Inductor Current Shunt for DC-DC Regulator Load Dump Mitigation
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Solution Overview
Problem
Inductor-based DC-DC regulators face issues with positive voltage transients on the regulated output voltage due to the finite response time and combined effects of electrical series resistance (ESR) and electrical series inductance (ESL) in the output capacitor, leading to potential system shutdowns or overvoltage stress.
Innovation Solution
Incorporating a current shunt switch with an amplifier circuit coupled to its control node to divert inductor current away from the output capacitor when the output voltage exceeds a specified maximum, using a fast linear loop for smooth transitions and minimizing negative output voltage excursions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If the output capacitance is increased to reduce voltage transients, then the output voltage stability is improved, but the device complexity and cost increase
Solution Approach 1:
The patent introduces a current shunt switch as an intermediary component that provides an alternative current path during transient events. This mediator diverts inductor current away from the output capacitor when needed, reducing voltage transients without requiring increased capacitance. The shunt switch acts as a temporary current bypass, solving the stability problem while maintaining the original capacitor size and system complexity.
2Reliability
If a current shunt switch is added to divert inductor current, then the output voltage transient response is improved, but the device complexity increases
Solution Approach 1:
The patent implements a feedback control mechanism where the shunt switch is controlled by a control circuit that monitors the output voltage or inductor current. When a transient condition is detected, the feedback signal activates the shunt switch to divert current. This feedback-based approach automatically responds to transient conditions, improving reliability while keeping the control logic integrated and manageable, thus limiting the increase in device complexity.
3Productivity
If the switching response time is reduced to improve transient handling, then the productivity is improved, but the loss of energy increases due to switching losses
Solution Approach 1:
The patent employs preliminary action by pre-positioning the shunt switch in the circuit and pre-charging its control gate. When a transient event occurs, the shunt switch can be activated immediately without delay for charging or positioning. This preliminary preparation enables instant response to transients, improving productivity in transient handling while minimizing the duration of high-frequency switching, thereby reducing overall switching losses.
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 approach effectively reduces the amount and duration of negative output voltage excursions, improving the output voltage response to load transients without the need for increased output capacitance, thus preventing system shutdowns and overvoltage stress.
Implementation Method 1
an amplifier circuit and a comparator circuit, the amplifier circuit having an output coupled with the control node of the shunt switch, the comparator circuit to compare the output voltage to the specified maximum output voltage
Implementation Method 2
a shunt circuit coupled in parallel to the inductor, the shunt circuit to divert the inductor current away from the output node when the output voltage exceeds a specified maximum output voltage
Implementation Method 3
an inductor coupled with the switching circuit and configured to provide an inductor current to the output node
Data Source
AI summary
For inductor-based DC-DC converters, a current shunt switch can provide an alternate path for the inductor current to flow that does not include the output capacitor. An amplifier circuit can be included and coupled with a control node of the current shunt switch to adjust a voltage on the control node to control an amount of inductor current diverted away from the output node. A fast linear loop can be included to ensure smooth transitions when engaging or disengaging the current shunt switch. These techniques can minimize the amount and duration of the subsequent negative output voltage excursion, which can be dependent on the specific ESL and ESR values of the output voltage capacitor, for the cases when the final value of the step-down load-transient is not zero. These techniques can improve a positive output voltage response caused by an output load transient in the negative direction.