Power Supply Circuit Mode Switching Ripple Suppression
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Solution Overview
Problem
Conventional power supply circuits experience voltage ripple when switching between PWM and PFM control modes, leading to output voltage variations.
Innovation Solution
A power supply circuit with a control mechanism that adjusts the control value to maintain equal average feedback current before and after mode switching, using a switching signal generating circuit to control the drive signal in both PWM and PFM modes, ensuring the averages of the feedback current remain consistent.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the control mode is switched between PWM control and PFM control, then the power supply circuit can adapt to different load conditions, but a ripple occurs in output voltage causing variation in output voltage
Solution Approach 1:
The patent applies preliminary action by adjusting the control value in advance before the control mode switching occurs. The control value is modified based on the difference between the switching frequency immediately before switching and a reference frequency, ensuring that the average feedback current remains consistent across the transition. This preemptive adjustment prevents voltage ripple from occurring at the moment of mode switching between PWM and PFM control.
Solution Approach 2:
The patent employs feedback mechanisms by continuously monitoring the switching frequency and using it to dynamically adjust the control value. The feedback loop compares the actual switching frequency with the reference frequency and modifies the control value accordingly, ensuring that the average feedback current remains stable during mode transitions. This feedback control eliminates output voltage variations caused by control mode switching.
2Stability of the object's composition
If the switching frequency is adjusted to maintain average feedback current consistency, then voltage ripple is suppressed, but the control circuit complexity increases
Solution Approach 1:
The patent applies parameter changes by dynamically modifying the control value based on the switching frequency difference. Instead of adding complex hardware circuits, the invention changes the control parameter (control value) as a function of the measured switching frequency. This approach maintains output voltage stability by equalizing average feedback current across mode transitions while avoiding significant increases in control circuit complexity, as the adjustment can be implemented through existing control logic.
Data Source
AI summary
According to one embodiment, a power supply circuit includes a switching element to which a drive signal is supplied, a control value generating circuit that compares an output voltage and a reference voltage to generate a control value, and a comparison circuit that compares a feedback current and the control value. The power supply circuit has a generating circuit that generates a clock signal having a constant period in a PWM control mode and a clock signal according to the output voltage in a PFM control mode. The control value of the control value generating circuit is changed so that averages of the feedback current before and after the control mode switching become equal.