Power Supply Ripple Reduction via Current Gradient Detection
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Solution Overview
Problem
DC-DC converters with small equivalent series resistance (ESR) smoothing capacitors face instability in feedback systems and control cycles, leading to irregular coil voltage and current, resulting in fluctuating output voltages due to ripple components.
Innovation Solution
A power supply device with a converter unit and control circuit that includes a current gradient detection circuit to detect the gradient of the coil current during the off period, generating a slope voltage and using an adder circuit to adjust the feedback and reference voltages, thereby stabilizing the output voltage by reducing ripple components.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-generated harmful factors
If a smoothing capacitor with small ESR is used to reduce output voltage ripple, then the output voltage ripple is reduced, but the feedback system and control cycle become unstable
Solution Approach 1:
The patent introduces a feedback mechanism that detects the coil current gradient during the off period and uses this information to adjust the switch control timing. The current gradient detection circuit monitors the rate of change of coil current, and this feedback is used to compensate for the instability caused by small ESR capacitors, thereby maintaining both low ripple and system stability
Solution Approach 2:
The patent performs preliminary detection of the coil current gradient during the off period before the next switching cycle begins. By detecting the current gradient in advance and using this information to set the appropriate timing for the next switch turn-on, the system proactively prevents instability rather than reacting to it after it occurs
2Object-generated harmful factors
If a smoothing capacitor with small ESR is used to reduce output voltage ripple, then the output voltage ripple is reduced, but the coil voltage and current become irregular
Solution Approach 1:
The current gradient detection circuit provides real-time feedback on the coil current characteristics during the off period. This feedback information is used to adjust the switching control, ensuring that the coil voltage and current maintain stable, predictable patterns even when using small ESR capacitors that would otherwise cause irregularities
3Power
If the switch circuit is on/off controlled to generate output voltage, then the output voltage can be regulated, but ripple voltage is generated due to coil current and ESR
Solution Approach 1:
The patent replaces the traditional method of ripple reduction (relying on capacitor ESR) with an electronic control mechanism. Instead of using the physical property of capacitor resistance to filter ripple, the system uses active detection of current gradient and electronic adjustment of switch timing to eliminate ripple, thereby achieving low ripple without the stability penalties of small ESR capacitors
Data Source
AI summary
A power supply device including a converter having a switch circuit to which an input voltage is supplied and a coil coupled between the switch circuit and an output end from which an output voltage is output; and a control circuit comparing between a feedback voltage and a reference voltage, and on/off controls the switch circuit according to a comparison result; wherein, the control circuit includes a current gradient detection circuit performs detection of a gradient of a coil current flows thorough the coil during an off period of the switch circuit and generates a slope voltage according to a result of the detection; and an adder circuit performs one of generating the feedback voltage by adding the slope voltage to a voltage according to the output voltage and generating the reference voltage by adding the slope voltage to a standard voltage that is set according to the output voltage.