Dual Edge Delay Control for Spread-Spectrum Current-Mode Converters
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Solution Overview
Problem
Spread spectrum frequency modulation in DC-to-DC converters and switch mode power supplies causes increased noise at the spread spectrum modulation frequency, degrading the low-frequency range performance and requiring converter inductor information for gain adjustment.
Innovation Solution
The apparatus includes a regulator, clock generator, current control comparator, and driver circuit, with a spread spectrum modulation circuit that modulates the switching frequency and uses dual edge delays to control switch turn-on and turn-off times, maintaining average inductor current and reducing ripple and noise.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If spread spectrum frequency modulation is used to reduce energy in certain frequency bands, then EMI performance is improved, but noise at the spread spectrum modulation frequency increases and low-frequency range performance degrades
Solution Approach 1:
The patent applies preliminary anti-action by introducing compensating delay signals before the spread spectrum modulation takes effect. The first delay generator creates a delay signal proportional to the spread spectrum modulation amount, and the second delay generator creates another delay signal proportional to both the modulation amount and duty cycle. These compensating signals are injected into the switching control paths to counteract the adverse effects of frequency modulation on inductor current and output voltage before they can degrade low-frequency performance.
Solution Approach 2:
The patent implements feedback by using the spread spectrum modulation signal itself as a feedback input to the delay generators. The modulation signal that causes the frequency deviation is fed back to control the compensating delay amounts, creating a closed-loop system where the compensation is dynamically adjusted based on the actual modulation amount, thereby optimizing the cancellation of adverse effects in real-time.
2Object-affected harmful factors
If spread spectrum modulation is applied to reduce switching frequency noise, then EMI compliance is improved, but ripple on input and output increases
Solution Approach 1:
The patent applies preliminary anti-action by generating compensating delay signals that counteract the ripple effects of spread spectrum modulation before they manifest on the input and output. The delay generators create timing adjustments that pre-compensate for the frequency variations, preventing the ripple from developing in the first place rather than attempting to filter it afterward.
3Reliability
If compensating regulation control signals are used to address low-frequency performance degradation, then converter performance is improved, but converter inductor information is required for correct gain adjustment
Solution Approach 1:
The patent applies self-service by making the delay generators derive their delay amounts directly from the spread spectrum modulation signal and duty cycle signal that are already present in the system. The first delay generator uses the modulation signal, and the second delay generator uses both the modulation signal and duty cycle signal, eliminating the need for external inductor information or additional sensing circuits. The system uses its own existing signals to generate the necessary compensation.
Data Source
AI summary
An apparatus includes a regulator, a modulation circuit, a first delay generator, and a second delay generator. The regulator generates a regulator control output signal to control a current of a power converter to regulate an output voltage of the power converter, the modulation circuit modulates a switching frequency of the power converter, the first delay generator controls a first delay time to turn on a switch of the power converter in a switching cycle, based on a change in the switching frequency of the power converter, and the second delay generator controls a second delay time to turn the switch of the power converter off in the switching cycle, based on the first delay time and a duty cycle of the power converter.