Stable control system with positive feedback characteristic
First Claim
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1. A stable control circuit, comprising:
- an input;
an output;
a negative feedback loop connecting the input and output and having a first time constant; and
a positive feedback loop connecting the input and output and having a second time constant, the second time constant being longer than the first time constant.
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Abstract
A control system and circuit has a positive feedback characteristic but is nonetheless stable. Stability is achieved by superimposing a negative feedback loop with a short time constant and a positive feedback loop with a long time constant. The system and circuit are useful in situations where the sensor and the controlled variable (e.g. a heater) are well-coupled.
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Citations
6 Claims
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1. A stable control circuit, comprising:
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an input; an output; a negative feedback loop connecting the input and output and having a first time constant; and a positive feedback loop connecting the input and output and having a second time constant, the second time constant being longer than the first time constant.
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2. A control system for regulating a load in accordance with the electrical characteristics of a sensor which is well-coupled to the load, comprising:
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an input to which a sensor is connected; an output to which a load is connected; a negative feedback loop connecting the input and output and having a first time constant; and a positive feedback loop connecting the input and output and having a second time constant, the second time constant being longer than the first time constant.
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3. An improvement to a negative feedback control system which regulates a load in accordance with the electrical characteristics of a sensor using a negative feedback loop with a fixed time constant, the improvement compensating the system for coupling between the sensor and load and comprising a positive feedback loop having a time constant which is longer than the time constant of the negative feedback loop.
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4. A proportional control circuit comprising:
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a temperature-sensing network having an output voltage which varies with temperature; an operational amplifier having an output and inverting and non-inverting inputs, said network being connected between said inverting and non-inverting inputs; an electrical heater connected between said output and ground; and a positive feedback loop connecting said output and said non-inverting input. - View Dependent Claims (5, 6)
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Specification