Switching Regulator Power-Down Energy Recovery

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Solution Overview

Problem

Switching regulators face inefficiencies in power management, particularly in battery-operated systems, as energy stored in the output capacitor is lost during frequent startup and shutdown cycles, leading to energy wastage.

Innovation Solution

A method and circuit design that ramps down the reference voltage to 0V, causing the output voltage to decrease to 0V, allowing current to flow from the capacitor back to the battery, eliminating the need for additional components and ensuring the output remains at 0V during power-down by controlling high and low pass transistors.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Use of energy by stationary object

If the switching regulator is frequently started up and shut down, then the regulator can be powered off to save energy, but the energy stored in the output capacitor is lost

Engineering Contradiction:

Improvepower management efficiencyVSAvoidenergy stored in output capacitor

Core Design Contradiction:

Use of energy by stationary objectVSLoss of energy

Solution Approach 1:

The patent applies the discarding and recovering principle by redirecting the energy that would normally be discarded in the output capacitor during shutdown to be recovered and stored back in the battery. The method involves ramping down the reference voltage to cause the regulator to actively discharge the output capacitor through the inductor to the battery, transforming the waste energy into recoverable energy that can be reused in subsequent startup cycles.

Inventive Principle:

Principle #34Discarding and recovering

2Loss of energy

If additional components are added to recover energy from the output capacitor, then energy loss can be reduced, but the number of components increases

Engineering Contradiction:

Improveenergy stored in output capacitorVSAvoidnumber of components

Core Design Contradiction:

Loss of energyVSDevice complexity

Solution Approach 1:

The patent applies the self-service principle by utilizing the existing regulator circuitry to perform the energy recovery function. The same switching regulator that normally regulates voltage to the load is repurposed to actively discharge the output capacitor back to the battery during shutdown. This eliminates the need for separate recovery circuits or additional components, as the existing system serves the dual purpose of voltage regulation and energy recovery.

Inventive Principle:

Principle #25Self-service

3Loss of energy

If the reference voltage is ramped down to 0V to discharge the output capacitor, then energy can be recovered, but the output voltage must be controlled to remain at 0V

Engineering Contradiction:

Improveenergy stored in output capacitorVSAvoidoutput voltage control

Core Design Contradiction:

Loss of energyVSEase of operation

Solution Approach 1:

The patent applies the preliminary action principle by preparing the output stage transistors before initiating the reference voltage ramp-down. The high-side pass transistor is turned off and the low-side pass transistor is turned on in advance, ensuring that the output is properly configured to remain at 0V before the energy recovery process begins. This preliminary configuration prevents output voltage fluctuations and ensures clean energy transfer to the battery.

Inventive Principle:

Principle #10Preliminary action

Applied Scientific Principles

This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.

Function Achieved in This Case

This approach efficiently recovers energy stored in the output capacitor and minimizes component count, reducing energy loss and enhancing power management in switching regulators, especially in battery-powered devices.

Implementation Method 1

an error amplifier having two inputs and an output, wherein a first input is a reference voltage and a second input is an output voltage of the switching regulator, and the output of the amplifier controls a pulse-width modulation control unit controlling a configuration of switches configured to convert and regulate a DC voltage

Methodology Applied

Scientific EffectPulse-width modulation:

Implementation Method 2

said configuration of switches configured to convert and regulate a DC voltage using an inductor, said inductor, wherein a second terminal is connected is connected to an output port of the switching regulator

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 3

said output capacitor, wherein a second terminal is connected to ground

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 4

ramping down the reference voltage to 0 Volt such that the output voltage is ramped down to 0V by the regulator's switching regulation and a current through the inductor changes its direction and flows from the capacitor side to the battery's port and ground

Methodology Applied

Scientific EffectElectrical current flow: Conduction (electrical)

Data Source

PatentUS8878514B2Powering down switching regulator using a ramped reference voltage

Publication Date: 2014.11.04 DIALOG SEMICON GMBH

AI summary

Circuits and related methods for energy efficient battery supplied switching DC-to-DC regulators are disclosed. When entering a power-down state the energy in an output capacitor is harvested and charged back to the battery. This is achieved by ramping-down a reference voltage after a power-down sequence is initiated. The output voltage of the regulator is ramped-down accordingly. At the end of the power down sequence the output voltage of the regulator is down to 0V. The disclosure is especially important for regulators, which frequently are started up and switched down.