JP2015216739A - Power transmission apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a non-contact power transmission apparatus capable of searching and controlling the drive frequency of the inverter for improving the efficiency of the inverter while constantly maintaining the input power to the inverter.SOLUTION: The power transmission apparatus includes: an inverter 7; a control section 9; a transmission-side capacitor 10; a power transmission coil 11; an input power detection section 6; and a phase difference detection section 8 that detects a phase difference between the output voltage and the output current of the inverter 7. The control section 9 changes the drive frequency and the output duty of the inverter 7 so that the phase difference is 0 while constantly maintaining the input power to the inverter 7 on the basis of the input power to the inverter 7 and the phase difference detected by the phase difference detection section 8.

Description

  The present invention relates to a power transmission device of a non-contact power feeding system for charging an in-vehicle storage battery such as an electric car and a hybrid car from an external power feeding facility in a non-contact manner.

  A non-contact power supply system that can be charged in a non-contact manner, for example, an alternating current is supplied to a power transmission coil (power transmission unit) on a power transmission side installed in a parking lot or the like, and a power reception coil (power reception) installed on the bottom surface of the vehicle A charging device that generates an alternating current by electromagnetic induction and supplies power from a power receiving coil to a storage battery has been proposed.

  In non-contact power feeding, the output impedance of the inverter changes due to the load fluctuation on the power receiving side and the change in mutual inductance due to the positional deviation between the power transmission coil and the power receiving coil. There is a problem of lowering.

  In order to solve this problem, a technique for detecting a resistance component of a load and controlling the drive frequency of the inverter according to the resistance component of the load is disclosed (for example, Patent Document 1). In addition, a technique is disclosed in which a positional relationship between a power transmission coil and a power reception coil is detected, a mutual inductance is estimated, and a drive frequency of the inverter is controlled accordingly (for example, Patent Document 2). Further, a technique for detecting the phase difference between the output voltage and output current of the inverter and controlling the drive frequency of the inverter so as to make the phase difference zero is disclosed (for example, Patent Document 3).

JP 2002-272134 A (paragraphs [0029] to [0035], FIG. 1) Japanese Patent No. 5369669 (paragraphs [0014] to [0020], [0026], [0035], FIG. 5) JP-A-10-225129 (paragraphs [0019] to [0022], FIG. 1)

  When charging an in-vehicle storage battery with contactless power supply, it is necessary to control the input power of the inverter to be constant. However, if the drive frequency of the inverter is controlled as in the disclosed technology, fluctuations in the drive frequency of the inverter Since the input power also fluctuates, there is a problem that the input power cannot be controlled constant.

  The present invention has been made to solve the above-described problems, and is a contactless power transmission device that can search and control the inverter drive frequency to improve the inverter efficiency while keeping the inverter input power constant. The purpose is to provide.

  The power transmission device according to the present invention includes an inverter that outputs high-frequency power, a control unit that controls the inverter, a power transmission-side capacitor that is connected to the output of the inverter and that is supplied with high-frequency power, and a power transmission coil that is connected to the power transmission-side capacitor And an input power detection unit that detects the input power of the inverter, and a phase difference detection unit that detects a phase difference between the output voltage and output current of the inverter, and the control unit includes the input power and phase difference detection unit of the inverter. Based on the detected phase difference, the drive frequency of the inverter and the output duty of the inverter are changed so that the phase difference is zero while keeping the input power of the inverter constant.

  Since the power transmission device according to the present invention is configured as described above, it is possible to search and control the inverter drive frequency that improves the inverter efficiency while keeping the input power of the inverter constant.

BRIEF DESCRIPTION OF THE DRAWINGS It is a system block diagram which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is an internal block diagram which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is output duty explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference signal explanatory drawing of the inverter output which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is a wave form diagram of the output voltage and output current of an inverter at the time of input power control concerning the power transmission device of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is a control flowchart which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 1 of this invention. It is zero volt switching explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is zero volt switching explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is zero volt switching explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is zero volt switching explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is zero volt switching explanatory drawing of the inverter which concerns on the power transmission apparatus of Embodiment 1 of this invention. It is a control flowchart which concerns on the power transmission apparatus of Embodiment 2 of this invention. It is phase difference explanatory drawing of the output voltage and output current of an inverter which concern on the power transmission apparatus of Embodiment 2 of this invention.

Embodiment 1 FIG.
The first embodiment detects an inverter, a control unit that controls the inverter, a power transmission side capacitor, a power transmission coil, an input power detection unit that detects input power of the inverter, and a phase difference between the output voltage and current of the inverter. And a control unit configured to control the inverter so that the phase difference is zero based on the input power of the inverter and the phase difference between the output voltage and current while maintaining the input power of the inverter constant. The present invention relates to a power transmission device that changes drive frequency and output duty.

  1 is a system configuration diagram including a power transmission device, FIG. 2 is an internal configuration diagram of the power transmission device, and FIG. 2 is an explanatory diagram of an output duty of an inverter. Fig. 3, Fig. 7, Fig. 7, Fig. 9 to Fig. 15 illustrating the phase difference between the output voltage and output current of the inverter, Fig. 5 illustrating the phase difference signal of the inverter output, Fig. 5, Description will be made based on FIG. 6 which is a waveform diagram of output voltage and output current, FIG. 8 which is a control flowchart, and FIGS. 16 to 20 which are explanatory diagrams of zero volt switching.

  FIG. 1 shows an overall configuration of a non-contact power feeding system 100 including a power transmission device 1 according to Embodiment 1 of the present invention. The non-contact power feeding system 100 includes a ground-side power transmission device 1, a vehicle-side power reception device 2, a power supply 3 that supplies power to the power reception device 2 via the power transmission device 1, and power supplied to the power reception device 2. It is comprised with the electrical storage apparatus 4 to store.

The power transmission device 1 is installed on the ground side such as a parking lot, and is connected to a power source 3 such as a system power source and is supplied with power from the power source 3. The power transmission device 1 includes a power transmission side rectifier circuit 5 that converts AC power supplied from a power supply 3 into DC power, and an input power detection unit 6 that detects DC power from the power transmission side rectifier circuit 5, that is, input power of an inverter 7. An inverter 7 that converts DC power into high-frequency power, a phase difference detector 8 that detects a phase difference between an output voltage and an output current output from the inverter 7, a controller 9 that controls the inverter 7, and a phase difference The resonance power transmission side capacitor 10 and the power transmission coil 11 are connected to the subsequent stage of the detection unit 8.
The control unit 9 is based on the input current and voltage signal of the inverter 7 detected by the input power detection unit 6 and the phase difference signal of the output voltage and output current output from the inverter 7 detected by the phase difference detection unit 8. To control the inverter 7.
The power transmission side rectifier circuit 5 and the power transmission side capacitor 10 are appropriately described as the rectifier circuit 5 and the capacitor 10, respectively.

The power receiving device 2 includes a power receiving coil 12 for outputting high frequency power from an induction current formed by a high frequency magnetic field transmitted from the power transmitting coil 11, and a power receiving side capacitor 13 for resonance connected in parallel to the power receiving coil 12. A received-side rectifier circuit 14 that converts received high-frequency power into direct-current power, and a step-up / down converter (DC / DC converter) that converts the voltage of the direct-current power via the received-side rectifier circuit 14 and supplies the power to the power storage device 4 ) 15.
Note that the power receiving side capacitor 13 and the power receiving side rectifier circuit 14 are appropriately described as a capacitor 13 and a rectifier circuit 14, respectively.

FIG. 2 shows configurations of the input power detection unit 6, the inverter 7, the phase difference detection unit 8, and the control unit 9.
The input power detection unit 6 includes an input current detection unit 21 and an input voltage detection unit 22, and sends signals detected by the input current detection unit 21 and the input voltage detection unit 22 to the control unit 9.
The inverter 7 is a full bridge inverter.
The phase difference detection unit 8 includes an output current detection unit 23, an output voltage detection unit 24, and a phase comparator 25 that detects a phase difference from the output current and output voltage of the inverter 7.
The control unit 9 includes an arithmetic processing unit 26 having a microcomputer and a gate driver 27, for example. Based on the signal input to the arithmetic processing unit 26, the output duty of the inverter 7 is controlled by changing the signal output to the gate driver 27.

In the control unit 9, the output voltage of the inverter 7 is controlled by a phase shift method of controlling the output voltage by shifting the on / off phase of each switching element constituting the inverter 7. Further, PWM control may be performed for the control of the output voltage of the inverter 7.
In FIG. 2, an FET is used as a switching element constituting the inverter 7, but an IGBT can also be used.

  FIG. 3 is a diagram for explaining the definition of the output duty of the inverter 7. The output voltage of the inverter 7 is a rectangular wave as shown in FIG. As shown in FIG. 3, in the present invention, when the drive frequency of the inverter 7 is f, when the positive pulse width w of the output voltage rectangular wave is a half cycle 1 / 2f, the output duty of the inverter 7 is maximized at 1, The output duty is defined as 2 fw.

FIG. 4 is a diagram for explaining the definition of the phase difference θ. A phase difference θ is defined between the rise of the output voltage of the inverter 7 and the zero cross point of the output current of the inverter 7. A signal of the phase difference θ is sent from the phase comparator 25 to the control unit 9.
As shown in FIG. 4, the phase difference θ may be a positive phase difference θ or a negative phase difference θ. Two dotted arrows from the phase comparator 25 to the control unit 9 in FIG. 2 indicate that signals of positive phase difference θ and negative phase difference θ are output separately.
Further, a phase comparator that outputs only the absolute value of the phase difference θ may be used. The function and operation of the control unit 9 when outputting only the absolute value of the phase difference θ will be described in the second embodiment.

FIG. 5 is a diagram illustrating a phase difference signal sent from the phase difference detection unit 8 to the control unit 9.
The signal of the phase difference θ sent to the control unit 9 is the phase difference signal shown in FIG. 5, and a value obtained by averaging the phase difference signals is input to the arithmetic processing unit 26 of the control unit 9 as the phase difference θ.
In addition, the control unit 9 may count the time when the phase difference signal voltage is not zero, instead of the averaged value of the phase difference signal.

  Next, the basic operation of the non-contact power feeding system 100 centering on the power transmission device 1 will be described with reference to FIG. This basic operation will be described assuming that the drive frequency of the inverter 7 is fixed.

The power supplied from the power source 3 is rectified and smoothed by the rectifier circuit 5 when the power source 3 is an alternating current such as a system power source. The rectifier circuit 5 includes, for example, a diode bridge, a smoothing reactor, and a smoothing capacitor. The rectifier circuit 5 may be configured without using a smoothing reactor.
The electric power smoothed by the rectifier circuit 5 is converted into high-frequency electric power by the inverter 7 connected to the subsequent stage of the rectifier circuit 5.

When charging an in-vehicle storage battery, a constant power supply is required depending on the situation.
For example, the input power detection unit 6, the inverter 7, and the control unit 9 are integrally provided with a feedback control function so that power can be transmitted at a constant 2kW, and the input power to the inverter 7 can be kept constant.
In order to perform this feedback control, the control unit 9 measures input power from the input current and input voltage of the inverter 7 detected by the input power detection unit 6.
The control unit 9 controls the output duty of the inverter 7 according to the input power so that the arithmetic processing unit 26 can always keep the input power of the inverter 7 constant.

  A power transmission side capacitor 10 and a power transmission coil 11 are connected in series to the output terminal of the phase difference detection unit 8 in FIG. 2, a high frequency current is supplied from the inverter 7 to the power transmission coil 11, and a high frequency magnetic field is generated around the power transmission coil 11. It is formed. The power transmission coil 11 can be formed by winding a conducting wire such as a litz wire in a spiral shape or a solenoid shape. Moreover, in order to improve the coupling coefficient with the receiving coil 12, the power transmission coil 11 may be inserted with a ferrite core, or may be a power transmission coil that does not use a ferrite core.

In the power receiving device 2, an induced current is generated in the power receiving coil 12 by the high frequency magnetic field generated by the power transmitting coil 11. The high-frequency power received from the power transmission device 1 is converted into DC power by the rectifier circuit 14 by a circuit composed of the power receiving coil 12 and the capacitor 13 connected in parallel.
Here, the power receiving coil 12 is also a coil formed of a conducting wire such as a litz wire, similar to the power transmitting coil 11, and a ferrite core may be inserted in order to improve the coupling coefficient with the power transmitting coil 11, or ferrite. The power receiving coil 12 may not use a core.
The rectifier circuit 14 includes a diode bridge, a smoothing reactor, and a smoothing capacitor. The rectifier circuit 14 may be configured without using a smoothing reactor.

A DC / DC converter 15 is connected to the rectifier circuit 14. When the non-contact power feeding system 100 performs the charging operation of the power storage device 4, the power smoothed by the rectifier circuit 14 is converted into an appropriate voltage by the DC / DC converter 15 and connected to the subsequent stage of the DC / DC converter 15. 4 is supplied with electric power.
As the power storage device 4, a nickel metal hydride battery or a lithium ion battery is used.

Next, the relationship between the inverter efficiency and the operating point in the non-contact power feeding system will be described.
In non-contact power supply, the output impedance of the inverter varies greatly depending on the positional relationship between the power transmission coil and the power reception coil. For this reason, in order to control electric power uniformly, the output duty of an inverter changes a lot.
In addition, since this description is description of general non-contact electric power feeding, (for example, an inverter) reference code is not attached | subjected with respect to a component apparatus.

  FIG. 6 is a diagram illustrating waveforms of the output voltage and output current of the inverter when the positional deviation is small and when the positional deviation is large. This is an example when the inverter is operated with a fixed driving frequency, and is not a waveform according to the present invention.

For example, when power is input from the inverter at a constant 2 kW, since the real part of the impedance viewed from the inverter, that is, the resistance component is large when the positional deviation is small, the output duty of the inverter is as shown in the right waveform of FIG. Becomes larger.
In addition, when the positional deviation is large, the real part of the impedance and the resistance component viewed from the inverter become small. Therefore, it is necessary to reduce the output duty of the inverter as shown by the waveform on the left side of FIG.
In Patent Documents 2 and 3, in a state where the positional deviation as shown in the right waveform of FIG. 6 is small, that is, duty = 1, the drive frequency of the inverter is controlled, the power factor is improved, and the efficiency of the inverter is improved. Has been explained.

However, the inventors of the present application have found that when the positional deviation is large, the efficiency of the inverter cannot be maximized even if the power factor is maximized. The reason will be described below.
When the positional deviation is large, the relationship between the output voltage and the output current of the inverter can be divided into three states according to the drive frequency of the inverter.
FIG. 7 is a diagram for explaining the three states.
When the zero cross point of the output current advances with respect to the rise of the output voltage of the inverter (FIG. 7A), when the rise of the output voltage of the inverter matches the zero cross point of the output current (FIG. 7 ( b)), there are three cases where the zero cross point of the output current is delayed with respect to the rise of the output voltage of the inverter (FIG. 7C).

Although the state of Fig.7 (a) is a state with the highest power factor, it becomes a mode which an inverter cannot perform zero volt switching.
Although the power factor is lower in the state of FIG. 7B than in the state of FIG. 7A, the efficiency is increased because the switching loss of the inverter is small. Further, in the state of FIG. 7A, since the switching is performed with a large current, the noise also increases.
In non-contact power feeding with high frequency and high power, such as for charging an in-vehicle storage battery, the effect of increased switching loss is greater than the reduction in reactive current due to power factor improvement. The state of FIG. 7C is a mode in which zero volt switching is possible, but the power factor is lower than that of FIG.
Since the inverter efficiency is maximized in the state shown in FIG. 7B, the phase difference θ between the rise of the output voltage of the inverter and the zero cross point of the output current becomes zero as shown in FIG. 7B. In addition, it is preferable to control the drive frequency and output duty.
Note that modes capable of performing zero-volt switching and modes incapable of performing zero-volt switching will be described later with reference to FIGS.

Next, functions and operations of the power transmission device of the present invention will be described.
Description will be made based on FIG. 8 showing a flowchart of the control method of the present invention, and FIGS. 9 to 15 showing waveforms of the output voltage and output current of the inverter 7 during control.
In the present invention, the drive frequency and output duty of the inverter 7 are controlled, and the input power of the inverter 7 is kept constant, while the efficiency of the inverter 7 is controlled to a good state.
The power storage device 4 will be described assuming an in-vehicle storage battery mounted on an automobile.

The vehicle is parked at the place where the power transmission device 1 is installed, and non-contact power feeding to the in-vehicle storage battery is started.
In step 1 (S01) of the control flowchart of FIG. 8, the control unit 9 fixes the drive frequency of the inverter 7, changes the output duty, and sets the input power of the inverter 7 to a power value required for non-contact power feeding. Control to match. The control in step 1 (S01) is appropriately described as “input power control by inverter output duty”.
The contactless power supply with the drive frequency of the inverter 7 fixed is the same as that described in the basic operation of the contactless power supply device.
The first control of the present invention is control performed by the control unit 9 in step 1 (S01). That is, the first control of the present invention is a control in which the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to the power value required for non-contact power feeding.

In step 2 (S02), the power input to the inverter 7 is determined. The input power is measured by the arithmetic processing unit 26 of the control unit 9 from the input current and the input voltage detected by the input power detection unit 6, and the input power is determined based on the measured value. This determination of the input power is a determination of whether or not the power value required for in-vehicle storage battery charging has been reached.
For example, under the condition that constant power input at 2 kW is required, it is determined whether 2 kW of power is input. Since this power value varies depending on the charging status and vehicle type, it is hereinafter referred to as a default value in the sense that the power value required by the charging status and vehicle type is default.

If it is determined in step 2 (S02) that the input power of the inverter 7 is different from the predetermined value, the process returns to step 1 (S01).
In step 1 (S01), as described above, control is performed so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.

If it is determined in step 2 (S02) that the inverter 7 has a predetermined input power, the process proceeds to step 3 (S03).
In step 3 (S03), the output duty of the inverter 7 is fixed by a command from the control unit 9.
FIG. 9 shows the output voltage waveform and output current waveform of the inverter 7 at this time.
At the start of power supply, the drive frequency is such that the efficiency of the inverter 7 is good, and the zero cross point of the output current is delayed with respect to the rise of the output voltage of the inverter 7, as shown in FIG. Is desirable.
Control may be started in a state where the zero cross point of the output current is advanced with respect to the output voltage of the inverter 7 as shown in FIG.

  Next, in step 4 (S04), the phase difference detection unit 8 detects the phase difference between the output voltage and the output current of the inverter 7, that is, the rise of the output voltage of the inverter 7 and the zero-cross point phase difference between the output currents.

Next, in step 5 (S05), the control unit 9 determines the phase difference θ based on the phase difference signal sent from the phase difference detection unit 8.
If it is determined in step 5 (S05) that the absolute value of the phase difference θ is greater than 0, the process proceeds to step 6 (S06).

In step 6 (S06), the control unit 9 determines whether the zero cross point of the output current is delayed with respect to the rise of the output voltage of the inverter 7.
If it is determined in step 6 (S06) that the output current phase is delayed, the process proceeds to step 7 (S07). If it is determined in step 6 (S06) that the phase is advanced, the process proceeds to step 8 (S08), which will be described later.

In step 7 (S07), the drive frequency of the inverter 7 is decreased by a command from the control unit 9.
When the drive frequency of the inverter 7 is decreased, the phase difference θ between the output voltage and the output current of the inverter 7 is reduced as shown in FIG. That is, in FIG. 11, the current waveform of the one-dot chain line shifts to the current waveform of the solid line.
In the following description, the current (voltage) waveform of the alternate long and short dash line is a waveform before transition (change), and the current (voltage) waveform of the solid line is a waveform after transition (change).
At this time, since the power factor of the inverter 7 is improved and the output duty is fixed, the input power of the inverter 7 is increased.

In order to correct the fluctuation of the input power of the inverter 7, the process returns from Step 7 (S07) to Step 1 (S01).
In step 1 (S01), the control unit 9 performs control so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.
In order to control the increased input power of the inverter 7 to a predetermined value, the output duty of the inverter 7 is reduced, so that the phase difference θ between the output voltage and the output current of the inverter 7 is further reduced as shown in FIG.

  The above steps are repeated, and when the phase difference between the output voltage and the output current of the inverter 7 becomes 0 as shown in FIG. 13 in the determination of step 5 (S05), the drive frequency of the inverter 7 is not changed and step 1 (S01) is performed. ) To return to the input power control based on the inverter output duty.

Next, the case where it is determined in step 6 (S06) that the phase has advanced will be described by returning to step 4 (S04), including the cause of this situation.
As shown in FIG. 14, the zero cross point of the output current may advance from the rise of the output voltage of the inverter 7 as the load fluctuates, such as an increase in the charging voltage of the in-vehicle storage battery.
In step 4 (S04) of the control flowchart of FIG. 8, since the zero cross point of the output current has advanced with respect to the rise of the output voltage of the inverter 7, a negative phase difference signal is sent from the phase difference detection unit 8 to the control unit 9. Will be sent.

In step 5 (S05), since the absolute value of the phase difference is larger than 0, the process proceeds to step 6 (S06).
In step 6 (S06), since the control unit 9 has received the negative phase difference signal, it is determined that the zero-cross point of the output current is advanced from the rise of the output voltage, and the process proceeds to step 8 (S08). In step 8 (S08), the drive frequency of the inverter 7 is increased.

When the drive frequency of the inverter 7 is increased, the phase difference between the output voltage and the output current of the inverter 7 is reduced as shown in FIG. At this time, the input power of the inverter 7 also varies. In order to correct this variation in input power, the process returns from step 8 (S08) to step 1 (S01).
In step 1 (S01), the control unit 9 performs control so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.

  The above steps are repeated, and when the phase difference between the output voltage and the output current of the inverter 7 becomes 0 in the determination of step 5 (S05), the drive frequency of the inverter 7 is not changed, and the inverter output duty of step 1 (S01) is changed. Return to input power control.

The second control of the present invention is a series of control of Step 3 (S03) to Step 7 (S07) and Step 3 (S03) to Step 8 (S08) performed by the control unit 9.
That is, the second control of the present invention is a control in which the output duty of the inverter 7 is fixed, the drive frequency is changed, and the phase difference between the output voltage and the output current of the inverter 7 is made zero. However, a positive phase difference signal and a negative phase difference signal are used as the phase difference signal between the output voltage and output current of the inverter 7.

  By using the control method of the present invention as described above, the phase difference between the output voltage and the output current of the inverter 7 is set to 0 while the input power of the inverter 7 is kept constant even when the load changes such as the change in the charging state. A combination of the drive frequency of the inverter 7 and the output duty can be searched.

Next, with reference to FIG. 7A to FIG. 7C, modes that can and cannot perform zero-volt switching will be described with reference to FIGS. 16 to 20.
16 to 20 show the output voltage waveform and output current waveform of the inverter 7 and the ON / OFF state of the FET of the inverter 7.

First, the operation mode of the inverter 7 when the zero crossing point of the output current of the inverter 7 in FIG. 7A is advanced with respect to the rise of the output voltage will be described.
In FIG. 16, only the low side of the left arm of the inverter 7 is on, and current flows through a path indicated by a thick dotted line as shown in the figure. At this time, a power supply voltage is applied between the drain and source on the high side of the right arm.
Next, the high-side FET of the right arm of the inverter 7 is turned on. FIG. 17 shows the state. At this time, the high side of the right arm of the inverter 7 is turned on in a state where the power supply voltage is applied, and a mode in which zero-volt switching cannot be performed is set. The same operation is performed for the left arm of FIG.
In FIG. 17, the state of FIG. 17 (left diagram) (the left low-side and right high-side FETs are on) continues during the thin dotted line period of FIG. 17 (right diagram).

Next, the case where the zero crossing point of the output current of the inverter 7 in FIGS. 7B and 7C is delayed with respect to the rise of the output voltage will be described.
FIG. 18 shows a state in which the right side and the left side of the inverter 7 are turned on. As shown in the figure, current flows along a path indicated by a thick dotted line.
Next, the low-side FET on the right side of the inverter is turned off. FIG. 19 shows the state at this time. As shown in the figure, current flows along a path indicated by a thick dotted line. At this time, since a current flows through the body diode of the high-side FET on the right side of the inverter, no voltage is applied to the high-side FET.
Next, the high-side FET of the right arm of the inverter 7 is turned on. FIG. 20 shows the state of the inverter 7. In this mode, zero volt switching is performed in order to turn on the FET while a current is flowing through the right-side high-side FET.

That is, whether or not the inverter 7 can perform zero volt switching depends on whether or not the direction of the current is reversed when the high side of the inverter 7 is turned on, that is, when the output voltage of the inverter 7 rises.
In the waveform of FIG. 7A, since the current is already inverted when the output voltage of the inverter 7 rises, the current does not flow through the body diode of the high-side FET, and the FET is turned on while the power supply voltage is applied. It will be.
On the other hand, in FIGS. 7B and 7C, when the output voltage of the inverter 7 rises, the current is not reversed because the current is not inverted, and the current flows through the high-side FET. It becomes.

  In Embodiment 1, the case where the system power supply which is AC power supply is used as the power supply 3 was demonstrated. A storage battery which is a direct current power source can also be used as the power source 3. In this case, the power supply 3 is directly connected to the input power detection unit 6 by bypassing the rectifier circuit 5.

  As described above, the power transmission device of the first embodiment includes the inverter, the control unit, the power transmission side capacitor, the power transmission coil, the input power detection unit, and the phase difference detection unit, and the control unit is the inverter. Based on the phase difference between the input power, the output voltage, and the current, the drive frequency and output duty of the inverter are changed so that the phase difference becomes zero while keeping the input power of the inverter constant. For this reason, the power transmission apparatus of Embodiment 1 can search and control the drive frequency of the inverter that improves the efficiency of the inverter while keeping the input power of the inverter constant. Moreover, there is an energy saving effect by improving the efficiency of the inverter.

Embodiment 2. FIG.
The power transmission device of the second embodiment is different from the power transmission device of the first embodiment in that the phase difference signal from the phase comparator of the phase difference detection unit to the arithmetic processing unit of the control unit is only the absolute value signal of the phase difference. Is.

  Hereinafter, regarding the configuration and operation of the power transmission device of the second embodiment, the difference from the first embodiment will be mainly described based on FIG. 21 which is a control flowchart and FIG. Explained. 1 is a system configuration diagram including the power transmission device described in the first embodiment, FIG. 2 is an internal configuration diagram of the power transmission device, and FIG. 9 to FIG. 9 are phase difference explanatory diagrams of the output voltage and output current of the inverter. Reference is made to 15 as appropriate.

The difference between the configuration of the power transmission device of the first embodiment and the configuration of the power transmission device of the second embodiment is that the phase difference signal output from the phase comparator 25 of the phase difference detection unit 8 to the arithmetic processing unit 26 of the control unit 9 Only.
In the power transmission device 1 of the first embodiment, a positive phase difference signal (advance) and a negative phase difference signal (lag) are separately transmitted from the phase comparator 25 of the phase difference detection unit 8 to the arithmetic processing unit 26 of the control unit 9. It was output on the line. In the power transmission device 1 according to the second embodiment, only the absolute value of the phase difference is output by one line from the phase comparator 25 of the phase difference detection unit 8 to the arithmetic processing unit 26 of the control unit 9.

Although the phase difference signal output from the phase comparator 25 has only an absolute value, it is possible to match the rise of the output voltage of the inverter 7 and the zero cross point of the output current while keeping the input power of the inverter 7 constant. . Since the phase difference signal output from the phase comparator 25 has only an absolute value, the control operation of the control unit 9 is different from that of the first embodiment.
The difference between the first embodiment and the embodiment is only the phase difference signal output from the phase comparator 25 of the phase difference detection unit 8 to the arithmetic processing unit 26 of the control unit 9. When referring to FIGS. 1 and 2 of the first embodiment, the reference numerals are used as they are.

The control of the control unit 9 in the second embodiment will be described based on the control flowchart of FIG. At the start of control, a control flag F, which will be described later, is set to an initial value F = 0.
In step 21 (S21) of the control flowchart of FIG. 21, the control unit 9 fixes the drive frequency of the inverter 7, changes the output duty, and sets the input power of the inverter 7 to the power value required for non-contact power feeding. Control to match. The control in step 21 (S021) is the same as the control in step 1 (S01) in the control flowchart of FIG. 8 of the first embodiment.

  Next, in step 22 (S22), power input to the inverter 7 is determined. The input power is measured by the arithmetic processing unit 26 of the control unit 9 from the input current and the input voltage detected by the input power detection unit 6, and the input power is determined based on the measured value. This determination of the input power is a determination of whether or not the power value required for in-vehicle storage battery charging has been reached.

If it is determined in step 22 (S22) that the input power of the inverter 7 is different from the predetermined value, the process returns to step 21 (S21).
In step 21 (S21), control is performed so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.

In step 22 (S22), the input power of the inverter 7 is determined. If the input power is a predetermined value, the output duty of the inverter 7 is fixed in accordance with a command from the control unit 9 in step 23 (S23).
FIG. 9 shows the output voltage waveform and output current waveform of the inverter 7 at this time.

  Next, in step 24 (S24), the phase difference detector 8 detects the phase difference θ between the output voltage and output current of the inverter 7, that is, the phase difference θ between the rise of the output voltage of the inverter 7 and the zero cross point of the output current. Do.

Next, in step 25 (S25), the control unit 9 determines the phase difference θ based on the phase difference signal sent from the phase difference detection unit 8.
If the absolute value of the phase difference θ is 0 in the determination in step 25 (S25), the process returns to step 21 (S21).
In step 21 (S21), the control unit 9 performs control so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.

In step 25 (S25), when the phase difference is larger than 0, the control unit 9 determines the control flag F in step 26 (S26).
The determination of the control flag F is to determine the positional relationship between the rise of the output voltage of the inverter 7 and the zero cross point of the output current.

  When the control flag F = 0, the zero cross point of the output current is delayed with respect to the rise of the output voltage of the inverter 7. When the control flag F = 1, the zero cross point of the output current is advanced with respect to the rise of the output voltage.

If it is determined in step 26 (S26) that the control flag is F = 0, the process proceeds to step 27 (S27). In step 27 (S27), the drive frequency of the inverter 7 is decreased.
If it is determined in step 26 that the control flag F = 1, the process proceeds to step 31 (S31), which will be described later.

  In step 27 (S27), when the drive frequency of the inverter 7 is decreased, the phase difference θ between the output voltage and the output current of the inverter 7 is reduced as shown in FIG.

  Next, the process proceeds to step 28 (S28). In step 28 (S28), the phase difference θ is acquired from the phase difference detection unit 8, and the control unit 9 detects the phase difference θ again.

Next, the process proceeds to step 29 (S29). In step 29 (S29), the control unit 9 determines the phase difference θ.
In this step 29 (S29), the phase relationship between the output voltage and the output current of the inverter 7 can be actually confirmed.
When the drive frequency of the inverter 7 is decreased in the state of FIG. 9, the phase difference θ measured in step 28 (S28) is decreased as compared with the phase difference detected before the drive frequency is decreased. This indicates that the phase of the output current is delayed with respect to the output voltage.

In this case, since it is determined in step 29 (S29) that the phase difference has decreased, the process returns to step 21 (S21) to perform input power control based on the inverter output duty.
If the rise of the output voltage of the inverter 7 is advanced with respect to the zero cross point of the output current, Step 21 (S21) to Step 29 (S29) are repeated until the output phase difference θ of the inverter 7 becomes zero.

On the other hand, the zero-cross point of the output current may advance from the rise of the output voltage of the inverter 7 due to load fluctuations such as an increase in the charging voltage of the in-vehicle storage battery. The control at this time will be described.
In step 25 (S25) of the control flowchart of FIG. 21, since the absolute value of the phase difference θ is larger than 0, the process proceeds to the determination of the control flag F in step 26 (S26).
Since the control flag F is still the initial value F = 0 at this time, the drive frequency of the inverter 7 is decreased in step 27 (S27).

Next, in step 28 (S28), the phase difference detector 8 detects the phase difference θ between the output voltage and the output current of the inverter 7.
When the phase of the output current is advanced with respect to the output voltage of the inverter 7, if the drive frequency of the inverter 7 is decreased, the output voltage and output current detected in step 28 (S28) are reduced as shown in FIG. The phase difference θ increases in comparison with the phase difference θ between the output voltage and the output current detected before the drive frequency of the inverter 7 is decreased.
Therefore, it can be determined that the phase difference θ between the output voltage and the output current of the inverter 7 is increased by determining the phase difference θ in step 29 (S29).

  Therefore, the process proceeds to step 30 (S30). In step 30 (S30), the control flag F is set to F = 1.

  Next, the process proceeds to step 31 (S31), and the drive frequency is increased in step 31 (S31).

Next, the process proceeds to step 32 (S32), and the phase difference θ between the output voltage and output current of the inverter 7 is detected in step 32 (S32).
Next, the process proceeds to step 33 (S33), and it is determined in step 33 (S33) whether or not the phase difference θ between the output voltage and the output current of the inverter 7 has decreased.
When the zero crossing point of the output current of the inverter 7 is advanced with respect to the output voltage, the phase difference θ decreases as shown in FIG. 15 when the drive frequency of the inverter 7 is increased. Return to (S21).

  In step 21 (S21), the control unit 9 performs control so that the drive frequency of the inverter 7 is fixed, the output duty is changed, and the input power of the inverter 7 is adjusted to a predetermined value.

  Next, Step 22 (S22) to Step 26 (S26) are performed in order, and F = 1 in the determination of the control flag in Step 26 (S26), and therefore, from Step 26 (S26) to Step 31 (S31). move on.

  When the zero crossing point of the output current of the inverter 7 is advanced with respect to the rise of the output voltage, the step 21 (S21) to the step 26 (S26), the step 31 (until the output phase difference θ of the inverter 7 becomes zero). S31) to step 33 (S33) are repeated.

  When the control flag is F = 1 and the phase of the output current of the inverter 7 is delayed from the output voltage, if the drive frequency of the inverter 7 is increased in step 31 (S31), the output of the inverter 7 is output. The phase difference θ between the voltage and the output current increases. Accordingly, in the detection of the phase difference θ in step 32 (S32) and the determination of the phase difference θ in step 33 (S33), it is not determined that the phase difference θ has decreased, so that the process proceeds from step 33 (S33) to step 34 (S34). move on.

In step 34 (S34), the control flag is set to F = 0.
Returning from step 34 (S34) to step 21 (S21), the steps 21 (S21) to 29 (S29) are repeated again, and the inverter 7 is controlled so that the phase difference θ remains zero while the input power of the inverter 7 remains constant. Search for a combination of drive frequency and output duty.

The second control of the present invention is performed by the control unit 9 at Step 23 (S23) to Step 29 (S29), Step 23 (S23) to Step 33 (S33), and Step 23 (S23) to Step 26 ( S26) Further, a series of control of step 31 (S31) to step 33 (S33) or step 31 (S31) to step 34 (S34).
That is, the second control of the present invention is a control in which the output duty of the inverter 7 is fixed, the drive frequency is changed, and the phase difference between the output voltage and the output current of the inverter 7 is made zero. However, only the absolute value of the phase difference is used as the phase difference signal between the output voltage and output current of the inverter 7.

In the power transmission device of the second embodiment, after detecting the phase difference θ between the output voltage and the output current of the inverter 7, the drive frequency of the inverter 7 is changed, and then the phase difference between the output voltage and the output current of the inverter 7 again. θ is detected and determined.
By controlling in this way, the phase relationship between the output voltage and the output current of the inverter 7 can be grasped and controlled only by the absolute value of the phase difference θ. Since the signals input from the phase difference detection unit 8 to the control unit 9 are reduced, the configuration of the phase comparator 25 of the phase difference detection unit 8 and the arithmetic processing unit 26 of the control unit 9 can be simplified.

  As described above, the power transmission device according to the second embodiment is different from the power transmission device according to the first embodiment in that the phase difference signal from the phase comparator of the phase difference detection unit to the arithmetic processing unit of the control unit is the phase difference signal. Only absolute value signals are used. Similar to the power transmission device of the first embodiment, the power transmission device of the second embodiment can search and control the drive frequency of the inverter that improves the efficiency of the inverter while keeping the input power of the inverter constant, and has an energy saving effect. . Furthermore, the configuration of the phase difference detection unit and the control unit can be simplified.

  Note that the present invention can be freely combined with each other within the scope of the invention, and the embodiments can be modified or omitted as appropriate.

1 power transmission device, 2 power receiving device, 3 power source, 4 power storage device, 5 power transmission side rectifier circuit,
6 Input power detection unit, 7 Inverter, 8 Phase difference detection unit, 9 Control unit,
10 power transmission side capacitor, 11 power transmission coil, 12 power reception coil,
13 power receiving side capacitor, 14 power receiving side rectifier circuit, 15 DC / DC converter,
21 input current detector, 22 input voltage detector, 23 output current detector,
24 output voltage detection unit, 25 phase comparator, 26 arithmetic processing unit, 27 gate driver, 100 contactless power supply system.

Claims (4)

An inverter that outputs high-frequency power;
A control unit for controlling the inverter;
A power transmission side capacitor connected to the output of the inverter and supplied with the high frequency power;
A power transmission coil connected to the power transmission side capacitor;
An input power detection unit for detecting input power of the inverter;
A phase difference detection unit for detecting a phase difference between the output voltage and the output current of the inverter;
Based on the input power of the inverter and the phase difference detected by the phase difference detection unit, the control unit maintains the input power of the inverter constant and sets the phase difference to 0. A power transmission device that changes a drive frequency and an output duty of the inverter. When the control unit starts controlling the inverter,
When the drive frequency of the inverter is fixed and the input power detected by the input power detection unit of the inverter is not a value required for power transmission, the output duty of the inverter is changed to request the input power for power transmission. The first control to match the value
Furthermore, the output duty of the inverter is fixed, and the second control is performed to change the drive frequency of the inverter so that the phase difference is zero.
The power transmission device according to claim 1, wherein the first control and the second control are repeated until the phase difference becomes zero. When the control unit performs the second control,
When the phase difference is a positive value, the drive frequency of the inverter is decreased and the second control is terminated.
The power transmission device according to claim 2, wherein when the phase difference is a negative value, the drive frequency of the inverter is increased and the second control is terminated. When the control unit performs the second control,
When the absolute value of the phase difference is not 0, the control flag F is set to 0 at the start of control,
If the control flag is F = 0, the drive frequency of the inverter is decreased,
Detecting the phase difference between the output voltage and output current of the inverter;
When the phase difference decreases, the second control is terminated,
When the phase difference increases, the control flag is set to F = 1, the drive frequency of the inverter is increased,
Detecting the phase difference between the output voltage and output current of the inverter;
When the phase difference decreases, the second control is terminated,
The power transmission device according to claim 2, wherein when the phase difference increases, the control flag is set to F = 0 and the second control is terminated.

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