DC-DC Converter Ramp Offset Removal
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Solution Overview
Problem
Existing DC-DC switching converters face issues with peak-current limiting and phase balancing due to the offset introduced by the compensation ramp in peak-mode and valley-mode operations, leading to unbalanced phase currents and potential saturation in valley-mode phases.
Innovation Solution
The solution involves sampling the compensation ramp immediately before the high side device turns off in peak-mode and before the low side device turns off in valley-mode to generate an offset current equal and opposite to the sampled value, which is then added or subtracted during the next cycle to balance the effect of the compensation ramp, thereby removing the offset effect.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a compensation ramp is added to the control current to prevent sub-harmonic oscillation, then stability is improved, but an offset is introduced that shifts the actual peak current away from the control current value
Solution Approach 1:
The patent measures the actual peak current achieved after compensation ramp application and uses this measurement to generate a corrective offset signal. This feedback mechanism continuously adjusts the offset to compensate for the compensation ramp effect, thereby maintaining accurate peak current control while preserving stability.
Solution Approach 2:
The patent dynamically adjusts the offset parameter based on the measured peak current and compensation ramp characteristics. By changing the offset parameter in response to operating conditions, the system maintains accurate current control despite the presence of the compensation ramp.
2Stability of the object's composition
If the compensation ramp offset is not compensated, then phase currents become unbalanced in multi-phase converters, but adding complex compensation circuitry increases device complexity
Solution Approach 1:
The patent employs feedback to automatically measure and compensate for phase current imbalances caused by compensation ramps. Each phase's peak current is measured, and the necessary offset is automatically generated and applied, eliminating manual tuning and complex compensation circuitry while maintaining balanced phase currents.
Solution Approach 2:
The system performs self-compensation by automatically measuring its own peak currents and generating the necessary offset corrections without external intervention. This self-service approach simplifies the overall system by eliminating the need for complex external compensation circuits.
3Reliability
If peak current limiting is implemented by limiting the control current maximum value, then current protection is improved, but the compensation ramp offset causes the actual peak current to differ from the limited value
Solution Approach 1:
The patent measures the actual peak current after compensation ramp application and uses this feedback to adjust the control current limit. By continuously monitoring the relationship between control current and actual peak current, the system maintains accurate current protection while accounting for the compensation ramp offset.
Solution Approach 2:
The patent dynamically adjusts the current limit parameter based on the measured peak current and compensation ramp characteristics. This ensures that the actual peak current accurately reflects the intended limit value, maintaining both protection reliability and limit accuracy.
Data Source
AI summary
A DC-DC current-control mode switching converter is disclosed, with peak-mode control circuitry, configured to compare a coil current to a variable current limit, to turn off a high side device when the coil current exceeds the variable current limit. The DC-DC switching converter includes a compensation ramp generator, configured to provide a compensation ramp signal, and an offset circuit, configured to provide an offset current. The DC-DC switching converter further includes an amplifier, configured to generate a control current proportional to the difference between an output voltage and a target voltage, and an adder, to combine the control current, the compensation ramp signal, and the offset current. A DC-DC current-control mode switching converter, with valley-mode control circuitry, configured to compare a coil current to a variable current limit, to turn off a low side device when the coil current falls below the variable current limit, is also disclosed.