic of the load drawn on the Smith chart to the ZVS geodesic that achieves the ZVS drawn on the Smith chart. It can be assumed that the circuit is constructed as a circuit satisfying the impedance parameter. This is the same as in the case of an inverter circuit, and when either constant voltage or constant current is selectively output as DC after rectification, an appropriate passive circuit may be provided according to the selected output. can.

In the invention of each of the above configurations, a control unit for controlling the switching operation of the switching element is further provided, and the control unit has a cycle of an input voltage or an input current when the input impedance is converted by the passive circuit. It is possible to control the switching operation while correcting the phase difference between the two.

According to the above configuration, the phase of the electric power input to the switching element changes due to the action of the passive circuit or the like, so that the phase difference can be corrected by the control unit. ..

In the present invention relating to a wireless power transmission system, a coupler provided between the two circuits is provided with a high-frequency inverter circuit having any of the above configurations as a power feeding side and a rectifier circuit having one of the above configurations as a receiving side. It is characterized by being prepared.

According to the above configuration, the DC voltage source can be output as a high-frequency constant voltage or constant current by the inverter circuit, and this can be transmitted to the power receiving side via the coupler as the supply side. On the other hand, on the power receiving side, the power supplied as a high-frequency constant voltage or constant current can be rectified by the constant voltage or constant current and supplied to the load. As the coupler, a magnetic field coupling method or an electric field coupling method can be used, and a transformer or a gyrator constructed can be used, but the type and configuration thereof are not questioned here. ..

According to the present invention, in both the high-frequency inverter circuit and the rectifier circuit, the switching voltage achieves at least ZVS even when the load resistance changes, so that the output voltage or the output current is stable. , Can be output as a constant voltage or constant current.

Further, the wireless power transmission system using these enables wireless transmission while converting the DC voltage source into a constant voltage or a constant current, and the efficiency is increased by the operation of the phase-adjusted switching element in the rectifier circuit. Good power transmission will be realized.

It is explanatory drawing which shows the embodiment which concerns on the high frequency inverter circuit. It is a figure explaining the design method, (a) shows a class E inverter, (b) shows a Smith chart. It is a figure explaining the design method, (a) shows a two-terminal pair circuit, (b) shows a conversion example of a geodesic. It is a figure which shows the impedance parameter for a constant voltage output in a high frequency inverter circuit, (a) is a Smith chart, (b) shows an example of a T-type circuit. It is a figure which shows the impedance parameter for a constant current output in a high frequency inverter circuit, (a) is a Smith chart, (b) shows an example of a T-type circuit. It is explanatory drawing which shows the embodiment which concerns on the rectifier circuit. It is explanatory drawing which shows the embodiment which concerns on the wireless power transmission system. (A) is a diagram showing an embodiment of a high-frequency inverter circuit for constant voltage output, and (b) is a diagram showing an embodiment of a high-frequency inverter circuit for constant current output. It is a graph which shows the simulation result which concerns on the Example of the high frequency inverter circuit, (a) is only the class E inverter, (b) is for constant voltage output, (c) shows the result by the high frequency inverter circuit for constant current output. .. It is a graph which shows the result of having measured the switching voltage (shunt capacitor voltage). (A) is a diagram showing an example of a rectifier circuit for constant voltage output, and (b) is a graph showing a simulation result. (A) is a diagram showing another embodiment of a rectifier circuit for constant voltage output, and (b) is a graph showing a simulation result. (A) is a diagram showing an example of a rectifier circuit for constant current output, and (b) is a graph showing a simulation result. (A) is a diagram showing another embodiment of a rectifier circuit for constant current output, and (b) is a graph showing a simulation result. It is a figure which shows the Example of the wireless power transmission system. It is a graph which shows the simulation result in the Example of a wireless power transmission system.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<Structure of high frequency inverter circuit>
FIG. 1 shows an outline of an embodiment of the present invention relating to a high frequency inverter circuit. The high-frequency inverter circuit 100 shown in FIG. 1 has a passive circuit (circuit network) 30 configured between the switching circuit 10 and the load-side circuit 20.

The switching circuit 10 is parallel to the input inductor 12 connected to the positive side of the DC voltage source 11, the switching element 13 connected in parallel to the DC voltage source 11 and switched by a predetermined duty ratio, and the switching element 13. It is configured to include an output capacitor 14 connected to the power transmission side wiring and a series LC resonance filter 15 connected to the transmission side wiring.

In the switching element 13, the on state and the off state are operated by the cycle controlled by PWM, and the typical duty ratio is 1/2 of the cycle T. Therefore, in the present embodiment. The duty ratio is set to 1/2 of the period T. A transistor, MOS-FET, or the like can be used for the switching element 13.

The input inductor 12 connected to the DC voltage source 11 supplies a DC current to the circuit after the switching element. Further, the series LC resonance filter 15 is an LC resonance circuit that resonates the output of the transmission side wiring, and is connected as a low-pass filter for passing only the fundamental wave and suppressing harmonics. If the passive circuit has a low-pass effect, the series LC resonance filter 15 can be omitted.

The output capacitor 14 accumulates electric charges when the switching element 13 is in the off state and discharges the electric charges when the switching element 13 is in the on state, but discharges all the electric charges accumulated before the switching element 13 shifts from the off state to the on state. By doing so, ZVS can be achieved. At this time, ZVDS can be achieved by designing so that the emission of electric charge that changes with the passage of time, that is, the amount of change in voltage (switching voltage) (slope on the graph) becomes zero. When ZVS is achieved, the switching loss is reduced, and when ZVDS is achieved, the harmonics of the switching voltage are expected to be further reduced. Therefore, the inverter circuit that achieves both ZVS and ZVDS is class E. It is distinguished from other inverter circuits by calling it.

In order for the voltage (switching voltage) of such an output capacitor 14 to achieve ZVS and ZVDS, the output impedance _Z0 in the switching circuit 10 must be set to a predetermined value. At that time, the output impedance Z ₀ is set on the premise that the load 21 is the optimum load, or the optimum load is set according to the value of the output impedance Z ₀ set by the configuration of the switching circuit 10. The load 21 calculated by that value will be used.

However, in any of the above cases, when the resistance value of the load 21 fluctuates, ZVS and ZVDS cannot be achieved. That is, when the resistance value of the load 21 is smaller than the optimum value, the charge stored in the output capacitor 14 is released quickly, and when the switching element 13 is turned on, the output voltage (switching voltage) becomes negative, and conversely. This is because when the resistance value of the load 21 is larger than the optimum value, all the charges are not discharged and the output voltage (switching voltage) becomes a positive state.

Therefore, in the present embodiment, a passive circuit (circuit network / network) 30 is provided between the switching circuit 10 and the load side circuit 20, and the passive circuit 30 outputs even when the load 21 fluctuates. ZVS is achieved so that the voltage (switching voltage) of the capacitor 14 becomes zero (V) when the switching element 13 is turned on, and all the electric charges accumulated in the output capacitor 14 are discharged. There is.

<Circuit design method>
The method for designing the network of the passive circuit 30 will be described below.
First, in a general class E inverter as shown in FIG. 2A, the output current (i ₁ (t)) and the voltage (v ₁ (t)) of the output capacitor (shunt capacitor) are expressed by the following equations. be able to.

Here, the following equation can be obtained by harmonic balance analysis based on the above equation.

Then, the following equation can be obtained under the conditions of ZVS and ZVDS with t = T / 2.

Here, by substituting the above equation (6) into the above equations (4) and (5) and deleting θ, the following equations (7) and (8) can be obtained.

At this time, the impedance (Z ₀ = R ₀ + jX ₀ ) satisfying the above (7) and (8) becomes two arcuate curves on the Smith chart as shown in FIG. 2 (b), and both curves. Cross at the point Z ₀₀ . This intersecting point Z ₀₀ is shown by the following equation. The arc-shaped curve as described above is called a geodetic station in hyperbolic geometry. Here, the above equation (7) represents a ZVS geodesic line, and the above equation (8) represents a ZVDS geodesic line.

The arcuate curve (ZVS geodesic or ZVDS geodesic) on such a Smith chart changes due to actual load fluctuations, but at that time, the actual axis load fluctuation geodesic is converted to the ZVS geodesic. be able to. The transformation at this time is due to the Mobius transformation. Since the Mobius transformation can map from a circle to a circle and the straight line can be regarded as a circle with a radius of ∞, it is possible to transform the straight line into a circle (or an arc-shaped curve).

Here, in a two-terminal pair circuit as shown in FIG. 3A, a general black box model is assumed when the load fluctuates. This black box is supposed to convert the load impedance Z _L into the input impedance Z ₀ . The input impedance Z ₀ converted by the impedance parameters Z ₁₁ , Z ₁₂ , Z ₂₁ , and Z ₂₂ in the black box at this time can be expressed by the following equation.

Further, when the black box is lossless and is composed of the reciprocal component, the above equation (10) can be expressed as the following equation.

Then, as shown in FIG. 3B, the input impedance Z ₀ converted as described above converts the load impedance Z _L from the real axis load fluctuation geodesic to the ZVS geodesic, and each geodesic line. When the impedances of three points are extracted from, each impedance becomes the following equation.

By solving the above equation, individual parameters (Z ₁₁ , Z ₂₂ , Z ₂₁ (= Z ₁₂ )) constituting the impedance parameter of the black box can be obtained. This individual parameter can be expressed by the following equation.

By substituting each value for the impedance parameter of the black box shown above, the individual parameters (Z ₁₁ , Z ₂₂ , Z ₂₁ (= Z ₁₂ )) can be found, and the specific circuit network of the passive circuit 30 can be found. Can be designed.

<Passive circuit design for constant voltage (CV) output>
Next, a method for designing the passive circuit 30 having a constant voltage output (hereinafter, may be abbreviated as CV output) will be described with reference to the above design method. As described above, the equation representing the ZVS geodesic line was as shown in the above equation (7). In this equation (7), when R ₀ = 0, X ₀ becomes the following equation (18), and the following equations (19) and (20) representing Z _0a and Z _0b . The intersection (Z ₀₀ ) of the ZVS geodesic line and the ZVDS geodesic line is the above equation (9).

On the other hand, as shown in FIG. 4A, for the loads Z _La , Z _Lb , and Z _L0 on the actual axis, the horizontal axis of the Smith chart indicates the load resistance _RL , which is used for geodesic measurement of the load resistance. It can be regarded as a line, and both ends are 0 and ∞. Then, the load resistance _RL becomes an arbitrary point in the range of 0 to ∞, and by setting Z _La = 0, Z _Lb = ∞, and Z _L0 = _RL 0, respectively, an impedance parameter for constant voltage output can be obtained. Can be done. By substituting these calculation formulas into the above formulas (15) to (17), individual parameters (Z ₁₁ , Z ₂₂ , Z ₂₁ (= Z ₁₂ )) can be obtained. The result is as shown in the following equation.

Further, since Z ₁₁ = jX ₁₁ , Z ₂₂ = jX ₂₂ , and Z ₂₁ = jX ₂₁ , the reactances X ₁₁ , X ₂₁ , and X ₂₂ , respectively, can be shown by the following equations.

Then, when the T-type circuit shown in FIG. 4 (b) is configured, when the above equations (22) to (24) are substituted for the reactance values in FIG. 4 (b), the polarity of X ₂₁ and the range of _{RL 0} are determined. Four different circuits can be configured. Further, the range of RL0 depends on _{ωC s} . The table below shows these four types of circuit configurations.

Therefore, with the above four types of circuit configurations, ZVS can be achieved in any case of the load resistance _RL . Then, when the load resistance _RL = RL0, ZVS and _ZVDS are achieved.
Further, by substituting the above equations (22) to (24) into the above equation (11), the following equation can be obtained.

Therefore, the current resonance width I ₁ can be obtained by the above equation (25) and the above equations (3) to (5), and the following equation is obtained.

Further, if the voltage resonance width V ₂ of the output voltage is obtained from the above equation (25) and the impedance parameter, the following equation is obtained.

As is clear from the above equation (27), since the voltage amplitude width V ₂ of the output voltage is constant regardless of the load resistance _RL , a constant voltage output can be achieved.

<Passive circuit design for constant current (CC) output>
Next, a method of designing a passive circuit 30 having a constant current output (hereinafter, may be abbreviated as CC output) will be described. The design method for constant current output is the same as for constant voltage output, where X ₀ is the equation (18) and Z _0a and Z _0b are the equations (19) and (20), ZVS. The intersection (Z ₀₀ ) of the geodesic line and the ZVDS geodesic line is the above equation (9).

Even in the case of constant current output, as shown in FIG. 5A, the horizontal axis of the Smith chart indicates the load resistance _RL for the loads Z _La , Z _Lb , and Z _L0 on the actual axis. This is regarded as a geodesic line of load resistance as in the case of constant voltage output, and both ends are 0 and ∞.

Here, the load resistance _RL is an arbitrary point in the range of 0 to ∞, but when obtaining the impedance parameter in the case of constant current output, both ends of the geodesic of the load resistance are “0” and “∞”. Is the opposite value to the constant voltage output. That is, by setting Z _La = ∞, Z _Lb = 0, and Z _L0 = _RL0 , the impedance parameter for constant current output can be obtained. By substituting these calculation formulas into the above formulas (15) to (17), individual parameters (Z ₁₁ , Z ₂₂ , Z ₂₁ (= Z ₁₂ )) can be obtained. The result is as shown in the following equation.

Further, since Z ₁₁ = jX ₁₁ , Z ₂₂ = jX ₂₂ , and Z ₂₁ = jX ₂₁ , the reactances X ₁₁ , X ₂₁ , and X ₂₂ , respectively, can be shown by the following equations.

Similar to the case of constant voltage output, the above reactance can be obtained by substituting the above equations (29) to (31) for the reactance in the figure when the T-type circuit shown in FIG. 5 (b) is configured. Four different circuits can be configured depending on the polarity of X ₂₁ and the range of _RL0 . The same applies to the fact that the range of RL0 depends on _{ωC s} . The table below shows these four types of circuit configurations.

In the case of the above four types of circuit configurations, ZVS can be achieved in any case of the load resistance _RL . Then, when the load resistance _RL = RL0, ZVS and _ZVDS are achieved. This point is the same as in the case of constant voltage output.

Further, by substituting the above equations (22) to (24) into the above equation (11), the following equation (32) can be obtained, and the equations (32) and the above equations (3) to (5) can be used. The current resonance width I ₁ can be obtained as the following equation (33). Further, if the current resonance width I ₂ of the output current is obtained from the equation (33) and the impedance parameter, the following equation (34) is obtained.

As is clear from the above equation (34), since the current amplitude width I ₂ of the output current is constant regardless of the load resistance _RL , a constant current output can be achieved.

<Summary of high frequency inverter circuit>
As described above, the class E switching circuit 10 that achieves ZVS and ZVDS at the optimum load is configured, and the output impedance for the optimum load is used as the basis, and the output impedance for the fluctuating actual load is converted into the basic impedance. A constant voltage output or a constant current output can be achieved even when the load resistance _RL of the actual load is variously changed. At this time, according to the design method as described above, the passive circuit 30 having a desired impedance parameter can be provided for each of the case of constant voltage output and the case of constant current output.

<Rectifier circuit>
FIG. 6 shows an outline of an embodiment of the present invention relating to a rectifier circuit. The rectifier circuit 200 shown in FIG. 6 has a configuration in which the above-mentioned high-frequency inverter circuit (FIG. 1) is inverted. That is, a passive circuit (circuit network) 30 is provided between the input side circuit (power supply circuit) 40 and the rectifying switching circuit 50.

The switching circuit 50 includes a switching element 53 and an output capacitor (shunt capacitor) connected in parallel to the switching element 53, and a series LC resonance filter 55 is provided in the power transmission side wiring. Further, the load 60 is provided with an output inductor 52 in series. In the rectifier circuit 220 as well, the series LC resonance filter 55 can be omitted if the passive circuit is to have a low-pass effect.

In the switching element 53, the on state and the off state are operated by the cycle controlled by PWM, and the typical duty ratio is 1/2 of the cycle T. Therefore, in the present embodiment. The duty ratio is set to 1/2 of the period T. However, as will be described later, since a phase difference may occur between the voltage and the power supply voltage, the phase is controlled to be adjusted. As the switching element 53, a transistor, a MOS-FET, or the like can be used.

In the rectifier circuit using the switching element 53, the alternating current supplied from the alternating current voltage source is converted into direct current by the switching operation by the switching element 53. Then, the switching voltage rises at the timing when the switching element 53 switches from the on state to the off state. The rising voltage at this time rises from 0 (V) when ZVS and ZVDS are achieved.

Therefore, in the rectifier circuit 200 using the switching element 53, as in the case of the inverter circuit, even if the load fluctuates by providing the passive circuit 30 configured with a predetermined impedance parameter. ZVS can be achieved. Then, a constant voltage or a constant current can be output by adjusting the impedance parameter.

<Rectifier circuit design method>
The design method of the rectifier circuit is the same as that of the high frequency inverter circuit described above. That is, as shown in FIG. 6, the configuration of each element constituting the rectifier circuit 200 is an inverse configuration in which the inverter circuit is inverted. With such a reverse configuration, the voltage in each element (element or the like) can be considered to be the same as in the case of the inverter circuit. Each impedance or reactance at that time can be calculated in the same manner. The same applies to the movement of each point on the geodesic line. Therefore, the impedance parameter can be obtained by the same design method.

Here, when the load condition and the output condition are the same as those of the inverter circuit, the internal configuration of the passive circuit 30 can also be reversed. For example, when an LLC circuit is adopted as a T-type circuit, a left-right inverted CLL circuit can be configured. The inductance or capacitance of each element at that time can be set in the same manner. On the other hand, when the load conditions and the like are different, different circuit configurations can be used while using the same design method. For example, when the inverter circuit has a CV output but the rectifier circuit outputs a CC, the passive circuit 30 inevitably has a different configuration. Even in this case, the design method can be the same as that of the above-mentioned inverter circuit.

Therefore, since the design method will be the same, the explanation will be omitted here. However, in the case of constant voltage output and constant current output, the impedance parameters are obtained by the same method to configure a passive circuit. It becomes a thing. However, since a phase difference occurs between the input voltage and the drive signal of the switching element, it is necessary to fix this phase difference to an appropriate value. This phase difference determines the impedance parameter in the passive circuit by the polarity of a specific reactance X ₂₁ among the individual parameters. The reactance X ₂₁ is the same as the reactance in the inverter circuit.

For example, in the case of inputting an AC constant voltage and DC voltage CV output, the phase difference when X ₂₁ > 0 is + 180 °, and the phase difference when X ₂₁ <0 is 0 °. Further, in the case of DC voltage CC output, the phase difference when X ₂₁ > 0 is −90 °, and the phase difference when X ₂₁ <0 is + 90 °.

<Wireless power transmission system>
Next, the wireless power transmission system will be described. By using the above-mentioned high-frequency inverter circuit and rectifier circuit, it is possible to construct a wireless power transmission system capable of producing CV output or CC output while achieving ZVS in each circuit.

FIG. 7 illustrates an embodiment of a wireless power transmission system. As shown in this figure, in a wireless power transmission system, a high frequency inverter circuit is composed of a switching circuit and a passive circuit, and a rectifying circuit is also composed of a switching circuit and a passive circuit. These high-frequency inverter circuits and rectifier circuits are wirelessly coupled by a coupler.

As the coupler, an electric field coupler or a magnetic field coupler is used, and these include a transformer type and a gyrator type. The transformer method is used when the CV input is CV output or the CC input is CC output, and the gyrator method is used when the CV input is CC output or the CC input is CV output.

The high-frequency inverter circuit and the rectifier circuit configured here are as described above, and specifically, both are configured to be mutually symmetrical. That is, the configurations of the high-frequency inverter circuit and the rectifier circuit are reversed (as a symmetrical positional relationship) and arranged around the coupler. Therefore, for example, the high-frequency inverter circuit may have the configuration shown in FIG. 1, and the rectifier circuit may have the configuration shown in FIG. 6 which is coupled by a coupler.

By the way, the high frequency inverter circuit converts direct current to high frequency, the coupler wirelessly transmits without converting high frequency, and the rectifier circuit converts high frequency to direct current. In these conversions, the CV input is CV. When outputting, or when CC input is CC output, it is recognized as a transformer characteristic. On the other hand, when the CV input is CC-output or the CC input is CV-output, it is recognized as a gyrator characteristic. Therefore, when both the high-frequency inverter circuit and the rectifier circuit have transformer characteristics, or when both have gyrator characteristics, the impedance parameters of the passive circuit are configured in the same manner, and each element is inverted (symmetrical). can do. On the other hand, when one has a transformer characteristic and the other has a gyrator characteristic, the impedance parameters of the passive circuit are different, so that individual passive circuits are configured.

Even when the high-frequency inverter circuit and the rectifying circuit are inverted (arranged symmetrically), the phase difference between the output voltage of the high-frequency inverter (input voltage to the rectifying circuit) and the drive signal of the switching element in the rectifying circuit. As described above, this phase difference must be fixed to an appropriate value. Therefore, in order to control the drive signal of the switching element of the rectifier circuit, the phase is controlled by means as exemplified in FIGS. 7A to 8B.

In order to demonstrate that the CV output characteristic or the CC output characteristic can be exhibited by the configuration as shown above, an experiment was conducted on a specific circuit configuration. The experiment was a simulation using a simulator, and each configuration and experimental results were as follows.

<Example of high frequency inverter circuit>
As a circuit for CV output in the high frequency inverter, the configuration as shown in FIG. 8A was designed. The specifications of the switching circuit in this case are as shown in the table below, and the passive circuit is a T-type LLC circuit and is set as shown in the table below. Although the load resistance is set to 50Ω, this corresponds to the optimum load for achieving ZVS and ZVDS in the class E inverter circuit without the passive circuit.

Further, as a circuit for CC output in the high frequency inverter, the configuration as shown in FIG. 8B was designed. The specifications of the switching circuit in this case are the same as those of the CV output, and the passive circuit is a T-type LCL circuit and is set as shown in the table below.

Regarding the high-frequency inverter circuit for CV output and the high-frequency inverter circuit for CC output, the switching voltage (shunt capacitor voltage) and the case where the load resistance is changed (25Ω and 100Ω) and when the load resistance is changed, respectively. Changes in the output voltage and output current over time were detected for one cycle from the off state to the on state of the switching element. For reference, each voltage and current were detected in the same manner for a simple class E inverter without a passive circuit.

These results are shown in FIG. Note that (a) is only a class E inverter, (b) is a high-frequency inverter circuit provided with a passive circuit for enabling CV output, and (c) is a high-frequency circuit provided with a passive circuit for enabling CC output. The result by the inverter circuit is shown. As shown in these figures, according to the switching voltage (shunt capacitor voltage), ZVS and ZVDS are achieved in the circuits of each configuration when the load resistance is the optimum load (50Ω). In the case of only the class E inverter, ZVS is not achieved when the load resistance fluctuates, but in the high frequency inverter circuit for CV output and CC output, ZVS is achieved.

Further, in the inverter circuit for CV output, the amplitude of the output voltage does not change even when the load resistance is changed, and a constant voltage is output. On the other hand, in the inverter circuit for CC output, the amplitude of the output current does not change even when the load resistance is changed, and a constant current is output.

In addition, in order to confirm the achievement status of ZVS in the range of load resistance of 5Ω to 500Ω (1/10 to 10 times the optimum load), the timing at which the switching element switches from the off state to the on state for the above three types of circuits. The switching voltage (shunt capacitor voltage) in was measured. The results are shown in FIG. In the figure, "G2G" indicates a configuration provided with the above-mentioned passive circuit, and "Conventional" indicates a class E inverter circuit as a conventional configuration.

As is clear from the results shown in FIG. 10, in each circuit for CV output and CC output, the timing at which the switching element is turned on at any load resistance so as to match the theoretical ZVS situation. In, the switching voltage (shunt capacitor voltage) indicates 0 (V). With reference to this result, it is determined that the high frequency inverter circuit configured as in this embodiment enables CV output or CC output in a wide range without being limited to 25Ω and 100Ω as described above. can do.

<Example of rectifier circuit>
As a circuit for CV output in the rectifier circuit, the configuration as shown in FIG. 11A was designed. In the circuit shown in this figure, the specifications when the polarity of the impedance parameter X ₂₁ described above is positive and the polarity of the impedance parameter X ₂₁ is positive are as shown in the table below. As shown in the table below, the input high frequency voltage amplitude was designed to be 51.6V (6.78MHz), the output voltage was designed to be 48V, and the optimum load was designed to be 86.6Ω. The passive circuit in this case was a T-type CLL circuit, and each element was set as shown in the table below. Since the input voltage is a high frequency (RF) voltage having a frequency of 6.78 MHz, the switching frequency by the switching element is set to 6.78 MHz and the phase difference is fixed at 180 °.

FIG. 11B shows the experimental results of the rectifier circuit having the above configuration. As shown in this figure, by operating the switching element while fixing the phase to 180 ° with respect to the high frequency (RF) input voltage, the falling voltage of the switching voltage (shunt capacitor voltage) achieves ZVS. rice field. As a result, the DC output voltage became a constant voltage.

Next, a rectifier circuit was designed for CV output when the polarity of the impedance parameter X ₂₁ is negative. The configuration is shown in FIG. 12 (a). The specifications of the switching circuit in this case are the same as those in Table 5 above, and only the passive circuit is changed. The passive circuit was a T-type LCL circuit and was set as shown in the table below.

FIG. 12B shows the experimental results of the rectifier circuit having the above configuration. When the polarity of the impedance parameter X ₂₁ is negative, there is no phase difference with respect to the high frequency (RF) input voltage. Therefore, as shown in the figure, the switching voltage is obtained by operating the switching element without adjusting the phase. The falling voltage of (shunt capacitor voltage) achieved ZVS. As a result, the DC output voltage became a constant voltage.

On the other hand, as a circuit for CC output, a configuration as shown in FIG. 13A was designed. This illustrates the case where the polarity of the impedance parameter X ₂₁ is positive. The specifications of this circuit are as shown in the table below. The input high frequency voltage amplitude was set to 51.6V (6.78MHz) and the optimum load was designed to be 86.6Ω, which is the same as the case of CV output, and the output current was designed to be 0.55A. The passive circuit in this case was a T-type LCL circuit, and each element was set as shown in the table below. The switching frequency of the switching element was set to 6.78 MHz, and the phase difference was fixed at −90 °.

FIG. 13B shows the experimental results of the rectifier circuit having the above configuration. As shown in this figure, by operating the switching element while fixing the phase to -90 ° with respect to the high frequency (RF) input voltage, the falling voltage of the switching voltage (shunt capacitor voltage) achieves ZVS. became. As a result, the DC output current became a constant current.

Next, a rectifier circuit was designed for CC output when the polarity of the impedance parameter X ₂₁ is negative. The configuration is shown in FIG. 14 (a). The specifications of the switching circuit in this case are the same as those in Table 7 above, and only the passive circuit is changed. The passive circuit was a T-type CLC circuit and was set as shown in the table below.

FIG. 14B shows the experimental results of the rectifier circuit having the above configuration. When the polarity of the impedance parameter X ₂₁ is negative, the falling voltage of the switching voltage (shunt capacitor voltage) is set by operating the switching element while correcting the phase of + 90 ° with respect to the high frequency (RF) input voltage. It became the one to achieve ZVS. As a result, the DC output current became a constant current.

<Example of wireless power transmission system>
As a circuit for constructing a wireless power transmission system, a configuration as shown in FIG. 15 was designed. Basically, it is composed of an inverter circuit, a coupling circuit, and a rectifier circuit. The specifications of the inverter circuit are as shown in Table 9 below, and the rectifier circuit is as shown in Table 10 below. The coupler has a configuration as shown in FIG. 15, and the specifications are shown in Table 11 below. The input voltage was set to 100 V by a constant voltage source, and this was set to a constant voltage output by an inverter circuit. The coupler adopts a gyrator method and outputs a constant voltage input with a constant current. Furthermore, the rectifier circuit is designed to output a constant current input at a constant voltage. At this time, the assumed output voltage was designed as a constant voltage of 100 V, and the result is shown in FIG.

From the results in FIG. 16, it was found that the output from the inverter circuit was a high frequency constant voltage of 300 V, and a high frequency constant current of 600 mA was input to the rectifier circuit via the coupler. Further, in the rectifier circuit, it was found that the high frequency constant current 600mA is rectified and a DC constant voltage of 100V is output.

<Summary>
As described above, for both the high-frequency inverter circuit and the rectifier circuit, it is possible to output CV or CC even when the load fluctuates by appropriately configuring the passive circuit. Furthermore, a wireless power transmission system can be constructed by combining these while using them with a coupler. In this wireless power transmission system, CV output or CC output is realized in a high-frequency inverter circuit, and then wireless. It is wirelessly transmitted by the coupler, and finally, CV output or CC output by direct current is possible regardless of the load by the rectifier.

Therefore, it is possible to supply desired electric power to various loads. In other words, stable power supply is possible for both loads that require constant voltage supply and loads that require constant current supply, and a passive circuit is provided after setting the optimum load in advance. As a result, the switching loss can be reduced against any load fluctuation.

The embodiments and examples of the present invention are as described above, but the present invention is not limited to these embodiments or examples. Therefore, it is possible to change the configuration of the above embodiment or add another configuration. For example, as the configuration of the passive circuit, a typical one is exemplified, but any circuit configuration that can obtain the impedance parameters that the passive circuit should have may be used, and other configurations may be used. Further, although an example is shown in the example, the coupler may have another configuration.

10,50 Switching circuit 11 DC voltage source 12 Input inductor 13,53 Switching element 14,54 Output capacitor (shunt capacitor)
15,55 Series LC resonance filter 20 Load circuit (output side circuit)
21,60 Load 30 Passive circuit 40 Power supply circuit (input side circuit)
52 Output inductor 100 High frequency inverter circuit 200 Rectifier circuit

Claims (8)

A high-frequency inverter circuit that supplies power with a constant voltage or constant current to a load with fluctuating load resistance.
A switching circuit including a switching element switched by a predetermined duty ratio and an output capacitor connected in parallel to the switching element.
A passive circuit that converts the output impedance of the switching circuit is provided.
In the passive circuit, the output impedance when the switching voltage determined based on the configuration and set value of each element provided in the switching circuit and the output side circuit including the actual load achieves ZVS and ZVDS is used as a reference impedance. It is characterized in that the output impedance in an actual load is converted to the reference impedance, and the output impedance is converted so that the switching voltage is within the range in which ZVS is achieved within the range of the fluctuating load. High frequency inverter circuit. The passive circuit obtains an impedance parameter capable of impedance conversion from the real axis fluctuation geodesic of the load drawn on the Smith chart to the ZVS geodesic that achieves the ZVS drawn on the Smith chart, and satisfies the impedance parameter. The high-frequency inverter circuit according to claim 1, which is constructed as a circuit. A rectifier circuit that rectifies AC power supplied by a constant voltage or constant current and outputs DC as a constant voltage or constant current to a load with fluctuating load resistance.
A switching circuit including a switching element that is switched by a predetermined duty ratio while adjusting the phase with the AC voltage input from the AC voltage source, and an output capacitor connected in parallel to the switching element.
A passive circuit that converts the input impedance to the switching circuit is provided.
The passive circuit is based on the input impedance when the rising voltage of the switching voltage determined based on the configuration and set value of each element provided in the switching circuit and the output side circuit including the actual load achieves ZVS and ZVDS. Impedance, which converts the input impedance in the actual load to the reference impedance, and converts the input impedance so that the falling voltage of the switching voltage is within the range of achieving ZVS within the range of the fluctuating load. A rectifying circuit characterized by being. The passive circuit obtains an impedance parameter capable of impedance conversion from the real axis fluctuation geodesic of the load drawn on the Smith chart to the ZVS geodesic that achieves the ZVS drawn on the Smith chart, and satisfies the impedance parameter. The rectifying circuit according to claim 3, which is constructed as a circuit. Further, a control unit for controlling the switching operation of the switching element is provided.
The control unit controls the switching operation while correcting the phase difference generated between the cycle of the input voltage or the input current when the input impedance is converted by the passive circuit. Rectifier circuit. A wireless power transmission system characterized in that the high frequency inverter circuit according to claim 1 or 2 is used as a power feeding side and is coupled to a rectifier circuit via a coupler. A wireless power transmission system comprising the rectifier circuit according to any one of claims 3 to 5 as a power receiving side and coupled to a high frequency inverter circuit via a coupler. The high frequency inverter circuit according to claim 1 or 2 is used as a power feeding side, and the rectifying circuit according to any one of claims 3 to 5 is used as a power receiving side, and a coupler provided between the two circuits is provided. Wireless power transmission system.

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