Master-slave voltage doubling full-wave rectifier for wireless power transfer system

1. Technical Field

The invention relates to rectifiers, particularly to voltage doubling full-wave rectifiers.

2. Related Art

A rectifier is used for converting AC power to DC power and can be applied in many fields. Rectification of rectifiers can divided into three species as follows:

1. The first species is passive rectifying circuitry, i.e., a half-wave or full-wave rectifying circuit composed of diodes. Its conversion efficiency is about 55%˜65%.

2. The second species is voltage doubling rectifying circuitry, which utilizes multi-staged half-wave rectifying circuit to obtain higher DC voltage output and conversion efficiency. Its conversion efficiency is about 75%.

3. The third species is active rectifying circuitry, which is composed of various solid state electronic switches and comparators. Loss of power conversion can be reduced by the comparators so as to reach conversion efficiency of 85%˜96%.

The conversion efficiency of the active rectifying circuitry is high enough, but its circuitry framework is very complicated. Contrarily, the passive rectifying circuitry is so simple in structure, but its conversion efficiency is the worst among others.

Recently, wireless charge technology has fast development and is extensively applied to portable electronic devices such as smartphones and tablets. Wireless charge must use a rectifier and portable electronic devices must emphasize using efficiency of battery and limitation of volume and weight. Thus, a rectifier with high efficiency and simple structure is urgently necessary.

An object of the invention is to provide a master-slave voltage doubling full-wave rectifier, which can reach relatively high conversion efficiency by means of a relatively simple circuitry.

To accomplish the above object, the master-slave voltage doubling full-wave rectifier of the invention includes:

a first electronic switch, having a first control end and two first contact ends, wherein the two first contact ends separately connect a ground end and a first end of an AC (alternating current) power source, and the first control end connects a second end of the AC power source;

a second electronic switch, having a second control end and two contact ends, wherein the two second contact ends separately connect the ground end and the second end of the AC power source, and the second control end connects the first end of the AC power source;

a first diode, having a positive end connecting the first end of the AC power source;

a second diode, having a positive end connecting the second end of the AC power source;

a first capacitor, connected between the second end of the AC power source and a negative end of the first diode;

a second capacitor, connected between the first end of the AC power source and a negative end of the second diode;

a third diode, having a positive end connecting the negative end of the first diode;

a fourth diode, having a positive end connecting the negative end of the second diode;

a third capacitor, connected between the second end of the AC power source and a negative end of the third diode;

a fourth capacitor, connected between the first end of the AC power source and a negative end of the fourth diode;

a fifth diode, having a positive end connecting the negative end of the third diode;

a sixth diode, having a positive end connecting the negative end of the fourth diode and a negative end connecting a negative end of the fifth diode to form a voltage output end; and

a filter capacitor, connected between the voltage output end and the ground end.

FIG. 1 is a circuit diagram of the invention;

FIG. 2 is an equivalent circuit diagram of the invention in positive half cycle input;

FIG. 3 is an equivalent circuit diagram of the invention in negative half cycle input; and

FIG. 4 is a circuit diagram of another embodiment of the invention.

Please refer to FIG. 1 . The invention provides a master-slave voltage doubling full-wave rectifier, which primarily includes a master-stage full-wave rectifying circuit (composed of two diodes D 1 and D 2 and two electronic switches S 1 and S 2 ) and a slave-stage auxiliary charging circuit (composed of four diode D 3 -D 6 and four capacitors C 1 ˜C 4 ). Because of the phase division switching by the electronic switches, the DC voltage and conversion efficiency can be increased. And opposite voltage polarity of positive and negative half cycles further makes the capacitors double voltage and enhances conversion efficiency. Additionally, a differential input signal is connected to two ends of capacitors so as to reduce power conversion loss resulting from high switching frequency. The diodes D 1 -D 6 may be MOS (metal-oxide-semiconductor) diodes or equivalent diodes.

The invention includes two electronic switches S 1 and S 2 , six diodes D 1 -D 6 and four capacitors C 1 -C 4 . The two electronic switches S 1 and S 2 are solid state devices such as MOSFETs (metal-oxide-semiconductor field-effect transistors). The first electronic switch S 1 has a first control end (i.e., the gate of MOSFET) and two contact ends (i.e., the drain and source of MOSFET). The two first contact ends separately connect a ground end and a first end (RFin+) of an AC (alternating current) power source PS. The first control end connects a second end (RFin−) of the AC power source PS. The second electronic switch S 2 has a second control end (gate) and two contact ends (drain and source). The two second contact ends separately connect the ground end and the second end (RFin−) of the AC power source PS. The second control end connects the first end (RFin+) of the AC power source PS.

A positive end of a first diode D 1 is connected to the first end (RFin+) of the AC power source PS. A positive end of a second diode D 2 is connected to the second end (RFin−) of the AC power source PS. Two ends of a first capacitor C 1 are connected between the second end (RFin−) of the AC power source PS and a negative end of the first diode D 1 . Two ends of a second capacitor C 2 are connected between the first end (RFin+) of the AC power source PS and a negative end of the second diode D 2 . A positive end of a third diode D 3 is connected to the negative end of the first diode D 1 . In other words, the positive end of the third diode D 3 , the negative end of the first diode D 1 and an end of the first capacitor C 1 are connected to each other. A positive end of a fourth diode D 4 is connected to the negative end of the second diode D 2 . In other words, the positive end of the fourth diode D 4 , the negative end of the second diode D 2 and an end of the second capacitor C 2 are connected to each other.

Two ends of a third capacitor C 3 are connected between the second end (RFin−) of the AC power source PS and a negative end of the third diode D 3 . Two ends of a fourth capacitor C 4 are connected between the first end (RFin+) of the AC power source PS and a negative end of the fourth diode D 4 . A positive end of a fifth diode D 5 is connected to the negative end of the third diode D 3 . In other words, the positive end of the fifth diode D 5 , the negative end of the third diode D 3 and an end of the third capacitor C 3 are connected to each other. A positive end of a sixth diode D 6 is connected to the negative end of the fourth diode D 4 . And a negative end of the sixth diode D 6 is connected to a negative end of the fifth diode D 5 to form a voltage output end. In other words, the positive end of the sixth diode D 6 , the negative end of the fourth diode D 4 and an end of the fourth capacitor C 4 are connected to each other. A filter capacitor CL is connected between the voltage output end and the ground end.

In sum, the two first contact ends of the first electronic switch S 1 , the first diode D 1 , the third diode D 3 and the fifth diode D 5 are connected in series to form a path, and the two second contact ends of the second electronic switch S 2 , the second diode D 2 , the fourth diode D 4 and the sixth diode D 6 are connected in series to form another path. These two paths are parallel and symmetrical.

Please refer to FIG. 2 . When the AC power source PS is in a positive half cycle, the first diode D 1 and the second electronic switch S 2 in the master-stage circuit and the sixth diode D 6 in the slave-stage circuit will become conductive first, and voltages of the first capacitor C 1 and the filter capacitor CL are: VC 1 =2A−Vd and Vout=A−Vd, respectively, where A stands for input voltage amplitude, and Vd stands for conduction voltage of diode. When the voltage of the first capacitor C 1 reaches VC 1 =2A−Vd, the third diode D 3 will become conductive. At this time, the voltage at node N is (3A−2Vd) and the output voltage Vout=2A−2Vd.

Please refer to FIG. 3 . When the AC power source PS is in a negative half cycle, the second diode D 2 and the first electronic switch S 1 in the master-stage circuit will become conductive first, and a voltage of the second capacitor C 2 is: VC 2 =2A−Vd. When the voltage of the second capacitor C 2 reaches VC 2 =2A−Vd, the fourth diode D 4 will become conductive. At this time, the voltages at nodes H and N are (3A−2Vd) and (4A−2Vd), respectively, and the output voltage reaches Vout=2A−Vd, and will hold at (2A−Vd). This can obtain an effect of voltage doubling.

Additionally, the slave-stage auxiliary charge circuit may be extended with one or more stages to accomplish a higher voltage.

FIG. 4 shows another embodiment of the invention, which replaces the electronic switches with diodes DA and DB. This can also accomplish the equivalent circuits as shown in FIGS. 2 and 3 .

It will be appreciated by persons skilled in the art that the above embodiment has been described by way of example only and not in any limitative sense, and that various alterations and modifications are possible without departure from the scope of the invention as defined by the appended claims.