SMPS VCC Resistor Layout for Lightning Surge Withstand
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Solution Overview
Problem
Switched-mode power supplies face insufficient withstand capability against lightning surges due to parasitic elements being activated by surge voltages, leading to unexpected currents and thermal disruptions.
Innovation Solution
Incorporating a first resistor element connected to the control chip's power source terminal to suppress currents through parasitic transistors, thereby stabilizing ground potential and preventing thermal disruptions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a capacitor is connected to the VCC terminal of the control IC, then power supply stability is improved, but the withstand capability against lightning surges deteriorates due to parasitic element activation
Solution Approach 1:
A resistor is introduced as an intermediary component between the capacitor and the VCC terminal. This resistor acts as a mediator that limits the surge current flowing through the capacitor during lightning surge events, preventing parasitic element activation while allowing the capacitor to maintain power supply stability during normal operation.
Solution Approach 2:
The resistor is pre-configured in the circuit to provide protective cushioning against future lightning surge events. By having this current-limiting component in place before any surge occurs, the circuit is prepared to withstand surge voltages without damage, while the capacitor continues to provide stable power supply.
2Ease of operation
If the control IC is directly connected to the power source, then ease of operation is improved, but thermal disruption risk increases due to unexpected currents from parasitic transistors
Solution Approach 1:
A resistor is inserted as an intermediary component between the power source and the control IC. This resistor serves as a protective mediator that limits current flow through parasitic transistors during surge events, preventing thermal disruptions while maintaining the simple direct connection topology for ease of operation.
Solution Approach 2:
The resistor provides preliminary protective action by being pre-positioned in the power supply path to counteract potential surge currents before they can cause thermal damage. This preemptive current limitation prevents parasitic transistor activation and subsequent thermal disruptions without complicating the overall circuit connection.
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
Enhances the power supply's resilience to surge voltages by reducing parasitic transistor currents and maintaining stable ground potential, thus preventing thermal breakdowns.
Implementation Method 1
a first resistor element arranged between a first terminal 101 and a first capacitor 131... suppress currents through parasitic transistors, thereby stabilizing ground potential
Implementation Method 2
a first capacitor 131 connected to a power source terminal VCC... stabilizing ground potential
Data Source
AI summary
There is provided a switched-mode power supply including a main transformer, a switching device which performs switching control of a main current flowing through the main transformer, a control chip which includes a first terminal and controls the switching device, a first capacitor connected to the first terminal of the control chip, and a first resistor element connected to the first terminal, in which the control chip includes a semiconductor substrate including a first connecting region connected to the first terminal, the first resistor element is arranged between the first connecting region and the first capacitor, and the first terminal is a power supply terminal to which power supply electric power is supplied.