US4090664A
Expired / Lapsed
US
⏱️ 0.0 years remaining
Tri-state electrical circuit
Assignee: Johnson and Starley Ltd
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Filing: 1976-05-10
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Granted: 1978-05-23
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Expires: 1996-05-10
Abstract
Abstract An electrical circuit having three states depending upon the magnitude of an electrical signal coupled, in operation, to an input thereof, the circuit having a first stable state when the said magnitude is less than a first, predetermined value, a second, stable state when the said magnitude is greater than a second, predetermined value higher than the first said predetermined value, and a third, unstable state when said magnitude is equal to or between said first and second predetermined values. In a development of the invention, the circuit is incorporated in a control apparatus for a ducted, warm-air, central-heating system in which the gas supply to a burner is supplied continuously when the temperature of a space to be heated is below a predetermined temperature, is cut-off when the temperature of the space is above another, higher predetermined temperature, and is switched on and off at a rate dependent upon the magnitude of the temperature when it is equal to or between the two values.
Inventors
- 👤 Patrick John Elderkin
Bibliographic Details
Application Number
—
Jurisdiction
US
Data Source
google_patents
Last Synchronized
2026-10-28 06:58
CPC Classifications
H; H03; H03K; H03K7/00; H03K7/08; F; F23; F23N; F23N5/00; F23N5/02; F23N5/14; F23N5/143; G; G05; G05B; G05B11/00; G05B11/01; G05B11/26; G05B11/28; G05D; G05D23/00; G05D23/19; G05D23/1906; G05D23/1912; G05D23/1913; G05D23/20; G05D23/24; H03K3/00; H03K3/02; H03K3/26; H03K3/28; H03K3/281; H03K3/282; H03K3/2826; H03K3/2828; H03K3/286; H03K3/2893
Claims Analysis
Total Claims: 34
Claim 1
Independent Claim
275 words
An electrical circuit having three states depending upon the magnitude of an input electrical signal coupled, in operation, to an input thereof, the circuit comprising an input for receiving the input signal and an output, and having a first stable state when the said magnitude of said input signal is less than a first, predetermined value, a second, stable state when the said magnitude is greater than a second, predetermined value higher than the first said predetermined value, and a third, unstable state when said magnitude is equal to or between said first and second predetermined values, said circuit including a semi-conductor device having an input electrode, means for coupling the input signal to said input electrode such that said device is arranged to conduct current continuously in one of its stable states, to be substantially non-conductive in the other of its stable states and to oscillate between a conductive state and a substantially non-conductive state in its third, unstable state, said circuit being so arranged that when it is in the third, unstable state the ratio of the time it is in the conductive state to the time it is in the substantially non-conductive state is dependent upon the magnitude of the input electrical signal, said circuit comprising two transistors of opposite conductivity type, a feedback network, means coupling the collector of the first transistor to the base of the second transistor and means coupling the collector of the second transistor to the base of the first transistor by way of said feedback network which is arranged to determine the period of oscillation of the circuit when it is in the third, unstable state.
Claim 2
Dependent Claim
275 words
An electrical circuit having three states depending upon the magnitude of an input electrical signal coupled, in operation, to an input thereof, the circuit comprising an input for receiving the input signal and an output, and having a first stable state when the said magnitude of said input signal is less than a first, predetermined value, a second, stable state when the said magnitude is greater than a second, predetermined value higher than the first said predetermined value, and a third, unstable state when said magnitude is equal to or between said first and second predetermined values, said circuit including a semi-conductor device having an input electrode, means for coupling the input signal to said input electrode such that said device is arranged to conduct current continuously in one of its stable states, to be substantially non-conductive in the other of its stable states and to oscillate between a conductive state and a substantially non-conductive state in its third, unstable state, said circuit being so arranged that when it is in the third, unstable state the ratio of the time it is in the conductive state to the time it is in the substantially non-conductive state is dependent upon the magnitude of the input electrical signal, said circuit comprising two transistors of opposite conductivity type, a feedback network, means coupling the collector of the first transistor to the base of the second transistor and means coupling the collector of the second transistor to the base of the first transistor by way of said feedback network which is arranged to determine the period of oscillation of the circuit when it is in the third, unstable state.
Claim 3
Dependent Claim
183 words
Control apparatus for controlling the amount of heat generated by a gas heater according to the temperature of an object or a space to be heated, the apparatus comprising a tri-state circuit according to claim 1, a gas control means having an output for controlling the supply of gas to a burner, and an input coupled to the output of said tri-state circuit, means for monitoring the said temperature and for providing an input signal to said input of said tri-state circuit of such magnitude that when the temperature is less than a first predetermined value said tri-state circuit causes said gas control means to supply gas continuously to the burner, when the temperature is more than a second predetermined value higher than the first said predetermined value, said circuit causes said gas control means to stop the supply of gas to said burner, and when the temperature is equal to or between the said two predetermined values, said circuit causes the gas control means to supply gas to said burner intermittently and at a rate dependent upon the magnitude of the temperature.
Claim 4
Dependent Claim
39 words
Control apparatus according to claim 2, in which the means for monitoring the temperature is a device, such as a thermistor, the resistance of which varies with temperature, or a thermocouple, the output voltage of which varies with temperature.
Claim 5
Dependent Claim
39 words
Control apparatus according to claim 2 arranged to control the amount of heat generated in a central-heating system in which said means for monitoring the temperature is arranged to monitor the ambient temperature of a space to be heated.
Claim 6
Dependent Claim
51 words
Control apparatus according to claim 4 in a warm-air central-heating system further comprising a heat exchanger, ducts for the conveyance of heated air and means for directing air to be heated over said heat exchanger and then through said ducts to be discharged into a space or spaces to be heated.
Claim 7
Dependent Claim
17 words
Control apparatus according to claim 5, in which the said means for directing air comprises a fan.
Claim 8
Dependent Claim
61 words
Control apparatus according to claim 6, comprising means for controlling the speed of said fan motor to control the volume of air passed over the heat exchanger and delivered to the space or spaces to be heated in dependence upon the temperature at a predetermined position in the system, thereby to maintain the temperature in the space, or spaces substantially constant.
Claim 9
Dependent Claim
110 words
Control apparatus according to claim 7 in which said means for controlling the speed of rotation of said fan motor in dependence upon the magnitude of a temperature at a predetermined position in the system comprises an analogue to digital converter having an input for receiving an analogue input signal dependent on the temperature and an output and a motor control means having an input coupled to said output of said converter and an output, said motor control means being arranged, in operation, periodically to decode the digital output of the converter and to provide an output signal to control the speed of rotation of said motor in dependence thereon.
Claim 10
Dependent Claim
39 words
Control apparatus according to claim 8, further comprising means for periodically resetting the output of said analogue to digital converter to a datum value and for inhibiting change in operation of said motor control means during a conversion period.
Claim 11
Dependent Claim
71 words
Control apparatus according to claim 8 in which the analogue to digital converter comprises an analogue to time interval converter arranged to generate an output signal having a time duration dependent upon the magnitude of the input signal, a counter and pulse generator means coupled to the output of said analogue to time interval converter for causing pulses to be counted by said counter for the duration of said output signal.
Claim 12
Dependent Claim
117 words
Control apparatus according to claim 10 in which said analogue to time interval converter comprises a ramp generator for generating a ramp output signal which varies at a substantially constant rate during a conversion period and means for comparing the magnitudes of the ramp output signal and the input signal, or a signal derived from the input signal, and for generating a comparison signal when the two compared signals balance out, and said means coupled to the output of said analogue to time interval converter is arranged to cause pulses to be counted during a time interval starting when said ramp signal is equal to a datum value and terminating with the generation of the comparison signal.
Claim 13
Dependent Claim
15 words
Control apparatus according to claim 11 in which said ramp generator is a staircase generator.
Claim 14
Dependent Claim
50 words
Control apparatus according to claim 12 in which said staircase generator comprises a resistor and capacitor connected in series to a source of a.c. potential whereby the potential across the capacitor increases in a stepwise fashion as it is charged by alternate half cycles of current from the a.c. source.
Claim 15
Dependent Claim
26 words
Control apparatus according to claim 13 in which means is provided for discharging said capacitor to a datum level at the start of each conversion period.
Claim 16
Dependent Claim
38 words
Control apparatus according to claim 11 in which said means for comparing is a bistable circuit arranged to be set to one state at the start of a conversion period and to be reset by the comparison signal.
Claim 17
Dependent Claim
44 words
Control apparatus according to claim 8 in which said motor control means comprises a plurality of latching circuits coupled to the outputs of said counter and arranged to vary the energisation to said electric motor according to the weighting of its associated counter stage.
Claim 18
Dependent Claim
49 words
Control apparatus according to claim 16, in which the counter is a four-stage binary counter in which the four outputs thereof are representative of counts 1, 2, 4 and 8 respectively and the associated latching circuits are arranged to vary the power supplied to said motor by corresponding amount.
Claim 19
Dependent Claim
65 words
Control apparatus according to claim 17 comprising four resistors having weightings R, 2R, 4R and 8R connected in series with the alternating current supply to said motor and in which said latching circuits are arranged to short circuit said resistors of weighting R, 2R, 4R and 8R when the counter has a count representative of 1, 2, 4 and 8 respectively, or any combination thereof.
Claim 20
Dependent Claim
34 words
Control apparatus according to claim 18 in which each said resistor has a normally-open relay contact connected across it, and the relay contacts are controlled by relay coils energised by the corresponding latching circuits.
Claim 21
Dependent Claim
39 words
Control apparatus according to claim 16 in which the motor control means further includes means responsive to the input signal for inhibiting operation of the motor when the magnitude of the input signal is less than a predetermined value.
Claim 22
Dependent Claim
44 words
Control apparatus according to claim 11 in which said motor control means comprises a plurality of latching circuits coupled to the outputs of said counter and arranged to vary the energisation to said electric motor according to the weighting of its associated counter stage.
Claim 23
Dependent Claim
58 words
A circuit according to claim 1 having an output for connection to a load, such as a relay, which is arranged, in operation, to be energised continuously and de-energised when the circuit is in one and the other of the first and second states respectively, and to be energised intermittently when the circuit is in the third state.
Claim 24
Dependent Claim
24 words
A circuit according to claim 1, wherein the circuit is so arranged that both transistors are not completely saturated when in the conductive state.
Claim 25
Dependent Claim
26 words
A circuit according to claim 1 comprising a load, such as a relay, coupled between the collector of the second transistor and its collector supply voltage.
Claim 26
Dependent Claim
20 words
A circuit according to claim 1 in which the input of the circuit is the base of the first transistor.
Claim 27
Dependent Claim
117 words
A circuit according to claim 25 comprising a first NPN transistor and a second PNP transistor and in which the input signal is a d.c. voltage and said means for coupling the input signal to the base of the first transistor comprises a resistor, the arrangement being such that both transistors will be "on" when the magnitude of the input voltage is greater than a first predetermined value and both transistors will be "off" when the magnitude is less than a second predetermined value lower than the first said value, and when the magnitude of the input voltage is equal to or between the first and second predetermined values the transistors are switched "on" and "off" continuously.
Claim 28
Dependent Claim
47 words
A circuit according to claim 1, in which the feedback network between the collector of the second transistor and the base of the first transistor comprises a capacitor and resistor in series having values which determine the period of oscillation in the third state of the circuit.
Claim 29
Dependent Claim
64 words
A circuit according to claim 27 in which the said values of the feedback resistor and capacitor are such that the mark-space ratio (ratio of the length of time the transistors are "on" to the length of time the transistors are "off") of the circuit in the third state is dependent upon the magnitude of the input voltage, increasing as the said magnitude increases.
Claim 30
Dependent Claim
70 words
A circuit according to claim 28 in which the feedback network comprises a further circuit, such as a second capacitance-resistance circuit in parallel with the first mentioned capacitance-resistance circuit, to supplement said first feedback circuit when the input voltage is equal to or between the first and second predetermined values to ensure that the circuit remains in its unstable state at the two extremes of the controlled state of oscillation.
Claim 31
Dependent Claim
47 words
A circuit according to claim 26 in which the feedback network between the collector of the second transistor and the base of the first transistor comprises a capacitor and resistor in series having values which determine the period of oscillation in the third state of the circuit.
Claim 32
Dependent Claim
64 words
A circuit according to claim 30 in which the said values of the feedback resistor and capacitor are such that the mark-space ratio (ratio of the length of time the transistors are "on" to the length of time the transistors are "off") of the circuit in the third state is dependent upon the magnitude of the input voltage, increasing as the said magnitude increases.
Claim 33
Dependent Claim
70 words
A circuit according to claim 31 in which the feedback network comprises a further circuit, such as a second capacitance-resistance circuit in parallel with the first mentioned capacitance-resistance circuit, to supplement said first feedback circuit when the input voltage is equal to or between the first and second predetermined values to ensure that the circuit remains in its unstable state at the two extremes of the controlled state of oscillation.
Claim 34
Dependent Claim
10 words
A central-heating system comprising control apparatus according to claim 8.
References Cited (Backward Citations)
USPTO Annuity & Maintenance Windows
| Annuity Stage | Window Opens | Payment Deadline | Surcharge Period Until | Estimated Fee | Status |
|---|---|---|---|---|---|
| 3.5 Years (Year 4) | 1981-05-22 | 1981-11-21 | 1982-05-23 | $2000.00 | Window Closed / Lapsed |
| 7.5 Years (Year 8) | 1985-05-22 | 1985-11-21 | 1986-05-23 | $3760.00 | Window Closed / Lapsed |
| 11.5 Years (Year 12) | 1989-05-22 | 1989-11-21 | 1990-05-23 | $7700.00 | Window Closed / Lapsed |