Switched Power Supply Charge Current Reduction
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Solution Overview
Problem
Existing DC-DC converters face inefficiencies and reduced maximum average power delivery due to unsteady output current and increased ripple when operating in current limit conditions, leading to sub-harmonics and power losses, especially in battery-equipped systems with unpredictable load requirements.
Innovation Solution
A synchronous switched power converter with a digital control circuitry that measures and controls input current, reducing the charge current when approaching the input current limit, thereby maintaining operation within normal mode and avoiding current limit conditions for a wider range of system load requirements.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the power converter operates in current limit conditions to protect against excessive current, then component protection is improved, but efficiency deteriorates and power losses increase
Solution Approach 1:
The control circuit proactively reduces the charge current when the input current approaches a predetermined threshold level, before the current limit condition is actually triggered. This preliminary action prevents the converter from entering the inefficient current limit mode while still protecting against excessive current, thereby maintaining high efficiency operation across a wider load range.
2Reliability
If the power converter operates in current limit conditions, then current protection is improved, but output current stability deteriorates and sub-harmonics increase
Solution Approach 1:
The control circuit takes preliminary action by detecting when the input current approaches the current limit threshold and proactively reduces the charge current accordingly. This prevents the converter from entering current limit mode where output current becomes unsteady and sub-harmonics are generated, thereby maintaining stable output current and clean waveform composition across varying load conditions.
3Loss of energy
If the charge current is reduced to avoid current limit conditions, then efficiency is improved, but the range of system load requirements that can be satisfied deteriorates
Solution Approach 1:
The control circuit dynamically adjusts the charge current based on real-time monitoring of the input current level. When the input current is below the threshold, the converter operates at full efficiency without unnecessary current reduction. When the input current approaches the threshold, the charge current is proportionally reduced to prevent entering current limit mode. This dynamic adaptation allows the converter to maintain high efficiency across a broader range of system load requirements while still meeting peak power demands when available input power is sufficient.
4Reliability
If cycle-by-cycle current limit is implemented to confine input current below target value, then current confinement is improved, but output duty cycle becomes unsteady and average power delivery deteriorates
Solution Approach 1:
Instead of allowing the current limit to trigger reactively and disrupt the output duty cycle, the control circuit takes preliminary action by reducing the charge current in advance when the input current approaches the target value. This proactive approach maintains steady output duty cycle operation and stable average power delivery to the load, while still effectively confining the input current below the maximum target value through predictive current management.
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 solution ensures the power converter stays out of current limit mode for the maximum possible range of system load requirements, maximizing efficiency, reducing output current sub-harmonics, and delivering the highest average current to the load without entering current limit conditions.
Implementation Method 1
They use a storage element device (an inductor) on which energy is alternatively stored and then delivered to a load
Implementation Method 2
At this purpose switches are used, whose ON and OFF states are defined by the high and low times of a usually fixed frequency digital control signal
Data Source
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Figure 2
Figure 3~4
AI summary
Circuits and methods for a switched power converter providing charge power for at least one battery and at the same time delivering current to operate an electronic device, wherein the converter is enabled to operate out of current limit mode, for the maximum possible range of system load requirements, have been achieved. The input current of the power converter is measured within each cycle-by-cycle, i.e. within each cycle of an external clock reference and the charge current is reduced if the input current exceeds a defined portion, e.g. 80% of the maximum allowable input current. The power converter may only enter current limited operation after the charge current has been already reduced to zero. Operating out of current limit mode ensures a maximum efficiency of the converter, maximize the current deliverable to a given load and minimizes subharmonics in the output current and voltage, thereby minimizing interference with other system component..