Pedestal Loop DC/DC Converter Feedback
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Current DC/DC power converters using current mode control face limitations in load and line transient responses, power supply rejection ratio, and are prone to instabilities due to complex implementation and lack of output voltage feedback, which restricts control loop design flexibility and gain bandwidth.
Innovation Solution
The introduction of a Pedestal loop with a high pass filter in the DC/DC power converter, which provides additional AC feedback, allowing for more flexible pole splitting with reduced complexity, enabling quicker response to output voltage transients and improved gain bandwidth by coupling between the output and inputs of the modulator circuit.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If current mode control is used in DC/DC power converter, then the complex poles associated with output LC filter are split and voltage loop design is simplified, but the implementation becomes complicated and the converter is susceptible to current mode instabilities
Solution Approach 1:
The patent introduces a second feedback loop (pedestal loop) that senses the output voltage and feeds it back to the modulator circuit inputs. This additional feedback path provides stability to the current mode control by compensating for output voltage variations, thereby resolving the instability issue while maintaining the pole-splitting benefit
Solution Approach 2:
The patent implements a nested feedback structure where the second feedback loop (pedestal loop) is embedded within the overall control system. The pedestal loop is coupled to the modulator circuit inputs, creating a nested configuration that provides internal stability without interfering with the external voltage loop functionality
2Device complexity
If current loop uses output current as feedback in front of modulator, then pole splitting is achieved, but zero information about output voltage is available for responding to output voltage disturbances
Solution Approach 1:
The patent makes the modulator circuit inputs receive multiple types of feedback signals: the primary current loop feedback and the secondary pedestal loop feedback that carries output voltage information. This multi-functionality allows the modulator to respond to both current and voltage disturbances, eliminating the information loss about output voltage
3Reliability
If unity gain bandwidth is made significantly smaller than switching frequency in current loop, then current mode instabilities are avoided, but gain bandwidth of voltage control loop is limited
Solution Approach 1:
The patent segments the feedback function into two separate loops: the current loop that maintains stability with limited bandwidth, and the pedestal loop that provides additional voltage feedback path. This segmentation allows the voltage control loop to achieve higher effective bandwidth and faster response without compromising the stability constraints of the current loop
Data Source
AI summary
The present document relates to a power converter configured to generate an output voltage at an output of the power converter. The power converter may comprise a power stage, a modulator circuit, ramp generator circuit, a first feedback circuit, and a second feedback circuit. The power stage may be coupled to the output of the power converter. The modulator circuit may comprise a first input and a second input, and an output of the modulator circuit may be coupled to the power stage. The ramp generator circuit may be configured to generate a ramp signal, and an output of the ramp generator circuit may be coupled to the first input of the modulator circuit. The first feedback loop may be coupled between the output of the power converter and the second input of the modulator circuit.