Laser Diode Driving Power Supply Current Ripple Control
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Solution Overview
Problem
Conventional switching-mode LD-driving power supplies face issues with low machining speed due to energy not being fully consumed during transitions in current command values, leading to defects in workpieces and reduced productivity.
Innovation Solution
A laser diode-driving power supply with a constant current source and a control unit that compares current command values, applying a voltage less than the lasing threshold when the second current command value is lower, ensuring energy is consumed by the laser diodes during transitions, thereby controlling the LD drive current effectively.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If a conventional switching-mode LD-driving power supply uses a large inductance value smoothing reactor to reduce ripple current, then the ripple current is reduced, but the energy consumption in the closed circuit is insufficient, causing pulsed minute current to be superimposed on the LD drive current
Solution Approach 1:
The patent converts the harmful effect of stored energy in the smoothing reactor (which causes current superposition and machining defects) into a beneficial effect by controlling the switching element to create a controlled discharge path. The energy that would otherwise cause problems is now utilized to maintain current stability without superposition effects.
Solution Approach 2:
The control unit monitors the LD drive current and adjusts the switching element operation accordingly. When a second current command value lower than the first is input, the control unit detects the potential current superposition and activates the switching element to discharge the smoothing reactor energy, preventing the harmful current spike.
2Reliability
If a standby time is provided until the LD drive current decreases to a specified value, then the current accuracy is improved, but the machining conditions cannot be switched at high speed
Solution Approach 1:
The control unit predicts when a lower current command value will be input and preliminarily activates the switching element to discharge the smoothing reactor energy in advance. This preliminary action prevents current superposition before it occurs, eliminating the need for standby time and enabling high-speed machining condition switching.
Solution Approach 2:
The patent skips the traditional standby time period by actively managing the smoothing reactor discharge through the switching element. Instead of waiting passively for current to decay, the system actively rushes through the energy dissipation process, maintaining both current accuracy and high switching speed.
3Loss of energy
If the switching element is turned on during the period when current command value is zero, then the energy stored in the smoothing reactor flows back to the closed circuit, but the low resistance and low impedance of the closed circuit result in low energy consumption
Solution Approach 1:
The switching element acts as an intermediary between the smoothing reactor and the closed circuit. Instead of allowing direct energy flow through the low-impedance closed circuit (which causes low energy consumption and current superposition), the switching element mediates the energy discharge through a controlled path that achieves both energy dissipation and current stability.
Data Source
AI summary
A laser diode-driving power supply includes a constant current source that supplies current to LDs, a switching element connected in parallel to the LDs, and a control unit that controls the constant current source and performs on-off control of the switching element. The control unit compares a first current command value and a second current command value for controlling current output from the constant current source, and when the second current command value input after the first current command value is smaller than the first current command value, applies to the LDs a voltage in the range of a voltage at which current flows through the LDs to a voltage less than the lasing threshold of the LDs when there is no output from the LDs.