DC-DC Converter Control Circuit for Output Voltage Overshooting

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Solution Overview

Problem

Conventional step-down DC-DC converters experience significant overshooting of output voltage when the load state suddenly changes from heavy to light or no load, leading to inefficiencies and prolonged overshooting periods due to inadequate control over the switching of transistors.

Innovation Solution

A control circuit that disables complementary switching of the main and synchronous transistors when the output voltage reaches a certain reference value, causing the coil current to change at a greater rate, and re-enables switching when the coil current reaches zero, allowing reverse flow and rapid discharge of excess energy, thus reducing overshooting.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Manufacturing precision

If the synchronous transistor T12 is activated after overshooting occurs to decrease output current, then the output voltage overshoot amount is reduced, but the current decreases gradually resulting in only small reduction of overshoot

Engineering Contradiction:

Improveoutput voltage control precisionVSAvoidcurrent decrease speed

Core Design Contradiction:

Manufacturing precisionVSSpeed

Solution Approach 1:

Instead of gradually decreasing current through continuous transistor activation, the invention inverts the approach by completely inactivating the synchronous transistor T12 to enable rapid current decrease. This binary switching approach (fully on/fully off) rather than gradual modulation allows the coil current to decrease much faster, thereby reducing the overshoot amount more effectively.

Inventive Principle:

Principle #13The other way round (Inversion)

Solution Approach 2:

The invention employs periodic switching control where the synchronous transistor T12 is repeatedly activated and inactivated in cycles. This periodic action allows the system to rapidly adjust the coil current by creating cycles of current buildup and release, enabling faster response to overshoot conditions compared to continuous gradual decrease.

Inventive Principle:

Principle #19Periodic action

2Stability of the object's composition

If the synchronous transistor T12 is continuously activated to maintain current flow, then the output voltage remains stable, but the overshooting period is prolonged

Engineering Contradiction:

Improveoutput voltage stabilityVSAvoidovershooting period duration

Core Design Contradiction:

Stability of the object's compositionVSDuration of action of moving object

Solution Approach 1:

The control circuit implements periodic switching of the synchronous transistor T12, alternating between activation and inactivation states. This periodic action creates a rhythm of current flow and release that maintains output voltage stability through controlled energy transfer while preventing prolonged overshoot by periodically releasing excess energy through transistor inactivation.

Inventive Principle:

Principle #19Periodic action

Solution Approach 2:

The invention transitions from static continuous transistor activation to dynamic periodic switching. The synchronous transistor T12 is dynamically controlled with changing activation patterns based on real-time output voltage conditions, allowing the system to adapt between maintaining stability and reducing overshoot duration according to operational needs.

Inventive Principle:

Principle #15Dynamics

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 solution effectively decreases the overshooting amount of the output voltage and shortens the overshooting period by enabling the coil current to flow reversely and efficiently discharge excess energy, improving the converter's stability and efficiency.

Implementation Method 1

The main transistor T11 is activated in response to a high (H) level control signal DHa to supply energy from an input terminal to an output terminal. Further, the main transistor T11 is inactivated to release energy accumulated in the coil L11.

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Implementation Method 2

The synchronous transistor T12 is activated in response to an H level control signal DLa generated in synchronization with the timing at which the energy accumulated in the coil L11 is released to a load.

Methodology Applied

Scientific EffectSynchronous rectification:

Data Source

PatentUS8823344B2Control circuit, electronic device, and method for controlling power supply

Publication Date: 2014.09.02 MONTEREY RESEARCH LLC

AI summary

A control circuit arranged in a power supply including first and second switches to control an output voltage of the power supply. The control circuit includes a first control circuit that switches the first and second switches in a complementary manner in accordance with a comparison result of a first reference voltage and a feedback voltage corresponding to the output voltage of the power supply. A first comparison circuit compares the output voltage or feedback voltage with a second reference value. A second comparison circuit compares a coupling point current flowing through a coupling point between the first and second switches with a third reference value. A second control circuit disables complementary switching of the first and second switches in accordance with an output signal from the first comparison circuit and enables the complementary switching in accordance with an output signal of the second comparison circuit.