Input Voltage Estimation via Conduction Time Measurement
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Solution Overview
Problem
Conventional switched mode power converters face challenges in accurately estimating input voltage on the secondary side due to galvanic isolation, requiring indirect and often inaccurate methods, which can lead to inefficiencies and instability in output power regulation.
Innovation Solution
The implementation of an input voltage estimate circuit that measures the power switch conduction time and secondary conduction time using a timer control and input voltage calculator, leveraging the volt-second balance of the energy transfer element to estimate the input voltage, allowing for precise regulation of output power.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If galvanic isolation is used between primary and secondary sides, then safety and electrical isolation are improved, but input voltage measurement accuracy deteriorates
Solution Approach 1:
The patent uses the energy transfer element (transformer) as an intermediary to indirectly measure the input voltage. By measuring the primary conduction time (when the primary switch is on) and secondary conduction time (when the secondary rectifier conducts), the controller can calculate the input voltage through the relationship established by the transformer's volt-second balance, without requiring direct electrical contact with the primary side voltage.
2Device complexity
If indirect measurement methods are used for input voltage, then device complexity is reduced, but measurement precision deteriorates
Solution Approach 1:
The measurement system uses the power converter's own operational parameters (conduction times of switches and rectifiers) to determine the input voltage. The controller leverages timing information that is already generated during normal operation, combining it with stored transformer characteristics (turns ratio) to calculate input voltage, thereby achieving accurate measurement without adding separate measurement hardware.
3Measurement precision
If conduction times are directly measured using timer control, then measurement precision is improved, but device complexity increases
Solution Approach 1:
The timing measurement function is merged with the existing controller's digital processing capabilities. The controller uses its internal timing mechanisms to measure the duration of primary switch conduction and secondary rectifier conduction, integrating the measurement function into the control logic rather than requiring separate dedicated timing hardware.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
This approach enables accurate estimation and regulation of input voltage, improving the efficiency and stability of switched mode power converters by directly measuring conduction times and using the energy transfer element's characteristics, thus enhancing output power management.
Implementation Method 1
an energy transfer element having an input winding coupled to the power switch and an output winding coupled to the output rectifier
Data Source
AI summary
An input voltage estimate circuit for use in a power converter. The input voltage estimate circuit comprises a timer, which comprises a timer control circuit to generate a control signal in response to a request signal, a winding signal, and an output voltage signal. The control signal is coupled to transition to a first logic level in response to a request event in the request signal, and to transition to a second logic level in response to the winding signal falling below the output voltage signal. The timer comprises a primary conduction timer to generate a primary conduction time signal in response to the first logic level and the second logic level in the control signal and a secondary conduction timer to generate a secondary conduction time signal in response to the second logic level in the control signal and a second logic level in a second drive signal.