Current-Mode DC/DC Converter with Correction Circuit for Fast Voltage Tracking
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Solution Overview
Problem
Current-mode controlled DC/DC converters have a suboptimal reaction speed to changes in reference voltage, limiting their ability to accurately track variations in output voltage, especially in applications like telecom systems where fast voltage modulation is required.
Innovation Solution
Incorporating a correction circuit that adds a correction signal to the control signal to represent the average inductor current, rather than just the peak current, allowing the control signal to better reflect the average current and improving the transfer function from the control signal to the average output current, thereby enhancing the converter's bandwidth and response speed.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If the control signal represents only the peak current through the inductor, then the switching control is simple, but the reaction speed to reference voltage changes is slow
Solution Approach 1:
The patent introduces a correction circuit as an intermediary component that processes the control signal by adding a correction signal representative of the average inductor current. This mediator transforms the peak-current-based control signal into a modified control signal that incorporates average current information, thereby improving the reaction speed to reference voltage changes without directly complicating the switching control logic
Solution Approach 2:
The patent changes the parameter representation in the control signal by adding a correction signal that represents the average inductor current. This parameter transformation converts the control signal from purely peak-current-based to a composite signal that includes both peak and average current characteristics, enabling faster response to reference voltage variations
2Measurement precision
If the control signal is used directly as the set level for peak current, then the control loop is simple, but the output voltage tracking of reference voltage variations is inaccurate
Solution Approach 1:
The patent implements a feedback mechanism where the correction circuit continuously monitors the control signal and adds a correction component based on the average inductor current. This feedback loop ensures that the modified control signal accurately reflects the actual current conditions, thereby improving output voltage tracking accuracy for reference voltage variations
Solution Approach 2:
The correction circuit acts as an intermediary between the controller and the switching element, processing the control signal to include average current information. This intermediary ensures accurate transmission of current state information, improving the precision of output voltage tracking without directly modifying the switching control structure
Data Source
AI summary
A current-mode controlled DC/DC converter receives an input voltage (Vb) and supplies an output voltage (Vo). A controllable switch (S1) is coupled to an inductor (L) to obtain a periodically varying inductor current (IL) through the inductor (L). A current-mode controller (1) compares (10) the output voltage (Vo) with a reference voltage (Ver) to Obtain an error signal (ER), and applies (11) a transfer function on the error signal (ER) to obtain a control signal (CO; CIO). A correction circuit (7) adds to the control signal (CO; ICO) a correction signal (ICR) representative for a difference between an original value of the control signal (CO; ICO) and an average value of the inductor current (IL) to obtain a modified control signal (MCO; IMC). A drive circuit (3, 4) compares (3) a sensed signal (SE) being representative for the inductor current (IL) with the modified control signal (MCO; ICO) to switch off (4) the controllable switch (S1) when a level of the sensed signal (SE) reaches a level of the modified control signal (MCO; ICO).