Resonance Power Supply Efficiency via Frequency Fixing
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Solution Overview
Problem
Conventional resonance-type switching power supplies face inefficiencies due to reactive power caused by exciting inductance, increased conduction losses in rectifying diodes, and rising switching frequencies, particularly under varying load conditions.
Innovation Solution
The solution involves a switching power supply with a control circuit that includes an error amplifying circuit, oscillator circuit, frequency fixing circuit, and pulse width control circuit, where the ON-periods of switching devices are set shorter than the half-wave period of a series resonance current, and the exciting inductance is set to a larger value, eliminating air gaps in the transformer core to minimize reactive power and optimize pulse width control.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ON-period of switching devices is extended to maintain stable operation, then the reliability is improved, but the switching frequency increases causing higher losses
Solution Approach 1:
The patent applies parameter changes by optimizing the ON-period of switching devices to be shorter than the half-wave period of series resonance current. This parameter adjustment allows the system to operate reliably while minimizing switching frequency and reducing energy losses, directly resolving the contradiction between stability and efficiency
2Loss of energy
If the exciting inductance is increased to reduce reactive power, then the energy efficiency is improved, but the device complexity increases
Solution Approach 1:
The patent changes the physical parameter of the transformer core by eliminating air gaps and using a continuous magnetic path structure. This structural parameter change increases the exciting inductance naturally, reducing reactive power without requiring additional complex control mechanisms or components
Solution Approach 2:
The patent replaces the mechanical adjustment of inductance (through air gap control) with a structural design approach using continuous magnetic paths. This substitution achieves high exciting inductance through geometric configuration rather than mechanical adjustment, simplifying the overall device structure
3Adaptability or versatility
If the switching frequency is increased to improve dynamic response, then the adaptability is improved, but the conduction losses in rectifying diodes increase
Solution Approach 1:
The patent optimizes the switching frequency parameter to maintain it below the resonance frequency of the series resonance circuit. This parameter control enables the system to respond dynamically to load changes while keeping conduction losses in rectifying diodes minimized, resolving the contradiction between adaptability and energy efficiency
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 configuration reduces reactive power, minimizes rectifying diode losses, stabilizes switching frequency, and enhances conversion efficiency across different load conditions.
Implementation Method 1
By switching on and off MOSFET's Q1 and Q2 as described above, the voltages generated across secondary windings Ns1 and Ns2 in insulation transformer T1 are rectified and smoothed
Implementation Method 2
the ON-period of the first switching device and the ON-period of the second switching device are set to be shorter than a half-wave period of a series resonance current which flows through a series resonance circuit
Data Source
AI summary
A switching power supply includes a control circuit controlling ON and OFF of switching devices Q1 and Q2 and having an error amplifying circuit that controls a DC output voltage at a constant preset value, an oscillator circuit that controls the switching frequency in response to the output signal level FB of an error amplifying circuit, and a pulse width control circuit PWM that controls the pulse width in response to the output signal such that the ON-periods of switching devices Q1 and Q2 are equal to each other. The ON and OFF of switching devices Q1 and Q2 is controlled based on the output from oscillator circuit VCO when the output signal is higher than a threshold level. The switching frequency is fixed when the output signal level FB is lower than the threshold level.