DC-DC Converter Ripple Control via Dynamic Inductor Threshold
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Solution Overview
Problem
In PFM-type DC-DC converters, the ripple in the output voltage varies significantly with input voltage variations, affecting the reliability of electronic devices, especially as power supply voltages decrease.
Innovation Solution
A switching power supply device with a switching converter circuit, control circuit, and threshold value adjusting circuit that adjusts the threshold value based on the voltage difference between the input and output terminals to reduce ripple voltage variation, using a combination of voltage and current judging circuits and a control signal generating circuit to manage the switching states of the converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the voltage applied to the inductor is increased to handle larger input voltage differences, then the power conversion capability is improved, but the ripple voltage in the output increases
Solution Approach 1:
The patent applies dynamics by making the inductor current threshold value dynamic rather than fixed. The threshold value is adjusted according to the input voltage level, allowing the system to adapt to varying voltage conditions. When input voltage is high, the threshold is increased to prevent excessive current and ripple; when input voltage is low, the threshold is reduced to maintain proper operation. This dynamic adjustment resolves the contradiction between power conversion capability and ripple voltage control.
Solution Approach 2:
The patent changes the parameter of inductor current threshold value based on input voltage conditions. By monitoring the input voltage and adjusting the threshold parameter accordingly, the system optimizes the balance between power conversion efficiency and ripple voltage suppression. This parameter change approach allows the converter to handle different operating conditions without generating excessive ripple voltage.
2Use of energy by moving object
If the PFM method is used to reduce power consumption in standby mode, then energy efficiency is improved, but the ripple voltage control becomes difficult when input voltage varies
Solution Approach 1:
The patent implements feedback by continuously monitoring the inductor current and comparing it against the dynamically adjusted threshold value. The control circuit uses this feedback to determine when to switch the MOSFET on and off, maintaining proper operation under PFM mode. This feedback mechanism ensures that even though the switching frequency varies with load conditions, the ripple voltage remains controlled through adaptive threshold adjustment based on input voltage levels.
3Loss of energy
If the switching frequency is reduced in PFM mode to save power, then energy consumption is decreased, but the output voltage ripple increases with input voltage variations
Solution Approach 1:
The patent applies dynamics by adjusting the inductor current threshold value dynamically according to input voltage conditions. In PFM mode, when input voltage is high, the threshold is increased to compensate for the reduced switching frequency, preventing excessive current buildup and associated ripple voltage. This dynamic adaptation allows the system to maintain low power consumption while controlling ripple voltage across varying input conditions.
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
This solution effectively stabilizes the output voltage ripple, improving the reliability of electronic devices by adjusting the threshold value corresponding to the input-output voltage ratio, thereby maintaining consistent output voltage accuracy despite input voltage fluctuations.
Implementation Method 1
a switching converter circuit (10) which includes at least one inductor (L1) and alternately repeats a first state for storing the power input from an input terminal (Ti) in the inductor (L1) and a second state for discharging the power stored in the inductor (L1) to an output terminal (To)
Data Source
AI summary
The invention provides a switching power supply device that can restrain the variation in the ripple of the output voltage corresponding to the variation in the input voltage and a control device thereof. When output voltage Vout is higher than a target value, switching converter circuit 10 is set to a second state (a state of discharging the power stored in inductor L1 to terminal To). When output voltage Vout is lower than the target value, switching converter circuit 10 is set to a first state (a state of storing the power input from terminal Ti in inductor L1) for a prescribed period of time and is then returned to the second state. Also, when the current flowing through inductor L1 exceeds a threshold value, switching converter circuit 10 is set to the second state. In addition, the threshold value of the inductor current is adjusted corresponding to the ratio between input voltage Vin and output voltage Vout, so that the variation in the ripple of output voltage Vout occurring together with the variation in that ratio can be restrained.