Switching Power-Supply Apparatus With Low-Threshold Voltage Elements

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Solution Overview

Problem

Existing switching power-supply apparatuses face challenges in achieving low loss, high efficiency, and stable control characteristics over a wide range of load variations, particularly at light loads, where zero voltage switching is difficult to maintain and switching elements require high withstand voltage, leading to increased switching loss.

Innovation Solution

A switching power-supply apparatus with a half-bridge primary-side power converter circuit and a secondary-side synchronous rectifier circuit, where switching elements perform complementary operations before and after a dead time, allowing zero voltage switching and energy regeneration from the secondary side to the primary side at light loads, using low-threshold voltage switching elements and leakage flux for inductance, reducing component count and size.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If switching elements are driven with high withstand voltage to handle light load conditions, then reliability is improved, but switching loss increases due to high on resistance

Engineering Contradiction:

Improvelight load control capabilityVSAvoidswitching loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent changes the voltage parameter of the switching elements from high withstand voltage to low threshold voltage, enabling the use of elements with lower on resistance while maintaining reliability through complementary driving control that ensures proper operation across all load conditions

Inventive Principle:

Principle #35Parameter changes

Solution Approach 2:

The patent implements dynamic complementary driving control where the first and second switching elements are driven in complementary manner with adjustable duty ratios, allowing the system to adapt to varying load conditions and maintain zero voltage switching while preventing both elements from being simultaneously on

Inventive Principle:

Principle #15Dynamics

2Reliability

If dead time is extended to prevent short circuit between switching elements, then reliability is improved, but zero voltage switching cannot be achieved and switching loss increases

Engineering Contradiction:

Improveshort circuit preventionVSAvoidswitching loss

Core Design Contradiction:

ReliabilityVSLoss of energy

Solution Approach 1:

The patent implements dynamic complementary driving control where the dead time is optimized and the duty ratios of switching elements are dynamically adjusted based on load conditions, allowing zero voltage switching to be achieved while maintaining reliable short circuit prevention through coordinated switching sequences

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent uses feedback control to monitor the state of switching elements and adjust their driving signals accordingly, ensuring that complementary driving is maintained and zero voltage switching is achieved without excessive dead time, thereby reducing switching loss while preventing short circuits

Inventive Principle:

Principle #23Feedback

3Stability of the object's composition

If duty ratio is reduced to control output voltage at light load, then output voltage stability is improved, but control becomes impossible when current becomes zero

Engineering Contradiction:

Improveoutput voltage stabilityVSAvoidcontrol capability

Core Design Contradiction:

Stability of the object's compositionVSEase of operation

Solution Approach 1:

The patent implements dynamic complementary driving control where the duty ratios of the first and second switching elements are dynamically adjusted based on load conditions. At light loads, the system switches to a mode where both elements can be driven with extended duty ratios while maintaining complementary timing, enabling continuous control capability even when inductor current approaches zero

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent inverts the conventional approach by using complementary driving where the second switching element is driven in opposition to the first, allowing one element to compensate when the other's duty ratio is reduced, thereby maintaining control capability across the full range of load conditions including light loads where conventional single-element control fails

Inventive Principle:

Principle #13The other way round (Inversion)

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 configuration enables low-loss, high-efficiency operation with stable output voltage control across a wide load range, reducing switching loss and cost by using low-threshold voltage switching elements and leveraging transformer leakage flux for inductance, thereby enhancing overall efficiency and reducing the circuit size.

Implementation Method 1

leveraging transformer leakage flux for inductance

Methodology Applied

Scientific EffectLeakage flux: Electromagnetic Induction

Implementation Method 2

allowing zero voltage switching

Methodology Applied

Scientific EffectZero voltage switching:

Data Source

PatentUS8837174B2Switching power-supply apparatus including switching elements having a low threshold voltage

Publication Date: 2014.09.16 MURATA MFG CO LTD

AI summary

In a switching power-supply apparatus, a primary-side power converter circuit includes a half bridge system and a synchronous rectifier circuit is provided as a rectifier circuit of a secondary-side power converter circuit. An on time ratio of the on time of a first switching element to the on time of a second switching element is controlled so as to provide an operation mode in which energy is regenerated from the secondary side to the primary side when the load is light.