JP2018078746A - Wireless power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a wireless power supply device for improving power transmission efficiency, by suppressing a transient voltage rise in a wide region, even when power is supplied wirelessly by using magnetic field resonance.SOLUTION: A wireless power supply device 10 supplies power wirelessly by using magnetic field resonance between a pair of power transmission coils 11 and a power reception coil 12. The wireless power supply device 10 includes a high frequency generation unit 22, a rectification unit 32, two or more switching elements 38, 39, and a control unit 33. The high frequency generation unit 22 supplies high frequency power to the pair of power transmission coils 11. The rectification unit 32 has two or more rectifier cells 34, 35, and rectifies the high frequency power received from the power transmission coils 11 by the power reception coil 12. The switching elements 38, 39 are connected in parallel with the rectifier cells 34, 35. The control unit 33 drives the switching elements 38, 39 while shifting switching timing in the switching elements 38, 39.SELECTED DRAWING: Figure 1

Description

  The present invention relates to a wireless power feeding apparatus that wirelessly supplies power using magnetic field resonance.

  Conventionally, PWM control is known as a method for controlling high-frequency power. In the case of this PWM control, a transient response at the time of switching, that is, a large voltage may be applied instantaneously. Therefore, as in Patent Document 1, it is necessary to take measures such as reducing transient response by supplying current to the capacitor when the pulse width is in a specific condition.

  In the wireless power feeder, when output fluctuation occurs, impedance matching between the power transmission side and the power reception side is lost, and there is a problem that power transmission efficiency is lowered. On the other hand, it is conceivable to arrange a switching element such as a MOSFET in parallel with the rectifying element in the rectifier circuit on the power receiving side. By arranging the switching elements in this way, the rectifier circuit can be directly PWM controlled, and even if output fluctuation occurs, deterioration of impedance matching is avoided.

  Even with such a configuration, the problem that an instantaneous large voltage is generated during operation cannot be solved. A wireless power supply apparatus using magnetic field resonance is driven at a high frequency and uses a drive circuit based on the principle of resonance. For this reason, it is difficult to reduce the transient voltage rise even if the configuration as in Patent Document 1 is used.

JP 2012-231574 A

  SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide a wireless power feeding device that suppresses a transient voltage increase in a wide area and improves power transmission efficiency even when power is supplied wirelessly using magnetic field resonance. It is in.

  In the first aspect of the invention, the switching element is connected in parallel with the rectifying element of the rectifying unit that rectifies the high frequency generated by the power receiving coil. Then, the control unit drives the two or more switching elements connected in parallel to the rectifying element while shifting the switching timing. By shifting the timing of switching in the switching element in this way, rapid changes in voltage and current in the rectifier connected to the power receiving coil are reduced. Therefore, a transient increase in voltage is reduced even in the resonant circuit on the power transmission side. Therefore, even when power is supplied wirelessly using magnetic field resonance, it is possible to suppress a transient increase in voltage in a wide range and improve power transmission efficiency.

Schematic which shows the electrical structure of the wireless power feeder by 1st Embodiment. Schematic which shows the time of ON and OFF of the switching element in the radio | wireless electric power feeder by 1st Embodiment Schematic which shows the relationship between the time of ON and OFF of the switching element and voltage in the wireless power feeder according to the first embodiment Schematic diagram showing the transient voltage when the switching elements are simultaneously turned on, and the transient voltage of the wireless power feeder according to the first embodiment Schematic which shows the electrical structure of the wireless power feeder by 2nd Embodiment. Schematic which shows the electrical structure of the wireless power feeder by 3rd Embodiment Schematic which shows the electrical structure of the wireless power feeder by other embodiment Schematic which shows the electrical structure of the wireless power feeder by other embodiment

Hereinafter, a plurality of embodiments of a wireless power feeder will be described with reference to the drawings. Note that, in a plurality of embodiments, substantially the same components are denoted by the same reference numerals, and description thereof is omitted.
(First embodiment)
FIG. 1 shows a wireless power feeding apparatus 10 according to the first embodiment. The wireless power feeder 10 includes a pair of power transmission coil 11 and power reception coil 12. The wireless power feeder 10 according to the first embodiment wirelessly transmits power to the power receiving coil 12 using magnetic field resonance by supplying high frequency power to the power transmitting coil 11. That is, the wireless power supply apparatus 10 of the first embodiment is a wireless power supply apparatus using magnetic field resonance.

  The power transmission coil 11 constitutes a power transmission circuit unit 20. The power transmission circuit unit 20 includes a capacitor 21 and a high frequency generator 22 in addition to the power transmission coil 11. The power transmission coil 11 and the capacitor 21 constitute an LC circuit. The high frequency generator 22 is an inverter composed of a class E push-pull circuit having a switching element 23, a switching element 24, a coil 25, a coil 26, a capacitor 27 and a capacitor 28. The high frequency generator 22 is connected to the drive signal output unit 29. The drive signal output unit 29 outputs a drive signal whose wavelength is shifted by a half wavelength to the switching element 23 and the switching element 24 of the high-frequency generation unit 22. Therefore, the switching element 23 and the switching element 24 operate in a state shifted by a half wavelength. As a result, the power transmission coil 11 is supplied with high-frequency power generated by the switching element 23 and the switching element 24. Note that an inverter including a class E push-pull circuit is an example of the high-frequency generation unit 22. As long as high frequency electric power can be supplied to the power transmission coil 11, the high frequency production | generation part 22 can employ | adopt arbitrary structures not only in the inverter of a class E push pull circuit.

  The power receiving coil 12 constitutes a power receiving circuit unit 30. In addition to the power receiving coil 12, the power receiving circuit unit 30 includes a capacitor 31, a rectifying unit 32, and a control unit 33. The power receiving coil 12 forms an LC circuit together with the capacitor 31. The rectifier 32 is a rectifier circuit including a class E push-pull circuit having a diode 34, a diode 35, a capacitor 36, a capacitor 37, a switching element 38 and a switching element 39. The rectifying unit 32 is connected to the capacitor 41 and the battery 42. As a result, the high-frequency power received by the power receiving coil 12 is rectified by the diode 34 and the diode 35 of the rectifying unit 32, and the capacitor 41 is charged or the battery 42 is charged. The diode 34 and the switching element 38 which are rectifying elements in the power receiving circuit unit 30 are connected in parallel. Similarly, the diode 35 that is a rectifying element and the switching element 39 are connected in parallel. The rectifying unit 32 of the power receiving circuit unit 30 is not limited to the capacitor 41 and the battery 42 and may be connected to an external load (not shown) that consumes the rectified power.

  The control unit 33 drives the switching element 38 and the switching element 39. The control unit 33 is connected to the A / D converter 43. The control unit 33 is supplied with power from the battery 42 as a power source through the A / D converter 43. The control unit 33 includes a microcomputer configured with, for example, a CPU, a ROM, and a RAM. The control unit 33 outputs drive signals to the two switching elements 38 and 39 and drives the switching elements 38 and 39 by shifting the switching timing. That is, the control unit 33 outputs a driving signal with a phase shift to the switching element 38 and the switching element 38. Thereby, the switching element 38 and the switching element 39 are switched, that is, turned on and off in a state where the switching timing is shifted based on the drive signal output from the control unit 33.

  In the case of the first embodiment, the switching timing of the switching element 38 and the switching element 39 is controlled using the output current Ib output from the diode 34 and the diode 35. In the case of the first embodiment shown in FIG. 1, the power receiving circuit unit 30 includes a shunt resistor 44, an instrumentation amplifier 45, and a comparator 46. The control unit 33 is connected to the instrumentation amplifier 45 and the comparator 46. The shunt resistor 44 is connected to the battery 42 on the output side of the diode 34 and the diode 35. The instrumentation amplifier 45 converts the output current Ib into a voltage waveform at the shunt resistor 44. The comparator 46 compares the voltage waveform converted by the instrumentation amplifier 45 with a predetermined voltage Vt and outputs the voltage waveform to the control unit 33 as a pulse signal. The control unit 33 determines the pulse width of the PWM signal that drives the switching element 38 and the switching element 39 based on the pulse signal input from the comparator 46, that is, the pulse signal correlated with the output current Ib. Then, the control unit 33 outputs a PWM signal according to the determined pulse width, and drives the switching element 38 and the switching element 39.

  As shown in FIG. 2, the switching element 38 and the switching element 39 are turned on and off in accordance with the PWM signal output from the control unit 33. That is, the switching element 38 and the switching element 38 have a PWM period between ON and ON. As described above, the control unit 33 controls the charging current IB for charging the battery 42 from the output current Ib to IB = 2 × Ib by controlling the duty ratio of the PWM signal. Here, in the case of the first embodiment, the timing t1 when the switching element 38 is turned on is slightly different from the timing t2 when the switching element 39 is turned on. That is, the pulse width of the PWM signal output from the control unit 33 to the switching element 38 and the switching element 39 is changed based on the output current Ib. In the example of the first embodiment shown in FIG. 2, the switching element 39 is turned on after the switching element 38 is turned on. Of course, the switching element 38 may be turned on after the switching element 39 is turned on.

  When the switching element 38 is turned on according to the PWM signal output from the control unit 33 in this way, the voltage of the shunt resistor 44, that is, the voltage Vb at both ends of the shunt resistor 44 changes as shown in FIG. That is, the voltage Vb of the shunt resistor 44 temporarily decreases after the switching element 38 is turned on and then increases greatly. The predetermined voltage Vt input to the comparator 46 is set so as to capture a ¼ to ３ period of the transient response period, thereby reducing the transient period.

  FIG. 4 is a simulation example in which the output power is 250 W in the circuit shown in FIG. As is apparent from FIG. 4, when the switching element 38 and the switching element 39 are turned on simultaneously, the transient voltage exceeds 250V and becomes about 260V. On the other hand, the transient voltage is reduced to about 70 V by turning on the switching element 38 and the switching element 39 as in the first embodiment. Thus, it turns out that 1st Embodiment which shifts the time which turns ON the switching element 38 and the switching element 39 is effective for reduction of a transient voltage.

  In the first embodiment, the switching element 38 is connected in parallel with the diode 34 that is a rectifying element of the rectifying unit 32 that rectifies the high frequency received by the power receiving coil 12. Similarly, the switching element 39 is connected in parallel with the diode 35 that rectifies the high frequency received by the power receiving coil 12. Then, the control unit 33 drives the switching timing of the switching element 38 and the switching timing of the switching element 39 to be shifted. In this way, by changing the timing of switching between the switching element 38 and the switching element 39, rapid changes in voltage and current in the rectifying unit 32 connected to the power receiving coil 12 are reduced. Therefore, a transient increase in voltage is also reduced in the power transmission circuit unit 20 that is a resonant power transmission circuit. Therefore, even when power is supplied wirelessly using magnetic field resonance, it is possible to suppress a transient increase in voltage in a wide range and improve power transmission efficiency.

  In the first embodiment, the current rectified in the rectification unit 32 using the shunt resistor 44 and the instrumentation amplifier 45 is converted into a voltage waveform and compared with a predetermined voltage Vt in the comparator 46. The control unit 33 generates a PWM signal based on the predetermined voltage Vt as a drive signal and outputs it to the switching element 38 and the switching element 39. Thus, in the first embodiment, the switching element 38 and the switching element 39 are turned on using the output current Ib from the rectifier 32 in the shunt resistor 44. Therefore, the on-time of the switching element 38 and the switching element 39 can be easily set with a simple configuration of inserting the shunt resistor 44.

(Second and third embodiments)
A wireless power feeding apparatus according to the second embodiment is shown in FIG.
In the case of the second embodiment, the control unit 33 of the wireless power feeding apparatus 10 includes a current sensor 51 that detects an output current Ib output from the diode 34 and the diode 35. That is, in the case of the second embodiment, the control unit 33 detects the output current Ib by the current sensor 51. Thus, the control unit 33 may detect the output current Ib with the current sensor 51. The control unit 33 outputs a PWM signal for driving the switching element 38 and the switching element 39 using a voltage based on the current waveform detected by the current sensor 51.
Also in the second embodiment, the on-time of the switching element 38 and the switching element 39 can be easily set with a simple configuration as in the first embodiment.

A wireless power supply apparatus according to the third embodiment is shown in FIG.
In the case of the third embodiment, the control unit 33 has a storage unit 52. The storage unit 52 stores a shift in the on-time of the switching element 38 and the switching element 39. In this case, the storage unit 52 stores, as a temporal element, a difference between the on-time of the switching element 38 and the on-time of the switching element 39. Further, the control unit 33 may store a certain deviation in the storage unit 52 and always cause a certain deviation using a timer. That is, the storage unit 52 may be a storage medium provided in the control unit 33 or a timer. In the case of the third embodiment as described above, the deviation between the ON timing of the switching element 38 and the ON timing of the switching element 39 is set as a predetermined constant value.

  In the case of the third embodiment, when used for a load that constantly fluctuates, the wireless power supply apparatus 10 does not have high follow-up performance with respect to load fluctuations, but if the load connected to the wireless power supply apparatus 10 is a constant load, a transient voltage Can be reduced. In the third embodiment as described above, the configuration for detecting the output current Ib is not necessary in the wireless power supply apparatus 10 with a constant load, and the transitional voltage change is reduced with a simpler configuration, and the power transmission efficiency is reduced. Can be improved.

(Other embodiments)
The present invention described above is not limited to the above-described embodiment, and can be applied to various embodiments without departing from the gist thereof.
For example, as illustrated in FIG. 7, the wireless power feeding apparatus 10 may use a body diode 61 included in the switching element 38 as a rectifying element instead of the diode 34 in the first embodiment. Similarly, the wireless power feeding apparatus 10 may use a body diode 62 included in the switching element 39 as a rectifying element instead of the diode 35 in the first embodiment. The control unit 33 may set the timing for turning on the switching element 38 and the switching element 39 using the output current Ib output from the body diode 61 of the switching element 38 and the body diode 62 of the switching element 39.

  Further, the wireless power supply apparatus 10 may exclude the AD converter 43 in the first embodiment as shown in FIG. That is, in the case of the wireless power feeder 10 shown in FIG. 8, the PWM control using the voltage Vb of the battery 42 may not be performed. As described above, even with the wireless power feeding apparatus 10 illustrated in FIG. 8, it is possible to suppress a transient voltage increase in a wide range and to improve power transmission efficiency.

  Further, the control unit 33 drives the switching element 38 and the switching element 39 based on the voltage applied to the battery 42 or a load (not shown) instead of the voltage waveform based on the output current Ib output from the diode 34 and the diode 35. It is good also as composition to do. In this case, the control unit 33 is connected to a voltage sensor that detects a voltage in the battery 42 or a load (not shown).

The plurality of embodiments and other embodiments can be applied to the wireless power supply apparatus 10 not only individually but also in combination.
Although the present disclosure has been described with reference to the embodiments, it is understood that the present disclosure is not limited to the embodiments and structures. The present disclosure includes various modifications and modifications within the equivalent range. In addition, various combinations and forms, as well as other combinations and forms including only one element, more or less, are within the scope and spirit of the present disclosure.

  In the drawing, 10 is a wireless power feeding device, 11 is a power transmission coil, 12 is a power receiving coil, 22 is a high-frequency generator, 32 is a rectifier, 33 is a controller, 34 and 35 are diodes (rectifiers), and 38 and 39 are switching. An element, 42 is a battery, 44 is a shunt resistor, 51 is a current sensor, 52 is a storage unit, and 61 and 62 are body diodes (rectifier elements).

Claims (7)

A wireless power feeder (10) that wirelessly supplies power between a pair of power transmission coils (11) and a power reception coil (12),
A high frequency generator (22) for supplying high frequency power to the power transmission coil (11);
A rectification unit (32) having two or more rectification elements (34, 35, 61, 62), and rectifying high-frequency power received from the power transmission coil (11) in the power reception coil (12);
Two or more switching elements (38, 39) connected in parallel with the rectifying elements (34, 35, 61, 62);
A control unit (33) for driving the switching elements (38, 39) by shifting the timing of switching in the two or more switching elements (38, 39);
A wireless power supply apparatus comprising:   The wireless power feeder according to claim 1, wherein the control unit (33) controls a switching timing of the switching element (38, 39) using an output current of the rectifying element (34, 35, 61, 62).   The wireless power feeder according to claim 2, wherein the control unit (33) includes a shunt resistor (44) for detecting an output current of the rectifying element (34, 35, 61, 62).   The wireless power feeder according to claim 2, wherein the control unit (33) includes a current sensor (51) that detects an output current of the rectifying element (34, 35, 61, 62).   The control unit (33) includes a storage unit (52) that stores in advance a shift amount of switching timing in the switching elements (38, 39), and the shift amount stored in the storage unit (52). The wireless power feeder according to claim 1, wherein the switching timing of the switching elements (38, 39) is controlled on the basis of the frequency. At least one of a battery (42) charged by the current rectified by the rectifier (32) and a load driven by the current rectified by the rectifier (32);
The wireless power feeder according to claim 1, wherein the control unit (33) controls a switching timing of the switching element (38, 39) based on a voltage applied to the battery (42) or the load.   The wireless power feeding device according to any one of claims 1 to 6, wherein the rectifying element (34, 35, 61, 62) is a body diode (61, 62) included in the switching element (38, 39).

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