Switching Power Supply PWM Control to Prevent Transformer Saturation

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Solution Overview

Problem

Existing switching power supply devices face challenges in preventing transformer saturation while maintaining efficient maximum on duty control, particularly in devices using transformers.

Innovation Solution

The implementation of a controller with a current source, voltage source, PWM signal generation, and comparison circuit to directly control the switching element, utilizing a one-way conduction element and digital processor for accurate PWM signal generation, thereby reducing component count and cost while ensuring maximum on duty control and preventing transformer saturation.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Volume of stationary object

If maximum on duty control is implemented to prevent transformer saturation, then transformer size can be reduced, but device complexity increases due to additional control circuits

Engineering Contradiction:

Improvetransformer sizeVSAvoidcontrol circuit complexity

Core Design Contradiction:

Volume of stationary objectVSDevice complexity

Solution Approach 1:

The patent combines the maximum on duty control function with the existing PWM control circuit by integrating a duty ratio determination circuit that calculates the maximum on duty based on transformer parameters and operating conditions. This merging approach enables transformer saturation prevention without adding completely separate control circuits, thus reducing transformer size while limiting the increase in device complexity.

Inventive Principle:

Principle #5Merging (Combining)

Solution Approach 2:

The patent implements a feedback mechanism where the duty ratio determination circuit continuously monitors transformer operating conditions (such as current and voltage) and adjusts the switching duty ratio in real-time to maintain operation below saturation points. This feedback control ensures transformer saturation prevention while using a compact integrated circuit design rather than complex external control systems.

Inventive Principle:

Principle #23Feedback

2Reliability

If complex control circuits are added to achieve precise maximum on duty control, then transformer saturation prevention improves, but manufacturing cost increases

Engineering Contradiction:

Improvetransformer saturation preventionVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent replaces complex analog control circuits with a digital duty ratio determination circuit that calculates maximum on duty using digital processing of transformer parameters. This substitution reduces the number of precision analog components required, improving saturation prevention reliability while lowering manufacturing costs through standard digital circuit implementation.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

Solution Approach 2:

The patent changes the control approach from fixed duty ratio to dynamically calculated duty ratio based on transformer parameters (inductance, resistance, operating frequency) and real-time operating conditions. This parameter-based control enables precise saturation prevention adapted to different transformer specifications without requiring custom circuit designs for each variant, thereby reducing manufacturing costs.

Inventive Principle:

Principle #35Parameter changes

3Productivity

If traditional control methods are used, then device structure remains simple, but efficiency is reduced due to inability to maintain optimal on duty

Engineering Contradiction:

Improvepower supply efficiencyVSAvoidcontrol structure

Core Design Contradiction:

ProductivityVSDevice complexity

Solution Approach 1:

The patent introduces dynamic adjustment of the switching duty ratio based on real-time transformer operating conditions through the duty ratio determination circuit. This dynamic control allows the system to maintain optimal on duty across varying load conditions and input voltages, improving power supply efficiency while using a relatively simple integrated control structure that adapts automatically rather than requiring complex manual tuning.

Inventive Principle:

Principle #15Dynamics

Data Source

PatentUS12537453B2Switching power supply device, switching control device, and industrial equipment

Publication Date: 2026.01.27 ROHM CO LTD

AI summary

A switching power supply device includes a switching element and a controller. The controller includes a current source circuit, a voltage source circuit, a PWM signal generation circuit, a capacitor of which the first terminal is connected to the current source circuit and of which the second terminal is connected to the PWM signal generation circuit, a one-way conduction element provided between the first terminal of the capacitor and the voltage source circuit and configured to pass only a current flowing from the capacitor toward the voltage source circuit, and a comparison circuit configured to compare the voltage appearing at the first terminal of the capacitor with a voltage based on the output voltage of the switching power supply device and to control the switching device based on the result of the comparison.