SIDAC Startup Circuit for Low-Loss Switched-Mode Power Supplies
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Solution Overview
Problem
Existing techniques for deriving startup current in switched-mode power converters result in substantial power losses during normal operation or require additional switches and gating to disconnect the startup current path.
Innovation Solution
A method using a SIDAC, a capacitor, and an inductor to derive low voltage from a higher voltage input, allowing for efficient transfer of energy to a second capacitor that supplies the startup current needs of the control IC in a switched-mode power converter.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If a resistive branch is used to derive startup current from high voltage input, then the control IC can be powered up, but substantial power losses occur during normal operation
Solution Approach 1:
The patent employs periodic action through the SIDAC breaker that operates in cyclic fashion: it remains off during normal operation to prevent power loss, then breaks over periodically when capacitor voltage reaches the breakover threshold to transfer energy to the output capacitor. This periodic breakdown and recovery cycle enables startup current derivation without continuous power loss during normal operation.
Solution Approach 2:
The patent extracts the startup current derivation function from the continuous power path by using a separate capacitive energy storage branch (C1-SIDAC-L-C2) that is disconnected during normal operation. The SIDAC breaker effectively extracts and isolates this auxiliary power derivation path, allowing it to operate independently without affecting the main power conversion efficiency.
2Loss of energy
If additional switches and gating are added to disconnect the startup current path, then power losses are reduced, but device complexity increases
Solution Approach 1:
The SIDAC breaker provides self-service by automatically turning on when its breakover voltage is reached and self-turning off when current drops below holding current, without requiring external gate control signals or additional switching components. This self-latching behavior eliminates the need for complex gating circuits while achieving the desired disconnection of the startup current path during normal operation.
Solution Approach 2:
The SIDAC breaker acts as an intermediary component between the input voltage source and the output capacitor, mediating the energy transfer in a controlled manner. It provides voltage breakdown mediation that automatically regulates the connection state based on voltage levels, replacing the need for active switch control while maintaining efficient power isolation during normal operation.
3Loss of energy
If a SIDAC, capacitor, and inductor are used to transfer energy, then power losses are minimized, but device complexity increases
Solution Approach 1:
The patent utilizes parameter changes in the SIDAC breaker's electrical characteristics - specifically its voltage-dependent resistance that transitions from high impedance (off state) to low impedance (on state) when breakover voltage is reached. This parameter change enables efficient energy transfer through the inductor and capacitor network without requiring additional control components, as the SIDAC's inherent electrical parameter variation provides the necessary switching function.
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 minimizes power losses by enabling a substantially lossless or resonant transfer of energy, improving the efficiency of the power converter system.
Implementation Method 1
energy from the said first capacitor is transferred through the said inductor to the said second capacitor in a substantially lossless or resonant manner
Implementation Method 2
The SIDAC turns on when its breakover voltage is reached
Data Source
AI summary
A system to deliver auxiliary or startup current at a low voltage side from a higher voltage input side is provided which comprises a SIDAC or voltage-breakover switch and an inductor to transfer energy from the high voltage input side to the low voltage side. The system further comprises capacitors at the high voltage input and low voltage sides. The SIDAC or voltage-breakover switch turns on when the voltage across it exceeds a specific value and initiates a current pulse through the inductor for transferring energy from the high voltage input side capacitor to the low voltage side. The voltage breakover rating of the SIDAC or voltage-breakover switch is selected to be in between the voltage levels of the high voltage input side and the low voltage side.