DCM Switching Power Converter Dead Time Compensation
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Solution Overview
Problem
Switching power converters with dead time experience reduced power factor due to deviations in average input current from being proportional to the input voltage, leading to inefficiencies in power delivery.
Innovation Solution
An improved DCM switching power converter that measures dead time duration and calculates a desired on-time duration based on baseline on-time and dead time, ensuring the average input current remains proportional to the input voltage, thereby enhancing the power factor by adjusting the switch control signal.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If dead time is inserted to reduce power loss in the switch, then power loss is reduced, but power factor deteriorates
Solution Approach 1:
The controller measures the dead time duration in advance during each switching cycle and uses this measurement to calculate the desired on-time duration for the next switching cycle. This preliminary measurement and calculation approach allows the system to proactively compensate for dead time effects, maintaining current proportionality and power factor while still benefiting from the power loss reduction provided by dead time insertion.
Solution Approach 2:
The system dynamically adjusts the on-time duration parameter based on the measured dead time duration. By changing the on-time parameter in response to dead time variations, the controller maintains the average input current proportionality to input voltage, thereby preserving power factor despite the presence of dead time. The adjustment follows the relationship: desired on-time = baseline on-time × √(1 + dead time/baseline on-time).
2Reliability
If dead time is inserted to allow switching at valley of ringing, then voltage ringing is managed, but average input current deviates from proportionality to input voltage
Solution Approach 1:
The controller implements a feedback mechanism where the dead time duration is measured during each switching cycle and this measurement feeds into the calculation of the desired on-time duration for the next cycle. This closed-loop feedback approach continuously compensates for dead time effects, ensuring that the average input current remains proportional to the input voltage while allowing the switch to operate at the valley of ringing for improved reliability.
3Ease of manufacture
If on-time is extended to compensate for dead time, then power factor is improved, but output voltage regulation becomes excessive
Solution Approach 1:
The system applies a controlled amount of on-time extension based on the measured dead time, using the relationship: desired on-time = baseline on-time × √(1 + dead time/baseline on-time). This partial compensation approach extends on-time just enough to counteract dead time effects on power factor, without excessive extension that would cause over-compensation and output voltage regulation issues. The square root relationship provides a moderated adjustment rather than a direct one-to-one compensation.
Data Source
AI summary
An improved discontinuous current mode (DCM) switching power converter that compensates for the effect of dead time. The dead time of the switching power converter is measured during a switching cycle and a baseline on-time for a switch of the switching power converter is determined. The dead time and baseline on-time are used in calculating the desired on-time of the switch during a subsequent switching cycle of the power converter. The desired switch on-time regulates the output voltage to a desired voltage level. The desired switch on-time also maintains the average input current to the power converter in proportion to the input voltage, thereby improving the power factor of the switching power.