Active Variable Inductor Circuit for SMPS Ripple and Transients
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Solution Overview
Problem
Existing Switched-Mode Power Supplies (SMPS) face a trade-off between reducing output ripple and improving transient response, as increasing capacitance or inductance to reduce ripple compromises transient response, and vice versa.
Innovation Solution
Implementing an active inductor circuit with a Negative Inductance Circuit (NIC) that adjusts inductance value dynamically, increasing it during steady-state to reduce ripple and decreasing it during transients for faster response.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Object-affected harmful factors
If output capacitor capacitance is increased to reduce ripple, then output ripple is reduced, but transient response deteriorates and board space increases
Solution Approach 1:
The patent applies dynamics by making the inductance value variable rather than fixed. The inductor circuit changes its inductance based on operating conditions: higher inductance during steady-state to reduce ripple, and lower inductance during transients to improve response time. This dynamic adjustment resolves the contradiction between ripple reduction and transient response.
Solution Approach 2:
The patent changes the inductance parameter dynamically. By adjusting the inductance value according to the operating state (steady-state vs. transient), the system achieves both low ripple during normal operation and fast response during load changes, eliminating the need for large capacitors that would compromise transient performance.
2Object-affected harmful factors
If inductor inductance is increased to reduce ripple, then output ripple is reduced, but transient response deteriorates and device size increases
Solution Approach 1:
The patent makes the inductance dynamic rather than static. The inductor circuit automatically adjusts its inductance value based on whether the system is in steady-state or transient condition, achieving both ripple suppression and fast transient response without requiring a physically large inductor.
Solution Approach 2:
The inductance parameter is changed dynamically according to operating conditions. During steady-state, higher inductance reduces ripple; during transients, lower inductance enables faster response. This parameter adjustment eliminates the need for oversized inductors that would compromise transient performance.
3Object-affected harmful factors
If output capacitor size is increased to reduce ripple, then output ripple is reduced, but board space increases and cost increases
Solution Approach 1:
By making the inductance dynamic, the patent reduces the need for large output capacitors. The variable inductance provides ripple suppression during steady-state without requiring the capacitor size increases that would consume board space, thus resolving the contradiction between ripple reduction and miniaturization.
4Object-affected harmful factors
If inductor size is increased to reduce ripple, then output ripple is reduced, but device complexity and cost increase
Solution Approach 1:
The patent uses a dynamic inductance circuit that adjusts based on operating conditions rather than relying on a physically large inductor. This approach reduces ripple without proportionally increasing device complexity, as the dynamic adjustment is achieved through control circuitry rather than simply scaling up passive components.
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 active inductor circuit effectively reduces output ripple during steady-state conditions while enhancing transient response by adjusting inductance values, allowing for smaller capacitors and inductors, thus improving efficiency and performance.
Implementation Method 1
a negative inductance circuit (NIC) for use with a load having a positive inductance. The NIC generates a negative inductance that counteracts the positive inductance of the load
Implementation Method 2
The amount of negative inductance generated by the NIC can be adjusted to provide an increased transient response of the SMPS
Data Source
AI summary
A Switched-Mode Power Supply uses a primary winding of a transformer rather than an inductor. The secondary winding of the transformer is driven with a current generated by a negative inductance circuit. When the reverse current flows it can increase the equivalent inductance value of the primary windings. A steady-state detector activates a steady signal and closes a switch to turn on the reverse current from an op amp when the output voltage remains within predetermined limits, causing the inductance to increase thus reducing ripple during steady state. When an output transient occurs, the steady signal is deactivated and the switch opened to stop the current from flowing through the transformer secondary, reducing primary inductance to allow for current to flow faster to the output to suppress the transient. Resistor and capacitor networks around the op amp allow for tuning the inductance modulation.