DC-DC Converter Inductor Current Sensing Without Dead-Time Error
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Solution Overview
Problem
Existing methods for determining inductor current in switching regulators, such as buck and boost converters, are inaccurate due to measurement errors during switching dead times, especially at higher frequencies.
Innovation Solution
A method and apparatus that senses the current through either the high-side or low-side transistor during the switching on phase and uses a switched capacitor circuit to charge a capacitor, allowing for accurate determination of inductor current by measuring the average current through the transistor and applying it to the real duty cycle of the switching regulator.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If summation of high-side and low-side currents is used to determine output current, then output current measurement is achieved, but measurement accuracy deteriorates due to switching dead time errors
Solution Approach 1:
The patent extracts only the necessary current measurement information from the high-side transistor during its on-phase, rather than attempting to measure both high-side and low-side currents and sum them. By taking out only the essential measurement component (high-side current during on-phase) and using duty cycle information, the method eliminates the problematic low-side current measurement during dead time, thereby resolving the accuracy-reliability contradiction
Solution Approach 2:
The patent introduces the duty cycle as an intermediary parameter to bridge the gap between the easily measurable high-side current and the desired accurate output current determination. Instead of directly measuring problematic low-side current during dead time, the method uses duty cycle information as a mediator to calculate the relationship between high-side current and output current, eliminating direct measurement during unreliable dead time periods
2Productivity
If switching frequency is increased to improve productivity, then converter output power increases, but measurement error increases due to dead time effects
Solution Approach 1:
The patent converts the harmful effect of dead time into a beneficial measurement approach by recognizing that during the high-side transistor's on-phase (which occurs outside dead time), the current measurement is accurate. By focusing measurement only on this reliable window and using duty cycle information to scale the measurement, the method transforms the constraint of dead time into a clear definition of when to take measurements, allowing high switching frequencies to be used without proportionally increasing measurement errors
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
Accurately determines the inductor current by sensing the transistor current during the on phase and using the real duty cycle, reducing measurement errors and improving accuracy across various switching frequencies.
Implementation Method 1
a first capacitor; a first switch configured to selectively charge the first capacitor in response to the current sense signal only during the switching on phase
Data Source
AI summary
A switching regulator circuit has a switching transistor actuated during a switching on phase of a duty cycle. The current flowing through an inductor of the switching regulator circuit is determined from sensing a transistor current flowing through the switching transistor during switching on phase and selectively charging a capacitor of a switched capacitor circuit dependent on a current sense signal during the switching on phase.