Sensorless CCM DCM Mode Detection in Power Converters
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Solution Overview
Problem
Switching power converters face challenges in accurately sensing the inductor current zero crossing point, leading to noise effects and power losses, especially at high switching frequencies, which require high-bandwidth and low-noise sensing circuitries, increasing cost and size, and are exacerbated by the need for additional hardware like ADCs in fully digital controllers.
Innovation Solution
A sensor-less control scheme using dual control loops that interpret the inductor current zero crossing from pulse-width modulation (PWM) duty cycle values, eliminating the need for current sensing and reducing power consumption, noise sensitivity, and component count by deriving the SR switch turn-off time from PWM duty cycle values.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If high-bandwidth low-noise sensing and comparator circuitry is used to detect inductor current zero crossing at high switching frequencies, then measurement precision is improved, but use of energy and device complexity increase
Solution Approach 1:
The patent extracts the zero crossing detection function from the current sensing circuitry and relocates it to the PWM controller. By using the PWM duty cycle information already available in the digital controller, the system eliminates the need for separate high-bandwidth current sensing and comparator circuitry, thereby reducing power consumption while maintaining detection accuracy.
Solution Approach 2:
The PWM controller is made multi-functional by enabling it to perform both PWM generation and zero crossing detection. The same PWM duty cycle values used for switch control are also utilized to determine zero crossing points, eliminating the need for dedicated sensing hardware and reducing overall system power consumption.
2Measurement precision
If high-bandwidth low-noise sensing and comparator circuitry is used to detect inductor current zero crossing, then measurement precision is improved, but device complexity and cost increase
Solution Approach 1:
The patent merges the zero crossing detection function with the existing PWM controller. By combining these functions in a single digital controller unit, the system eliminates separate sensing circuits, comparators, and associated analog-to-digital conversion hardware, thereby reducing device complexity and component count.
Solution Approach 2:
Instead of directly sensing the analog current waveform, the system uses a digital copy of the current information embedded in the PWM duty cycle values. This digital representation is processed by the PWM controller to detect zero crossing points, eliminating the need for complex analog sensing circuitry.
3Measurement precision
If additional ADC hardware is added to fully digital controller for current sensing, then measurement precision is improved, but device complexity and power consumption increase
Solution Approach 1:
The patent extracts the current measurement information from the physical domain and represents it in the digital domain through PWM duty cycle values. By processing this digital representation within the existing PWM controller, the system eliminates the need for additional ADC hardware while maintaining measurement precision.
4Productivity
If sensing circuitry operates at higher switching frequencies, then productivity is improved, but use of energy by stationary object increases
Solution Approach 1:
The patent replaces the analog sensing and comparison mechanism with a digital processing approach. By using the PWM controller to detect zero crossing points through digital duty cycle analysis, the system eliminates the power-hungry analog comparator circuitry that would need to operate at high switching frequencies, thereby reducing power loss while maintaining high productivity.
Data Source
AI summary
Generally, described herein are embodiments of control schemes for sensor-less operation and detection of CCM and DCM in a switching power converter. In one aspect, embodiments of a controller are described that utilize dual control loops and do not require sensing the inductor current or any current in the converter which eliminates or reduces the challenges and problems associated with current sensing. Advantages of embodiments of methods described herein become more significant when used in ultra high switching frequency converters since embodiments of the controller result in eliminating the need for high-speed low-noise current sensing circuitries, when used in on-chip integrated power converters where sensing accuracy may be a more significant issue compared to on-board power converters, and in power converters with paralleled modules since embodiments of the controller eliminate sensing circuitries in each of the modules.