JP6710106B2 - Power supply system and power supply method - Google Patents

Description

In the present invention, when the primary side coil connected to the primary side power source and the secondary side coil connected to the secondary side load are arranged with a gap, The present invention relates to a power supply system and a power supply method for supplying power to a secondary coil in a contactless manner.

In recent years, a primary side coil connected to a primary side power source and a secondary side coil connected to a secondary side load are arranged with a gap, and the primary side coil is not connected to the secondary side coil. A technique has been developed in which non-contact power supply (non-contact power transmission) is performed from a power source to a load by supplying electric power by contact.

As one of such contactless power feeding methods, there is a method using electromagnetic induction. In this power supply system, for example, the power source on the primary side (power supply side) is an AC power source, the load on the secondary side (power reception side) is a power storage device equipped in the electric vehicle, and the power supply side is connected to the ground side outside the electric vehicle. The power storage device such as a secondary battery or a capacitor is charged using electromagnetic induction between the provided primary side coil and the secondary side coil provided on the electric power receiving side vehicle.

For example, Patent Documents 1 and 2 are disclosed as conventional techniques of the non-contact power feeding system.

In Patent Document 1, in order to transmit power feeding information such as a charging instruction and required power from the power receiving side to the power feeding side during non-contact power feeding, a communication device is provided in the primary coil and the secondary coil, and between both coils. It is disclosed that the power feeding information is transmitted and received to perform non-contact power feeding from the power feeding side to the power receiving side based on the power feeding information.

On the other hand, in Patent Document 2, in the non-contact power feeding method, there is a large allowance for the positional deviation between the primary coil and the secondary coil during the non-contact power feeding and the variation in the gap length between the two coils. There is a problem that the ratio of the primary voltage and the secondary voltage changes with the change of the positional relationship. Further, in Patent Document 2, in order to solve this problem, if power supply information is exchanged by communication between a primary side coil (power supply side coil) and a secondary side coil (power reception side coil), communication of It is disclosed that interference, communication error, communication noise due to a power transmission magnetic field, and the like occur, and installation of a communication device hinders reduction in size and weight on the power receiving side. In order to solve such a problem, the technique of Patent Document 2 realizes a constant secondary voltage by controlling the primary voltage without using a communication device.

JP, 2008-288889, A JP, 2011-45195, A

In the technology of Patent Document 2, from the viewpoint that a constant voltage is desirable for the charging voltage to the power storage device, the secondary voltage is converted to a constant voltage by controlling the primary voltage without using a communication device, and the secondary battery is used. To charge. However, when power is supplied to a load that is a power storage device such as a secondary battery, a simpler control method, specifically, to the load on the secondary side without controlling the primary voltage, It is preferable that contactless power supply can be performed.

The present invention has been made in consideration of such a problem, and does not exchange power supply information between a primary side that is a power supply side and a secondary side that is a power reception side, and To provide a power supply system and a power supply method capable of supplying power to a load on a secondary side by using contactlessly supplied power from a primary side to a secondary side without controlling a secondary voltage. To aim.

In the present invention, a primary side coil connected to a primary side power source and a secondary side coil connected to a secondary side load are arranged with a gap, and the primary side coil is connected to the secondary side coil. The present invention relates to a power supply system and a power supply method for supplying power to a side coil in a contactless manner.

In order to achieve the above object, the power supply system according to the present invention is provided between the secondary coil and the load, and controls the power supply from the secondary coil to the load. Means are provided. In this case, the control means performs a voltage conversion on the rectified output voltage and the output current of the secondary coil and the rectified output voltage, and converts the output voltage into a DC voltage. To the load, and a control unit that controls the voltage conversion circuit, wherein the control unit controls the maximum output current flowing from the secondary coil to the load in the secondary coil. In the current region equal to or lower than the current value corresponding to the power operating point, the load resistance starts from an initial state in which the load resistance value when the load is viewed from the secondary coil becomes substantially infinite, and the load resistance changes with time. The power supply from the secondary coil to the load is controlled so that the value decreases , and the control unit controls the target current value of the DC current flowing from the voltage conversion circuit to the load and the target of the DC voltage. A voltage value and a maximum power value of output power obtained by multiplying the output voltage after rectification and the output current are set, and the DC voltage reaches the target voltage value or the output power reaches the maximum power value. When the DC current reaches the target current value before the DC current, the voltage conversion circuit is controlled so that the DC current becomes constant at the target current value, and the DC current becomes the target current value. When the DC voltage reaches the target voltage value before the output power reaches the maximum power value or the output power reaches the maximum power value, the voltage conversion is performed so that the DC voltage becomes constant at the target voltage value. If the output power reaches the maximum power value before the DC current reaches the target current value or the DC voltage reaches the target voltage value by controlling a circuit, the output power Controls the voltage conversion circuit so that is constant at the maximum power value .

In order to achieve the above-mentioned object, in the power supply method according to the present invention, the power supply from the secondary coil to the load is performed by the control means provided between the secondary coil and the load. controls, the control means includes a rectifier circuit for rectifying the output voltage and output current of the secondary coil, performs voltage conversion with respect to the output voltage after rectification, which is the output voltage of the converted DC A voltage conversion circuit that supplies a voltage to the load and a control unit that controls the voltage conversion circuit are provided, and the control unit controls the output current flowing from the secondary coil to the load of the secondary coil. In a current region equal to or lower than the current value corresponding to the maximum power operating point, the load resistance value when the load is viewed from the secondary coil starts from an initial state where the load resistance value is substantially infinite, and the load changes with time. The power supply from the secondary coil to the load is controlled so that the resistance value decreases , and the control unit controls the target current value of the DC current flowing from the voltage conversion circuit to the load and the DC voltage. A target voltage value and a maximum power value of output power obtained by multiplying the output voltage after rectification and the output current are set, and the DC voltage reaches the target voltage value or the output power reaches the maximum power value. If the DC current reaches the target current value before, the DC converter controls the voltage conversion circuit so that the DC current becomes constant at the target current value, and the DC current is the target current value. When the DC voltage reaches the target voltage value before the output power reaches the maximum power value or the output power reaches the maximum power value, the voltage so that the DC voltage becomes constant at the target voltage value. If the output current reaches the maximum power value before the DC current reaches the target current value or the DC voltage reaches the target voltage value, the output is controlled by controlling the conversion circuit. The voltage conversion circuit is controlled so that the electric power is constant at the maximum electric power value .

Thus, in the present invention, the control means controls the power supply from the secondary coil to the load by decreasing the load resistance value from substantially infinity with the lapse of time. Therefore, according to the present invention, the power supply to the load can be controlled without exchanging the power supply information between the primary side and the secondary side and without controlling the primary voltage. .. That is, the control on the power supply to the load is completed on the secondary side regardless of the state of the primary side. As a result, the electric power supplied from the primary coil to the secondary coil in a non-contact manner can be used to supply electric power to the load by simple control on the secondary side.

Therefore, the present invention does not require a feedback means (communication device or the like) from the secondary side to the primary side. Further, the compatibility between the primary side and the secondary side due to the provision of the communication device and the interoperability test for ensuring the compatibility become unnecessary. In this way, many processes for ensuring compatibility are unnecessary. Therefore, in the present invention, the cost of the power supply system can be reduced.

Further, the voltage conversion circuit is configured to include a switching element, and the control unit sets the load resistance value to substantially infinity by turning off the switching element in the initial state, and thereafter, every predetermined unit time. It is preferable to gradually decrease the load resistance value by increasing the on-time of the switching element. This makes it possible to easily supply electric power to the load.

Specifically, the control unit may control the power supply to the load as follows.

That is, when the DC current reaches the target current value, the control unit controls the DC current to the target current value while increasing or decreasing the duty of the switching element. After that, when the output power reaches the maximum power value, the control unit controls the output power to the maximum power value while increasing or decreasing the duty. Further, the control unit, when the DC voltage reaches the target voltage value, and when the DC voltage continuously reaches the target voltage value within a specified time, turns off the switching element, The control of the voltage conversion circuit is ended.

Thus, when the load is a power storage device such as a secondary battery and the SOC (charge rate) is low, non-contact power supply to the power storage device can be easily performed to complete the charging.

When the DC voltage reaches the target voltage value, the control unit controls the DC voltage to the target voltage value while increasing or decreasing the duty of the switching element, and then the DC voltage is within a specified time. When the target voltage value is continuously reached, the switching element may be turned off to end the control of the voltage conversion circuit. Accordingly, when the load is the power storage device, contactless power supply to the power storage device can be completed in a short time if the SOC is sufficiently large.

Furthermore, when the output power reaches the maximum power value, the control unit controls the output power to the maximum power value while increasing or decreasing the duty of the switching element, and then the DC voltage is the target voltage. When the value reaches the target voltage value and the DC voltage reaches the target voltage value continuously within a specified time, the switching element may be turned off and the control on the voltage conversion circuit may be ended. Thus, when the load is a power storage device, even if the maximum power value is set to a small value due to a positional deviation between the primary coil and the secondary coil, the power storage device can be easily set. Can be contactlessly fed to. As a result, the maximum electric power that can be obtained from the primary side can be easily and efficiently supplied to the power storage device.

In each of the above inventions, the switching element is preferably a field effect transistor. Accordingly, it is possible to quickly perform voltage conversion from the output voltage in the voltage conversion circuit to the DC voltage while suppressing power consumption in the voltage conversion circuit.

Further, the output power increases with a decrease in the output voltage after rectification, reaches the maximum power value at the maximum power operating point where the product of the output current and the output voltage is maximum, and further, It has a drooping characteristic that decreases when the output voltage is reduced. On the other hand, the output current after rectification has a characteristic of becoming smaller as the output voltage increases. In this case, in the initial state, the load resistance value becomes substantially infinite, so that the output voltage becomes the no-load voltage as the maximum voltage value and the output current becomes the minimum value. Therefore, in the current region, the control unit may start from the no-load voltage and control the voltage conversion circuit between the no-load voltage and the output voltage value according to the maximum power operating point. ..

In the current region, the loss (copper loss) of the internal resistance on the secondary side is small, and the power use efficiency is high. Therefore, by controlling the voltage conversion circuit between the no-load voltage and the output voltage value corresponding to the maximum power operating point, the loss due to the power supply on the secondary side is reduced, and It becomes possible to perform non-contact power feeding to the load. In addition, even if the electric power that can be supplied to the load is restricted due to a positional deviation between the primary coil and the secondary coil or an increase in the gap length, It is possible to supply the maximum electric power to the load under the given constraint condition.

Furthermore, it is preferable that the primary coil and the secondary coil are electromagnetic induction coils. This makes it possible to easily control the power supply to the load.

According to the present invention, the control means controls the power supply from the secondary coil to the load by decreasing the load resistance value from substantially infinity with the lapse of time. Therefore, in the present invention, the power supply to the load can be controlled without exchanging the power supply information between the primary side and the secondary side and without controlling the primary voltage. That is, the control on the power supply to the load is completed on the secondary side regardless of the state on the primary side. As a result, the electric power supplied to the secondary coil in a non-contact manner from the primary coil can be used to supply electric power to the load by simple control on the secondary side.

It is a circuit diagram of a power supply system according to the present embodiment. It is a circuit diagram which shows the equivalent circuit of the primary side coil and secondary side coil of FIG. It is a graph which shows the relationship of the input voltage, the input current, and the input electric power with respect to a voltage conversion circuit. 6 is a graph showing a relationship among an input current, an input voltage, a required voltage, an input power and a duty. It is a flowchart explaining operation|movement of the electric power supply system of FIG. 3 is a timing chart of the first embodiment. 7 is a timing chart of the second embodiment. 9 is a timing chart of the third embodiment. It is a circuit diagram which shows the modification of the electric power supply system of FIG.

Hereinafter, preferred embodiments of a power supply system and a power supply method according to the present invention will be illustrated and described with reference to the accompanying drawings.

[Configuration of this embodiment]
As shown in FIG. 1, the power supply system 10 according to the present embodiment is a system that performs non-contact power feeding (non-contact power transmission) from a primary side 12 that is a power feeding side to a secondary side 14 that is a power receiving side. ..

Specifically, on the primary side 12, a series circuit of a resistor 18 and a primary side coil 20 is connected to an AC power supply 16. On the other hand, on the secondary side 14, a control means 24 and a secondary battery 26 as a load are connected in parallel to the secondary coil 22.

In the control unit 24, the rectifier circuit 28, the first smoothing circuit 30, the voltage conversion circuit 32, and the second smoothing circuit 34 are parallel to the secondary coil 22 from the secondary coil 22 toward the secondary battery 26. It is connected to the.

The rectifier circuit 28 is a diode bridge composed of four diodes 36. The first smoothing circuit 30 has a capacitor 38. The voltage conversion circuit 32 has a MOSFET (metal oxide semiconductor field effect transistor) 40 as a switching element, a diode 42, and a coil 44.

In this case, a series circuit of the MOSFET 40 and the diode 42 is connected in parallel with the capacitor 38. That is, the drain terminal of the MOSFET 40 is connected to one end of the capacitor 38, the source terminal is connected to the cathode of the diode 42, and the anode of the diode 42 is connected to the other end of the capacitor 38. Further, one end of a coil 44 is connected to the source terminal of the MOSFET 40 and the cathode of the diode 42, and the other end of the coil 44 is connected to one end of a capacitor 46 that constitutes the second smoothing circuit 34.

One end of the capacitor 46 is connected to the positive electrode of the secondary battery 26, and the other end of the capacitor 46 is connected to the negative electrode of the secondary battery 26. In this case, the other end of the capacitor 46, the anode of the diode 42 and the other end of the capacitor 38 are connected to the negative electrode of the secondary battery 26.

In the control means 24, a current sensor 48 is connected between one end of the capacitor 38 and the drain terminal of the MOSFET 40. A voltage sensor 50 is connected in parallel with the capacitor 38. Further, a current sensor 52 is connected between one end of the capacitor 46 and the positive electrode of the secondary battery 26. Further, a voltage sensor 54 is connected in parallel with the capacitor 46 and the secondary battery 26. Further, the control unit 24 further includes a charge control unit 56 and a step-down control unit 58 as a control unit of the MOSFET 40.

The power supply system 10 is applied to, for example, contactless power supply to a power storage device (secondary battery 26) included in an electric vehicle (not shown). In this case, the primary coil 20 is a power supply side (ground side) coil, and the secondary coil 22 is an electric vehicle side coil. That is, when the electric vehicle moves above the primary coil 20 on the ground side, the primary coil 20 and the secondary coil 22 are arranged with a predetermined gap. Electric power is supplied from the primary coil 20 to the secondary coil 22 in a non-contact manner by electromagnetic induction between the primary coil 20 and the secondary coil 22, and the AC power supply 16 performs non-contact power feeding (non-contact). The secondary battery 26 can be charged by contact power transmission.

Due to the above electromagnetic induction, a mutual inductance M is generated between the primary coil 20 having the self-inductance L1 and the secondary coil 22 having the self-inductance L2. FIG. 2 shows an equivalent circuit between the primary coil 20 and the secondary coil 22 in this case.

Here, when the primary current I1 flows from the AC power supply 16 to the primary coil 20 via the resistor 18, when the primary voltage V1 is applied to the primary coil 20, the secondary coil 22 Due to the electromagnetic induction, the secondary voltage V2 of the AC voltage as the electromotive force is generated, and the secondary current I2 as the AC current flows. The following relationships (1) to (3) are established between the primary voltage V1 and the primary current I1 and the secondary voltage V2 and the secondary current I2.
V1=jω×L1×I1-jω×M×I2 (1)
V2=jω×M×I1-jω×L2×I2 (2)
M=k×(L1×L2) ^1/2 (3)

In addition, j is an imaginary unit and ω is an angular frequency. Also, k is a coupling coefficient (k<1).

From the above equations (1) to (3), the secondary voltage V2 can be expressed by the following equation (4). The power P2 of the secondary coil 22 can be expressed by the following equation (5).
V2=jω×I2×{(M ² −L1×L2)/L1}
+V1 x (M/L1) (4)
P2=V2×I2 (5)

The rectifier circuit 28 rectifies the secondary voltage V2 and the secondary current I2 and converts them into a pulsating voltage and a pulsating current, respectively. The first smoothing circuit 30 generates a DC voltage (output voltage) Vin and a DC current (output current) Iin that are electromotive force by smoothing the pulsating voltage and the pulsating current.

The DC voltage Vin is a DC voltage corresponding to the secondary voltage V2 that is the output voltage of the secondary coil 22, and is an input voltage applied to the input side of the voltage conversion circuit 32. Further, the direct current Iin is a direct current corresponding to the secondary current I2 which is the output current of the secondary coil 22, and is an input current flowing to the input side of the voltage conversion circuit 32. Therefore, in the following description, the DC voltage (output voltage) Vin may be referred to as the input voltage Vin, and the DC current (output current) Iin may be referred to as the input current Iin.

In FIG. 1, the voltage conversion circuit 32 is a step-down chopper and turns on or off the MOSFET 40 to step down the input voltage Vin. Since the step-down chopper having the configuration shown in FIG. 1 is well known, its detailed description is omitted.

The input voltage Vin is stepped down, smoothed by the second smoothing circuit 34, and supplied to the secondary battery 26 as an output voltage (DC voltage) Vout. Further, the output current (DC current) Iout corresponding to the input current Iin also flows from the second smoothing circuit 34 to the secondary battery 26. As a result, the secondary battery 26 is charged.

The current sensor 48 detects the input current Iin and outputs a detection signal corresponding to the detected input current Iin to the charging control unit 56. The voltage sensor 50 detects the input voltage Vin and outputs a detection signal corresponding to the detected input voltage Vin to the charging control unit 56. The current sensor 52 detects the output current Iout and outputs a detection signal corresponding to the detected output current Iout to the charging control unit 56. The voltage sensor 54 detects the output voltage Vout and outputs a detection signal corresponding to the detected output voltage Vout to the charging control unit 56.

The charging control unit 56, based on the input detection signals (input voltage Vin, input current Iin, output voltage Vout, output current Iout), the voltage value (request voltage) and current required for charging the secondary battery 26. A value (request current) is calculated and a command signal corresponding to the calculated request voltage and request current is output to the step-down control unit 58.

The step-down control unit 58 controls the turning on or off of the MOSFET 40 by supplying a control signal to the gate terminal of the MOSFET 40 based on the command signal from the charging control unit 56. The step-down control unit 58 controls ON/OFF of the MOSFET 40 by PWM (Pulse Width Modulation) control. Details of the PWM control will be described later.

FIG. 3 shows the qualitative relationship between the input voltage Vin, the input current Iin, and the DC power (output power) Pin (Pin=Vin×Iin) obtained by multiplying the input voltage Vin and the input current Iin. Since the DC power Pin is the input power to the voltage conversion circuit 32, it may be referred to as the input power Pin in the following description.

In FIG. 3, V0 is a no-load voltage. The no-load voltage V0 is a value of the input voltage Vin (electromotive force) when the load resistance value is substantially infinite when the secondary battery 26 that is a load is viewed from the secondary coil 22. If the MOSFET 40 is turned off and the conduction between the drain terminal and the source terminal is cut off, the load resistance value becomes substantially infinite.

Here, when the primary coil 20 and the secondary coil 22 are coupled by electromagnetic induction and the input power Pin is consumed by a load such as the secondary battery 26, the input voltage Vin is lowered from the no-load voltage V0. Then, the input power Pin increases. When the input voltage Vin is further reduced, the value of the input power Pin becomes the maximum power Pmax (maximum power value). That is, in the characteristic of the input power Pin, the operating point at the maximum power Pmax is the maximum power operating point of the secondary coil 22.

Thereafter, when the input voltage Vin is further reduced from the input voltage value Vinmax (the output voltage value corresponding to the maximum power operating point) according to the maximum power Pmax, the input power Pin is reduced. That is, the input power Pin has a drooping characteristic that changes parabolically with respect to the input voltage Vin.

It should be noted that reducing the input voltage Vin from the no-load voltage V0 can be rephrased as increasing the load from 0, and can also be rephrased as reducing the load resistance value from infinity.

In such a drooping characteristic of the input power Pin, there are a total of two input voltage Vin values corresponding to an arbitrary input power Pin, one on each of the left and right sides of FIG. 3 across the maximum power Pmax. On the other hand, the input current Iin has a characteristic of becoming smaller as the input voltage Vin increases. Therefore, the smaller the input current Iin, the smaller the loss (copper loss) due to the internal resistance of the circuit on the secondary side 14, and the higher the utilization efficiency of the input power Pin.

Therefore, in the power supply system 10, the secondary battery 26 is charged in the current region equal to or lower than the input current value Iinmax according to the maximum power Pmax, that is, in the voltage region between the no-load voltage V0 and the input voltage value Vinmax. Be seen. That is, in this voltage region (current region), the input current Iin is small and the input voltage Vin is high, so the load is small and the load resistance value is high. Therefore, in this charge control, the operating point of the secondary coil 22 changes between the no-load voltage V0 and the maximum power Pmax (input voltage value Vinmax) due to the drooping characteristic of the input power Pin.

FIG. 4 is a graph showing the relationship between the input current Iin, the input voltage Vin and the input power Pin, the required voltage and the duty of the MOSFET 40.

As described above, in the power supply system 10, the charging control for the secondary battery 26 is performed in the voltage region between the no-load voltage V0 and the input voltage value Vinmax (current region of the input current value Iinmax or less). Therefore, the required voltage is set between the end-of-charge voltage Vobj and the end-of-discharge voltage according to the voltage range and the current range. In FIG. 4, the required voltage is set within the range shown by the triangles in the voltage region and the current region.

The duty is also set to 0% at the no-load voltage V0 and X% at the input voltage value Vinmax. Therefore, in the above voltage region and current region, the duty of the control signal supplied from the step-down control unit 58 to the MOSFET 40 can be changed within the range of 0% to X%. The duty of X% is a duty corresponding to the maximum value Tonmax of the on time Ton of the MOSFET 40.

In this case, the input voltage Vin can be changed from the no-load voltage V0 to the input voltage value Vinmax by gradually increasing the duty from 0% corresponding to the no-load voltage V0 in the initial state toward X%. it can. In other words, by increasing the duty, it is possible to reduce the load resistance value (equivalent impedance) when the secondary battery 26 is viewed from the secondary coil 22. By such charge control, the SOC (charge rate) of the secondary battery 26 can be charged within the range of 0% to 100%.

[Operation of this embodiment]
Next, the operation (power supply method) of the power supply system 10 according to the present embodiment will be described with reference to FIGS. 5 to 8. In this operation description, it will be described with reference to FIGS. 1 to 4 as necessary.

As described above, in the power supply system 10 of FIG. 1, the voltage conversion circuit 32 is a step-down chopper. In this case, the charging end voltage Vobj, which is the maximum value of the charging voltage of the secondary battery 26, is set to a voltage value equal to or lower than the no-load voltage V0. Therefore, in the charge control for the secondary battery 26, the target is to raise the output voltage Vout to the end-of-charge voltage Vobj. On the other hand, the target current Iobj of the output current Iout changes depending on the charging condition of the secondary battery 26. In this case, the target current Iobj is preferably the maximum current value with which the secondary battery 26 can be charged, for example.

Then, the step-down control unit 58 turns on or off the MOSFET 40 by PWM control based on the command signal from the charge control unit 56. In this case, the period of the control signal is τ.

FIG. 5 is a flowchart showing the operation of the power supply system 10. In the power supply method according to this flowchart, the following three embodiments (first to third embodiments) can be applied.

The first embodiment (see FIG. 6) shows a case where the output current Iout reaches the target current Iobj first among the output current Iout, the output voltage Vout, and the input power Pin used for charging the secondary battery 26. .. The first embodiment assumes a case where the secondary battery 26 whose SOC has decreased is fully charged (SOC: 100%).

The second embodiment (see FIG. 7) shows a case where the output voltage Vout reaches the end-of-charge voltage Vobj among the output current Iout, the output voltage Vout, and the input power Pin first. The second embodiment assumes a case where the secondary battery 26, which is close to full charge, is charged.

The third embodiment (see FIG. 8) shows a case where the input electric power Pin reaches the maximum electric power Pmax first among the output current Iout, the output voltage Vout, and the input electric power Pin. In the third embodiment, it is assumed that the maximum electric power Pmax is set low due to the positional deviation between the primary coil 20 and the secondary coil 22 and the large gap length.

The first to third examples are examples of the present embodiment, and in practice, which of the output current Iout and the output voltage Vout reaches the target value first, or the input power Pin is the first. Whether the maximum power Pmax is reached depends on the state of the secondary battery 26 during charge control, the coupling state between the primary coil 20 and the secondary coil 22 (the magnitude of the coupling coefficient k), and the like. Note that

[First embodiment]
The first embodiment will be described with reference to FIGS. 5 and 6.

First, in order to charge the secondary battery 26, the power supply side (primary side 12) and the power receiving side (secondary side 14) are set to predetermined positions, and the primary side coil 20 and the secondary side coil 22 are connected. It is arranged with a predetermined gap length.

Next, at time t0 in FIG. 6, a switch (not shown) on the primary side 12 is turned on, so that AC power is supplied from the AC power supply 16 to the primary coil 20 via the resistor 18. Thereby, the secondary voltage V2 is generated in the secondary coil 22 by electromagnetic induction between the primary coil 20 and the secondary coil 22, and AC power is generated. As a result, power can be supplied (charged) to the secondary battery 26 by internal control on the secondary side 14.

In this case, in step S1 of FIG. 5 before time t0, the charging control unit 56 first supplies the command signal for setting the on-time Ton to 0 to the step-down control unit 58. The step-down control unit 58 keeps the MOSFET 40 off based on the command signal. As a result, the connection between the input side and the output side of the voltage conversion circuit 32 is cut off, and the load resistance value when the secondary battery 26 is viewed from the secondary coil 22 becomes infinite. That is, the connection with the secondary battery 26 is opened, and a no-load state is set. The no-load state set by the process of step S1 is the initial state of the power supply system 10.

In the next step S2, the charging control unit 56 acquires the output voltage Vout from the voltage sensor 54 and the output current Iout from the current sensor 52. In step S3, the charging control unit 56 acquires the input voltage Vin from the voltage sensor 50 and the input current Iin from the current sensor 48. Then, in step S4, the charging control unit 56 calculates the input power Pin by multiplying the input voltage Vin and the input current Iin.

In the next step S5, the charging control unit 56 determines whether or not the current input power Pin calculated in step S4 is greater than the value of the previous input power Pin (hereinafter, also referred to as the previous value Pinold). ..

When the input power Pin this time is larger than the previous value Pinold (step S5: YES, Pin>Pinold), in the next step S6, the charge control unit 56 controls to increase the duty of the MOSFET 40 in the previous charge control process. (Hereinafter, referred to as duty-up control) is determined. That is, in step S6, the charging control unit 56 determines whether or not the processing in step S9 described below, which increments the on-time Ton by the unit time Δτ, has been executed in the previous charging control processing.

The unit time Δτ is the minimum unit time when the on-time Ton is changed. For example, when the on-time Ton can be changed in n stages including 0, Δτ=τ/(n− 1).

If the determination result of step S6 is affirmative (step S6: YES), the charge control unit 56 determines whether or not the output voltage Vout is lower than the charge end voltage Vobj as the target voltage in the next step S7. ..

Since Vout<Vobj at the time point t0 (step S7: YES), the charge control unit 56 determines whether or not the output current Iout is smaller than the target current Iobj at the next step S8.

At the time point t0, since Iout<Iobj (step S8: YES), the charging control unit 56 increments the on time Ton by the unit time Δτ in the next step S9. In this case, since the control means 24 has a feedback control configuration, incrementing the on-time Ton by the unit time Δτ means controlling the load resistance value to decrease from infinity in the initial state. To do. That is, the flowchart of FIG. 5 has the processing content of performing charging control on the secondary battery 26 so that the load resistance value decreases with the passage of time.

In the next step S10, the charging control unit 56 sets the current input power (current value) Pin to the previous value Pinold. Then, in step S11, the charging control unit 56 determines whether or not the charging control for the secondary battery 26 should be ended.

When continuing the charge control (step S11: NO), the charge control unit 56 outputs a command signal according to the ON time Ton incremented in step S9 to the step-down control unit 58. The step-down control unit 58 supplies a control signal with a duty corresponding to the on time Ton to the gate terminal of the MOSFET 40 based on the command signal from the charging control unit 56 to turn the MOSFET 40 on or off. Then, the process returns to step S2. That is, the processes of steps S2 to S10 are repeatedly executed until it is determined in step S11 that the charging control is finished (step S11: YES).

In this way, by repeatedly performing the processing of steps S2 to S10, as shown in FIG. 6, the output current Iout, the output voltage Vout, the input power Pin, and the duty (on time Ton) have elapsed from time t0. It increases with each.

Then, at time t1 when time T1 has elapsed from time t0, the output current Iout first reaches the target current Iobj. The target current Iobj is, for example, preferably the maximum current value with which the secondary battery 26 can be charged, as described above.

As a result, a negative determination result is obtained in step S8 (step S8: NO, Iout≧Iobj), so in the next step S12, the charging control unit 56 decrements the on-time Ton by the unit time Δτ. In the next step S13, the charging control unit 56 determines whether or not the on-time Ton after decrement has a negative value.

Usually, Ton>0 (step S13: NO), so the charging control unit 56 executes the processing of steps S10 and S11, returns to step S2, and executes the processing of step S2 and subsequent steps again.

That is, when the output current Iout reaches the target current Iobj at the time point t1, the process of incrementing the on-time Ton (step S9) or decrementing (step S12) is repeatedly performed, so that the output current Iout becomes the target current Iobj. It is controlled to be constant. With such control, the SOC and the output voltage Vout gradually increase with the passage of time. At the same time, the input power Pin also increases toward the maximum power Pmax. Further, the duty increases slightly with the passage of time.

At time t2 when time T2 has elapsed from time t1, input power Pin reaches maximum power Pmax. In this case, since Pin=Pinold, a negative determination result is obtained in step S5. Therefore, in the next step S14, the charging control unit 56 determines whether or not the duty-up control was executed in the previous process.

When the previous process is duty-up control (step S14: YES), the charging control unit 56 executes step S12 and decrements the on-time Ton by the unit time Δτ. On the other hand, when the previous process is not the duty-up control (step S14: NO), the charge control unit 56 executes the determination process of steps S7 and S8 and then executes step S9 to increment the on-time Ton by the unit time Δτ. To do.

After executing the processing of step S9 or step S12, the charging control unit 56 executes the processing of steps S10 and S11, returns to step S2, and executes the processing of step S2 and subsequent steps again.

That is, when the input power Pin reaches the maximum power Pmax at the time point t2, the input power Pin is equal to the maximum power Pmax by repeatedly performing the process of incrementing the on-time Ton (step S9) or decrementing (step S12). It is controlled to be constant. With this control, the SOC and the output voltage Vout gradually increase over time, while the output current Iout gradually decreases. In addition, the duty decreases slightly with the passage of time.

At time t3 when time T3 has elapsed from time t2, the output voltage Vout reaches the end-of-charge voltage Vobj which is the control target (target voltage) of the secondary battery 26. In this case, since a negative determination result is obtained in step S7 (step S7: NO, Vout=Vobj), in the next step S12, the charging control unit 56 decrements the on time Ton by the unit time Δτ. After that, the charging control unit 56 sequentially executes the processing of steps S13, S10, and S11, returns to step S2, and executes the processing of step S2 and subsequent steps again.

However, since the output voltage Vout has reached the end-of-charge voltage Vobj, a negative determination result is obtained in step S7 even in the subsequent processing (step S7: NO). Therefore, the decrement process of step S12 is performed every time the output voltage Vout reaches the charge termination voltage Vobj during the predetermined prescribed time. As a result, when the output voltage Vout continuously reaches the end-of-charge voltage Vobj and the positive determination result is obtained in step S13 (step S13: YES), the charging control unit 56 determines that It is determined that the charging of the secondary battery 26 is completed, and the on time Ton is set to 0.

After that, the charging control unit 56 executes the processes of steps S10 and S11 (step S11: YES), and outputs a command signal indicating Ton=0 to the step-down control unit 58. The step-down control unit 58 supplies a control signal with a duty of 0 to the MOSFET 40 based on the command signal to turn off the MOSFET 40.

Therefore, the output current Iout, the input power Pin, and the duty decrease from time t3 with the lapse of time by the above-described decrement process for the on-time Ton, and become 0 at time t4 after the time T4 has elapsed from time t3. ..

In the first embodiment, when step S6 of FIG. 5 has a negative determination result (step S6: NO), the input power Pin is increasing, but the duty-up control is not previously executed. Is. In this case, in the drooping characteristic of the input power Pin of FIG. 3, among the two electromotive forces (input voltage Vin) corresponding to the input power Pin existing on both the left and right sides with the maximum power Pmax sandwiched, the input This is a case where the input voltage Vin exists (the operating point is moving) on the lower voltage side than the voltage value Vinmax.

Therefore, in step S12, the charge control unit 56 performs control to decrement the on time Ton to return the input voltage Vin to a higher voltage side than the input voltage value Vinmax.

If Pin≦Pinold (step S5: NO) in step S5 and a negative determination result (step S14: NO) is obtained by the determination process of step S14, the charging control unit 56 determines that the duty is increased. By not executing the control last time, it is determined that the input power Pin is decreasing. After that, the charging control unit 56 executes feedback control according to the output voltage Vout and the like in step S7 and subsequent steps.

On the other hand, when a positive determination result (step S14: YES) is obtained in step S14, the charge control unit 56 executes the duty-up control last time, so that the input power Pin decreases and the input voltage Vin is input. It is determined that the voltage is lower than the voltage value Vinmax. Then, in step S12, the charging control unit 56 decrements the on time Ton and performs feedback control to return the input voltage Vin to the high voltage side.

[Second Embodiment]
Next, a second embodiment will be described with reference to FIGS. It should be noted that the description of the processing common to the first embodiment will be omitted or will be simplified. Further, in the second embodiment, as described above, the secondary battery 26 is charged in a state close to full charge (SOC: 100%), so that the secondary battery 26 is compared with the first embodiment. Keep in mind that the charging time is short.

Also in the second embodiment, because the primary side coil 20 and the secondary side coil 22 are arranged with a gap length between them, and the switch (not shown) on the primary side 12 is turned on at time t5 in FIG. Power can be supplied to the secondary battery 26 by internal control of the secondary side 14.

Also in this case, as in the first embodiment, the on-time Ton is set to 0 in step S1 and then the processes of steps S2 to S11 are repeated, so that the output current Iout increases with time from time t5. , The output voltage Vout, the input power Pin, and the duty (on time Ton) increase.

However, in the second embodiment, at the time t6 when the time T5 has elapsed from the time t5, the output voltage Vout first reaches the end-of-charge voltage Vobj which is the control target (target voltage) of the secondary battery 26.

In this case, since a negative determination result is obtained in step S7 (step S7: NO, Vout=Vobj), the charging control unit 56 decrements the on-time Ton by the unit time Δτ in the next step S12. Next, the charging control unit 56 performs the determination process of step S13. Normally, Ton>0 (step S13: NO), and therefore, the process returns to step S2 via steps S10 and S11.

In this way, when the output voltage Vout reaches the end-of-charge voltage Vobj, the process of incrementing the on-time Ton (step S9) or decrementing (step S12) is repeated, and the output voltage Vout becomes constant at the end-of-charge voltage Vobj. To be controlled.

After that, when the output voltage Vout reaches the end-of-charge voltage Vobj continuously and Ton<0 (step S13: YES), the charge control unit 56 charges the secondary battery 26 during the predetermined specified time. Is judged to have been completed. As a result, the on-time Ton is set to 0 in step S15, and it is determined in step S11 that charging has ended (step S11: YES).

In the second embodiment, the subsequent processing when a negative determination result is obtained in step S6 or when Pin<Pinold is determined in step S5 is the same as in the first embodiment. Further, in FIG. 7, the output voltage Vout is controlled to be constant at the charge end voltage Vobj at the time T6 from the time t6 to the time t7. Further, the decrement process for the on time Ton is executed from the time point t7, and the charging of the secondary battery 26 ends at the time point t8 when the time T7 has elapsed from the time point t7.

[Third Embodiment]
Next, a third embodiment will be described with reference to FIGS. Note that the description of the processing common to the first and second embodiments will be omitted or will be simplified. Further, in the third embodiment, as described above, the maximum electric power Pmax is limited to a low value due to the positional deviation between the primary side coil 20 and the secondary side coil 22 and the large gap length. Therefore, it is necessary to charge the secondary battery 26 more time than in the first and second embodiments.

In the third embodiment as well, similar to the first and second embodiments, the primary coil 20 and the secondary coil 22 are arranged with a gap length between them, and the primary coil is placed at time t9 in FIG. Due to the switch (not shown) on the side 12 being turned on, the power can be supplied to the secondary battery 26 by the internal control of the secondary side 14. Further, similarly to the first and second embodiments, the on-time Ton is set to 0 in step S1 and then the processes of steps S2 to S11 are repeated, so that the time elapses from time t9. The output current Iout, the output voltage Vout, the input power Pin, and the duty (on time Ton) increase.

However, in the third embodiment, the input power Pin first reaches the maximum power Pmax at the time t10 when the time T8 has elapsed from the time t9.

In this case, since a negative determination result is obtained in step S5 (step S5: NO, Pin=Pinold), the charging control unit 56 determines in the next step S14 whether or not the duty-up control was previously executed.

When a negative determination result (step S14: NO) is obtained in step S14, the charge control unit 56 performs a process of incrementing the on-time Ton by the unit time Δτ in step S9 after the processes of steps S7 and S8. .. On the other hand, when a positive determination result (step S14: YES) is obtained in step S14, the charging control unit 56 performs a process of decrementing the on time Ton by the unit time Δτ in step S12. As a result, the input power Pin is controlled to be constant at the maximum power Pmax.

By such control, after the time t10, the SOC and the output voltage Vout gradually increase with the lapse of time, while the output current Iout gradually decreases. In addition, the duty decreases slightly with the passage of time. Then, at time t11 when time T9 has elapsed from time t10, the output voltage Vout reaches the charge end voltage Vobj.

In this case, when the output voltage Vout reaches the end-of-charge voltage Vobj continuously and Ton<0 (step S13: YES) during the predetermined regulation time, the charging control unit 56 controls the secondary battery 26. Judge that charging is complete. As a result, the on-time Ton is set to 0 in step S15, and it is determined in step S11 that charging has ended (step S11: YES).

In the third embodiment, the subsequent processing when a negative determination result is obtained in step S6 or when Pin<Pinold is determined in step S5 is the same as that in the first embodiment. Further, in FIG. 8, the decrement process for the on-time Ton is performed from time t11, and the charging of the secondary battery 26 ends at time t12 when time T10 has elapsed from time t11.

[Modification of this embodiment]
FIG. 9 shows a modification of the power supply system 10 according to this embodiment. This modification is different from the configuration of FIG. 1 in that the voltage conversion circuit 32 is a step-up chopper, and the control section that controls ON/OFF of the MOSFET 40 is the charge control section 56 and the step-up control section 60.

In this case, the voltage conversion circuit 32 as the boost chopper boosts the input voltage Vin from the first smoothing circuit 30. Since the step-up chopper is well known, detailed description thereof will be omitted.

Further, the boost control unit 60 controls ON/OFF of the MOSFET 40 based on the command signal from the charge control unit 56. In this case, the boost controller 60 controls the MOSFET 40 by PWM control.

Also in this modification, the input power Pin has the drooping characteristic shown in FIG. 3, as in the configuration shown in FIG. Further, in the charge control for the secondary battery 26, as shown in FIGS. 2 and 3, the control is performed in the voltage region and the current region between the no-load voltage V0 and the input voltage value Vinmax.

However, in this modified example, since the voltage conversion circuit 32 is a step-up chopper, the discharge end voltage is designed to be equal to or higher than the no-load voltage V0. The other configurations and operations are the same as in the case of FIG. 1, and thus detailed description will be omitted.

In this modification, the diode 42 is connected between the coil 44 and the positive electrode of the secondary battery 26. As a result, backflow from the secondary battery 26 while the voltage conversion circuit 32 stops the boosting operation can be prevented, and inadvertent discharge of the secondary battery 26 can be prevented.

[Effects of this embodiment]
According to the power supply system 10 and the power supply method according to the present embodiment, the control unit 24 reduces the load resistance value from approximately infinity in the initial state with the lapse of time, so that the secondary coil 22 serves as a load. The power supply to the secondary battery 26 is controlled. Therefore, in the present embodiment, the power supply to the secondary battery 26 is performed without exchanging the power supply information between the primary side 12 and the secondary side 14 and without controlling the primary voltage V1. Can be controlled. That is, the control on the power supply to the secondary battery 26 is completed on the secondary side 14 regardless of the state of the primary side 12. As a result, the power supplied from the primary coil 20 to the secondary coil 22 in a non-contact manner can be used to supply power to the secondary battery 26 by simple control on the secondary side 14. it can.

Therefore, in the present embodiment, a feedback means (communication device or the like) from the secondary side 14 to the primary side 12 is unnecessary. Further, the compatibility between the primary side 12 and the secondary side 14 due to the provision of the communication device and the interoperability test for ensuring the compatibility are not necessary. In this way, many processes for ensuring compatibility are unnecessary. Therefore, in this embodiment, the cost of the power supply system 10 can be reduced.

Further, in the control means 24, feedback such that the output current Iout substantially matches the target current Iobj, the output voltage Vout substantially matches the end-of-charge voltage Voobj, and/or the input power Pin substantially matches the maximum power Pmax. By performing the control, it is possible to easily control the power supply to the secondary battery 26. As a result, it is possible to efficiently control the power that can be acquired from the primary side 12.

In this case, among the output current Iout, the output voltage Vout, and the input power Pin, the output current Iout first reaches the target current Iobj, the output voltage Vout first reaches the charge cutoff voltage Vobj, or the input power When Pin reaches the maximum power Pmax for the first time, the control unit 24 controls the output current Iout, the output voltage Vout, or the input power Pin that has reached the first to the target current Iobj, the end-of-charge voltage Voobj, or the maximum power Pmax. Then, the power supply to the secondary battery 26 is continued. This allows the secondary battery 26 to be easily charged.

Further, in the initial state, the load resistance value is made almost infinite by turning off the MOSFET 40 which is a switching element, and thereafter, the ON time Ton of the MOSFET 40 is increased every unit time Δτ to gradually decrease the load resistance value. The power supply to the secondary battery 26 can be easily performed.

Specifically, in the first embodiment of FIG. 6, when the output current Iout reaches the target current Iobj, the output current Iout is controlled to the target current Iobj while increasing or decreasing the duty of the MOSFET 40, and then the input power Pin is maximized. When the electric power Pmax is reached, the input electric power Pin is controlled to the maximum electric power Pmax while increasing/decreasing the duty. Further, when the output voltage Vout reaches the end-of-charge voltage Vobj and the output voltage Vout reaches the end-of-charge voltage Vobj continuously within a specified time, the MOSFET 40 is turned off to control the voltage conversion circuit 32. finish. As a result, when the SOC of the secondary battery 26 is low, the contactless power supply to the secondary battery 26 can be easily performed to complete the charging.

Further, in the second embodiment of FIG. 7, when the output voltage Vout reaches the charge end voltage Vobj, the output voltage Vout is controlled to the charge end voltage Vobj while increasing or decreasing the duty of the MOSFET 40, and then the output voltage Vout is regulated. When the end-of-charge voltage Vobj is continuously reached within the time, the MOSFET 40 is turned off, and the control of the voltage conversion circuit 32 is completed. Accordingly, if the SOC is sufficiently large, the non-contact power supply to the secondary battery 26 can be completed in a short time.

Further, in the third embodiment of FIG. 8, when the input power Pin reaches the maximum power Pmax, the input power Pin is controlled to the maximum power Pmax while increasing/decreasing the duty of the MOSFET 40, and then the output voltage Vout is the end-of-charge voltage. When Vobj is reached and the output voltage Vout continuously reaches the end-of-charge voltage Vobj within the specified time, the MOSFET 40 is turned off, and the control of the voltage conversion circuit 32 is terminated. As a result, even if the maximum power Pmax is set to a small value due to the displacement of the primary coil 20 and the secondary coil 22 or the like, it is possible to easily perform non-contact power supply to the secondary battery 26. it can. As a result, the maximum electric power that can be obtained from the primary side 12 can be easily and efficiently supplied to the secondary battery 26.

In addition, since the voltage conversion circuit 32 includes the MOSFET 40, it is possible to quickly perform voltage conversion from the input voltage Vin to the output voltage Vout in the voltage conversion circuit 32 while suppressing power consumption in the voltage conversion circuit 32.

Further, in the voltage region (current region) between the no-load voltage V0 and the input voltage value Vinmax, the loss of the internal resistance of the secondary side 14 is small and the power use efficiency is high. Therefore, by controlling the voltage conversion circuit 32 in this region, it is possible to perform non-contact power supply to the secondary battery 26 while reducing the loss due to the power supply on the secondary side 14. In addition, even when the electric power that can be supplied to the secondary battery 26 is restricted due to the occurrence of the positional deviation between the primary coil 20 and the secondary coil 22 and the increase in the gap length, the power is still provided. It is possible to supply the maximum electric power to the secondary battery 26 under the constraint condition.

Furthermore, since the primary coil 20 and the secondary coil 22 are electromagnetic induction coils, the power supply to the secondary battery 26 can be easily controlled.

It should be noted that the present invention is not limited to the above-described embodiment, and it is naturally possible to adopt various configurations without departing from the gist of the present invention.

10... Power supply system 12... Primary side 14... Secondary side 16... AC power supply 18... Resistor 20... Primary side coil 22... Secondary side coil 24... Control means 26... Secondary battery 28... Rectifier circuit 30... 1st smoothing circuit 32... Voltage conversion circuit 34... 2nd smoothing circuit 36, 42... Diode 38, 46... Capacitor 40... MOSFET
44... Coil 48, 52... Current sensor 50, 54... Voltage sensor 56... Charge control unit 58... Step-down control unit 60... Step-up control unit

Claims (9)

A primary side coil connected to a primary side power source and a secondary side coil connected to a secondary side load are arranged with a gap, and the primary side coil is not connected to the secondary side coil. In the power supply system that supplies power by contact,
A control unit that is provided between the secondary coil and the load and that controls power supply from the secondary coil to the load;
The control means performs voltage conversion on the rectified output voltage and output current of the secondary coil and the rectified output voltage, and applies the DC voltage that is the converted output voltage to the load. To a voltage conversion circuit, and a control unit for controlling the voltage conversion circuit,
The control unit views the load from the secondary coil in a current region in which an output current flowing from the secondary coil to the load is equal to or less than a current value corresponding to a maximum power operating point of the secondary coil. Starting from an initial state in which the load resistance value is almost infinite, the power supply from the secondary coil to the load is controlled so that the load resistance value decreases with time .
And the control unit, the target current value of the DC current flowing from the voltage conversion circuit to the load, the target voltage value of the DC voltage, and the maximum power value of the output power obtained by multiplying the output voltage after rectification and the output current. Set
If the DC current reaches the target current value before the DC voltage reaches the target voltage value or the output power reaches the maximum power value, the DC current is the target current value. The voltage conversion circuit is controlled so that
If the DC voltage reaches the target voltage value before the DC current reaches the target current value or the output power reaches the maximum power value, the DC voltage is the target voltage value. The voltage conversion circuit is controlled so that
If the output power reaches the maximum power value before the DC current reaches the target current value or the DC voltage reaches the target voltage value, the output power is the maximum power value. The power supply system is characterized in that the voltage conversion circuit is controlled so as to be constant . The power supply system according to claim 1 ,
The voltage conversion circuit is configured to include a switching element,
In the initial state, the control unit makes the load resistance value substantially infinite by turning off the switching element, and then increases the ON time of the switching element at every predetermined unit time, thereby increasing the load. A power supply system characterized by gradually reducing a resistance value. The power supply system according to claim 2 ,
The control unit is
When the DC current reaches the target current value, controlling the DC current to the target current value while increasing or decreasing the duty of the switching element,
After that, when the output power reaches the maximum power value, the output power is controlled to the maximum power value while increasing or decreasing the duty.
Furthermore, when the DC voltage reaches the target voltage value, and when the DC voltage continuously reaches the target voltage value within a specified time, the switching element is turned off to turn off the voltage conversion circuit. A power supply system characterized by terminating control. The power supply system according to claim 2 ,
The control unit is
When the DC voltage reaches the target voltage value, controlling the DC voltage to the target voltage value while increasing or decreasing the duty of the switching element,
After that, when the DC voltage continuously reaches the target voltage value within a specified time, the switching element is turned off, and the control of the voltage conversion circuit is ended. The power supply system according to claim 2 ,
The control unit is
When the output power reaches the maximum power value, controlling the output power to the maximum power value while increasing or decreasing the duty of the switching element,
After that, when the DC voltage reaches the target voltage value, and when the DC voltage continuously reaches the target voltage value within a specified time, the switching element is turned off and the voltage conversion circuit is turned off. A power supply system characterized by terminating control. The power supply system according to any one of claims 2 to 6 ,
The power supply system is characterized in that the switching element is a field effect transistor. The power supply system according to any one of claims 1 to 7 ,
The output power increases with a decrease in the output voltage after rectification, reaches the maximum power value at the maximum power operating point where the product of the output current and the output voltage is maximum, and further the output voltage Has a drooping property that decreases when
The output current after rectification has a characteristic of becoming smaller as the output voltage increases,
In the initial state, the load resistance value is substantially infinite, the output voltage becomes a no-load voltage as a maximum voltage value, the output current is a minimum value,
In the current region, the control unit starts from the no-load voltage, and controls the voltage conversion circuit between the no-load voltage and an output voltage value according to the maximum power operating point. Power supply system. The power supply system according to any one of claims 1 to 7 ,
The power supply system, wherein the primary side coil and the secondary side coil are electromagnetic induction coils. A primary side coil connected to a primary side power source and a secondary side coil connected to a secondary side load are arranged with a gap, and the primary side coil is not connected to the secondary side coil. In the power supply method of supplying power by contact,
Wherein the control means provided between the secondary side coil load, and controls the power supply to the load from the secondary coil,
The control means performs voltage conversion on the rectified output voltage and output current of the secondary coil and the rectified output voltage, and applies the DC voltage that is the converted output voltage to the load. To a voltage conversion circuit, and a control unit for controlling the voltage conversion circuit,
In the current region where the output current flowing from the secondary side coil to the load is equal to or less than the current value corresponding to the maximum power operating point of the secondary side coil, the controller sees the load from the secondary side coil. Starting from an initial state in which the load resistance value is almost infinite, the power supply from the secondary coil to the load is controlled so that the load resistance value decreases with time .
And the control unit, the target current value of the DC current flowing from the voltage conversion circuit to the load, the target voltage value of the DC voltage, and the maximum power value of the output power obtained by multiplying the output voltage after rectification and the output current. Set
If the DC current reaches the target current value before the DC voltage reaches the target voltage value or the output power reaches the maximum power value, the DC current is the target current value. The voltage conversion circuit is controlled so that
If the DC voltage reaches the target voltage value before the DC current reaches the target current value or the output power reaches the maximum power value, the DC voltage is the target voltage value. The voltage conversion circuit is controlled so that
If the output power reaches the maximum power value before the DC current reaches the target current value or the DC voltage reaches the target voltage value, the output power is the maximum power value. The power supply method is characterized in that the voltage conversion circuit is controlled so as to be constant at .

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