Fast start-up circuit
First Claim
1. An electronic apparatus comprising:
- a source having an output for providing a voltage Vi;
a load connection for receiving a voltage Vo whose rise time depends upon a capacitance coupled to the load connection;
a sensor circuit coupled to the source output and the load connection, for detecting Vi and Vo and providing an output signal related to (Vi-Vo);
a charger circuit for receiving the output signal of the sensor circuit and in response thereto, charging the capacitance until Vo˜
Vi; and
a feedback circuit having a buffer and a latch, wherein the buffer and latch are coupled to the sensor circuit for temporarily deactivating the sensor circuit when Vo˜
Vi so that the sensor circuit does not respond to (Vi-Vo) until after Vi is turned OFF.
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Accused Products
Abstract
The rise time of a voltage Vo presented to a load, based on an input voltage Vi provided via an RC filter coupled to the load for removing higher frequency noise on Vo, is substantially reduced by providing a sensor circuit with differential inputs Vi, Vo. The sensor circuit drives a charger circuit coupled to a DC potential and the load so that rapid charging of C to Vo does not depend on R. As Vo approaches Vi, the sensor circuit deactivates the charger circuit to stop further charging and a latch coupled to the sensor circuit shuts off the sensor circuit to reduce power consumption while (Vo˜Vi)>0. A current mirror buffer is desirably included between the sensor output and the latch for level shifting.
50 Citations
20 Claims
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1. An electronic apparatus comprising:
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a source having an output for providing a voltage Vi; a load connection for receiving a voltage Vo whose rise time depends upon a capacitance coupled to the load connection; a sensor circuit coupled to the source output and the load connection, for detecting Vi and Vo and providing an output signal related to (Vi-Vo); a charger circuit for receiving the output signal of the sensor circuit and in response thereto, charging the capacitance until Vo˜
Vi; anda feedback circuit having a buffer and a latch, wherein the buffer and latch are coupled to the sensor circuit for temporarily deactivating the sensor circuit when Vo˜
Vi so that the sensor circuit does not respond to (Vi-Vo) until after Vi is turned OFF. - View Dependent Claims (2, 3, 4, 5)
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6. A fast rise time, low noise circuit for providing a voltage Vo to a load connection, comprising:
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a reference generator producing a voltage Vi on an output thereof; a filter coupled between the reference generator output and the load connection for removing higher frequency noise from Vo, wherein a capacitance C appears at the load connection; a sensor circuit having a first input terminal coupled to the reference generator output and a second input terminal coupled to the load connection, and an output; and a charger circuit actuated by the output of the sensor circuit for coupling the load connection to a first potential when Vo<
(Vi-Vos), and to a second potential when Vo>
(Vi+Vos'"'"'), where Vos and Vos'"'"' are off-set voltages smaller than Vi. - View Dependent Claims (7, 8, 9, 10)
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11. An apparatus for providing voltage Vo on a node thereof, comprising:
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a generator circuit for providing a reference voltage Vi; a filter having resistance R coupled between the generator circuit and the node and capacitance C coupled to the node, for removing higher frequency noise from Vo; a variable impedance coupled between a DC potential connection and the node; a differential amplifier having inputs, coupled to R, and an output, wherein the output controls the variable impedance so that rapid charging of C does not depend on R; and a feedback circuit for receiving an input signal from the output of the differential amplifier and having an output coupled to a control input of the differential amplifier for shutting off the variable impedance when Vo˜
Vi and then, after a delay, shutting off the differential amplifier to reduce further power consumption. - View Dependent Claims (12, 13)
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14. An apparatus for providing voltage Vo on a node thereof, comprising:
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a voltage reference circuit for providing voltage Vi; a low pass RC filter wherein resistance R is coupled between the voltage reference circuit and the node, and capacitance C is coupled to the node for removing higher frequency noise from Vo; a variable current source coupled between DC potentials and to the node having Vo, wherein the variable current source has a first portion for charging C when Vo<
Vi-Vos1, and a second portion for discharging C when Vo>
Vi+Vos2, where Vos1 and Vos2 are off-set voltages greater than zero; anda differential amplifier coupled to R and driving the variable current source so that rapid charging and discharging of C does not depend on R. - View Dependent Claims (15, 16, 17, 18, 19, 20)
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Specification