Duty Cycle Estimation Circuit for Switch Mode Power Supply
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Solution Overview
Problem
Modern electronic devices face challenges in accurately sensing load current during discontinuous operation mode of switching voltage regulators, which affects battery power efficiency and runtime, as duty cycle information is not readily available in this mode.
Innovation Solution
A duty cycle estimation circuit that includes a latch circuit, a low pass filter, and a comparator to generate and refine a duty cycle estimate, allowing for accurate load current estimation and efficient transition between power modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Duration of action of moving object
If discontinuous operation mode is used to reduce power consumption, then battery runtime is extended, but load current sensing accuracy deteriorates due to unavailable duty cycle information
Solution Approach 1:
The patent introduces a duty cycle estimation circuit as an intermediary component that generates estimated duty cycle signals when actual duty cycle information is unavailable in discontinuous mode. This estimated duty cycle serves as a mediator to enable accurate load current sensing without requiring direct access to the actual duty cycle signal, thus resolving the contradiction between power savings and measurement accuracy.
Solution Approach 2:
The patent creates a copy of the duty cycle information through estimation circuits that replicate the essential characteristics of the actual duty cycle signal. By generating an estimated duty cycle copy, the system maintains load current sensing capability in discontinuous mode without requiring the original duty cycle signal, enabling accurate measurements while preserving power efficiency.
2Measurement precision
If duty cycle estimation circuit is added to enable load current sensing in discontinuous mode, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The duty cycle estimation circuit is designed to serve multiple functions: it provides duty cycle information for load current sensing, supports both continuous and discontinuous operation modes, and enables power mode transitions. This multi-functionality reduces the need for separate dedicated circuits for each function, thereby minimizing the increase in overall device complexity while achieving accurate measurement.
3Measurement precision
If continuous operation mode is used to maintain duty cycle information availability, then load current sensing accuracy is improved, but power consumption increases reducing battery runtime
Solution Approach 1:
The patent implements dynamic operation mode switching between continuous and discontinuous modes based on load conditions and duty cycle availability. The system dynamically transitions to discontinuous mode when appropriate to save power, while using the estimation circuit only when needed to maintain measurement accuracy, thus optimizing the balance between power consumption and sensing precision.
Data Source
AI summary
A duty cycle estimation circuit includes a latch circuit that receives a clock signal for a voltage regulator. The latch circuit outputs a duty cycle estimate. The duty cycle estimation circuit also includes a low pass filter coupled to an output of the latch circuit to receive the duty cycle estimate. The duty cycle estimation circuit further includes a comparator that receives, as input, an output of the low pass filter and a voltage regulator output. The comparator feeds back a feedback signal to the latch circuit.