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LDD-3000 Diode Driver Theory of Operation
(Refer to Figure 1)
The LDD-3000 laser diode driver was designed specifically for the OEM high
power CW laser diode systems. OEM power supplies for the laser diode industry
have the following requirements:
Safe laser diode operation
Broad range of control of output current
Safe rise/fall times
Compact size
Power factor correction to conform with CE requirements
Low conducted electromagnetic emissions
Low leakage for medical applications
Referring to the Figure 1, “LDD-3000 Laser Diode Power Supply” block diagram,
the following is a brief description of operation.
AC Input Power Circuitry
AC input power is processed through a line filter to reduce the conducted EMI to
an acceptable level. The LDD-3000 line filter has minimum capacitance to ground
to minimize leakage currents.
Power Factor Correction Boost Inverter
The rectified input power is next applied to power factor boost inverter. This
inverter boosts the input voltage to 400VDC. In the process of boosting the input
AC voltage, the input AC current is adjusted so that is always in phase with the
input AC voltage. Without this power factor correction circuit, the AC input
current would be delivered to the power supply in high amplitude, narrow spikes,
having a high harmonic content. With power factor correction, the non-50/60 Hz
harmonics are reduced to near zero. Since only the fundamental frequency is
now used to deliver power, the efficiency of the power supply is improved
considerably.
One problem with standard input power factor correction circuits is that a high
frequency switching circuit is placed across the line in the input side of the
traditional input capacitor filter. This circuit results in substantial switching noise
conducted to the line. Lumina Power employs a proprietary soft-switching boost
inverter which produces minimum switching noise, reduces switching losses, and
results in a smaller heat sink associated with the power factor circuit.
Zero Voltage Switching (ZVS) Inverter
The ZVS inverter and the output transformer are used to step the 400VDC bus
down to the appropriate output value. The ZVS inverter is the most modern high
frequency/low loss/low noise topology utilized in power electronics today.
Instead of running the inverter in a traditional PWM mode, the inverter is run in a
