Switching Power Supply Over-Current Protection

Solution Overview

Problem

Conventional switching power supplies for electronic control units in vehicles require multiple over-current detectors and current limiters for each switching circuit, increasing manufacturing costs and size due to the need to detect and limit currents in each circuit independently.

Innovation Solution

A switching power supply design with two switching units, where the maximum current of one unit is higher than the other, allowing the power supply to recognize and limit currents without detecting the lower current, thereby preventing over-currents without additional detectors, simplifying the structure and reducing costs.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If multiple over-current detectors and current limiters are added to each switching circuit, then over-current protection reliability is improved, but device complexity and manufacturing cost increase

Engineering Contradiction:

Improveover-current protection reliabilityVSAvoiddevice complexity

Core Design Contradiction:

ReliabilityVSDevice complexity

Solution Approach 1:

The patent merges the current detection function into a single shared detector that measures the total current from all switching circuits combined, rather than having separate detectors for each circuit. The control unit then distributes this detection information to coordinate current limiting across all circuits, reducing the number of detectors and limiters while maintaining protection reliability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The single over-current detector serves multiple switching circuits simultaneously by detecting the combined current output. The control unit universally manages current limiting for all circuits based on this single detection point, making the detection system multi-functional across different circuit phases

Inventive Principle:

Principle #6Universality (Multi-functionality)

2Reliability

If multiple over-current detectors and current limiters are added to each switching circuit, then over-current protection reliability is improved, but manufacturing cost increases

Engineering Contradiction:

Improveover-current protection reliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent merges the current detection function into a single shared detector that measures the total current from all switching circuits combined, rather than having separate detectors for each circuit. The control unit then distributes this detection information to coordinate current limiting across all circuits, reducing the number of detectors and limiters while maintaining protection reliability

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The control unit creates virtual copies of the current limitation function by distributing the single detection signal to multiple switching circuits, allowing each circuit to be controlled without requiring physical duplicate detectors and limiters in each circuit

Inventive Principle:

Principle #26Copying

3Reliability

If multiple over-current detectors and current limiters are added to each switching circuit, then over-current protection reliability is improved, but the size of the power supply increases

Engineering Contradiction:

Improveover-current protection reliabilityVSAvoidpower supply size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent merges the current detection function into a single shared detector that measures the total current from all switching circuits combined, rather than having separate detectors for each circuit. The control unit then distributes this detection information to coordinate current limiting across all circuits, reducing the number of detectors and limiters while maintaining protection reliability

Inventive Principle:

Principle #5Merging (Combining)

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 design effectively prevents over-currents in switching units while reducing the size and manufacturing costs of the power supply, allowing for reliable operation without the need for multiple current detectors.

Implementation Method 1

a first switching unit receives an input voltage from an external power source and performs a first switching operation to intermittently receive a first electric current from the external power source and to produce a first voltage, different from the input voltage, from the input voltage and the first electric current

Methodology Applied

Scientific EffectElectromagnetic induction: Electromagnetic Induction

Data Source

PatentUS8120339B2Switching power supply with switching circuits

Publication Date: 2012.02.21 DENSO CORP

AI summary

A switching power supply has first and second switching units and a control unit. Each switching unit has a switching element performing a switching operation to intermittently receive electric current from a battery while accumulating electric power in a coil and discharging this power to an output terminal. A resistor earthed is serially connected with each switching element. The resistance of the first resistor receiving the first current from the first switching element is lower than that of the second resistor receiving the second current from the second switching element. A maximum value of the first current is higher than that of the second current due to the difference between the resistors. The control unit controls the switching operations of the elements to boost the voltage of the battery and stops the switching operations in response to the first current exceeding an upper value.