On-Timing Circuit With Pseudo-Ripple for Stable Switching Power Supply
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Solution Overview
Problem
Conventional switching power supply devices with COT control systems using ceramic capacitors with low ESR face instability in output voltage control due to insufficient ripple voltage and noise interference, especially when input voltage varies widely, such as in vehicle applications.
Innovation Solution
A switching power supply device with an on-timing generation circuit that includes an error amplifier, common voltage generation, and ripple signal generation units to produce differential signals for accurate on-timing control, improving signal-to-noise ratio and stabilizing output voltage across varying input voltages.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If a ceramic capacitor with low ESR is used for smoothing output voltage, then the power supply device can operate with a wide range of input voltages, but sufficient ripple voltage cannot be obtained and output voltage control becomes unstable
Solution Approach 1:
The patent introduces a pseudo-ripple injection circuit as an intermediary component that generates artificial ripple voltage and adds it to the feedback signal. This mediator compensates for the insufficient natural ripple voltage caused by low-ESR ceramic capacitors, enabling stable output voltage control while maintaining the ability to operate with wide input voltage ranges.
Solution Approach 2:
The patent modifies the feedback signal parameters by injecting a pseudo-ripple voltage component. This changes the characteristics of the feedback signal to include sufficient ripple content, thereby enabling stable PWM control operation even when using low-ESR ceramic capacitors that would otherwise produce insufficient natural ripple voltage.
2Device complexity
If conventional COT control is used with low ESR ceramic capacitors, then device complexity is reduced, but control stability deteriorates due to insufficient ripple voltage
Solution Approach 1:
The pseudo-ripple injection circuit serves as an intermediary that adds minimal complexity to the control system. By injecting a simple artificial ripple signal into the feedback path, it provides sufficient ripple voltage for stable control without requiring complex circuit modifications or additional control mechanisms.
3Reliability
If pseudo-ripple injection is used to generate sufficient ripple voltage, then output voltage control stability is improved, but device complexity increases due to additional circuit components
Solution Approach 1:
The patent merges the pseudo-ripple injection function with the existing feedback circuitry. The injection circuit is integrated into the feedback signal path, combining multiple functions (ripple generation, signal addition, and feedback provision) into a unified circuit structure that minimizes additional component count and overall system complexity.
4Reliability
If ripple voltage is enhanced for stable control, then noise interference increases and common mode noise resistance decreases
Solution Approach 1:
The patent employs feedback mechanisms where the pseudo-ripple injection is controlled based on the actual output voltage conditions. The feedback loop monitors the system state and adjusts the injection level accordingly, ensuring sufficient ripple for stable control while preventing excessive injection that would amplify noise interference and reduce common mode noise resistance.
Data Source
AI summary
A switching power supply device includes an on-timing generation circuit that generates an on-timing signal for turning on a switching element. The on-timing generation circuit includes: an error amplifier that outputs an error amplification signal obtained by amplifying a difference between a feedback voltage and a reference voltage; a common voltage generation unit that generates a common voltage; a ripple signal generation unit that generates a forward phase ripple signal and a reverse phase ripple signal; and a comparator that generates the on-timing signal by comparing a pair of differential signals generated based on the error amplification signal, the common voltage, the forward phase ripple signal and the reverse phase ripple signal.