Switched-Mode Power Supply Delay Matching for High-Frequency Linearity
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Solution Overview
Problem
Conventional switched mode power supplies operate at relatively low switching frequencies, which is not sufficient for high power efficiency and linearity required in envelope tracking applications, especially for wideband control signals like those in the 3GPP LTE standard.
Innovation Solution
A switched mode power supply design that includes a reactive element, a control signal generator producing two control signals, and a switching stage that alternates between charging and discharging the reactive element using different supply voltages. This design also incorporates a delay detector and an adjustable delay stage to ensure equal and short decoupling times, enhancing power efficiency and linearity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If the switching frequency is increased to meet wideband control signal requirements, then the power efficiency and linearity improve, but the dead time management becomes more difficult due to temperature and process variations
Solution Approach 1:
The patent implements a feedback mechanism where the second control signal is delayed based on the detected delay of the first control signal. The delay detector monitors the actual delay in the first control signal path, and the adjustable delay stage compensates by adding delay to the second control signal path, ensuring both signals arrive at the switching stage simultaneously despite temperature and process variations
Solution Approach 2:
The system uses its own control signals to detect and compensate for delays. The delay detector samples the first control signal and uses this information to automatically adjust the delay of the second control signal, making the system self-calibrating without external intervention
2Loss of energy
If the dead time is shortened to improve power efficiency, then the power efficiency improves, but the difficulty of implementation increases due to circuit delay variations
Solution Approach 1:
The patent makes the delay parameter dynamic rather than fixed. The adjustable delay stage changes the delay of the second control signal based on the detected delay of the first control signal, allowing the system to adapt to different operating conditions and minimize dead time while accounting for circuit variations
Solution Approach 2:
The system changes the delay parameter of the second control signal based on detected conditions. By adjusting the delay time dynamically, the system optimizes the dead time for power efficiency while compensating for manufacturing variations in circuit delays
3Manufacturing precision
If the switching frequency is increased to follow wideband control signals, then the linearity improves, but the requirement for precise switch timing becomes more critical
Solution Approach 1:
The patent introduces a delay detector and adjustable delay stage as intermediary components between the control signal generator and the switching stage. These intermediaries synchronize the control signals by detecting and compensating for path delays, enabling precise switch timing at high switching frequencies
Data Source
AI summary
A switched mode power supply comprises a control signal generator arranged to generate first and second control signals via first and second outputs, respectively, which are coupled to respective first and second inputs of a switching stage, by means of respective first and second control signal paths. The switching stage is arranged to, responsive to the first and second control signals, alternately charge and discharge the reactive element by coupling it alternately to first and second supply voltages. An adjustable delay stage in one of the first and second signal paths is arranged to control an adjustable delay so that a first delay experienced by the first control signal passing from the control signal generator's first output to the switching stage's first input is substantially equal to a second delay experienced by the second control signal passing from the control signal generator's second output to the switching stage's second input.