Switching Power Supply Dynamic Frequency Control
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Solution Overview
Problem
Conventional switching power supplies face inefficiencies due to high switching loss and conduction noise, particularly in high-AC power-supply-voltage regions, where the switching frequency is maximized, leading to increased coil current and reduced conversion efficiency.
Innovation Solution
A switching power supply that dynamically adjusts its switching frequency based on input voltage and current control signals, increasing frequency at zero-cross of AC power supply voltage and decreasing it at peak voltage, thereby dispersing the switching frequency to reduce switching loss and conduction noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is maximized in high-AC power-supply-voltage regions, then the power factor correction is improved, but the switching loss increases and conversion efficiency decreases
Solution Approach 1:
The patent applies dynamics by making the switching frequency variable rather than fixed. The frequency setting circuit dynamically adjusts the switching frequency based on the AC power supply voltage level: using higher frequencies when voltage is low and lower frequencies when voltage is high. This dynamic adaptation resolves the contradiction by optimizing power factor correction at each voltage level while minimizing switching loss.
Solution Approach 2:
The patent changes the parameter of switching frequency according to operating conditions. By detecting the AC power supply voltage and adjusting the switching frequency accordingly, the system achieves efficient power factor correction across varying voltage conditions without incurring excessive switching losses at high voltage levels.
2Volume of moving object
If the switching frequency is raised to reduce inductor size, then the power supply circuit compactness is improved, but the switching loss increases and conversion efficiency decreases
Solution Approach 1:
The patent uses dynamic frequency adjustment to achieve a compromise between inductor size and switching loss. Rather than operating at a fixed high frequency that minimizes inductor size but maximizes switching loss, the system adapts the frequency to operating conditions, reducing frequency (and thus switching loss) when voltage is high while maintaining adequate power factor correction.
Solution Approach 2:
The switching frequency parameter is changed based on AC power supply voltage detection. This parameter change allows the system to optimize the trade-off between inductor size and switching loss by using higher frequencies only when necessary (at low voltage conditions) and lower frequencies when switching loss would be excessive (at high voltage conditions).
3Loss of energy
If the switching frequency is lowered to improve conversion efficiency, then the switching loss is reduced, but the filter circuit size must be enlarged to remove conduction noise
Solution Approach 1:
The patent applies dynamics by varying the switching frequency according to AC power supply voltage. This dynamic approach allows the system to use lower frequencies (reducing switching loss) when voltage is high, while using higher frequencies (reducing filter size requirements) when voltage is low. The frequency setting circuit ensures optimal balance between switching loss and filter size across different operating conditions.
4Loss of energy
If the switching frequency is dispersed to reduce switching loss and conduction noise, then the conversion efficiency is improved, but the control circuit complexity increases
Solution Approach 1:
The patent implements feedback by detecting the AC power supply voltage and using this information to adjust the switching frequency. The voltage detection circuit provides feedback to the frequency setting circuit, creating a closed-loop control system that automatically optimizes the switching frequency based on operating conditions, thereby reducing switching loss without requiring complex manual control.
Solution Approach 2:
The patent introduces an intermediary frequency setting circuit that mediates between the voltage detection circuit and the oscillation circuit. This intermediary component translates voltage detection signals into appropriate frequency control signals, simplifying the overall control architecture while achieving the desired frequency dispersion to reduce switching loss and conduction noise.
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 enhances conversion efficiency, reduces switching loss, and minimizes conduction noise by optimizing switching frequency distribution, allowing for a smaller filter circuit size and improved power factor correction.
Implementation Method 1
rectifier circuit conducting full-wave rectification of an AC power supply for obtaining a pulsating output
Implementation Method 2
an inductor having a first end connected to the rectifier circuit, a capacitor smoothing the current fed from the inductor
Implementation Method 3
a capacitor smoothing the current fed from the inductor for obtaining a DC output
Data Source
AI summary
A switching power supply has a full-wave AC rectifier circuit; a chopper circuit including an inductor, a capacitor smoothing current from the inductor, and a switching device for on-off control of the current fed to the capacitor. The rectifier circuit further has an input voltage detector circuit detecting chopper circuit input voltage; an output voltage error detector circuit detecting an error between an output voltage from the chopper circuit and a set voltage; a current control signal generator circuit generating a current control signal in-phase with an input voltage detection signal having a waveform similar to the input voltage detection signal and an amplitude proportional to an output voltage error signal; a current detector circuit detecting inductor current flow; a frequency setting circuit; an oscillator circuit; and a switching control circuit switching the switching device based on oscillation circuit signal, the current control signal, and the current detection signal.