Switching Power Supply Control Circuit Voltage Ripple Reduction
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Solution Overview
Problem
Existing control methods for switching power supplies face challenges in controlling output voltage ripple and fluctuations, particularly when the output voltage is high and the voltage-dividing ratio is large, leading to increased hysteresis width and difficulty in maintaining stable output voltage.
Innovation Solution
A control circuit is designed with a comparator and a constant voltage source, where the comparator has input terminals connected to the output voltage and a reference voltage, and a controller adjusts the switching element based on the comparator's output, incorporating a capacitive element and resistors to meet specific conditions that suppress output voltage fluctuations and allow rapid voltage stabilization.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Measurement precision
If hysteresis control is used with a comparator to control output voltage, then the output voltage can be regulated, but the output voltage ripple increases when the voltage-dividing ratio is large
Solution Approach 1:
A constant voltage source is introduced as an intermediary element connected to the inverting input terminal of the comparator. This constant voltage source acts as a mediator that references the output voltage fluctuations, effectively canceling out the amplified ripple that would otherwise appear at the comparator input due to the large voltage-dividing ratio. The constant voltage source provides a stable reference that compensates for the ripple, allowing precise output voltage regulation without excessive ripple amplification.
2Object-generated harmful factors
If the hysteresis width is decreased to reduce output voltage ripple, then the ripple is reduced, but the control becomes unstable due to noise
Solution Approach 1:
The constant voltage source serves as a noise-filtering intermediary by providing a stable reference voltage that is insensitive to high-frequency noise. This mediator allows the use of a smaller hysteresis width for reduced ripple while maintaining control stability, as the constant voltage source prevents noise from being amplified through the voltage-dividing network.
Solution Approach 2:
The comparator implements feedback control by continuously comparing the divided output voltage (with constant voltage source reference) against a reference voltage and adjusting the switching element accordingly. This feedback mechanism maintains control stability even with reduced hysteresis width, as the system can quickly respond to and correct for noise-induced deviations.
3Measurement precision
If a large voltage-dividing ratio is used to control high output voltage, then the output voltage can be regulated, but the output voltage fluctuations are amplified
Solution Approach 1:
The constant voltage source connected to the inverting input terminal acts as a mediator that references and cancels the amplified voltage fluctuations. By providing a stable reference voltage that tracks the output voltage changes, it prevents the fluctuations from being amplified by the voltage-dividing ratio, thereby maintaining precise output voltage control without excessive fluctuations.
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 effectively controls output voltage ripple and fluctuations, ensuring they fall within a desired range, and enables the output voltage to reach a target value quickly during activation, improving the stability and efficiency of the switching power supply.
Implementation Method 1
a comparator having a first input terminal that is connectable to a negative terminal of the constant voltage source and the comparator having a second input terminal that is connectable to a reference voltage source
Implementation Method 2
incorporating a capacitive element and resistors to meet specific conditions that suppress output voltage fluctuations
Implementation Method 3
a third resistor and a fourth resistor that voltage-divide an output voltage of the switching power supply
Data Source
AI summary
A control circuit according to an embodiment of the present invention is configured to control a switching element of a switching power supply. The control circuit includes a comparator having a first input terminal configured to receive an output voltage of the switching power supply. The comparator has a second input terminal that is connectable to a positive terminal of a reference voltage source. The comparator has an output. The output brings the reference voltage to a first voltage while the output signal takes a first voltage level. The output brings the reference voltage to a second voltage while the output signal takes a second voltage level. The constant voltage source has a positive terminal connected to a negative terminal of the reference voltage source and a ground of the comparator.