CN107294409B - Active rectifier - Google Patents

Active rectifier Download PDF

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Publication number
CN107294409B
CN107294409B CN201710620901.4A CN201710620901A CN107294409B CN 107294409 B CN107294409 B CN 107294409B CN 201710620901 A CN201710620901 A CN 201710620901A CN 107294409 B CN107294409 B CN 107294409B
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Prior art keywords
comparator
switching element
reference voltage
output
active rectifier
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CN201710620901.4A
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CN107294409A (en
Inventor
宋垠锡
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Jiangxi Celfras Integrated Circuit Co ltd
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Jiangxi Celfras Integrated Circuit Co ltd
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    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02MAPPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M7/219Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only in a bridge configuration
    • HELECTRICITY
    • H02GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02JCIRCUIT ARRANGEMENTS OR SYSTEMS FOR SUPPLYING OR DISTRIBUTING ELECTRIC POWER; SYSTEMS FOR STORING ELECTRIC ENERGY
    • H02J50/00Circuit arrangements or systems for wireless supply or distribution of electric power
    • YGENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y02TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
    • Y02BCLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
    • Y02B70/00Technologies for an efficient end-user side electric power management and consumption
    • Y02B70/10Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Computer Networks & Wireless Communication (AREA)
  • Rectifiers (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention provides an active rectifier which can be used for a wireless charging system. The active rectifier is connected with the first to fourth switching elements in a bridging mode, and each switching element is connected with the comparator and the reference voltage switcher respectively. According to each reference voltage switcher, the time that each switching element operates based on own parasitic capacitance is eliminated, so that the conversion efficiency of the active rectifier can be improved. Accordingly, it is possible to provide a high-efficiency active rectifier that can be used in a system requiring high efficiency while stably operating in a wireless charging system having a wide input current range.

Description

Active rectifier
Technical Field
The present invention relates to an active rectifier for a wireless charging system.
Background
With the development of society, electronic devices are widely used, and the range and number of applications thereof are increasing. Such electronic devices basically require power supply, and various kinds of power devices such as a generator, a power transmitter, a power receiver, and an inverter are required to supply power. The power converter may be classified into a DC/DC (direct current/direct current) converter, a DC/AC (direct current/alternating current) converter, and an AC/DC (alternating current/direct current) converter, and the AC/DC converter is generally referred to as a rectifier.
In recent years, the number of IT devices used in IoT (internet of things) environments such as smartphones, tablet computers, smartwatches, bluetooth headsets, wearable devices, etc. is gradually increasing. Therefore, the demand for wireless charging technology is increasing over the past. Wireless charging or wireless power transmission can be physically divided into a power transmitting side and a power receiving side, and ac power can be transmitted using a coil or an inductance, or the like. The core is a DC/AC converter on the power transmitting side and an AC/DC converter on the power receiving side.
Fig. 1 is a conceptual diagram illustrating a wireless charging system. In the wireless charging system, the power transmission efficiency of the power transmitting side and the power receiving side is very important, and the main factor determining the efficiency is the conversion efficiency of the DC/AC converter 12 and the AC/DC converter 22 (i.e., rectifiers). In a wireless charging system, in order to obtain stable power transmission, a power transmitting side and a power receiving side communicate according to a predetermined standard, and power transmission is performed according to states of the transmitting side and the receiving side. The amount of power transmitted by a power transmitter varies from case to case, and thus, on the receiving side, an AC/DC converter (i.e., a rectifier) that can operate for a wide power range or current range is required.
Fig. 9 shows an active rectifier used in a wireless charging system according to the related art, (a) shows a schematic structural diagram, and (b) shows a timing chart when in operation. As shown in fig. 9 (a), first to fourth switching elements M1 to M4 are connected in a bridging manner, a power receiver 24 is connected between a connection point AC1 between the first switching element M1 and the third switching element M3 and a connection point AC2 between the second switching element M2 and the fourth switching element M4, and first to fourth comparators 201 to 204 are connected to the respective switching elements. Diodes connected in parallel to the four switching elements M1 to M4 represent parasitic capacitances of the respective switching elements. G1 to G4 represent output signals of the first to fourth comparators 201 to 204. As shown in fig. 9 (b), when the voltage at the connection point AC1 falls below the ground potential, taking the connection point ACl and the output G1 of the first comparator 201 as an example, the output G1 of the first comparator 201 becomes high level, the first switching element M1 is turned on, and the other switching elements operate similarly.
However, in the active rectifier shown in fig. 9 (a), for example, the switching element M2 should be turned on immediately after the switching element M1 is turned off, but it is actually difficult to do this because there is a time delay in the feedback control loop including the comparator, which is unavoidable no matter how fast the feedback control is set. During the delay time, since the switching element is not turned on, it operates by its own parasitic capacitance, which causes a decrease in the conversion efficiency of the rectifier.
In addition, in the wireless charging system, in order to improve the AC/DC conversion efficiency of the rectifier, it is necessary to make the impedance of each of the switching elements M1 to M4 in fig. 9 very small, and thus the size of each of the switching elements M1 to M4 becomes large, and in this case, ringing occurs when each of the switching elements is turned on or off. Therefore, the conversion efficiency of the rectifier may be lowered.
Disclosure of Invention
The present invention has been made to solve the above-described problems, and an object thereof is to provide an active rectifier having a wide operating current range for a wireless charging system.
The present invention provides an active rectifier for a wireless power transfer system, the active rectifier characterized by comprising: a first switching element, a second switching element, a third switching element, and a fourth switching element; a first comparator, a second comparator, a third comparator, and a fourth comparator; a first reference voltage switcher, a second reference voltage switcher, a third reference voltage switcher, and a fourth reference voltage switcher; and a first connection point between a first end of the first switching element and a first end of the third switching element, and a second connection point between a first end of the second switching element and a first end of the fourth switching element, wherein a power receiver of the wireless power transmission system is connected between the first connection point and the second connection point, an inverting input end is connected with the first connection point in the first comparator, a non-inverting input end is connected with one end of the first reference voltage switcher, an output end is connected with a second end of the first switching element, in the second comparator, an inverting input end is connected with the second connection point, a non-inverting input end is connected with one end of the second reference voltage switcher, an output end is connected with the first connection point in the third comparator, a non-inverting input end is connected with one end of the third reference voltage switcher, an output end is connected with a second end of the fourth switching element, a non-inverting input end is connected with the second connection point in the fourth comparator, a non-inverting input end is connected with the second reference voltage switcher, a fourth connection point in the fourth comparator, a non-inverting input end is connected with the fourth connection point in the fourth comparator, a fourth connection point is connected with the fourth connection point in the fourth voltage switcher, a non-inverting input end is connected with the fourth connection point.
Preferably, the active rectifier further includes a first holding circuit that controls the first comparator, holds an output of the first comparator for a predetermined period, a second holding circuit that controls the second comparator, holds an output of the second comparator for the predetermined period, a third holding circuit that controls the third comparator, holds an output of the third comparator for the predetermined period, and a fourth holding circuit that controls the fourth comparator, and holds an output of the fourth comparator for the predetermined period.
Preferably, the first holding circuit includes a first edge detector detecting a rising edge or a falling edge of the output signal of the first comparator, the first comparator is controlled for the predetermined period based on a result of the detection, the second holding circuit includes a second edge detector detecting a rising edge or a falling edge of the output signal of the second comparator, the second comparator is controlled for the predetermined period based on a result of the detection, the third holding circuit includes a third edge detector detecting a rising edge or a falling edge of the output signal of the third comparator, the third comparator is controlled for the predetermined period based on a result of the detection, and the fourth holding circuit includes a fourth edge detector detecting a rising edge or a falling edge of the output signal of the fourth comparator, and the fourth comparator is controlled for the predetermined period based on a result of the detection.
Preferably, the first to fourth reference voltage switches are constituted by multiplexers.
Preferably, the first and second switching elements are N-channel type MOS transistors, and the third and fourth switching elements are P-channel type MOS transistors.
Preferably, the first to fourth switching elements are N-channel MOS transistors.
Preferably, the active rectifier further includes a first boost converter connected between the third comparator and the second end of the third switching element, and a second boost converter connected between the fourth comparator and the second end of the fourth switching element.
The present invention also provides an active rectifier for a wireless power transfer system, the active rectifier characterized by comprising: a first switching element, a second switching element, a third switching element, and a fourth switching element; a first comparator and a second comparator; a first reference voltage switcher and a second reference voltage switcher; and a first connection point between a first end of the first switching element and a first end of the third switching element, and a second connection point between a first end of the second switching element and a first end of the fourth switching element, a power receiver of the wireless power transmission system is connected between the first connection point and the second connection point, an inverting input end is connected to the first connection point in the first comparator, a non-inverting input end is connected to one end of the first reference voltage switcher, an output end is connected to a second end of the first switching element, an inverting input end is connected to the second connection point in the second comparator, a non-inverting input end is connected to one end of the second reference voltage switcher, an output end is connected to a second end of the second switching element, the other end of the first reference voltage switcher is connected to the second end of the first switching element, the other end of the second reference voltage switcher is connected to the second end of the second switching element, and the output of the second switching element is connected to the fourth switching element by using the output signal of the fourth switching element.
Preferably, the active rectifier further includes a first holding circuit that controls the first comparator to hold an output of the first comparator for a predetermined period, and a second holding circuit that controls the second comparator to hold an output of the second comparator for the predetermined period.
Preferably, the first holding circuit includes a first edge detector that detects a rising edge or a falling edge of the output signal of the first comparator, the first comparator is controlled for the predetermined period according to a result of the detection, and the second holding circuit includes a second edge detector that detects a rising edge or a falling edge of the output signal of the second comparator, and the second comparator is controlled for the predetermined period according to a result of the detection.
Preferably, the first and second reference voltage switches are constituted by multiplexers.
Preferably, the first and second switching elements are N-channel type MOS transistors, and the third and fourth switching elements are P-channel type MOS transistors.
Preferably, the active rectifier further includes a first inverter and a second inverter, the second end of the third switching element inputs the output signal of the second comparator via the first inverter, and the second end of the fourth switching element inputs the output signal of the first comparator via the second inverter.
Preferably, the first to fourth switching elements are N-channel MOS transistors.
Preferably, the active rectifier further includes a first boost converter and a second boost converter, the second end of the third switching element inputs the output signal of the second comparator via the first boost converter, and the second end of the fourth switching element inputs the output signal of the first comparator via the second boost converter.
According to the present invention, the time for which the active rectifier operates by means of the parasitic capacitance of the switching element can be eliminated or minimized, and the ringing phenomenon can be effectively suppressed, whereby the conversion efficiency of the active rectifier can be improved. Accordingly, it is possible to provide a high-efficiency active rectifier that can be used in a system requiring high efficiency while stably operating in a wireless charging system having a wide input current range.
Drawings
Fig. 1 is a conceptual diagram illustrating a wireless charging system.
Fig. 2 is a schematic diagram showing an active rectifier according to embodiment 1 of the present invention.
Fig. 3 is a timing chart of the active rectifier when each switching element is turned on, (a) shows a delay of the on time of each switching element in the prior art configuration, and (b) shows a schematic diagram of suppressing the delay of the on time of each switching element in the configuration of fig. 2 according to the present invention.
Fig. 4 is a timing chart of the switching elements of the active rectifier when turned on, (a) shows a ringing phenomenon in the prior art configuration, and (b) shows an effect diagram of suppressing the ringing phenomenon in the configuration of fig. 2 according to the present invention.
Fig. 5 (a) is a schematic diagram showing the structure of the reference voltage switcher of the present invention, and (b) is a timing chart showing the reference voltage switcher.
Fig. 6 is a schematic diagram showing an active rectifier according to modification 1 of the present invention.
Fig. 7 is a schematic diagram showing an active rectifier according to embodiment 2 of the present invention.
Fig. 8 is a schematic diagram showing an active rectifier according to modification 2 of the present invention.
Fig. 9 shows an active rectifier used in a wireless charging system according to the related art, (a) shows a schematic structural diagram, and (b) shows a timing chart when in operation.
Detailed Description
In the following description, specific configurations and descriptions are merely descriptions for easier understanding of the present invention, and the present invention can be implemented in various forms and is not limited to the forms described in the present specification. Further, various changes, modifications, and the like may be made to the present invention within the scope of the technical idea of the present invention, and these changes, modifications, and the like are included in the scope of the present invention.
In the following description, terms such as "first" and "second" may be used to describe specific components, but these terms are not limited to these components. These terms are only used to distinguish between the components. In addition, any one of the components used in the present specification may be connected or linked to another component, and may be directly connected or indirectly connected. In addition, the same or similar constituent elements are given the same reference numerals.
Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
Embodiment 1
Fig. 1 is a conceptual diagram illustrating a wireless charging system, and fig. 2 is a schematic diagram illustrating an active rectifier according to embodiment 1 of the present invention, and is a schematic diagram illustrating a specific configuration of an AC/DC converter (i.e., rectifier) 22 in fig. 1.
As shown in fig. 2, the active rectifier 22 (hereinafter, may be simply referred to as a rectifier) includes: the first to fourth switching elements MI to M4, the first to fourth comparators 201 to 204, the first to fourth reference voltage switches 211 to 241, the connection point AC1 between the first switching element M1 and the third switching element M3, and the connection point AC2 between the second switching element M2 and the fourth switching element M4. Diodes connected in parallel with the first to fourth switching elements M1 to M4 represent parasitic capacitances of the respective switching elements themselves. A power receiver 24 is connected between the connection point AC1 and the connection point AC2, and the power receiver 24 may be constituted by an inductor and a capacitor, and is not particularly limited in the present invention. As shown in fig. 2, the rectifier 22 may further include first to fourth holding circuits 212 to 242 and first to fourth edge detectors 213 to 243. The rectifier 22 supplies the AC/DC converted power to a load.
As shown in fig. 2, the first switching element M1 and the second switching element M2 are N-channel MOS transistors, and the third switching element M3 and the fourth switching element M4 are P-channel MOS transistors. Taking the first switching element M1 as an example, the gate thereof is connected to the output terminal of the first comparator 201, and is also connected to one end of the first reference voltage switch 211 and one end of the first holding circuit 212, the drain thereof is connected to the connection point AC1, and the source thereof is grounded; an inverting input terminal of the first comparator 201 is connected to the connection point AC1, and a non-inverting input terminal thereof is connected to the other end of the first reference voltage switcher 211. The connection of the second to fourth switching elements M2 to M4 is also similar to the first switching element M1, and thus a description thereof will not be repeated here. In fig. 2, G1 to G4 represent output signals of the first to fourth comparators 201 to 204, and VRECT represents a high-level side voltage of the load. The configuration of the first to fourth reference voltage switches 211 to 241 will be described later.
Fig. 3 is a timing chart of the active rectifier when each switching element is turned on, (a) shows a delay of the on time of each switching element in the prior art configuration, and (b) shows a schematic diagram of suppressing the delay of the on time of each switching element in the configuration of fig. 2 according to the present invention.
In the configuration of the related art shown in fig. 9, when the connection point AC2 is lowered below 0V (ground potential) after the first switching element M1 is turned off (i.e., G1 is at a low level), the second switching element M2 should be turned on immediately, but it is actually difficult to do so. This is because there is a delay in the feedback control loop including the comparator. That is, no matter how fast the feedback control including the comparator is designed, there is still a delay. During the delay time, the second switching element M2 cannot be turned on and can only operate by means of its parasitic capacitance, so that the conversion efficiency of the rectifier is reduced. The same is true for other switching elements. Fig. 3 (a) shows the case where the broken line indicates the timing at which the switching element should be turned on in the prior art configuration, and the solid line indicates the timing at which the switching element is actually turned on in the prior art.
In order to solve this problem, fig. 3 (b) shows the effect of the present invention by changing the reference input of each comparator according to the operation phase, wherein the broken line indicates the time at which each switching element is actually turned on in the prior art, and the solid line indicates the time at which each switching element is turned on in the configuration of the present invention, and it is known that the on time of each switching element is significantly advanced compared to the prior art. Specifically, by providing the first to fourth reference voltage switches 211 to 241, the input voltage of the non-inverting input terminal of each comparator is controlled. In fig. 3 (b), vref_g1 represents the output of the first reference voltage switcher 211, and vref_g2 represents the output of the second reference voltage switcher 221. For convenience of explanation, fig. 3 (b) shows only the output signals of the first and second reference voltage switches, and the output signals of the third and fourth reference voltage switches are the same principle.
As shown in fig. 3 (b), for example, taking the first switching element M1 and the second switching element M2 as an example, when the output G1 of the first comparator 201 becomes low level and the first switching element M1 is turned off and the voltage of the connection point AC2 decreases, the output vref_g2 of the second reference voltage switcher 221 is high, so that even if the voltage of the connection point AC2 does not decrease by 0V, the feedback control is triggered to make the second switching element M2 conduct in advance. Thus, the passive mode time of the rectifier operating based on the parasitic capacitance of the switching element due to feedback control can be eliminated or minimized. Here, the delay time required for vref_g2 to become 0V does not affect the overall operation of the rectifier. This is because there is a sufficient time for the second switching element M2 until the comparison of the reference level of 0V of the second comparator 202 for the next turn-on. The same principle applies to the third switching element M3 and the fourth switching element M4. As shown in fig. 3 (b), the on-time of each switching element is advanced as compared with the conventional art, and therefore the conversion efficiency of the rectifier can be improved.
Fig. 4 is a timing chart of the switching elements of the active rectifier when turned on, (a) shows a ringing phenomenon in the prior art configuration, and (b) shows an effect diagram of suppressing the ringing phenomenon in the configuration of fig. 2 according to the present invention.
In the conventional configuration shown in fig. 9, when the size of each of the switching elements M1 to M4 is increased in order to improve the AC/DC conversion efficiency of the rectifier, ringing occurs when each of the switching elements is turned on or off as shown in fig. 4 (a).
In the present embodiment, in order to solve this problem, first to fourth holding circuits 212 to 242 are provided. As shown in fig. 4 (b), for example, when the 1 st switching element M1 is turned on, the function of the first comparator 201 is disabled for a predetermined period, and the output G1 is held for a predetermined period by the first holding circuit 212, thereby eliminating the ringing phenomenon. The same principle applies to the second to fourth switching elements. The first to fourth holding circuits 212 to 242 may further include first to fourth edge detectors 213 to 243, respectively, each of which detects a rising edge or a falling edge of the output signal of each of the comparators. Based on the detection results of the edge detectors, the comparators are controlled so that the outputs of the comparators are maintained for a predetermined time. As can be seen from fig. 4, the ringing phenomenon is significantly improved compared with the prior art, whereby the conversion efficiency of the rectifier can be improved.
Fig. 5 (a) is a schematic diagram showing the structure of the reference voltage switcher of the present invention, and (b) is a timing chart showing the reference voltage switcher. As shown in fig. 5 (a), the reference voltage switch may be formed by a multiplexer, for example, the first reference voltage switch 211 receives the output G1 of the first comparator 201 as a selection signal of the multiplexer, and generates vref_g1 as a non-inverting input signal of the first comparator 201. At this time, VREF1 is 0V, that is, grounded, and VREF2 is a voltage greater than 0V, and may be set appropriately according to actual needs, and is not particularly limited in the present application. Fig. 5 (b) is a timing diagram of the first reference voltage switch 211. In fig. 5, the first reference voltage switch 211 is illustrated as an example, but the structure and timing of other reference voltage switches are similar, and thus the illustration is omitted.
Modification 1
Fig. 6 is a schematic diagram showing an active rectifier according to modification 1 of the present invention. The difference compared to the structure of fig. 2 is that in the rectifier 22' shown in fig. 6, the third and fourth switching elements M3', M4' are also N-channel MOS transistors. When an N-channel MOS transistor is used on the high-level side of the load, the power supply device is applicable to a high-voltage and high-power wireless charging system, and can improve the conversion efficiency of a rectifier. Since the N-channel MOS transistors are used on the high-level side, the outputs of the third comparator 203 and the fourth comparator 204 are boosted by the first boost converter 234 and the second boost converter 244 and then applied to the gates of the third and fourth switching elements M3', M4'. Other structures and effects are the same as those of the rectifier of fig. 2, and thus duplicate explanation is omitted.
Embodiment 2
Fig. 7 is a schematic diagram showing an active rectifier according to embodiment 2 of the present invention. In comparison with the structure of fig. 2, the rectifier 42 shown in fig. 7 is different in that only the first switching element M1 and the second switching element M2 sides have reference voltage switches (411 and 421). An output G2 of the second comparator 202 is input via the first inverter 431 on the gate side of the third switching element M3; on the gate side of the fourth switching element M4, the output G1 of the first comparator 201 is input via the second inverter 441. In addition, the rectifier 42 may further have first and second holding circuits 412, 422, first and second edge detection circuits 413, 423. Other structures and effects are the same as those of the rectifier of fig. 2, and thus duplicate explanation is omitted.
Compared with the active rectifier 22 of fig. 2, since the third and fourth comparators, the third and fourth reference voltage switches, and the third and fourth holding circuits are omitted on the third and fourth switching element side (i.e., the high level side), the outputs G1, G2 of the first and second comparators are shared, and thus the circuit can be simplified.
Modification 2
Fig. 8 is a schematic diagram showing an active rectifier according to modification 2 of the present invention. The difference from the structure of fig. 7 is that in the rectifier 42' shown in fig. 8, the third and fourth switching elements M3', M4' are also N-channel MOS transistors. When an N-channel MOS transistor is used on the high-level side of the load, the power supply device is applicable to a high-voltage and high-power wireless charging system, and can improve the conversion efficiency of a rectifier. Since the N-channel MOS transistor is also used on the high-level side, an inverter is not required, and the output G2 'of the second comparator 202 is supplied to the gate of the third switching element M3' through the first boost converter 432, and the output G1 'of the first comparator 201 is supplied to the gate of the fourth switching element M4' through the second boost converter 442. Other structures and effects are the same as those of the rectifier of fig. 7, and thus duplicate explanation is omitted.
While the specific embodiments of the present invention have been described in detail, the present invention is not limited to the above description, and modifications, improvements, etc. within the scope of the technical idea of the present invention are all within the scope of the present invention.

Claims (15)

1. An active rectifier for a wireless power transfer system, the active rectifier comprising:
a first switching element, a second switching element, a third switching element, and a fourth switching element;
a first comparator, a second comparator, a third comparator, and a fourth comparator;
a first reference voltage switcher, a second reference voltage switcher, a third reference voltage switcher, and a fourth reference voltage switcher; and
a first connection point between the first end of the first switching element and the first end of the third switching element, and a second connection point between the first end of the second switching element and the first end of the fourth switching element,
a power receiver of the wireless power transfer system is connected between the first connection point and the second connection point,
in the first comparator, an inverting input terminal is connected with the first connection point, a non-inverting input terminal is connected with one end of the first reference voltage switcher, an output terminal is connected with a second terminal of the first switching element,
in the second comparator, an inverting input terminal is connected to the second connection point, a non-inverting input terminal is connected to one end of the second reference voltage switcher, an output terminal is connected to the second terminal of the second switching element,
in the third comparator, an inverting input terminal is connected to the first connection point, a non-inverting input terminal is connected to one end of the third reference voltage switcher, an output terminal is connected to the second terminal of the third switching element,
in the fourth comparator, an inverting input terminal is connected with the second connection point, a non-inverting input terminal is connected with one end of the fourth reference voltage switcher, an output terminal is connected with the second terminal of the fourth switching element,
the other end of the first reference voltage switcher is connected with the second end of the first switching element and is connected with the output end of the first comparator, the first reference voltage switcher receives the output of the first comparator as a selection signal and generates a non-inverting input end input signal of the first comparator,
the other end of the second reference voltage switcher is connected with the second end of the second switching element and is connected with the output end of the second comparator, the second reference voltage switcher receives the output of the second comparator as a selection signal and generates a non-inverting input end input signal of the second comparator,
the other end of the third reference voltage switcher is connected with the second end of the third switching element and is connected with the output end of the third comparator, the third reference voltage switcher receives the output of the third comparator as a selection signal and generates a non-inverting input end input signal of the third comparator,
the other end of the fourth reference voltage switcher is connected with the second end of the fourth switching element and the output end of the fourth comparator, and the fourth reference voltage switcher receives the output of the fourth comparator as a selection signal and generates a non-inverting input end input signal of the fourth comparator.
2. The active rectifier of claim 1,
also comprises a first holding circuit, a second holding circuit, a third holding circuit and a fourth holding circuit,
the first holding circuit controls the first comparator to hold an output of the first comparator for a predetermined period,
the second holding circuit controls the second comparator to hold the output of the second comparator for the predetermined period,
the third holding circuit controls the third comparator to hold an output of the third comparator for the predetermined period,
the fourth holding circuit controls the fourth comparator to hold an output of the fourth comparator for the predetermined period.
3. An active rectifier according to claim 2, characterized in that,
the first holding circuit includes a first edge detector that detects a rising edge or a falling edge of an output signal of the first comparator, controls the first comparator for the predetermined period based on a result of the detection,
the second holding circuit includes a second edge detector that detects a rising edge or a falling edge of an output signal of the second comparator, controls the second comparator for the predetermined period based on a result of the detection,
the third holding circuit includes a third edge detector that detects a rising edge or a falling edge of an output signal of the third comparator, controls the third comparator for the predetermined period based on a result of the detection,
the fourth holding circuit includes a fourth edge detector that detects a rising edge or a falling edge of an output signal of the fourth comparator, and controls the fourth comparator for the predetermined period based on a result of the detection.
4. An active rectifier according to any one of claims 1 to 3,
the first to fourth reference voltage switches are constituted by multiplexers.
5. An active rectifier according to any one of claims 1 to 3,
the first and second switching elements are N-channel MOS transistors,
the third switching element and the fourth switching element are P-channel MOS transistors.
6. An active rectifier according to any one of claims 1 to 3,
the first to fourth switching elements are N-channel MOS transistors.
7. The active rectifier of claim 6,
a first boost converter and a second boost converter are also included,
the first boost converter is connected between the third comparator and the second end of the third switching element,
the second boost converter is connected between the fourth comparator and the second end of the fourth switching element.
8. An active rectifier for a wireless power transfer system, the active rectifier comprising:
a first switching element, a second switching element, a third switching element, and a fourth switching element;
a first comparator and a second comparator;
a first reference voltage switcher and a second reference voltage switcher; and
a first connection point between the first end of the first switching element and the first end of the third switching element, and a second connection point between the first end of the second switching element and the first end of the fourth switching element,
a power receiver of the wireless power transfer system is connected between the first connection point and the second connection point,
in the first comparator, an inverting input terminal is connected with the first connection point, a non-inverting input terminal is connected with one end of the first reference voltage switcher, an output terminal is connected with a second terminal of the first switching element,
in the second comparator, an inverting input terminal is connected to the second connection point, a non-inverting input terminal is connected to one end of the second reference voltage switcher, an output terminal is connected to the second terminal of the second switching element,
the other end of the first reference voltage switcher is connected with the second end of the first switching element and is connected with the output end of the first comparator, the first reference voltage switcher receives the output of the first comparator as a selection signal and generates a non-inverting input end input signal of the first comparator,
the other end of the second reference voltage switcher is connected with the second end of the second switching element and is connected with the output end of the second comparator, the second reference voltage switcher receives the output of the second comparator as a selection signal and generates a non-inverting input end input signal of the second comparator,
the output signal of the second comparator is used at the second end of the third switching element and the output signal of the first comparator is used at the second end of the fourth switching element.
9. The active rectifier of claim 8,
further comprising a first holding circuit and a second holding circuit,
the first holding circuit controls the first comparator to hold an output of the first comparator for a predetermined period,
the second holding circuit controls the second comparator to hold an output of the second comparator for the predetermined period.
10. The active rectifier of claim 9,
the first holding circuit includes a first edge detector that detects a rising edge or a falling edge of an output signal of the first comparator, controls the first comparator for the predetermined period based on a result of the detection,
the second holding circuit includes a second edge detector that detects a rising edge or a falling edge of an output signal of the second comparator, and controls the second comparator for the predetermined period according to a result of the detection.
11. An active rectifier according to any one of claims 8 to 10,
the first and second reference voltage switches are constituted by multiplexers.
12. An active rectifier according to any one of claims 8 to 10,
the first and second switching elements are N-channel MOS transistors,
the third switching element and the fourth switching element are P-channel MOS transistors.
13. The active rectifier of claim 12,
a first inverter and a second inverter are also included,
a second terminal of the third switching element inputs the output signal of the second comparator via the first inverter,
the second end of the fourth switching element inputs the output signal of the first comparator via the second inverter.
14. An active rectifier according to any one of claims 8 to 10,
the first to fourth switching elements are N-channel MOS transistors.
15. The active rectifier of claim 14,
a first boost converter and a second boost converter are also included,
a second terminal of the third switching element inputs the output signal of the second comparator via the first boost converter,
the second end of the fourth switching element inputs the output signal of the first comparator via the second boost converter.
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