Voltage Doubler Circuit Layout to Prevent SCR Failure Overvoltage
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Solution Overview
Problem
Conventional voltage doubling circuits face safety concerns due to the risk of overvoltage in the storage capacitor when the silicon controlled rectifier (SCR) fails, which can lead to unsafe conditions, especially when the doubled voltage exceeds the rating of the storage capacitor.
Innovation Solution
A voltage doubling circuit design that includes a silicon controlled rectifier (SCR) and a control circuit to manage the flow of electricity during AC cycles, ensuring the non-polar charging capacitor is charged to a maximum voltage during the negative half-cycle and discharges into a polar storage capacitor during the positive half-cycle, preventing overvoltage in the storage capacitor even if the SCR fails.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Device complexity
If the SCR is used to control voltage doubling without additional protection, then the circuit complexity is reduced, but the storage capacitor may be over-voltaged when the SCR fails
Solution Approach 1:
The patent applies beforehand cushioning by incorporating a voltage clamp circuit and protection circuitry that are pre-configured to prevent overvoltage conditions before they can damage the storage capacitor. These protection mechanisms are built into the circuit architecture from the outset, ensuring that even if the SCR fails, the storage capacitor cannot exceed its rated voltage.
Solution Approach 2:
The patent uses an intermediary protection circuit between the SCR and the storage capacitor. This intermediary circuit includes voltage clamp elements and protection devices that mediate the voltage transmission, preventing direct overvoltage transmission to the storage capacitor while allowing normal voltage doubling operation.
2Reliability
If the storage capacitor is designed to handle higher voltage to account for SCR failure, then reliability is improved, but the capacitance value must be reduced to maintain energy storage requirements
Solution Approach 1:
The patent segments the voltage handling function by separating the voltage doubling function (performed by the SCR and charging capacitor) from the energy storage function (performed by the storage capacitor). The protection circuit acts as an additional segment that clamps the voltage, allowing the storage capacitor to be optimized for capacitance value without needing to accommodate potential overvoltage conditions.
Solution Approach 2:
The voltage clamp circuit serves as an intermediary that decouples the voltage stress from the storage capacitor. This allows the storage capacitor to be sized for optimal energy storage capacity rather than being constrained by potential overvoltage scenarios, as the clamp circuit intercepts and limits any excessive voltage before it reaches the capacitor.
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 design effectively prevents overvoltage in the storage capacitor, enhancing safety by ensuring the storage capacitor is charged to a predetermined voltage without exceeding its rating, even in the event of SCR failure, thereby providing reliable power to loads like strobe lights.
Implementation Method 1
a diode connected in series between the parallel combination and the first output terminal and configured to allow the flow of current from the capacitors to the first output terminal
Implementation Method 2
a silicon controlled rectifier (SCR) having a cathode coupled between the parallel combination and the diode, and an anode coupled to the negative terminal, and a control circuit having a first connection to the positive terminal, a second connection to the negative terminal, and a third connection to a gate of the SCR
Implementation Method 3
at least one non-polar charging capacitor forming a parallel combination, the parallel combination together being connected in series between the positive terminal and the first output terminal
Data Source
AI summary
A voltage doubling circuit including a silicon controlled rectifier (SCR) having a control circuit configured to charge a charging capacitor during a negative alternating current cycle, and including a storage capacitor that receives a voltage from the charging capacitor during a positive alternating current cycle, and by charging the storage capacitor from the charging capacitor when the SCR is off, the storage capacitor is prevented from exceeding its regulated voltage even if the SCR fails.