Power and signal transmission system

A power and signal transmission system comprising:

• a first communication device including a transmitting circuit for outputting a transmission signal and first capacitive coupling means connected to said transmitting circuit for passing the transmission signal and blocking DC components;
• a pair of transmission lines connected to said first communication device, for transmitting the transmission signal which has passed through said first capacitive coupling means;
• a second Communication device including second capacitive coupling means connected to said transmission path for passing the transmission signal and blocking DC components and a receiving circuit for receiving the transmission signal which has passed through said second capacitive coupling means;
• power source means provided in said first communication device and having a pair of terminals connected to the transmission lines, respectively, for producing a DC power to be supplied to said transmission lines;
• converting means provided in said second communication device and connected to said transmission lines, for converting the power transmitted via said transmission lines into operating power to be supplied to said receiving circuit;
• and
• a pair of active inductances provided between the terminals of said power source means and said transmission lines, respectively, for supplying the DC power of said power source to the transmission lines and blocking the transmission signal, each of said active inductances including:
• a first terminal connected to a corresponding one of said transmission lines,
• a second terminal connected to said power source means and grounded,
• a power transistor having a collector and an emitter connected to said first and second terminals, respectively,
• a first level shift circuit connected to said first terminal, for level-shifting a voltage appearing on said first terminal,
• a first transistor having a base connected to said first level shift circuit,
• a second level shift circuit connected to said second terminal, for level-shifting a voltage appearing on said second terminal,
• a second transistor having a base connected to said second level shift circuit, for converting a voltage appearing between said first and second terminals to a current,
• a resistor connected between bases of said first and second transistors, a voltage appearing across said resistor being equal to the voltage between said first and second terminals,
• a constant current source connected to a collector of said second transistor, and
• an emitter follower connected between a base of said power transistor and the collector of said second transistor.

A power and signal transmission system comprising:

• a first communication device including a transmitting circuit for outputting a transmission signal and first capacitive coupling means connected to said transmitting circuit for passing the transmission signal and blocking DC components;
• a pair of transmission lines connected to said first communication device, for transmitting the transmission signal which has passed through said first capacitive coupling means;
• a second communication device including second capacitive coupling means connected to said transmission path for passing the transmission signal and blocking DC components and a receiving circuit for receiving the transmission signal transmitted via said transmission lines;
• power source means provided in said first communication device and having a pair of terminals connected to the transmission lines, respectively, for producing a DC power to be supplied to said transmission lines;
• converting means provided in said second communication device and connected to said transmission lines, for converting the DC power transmitted via said transmission lines into operating power to be supplied to said receiving circuit;
• and
• a pair of active inductances connected between two input terminals of said converting means and said transmission lines, respectively, for supplying the DC power via the transmission lines to said converting means and blocking the transmission signal, each of said active inductances including:
• a first terminal connected to said converting means,
• a second terminal connected to a corresponding one of said transmission lines,
• a power transistor having a collector and an emitter connected to said first and second terminals, respectively,
• a first level shift circuit for level-shifting a voltage appearing on said first terminal,
• a first transistor having a base connected to said first level shift circuit,
• a second level shift circuit for level-shifting a voltage appearing on said second terminal,
• a second transistor having a base connected to said second level shift circuit, for converting a voltage appearing between said first and second terminals to a current,
• a resistor connected between emitters of said first and second transistors, a voltage appearing across said resistor being equal to the voltage between said first and second terminals,
• a series circuit of an emitter follower and a diode circuit, which is connected between a collector of said second transistor and the base of said power transistor, and
• a current mirror circuit connected to said emitter follower, for supplying a load current thereto.

A power and signal transmission system comprising:

• a first communication device including a transmitting circuit having two output terminals for outputting a transmission signal, a first pair of DC blocking capacitors, each being connected between one of said output terminals of said transmitting circuit and one of two transmission lines, and a DC power source having two terminals for supplying a DC power to said transmission lines;
• a second communication device including a receiving circuit having two input terminals for receiving the transmission signal transmitted from said first communication device via the transmission lines, a second pair of DC blocking capacitors, each being connected between one of the transmission lines and one of the two input terminals of said receiving circuit, and converting means having two terminals for converting the DC power supplied via the transmission lines into operating power and supplying the operating power to said receiving circuit;
• a first pair of active inductances provided in said first communication device, and connected between the terminals of said DC power source and the transmission lines, for supplying the DC power from said DC power source to the transmission lines and blocking the transmission signal, each of said first active inductances including:
• a first terminal connected to a corresponding one of said transmission lines,
• a second terminal connected to said power source means.
• a first power transistor having a collector and an emitter connected to said first and second terminals, respectively,
• a first level shift circuit connected to said first terminal, for level-shifting a voltage appearing on said first terminal,
• a first transistor having a base connected to said first level shift circuit,
• a second level shift circuit connected to said second terminal, for level-shifting a voltage appearing on said second terminal,
• a second transistor having a base connected to said second level shift circuit, for converting a voltage appearing between said first and second terminals to a current,
• a resistor connected between emitters of said first and second transistors, a voltage appearing across said resistor being equal to the voltage between said first and second terminals,
• a constant current source connected to a collector of said second transistor, and
• a first emitter follower connected between a base of said first power transistor and the collector of said second transistor;
• and
• a second pair of active inductances provided in said second communication device, and connected between the terminals of said converting means and the transmission lines, for supplying the power supplied via the transmission lines to said converting means and blocking the transmission signal, each of Said second active inductances including:
• a third terminal connected to said converting means,
• a fourth terminal connected to a corresponding one of said transmission lines,
• a second power transistor having a collector and an emitter connected to said third and fourth terminals, respectively,
• a third level shift circuit for level-shifting a voltage appearing on said third terminal,
• a third transistor having a base connected to said third level shift circuit,
• a fourth level shift circuit for level-shifting a voltage appearing on said fourth terminal,
• a fourth transistor having a base connected to said fourth level shift circuit, for converting a voltage appearing between said third and fourth terminals to a current,
• a second resistor connected between emitters of said third and fourth transistors, a voltage appearing across said second resistor being equal to the voltage between said third and fourth terminals,
• a series circuit of a second emitter follower and a diode circuit, which is connected between a collector of said fourth transistor and the base of said second power transistor, and
• a current mirror circuit connected to said second emitter follower, for supplying a load current thereto.

A power and signal transmission system comprising:

• a first communication device including a transmitting circuit having two output terminals for outputting a transmission signal, a first pair of DC blocking capacitors, each being connected between one of said output terminals of said transmitting circuit and one of two transmission lines, and a DC power source having two terminals for supplying a DC power to said transmission lines;
• a second communication device including a receiving circuit having two input terminals for receiving the transmission signal transmitted from said first communication device via the transmission lines, a second pair of DC blocking capacitors, each being connected between one of the transmission lines and one of the two input terminals of said receiving circuit, and converting means having two terminals for converting the DC power supplied via the transmission lines into operating power and supplying the operating power to said receiving circuit;
• a first pair of active inductances provided in said first communication device, and connected between the terminals of said DC power source and the transmission lines, for supplying the DC power from said DC power source to the transmission lines and blocking the transmission signal;
• and
• a second pair of active inductances provided in said second communication device, and connected between the terminals of said
• a capacitor having one terminal connected to a node between the collector of one of said PNP and NPN transistors and said constant current source, and
• a third level shift circuit for level-shifting a voltage appearing on said node and applying a level shifted voltage to the base of said power transistor,
• wherein an amount of level shift otained by said first level shift circuit and said NPN transistor is equal to that obtained by said second level shift circuit and said PNP transistor, and said second pair of active inductances each extract a load current of an emitter follower for driving the base of said power transistor from a constant current source using a current mirror circuit.
• a capacitor having one terminal connected to a node between the collector of one of said PNP and NPN transistors and said constant current source, and
• a third level shift circuit for level-shifting a voltage appearing on said node and applying a level shifted voltage to the base of said power transistor,
• wherein an amount of level shift obtained by said first level shift circuit and said NPN transistor is equal to that obtained by said second level shift circuit and said PNP transistor, and said second pair of active inductances each extract a load current of an emitter follower for driving the base of said power transistor from a constant current source using a current mirror circuit.