Rectifier and associated rectifying circuit

A rectifier, including: a first and a second input terminal, a first output terminal and at least one rectifying circuit. Each rectifying circuit including: a switching circuit including a transistor, and a driving circuit. The driving circuit is coupled to the switching circuit and controls a switching status of the switching circuit, and includes a totem-pole circuit and an input transistor. The totem-pole circuit includes an input terminal and an output terminal coupled to the transistor. The input transistor is coupled between the totem-pole circuit and the switching circuit. The at least one rectifying circuit includes a first and a second rectifying circuit. The transistors of the first rectifying circuit and the second rectifying circuit are coupled to the first output terminal. The input transistors of the first rectifying circuit and the second rectifying circuit are coupled to the first input terminal and the second input terminal, respectively.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a rectifier and an associated rectifying circuit.

2. Description of the Prior Art

A traditional bridge rectifier is typically implemented by four diodes. Refer toFIG. 1,FIG. 1is a diagram illustrating a bridge rectifier1implemented by diodes in the prior art. The bridge rectifier1comprises diodes D1-D4, input terminals IN1and IN2, and output terminals OUT1and OUT2. The traditional bridge rectifier typically has advantages suchlike the size of a transformer thereof is relatively small. However, regarding a bridge rectifier implemented by diodes, the peak inverse voltage of the diodes is required to reach a certain voltage level. Once the diodes corresponding to such high performance are utilized, the manufacturing cost is accordingly increased. Therefore, a novel rectifier architecture is desired to solve the aforementioned problem.

SUMMARY OF THE INVENTION

One of objectives of the present invention is to provide a rectifier and an associated rectifying circuit to solve the aforementioned problem.

According to an embodiment of the present invention, a rectifier is disclosed, comprising: a first input terminal, a second input terminal, a first output terminal and at least one rectifying circuit. Each of the at least one rectifying circuit comprises: a switching circuit and a driving circuit. The switching circuit comprises a transistor; the driving circuit is coupled to the switching circuit and configured to control a switching status of the switching circuit, and the driving circuit comprises a totem-pole circuit and an input transistor. The totem-pole circuit comprises an input terminal and an output terminal, and the output terminal is coupled to the transistor. The input transistor is coupled between the totem-pole circuit and the switching circuit. The at least one rectifying circuit comprises a first rectifying circuit and a second rectifying circuit, the transistors of the first rectifying circuit and the second rectifying circuit are coupled to the first output terminal, and the input transistors of the first rectifying circuit and the second rectifying circuit are coupled to the first input terminal and the second input terminal, respectively.

According to an embodiment of the present invention, a rectifying circuit is disclosed, comprising: a switching circuit and a driving circuit. The switching circuit comprises a transistor. The driving circuit is coupled to the switching circuit and configured to control a switching status of the switching circuit, and the driving circuit comprises a totem-pole circuit and an input transistor. The totem-pole circuit comprises an input terminal and an output terminal, and the output terminal is coupled to the transistor. The input transistor is coupled between the totem-pole circuit and the switching circuit.

DETAILED DESCRIPTION

FIG. 2is a diagram illustrating a bridge rectifier20according to an embodiment of the present invention. As shown inFIG. 2, the bridge rectifier20comprises rectifying circuits210,220,230, and240, input terminals IN1and IN2, output terminals OUT1and OUT2, wherein the input terminal IN1is a natural wire terminal while the input terminal IN2is a fire wire terminal. The input terminal IN1and IN2are coupled to an electromagnetic interference filter circuit (not shown inFIG. 2). Refer toFIG. 2in conjunction withFIG. 1, the rectifying circuits210-240proposed by the present invention can be interpreted as the diodes D1-D4shown inFIG. 1, and the rectifying circuits210-240are basically identical. Each of the rectifying circuits210-240comprises a switching circuit SW and a driving circuit DR, wherein the switching circuit SW is implemented by an N-type Metal Oxide Semiconductor Field Effect Transistor (MOSFET) T3(hereinafter the transistor T3), and the driving circuit DR comprises a totem-pole circuit composed by Bipolar Junction Transistors (BJTs) and an input transistor T4composed by an N-type MOSFET. The totem-pole circuit of the driving circuit DR is composed by an npn BJT T1(hereinafter the transistor T1) and a pnp BJT (hereinafter the transistor T2), and the totem-pole circuit further comprises an input terminal N1, an output terminal N2and terminals N3and N4. The input terminal N1is coupled to base terminals of the transistors T1and T2while the output terminal N2is coupled to emitter terminals of the transistors T1and T2and a gate terminal of the transistor T3. The terminal N3is coupled to a collector terminal of the transistor T1while the terminal N4is coupled to a collector terminal of the transistor T2. In addition, as shown inFIG. 2, the input transistor T4of the driving circuit DR is coupled between the totem-pole circuit and the switching circuit SW. More specifically, a base terminal of the transistor T4is coupled to the terminal N4, a collector terminal of the transistor T4is coupled to the terminal N1, and a emitter terminal of the transistor T4is coupled to a source terminal of the transistor T3. In addition, drain terminals of the transistors T3of the rectifying circuits210and220are coupled to the output terminal OUT1and source terminals of the transistor T3of the rectifying circuit230and240are coupled to the output terminal OUT2.

Refer toFIG. 2again, each of the rectifying circuit210and220comprises a bootstrap circuit, and the bootstrap circuit and a reference voltage Vcc are utilized to elevate the voltage level on the terminal N3to provide power to the totem-pole circuit and the input transistor T4. In this embodiment, the maximum of the reference voltage Vcc is 12 volts. The bootstrap circuit of the rectifying circuit210is composed by a diode D1and a capacitor C1. More specifically, an anode of the diode D1is coupled to a reference voltage Vcc while a cathode of the diode D1is coupled to the terminal N3, and a terminal of the capacitor C1is coupled to the terminal N3while the other terminal of the capacitor C1is coupled to a source terminal of the transistor T4and input terminal IN1. In addition, the bootstrap circuit of the rectifying circuit220is composed by a diode D2and a capacitor C2. More specifically, an anode of the diode D2is coupled to the reference voltage Vcc while a cathode of the diode D2is coupled to the terminal N3, and a terminal of the capacitor C2is coupled to the terminal N3while the other terminal of the capacitor C2is coupled to the source terminal of the transistor T4and input terminal IN2.

Each of the rectifying circuits210-240comprises resistors R1and R2. Regarding the rectifying circuit210, a terminal of the resistor R1is coupled to the terminal N1while the other terminal of the resistor R1is coupled to the terminal N3, and a terminal of the resistor R2is coupled to the terminal N4while the other terminal of the resistor R2is coupled to the terminal N3of the rectifying circuit220; Regarding the rectifying circuit220, a terminal of the resistor R1is coupled to the terminal N1while the other terminal of the resistor R1is coupled to the terminal N3, and a terminal of the resistor R2is coupled to the terminal N4while the other terminal of the resistor R2is coupled to the terminal N3of the rectifying circuit210; Regarding the rectifying circuit230, a terminal of the resistor R1is coupled to the terminal N1while the other terminal of the resistor R1is coupled to a drain terminal of the transistor T3of the rectifying circuit240, and a terminal of the resistor R2is coupled to the terminal N4while the other terminal of the resistor R2is coupled to the input terminal IN2; Regarding the rectifying circuit240, a terminal of the resistor R1is coupled to the terminal N1while the other terminal of the resistor R1is coupled to the input terminal IN2, and a terminal of the resistor R2is coupled to the terminal N4while the other terminal of the resistor R2is coupled to a drain terminal of the transistor T3of the rectifying circuit240.

The operation of the bridge rectifier20has three different statuses while will be described in the following paragraphs.

When an absolute value of a difference between the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1and the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2is smaller than the reference voltage Vcc, i.e. |V1−V2|<Vcc, the input transistor T4is activated, to allow a strong current to flow through the transistor T4via the totem-pole circuit. The voltage on the terminal N2is accordingly decreased, and the transistor T3is deactivated. Therefore, when an absolute value of a difference between the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1and the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2is smaller than the reference voltage Vcc, the rectifying circuits210-240are closed.

When an absolute value of a difference between the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1and the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2is greater than the reference voltage Vcc, i.e. V1−V2>Vcc, the difference of the input voltages is a negative half wave waveform (refer to the difference of the input voltage inFIG. 3). The input transistors T4of the rectifying circuits220and240are accordingly activated to make the voltages on the terminals N2of the rectifying circuits220and240decrease. The transistors T3of the rectifying circuit220and240are deactivated. Oppositely, the transistors T4of the rectifying circuits210and230are deactivated, and the current flows to the terminal N2from the terminal N3to make the transistors T3of the rectifying circuits210and230activate by being driven by the totem-pole circuit. Therefore, when an absolute value of a difference between the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1and the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2is greater than the reference voltage Vcc, the rectifying circuit210and the rectifying circuit which is positioned on the diagonal corner of the rectifying circuit210(i.e. the rectifying circuit230) are activated, and the rectifying circuit220and the rectifying circuit which is positioned on the diagonal corner of the rectifying circuit220(i.e. the rectifying circuit240) are deactivated.

When an absolute value of a difference between the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2and the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1is greater than the reference voltage Vcc, i.e. V2−V1>Vcc, the difference of the input voltages is a positive half wave waveform. The input transistors T4of the rectifying circuits210and230are activated to make the voltages on the terminals N2of the rectifying circuits210and230decrease. The transistors T3of the rectifying circuits210and230are deactivated. Oppositely, the transistors T4of the rectifying circuits220and240are deactivated, and the current flows to the terminal N2from the terminal N3to make the transistors T3of the rectifying circuit220and240activate by being driven by the totem-pole circuit. Therefore, when an absolute value of a difference between the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2and the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1is greater than the reference voltage Vcc, the rectifying circuit220and the rectifying circuit which is positioned on the diagonal corner of the rectifying circuit220(i.e. the rectifying circuit240) are activated, and the rectifying circuit210and the rectifying circuit which is positioned on the diagonal corner of the rectifying circuit210(i.e. the rectifying circuit230) are deactivated.

Normally, the difference of the voltage (labeled as “V1” inFIG. 2) on the input terminal IN1and the voltage (labeled as “V2” inFIG. 2) on the input terminal IN2forms a sin wave, and by the rectifying operation of the bridge rectifier20, the voltage on the output terminal OUT1or OUT2shows a full wave rectifying waveform. However, by the architecture proposed by the present invention, when |V1−V2|>Vcc, the transistors T3of the rectifying circuits210-240are temporarily deactivated to keep the output voltage above the 0 volt. Refer toFIG. 3which is a diagram illustrating a difference value of the input voltage and the output voltage according to an embodiment of the present invention, such as the shown waveform of the difference of the input voltages (V1−V2), when the waveform of V1−V2enters a range defined by +12 volts and −12 volts, the output voltage is kept at 10 volts approximately. When the waveform of V1−V2keeps decreasing, the bridge rectifier20enters in to a state that the rectifying circuits210and230are activated while the rectifying circuits220and240are deactivated, and the waveform of the output voltage shows a full wave rectifying waveform. Oppositely, when the waveform of V1−V2keeps increasing the bridge rectifier20enters in to a state that the rectifying circuits220and240are activated while the rectifying circuits210and230are deactivated, and the waveform of the output voltage also shows a full wave rectifying waveform.

It should be noted that, the bridge rectifier20proposed by the present invention can be an analogy of the traditional bridge rectifier implemented by diodes. The only difference is the diodes in the traditional bridge rectifier are replaced by transistors in the present invention, and BJTs are utilized to implement the driving circuit. However, those skilled in the art should readily understand that the full wave rectifier is not limited to be implemented by the bridge rectifier comprising 4 diodes. A full wave rectifier can also be implemented by 2 diodes. Therefore, by implementing a rectifier with two rectifying circuits (e.g. the rectifying circuit210and230) proposed by the present invention, the same rectifying effect can also be achieved. In other words, the present invention is not limited by to be implemented by 4 rectifying circuits, i.e. the rectifying circuits210-240.

Briefly summarized, by the architecture of the present invention, when the input terminals are suddenly short circuited, the output voltage can still be kept at a voltage value to prevent the circuits from being damaged due to the huge swing of the voltage. In addition, the present invention utilizes BJT to implement the driving circuit which lowers the manufacturing cost comparing to the art implementing the driving circuit by driver ICs.