Parasitic power supply system for supplying operating power to a control device

• US 20030090243A1
• Filed: 11/13/2001
• Published: 05/15/2003
• Est. Priority Date: 11/13/2001
• Status: Active Grant

• Current Assignee: Ademco Inc. (Resideo Technologies, Inc.)
• Original Assignee: Honeywell International Inc.
• Inventors: Atherton, Larry S.
• Granted Patent: US 6,657,418 B2
• Time in Patent Office: Days
• US Class Current: 323/239
• CPC Class Codes: H02J 7/007 Regulation of charging or discharging current or voltage
• CPC Class Codes: H02M 1/0006 Arrangements for supplying an adequate voltage to the control circuit of converters
• CPC Class Codes: H02M 5/293 using semiconductor devices only

Abstract

A system and method to parasitically take electrical power from a source of ac load power to provide a voltage source to directly power an associated control device is described. The system utilizes a controllable transconductance device to both selectively provide power to a controlled load and to develop a predetermined voltage to directly power the control device in a system where the ac load power is applied at one terminal and is passed through the transconductance device to be returned through the load. The system includes a means for establishing the predetermined voltage level to power the control device and for continuously monitoring that voltage level to maintain it as required, whether power is applied to the load or not. Alternative voltage regulators to provide isolated or non-isolated power to the control device irrespective of whether or not power is applied to the load are also described.

Claims

1. For use in controlling selective application of electrical load power to a load, a parasitic control system to provide power to a control device from the load power comprising:

first means for coupling to a source of electrical load power to be selectively applied to a load;

second means for parasitically diverting a predetermined amount of power from applied electrical load power whether or not said load power is applied to the load, said predetermined amount of power being insufficient to impair proper operation of a the load when power is applied to the load or to cause activation of the load when load power is not applied to the load;

third means coupled to said second means for providing control device power at a predetermined voltage level to a control device; and

fourth means for sensing said predetermined voltage level of said control device power provided by said third means and for activating said second means as necessary to maintain said predetermined voltage level.

2. A parasitic control system as in claim 1, wherein said third means further includes:

fifth means for regulating a predetermined dc voltage level to power a control device.

3. A parasitic control system as in claim 2, and further including:

sixth means for isolating and regulating a predetermined isolated dc voltage level to be provided to a control device.

4. A parasitic control system as in claim 1, and further including power activating means for activating application of applied electrical load power to a load in response to an activation signal provided by a control device powered by said predetermined control device power.

5. A parasitic control system as in claim 1, and further including limiting means for limiting the voltage drop across said second means.

6. For use in providing ac electrical power to a load, a parasitic power controller comprising:

a power input terminal to couple to a source of alternating load power;

a transconductance circuit having a first terminal coupled to said power input terminal, a second terminal, and at least one control terminal to receive control signals to switch said transconductance circuit off or on;

a power circuit to provide a predetermined voltage to power a control device;

a bias switching circuit coupled to said power input terminal, to said power circuit, and to said at least one control terminal to cause said transconductance circuit to be switched to a predetermined state and to cause said power circuit to maintain said predetermined voltage level; and

an output circuit coupled to said transconductance circuit and to said power circuit and having a voltage output terminal to provide a predetermined output voltage;

whereby said predetermined voltage level is maintained whether the load power is applied to a load or not.

7. A parasitic power controller as in claim 6, and further including

a power switching circuit having an activation circuit to couple to a control device, a power-in terminal coupled to said second terminal of said transconductance circuit, and a power-out terminal to couple to a load to selectively provide power to the load under control of the control device,

whereby said output voltage is supplied to the control device and said transconductance circuit passes electrical load power through said power switching circuit to the load when the control device provides an activating signal to said activation circuit.

8. A parasitic power controller as in claim 6, wherein said transconductance device includes:

first and second field-effect transistors, each having a source, a drain, and a gate, and each of said gates coupled to said at least one control terminal;

a first diode coupled across said source and said drain of said first field-effect transistor; and

a second diode coupled across said source and said drain of said second field-effect transistor.

9. A parasitic power controller as in claim 8, and further including a voltage drop limiting circuit coupled across said first terminal and said second terminal, including

a pair of oppositely coupled voltage breakdown circuits to limit voltage drop across said transconductance circuit.

10. A parasitic power controller as in claim 8, wherein said bias switching circuit includes:

a first line diode having a first terminal coupled to said power input terminal and a second terminal coupled to a first line;

a second line diode coupled to said second terminal and said first line;

a common line coupled to said drain of said first field-effect transistor and to said drain of said second field-effect transistor;

a third field-effect transistor having a source coupled to said first line through a first juncture, a drain coupled to said common line, and a gate coupled through a second juncture to said at least one control terminal of said transconductance circuit;

a transistor having a collector coupled to said first line and to said second juncture, an emitter coupled to said common line, and a base coupled to a third juncture;

a first capacitor coupled between said first line and said common line;

a breakdown diode having a terminal coupled to said first line and a second terminal coupled to said third juncture to provide a reference voltage; and

a second capacitor coupled between said third juncture and said common line.

11. A parasitic power controller as in claim 6, wherein said power switching circuit comprises:

a relay having a normally open contact coupled to said second terminal of said transconductance circuit, a normally closed terminal, a contact coupled to said power-out terminal, and said activation circuit; and

a capacitor coupled between said normally open contact and said contact coupled to said power-out terminal.

12. A parasitic power controller as in claim 6, and further including:

a voltage regulator having a first input terminal coupled to said common line, a second input terminal coupled to a common point, and an output terminal for providing predetermined non-isolated regulated dc voltage to a control sensor; and

a diode coupled between said common point and said second terminal of said transconductance circuit.

13. A parasitic power controller as in claim 6, and further including:

an oscillator having a first input coupled to said common line and a second input coupled to a common point, and having output terminals;

a transform having a primary winding coupled to said output terminals of said oscillator, and having a secondary winding;

a bridge circuit coupled across said secondary winding, and having first and second bridge output terminals; and

a voltage regulator coupled to said first and second bridge output terminals and having an output terminal for providing a predetermined isolated regulated dc voltage to a control sensor.

14. A parasitic power controller as in claim 6, and further including an isolating activation control circuit comprising:

an isolation field-effect transistor having a drain coupled to said activation circuit of said power switching circuit, a source coupled to said bias switching circuit, and a gate coupled to said second terminal of said transconductance circuit, said gate arranged to receive the activating signal from the control sensor.

15. In a system for controlling selective application of electrical load power to a load under control of a control system, the method of parasitically providing power for the control system comprising:

coupling to a source of electrical load power;

parasitically diverting a predetermined amount of electrical power from the electrical load power to form a power source to be utilized to power the control system;

sensing the level of said power source;

selectively maintaining said power source at a predetermined level;

developing a dc output voltage from said predetermined amount of electrical power;

providing said dc output voltage to the control system; and

selectively activating application of the electrical load power to the load in response to the sensed conditions developed by the control system.

16. The method of claim 15, and further including the step of:

regulating said dc output voltage prior to said step of providing said dc output voltage to the control system.

17. The method of claim 16, wherein said developing step includes:

isolating said step of developing said dc output voltage from said step of providing said dc output voltage to the control system.

18. The method of claim 15, wherein the step of parasitically diverting a predetermined amount of electrical power includes:

applying the electrical load power to a transconductance device and to a bias circuit that controls the transconductance device;

causing the bias circuit to control the transconductance device to conduct sufficient power in response to the applied electrical load power whether or not the electrical load power is applied to the load, to thereby allow said dc output voltage to be developed; and

passing the electrical load power through the transconductance device to the load when control system determines the load should have power applied.

19. The method of claim 18, and further including the step of:

regulating said dc output voltage to a predetermined voltage level prior to said step of providing said dc output voltage to the control system.

20. For use in selectively providing ac electrical power to a load, a control circuit comprising:

a power input terminal to couple to a source of ac electrical power;

a transconductance circuit having a first terminal coupled to said power input terminal, a second terminal, and at least one control terminal to receive control signals to control the level of current flow through said transconductance circuit;

a voltage drop limiting circuit coupled across said first terminal and said second terminal;

a bias switching circuit coupled to said power input terminal and said at least one control terminal, bias switching circuit including a control device power source;

a dc output circuit coupled to said transconductance circuit and to said bias switching circuit and having a dc voltage output terminal to provide a predetermined dc voltage determined by said control device power source;

a control device having a dc power terminal coupled to said dc voltage output terminal, a sensing device to determine when electrical power should be applied to a load, and a control output terminal to provide activation signals;

a power switching circuit having an activation circuit coupled to said control output terminal, said power switching circuit having a power-in terminal coupled to said second terminal of said transconductance circuit, and a power-out terminal to couple to a load to selectively provide power to the load under control of said activation signals;

whereby sufficient power is parasitically withdrawn as needed from the ac electrical power available to power the load to be converted to said predetermined dc output voltage necessary to provide the power needed to operate said control device.

21. A control circuit as in claim 20, wherein said control device includes:

a sensor device to sense a predetermined ambient condition to determine the need of activating the application of electrical power to a load.

22. A control circuit as in claim 20, wherein said dc output circuit includes:

a voltage regulator circuit to provide said predetermined dc output voltage at a predetermined regulated level to be applied to said dc voltage output terminal.

23. A control circuit as in claim 22, and further including:

an isolation circuit coupled intermediate said voltage regulator circuit and said power input terminal to isolate said sensor control device from the source of ac electrical power.

24. A control circuit as in claim 20, wherein said bias switching circuit includes:

a floating common conductor; and

said control device power source includes a first capacitor coupled between said power input terminal and said floating common conductor, wherein said first capacitor is kept charged to a predetermined level by operation of said transconductance circuit.

25. A control circuit as in claim 24, and further including:

a second capacitor coupled to said second terminal of said transconductance circuit and to said power-out terminal of said power switching circuit to provide coupling to said power-out terminal when said power switching circuit is deactivated.