US4894520A
Expired / Lapsed
US
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Circuit for controlling power dissipated by an electrical resistance
Assignee: Westinghouse Electric Corp
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Filing: 1988-06-13
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Granted: 1990-01-16
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Expires: 2008-06-13
Abstract
Abstract A circuit for controlling the power dissipated by an electrical resistance coupled to a supply voltage which varies, includes a feedback circuit, coupled to the electrical resistance, for producing a feedback current corresponding to the current flowing through the heater. A correction circuit produces a correction current corresponding to variations in the supply voltage. An integrator receives the correction current and the feedback current and amplifies the error indicated by the correction current and the feedback current. A pulse width modulator receives the amplified error and controls the ON time of a switching device to control the flow of current through the electrical resistance. The flow of current through the electrical resistance is controlled to maintain the power dissipated by the resistance constant.
Inventors
- 👤 Steven A. Moran
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-11-01 16:43
CPC Classifications
G; G05; G05D; G05D23/00; G05D23/19; H; H02; H02M; H02M3/00; H02M3/02; H02M3/04; H02M3/10; H02M3/145; H02M3/155; H02M3/156
Claims Analysis
Total Claims: 24
Claim 1
Independent Claim
102 words
A circuit for controlling power dissipated by an electrical resistance coupled to a supply voltage, comprising: first means, electrically coupled to the electrical resistance, for providing a feedback current in dependence upon the current flowing through the electrical resistance without using a squaring circuit; second means for providing a correction current corresponding to variations in the supply voltage; and third means for receiving the correction current and the feedback current, for amplifying an error indicated by the correction current and the feedback current, and for controlling the current flowing through the electrical resistance to control the power dissipated by the electrical resistance.
Claim 2
Dependent Claim
102 words
A circuit for controlling power dissipated by an electrical resistance coupled to a supply voltage, comprising: first means, electrically coupled to the electrical resistance, for providing a feedback current in dependence upon the current flowing through the electrical resistance without using a squaring circuit; second means for providing a correction current corresponding to variations in the supply voltage; and third means for receiving the correction current and the feedback current, for amplifying an error indicated by the correction current and the feedback current, and for controlling the current flowing through the electrical resistance to control the power dissipated by the electrical resistance.
Claim 3
Dependent Claim
34 words
A circuit according to claim 1, wherein said second means comprises: means for providing a variable current which varies in accordance with variations in the supply voltage; and means for providing a reference current.
Claim 4
Dependent Claim
31 words
A circuit according to claim 2, wherein said means for providing a reference current comprises: a Zener diode; and a first resistor coupled to said Zener diode and to a node.
Claim 5
Dependent Claim
27 words
A circuit according to claim 3, wherein said means for providing a variable current comprises a second resistor coupled to the supply voltage and to the node.
Claim 6
Dependent Claim
39 words
A circuit according to claim 4, wherein said circuit is coupled to an RMS reference voltage, and wherein said means for providing a reference current further comprises a third resistor coupled to the RMS reference voltage and the node.
Claim 7
Dependent Claim
23 words
A circuit according to claim 5, wherein said first means comprises a fourth resistor coupled to the node and to the electrical resistance.
Claim 8
Dependent Claim
52 words
A circuit according to claim 6, wherein said third means comprises: an integrator coupled to the node; a pulse width modulator coupled to said integrator; and a switching device, coupled to said pulse width modulator and to the electrical resistance, for controlling the flow of the current flowing through the electrical resistance.
Claim 9
Dependent Claim
23 words
A circuit according to claim 4, wherein said first means comprises a third resistor coupled to the node and to the electrical resistance.
Claim 10
Dependent Claim
52 words
A circuit according to claim 8, wherein said third means comprises: an integrator coupled to the node; a pulse width modulator coupled to said integrator; and a switching device, coupled to said pulse width modulator and to the electrical resistance, for controlling the flow of the current flowing through the electrical resistance.
Claim 11
Dependent Claim
109 words
A circuit for controlling power dissipated by an electrical resistance heater coupled to a supply voltage, comprising: first means, electrically coupled to the electrical resistance heater, for providing a feedback current based on the current flowing through the electrical resistance heater without using a squaring circuit; second means for providing a correction current corresponding to variations in the supply voltage; and third means for receiving the correction current and the feedback current, for amplifying an error indicated by the correction current and the feedback current, and for controlling the flow of current flowing through the electrical resistance heater to maintain the power dissipated by the electrical resistance heater constant.
Claim 12
Dependent Claim
109 words
A circuit for controlling power dissipated by an electrical resistance heater coupled to a supply voltage, comprising: first means, electrically coupled to the electrical resistance heater, for providing a feedback current based on the current flowing through the electrical resistance heater without using a squaring circuit; second means for providing a correction current corresponding to variations in the supply voltage; and third means for receiving the correction current and the feedback current, for amplifying an error indicated by the correction current and the feedback current, and for controlling the flow of current flowing through the electrical resistance heater to maintain the power dissipated by the electrical resistance heater constant.
Claim 13
Dependent Claim
34 words
A circuit according to claim 10, wherein said second means comprises: means for providing a variable current which varies in accordance with variations in the supply voltage; and means for providing a reference current.
Claim 14
Dependent Claim
31 words
A circuit according to claim 11, wherein said means for providing a reference current comprises: a Zener diode; and a first resistor coupled to said Zener diode and to a node.
Claim 15
Dependent Claim
27 words
A circuit according to claim 12, wherein said means for providing a variable current comprises a second resistor coupled to the supply voltage and to the node.
Claim 16
Dependent Claim
39 words
A circuit according to claim 13, wherein said circuit is coupled to an RMS reference voltage, and wherein said means for providing a reference current further comprises a third resistance coupled to the RMS reference voltage and the node.
Claim 17
Dependent Claim
116 words
A heater coupled to a supply voltage which varies, comprising: an electrical resistance heater, coupled to the supply voltage, for dissipating power as heat; and means for controlling the average current flowing through the electrical heater to produce an average heater current in accordance with the following equation: ##EQU4## where I avg (V BUS ) is the average heater current at the variable supply voltage, where I avg (V nom ) is the average heater current at the nominal value of the variable supply voltage, where V nom equals the nominal value of the supply voltage, and where V BUS equals the value of the variable supply voltage, said controlling means not including a squaring circuit.
Claim 18
Dependent Claim
116 words
A heater coupled to a supply voltage which varies, comprising: an electrical resistance heater, coupled to the supply voltage, for dissipating power as heat; and means for controlling the average current flowing through the electrical heater to produce an average heater current in accordance with the following equation: ##EQU4## where I avg (V BUS ) is the average heater current at the variable supply voltage, where I avg (V nom ) is the average heater current at the nominal value of the variable supply voltage, where V nom equals the nominal value of the supply voltage, and where V BUS equals the value of the variable supply voltage, said controlling means not including a squaring circuit.
Claim 19
Dependent Claim
107 words
A heater according to claim 15, wherein said means for controlling the average current flowing through the electrical resistance heater comprises: first means, coupled to the electrical resistance heater, for providing a feedback current corresponding to the current flowing through the electrical resistance heater; second means for providing a correction current corresponding to variations in the supply voltage; and third means for receiving the correction current and the feedback current, for amplifying an error indicated by the correction current and the feedback current, and for controlling the flow of current flowing through the electrical resistance heater to maintain the power dissipated by the electrical resistance heater constant.
Claim 20
Dependent Claim
34 words
A heater according to claim 16, wherein said second means comprises: means for providing a variable current which varies in accordance with variations in the supply voltage; and means for providing a reference current.
Claim 21
Dependent Claim
31 words
A heater according to claim 17, wherein said means for providing a reference current comprises: a Zener diode; and a first resistor coupled to said Zener diode and to a node.
Claim 22
Dependent Claim
27 words
A circuit according to claim 18, wherein said means for providing a variable current comprises a second resistor coupled to the supply voltage and to the node.
Claim 23
Dependent Claim
39 words
A heater according to claim 19, wherein said circuit is coupled to an RMS reference voltage and wherein said means for providing a reference current further comprises a third resistor coupled to the RMS reference voltage and the node.
Claim 24
Dependent Claim
58 words
A heater according to claim 15, wherein said means for controlling the average current flowing through the electrical resistance heater comprises means for increasing the average current when the variable supply voltage falls below its nominal value V nom and for decreasing the average current when the variable supply voltage rises above its nominal value V nom .
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USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1993-01-15 | 1993-07-17 | 1994-01-16 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1997-01-15 | 1997-07-17 | 1998-01-16 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 2001-01-15 | 2001-07-17 | 2002-01-16 | $7700.00 | Window Closed / Lapsed |