OEM Tech NBU-1508 Thyristor Based Discharge Circuit User Manual
rev 1.07 / 2025 01 22
NBU-1508 thyristor-based discharge circuit
User manual
| Warning! This equipment may be dangerous. Please read the entire user manual carefully before using the product. |
Overview / Appearance
The NBU-1508 discharge circuit is designed for simplification of solid-state laser systems development. The module utilizes complete discharge of a relatively small capacitor bank (a typical value is 100uF), which, together with an external inductor, forms short (tens to hundreds of microseconds) bell-shaped pulses on a flashlamp. The NBU-1508 includes a thyristor, its driver, protective circuits, simmer and trigger circuits and controls. Typical applications are Q-switched Nd:YAG lasers or similar.
It’s important to emphasize that the NBU-1508 is not a stand-alone solution. It requires a capacitor charging power supply, an external inductor and capacitor bank, as well as some minor parts and controls to operate properly.
By default the NBU-1508 includes capabilities both for serial and external triggering (See Triggering section for details). Simplified as well as more complicated modifications are available on request.
An important feature of the NBU-1508 is clear and visible separation between low voltage and high voltage parts. The 24V power input and all interface circuits (SIM and PWF) are separated from the high voltage circuits by 4mm creepage distances and solid insulation to 2500VAC test voltage (1 MOOP/MOPP).
Cooling
Module is cooled with a built-in fan.
No external cooling is required.
Contents of delivery
By default, the delivery package contains the NBU-1508 module only.
The following standardized set of cables can be purchased optionally:
- Flashlamp connection cable – 2pcs (150cm each)
- Capacitor connection cable – 2pcs (30cm each)
- Inductor connection cable – 2pcs (30cm each)
- External trigger transformer connection cable with mounted 1:70 trigger transformer – 1pc (150cm)
- 24VDC cable – 1pc (50cm)
- SIM cable – 1pc (50cm)
- PWF cable – 1pc (50cm)
A DR cable and a discharge resistor itself can not usually be supplied. Customized delivery content is available on request.
Connections, signals, signal descriptions
INDUCTOR CONNECTION: Two M5 terminals
L1, L2 – to the inductor (polarity is not important)
FLASHLAMP CONNECTION: Two M5 terminals
LAMP+ – to the flashlamp anode
LAMP– – to the flashlamp cathode
CAPACITOR BANK CONNECTION: Two M5 terminals
C+ – to the capacitor bank positive
C– – to the capacitor bank negative
CAPACITOR CHARGER CONNECTION CONSIDERATIONS
| Note: we recommend connecting the capacitor charging power supply not to the C+/C– terminals, but directly to the capacitor bank. |
EXT (TO THE TRIGGER TRANSFORMER): Molex 39-30-1020
By default, the NBU-1508 supports both serial and external methods of triggering. To use the NBU-1508 for external triggering, a trigger transformer should be connected to the EXT connector. If the EXT connector is left unconnected, the NBU-1508 automatically recognizes this and applies pulses of serial triggering to the LAMP– flashlamp connection (see also Triggering section for details).
DR (TO DISCHARGE RESISTORS): Molex 39-30-1020
We suggest using the NBU-1508 with discharge resistors of your choice. The resistance and the power rating of discharge resistors must be selected accordingly to your application. Real operating voltages, your capacitor bank capacitance and the required quick discharge time are the most important parameters affecting the choice. You are welcome to contact us for assistance.
24VDC (TO 24V DC POWER SUPPLY): Molex 39-30-1040
PWF (PULSE CONTROL): Molex 39-30-1040
PWF CIRCUITS:
SIM (SIMMER SUPPLY CONTROL): Molex 39-30-1040
SIM CIRCUITS:
LED:
There is the warning LED indicating that NBU-1508 circuits are under high voltage.
HV LED (red) – is ON when NBU-1508 circuits are under high voltage
GND: M4 THREAD
The module should be grounded using this thread.
Grounding should be carried out before the module is powered up.
Safety
Warning! This equipment produces high voltages that can be very dangerous. Be careful around the device.
- During operation all the protective covers of the equipment must be securely fixed in place and all electrical connections must be properly attached
- The NBU-1508 discharge circuit is designed to be installed inside a properly grounded metal enclosure. It is the user’s responsibility to ensure that personnel are prevented from accidentally contacting the NBU-1508, especially DR, L1/L2, C+/C–, LAMP+/LAMP– connectors and cables. Casual contact could be fatal!
- After shutdown, do not handle the capacitance load until it has been discharged. Use an appropriate meter to check for complete discharge.
- Disconnect the module from the DC power source before making or changing electrical or mechanical connections.
- Don’t remove protective covers! There are no user serviceable parts inside this equipment.
Operations
A typical start-up sequence of the NBU-1508 is given below:
- Connect your capacitor charging power supply, +24V DC power supply, the inductor, the capacitor and the flashlamp to the NBU-1508 module
- Set +5V voltage on PIN1 of PWF connector to switch off the capacitor bank discharging
| Warning! By default, the capacitor discharge is switched on. Be careful and always switch off capacitor discharging before turning on your capacitor charging module. Otherwise, it may lead to failure of discharge resistors used in the system. |
- Disable simmer supply (PIN3 of SIM connector)
- Apply +24V DC power to the module
- Enable your capacitor charging power supply (charging module).
As soon as charging module starts operation, capacitor is charged
- Enable simmer supply (set +5V on PIN3 of SIM connector)
- Wait a few seconds for Simmer Sensor. If it fails, shut down the system
- Disable the capacitor charging power supply prior to pulse
| Note: this is important to disable the capacitor charging power supply. Otherwise, the output current of working capacitor charging power supply won’t allow the thyristor to close after the flash. |
- Apply +5V TTL pulse to PIN3 of PWF connector. The rising edge of TTL pulse will initiate the discharge through the flashlamp. The discharge will stop automatically once the energy stored in the capacitor bank is emitted. Pulse length of TTL signal should be a little longer than the actual discharge time, which depends on the L, C and flashlamp parameters
- Enable the capacitor charging power supply after the pulse
- Repeat #8-#10
To power down NBU-1508 and discharge capacitor bank:
- Turn off or Disable your capacitor charging power supply (important!)
- Disable simmer supply
- Set 0V on PIN1 of PWF connector to switch on capacitor bank discharging. Wait for the complete discharge of capacitors.
| Warning! If the capacitor bank capacitance is enormously high, this might lead to the overheating of the discharge resistors used in the system. |
- Remove +24V DC power from the module.
Specifications
ELECTRICAL
| +24VDC INPUT: | |
| Voltage | +24V DC |
| Current consumption | 5A max, up to 10A peak |
| PULSE PARAMETERS: | |
| Max. voltage | 1500V (other on request) |
| Max. discharge current (depends on flashlamp impedance K0) | 1000A for pulse width < 1 ms 500A for pulse width > 1 ms (other on request) |
| Max. average power | 2000W (other on request) |
| Pulse width | Defined by L, C and flashlamp parameters |
| Max. rep. rate | 50Hz (up to 100Hz on request) |
| RECOMMENDED WIRES: | |
| For capacitor bank connections | FLEXI-2V or similar (>1000V rated voltage, >4mm2cross-section), short length (30cm recommended) |
| For flashlamp connections | For external triggering – FLEXI-2V or similar (>1000V rated voltage, >4mm2cross section) For serial triggering additional insulation (e.g. with silicone tubing) or spacing (e.g. with spiral bundle hose) of LAMP– wire is required |
| SIMMER PARAMETERS: | |
| Simmer current | 400mA (200-500mA on request) |
| Max output voltage | 300V |
| Max output power | 100W |
| Open circuit voltage | 1500V |
| FLASHLAMP TRIGGERING PARAMETERS: | |
| Trigger pulse width | ~1us |
| Restrike rate | A few Hertz (automatically adjusted) |
| EXTERNAL TRIGGERING: | |
| Pulse energy / trigger voltage | ~20mJ / 350V positive to the EXT connector (other on request) |
| Trigger transformer | External transformer (purchased separately) Recommended p/n ZS1324-24V LUL1(H) by |
| Excelitas Technologies (Digikey p/n ZS1324- 24VLUL1(H)-ND) | |
| SERIAL TRIGGERING: | |
| Pulse energy / trigger voltage | ~160mJ / 10kV negative to LAMP– (other on request) |
| Trigger transformer | Integrated transformer |
| Cooling | Forced air cooling with built-in fan |
| Safety | 1 MOOP/MOPP between high voltage and low voltage parts (4mm creepages / 2500VAC HiPot) |
| Protections | From overheating of internal components |
| ENVIRONMENT: | |
| Operation temperature | 0 … +40 °C |
| Storage temperature | -20 … +60 °C |
| Humidity | <90%, non-condensing |
MECHANICAL
| Size (LxWxH) | Approx. 217x177x64mm (see also the dimensional drawing below) |
| Weight | Approx. 2.0 kg (w/o cables) |
Dimensional drawing
How to order? / Options
By default, there is the only standard part number, namely NBU-1508.
The following options are available on request:
- Integrated current sensor
- High power / current / voltage thyristor with extended parameters
- Low power / current / voltage thyristor with reduced cost
- Digital RS-232 / RS-485 interface
- Modified cables
- Modified simmer and / or trigger parameters
Triggering (serial triggering, external triggering, triggering basics)
By default the NBU-1508 supports both serial and external methods of triggering.
To use the NBU-1508 for external triggering, a trigger transformer should be connected to the EXT connector.
Default parameters for external triggering are (other on request):
- 350V voltage (applied to EXT connector)
- ~20mJ energy
- Recommended transformer (sold separately) – 1:70 e.g. ZS1324-24V LUL1(H) by Excelitas Technologies (Digikey p/n ZS1324-24VLUL1(H)- ND)
If EXT connector is left unconnected, the NBU-1508 automatically recognizes this and applies serial triggering to the flashlamp.
Default parameters for serial triggering are (other on request):
- 10kV voltage (applied to LAMP–)
- ~160mJ energy
Documents / Resources
 | OEM Tech NBU-1508 Thyristor Based Discharge Circuit [pdf] User Manual NBU-1508 Thyristor Based Discharge Circuit, NBU-1508, Thyristor Based Discharge Circuit, Based Discharge Circuit, Discharge Circuit, Circuit |