US 5,903,138 A · Two-stage switching regulator having low power modes responsive to load power consumption

Abstract

A two-stage switching regulator having low power modes responsive to load power consumption. A first stage of the regulator is a power factor correction (PFC) stage. A second stage is a pulse-width modulating (PWM) stage. When a load draws a high level of current, switching in both stages is enabled. Under certain conditions, switching in either one or both of the stages is disabled by the duty cycle for the corresponding switch falling to zero. When switching in both stages is enabled, as in a normal mode, switching in the PWM stage is then disabled in response to an error signal falling below a first error threshold. When switching in the PFC stage is enabled and switching in the PWM stage is disabled, as in a first low power mode, switching in the PFC stage is then disabled in response to a feedback voltage rising above a first feedback threshold. When switching in both stages is disabled, as in a second low power mode, switching in the PWM stage is then enabled in response to the error voltage rising above a second error threshold, higher than the first error threshold. When switching in the PFC stage is disabled and switching in the PWM stage is enabled, as in a third low power mode, switching in the PFC stage is enabled in response to the feedback voltage falling below the second feedback threshold. As a result of these low power modes, the switching regulator is highly efficient.

Claims25

Dependent claims

A switching regulator comprising:

a. a first stage having a first switch the first stage for receiving an input voltage and for forming an intermediate voltage, wherein the intermediate voltage is regulated according to a duty cycle of the first switch;
b. a second stage having a second switch, the second stage coupled to receive the intermediate voltage for forming an output voltage, wherein the output voltage is regulated according to a duty cycle of the second switch;
and
c. a circuit for separately and selectively disabling switching of the first switch and the second switch according to power requirements of a load coupled to receive the output voltage, wherein the circuit for selectively disabling is coupled to the first stage and to the second stage.

1 more element

A method of conserving power consumed by a switching regulator wherein the switching regulator includes a first stage having a first switch and a second stage having a second switch and wherein the first stage supplies an intermediate signal to the stage and wherein second stage forms an output signal for supplying power to a load, the method comprising:

a. operating the switching regulator in a normal mode wherein a duty cycle of the first switch is adjusted according to a level of the intermediate signal and wherein a duty cycle of the second switch is adjusted according to difference between the output signal and a desired output signal;
b. operating the switching regulator in a first low power mode when the difference between the output signal and the desired output signal is lower than a first error threshold wherein the duty cycle of the first switch is adjusted according to a level of the intermediate output signal and the duty cycle of the second switch is zero;
and
c. operating the switching regulator in a second low power mode when the intermediate output signal is higher than a first feedback threshold wherein the duty cycle of the first switch is zero and wherein the duty cycle of the second switch is zero.

1 more element

Dependencies are inferred from the claim text.

Two-stage switching regulator having low power modes responsive to load power consumption

Life of this patent

Two-stage switching regulator having low power modes responsive to load power consumption

Life of this patent

Abstract

Claims25