DC-DC Converter Undershoot Reduction via Phase Compensation

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Solution Overview

Problem

Conventional DC-DC converters experience a large undershoot when switching from bypass mode to boost mode due to the voltage output being clamped at ground level, which hampers the boosting operation and requires a longer period for the error voltage to become zero, preventing immediate switching with the load current.

Innovation Solution

A DC-DC converter design that includes an error amplifier, phase compensation impedance element, determination unit, and voltage setting unit to monitor and adjust the voltage at the phase compensation impedance element, ensuring it is set higher than the ground voltage in bypass mode, thereby reducing the period required for the error voltage to zero when switching to boost mode, allowing immediate switching with the load current.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Device complexity

If the voltage output of the error amplifier is clamped at ground level in bypass mode, then the circuit structure is simple, but a large undershoot occurs when switching to boost mode and the switching response is delayed

Engineering Contradiction:

Improvecircuit structureVSAvoidswitching response speed

Core Design Contradiction:

Device complexityVSSpeed

Solution Approach 1:

The patent applies preliminary action by pre-charging the phase compensation impedance element to a predetermined voltage level before mode switching occurs. The voltage setting unit charges the impedance element to a voltage higher than ground level during bypass mode, so when switching to boost mode, the error voltage is already close to the target value, enabling immediate switching without delay or undershoot.

Inventive Principle:

Principle #10Preliminary action

2Speed

If the voltage at the phase compensation impedance element is set higher than ground level in bypass mode, then the switching response to boost mode is immediate, but additional control circuitry is required

Engineering Contradiction:

Improveswitching response speedVSAvoidcontrol circuitry

Core Design Contradiction:

SpeedVSDevice complexity

Solution Approach 1:

The voltage setting unit is designed to perform multiple functions: it charges the phase compensation impedance element to a predetermined voltage during bypass mode, maintains this voltage level, and automatically discharges it when boost mode is activated. This multi-functional design achieves fast switching response without requiring separate dedicated circuits for each function.

Inventive Principle:

Principle #6Universality (Multi-functionality)

Solution Approach 2:

The patent introduces a voltage setting unit as an intermediary component between the error amplifier and the phase compensation impedance element. This intermediary actively controls the voltage level at the impedance element, mediating the transition between bypass and boost modes to eliminate undershoot and enable immediate switching response.

Inventive Principle:

Principle #24Intermediary (Mediator)

3Stability of the object's composition

If the error voltage takes a longer period to become zero when switching from bypass to boost mode, then the circuit is stable in bypass mode, but the boosting operation performance is hampered and load current switching is delayed

Engineering Contradiction:

Improvebypass mode stabilityVSAvoidboosting operation efficiency

Core Design Contradiction:

Stability of the object's compositionVSProductivity

Solution Approach 1:

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

The solution reduces the undershoot occurring during mode switching by ensuring the voltage setting unit establishes a short circuit between the phase compensation impedance element ends in bypass mode and cancels it in boost mode, enabling immediate switching operations consonant with load currents, thus minimizing the undershoot.

Implementation Method 1

a phase compensation impedance element for performing phase compensation, and for accumulating the error across one end to generate an error voltage

Methodology Applied

Scientific EffectCapacitance: Capacitance

Implementation Method 2

the voltage setting unit establishes a short circuit between the phase compensation impedance element ends in bypass mode and cancels it in boost mode

Methodology Applied

Scientific EffectElectrical Conduction: Conduction (electrical)

Data Source

PatentUS9263932B2DC-DC converter

Publication Date: 2016.02.16 ASAHI KASEI MICRODEVICES CORP

AI summary

A DC-DC converter includes: an error amplifier for outputting an error between an output voltage and a predetermined voltage; a phase compensation impedance element for accumulating the error across one end to generate an error phase; a determination unit for determining whether the voltage output by the error amplifier is higher, or lower than a reference voltage that is consonant with the predetermined voltage, and outputting a determination signal indicating determination results; and a voltage setting unit for setting a voltage for one end of the phase compensation impedance element higher than a lower output voltage limit for the error amplifier when the determination signal indicates that the voltage output by the error amplifier is lower than the reference voltage, or for canceling setting of the voltage when the determination signal indicates that the voltage output by the error amplifier is higher than the reference voltage.