Electric power conversion systems – Current conversion – Using semiconductor-type converter
Reexamination Certificate
1998-02-05
2002-08-06
Han, Jessica (Department: 2838)
Electric power conversion systems
Current conversion
Using semiconductor-type converter
C363S089000
Reexamination Certificate
active
06430071
ABSTRACT:
DETAILED DESCRIPTION OF THE INVENTION
1. Technical Field
The present invention relates to an electric circuit for rectifying an alternating current, more particularly to an electric circuit for rectifying an alternating current with a small loss.
2. Background Art
A rectification circuit has been used as a circuit for converting an alternating voltage to a direct voltage.
The conventional rectification circuit is comprised of a silicon diode, a schottky-barrier diode, or the like.
In the conventional circuit, however, a forward voltage Vf of a diode is approximately 0.4V to 1.0V, as shown in
FIG. 3
showing a relationship between the voltage Vf and a current If. Therefore, the voltage drop, in other words, a loss in the diode of the rectification circuit, is large. As a result, inefficient rectification has been a problematical matter.
The present invention has been made in consideration of the above, and it is an object of the present invention to provide an electric circuit which can rectify an alternating current with a small loss.
DISCLOSURE OF INVENTION
To achieve the above described object, an electric circuit according to a first aspect of the present invention comprises a transistor and a control circuit connected to said transistor, and is characterized in that said transistor comprises a current path and a control terminal, receives a target voltage to be rectified at one end of said current path, and is controlled by said control circuit to be activated or inactivated to output a rectified voltage at the other end of said current path; and
said control circuit is connected to at least one end of said current path of said transistor and said control terminal, activates said transistor when a reverse voltage is applied to said current path, inactivates said transistor when a forward voltage is applied to said current path, and controls a signal to be applied to said control terminal for activating or inactivating said transistor to make said transistor rectify said target voltage.
According to the electric circuit of the first aspect of the present invention, the transistor is activated when the voltage applied to the current path of the transistor is a reverse voltage, and is inactivated when it is a forward voltage. Therefore, only a voltage having one polarity is applied to a load which is connected to the transistor. And, a forward voltage is applied to the current path when the transistor is inactivated, therefore, a high withstanding voltage can be obtained.
The electric circuit according to a second aspect of the present invention comprises a transistor and a control circuit connected to said transistor, and is characterized in that said transistor comprises a current path and a control terminal, receives a target voltage to be rectified at one end of said current path, and outputs a rectified voltage at the other end of said current path by being activated or inactivated in accordance with control of said control circuit; and
said control circuit is connected to both ends of said current path and said control terminal, detects the potential difference between the both ends of said current path, and controls a signal to be applied to said control terminal for activating or inactivating said transistor, so as to activate said transistor when a reverse voltage of said transistor is applied to said current path of said transistor and inactivate said transistor when a forward voltage of said transistor is applied to said current path, to make said transistor rectify said target voltage.
The electric circuit according to a third aspect comprises a transistor and a control circuit connected to said transistor, and is characterized in that said transistor comprises a current path and a control terminal, receives a target voltage to be rectified at one end of said current path, and outputs a rectified voltage to the other end of said current path by being activated or inactivated in accordance with control of said control circuit; and
said control circuit is connected to both ends of said current path and said control terminal, detects the potential difference between the both ends of said current path, and controls a signal to be applied to said control terminal for activating or inactivating said transistor so as to activate said transistor when a reverse voltage is applied to said current path of said transistor and inactivate said transistor when a forward voltage is applied to said current path to make said transistor rectify said target voltage.
According to the electric circuit of the second and third aspects of the present invention, the voltage which is applied between the both ends of the current path of the transistor or the polarity of the voltage is detected, and the transistor is activated when the voltage is in the reverse direction and the transistor is inactivated when the voltage is in the forward direction. Therefore, only voltage in one polarity is applied to a load which is connected to the other end side of the current path of the transistor. And, the forward voltage is applied to the current path when the transistor is inactivated, therefore, a high withstanding voltage can be obtained.
In thus structured electric circuit, there is a way to activate/inactivate the transistor based on values for the supplied target voltage to be rectified or its polarity. However, a reverse current flow is caused by this method because the source voltage becomes lower than the voltage at the load while the transistor is being activated, when a capacitor or a battery is used as the load retaining the voltage. By the present invention, the target voltage to be rectified can be rectified without such a problem because the voltage to be applied to the current path of the transistor is detected.
Said transistor is, for example, a bipolar transistor. In this case, both ends of said current path are the emitter and collector of said bipolar transistor, said control terminal is the base of said bipolar transistor, and said control circuit comprises means for detecting voltage and/or its polarity between said emitter and said collector, and for supplying a voltage and a current to said base.
If said bipolar transistor is an NPN type bipolar transistor:
one end of said current path is emitter of said NPN bipolar transistor, the other end of said current path is collector of said NPN bipolar transistor, and said control terminal is base of said NPN bipolar transistor; and
said control circuit supplies a voltage and a current for activating said NPN transistor to said base when potential in positive polarity, which is higher than that applied to said collector, is applied to said emitter, and supplies a voltage and a current for inactivating said NPN transistor to said base when voltage in positive polarity, which is lower than that applied to said collector, is applied to said emitter.
If said bipolar transistor is a PNP type bipolar transistor:
one end of said current path is emitter of said PNP bipolar transistor, the other end of said current path is collector of said PNP bipolar transistor, and said control terminal is base of said PNP bipolar transistor; and
said control circuit supplies a voltage and a current for activating said PNP transistor to said base when potential in positive polarity, which is higher than that applied to said emitter, is applied to said collector, and supplies a voltage and a current for inactivating said PNP transistor to said base when voltage in positive polarity, which is lower than that applied to said emitter, is applied to said collector.
Said bipolar transistor comprises the emitter and the collector both having substantially the same thickness of semiconductor layers. According to such a structure, the emitter and the collector are not distinguished substantially, and it can save current amplification factor largely during activation. Moreover, high withstanding voltage can be obtained.
Said transistor may be replaced with a field effect transistor.
In this case, both ends of said current path are source and drain of said field effe
Han Jessica
NTT Data Corporation
Rader & Fishman & Grauer, PLLC
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