Switching Power Supply Circuit Audible Noise Reduction
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Solution Overview
Problem
Conventional switching power supply circuits experience a buzzing noise due to switching frequencies within the audible range during the power-on mode, in addition to the standby mode.
Innovation Solution
A switching power supply circuit with a control circuit that adjusts the current-to-voltage ratio for a photocoupler to control the switching operation, ensuring the switching frequency is outside the audible range in both standby and power-on modes by using a first and second rectifier circuit, a switching transformer, and a photocoupler for feedback control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If the switching frequency is reduced in standby mode, then power consumption and transformer buzz are reduced, but the switching frequency may fall within the audible range causing noise
Solution Approach 1:
The patent applies dynamics by making the switching frequency adjustable based on operational mode. The control circuit dynamically changes the switching frequency between a first frequency (lower) in standby mode and a second frequency (higher) in power-on mode, allowing optimization of both power consumption and noise characteristics for each mode without compromise
Solution Approach 2:
The patent changes the switching frequency parameter between two distinct values depending on operational mode. In standby mode, a lower frequency reduces power consumption and transformer buzz, while in power-on mode, a higher frequency prevents audible noise. This parameter switching resolves the contradiction between energy efficiency and noise reduction
2Object-affected harmful factors
If the switching frequency is increased to avoid audible noise in power-on mode, then noise is reduced, but power consumption increases
Solution Approach 1:
The control circuit dynamically adjusts the switching frequency based on the operational mode of the power supply. During power-on mode, a higher frequency eliminates audible noise, while during standby mode, a lower frequency reduces power consumption. This dynamic adaptation allows the system to optimize both noise and energy characteristics
Solution Approach 2:
The patent employs periodic switching between two frequency regimes corresponding to different operational modes. The control circuit periodically monitors the operational state and switches between the first (lower) and second (higher) frequencies, creating a periodic action pattern that optimizes performance for each mode
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
The solution effectively reduces noise in the switching transformer across both operational modes, maintaining low power consumption and minimizing audible noise in audio systems.
Implementation Method 1
a first rectifier circuit configured to rectify the AC power and convert the AC power to a direct current
Implementation Method 2
a switching transformer including a primary coil supplied with the current switched by the switching operator, and a secondary coil inducing power corresponding to the current supplied to the primary coil
Implementation Method 3
a second rectifier circuit configured to rectify the power induced by the secondary coil of the switching transformer and output the DC power
Implementation Method 4
a photocoupler configured to feed back a signal from a secondary side to a primary side in accordance with a flowing current
Data Source
Figure 1
Figure 2(a)~2(b)
Figure 3
AI summary
A switching power supply circuit (101) includes a first rectifier circuit (102) converting an alternate current to a direct current, a switching operator (20), a switching transformer (103) including a primary coil supplied with a switched current and a secondary coil inducing power corresponding to the current, a second rectifier circuit (30) rectifying the power induced by the secondary coil, and a control circuit (40) changing a ratio of a current flowing to a photocoupler (107) to an output voltage from the second rectifier circuit (30) in a standby mode and in a power-on mode to reduce a noise of the switching transformer in each of the modes.