Buck Converter Threshold Detection for Pulse Skipping Mode
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Designers of buck converters face challenges in detecting the optimal threshold for switching between continuous current mode (CCM) and discontinuous current mode (DCM) and implementing a fast method for switching back to CCM, especially when negative inductor currents are allowed or suppressed, and for different current or voltage control modes.
Innovation Solution
A method and apparatus that measure the average battery current to detect thresholds for entering and leaving DCM, using a current comparator to control high and low side switches, and monitoring the delay between current pulses to facilitate fast switching back to CCM, allowing for flexible operation in both pulse skipping and PWM modes.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the converter operates in continuous current mode (CCM) with PWM control, then the output voltage is stable and the current is continuous, but the efficiency decreases at low load currents due to unnecessary switching operations
Solution Approach 1:
The patent implements dynamic mode switching between CCM and DCM based on load conditions. The controller automatically transitions from PWM mode at high loads to pulse skipping mode at low loads, optimizing efficiency across the entire operating range while maintaining stable output voltage through adaptive control strategies
Solution Approach 2:
The patent changes the operating parameters by switching between different current modes (CCM/DCM) and control methods (PWM/pulse skipping). This parameter change allows the converter to adapt to varying load conditions, reducing switching losses at low loads while maintaining voltage stability through threshold-based mode transition detection
2Loss of energy
If the converter operates in discontinuous current mode (DCM) with pulse skipping control at low load currents, then the efficiency increases by reducing switching operations, but the output voltage ripple increases and current continuity is lost
Solution Approach 1:
The patent employs feedback mechanisms to monitor output voltage and inductor current, using this information to maintain stable operation in DCM. The controller adjusts switching thresholds and timing based on feedback signals, ensuring voltage stability even when operating in discontinuous mode with reduced switching operations
Solution Approach 2:
The patent dynamically adjusts the pulse skipping pattern and switching frequency in DCM to maintain output voltage stability. By adaptively controlling the on-time and off-time of switches based on load conditions and feedback, the system reduces switching losses while compensating for increased voltage ripple through real-time parameter adjustment
3Device complexity
If a fixed threshold is used for switching between CCM and DCM modes, then the control logic is simple, but the transition point cannot be optimized for different operating conditions and load ranges
Solution Approach 1:
The patent implements dynamic threshold adjustment for mode switching between CCM and DCM. Instead of using a fixed threshold, the switching point adapts based on operating conditions such as input voltage, output voltage, and load current. This dynamic approach optimizes the transition point for different operating ranges while the underlying control logic remains relatively simple through state-machine implementation
Solution Approach 2:
The patent creates a universal control mechanism that handles both CCM and DCM operations with a unified threshold detection approach. The same control structure and threshold comparison logic work across different operating conditions and load ranges, providing adaptability without significantly increasing device complexity through modular design
4Reliability
If the threshold for entering DCM is set low to maintain CCM longer, then output voltage stability is maintained, but switching losses increase at low load currents
Solution Approach 1:
The patent implements variable threshold parameters that change based on operating conditions. The threshold for entering DCM is not fixed but adapts according to input voltage, output voltage, and load current levels. This allows the system to maintain voltage stability through appropriate threshold selection while minimizing switching losses by transitioning to DCM at optimal points across different operating ranges
Data Source
Figure 1~2
Figure 3
Figure 4~5
AI summary
Circuits and methods to detect a threshold for entering and leaving a discontinuous current mode of a buck converter have been disclosed. A buck converter is switched to continuous mode if the filtered battery current has reached a defined threshold current Ithccm. In order to expedite the transition from DCM mode to CCM mode the time delay between two or more pulses of a current through an inductor is monitored and the buck converter is switched to CCM mode if this time delay is smaller than a defined threshold.