DC-DC Converter Ripple Cancellation via Emulation Compensation
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Solution Overview
Problem
Existing DC to DC converters experience unintended switching and undesirable output offsets due to undershoot in discontinuous conduction mode (DCM) and regulation point shifts in continuous conduction mode (CCM) caused by emulated inductor current circuits, leading to switching noise and multi-pulse issues.
Innovation Solution
The proposed solution involves a DC to DC converter with an inductor current emulation circuit that modifies emulated inductor current information based on output voltage and off-time, using a compensation circuit to reduce discharging current and cancel ripple voltage, thereby mitigating undershoot and regulation point offsets.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If emulated inductor current information is used for PWM control, then closed loop regulation is achieved, but undershoot and unintended switching occur in discontinuous conduction mode
Solution Approach 1:
The compensation circuit proactively generates a counteracting signal before the undershoot occurs. By detecting the switching state and generating a compensating voltage that opposes the expected undershoot, the circuit prevents the harmful effect rather than merely responding to it after occurrence.
Solution Approach 2:
A compensation circuit is introduced as an intermediary element between the emulated current signal and the PWM comparator. This intermediary generates a compensating signal that modifies the overall control signal, thereby eliminating the undershoot effect while preserving the beneficial regulation function.
2Measurement precision
If emulated inductor current circuit is used for regulation, then output voltage feedback is supplemented, but regulation point offset occurs in continuous conduction mode
Solution Approach 1:
The compensation circuit uses feedback from the switching state to dynamically adjust the emulated current signal. By continuously monitoring when switches are on or off and adjusting the compensation accordingly, the circuit maintains accurate regulation points without offset during continuous conduction mode operation.
Data Source
AI summary
DC to DC converters and pulse width modulation controllers are presented with compensation circuitry to mitigate discontinuous conduction mode (DCM) undershoot and continuous conduction mode offsets in inductor current emulation information by providing compensation signals proportional to the output voltage and the converter off time (Toff) when the low side converter switch is actuated.