COT Control Circuit Frequency Locking for DC-DC Converters
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Solution Overview
Problem
Existing DC-DC converters with constant on-time (COT) control face challenges in flexibly changing their operating frequency due to the integration of resistors and capacitors in the on-time generator, limiting adaptability to different operation conditions.
Innovation Solution
A COT control circuit for DC-DC converters is introduced, comprising a synchronizing signal generator to produce frequency-modulated signals, an on-time generator that receives input and output voltage signals along with error signals to generate on-time signals for controlling switches, and a frequency locking circuit to compare and synchronize the frequency of on-time signals with synchronizing signals, allowing for adjustable operating frequencies.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the on-time generator uses integrated resistors and capacitors to generate on-time signals, then the control loop is simple and dynamic response is fast, but the operating frequency cannot be flexibly changed in different operation conditions
Solution Approach 1:
The patent implements a dynamic frequency adjustment mechanism where the operating frequency of the DC-DC converter can be flexibly changed according to different operation conditions. The on-time generator receives control signals that dynamically adjust the on-time period, enabling the switching frequency to adapt to varying load and input voltage conditions while maintaining COT control characteristics.
Solution Approach 2:
The patent changes the parameter of on-time period dynamically by introducing control signals that adjust the charging current of the timing capacitor in the on-time generator. This allows the operating frequency to be regulated without changing the fundamental COT control architecture, resolving the contradiction between simplicity and adaptability.
2Stability of the object's composition
If the DC-DC converter operates with variable frequency to regulate output voltage, then the control is simple, but the system stability is reduced
Solution Approach 1:
The patent incorporates a feedback mechanism where the on-time generator receives feedback signals representing input voltage and output voltage. This feedback allows the system to maintain stability by adjusting the on-time period based on actual operating conditions, ensuring regulated output voltage while preserving the simplicity of COT control.
Solution Approach 2:
The COT control circuit automatically adjusts its operation based on inherent feedback from the power stage, using the natural relationship between on-time, input voltage, and output voltage to maintain stability without requiring complex external control loops.
3Adaptability or versatility
If the on-time generator is integrated on a monolithic chip, then the device is compact, but it is hard to flexibly change the operating frequency in different operation conditions
Solution Approach 1:
The patent maintains integration by implementing frequency adjustment functionality within the on-time generator block itself, using localized control signals and components. This allows flexible frequency changing without requiring separate external circuits, preserving both compactness and adaptability.
Data Source
AI summary
A COT control circuit for DC-DC converter. The COT control circuit has a synchronizing signal generator, an on time generator and a frequency locking circuit. The synchronizing signal generator generates a synchronizing signal and a frequency-modulated signal. The on time generator receives an input voltage signal, an output voltage signal, an error signal and the frequency-modulated signal to generate an on time signal. The error signal is generated by the frequency locking circuit based on the on time signal and the synchronizing signal. The operation frequency of a steady state of the DC-DC converter is regulated through changing the value of the frequency-modulated signal.