Power Converter Negative Current Sensing Low Quiescent Consumption
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Solution Overview
Problem
Existing DC-DC current mode power converters face challenges in efficiently sensing and controlling negative currents, leading to significant power dissipation due to class A biasing, which results in high quiescent current consumption even at zero load.
Innovation Solution
The implementation of push-pull class B or AB current sensing using operational transconductance amplifiers dynamically biased with error information allows for efficient sensing of both positive and negative currents without the need for constant bias, enabling reduced quiescent current consumption and enhanced power supply rejection ratio.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If class A biasing is used to enable sensing of negative currents, then negative current sensing capability is improved, but quiescent current consumption increases significantly
Solution Approach 1:
The patent applies dynamic biasing where the bias current is adjusted based on the operating state. During negative current conditions, sufficient bias is provided to enable accurate sensing. During normal positive current operation, the bias current is reduced or eliminated, thereby reducing quiescent power consumption while maintaining negative current sensing capability when needed
Solution Approach 2:
The patent changes the bias current parameter dynamically based on the sensed current direction. The biasing scheme transitions from a fixed class A bias to a variable bias that adapts to the operating conditions, providing high bias current during negative current events and low or zero bias during normal operation, thus resolving the contradiction between sensing capability and power consumption
2Measurement precision
If bias current is increased to match maximum negative current, then negative current sensing accuracy is improved, but power dissipation in feedback loop increases
Solution Approach 1:
The bias current is made dynamic rather than static, being increased only during negative current events when sensing accuracy is critical, and reduced during normal operation when full bias current is not needed, thus achieving high measurement precision during critical moments without continuous energy loss
Solution Approach 2:
The high bias current is applied periodically or event-driven during negative current conditions rather than continuously, allowing the system to achieve accurate measurement precision during negative current events while minimizing average power dissipation through intermittent high-bias operation
Data Source
AI summary
DC-DC current mode switching power converters that have negative current capability are presented. The power converters comprise: an output node, a pass device connected to the output node of the power converter, the pass device being configured to operate in accordance with a PWM signal and to supply at least a portion of an output current of the power converter, a PWM comparator for generating the PWM signal for controlling operation of the pass device in accordance with a current conducted by the pass device and a difference between an output voltage of the power converter and a reference voltage. The converters have push pull class B (or AB) current sensing, dynamic biasing of a current sense amplifier using error information, and using operational transconductance amplifiers that are fed an error voltage. This results in a lower quiescent current at zero load.