Artificial Ramp Generation in PWM Modulator for SMPS
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Solution Overview
Problem
Switched-mode power supplies (SMPS) face challenges in achieving low ripple voltage output, require complex saw-tooth generators, are sensitive to noise and spikes, and are costly, especially for mobile electronic devices.
Innovation Solution
A method and circuit for artificial ramp signal generation in current mode control SMPS using a current sensing circuit, current amplifier, and PWM comparator, where a biasing pedestal current is subtracted from the output of the current amplifier, and artificial ramp signals are generated on a capacitor biased by a constant current source, allowing easy trimming and reduced noise susceptibility.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If conventional saw-tooth generators are used in SMPS, then the power supply can operate, but the circuit complexity increases and cost increases
Solution Approach 1:
The patent extracts the pedestal current component from the amplifier output and separates it using a current source, allowing the saw-tooth waveform to be generated without requiring complex dedicated saw-tooth generator circuits. This extraction principle simplifies the overall circuit while maintaining functionality.
Solution Approach 2:
The amplifier output is designed to serve multiple functions: it provides both the signal amplification and the saw-tooth waveform generation through the capacitor charging mechanism. This multi-functionality eliminates the need for separate saw-tooth generator circuits, reducing complexity and cost.
2Reliability
If conventional saw-tooth generators are used in SMPS, then the power supply can operate, but the cost increases
Solution Approach 1:
By extracting and separately managing the pedestal current component, the patent enables the use of simpler, lower-cost amplifier and capacitor components rather than requiring expensive dedicated saw-tooth generator circuits, thereby reducing manufacturing cost while maintaining operational reliability.
Solution Approach 2:
The patent employs simple, inexpensive components such as standard capacitors and current sources that can be easily manufactured and replaced, rather than complex expensive circuits, making the overall system more cost-effective for mobile electronic devices.
3Reliability
If conventional saw-tooth generators are used in SMPS, then the power supply can operate, but susceptibility to noise and spikes increases
Solution Approach 1:
The capacitor serves as an intermediary element that smooths the amplifier output by charging and discharging in a controlled manner. This intermediary component filters out noise and voltage spikes from the input, producing a clean saw-tooth waveform that is less susceptible to harmful electrical disturbances.
Solution Approach 2:
The capacitor is pre-charged through the current source to establish a stable voltage baseline before the comparison operation occurs. This beforehand cushioning effect protects the PWM comparator from noise and spikes that might otherwise interfere with the switching control, ensuring more reliable operation in electrically noisy environments.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enables low-complexity, cost-effective saw-tooth signal generation with reduced noise susceptibility, allowing for stable DC output voltage in SMPS, particularly suitable for mobile electronic devices.
Implementation Method 1
generating artificial ramp signals as a voltage on a capacitor biased by a constant current source
Implementation Method 2
a current sensing circuit, measuring a current through an inductor
Data Source
AI summary
Circuits and related methods for artificial ramp generation for pulse-width modulators (PWM) for current control mode switch mode power supplies (SMPS) are disclosed. The artificial ramp generation is separated from a current sensing part and allows easy trimming of both paths. Artificial ramp is generated as a voltage on a capacitor biased by constant current and placed between a voltage sensing node and an input of a PWM comparator. The circuit disclosed reduces circuit complexity and susceptibility to noise and spikes from the input voltage.