Switching Power Converter Ramp Signal Slope Adjustment
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Solution Overview
Problem
Constant ON-time switching power converter circuits face instability due to small parasitic resistance in output capacitors, leading to errors in output voltage regulation and compromised fast load response when trying to improve precision with high gain error amplifiers and additional ramp circuits.
Innovation Solution
A switching power converter circuit with a pulse width modulation circuit and a ramp signal generation circuit that adjusts the slope and amplitude of the ramp signal based on input and output voltages, using an error amplifier to generate an error amplified signal, which helps in maintaining high precision and fast load response by dynamically controlling the power switch's ON-time.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If a high gain error amplifier and additional ramp circuit are employed to increase output voltage precision, then the precision of the output voltage is improved, but the fast load response advantage of constant ON-time switching power converter circuit is sacrificed
Solution Approach 1:
The patent implements dynamic adjustment of the ramp signal slope based on the error amplified signal. The ramp signal generation circuit dynamically changes the slope according to the output voltage error, allowing the system to maintain both high precision (through error amplification) and fast load response (through adaptive slope adjustment that preserves constant ON-time characteristics).
Solution Approach 2:
The patent changes the parameter of the ramp signal (its slope) dynamically based on the error amplified signal. By adjusting the ramp signal slope rather than using a fixed high gain amplifier throughout, the system achieves high precision when needed while maintaining the fast response characteristics of constant ON-time control during transient conditions.
2Measurement precision
If a high gain error amplifier is used to reduce output voltage error, then the precision of the output voltage is improved, but the circuit complexity increases
Solution Approach 1:
The patent combines the error amplification function with the ramp signal generation function into a single integrated circuit. The error amplifier's output is directly used to control the ramp signal slope, merging two separate functions (error amplification and ramp generation) into one unified structure, thereby reducing overall circuit complexity while maintaining high precision.
Solution Approach 2:
The ramp signal generation circuit serves multiple functions: it generates the ramp signal for PWM comparison, dynamically adjusts its slope based on error conditions, and effectively replaces the need for separate high gain error amplifier and additional stability circuits. This multi-functionality reduces the total number of components needed.
3Stability of the object's composition
If additional ramp circuit is added to increase loop stability, then the loop stability is improved, but the device complexity increases
Solution Approach 1:
The patent merges the stability-enhancing ramp circuit functionality into the existing ramp signal generation path. By using the error amplifier output to dynamically control the ramp signal slope rather than adding a separate stability circuit, the system achieves improved loop stability without increasing device complexity.
Data Source
AI summary
A switching power converter circuit includes a power switch for operating an inductor to convert the input voltage to the output voltage to drive a load circuit; and a control circuit, including: a pulse width modulation circuit comparing an output related signal with a ramp signal to generate a pulse width modulation signal for controlling the power switch, wherein the output related signal is related to the output voltage; an error amplifier circuit generating an error amplified signal according to a difference between the output related signal and a reference signal; and a ramp signal generation circuit generating the ramp signal, wherein an amplitude of the ramp signal is determined according to the input voltage and the output voltage; and/or the slope of the ramp signal is determined according to the error amplified signal.