Power Converter Current Control via High-Side Switch Skip State
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Solution Overview
Problem
Conventional chargers face significant sensing errors when controlling small charging currents, particularly during wake-up, trickle, or end-of-charge phases, due to offset issues in input current amplifiers, leading to inaccuracies up to 100%.
Innovation Solution
A power converter design that includes a high-side switch and a conduction path, controlled by a controller to adjust on and skip state durations based on a current reference, allowing precise control of output current through pulse width modulation and low-side switch enable signals, even at low current levels.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If conventional current sensing methods are used with input current amplifier, then charging current can be controlled during normal operation, but sensing error reaches up to 100% when controlling small charging currents due to amplifier offset
Solution Approach 1:
The charging process is segmented into different modes (normal charging mode and small current charging mode) based on the charging current magnitude. The controller switches between different control methods: using amplifier-based current sensing for normal currents and pulse width modulation with conduction path control for small currents, thereby avoiding the amplifier offset error in small current scenarios
Solution Approach 2:
The invention changes the control parameter from amplifier output voltage to pulse width modulation duty cycle. By controlling the conduction path on-state duration as a percentage of the switching period, the system achieves precise small current control without being affected by amplifier offset, since the control is based on time proportion rather than voltage measurement
2Productivity
If amplifier-based current sensing is used, then current control is effective for large currents, but the offset voltage causes significant error for small currents
Solution Approach 1:
The invention introduces a conduction path as an intermediary element between the power converter output and ground. By controlling the on-state duration of this conduction path through pulse width modulation, the system indirectly controls the output current without requiring precise voltage measurement, thus avoiding the amplifier offset problem while maintaining charging productivity
Data Source
AI summary
A power converter can include a high-side switch coupled to a power supply terminal and selectively coupled to ground via a conduction path. During an on state duration, the high-side switch can be enabled and the conduction path can be disabled. During an off state duration, the high-side switch can be disabled and the conduction path can be enabled. During a skip state duration, the high-side switch and the conduction path both can be disabled. A controller coupled to the high-side switch can control the on state duration and the skip state duration based on a current reference. The controller can further generate a first control signal for controlling the high-side switch and the conduction path according to the on state duration and the skip state duration, and adjust an output current of the power converter to the current reference according to the first control signal.