Switching Power Source Frequency Control for Transformer Saturation
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Solution Overview
Problem
Current flyback switching power sources with small core areas face issues of low inductance, leading to high iron loss and core saturation, and high switching frequencies result in significant efficiency losses, especially when handling high alternating currents.
Innovation Solution
A switching power source with a control module that adjusts the operational frequency inversely proportional to the amplitude of the alternating current, allowing the power source to switch between Continuous Inductor Current (CCM) and Discontinuous Inductor Current (DCM) modes, ensuring high inductance and preventing core saturation, and reducing losses by adjusting frequency according to input current amplitude.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If the switching frequency is increased to reduce transformer size, then the transformer achieves higher power density, but switching loss increases substantially
Solution Approach 1:
The patent implements dynamic frequency adjustment where the switching frequency varies according to the input voltage amplitude. During low input voltage periods, the frequency is reduced to minimize switching losses. During high input voltage periods, the frequency is increased to maintain high power density. This dynamic adaptation resolves the contradiction by making the frequency a variable parameter rather than a fixed value.
Solution Approach 2:
The patent changes the operational parameter (switching frequency) based on input conditions. By detecting input voltage amplitude and adjusting the frequency accordingly, the system optimizes the trade-off between transformer size and switching loss. The frequency is lowered when input voltage is low to reduce switching losses, and raised when input voltage is high to maintain compact transformer dimensions.
2Productivity
If the inductance is decreased to enable DCM operation, then the switching power source can operate in DCM mode, but iron loss increases due to large air gap
Solution Approach 1:
The patent dynamically adjusts the inductance value based on input voltage conditions. During high input voltage periods, the inductance is maintained at a higher value to reduce iron losses from large air gaps. During low input voltage periods, the inductance is decreased to enable DCM operation and improve switching speed. This dynamic adjustment resolves the contradiction between productivity and energy loss.
Solution Approach 2:
The patent changes the inductance parameter according to input voltage amplitude detection. By using a variable inductance approach rather than a fixed inductance value, the system can optimize for DCM operation when needed while minimizing iron losses when input voltage is high. The inductance is adjusted as a controllable parameter to balance switching performance and energy efficiency.
3Volume of moving object
If the core area is reduced to minimize power source size, then the power source becomes more compact, but core saturation occurs at high current
Solution Approach 1:
The patent implements dynamic frequency adjustment that prevents core saturation in compact transformers. By lowering the switching frequency during high input voltage conditions, the system reduces the peak current stress on the transformer core, preventing saturation. This allows the use of smaller core areas while maintaining reliability under varying load conditions.
Solution Approach 2:
The patent takes preliminary action to prevent core saturation by detecting input voltage amplitude and proactively adjusting the switching frequency before saturation can occur. During high input voltage periods, the frequency is reduced in advance to limit the energy transferred to the transformer, preventing core saturation. This preemptive approach allows compact transformer design without sacrificing reliability.
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 enables the use of transformers with small core areas while maintaining output power equivalent to those with larger cores, reducing iron loss and switching losses, thereby enhancing efficiency and preventing core saturation.
Implementation Method 1
a primary winding, connected with the main switching transistor and the filtering and rectifying module respectively, and configured to convert the direct current into an electromagnetic signal
Implementation Method 2
a secondary winding, configured to output a constant current according to the electromagnetic signal generated by the primary winding
Data Source
AI summary
A switching power source, a method and a control chip for controlling the same are provided. The switching power source includes: a filtering and rectifying module, connected with an AC power source and configured to filter and rectify an alternating current outputted from the AC power source to obtain a direct current; a control module, connected with the filtering and rectifying module and configured to obtain an amplitude of the alternating current from the direct current, to adjust a frequency of a control signal according to the amplitude, in which the control module decreases the frequency of the control signal continuously or intermittently when the amplitude increases, and to output the control signal; and a primary constant current circuit, connected with the control module and the filtering and rectifying module respectively, and configured to receive the control signal and to output a constant current according to the control signal.