Hybrid Sensing for DC-DC Converters With Output LC Double-Pole Compensation
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Solution Overview
Problem
Switching DC-to-DC converters with a second LC filter connected to their output face challenges in achieving high control loop bandwidth and phase margin due to the introduction of a double pole, leading to poor transient response and potential oscillation, particularly in inverting buck-boost converters with unity feedback gain.
Innovation Solution
Hybrid sensing circuits that include transconductance amplifiers to generate signals proportional to local and remote output voltages, with a summing circuit to create a double-zero response that compensates for the double-pole introduced by the second LC filter, ensuring high bandwidth and phase margin.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If a second LC filter is connected to the output of a switching DC-to-DC converter, then output voltage ripple and noise are reduced, but control loop bandwidth and phase margin deteriorate due to double pole introduction
Solution Approach 1:
The patent introduces an intermediary sensing circuit that senses both local and remote output voltages and generates a compensated feedback signal. This intermediary circuit acts as a mediator between the second LC filter and the control loop, providing a feedback signal that accounts for the double pole effect without being directly affected by it, thereby maintaining control loop bandwidth while still benefiting from the ripple and noise reduction of the second LC filter
Solution Approach 2:
The patent changes the feedback parameter by using a hybrid sensing approach that combines local and remote voltage sensing with specific gain values. The sensing circuit is configured with gains that compensate for the frequency-dependent voltage division introduced by the second LC filter, effectively transforming the feedback signal parameters to counteract the double pole effect and maintain high control loop bandwidth
2Object-affected harmful factors
If a second LC filter is connected to the output of a switching DC-to-DC converter, then output voltage ripple and noise are reduced, but transient response deteriorates
Solution Approach 1:
The hybrid sensing circuit serves as an intermediary that provides accurate feedback during transient conditions. By sensing both local and remote voltages and combining them with appropriate gains, the circuit ensures that the control loop receives accurate information about the actual output voltage at the load, enabling fast transient response despite the presence of the second LC filter
3Device complexity
If unity feedback gain is used in an inverting buck-boost converter, then circuit simplicity is maintained, but control loop stability deteriorates when a second LC filter is present
Solution Approach 1:
The patent introduces a hybrid sensing circuit as an intermediary between the output and the feedback input. This intermediary circuit compensates for the double pole effect introduced by the second LC filter through its specific sensing and signal combination approach, maintaining control loop stability without requiring complex compensation networks or changing the basic unity feedback gain structure of the inverting buck-boost converter
Solution Approach 2:
The patent modifies the feedback signal parameters by using a hybrid sensing approach with specific gain values that account for the second LC filter's effect. This parameter change in the feedback signal allows the unity feedback gain structure to remain simple while achieving stable control loop operation with the second LC filter present
Data Source
AI summary
A hybrid sensing circuit for generating a control signal for controlling a switching direct-current-to-direct-current (DC-to-DC) converter where (i) the switching DC-to-DC converter includes a first inductor-capacitor (LC) filter and (ii) a second LC filter is electrically coupled between a local output node and a remote output node of the switching DC-to-DC converter. The hybrid sensing circuit includes (a) one or more first amplifiers configured to generate a first amplifier output signal proportional to a dynamic voltage at the local output node, (b) one or more second amplifiers configured to generate a second amplifier output signal proportional to a difference between (i) a desired output voltage of the switching DC-to-DC converter and (ii) an output voltage of the switching DC-to-DC converter at the remote output node, and (c) summing circuitry configured to generate a control signal based on a sum of the first and second amplifier output signals.