Current Mode Control Modulator With Adjustable Ramp Signal
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Solution Overview
Problem
Current mode control schemes for voltage regulators face limitations due to signal range constraints, which impact system stability, gain, and dynamic performance, especially as supply voltages drop, leading to reduced performance and flexibility.
Innovation Solution
The implementation of a high-performance current mode pulse width modulation (PWM) regulator using a modulator that adjusts the signal range by synthesizing the inductor current and output voltage error, allowing for improved load transient response and increased noise tolerance through the use of transconductance amplifiers and hysteretic comparators.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If current mode control is used for voltage regulators, then control performance is improved, but signal range constraints worsen system stability and flexibility
Solution Approach 1:
The patent transforms the control approach by changing the parameter being controlled from direct current mode control to voltage mode control with a modified ramp signal. The ramp signal is adjusted to incorporate current mode control benefits while operating in a voltage control framework, allowing the system to achieve current mode performance without the associated signal range constraints. This parameter transformation enables the system to maintain flexibility across varying supply voltages.
2Use of energy by moving object
If supply voltage is reduced, then power consumption is lowered, but signal range constraints increase and reduce performance
Solution Approach 1:
The patent changes the control parameter from current-based to voltage-based control with a modified ramp signal that maintains effectiveness across different supply voltages. This allows the regulator to operate efficiently at lower supply voltages without suffering from the signal range constraints that plague traditional current mode control, thereby maintaining performance while reducing power consumption.
Solution Approach 2:
The patent implements a dynamic ramp signal that adapts to varying supply voltages and operating conditions. The ramp signal's characteristics are adjusted based on the operating point, allowing the controller to maintain optimal performance across a wide range of supply voltages, from low-power to high-performance modes, without being constrained by fixed signal range limitations.
3Adaptability or versatility
If gain is scaled to adjust signal range, then signal constraints are relaxed, but system stability and dynamic performance deteriorate
Solution Approach 1:
Instead of scaling gain to adjust signal range, the patent changes the fundamental control parameter from current to voltage with a modified ramp signal. This approach relaxes signal range constraints without requiring gain adjustments that would compromise stability. The voltage-based control framework with adaptive ramp signaling inherently maintains system stability while providing the necessary signal range flexibility.
Data Source
AI summary
A modulator for controlling a switch circuit of a voltage regulator, including a sense circuit that provides a current sense signal indicative of current through the output inductor, a ramp circuit that develops a ramp voltage on a ramp node using the current sense signal, an error circuit that develops an error signal indicative of output voltage error and that injects the error signal into the ramp node to adjust the ramp voltage, a comparator circuit that compares the ramp voltage with a fixed control voltage to develop a compare signal, and a logic circuit that uses the compare signal to develop a pulse control signal that controls the switch circuit. The output voltage error may be determined by comparing the output voltage with a reference voltage and converting the error voltage to a current applied to the ramp node.