Soft-start reference ramp and filter circuit
First Claim
1. A circuit for providing controlled ramping and filtering, comprising:
- a voltage regulator controller, including;
a current mirror circuit that is arranged to receive a reference voltage and to provide a charging current from a biasing current, wherein the current mirror circuit includes a first and a second transistor having sources receiving said reference voltage;
a soft-start capacitor circuit that is arranged to provide a conditioned reference voltage based, in part, on the charging current, wherein the soft-start capacitor circuit is coupled to the second transistor, and wherein the soft-start capacitor circuit is arranged such that the conditioned reference voltage is substantially stable during a steady state and such that the conditioned reference voltage substantially tracks the reference voltage during the steady state;
a switch circuit comprising a transistor, wherein the switch circuit is arranged to receive a switch control signal, and wherein the switch circuit is arranged to shunt the charging current away from the soft-start capacitor circuit, if the switch control signal corresponds to an inactive level, and further arranged to enable the soft-start capacitor circuit to be charged, if the switch control signal corresponds to an active level; and
a differential amplifier that is arranged to receive a feedback voltage that is based at least, in part, on a regulated output voltage;
to receive the conditioned reference voltage;
and to, during all operating states, compare the conditioned reference voltage with the feedback voltage.
2 Assignments
0 Petitions
Accused Products
Abstract
A method and circuit for providing a controlled ramping and filtering to a reference voltage in a regulator circuit such that an inrush current is limited and noise coupling to an output voltage is reduced. In a typical regulator circuit a soft-start and filter circuit is inserted between a feedback amplifier and a charge transfer circuit. The soft-start and filter circuit comprises a pair of transistors that are arranged to operate as a current mirror, a biasing current source determining the current drawn from the current mirror, and a soft-start capacitor shunted by a third transistor providing a conditioned reference voltage. When reference voltage rises rapidly during power-up, charging of the soft-start capacitor with constant current provides a soft-sloped conditioned reference voltage. In steady state, soft-start capacitor and a resistance of the transistor provide a first order low pass filter reducing noise that couples to the reference voltage.
-
Citations
20 Claims
-
1. A circuit for providing controlled ramping and filtering, comprising:
-
a voltage regulator controller, including; a current mirror circuit that is arranged to receive a reference voltage and to provide a charging current from a biasing current, wherein the current mirror circuit includes a first and a second transistor having sources receiving said reference voltage; a soft-start capacitor circuit that is arranged to provide a conditioned reference voltage based, in part, on the charging current, wherein the soft-start capacitor circuit is coupled to the second transistor, and wherein the soft-start capacitor circuit is arranged such that the conditioned reference voltage is substantially stable during a steady state and such that the conditioned reference voltage substantially tracks the reference voltage during the steady state; a switch circuit comprising a transistor, wherein the switch circuit is arranged to receive a switch control signal, and wherein the switch circuit is arranged to shunt the charging current away from the soft-start capacitor circuit, if the switch control signal corresponds to an inactive level, and further arranged to enable the soft-start capacitor circuit to be charged, if the switch control signal corresponds to an active level; and a differential amplifier that is arranged to receive a feedback voltage that is based at least, in part, on a regulated output voltage;
to receive the conditioned reference voltage;and to, during all operating states, compare the conditioned reference voltage with the feedback voltage. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17)
-
-
18. A circuit for soft-started ramping and filtering, comprising:
a means for providing a regulated input voltage at an output, including; a current mirror that is arranged to receive a reference voltage at sources of first and second transistors of a current mirror and to provide a charging current; a means for providing a conditioned reference voltage based, in part, on the charging current such that a rise time of the conditioned reference voltage is substantially greater than a rise time of the reference voltage, and such that a noise component of the reference voltage is filtered, such that the conditioned reference voltage is substantially stable during a steady state, and such that the conditioned reference voltage substantially tracks the reference voltage during the steady state; a means for providing the reference voltage to the means for providing a conditioned reference voltage; a means for providing the charging current to the means for providing a conditioned reference voltage, if a switch control signal changes to an active level, said charging current independent of the regulated input voltage at said output; a means for filtering a noise component of the reference voltage in a steady state when the means for providing a conditioned reference voltage is charged; and a means for comparing, during all operating states, the conditioned reference voltage with a feedback voltage, wherein the feedback voltage is based at least, in part, on the regulated input voltage at said output.
-
19. A method for providing controlled ramping and filtering, comprising:
regulating an output voltage, wherein regulating the output voltage includes; receiving a reference voltage at sources of a first and second transistor of a current mirror; providing a charging current from the current mirror; if a switch control signal corresponds to an active level, charging a soft-start capacitor circuit with the charging current; and if the switch control signal corresponds to an inactive level, shunting the charging current away from the soft-start capacitor circuit; providing a conditioned reference voltage, such that a rise time of the conditioned reference voltage is greater than a rise time of the reference voltage, such that a noise component of the reference voltage is less than a noise component of the conditioned reference voltage, such that the conditioned reference voltage is substantially stable during a steady state, and such that the conditioned reference voltage substantially tracks the reference voltage during the steady state; and comparing, during all operating states, the conditioned reference voltage with a feedback voltage, wherein the feedback voltage is based at least, in part, on a regulated output voltage. - View Dependent Claims (20)
Specification