Low-Gain Current-Mode Voltage Regulator Offset Cancellation
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Solution Overview
Problem
Low-gain current-mode voltage regulators suffer from output offset due to the ripple effect of the error and current sense signals, leading to an output voltage that is not equal to the reference voltage, especially in load transients.
Innovation Solution
An offset cancellation circuit is introduced to subtract the inputs of the PWM comparator, producing an offset signal that is filtered to remove AC components and injected into the error signal to cancel the output offset, effectively modifying the error signal to eliminate the offset.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If parallel-connected capacitors are used at the output to reduce voltage spike, then the voltage spike is reduced, but the volume, weight and cost of the voltage regulator increase
Solution Approach 1:
The patent extracts the harmful voltage spike from the output by introducing an offset cancellation circuit that actively removes the spike through signal processing, rather than passively absorbing it with large capacitors. The offset signal is detected and subtracted from the output, eliminating the need for bulky output capacitors.
Solution Approach 2:
The patent introduces an intermediary offset cancellation circuit between the PWM comparator and the output that actively compensates for voltage spikes. This circuit includes an offset detector and a subtractor that processes the output signal to remove spikes, serving as a mediator that eliminates the harmful effect without requiring large physical capacitors.
2Object-affected harmful factors
If parallel-connected capacitors are used at the output to reduce voltage spike, then the voltage spike is reduced, but the volume, weight and cost of the voltage regulator increase
Solution Approach 1:
The patent extracts the harmful voltage spike from the output by introducing an offset cancellation circuit that actively removes the spike through signal processing, rather than passively absorbing it with large capacitors. The offset signal is detected and subtracted from the output, eliminating the need for bulky output capacitors.
Solution Approach 2:
The patent introduces an intermediary offset cancellation circuit between the PWM comparator and the output that actively compensates for voltage spikes. This circuit includes an offset detector and a subtractor that processes the output signal to remove spikes, serving as a mediator that eliminates the harmful effect without requiring large physical capacitors.
3Device complexity
If low-gain error amplifier is used in current-mode voltage regulator, then the circuit complexity is reduced, but the output offset increases due to ripple effect
Solution Approach 1:
The patent implements a feedback mechanism where the output voltage is continuously monitored and compared with the reference voltage. The difference (offset) is detected and fed back to the PWM comparator through the offset cancellation circuit, creating a closed-loop system that automatically corrects the output offset without requiring a high-gain amplifier.
Solution Approach 2:
The patent introduces an intermediary offset cancellation circuit that includes a subtractor to remove the ripple-induced offset from the output. This intermediary component processes the error signal to eliminate the harmful ripple effect, maintaining output precision while keeping the error amplifier gain low.
Data Source
AI summary
In a low-gain current-mode voltage regulator having a PWM comparator in response to the varying output voltage and inductor current of the voltage regulator to produce a PWM signal to regulate the output voltage, an offset signal is derived from a subtraction between the inputs of the PWM comparator, and the offset signal is injected into the PWM comparator to cancel the output offset of the voltage regulator.