Patent Application
20160308398
The present invention relates to a rectifying circuit for high-frequency power supply that rectifies an alternating current power supply at a high frequency.
A class E rectifier circuit according to a conventional technology, for use in rectification in a kHz band, is shown in
Nonpatent reference
However, a problem is that when the conventional configuration is applied to the rectification at a high frequency equal to or higher than a MHz band, the power conversion efficiency is poor. Particularly, in a case where a circuit, such as a resonant type reception antenna, which has high frequency characteristics in its output impedance is connected to the input side, an influence is exerted upon the operation of the class E rectifier circuit itself, and an efficient power conversion operation which is an essential object cannot be maintained.
The power loss in the circuit which occurs at the time of the rectifying operation results in heat energy and hence a temperature rise of the circuit board. This results in an increase in the operating environment temperature of the circuit board and hence a reduction in the life of the used parts. Therefore, a measure, such as a measure of providing an exhaust heat device, is needed, and the conventional configuration also causes an increase in cost, upsizing, and an increase in mass.
The present invention is made in order to solve the above-mentioned problems, and it is therefore an object of the present invention to provide a rectifying circuit for high-frequency power supply that can provide a high power conversion efficiency characteristic in rectification of an alternating voltage at a high frequency equal to or higher than 2 MHz
According to the present invention, there is provided a rectifying circuit for high-frequency power supply that rectifies an alternating voltage at a high frequency equal to or higher 2 MHz, the rectifying circuit for high-frequency power supply including: a class E rectifier circuit that rectifies the alternating voltage inputted from a reception antenna for power transmission; a resonant circuit that causes the class E rectifier circuit to perform resonant switching in a switching operation at a time of rectification; a matching functional circuit that has a function of matching a resonance condition to that of the reception antenna for power transmission, and a function of matching the resonance condition to that of the resonant circuit; and a smoothing functional circuit that smooths the voltage rectified by the class E rectifier circuit into a direct voltage.
Because the rectifying circuit for high-frequency power supply according to the present invention is configured as above, a high power conversion efficiency characteristic can be provided in the rectification of the alternating voltage at a high frequency equal to or higher than 2 MHz.
Hereafter, the preferred embodiments of the present invention will be explained in detail with reference to the drawings.
The rectifying circuit for high-frequency power supply rectifies an alternating voltage Vin at a high frequency equal to or higher 2 MHz. This rectifying circuit for high-frequency power supply is configured with a diode D1, capacitors C1 and C2, an inductor L21, a capacitor C21, an inductor L11 and a capacitor C11, as shown in
A resonant type reception antenna (a reception antenna for power transmission) 10 is a resonant type antenna for power transmission having LC resonance characteristics (which is not limited only to a noncontact type one). This resonant type reception antenna 10 can be of any of magnetic-field resonance type, electric-field resonance type, and electromagnetic induction type.
The diode D1 is a rectifying element that constructs a class E rectifier circuit for converting the alternating voltage Vin at a high frequency equal to or higher than 2 MHz, which is inputted from the resonant type reception antenna 10, into a direct voltage. As the diode D1, not only a diode for high frequency (RF; Radio Frequency) but also an element, such as a diode of, for example, Si type, SiC type or GaN type, or a Schottky barrier diode, can be used.
The capacitors C1 and C2 and the inductor L21 construct a resonant circuit for a class E rectifying operation in the diode D1 by a compound function. This resonant circuit causes the diode D1 to perform resonant switching in a switching operation at the time of rectification of the diode D1. The capacitor C1 is a constant that consists of either the parasitic capacitance of the diode D1 or a combined capacitance of the parasitic capacitance and the capacitance of a discrete element. Further, as the capacitor C2, a ceramic capacitor or a film capacitor or the like can be used. Further, as the inductor L21, an air-core coil, a magnetic material coil or the like can be used.
The capacitor C21 is an element that constructs a smoothing functional circuit for smoothing a ripple voltage after being rectified by the diode D1 into a direct voltage. As the capacitor C21, an element, such as a ceramic capacitor, a tantalum capacitor or a film capacitor, can he used.
The inductor L11 and the capacitor C11 are elements that construct a matching functional circuit having a function of performing impedance matching with the resonant type reception antenna 10 on an input side (matching the resonance condition to that of the resonant type reception antenna 10), and a function for performing impedance matching with the resonant circuit by the capacitors C1 and C2 and the inductor L21 (matching the resonance condition to that of the resonant circuit). As the inductor L11, an air-core coil, a magnetic material coil or the like can be used. In addition, as the capacitor C11, an element, such as a ceramic capacitor, a tantalum capacitor or a film capacitor, can be used. By virtue of the inductor L11 and the capacitor C11, a resonant switching operation can be implemented by the diode D1.
The rectifying circuit for high-frequency power supply according to the present invention is configured in this way so as to include the three functions (the matching function, the class E rectifying function and the smoothing function) in the single circuit configuration which is not established by using a circuit designing method of keeping those functions separated. Then, the rectifying circuit for high-frequency power supply has a function of performing matching with the output impedance of the resonant type reception antenna 10 and also performing matching with the impedance of the resonant circuit configured with the capacitors C1 and C2, and the inductor L21 by using a compound function according to the inductor L1 and the capacitor C11, and also has a function of performing the diode D1 to perform the resonant switching in the switching operation at the time of rectification by using the resonant circuit. As a result, the switching loss of the diode D1 is reduced.
Next, the operation of the rectifying circuit for high-frequency power supply configured as above will be explained.
First, when the alternating voltage Vin having a high frequency equal to or higher 2 MHz is inputted from the resonant type reception antenna 10, matching with the output impedance of the resonant type reception antenna 10 and impedance matching with the impedance of the resonant circuit configured with the capacitors C1 and C2, and the inductor L21 are achieved by the compound function according to the inductor L11 and the capacitor C11. Then, while the matching state is maintained, the inputted alternating voltage Vin is rectified into a ripple voltage having a one-sided electric potential (a positive electric potential) by the capacitor C2 and diode D1. At that time, because the switching operation by the diode D1 becomes resonant switching operation by virtue of the compound function according to the capacitors C1 and C2 and the inductor L21, and enters a ZVS (zero voltage switching) state. This state is a class E rectifying operation, so that the operation is implemented with a small switching loss. Then, the ripple voltage after being rectified is smoothed into a direct voltage by the capacitor C21, and the direct voltage is outputted.
Through the above-mentioned series of operations, the rectifying circuit for high-frequency power supply can rectify the inputted alternating voltage Vin having a high frequency into a direct voltage with high power conversion efficiency (equal to or greater than 90%) , and output the direct voltage.
As mentioned above, because the rectifying circuit for high-frequency power supply according to this Embodiment 1 is configured in such a way as to include the function of performing impedance matching with a circuit having a high frequency characteristic in its output impedance, such as the resonant type reception antenna 10, and the function of operating as a part of the resonance operation of the class E rectifier circuit thereof, the loss at the time of the rectifying operation at a high frequency equal to or higher than a MHz band can be greatly reduced, and high power conversion efficiency (efficiency of 90% or more) can be achieved.
Further, because the power loss in the circuit which occurs at the time of the rectifying operation is small, and hence the heat energy generated is also small and the temperature rise of the circuit board is suppressed to a low value, the influence of the operating environment temperature on the life of the used parts can be reduced. Therefore, measure, such as a measure of providing a conventional exhaust heat device, is not needed, and a cost reduction, downsizing, a weight reduction and low power consumption can be achieved.
Incidentally, the case in which the rectifying circuit for high-frequency power supply is configured using the diode D1, the capacitors C1 and C2, the inductor L21, the capacitor C21, the inductor L11 and the capacitor C11 is shown in
Further, although the explanation is made as to the example shown in
The variable resonance condition LC circuit 1 can be applied similarly to the examples shown in
The power element Q1 is a rectifying element that constructs a class E rectifier circuit for converting an alternating voltage Vin at a high frequency equal to or higher than 2 MHz, which is inputted from a resonant type reception antenna 10, into a direct voltage. As the power element not only a field effect transistor for RF (FET: Field Effect Transistor) but also an element, such as a Si-MOSFET, a SiC-MOSFET or a GaN-FETs, can be used. A capacitor C1 consists of either the parasitic capacitance of the power element Q1 or a combined capacitance of the parasitic capacitance and the capacitance of a discrete element.
Even in the case in which the rectifying circuit for high-frequency power supply is configured using the power element Q1 in this way, instead of using the diode D1, the same advantages as those provided by Embodiment 1 can be provided.
The configuration in which the diode D1 shown in
Further, although the explanation is made as to the example shown in
Further, the case in which the diode D1 is used as the rectifying element is shown in Embodiment 1 while the case in which the power element Q1 is used as the rectifying element is shown in Embodiment 2. In contrast with this, both the diode D1 and the power element Q1 can be used as the rectifying element as shown in
In addition, while the invention has been described in its preferred embodiments, it is to be understood that an arbitrary combination of two or more of the embodiments can be made, various changes can be made in an arbitrary component according to any one of the embodiments, and an arbitrary component according to anyone of the embodiments can be omitted within the scope of the invention.
The rectifying circuit for high-frequency power supply according to the present invention can provide a high power conversion efficiency characteristic in the rectification of an alternating voltage at a high frequency equal to or higher than 2 MHz, and is suitable for use as a rectifying circuit for high-frequency power supply or the like that rectifies an alternating current power supply at a high frequency.
1 variable resonance condition LC circuit, and 10 resonant type reception antenna (reception antenna for power transmission).
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/JP2013/083097 | 12/10/2013 | WO | 00 |
