Digital CrCM Boost Converter Control for Fast Current Sensing
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Solution Overview
Problem
Conventional boost power converters face challenges in achieving high switching frequencies and effective over-current protection while operating in Critical Conduction Mode (CrCM), particularly in bridgeless totem-pole designs, due to limitations in current sensing and control loop delays.
Innovation Solution
A fully digital, discrete-time control system for bridgeless totem-pole boost converters that senses high-bandwidth, bidirectional inductor current using current-sense resistors and comparators, enabling CrCM operation with programmable DAC references and re-referencing techniques, and implements interleaving methods for phase control and current sharing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If conventional current sensing methods are used in CrCM boost converters, then the system structure is simple, but the switching frequency is limited and over-current protection is ineffective
Solution Approach 1:
The patent segments the current sensing function into per-switch current sensing, where each switch has its own current sense resistor and comparator. This segmentation enables high-frequency operation by providing dedicated high-bandwidth sensing paths for each switching node, resolving the contradiction between switching frequency and system complexity through functional decomposition
Solution Approach 2:
The patent replaces conventional analog current sensing with a fully digital discrete-time control system. Current sense resistors generate voltage signals that are processed by comparators and digital logic circuits, substituting traditional continuous analog control with digital sampling and processing. This substitution enables higher switching frequencies while maintaining manageable system complexity through digital signal processing
2Power
If CrCM mode operation is implemented with large peak inductor current, then output power is increased, but over-current conditions occur and require effective protection
Solution Approach 1:
The patent implements per-switch current sensing with comparators that continuously monitor inductor current and provide feedback signals. The digital control system uses this feedback to detect over-current conditions and adjust switching operations in real-time, enabling the system to operate at high power levels while maintaining reliability through active feedback control
Solution Approach 2:
The patent employs over-current protection thresholds that are predetermined and programmed into the digital control system. Before over-current damage can occur, the system compares sensed current against these pre-set thresholds and takes protective action, implementing preliminary protection measures that prevent equipment damage while allowing high peak currents for increased power output
3Volume of moving object
If bridgeless totem-pole design is used, then system size and cost are reduced, but control loop delays increase and current sensing becomes more difficult
Solution Approach 1:
The patent introduces per-switch current sense resistors and comparators as intermediary elements in the bridgeless totem-pole configuration. These intermediaries provide direct, high-bandwidth current sensing paths that bypass the limitations of conventional sensing methods, enabling accurate current measurement and fast control response despite the simplified bridgeless architecture
Solution Approach 2:
The patent transitions from conventional single-ended current sensing to bidirectional current sensing capability in the bridgeless totem-pole design. By sensing current in both directions and processing it through digital logic, the system overcomes the control loop delays inherent in bridgeless configurations, maintaining fast response times while achieving compact system size
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
The system achieves higher switching frequencies and effective over-current protection, ensuring inductor current reaches zero or negative values consistently, while maintaining efficient power factor correction and reducing system size and cost.
Implementation Method 1
An apparatus to sense high bandwidth bidirectional inductor current in a totem-pole converter using current-sense resistor based per-switch, current-sensing
Data Source
AI summary
A method of setting a synchronous rectifier on-time value includes determining that a time interval has occurred, receiving a number of triangular current mode (TCM) pulses measured during the time interval, and determining a pulse comparison value equal to a number of switching period pulses during the time interval minus the number of TCM pulses during the time interval. The method also includes increasing the synchronous rectifier on-time if the pulse comparison value is greater than or equal to a threshold and decreasing the synchronous rectifier on-time if the pulse comparison value is less than the threshold.