DC-DC Converter RHPZ Compensation via Dual Feedback Path
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Solution Overview
Problem
DC/DC converters with a Right Half Plane Zero (RHPZ) in their transfer function face limitations in control loop performance, leading to poor transient responses and Power Supply Rejection Ratio (PSRR) due to the inability to compensate the RHPZ, resulting in slow converter performance.
Innovation Solution
A new feedback scheme is introduced that includes a second feedback path with a high pass filter and a buffer circuit, allowing the removal or compensation of the RHPZ, enabling the Unity Gain Frequency (UGF) to be pushed beyond the RHPZ frequency, thereby improving transient performance in boost, buck-boost, and inverting buck-boost converters.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the Unity Gain Frequency (UGF) is limited to frequencies much lower than the RHPZ frequency to maintain required phase margin, then the converter stability is improved, but the transient performance deteriorates and the converter becomes slow
Solution Approach 1:
A new feedback path is introduced as an intermediary mechanism that directly connects the output of the VCVS to the output of the boost power converter. This intermediate path provides a direct compensation mechanism for the RHPZ without requiring the main control loop to operate at limited frequencies, thus improving transient response while maintaining stability through the mediating feedback path
2Speed
If a new feedback path is added to compensate the RHPZ and improve transient performance, then the converter speed and transient response are improved, but the device complexity increases
Solution Approach 1:
The feedback system is segmented into two independent paths: the first feedback path that provides standard voltage feedback through the VCVS and power stage, and the second feedback path that provides direct RHPZ compensation. This segmentation allows each path to perform its specific function independently, improving transient response without significantly complicating the overall system architecture
Data Source
AI summary
The present document relates to a power converter configured to convert an input voltage at an input of the power converter into an output voltage at an output of the power converter. The power converter may comprise a power stage, a voltage controlled voltage source VCVS, a first feedback path and a second feedback path. The power stage may be coupled to the output of the power converter. The VCVS may be configured to generate, at an output of the VCVS, an error voltage by comparing a reference voltage with a feedback voltage indicative of the output voltage. The first feedback path may extend from the output of the power converter, via the VCVS, via the power stage, to the output of the power converter. The second feedback path may extend from the output of the VCVS to the output of the power converter.