Battery wake-up
First Claim
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1. A method to fast detect a low voltage in the range of few μ
- Volts, comprising the following steps;
(1) providing a circuit comprising input ports for a voltage to be measured, an output port, a pre-amplifier, a second amplifier, a buffer amplifier, an arrangement of switches used for calibration of the circuit, an integrator stage with reset function, and a voltage source for calibrating the integrator stage;
(2) connecting an output of the pre-amplifier to an input of the second amplifier and an output of the second amplifier to an input of the buffer amplifier and an output of the buffer amplifier to an input of the integrator stage, wherein an output of the integrator stage is the output of the circuit,(3) calibrating the pre-amplifier before each measurement of the voltage is performed;
(4) start calibration of the integrator stage by providing a voltage stimulus from said voltage source to the integrator stage;
(5) storing the integrated output signal of the integrator stage generated from said calibration voltage measurement;
(6) setting said switches to perform the voltage measurement;
(7) storing the integrated output signal of the integrator stage generated from said voltage measurement; and
(8) generating an output signal of the circuit if a difference between the calibration signal and the measurement signal exceeds a defined level, wherein all errors of the circuit are eliminated by said differentially generated signal.
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Abstract
Circuits and methods for fast detection of a low voltage in the range of few μVolts have been achieved. In a preferred embodiment the low voltage represents a current via a shunt resistor and the circuit is used to generate a digital wake-up signal. In regard of the wake-up application the circuit invented is activated periodically and in case of a certain level of the voltage drop, e.g. 50 μV, at the shunt resistor. The time required for a measurement of the voltage drop is inclusive calibration and integration time far below 1 ms. It is obvious that the circuit invented can be used for any measurements of very small voltages.
21 Citations
19 Claims
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1. A method to fast detect a low voltage in the range of few μ
- Volts, comprising the following steps;
(1) providing a circuit comprising input ports for a voltage to be measured, an output port, a pre-amplifier, a second amplifier, a buffer amplifier, an arrangement of switches used for calibration of the circuit, an integrator stage with reset function, and a voltage source for calibrating the integrator stage; (2) connecting an output of the pre-amplifier to an input of the second amplifier and an output of the second amplifier to an input of the buffer amplifier and an output of the buffer amplifier to an input of the integrator stage, wherein an output of the integrator stage is the output of the circuit, (3) calibrating the pre-amplifier before each measurement of the voltage is performed; (4) start calibration of the integrator stage by providing a voltage stimulus from said voltage source to the integrator stage; (5) storing the integrated output signal of the integrator stage generated from said calibration voltage measurement; (6) setting said switches to perform the voltage measurement; (7) storing the integrated output signal of the integrator stage generated from said voltage measurement; and (8) generating an output signal of the circuit if a difference between the calibration signal and the measurement signal exceeds a defined level, wherein all errors of the circuit are eliminated by said differentially generated signal. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11)
- Volts, comprising the following steps;
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12. A circuit for fast detection of a low voltage in the range of few μ
- Volts, comprising;
a shunt resistor configured to convert an input current to a voltage drop; a pre-amplifier stage, wherein a first input is connected to a second terminal of a first switching means and a second input is connected to a second terminal of the shunt resistor; said first switching means, wherein a first terminal of the switching means is connected to a first terminal of the shunt resistor; a second switching means being connected between both inputs of the pre-amplifier, wherein a first terminal of the switching means is connected to a first terminal of the shunt resistor; a first capacitor, wherein a first terminal is connected to the output of the preamplifier and a second terminal is connected to a first input of a second amplifier of a second amplifying stage and to a first terminal of a third switching means; said second amplifying stage comprising; said second amplifier having two inputs and an output, wherein the output is connected to a first terminal of a fifth switching means; said fifth switching means, configured to be used for calibration of the integrator stage only, having a second terminal connected a first terminal of a second capacitor and to a first terminal of a sixth switching means; said sixth switching means configured to be used for calibration of the integrator stage only; said second capacitor connected between a second terminal of the fifth switching means and a first input of a buffer amplifier; and said third switching means, wherein a second terminal is connected to a positive terminal of a first voltage source; and said fourth switching means wherein a first terminal is connected to the first input of the buffer amplifier and a second terminal is connected to the positive terminal of the first voltage source; said first voltage source, having a positive and a negative terminal, wherein a negative terminal is connected to ground; said buffer amplifier, having two inputs and an output, wherein a second input is connected to the output, and the output is further connected to an input of an integrator stage; said integrator stage comprising; an input resistor connected between the output of the buffer amplifier and a first input of an operational amplifier; said operational amplifier having two inputs and an output, wherein a second input is connected to the positive terminal of the first voltage source and the output is connected to an input of a sample and hold stage, to a second terminal of a feedback capacitor and to a second terminal of a reset switching means; said feedback capacitor wherein a first terminal of the feedback capacitor is connected to the first input of the operational amplifier; and said reset switching means wherein a first terminal of the reset switching means is connected to the first input of the operational amplifier; and said sample and hold stage generating a digital output signal of the circuit;
wherein the circuit is configured for calibration of the pre-amplifier, the buffer amplifier and the integrator stage before each measurement. - View Dependent Claims (13, 14, 15, 16, 17, 18, 19)
- Volts, comprising;
Specification