Resonant DC-DC Converter Standby Noise Suppression
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Solution Overview
Problem
Current-resonant DC-DC converter switching power source devices face noise issues during standby mode due to sudden changes in resonant current when switching stops, leading to audible noise, and existing solutions like PWM control are not applicable for frequency-changing converters, with no effective handling of ineffective regions.
Innovation Solution
A switching power source device with a transformer having a primary, secondary, and auxiliary coil, using a control circuit that generates frequency control voltages based on auxiliary coil voltages to adjust switching frequency, incorporating a charging/discharging unit to manage burst operations, and an output voltage detecting unit to set switching frequency, effectively handling soft start and soft end operations and ineffective regions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Use of energy by moving object
If switching is stopped immediately in standby mode to reduce power consumption, then power consumption is reduced, but audible noise is generated due to sudden resonant current changes
Solution Approach 1:
The control circuit gradually reduces the switching frequency before stopping switching operations, preparing the resonant current for gradual decrease rather than sudden termination. This preliminary action prevents the transient phenomenon that causes audible noise while maintaining low power consumption in standby mode.
Solution Approach 2:
The switching frequency is dynamically adjusted during standby mode, transitioning from a fixed frequency to a gradually decreasing frequency before cessation. This dynamic control allows the system to adapt the switching behavior to minimize noise while managing power consumption effectively.
2Use of energy by moving object
If switching frequency is reduced to save power in standby mode, then power consumption is reduced, but the system becomes less responsive to load changes
Solution Approach 1:
The control circuit employs burst operation with periodic switching cycles during standby mode, alternating between active switching periods and pause periods. This periodic action reduces average power consumption while maintaining the capability to respond to load changes during the active switching periods.
Solution Approach 2:
The switching frequency and duty cycle are dynamically adjusted based on detected output voltage and current conditions, allowing the system to optimize between power savings and responsive behavior according to actual load requirements.
3Object-generated harmful factors
If soft start operation is implemented to gradually increase resonant current, then noise is reduced during startup, but the startup time is extended
Solution Approach 1:
The control circuit implements soft start by preliminarily increasing the switching frequency before the main switching operation begins, allowing resonant current to build up gradually. This preliminary frequency adjustment reduces noise during startup while minimizing the extension of startup time through optimized frequency transition.
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 significantly improves noise suppression during burst operations in standby mode by dynamically adjusting switching frequency based on auxiliary and output voltages, reducing the ineffective region and minimizing audible noise.
Implementation Method 1
switching elements being turned ON and OFF to convert inputted direct current into high-frequency current and supply the high-frequency current to the primary coil of the transformer, thereby generating high-frequency current at the secondary coil of the transformer
Implementation Method 2
current-resonant DC-DC converter switching power source device
Data Source
AI summary
A switching power source device according to one aspect of the present invention is a current-resonant DC-DC converter, and includes a control integrated circuit having an oscillation circuit that determines a switching frequency of switching elements and a burst control circuit that controls a burst operation in the standby mode, as well as an output voltage detecting unit connected to a secondary side of a transformer to detect an output voltage. The switching frequency of the switching element is determined by the oscillation circuit by the smaller of a first frequency control voltage generated from a voltage of an auxiliary coil disposed in the primary side of the transformer and a second frequency control voltage corresponding to the output voltage, and the burst control circuit generates the first frequency control voltage that gradually increases or decreases in accordance with the voltage of the auxiliary coil.