Power Supply Startup Circuit Transitioning to Zero-Voltage Switching
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Solution Overview
Problem
Existing power supply startup methods impose high stress on circuit devices and are inefficient, particularly due to the reliance on hard-switching methods that cause high di/dt values and voltage stress on output rectifier diodes, especially at higher input voltages.
Innovation Solution
Implementing a startup method that transitions from a hard-switching method to a zero-voltage switching (ZVS) method with peak current mode control, using a control module to determine the peak line voltage and center tap voltage, and initiating ZVS when the center tap voltage crosses a fraction of the peak line voltage, thereby reducing stress and increasing efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Speed
If hard-switching method is used during startup, then power supply can be initiated, but high di/dt values and voltage stress occur on output rectifier diodes
Solution Approach 1:
The system dynamically transitions from hard-switching method to zero-voltage switching method based on real-time detection of center tap voltage relative to peak line voltage. This dynamic adaptation allows the power supply to operate in hard-switching mode during initial startup for fast initiation, then automatically switch to ZVS mode when voltage conditions are met, thereby reducing voltage stress on rectifier diodes while maintaining startup speed.
Solution Approach 2:
The switching method changes based on voltage parameters. When the center tap voltage reaches a fraction of the peak line voltage, the system transitions from hard-switching to zero-voltage switching. This parameter-based transition optimizes the operating conditions to reduce stress on circuit devices while maintaining efficient power transfer.
2Power
If hard-switching method is used during startup, then power transfer can be established, but high di/dt values cause inefficiency and device stress
Solution Approach 1:
The system dynamically adapts the switching method based on startup progress. Initially, hard-switching establishes power transfer quickly, but once the center tap voltage reaches the threshold (fraction of peak line voltage), the system transitions to zero-voltage switching. This dynamic approach maintains power transfer capability while significantly reducing energy losses associated with high di/dt values.
Solution Approach 2:
The startup process utilizes the voltage buildup during hard-switching as a beneficial precursor. The hard-switching phase, which would normally cause excessive stress and losses, is intentionally used to establish initial voltage conditions, and once the center tap voltage reaches the threshold, the system transitions to ZVS mode that eliminates the harmful effects while maintaining power transfer.
3Measurement precision
If clamp voltage is directly regulated, then voltage control is achieved, but device complexity and cost increase
Solution Approach 1:
The clamp circuit automatically maintains appropriate voltage levels through the zero-voltage switching operation itself. The ZVS mechanism inherently limits voltage stress on the clamp circuit by ensuring switches turn on when drain-source voltage is near zero, eliminating the need for active voltage regulation of the clamp node. This self-regulating behavior reduces circuit complexity while maintaining voltage control precision.
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 increases the lifespan of circuit devices, reduces stress, and enhances efficiency by lowering di/dt values and eliminating the need for direct regulation of clamp voltage, while also reducing costs and improving power throughput.
Implementation Method 1
the clamp circuit comprising a first element that stores energy
Implementation Method 2
a transformer for isolating a primary side of the first stage from a secondary side of the first stage
Data Source
AI summary
An example apparatus may include a power supply circuit comprising a first stage, the first stage comprising a current-fed topology and a transformer for isolating a primary side of the first stage from a secondary side of the first stage; a control module configured to provide control signals to one or more switches of the power supply circuit and to perform startup operations comprising: determining a peak line voltage value of an AC input voltage to the power supply circuit; initiating, when the power supply circuit is started, a hard-switching method; determining a center tap voltage of the transformer; stopping the hard-switching method, when the center tap voltage crosses a fraction of the peak line voltage value; and initiating, when the hard-switching method stops, a zero-voltage switching method with peak current mode control.