Flyback Laser Diode Driver Supply With Shunt-Controlled Pulse Charging
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Solution Overview
Problem
Existing power supply systems for pulsed lasers and similar devices are inefficient due to high power losses when charging energy storage capacitors at high pulse repetition frequencies, leading to thermal dissipation issues and reduced efficiency.
Innovation Solution
A fly-back or boost stage transfers energy to the energy storage capacitor in a single event pulse, with real-time voltage measurement and shunt active device control to prevent overcharging and minimize losses, allowing for efficient recharging at MHz rates without dissipative series resistors.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Loss of energy
If a fixed voltage power supply is used to charge the energy storage capacitor, then the capacitor can be charged to the required voltage, but the efficiency is only 50% due to energy dissipation in the charging resistor
Solution Approach 1:
The patent employs periodic pulsed charging instead of continuous charging. The energy storage capacitor is charged in discrete pulses at the required voltage level, allowing the system to operate efficiently at high pulse repetition frequencies while minimizing energy loss during charging transitions.
Solution Approach 2:
The patent changes the charging voltage parameter dynamically. Instead of using a fixed voltage power supply, the system charges the capacitor to the specific required voltage level and then disconnects, avoiding continuous energy dissipation. The shunt transistor further adjusts the voltage parameter to maintain optimal charging conditions.
2Speed
If the charging voltage is increased to achieve fast risetime, then the pulse rise time improves, but the power loss in the switching device increases
Solution Approach 1:
The patent prepares the energy storage capacitor in advance by charging it to the required high voltage before the pulse is needed. This preliminary charging action ensures that when the pulse is generated, the capacitor can deliver the required fast rise time without requiring additional high voltage during the switching event, thereby reducing power loss in the switching device.
Solution Approach 2:
The patent introduces an energy storage capacitor as an intermediary between the power supply and the load. The capacitor acts as a buffer that stores energy at the required voltage level, allowing the power supply to operate at lower voltages while still achieving fast rise times through the pre-charged capacitor.
3Device complexity
If the energy storage capacitor is allowed to discharge into the power supply output, then the power supply can be simplified, but it causes ringing and other issues
Solution Approach 1:
The patent extracts the discharge path of the energy storage capacitor from the power supply output circuit. By providing a separate discharge path through the switching device and series inductance to the load, the capacitor can discharge without interacting with the power supply output, thereby eliminating ringing while maintaining a relatively simple power supply structure.
4Reliability
If a shunt transistor is used to prevent overcharging, then the capacitor is protected from damage, but additional power loss occurs in the shunt device
Solution Approach 1:
The patent implements feedback control through the shunt transistor to prevent overcharging of the energy storage capacitor. The transistor is activated when the capacitor reaches the required voltage level, providing negative feedback that stops further charging. This feedback mechanism protects the capacitor from damage while minimizing power loss by only activating the shunt path when necessary.
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 method enables high-efficiency recharging of energy storage capacitors at MHz rates, minimizing power losses and thermal dissipation, and maintaining a stable power supply output.
Implementation Method 1
An inductor is provided for storing energy to be transferred to the capacitor (1)
Implementation Method 2
providing a power supply for charging an energy storage capacitor (1); charging the energy storage capacitor with sufficient energy to fire the load (2)
Data Source
AI summary
A fly-back or boost stage transfers its stored energy to the energy storage capacitor of the fast driver discharge stage in a single event pulse. The charging voltage of a single flyback pulse on the capacitor is measured in real time and, if necessary, the charging current is diverted via a shunt active device or transistor, to ground, thus preventing the storage capacitor from overcharging with the risk of component damage. A series sense resistor is used to determine the presence and amount of the wasted shunt current in order that this current may be minimized by turning down the flyback energy, thus maximizing the overall efficiency.