Switching Power Supply Noise Reduction via Frequency Modulation
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Solution Overview
Problem
Conventional switching power supplies with fixed loads tend to produce stable oscillation frequencies, leading to increased noise, which requires the use of anti-noise components like filter circuits, thereby limiting size reduction and increasing costs.
Innovation Solution
The implementation of a modulation component applied to the oscillation frequency of a switching element, utilizing a control circuit with a drain current limiting circuit, secondary current on period detecting circuit, and secondary current on duty modulating circuit to maintain a constant on duty ratio and modulate the oscillation frequency, eliminating the need for anti-noise components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a fixed load is used to achieve stable switching operation, then the oscillation frequency becomes more stable, but noise increases requiring anti-noise components
Solution Approach 1:
The patent applies periodic modulation to the oscillation frequency of the switching element by varying the on-duty ratio in a periodic manner. This transforms the stable but noisy fixed-frequency operation into a modulated frequency operation that disperses the noise energy across a broader frequency spectrum, thereby reducing peak noise levels without requiring additional anti-noise components.
2Object-generated harmful factors
If anti-noise components like filter circuits are added to reduce noise, then noise is suppressed, but the size of the power supply increases
Solution Approach 1:
The patent extracts and eliminates the need for separate anti-noise components by integrating noise reduction functionality directly into the control mechanism of the switching element. Through periodic modulation of the on-duty ratio, the noise is reduced at its source without requiring external filter circuits or other noise suppression components, thereby maintaining a compact power supply design.
3Object-generated harmful factors
If anti-noise components are added to suppress noise, then noise is reduced, but costs increase
Solution Approach 1:
The patent eliminates the need for separate anti-noise components by integrating noise reduction functionality into the existing control circuitry. The periodic modulation of the switching element's on-duty ratio is achieved through existing control mechanisms without requiring additional filter circuits or noise suppression components, thereby reducing manufacturing costs while maintaining noise reduction effectiveness.
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 approach reduces noise without requiring filter circuits, allowing for a reduction in size and costs of the switching power supply, while maintaining accurate constant voltage and current control.
Implementation Method 1
a transformer having a primary winding and a secondary winding; a switching element; a control circuit controlling a switching operation of the switching element to perform switching control on a first DC voltage input to the switching element via the primary winding
Data Source
AI summary
The present invention provides a switching power supply that enables a reduction in noise without the need for an anti-noise component such as a filter circuit. A secondary current on period detecting circuit detects a first period during which a secondary current flows, the secondary current starting to flow through a secondary winding after a switching element is turned off. A secondary current on duty control circuit oscillates a clock signal set turning on the switching element so as to maintain, at a constant value, an on duty ratio of the first period to a third period made up of the first period and a second period during which the secondary current does not flow. A secondary current on duty modulating circuit applies a modulation component to the on duty ratio to periodically modulate the on duty ratio and thus the oscillation frequency of the switching element.