Constant Frequency ON-Time Control System for Voltage Regulator Stability
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Solution Overview
Problem
Conventional constant frequency ON-time control systems face a limitation where the minimum OFF-time restricts the modulation of ON-time, leading to an over-low output voltage when attempting to shorten the OFF-time below a certain threshold.
Innovation Solution
A constant frequency ON-time control system with a frequency setting parameter adjusting circuit that modulates the frequency setting parameter when the OFF-time is shorter than a reference value, increasing the ON-time to maintain output voltage stability, comprising an error amplifier, low-pass filter, polarity selection circuit, and computing circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Power
If the OFF-time is shortened below the minimum OFF-time threshold, then the ON-time can be increased to improve output voltage, but the minimum OFF-time limitation prevents further modulation and causes output voltage to drop
Solution Approach 1:
The patent implements dynamic frequency setting by making the frequency setting parameter adjustable based on operating conditions. The controller dynamically modifies the frequency setting parameter according to the relationship between ON-time and OFF-time, allowing the system to adapt to different load conditions and prevent output voltage drops that would occur with fixed frequency settings.
Solution Approach 2:
The patent employs feedback control by monitoring the ON-time and OFF-time relationship and using this information to adjust the frequency setting parameter. The controller continuously compares the actual timing parameters against reference values and modifies the frequency setting parameter accordingly, creating a closed-loop control system that maintains output voltage stability.
2Device complexity
If the frequency setting parameter is fixed, then the circuit design is simple, but the ON-time cannot be properly modulated when OFF-time reaches minimum threshold
Solution Approach 1:
The patent transforms the static frequency setting parameter into a dynamic one that can be adjusted based on real-time operating conditions. This allows the system to expand its adaptability range without requiring a completely redesign of the circuit architecture, maintaining relative simplicity while enabling flexible ON-time modulation.
Solution Approach 2:
The patent changes the frequency setting parameter based on the relationship between ON-time and OFF-time. By modifying this key parameter dynamically, the system achieves expanded modulation capability without fundamentally changing the circuit structure, thus balancing complexity and versatility.
3Productivity
If the OFF-time is maintained at minimum threshold, then the switching frequency is maximized, but the output voltage becomes over-low and cannot be maintained at preset level
Solution Approach 1:
The patent dynamically adjusts the frequency setting parameter to optimize the balance between switching frequency and output voltage. Instead of maintaining a fixed maximum frequency, the system adaptively modifies the frequency setting parameter based on the ON-time and OFF-time relationship, allowing it to prioritize output voltage maintenance when necessary while still achieving high switching frequencies under appropriate conditions.
Data Source
AI summary
A constant frequency ON-time control system applied to a voltage regulator is disclosed. The voltage regulator determines a time length of an input voltage inputted thereto according to an ON-time and thereby regulates an output voltage. The constant frequency ON-time control system includes a constant frequency ON-time control circuit for computing the ON-time according to a system duty cycle of the voltage regulator and a frequency setting parameter and a frequency setting parameter adjusting circuit for generating a frequency setting parameter adjust value according to an OFF-time corresponding to the ON-time and taking a result of operation between the frequency setting parameter adjust value and a preset frequency setting parameter as the frequency setting parameter. The frequency setting parameter adjusting circuit uses the frequency setting parameter adjust value to change the result of operation for varying the frequency setting parameter when the OFF-time is shorter than a reference value.