DC-DC Converter Frequency Stabilization via Variable Peak Current Control
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Solution Overview
Problem
DC-DC converters with peak-current control experience frequency fluctuations due to load current variations, leading to noise generation in audio devices and the need for high power supplies, as existing solutions fail to effectively control switching frequency outside human audible and radio broadcast ranges without increasing circuit scale or power supply capacity.
Innovation Solution
A DC-DC converter with a switching control circuit that performs peak-current control by turning on/off a switching element based on a combined current from a copied-current generating circuit and a reference current, ensuring the peak current through the inductor varies with load current, thereby stabilizing the operating frequency outside noise-prone ranges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If the DC-DC converter operates at a high switching frequency above 1.7 MHz to avoid noise, then the frequency is above radio broadcast range, but the converter with high boosting rate and large load capacity cannot be readily operated at such high frequency
Solution Approach 1:
The patent changes the control parameter from fixed peak current to variable peak current that adapts to load conditions. By dynamically adjusting the peak current based on load current feedback, the switching frequency is stabilized within the 500 kHz to 1.7 MHz range, achieving noise avoidance without requiring operation above 1.7 MHz where the converter cannot function properly
2Reliability
If peak-current control is used to maintain constant peak current regardless of voltage level, then the converter works with battery voltage variations, but the switching frequency fluctuates with load current causing noise generation
Solution Approach 1:
The patent introduces a feedback mechanism where the load current is detected and used to adjust the peak current setting. The load current detection circuit monitors the actual load conditions, and this information feeds back to the peak current control circuit, which dynamically adjusts the peak current to maintain stable switching frequency while adapting to both voltage and load variations
Solution Approach 2:
The patent transforms the static peak current control into a dynamic control system. The peak current is no longer fixed but varies dynamically based on load conditions. This dynamic adjustment allows the converter to maintain stable frequency under varying loads while still adapting to battery voltage variations, resolving the contradiction between reliability and noise generation
3Loss of energy
If the switching frequency is kept low to reduce switching losses, then the converter efficiency improves, but the frequency enters the human audible range of 20 Hz to 20 kHz causing uncomfortable noises
Solution Approach 1:
The patent optimizes the switching frequency parameter to operate in the 500 kHz to 1.7 MHz range, which is high enough to avoid audible noise but low enough to maintain acceptable switching losses. This frequency parameter selection, combined with the variable peak current control, achieves the optimal balance between energy efficiency and noise avoidance for this specific converter design
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 frequency fluctuations, preventing noise generation and minimizing power consumption at startup without increasing circuit scale or power supply capacity, ensuring stable operation within desired frequency ranges.
Implementation Method 1
a switching element that applies a direct current voltage from a direct current power supply to an inductor (coil) to allow a current to pass through and store energy in the inductor
Implementation Method 2
a rectifier circuit that rectifies the current in the inductor in an energy emission period when the switching element is off
Data Source
AI summary
A DC-DC converter, which allows a current to pass through an inductor and rectifies the current through the inductor to convert an input direct current voltage supplied from a direct current power unit into a direct current voltage at a different potential and output the direct current voltage, includes a switching control circuit performing peak-current control procedures including turning on the switching element when the converted direct current voltage drops to a predetermined potential and turning off the switching element when the current through the inductor reaches a predetermined value. The converter includes a copied-current generating circuit generating a current proportional to the output current. The switching control circuit turns off the switching element when the circuit detects that the current through the inductor reaches a predetermined value with reference to a combined current of the copied current generated at the copied-current generating circuit and a predetermined reference current.