Telephone line power utility circuit

• US 5,461,671 A
• Filed: 06/01/1993
• Issued: 10/24/1995
• Est. Priority Date: 06/05/1992
• Status: Expired due to Term

• Current Assignee: Murata Manufacturing Co Limited
• Original Assignee: Murata Manufacturing Co Limited
• Inventors: Kuroda, Takashi, Sakuragi, Satosi
• Primary Examiner(s): Hofsass, Jeffery A.
• Assistant Examiner(s): WEAVER, SCOTT LOUIS
• Application Number:
  US08/070,606
• Time in Patent Office: 875 Days
• Field of Search: 379/413, 379/412, 379/387, 379/394, 379/398, 379/400, 379/403, 379/404, 379/412, 379/413, 379/415, 363/21, 363/89, 323/266, 323/277, 323/279, 323/258, 323/343, 329/387
• US Class Current: 379/400
• CPC Class Codes: H04M 19/08 with current supply sources at the substations generating ringing current H04M19/04
• CPC Class Codes: Y02D 30/70 in wireless communication networks

Abstract

A telephone line power utility circuit, in which direct-current power supplied through a telephone line-side is utilized as a power source for a line terminal device having a direct-current resistance, the telephone line power utility circuit including a DC-DC converter connected with the line terminal device for supplying the direct-current power to the line terminal device, the DC-DC converter having an input direct-current resistance; and a central processing unit (CPU), connected with the DC-DC converter, for obtaining a maximum input direct-current resistance of the DC-DC converter to increase the efficiency of receiving power of the DC-DC converter by allowing the direct-current resistance of the line terminal device, viewed from the telephone line-side, to satisfy a predetermined standard, controlling the duty ratio of the primary side switching element, and/or switching the taps of the primary side winding of the transformer of the DC-DC converter, such that the direct-current power supplied through the telephone line can effectively be used as a power source for the line terminal device.

Claims

1. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

DC-DC converter means, connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter means having an input direct-current resistance circuit;

input direct-current resistance control means, connected to said DC-DC converter means, for controlling an input direct-current resistance of said input direct-current resistance circuit of said DC-DC converter means so as to obtain highest efficiency of receiving power of the DC-DC converter means within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range for said telephone line, said input direct-current resistance control means including means for;

sensing a line current and rectified input voltage of said telephone line;

calculating a resistance using said rectified input voltage and said line current;

comparing said resistance with a reference value which is a highest resistance value permitted by said predetermined range; and

changing said input direct-current resistance so as to maintain said resistance close to said highest resistance value.

4. A telephone line power utility circuit according to claim 1,

further including:

a diode bridge having an input connected to the telephone line, and further having an output and a resistance RD, and

a hook switch having an input connected to the output of the diode bridge, and further having an output and a resistance RH; and

wherein said direct-current resistance of said telephone line power utility circuit, as viewed from the telephone-line side, is composed of a sum of said resistance RD, said resistance RH and said input direct-current resistance of the DC-DC converter means.

5. A telephone line power utility circuit according to claim 1, wherein said input direct-current resistance circuit includes a switching element having a control input, and said input direct-current resistance control means includes a central processing unit connected to said control input of said switching element of said DC-DC converter means which drives said switching element.

6. A telephone line power utility circuit according to claim 5, wherein said input direct-current resistance circuit includes a transformer connected to said switching element, and said switching element includes a transistor having a base as said control input and a current path through the collector and emitter of the transistor, said current path being connected to a primary winding of said transformer and said base being connected to said central processing unit to change said input direct-current resistance of said DC-DC converter means.

2. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

DC-DC converter means, connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter means having a transformer with a primary side winding and a switching element with a duty ratio connected to said winding;

duty ratio control means for controlling the duty ratio of said switching element of said DC-DC converter means so as to obtain highest efficiency of receiving power of the DC-DC converter means within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range for said telephone line, said duty ratio control means including means for;

sensing a line current and rectified input voltage of said telephone line;

calculating a resistance using said rectified input voltage and said line current;

comparing said resistance with a reference value which is a highest resistance value permitted by said predetermined range; and

changing said duty ratio of said switching element so as to maintain said resistance close to said highest resistance value.

7. A telephone line power utility circuit according to claim 2,

further including:

a diode bridge having an input connected to the telephone line, and further having an output and a resistance RD, and

a hook switch having an input connected to the output of the diode bridge, and further having an output and a resistance RH; and

wherein said direct-current resistance of said telephone line power utility circuit, as viewed from the telephone-line side, is composed of a sum of said resistance RD, said resistance RH and said input direct-current resistance of the DC-DC converter means.

8. A telephone line power utility circuit according to claim 2, wherein said switching element has a control input, and said duty ratio control means includes a central processing unit connected to said control input of said switching element of said DC-DC converter means which drives said switching element on the basis of said duty ratio.

9. A telephone line power utility circuit according to claim 8, wherein said switching element includes a transistor having a base as said control input and a current path through collector and emitter of the transistor, said current path being connected to a primary winding of said transformer and said base being connected to said central processing unit to change said input direct-current resistance of said DC-DC converter means.

3. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

DC-DC converter means, connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter means having a transformer with a primary side winding, said primary side winding having turns, and taps for increasing or decreasing the number of turns of said primary side winding;

tap changer means for switching said taps of said primary side winding of said transformer of said DC-DC converter means so as to obtain highest efficiency of receiving power of the DC-DC converter means within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range for said telephone line, said tap changer means including means for;

sensing a line current and rectified input voltage of said telephone line;

calculating a resistance using said rectified input voltage and said line current;

comparing said resistance with a reference value which is a highest resistance value permitted by said predetermined range; and

changing the taps of said primary side winding so as to maintain said resistance as close as possible to said highest resistance value.

10. A telephone line power utility circuit according to claim 3,

further including:

a diode bridge having an input connected to the telephone line, and further having an output and a resistance RD, and

a hook switch having an input connected to the output of the diode bridge, and further having an output and a resistance RH; and

wherein said direct-current resistance of said telephone line power utility circuit, as viewed from the telephone-line side, is composed of a sum of said resistance RD, said resistance RH and said input direct-current resistance of the DC-DC converter means.

11. A telephone line power utility circuit according to claim 3, wherein said DC-DC converter means includes a plurality of switching elements connected to different ones of said taps of said primary side winding, respectively, and said tap changer means includes a central processing unit connected to said switching elements of said DC-DC converter means to switch the taps of the primary side winding.

12. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

a DC-DC converter, connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter having an input direct-current resistance circuit;

input direct-current resistance control means, connected to said DC-DC converter, for controlling an input direct-current resistance of said input direct-current resistance circuit of said DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range for the telephone line;

a diode bridge having an input connected to a telephone line, and further having an output, and

a hook switch having an input connected to the output of said diode bridge, a resistance HS;

a low pass filter connected to an input of said DC-DC converter;

a separation transistor having a current path connected between said hook switch and said low pass filter, and said separation transistor further having a control input connected to said input direct-current resistance control means;

a bias shunt resistance circuit connected between said control input of said separation transistor and said input direct-current resistance control means; and

said input direct-current resistance control means including means for;

changing said input direct-current resistance of said DC-DC convertor so as to maintain said direct-current resistance of the telephone line power utility circuit close to a reference value which is a highest resistance value permitted by the predetermined range, and

changing a bias shunt resistance value of said bias shunt resistance circuit so as to control power loss in said separation transistor.

13. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

a transistor circuit which includes a separation transistor having a control input and a current path and a bias circuit which supplies a bias current to said control input of the separation transistor;

a DC-DC converter connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter having a switching transistor with a control input; and

input direct-current control means including a central processing unit, connected to said control input of the switching transistor and the transistor circuit, for controlling said switching transistor of said DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range and for changing said bias current of the separation transistor so as to control power loss in said separation transistor.

14. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

DC-DC converter connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter having a transformer with a primary side winding and a switching element with a duty ratio connected to said winding;

duty ratio control means for controlling the duty ratio of said switching element of said DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range;

a diode bridge having an input connected to a telephone line, and further having an output,

a hook switch having an input connected to the output of said diode bridge,

a low pass filter connected to an input of said DC-DC converter,

a separation transistor having a current path connected between said hook switch and said low pass filter, and said separation transistor further having a control input connected to said duty ratio control means;

a bias shunt resistance circuit connected between said control input of said separation transistor and said duty ratio control means; and

said duty ratio control means including means for;

changing the duty ratio of said switching element of said DC-DC convertor so as to maintain said direct-current resistance of the telephone line power utility circuit close to a reference value which is a highest resistance value permitted by the predetermined range, and

changing a bias shunt resistance value of said bias shunt resistance circuit so as to control power loss in said separation transistor.

15. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

a transistor circuit which includes a separation transistor having a control input and a current path and a bias circuit which supplies a bias current to said control input of the separation transistor;

a DC-DC converter connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter having a primary side switching element with a duty ratio, said switching element including a switching transistor with a control input; and

duty ratio control means including a central processing unit, connected to said control input of the switching transistor and the transistor circuit, for controlling the duty ratio of said primary side switching element of said DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range and for changing said bias current of the separation transistor so as to control power loss in said separation transistor.

16. A telephone line power utility circuit, in which direct-current power supplied through a telephone line is utilized as a power source for a line terminal device, comprising:

DC-DC converter connected to said line terminal device, for supplying said direct-current power to said line terminal device, said DC-DC converter having a transformer with a primary side winding, said primary side winding having turns, and taps for increasing or decreasing the number of turns of said primary side winding;

tap changer means for switching the taps of the primary side winding of said transformer of the DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range and to cause the direct-current resistance of the telephone line power utility circuit, viewed from the telephone line-side, to be within a predetermined range;

a diode bridge having an input connected to a telephone line, and further having an output,

a hook switch having an input connected to the output of said diode bridge, and further having an output;

a low pass filter connected to an input of said DC-DC converter, and

a separation transistor having a current path connected between said hook switch and said low pass filter and a control input connected to said tap changer means.

17. A power supply for use in a line terminal device, the power supply including a DC-DC converter means having a transformer with a primary winding and a switching element with a duty ratio connected to the primary said winding, comprising:

a transistor circuit associated with the DC-DC converter which includes a separation transistor having a control input and a current path and a bias circuit for supplying a bias current to said control input of the separation transistor;

bias means for controlling a bias current of said separation transistor so as to control power loss in said separation transistor; and

duty ratio control means, connected to said switching element, for controlling the duty ratio of the switching element of said DC-DC converter so as to obtain highest efficiency of receiving power of the DC-DC converter within a predetermined range.

18. A power supply according to claim 17, wherein said bias means include means for obtaining a voltage across said current path of the separation transistor to compare the first said voltage with a predetermined reference voltage and changing the first said voltage transistor so as to maintain the first said voltage to said predetermined reference voltage.

19. A power supply according to claim 17, wherein said bias circuit includes a bias shunt resistance connected between said control input of said separation transistor and said bias means, said bias means including means for changing a bias shunt resistance value of said bias shunt resistance.

20. A power supply according to claim 17,

further including a central processing unit,

said bias means includes means for:

obtaining a voltage across said current path of the separation transistor;

comparing the first said voltage with a predetermined reference voltage; and

changing the first said voltage so as to maintain the first said voltage to said predetermined reference voltage;

said duty ratio control means includes means for;

sensing an input current of an input of said DC-DC converter and an input voltage of said transistor circuit;

calculating a resistance using the input voltage and the input current;

comparing the resistance with a reference value which is a highest resistance value permitted by said predetermined range; and

changing said duty ratio of said switching element so as to maintain said resistance close to said highest resistance value.