Power supply for telephone exchange

Claim 2

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer for detecting the current in said primary or secondary winding, and for feeding back the detected current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input and a single output, said input being connected to said secondary winding; a second switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistors is subsequently turned on, wherein said driving signal generator circuit includes a binary counter; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 3

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer for detecting the current in said primary or secondary winding, and for feeding back the detected current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input and a single output, said input being connected to said secondary winding; a second switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on, wherein said second switching circuit has four transistors for forming a full bridge circuit; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistors is subsequently turned on; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 4

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer for detecting the current in said primary or secondary winding, and for feeding back the detected current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input and a single output, said input being connected to said secondary winding; a second switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on, wherein said second switching circuit has four transistors for forming a full bridge circuit; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistors is subsequently turned on; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 5

The power supply for a telephone exchange according to claim 1 or 2, wherein an inductive/capacitive (LC) filter is provided between the output of said second switching circuit and a load.

Claim 6

The power supply for a telephone exchange of claim 1 or 2 wherein said converter transformer includes a secondary auxiliary winding for providing electric power to said driving circuit, said drive signal generator circuit and said second switching circuit.

Claim 7

The power supply for the telephone exchange of claim 4 further including an auxiliary power supply, having a rectifying and smoothing circuit, connected to said secondary auxiliary winding, for providing electric power to said driving circuit, said drive signal generator circuit and said second switching circuit.

Claim 8

The power supply for a telephone exchange of claim 1 or 2 wherein said second driving signal generator circuit has means for generating said driving signal so as to eliminate the period during which said transistors, being connected in series, are simultaneously turned on.

Claim 9

The power supply for a telephone exchange of claim 1 or 2, where in the surplus power supplied from said second switching circuit to a load is returned to the secondary winding of said converter transformer.

Claim 12

The method of supplying power to a telephone exchange of claim 8, further including the step of filtering the output of said second switching circuit with an inductive/capacitive (LC) filter.

Claim 13

The method of supplying power to a telephone exchange of claim 8 further including the step of providing electric power to said driving circuit, said drive signal generator circuit and said second switching circuit from a second auxiliary winding connected to said converter transformer.

Claim 14

The method of supplying power to the telephone exchange of claim 10 wherein said step of providing electric power to said driving circuit, said drive signal generator circuit, and said second switching circuit includes a step of rectifying and smoothing said electric power in a rectifying and smoothing circuit.

Claim 15

The method of supplying power to a telephone exchange of claim 8 wherein said step of generating includes a step of generating said driving signals so as to eliminate the period during which said transistors, being connected in series, are simultaneously turned on.

Claim 16

The method of supplying power to a telephone exchange of claim 8 further including the step of returning surplus power supplied from said second switching circuit to a load to said secondary winding of said converter transformer.

Claim 17

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer, coupled to said converter transformer and said first switching circuit, for detecting the current in said primary or secondary winding, and for feeding back the current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input connected to said secondary winding, and a single output; a second low frequency switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistor is subsequently turned on, wherein said driving signal generator circuit includes a binary counter; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 18

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer, coupled to said converter transformer and said first switching circuit, for detecting the current in said primary or secondary winding, and for feeding back the current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input connected to said secondary winding, and a single output; a second low frequency switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistor is subsequently turned on, wherein said driving signal generator circuit includes a binary counter; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 21

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer, coupled to said converter transformer and said first switching circuit, for detecting the current in said primary or secondary winding, and for feeding back the current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input connected to said secondary winding, and a single output; a second low frequency switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on, wherein said second low frequency switching circuit has four transistors forming a full bridge circuit; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistors is subsequently turned on; and a driving circuit for driving each of said transistors in accordance with said driving signal.

Claim 22

A power supply for a telephone exchange, comprising: a first switching circuit for receiving and subjecting direct current to high frequency switching by means of a switching element; a converter transformer having a primary winding connected to said first switching circuit, and a secondary winding; a current transformer, coupled to said converter transformer and said first switching circuit, for detecting the current in said primary or secondary winding, and for feeding back the current to the first switching circuit to stabilize the output of said first switching circuit; a smoothing circuit having an input connected to said secondary winding, and a single output; a second low frequency switching circuit connected to the single output of said smoothing circuit and used for switching the output current of said smoothing circuit by means of a transistor bridge including a plurality of transistors for being alternately turned on, wherein said second low frequency switching circuit has four transistors forming a full bridge circuit; a direct-current bypassing diode connected between the input and output terminals of each of said transistors for returning reactive power to said secondary winding; a driving signal generator circuit for generating a driving signal for setting timing to prevent the period during which each of said transistors is turned on from overlapping the period during which another of each of said transistors is subsequently turned on; and a driving circuit for driving each of said transistors in accordance with said driving signal.