DC-DC Converter Pseudo Ripple Generation Circuit
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Solution Overview
Problem
Hysteresis controlled DC-DC converters face challenges in stable operation when using ceramic capacitors due to their low equivalent series resistance (ESR), leading to minimal ripple component in output voltage, which hampers switching element control, and existing ripple injection techniques are susceptible to noise.
Innovation Solution
A DC-DC converter design that employs a pseudo ripple generation circuit and comparison circuit to generate and smooth pseudo ripple voltages, and controls switching elements based on comparison results, excluding noise-sensitive pseudo ripple comparisons when the load is light to ensure stable operation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Volume of moving object
If ceramic capacitors are used to reduce device size, then miniaturization is achieved, but the low ESR causes minimal ripple component in output voltage which hampers switching element control
Solution Approach 1:
The patent introduces a pseudo ripple generation circuit as an intermediary component that artificially generates a ripple component in the feedback voltage signal. This mediator compensates for the insufficient natural ripple caused by low-ESR ceramic capacitors, enabling reliable switching element control while maintaining the use of compact ceramic capacitors.
Solution Approach 2:
The patent changes the parameter of the feedback voltage by adding a pseudo ripple component through the pseudo ripple generation circuit. This modifies the voltage characteristics to ensure sufficient ripple amplitude for reliable switching control, resolving the contradiction between using low-ESR capacitors and maintaining control stability.
2Reliability
If pseudo ripple injection technique is employed to enable switching control, then switching element control is improved, but noise susceptibility increases especially at light loads
Solution Approach 1:
The patent implements dynamic control by switching between two operational modes: using pseudo ripple injection during normal operation to ensure switching control, and disabling pseudo ripple injection during light load conditions to eliminate noise susceptibility. This dynamic adaptation resolves the contradiction between control reliability and noise resistance.
Solution Approach 2:
The patent applies different control strategies to different operating conditions: pseudo ripple injection is applied locally during normal operation where it is needed, while being excluded during light load conditions where it causes noise problems. This localized application resolves the contradiction by tailoring the solution to specific operational contexts.
3Reliability
If pseudo ripple voltage is continuously injected to maintain switching control, then switching element control stability is improved, but operational stability at light loads deteriorates due to noise influence
Solution Approach 1:
The patent dynamically adjusts the control strategy based on load conditions, switching between pseudo ripple injection and feedback voltage comparison modes. This dynamic approach maintains switching control stability during normal operation while ensuring operational stability at light loads by eliminating noise-prone pseudo ripple injection.
Solution Approach 2:
The patent takes preliminary anti-action by detecting light load conditions and preemptively disabling pseudo ripple injection before noise can disrupt operational stability. This preventive measure resolves the contradiction by avoiding the noise susceptibility issue before it occurs.
Data Source
AI summary
The DC-DC converter includes: a switching element connected between an inductor and a power supply terminal; a pseudo ripple generation circuit configured to generate a pseudo ripple voltage depending on a ripple component that is generated in the output voltage, and a smoothed voltage by smoothing the pseudo ripple voltage; a comparison circuit configured to combine a first comparison result obtained by comparing the pseudo ripple voltage and the smoothed voltage to each other, and a second comparison result obtained by comparing a reference voltage and a feedback voltage obtained by dividing the output voltage to each other, and output a comparison result signal; and an output control circuit configured to control the switching element to be turned on and off based on the comparison result signal. The comparison circuit is configured to output only the second comparison result, as the comparison result signal, when a load becomes lighter.