QBY Series Pockels Cell Drivers

QBY-series Pockels cell drivers
User manual (preliminary)

rev 1.03 / 2023 07 18

Warning! This equipment produces high voltages that can be very dangerous. Please read user manual before starting operations.
Important note: please measure the output with symmetrical (differential) high voltage probe only. Measurement made with inappropriate equipment
is a common cause of driver’s failure.

Overview
QBY is a novel Pockels cell driver based on GaN transistors and producing high voltage pulses with high repetition rates, fast rise and fall times and adjustable pulse width and pulse amplitude. Main parameters are as below:
· Input ­ 24VDC · Output ­ bipolar pulses of high voltage · Pulse amplitude ­ adjustable up to 4000V (other on request) · Pulse width ­ adjustable from 10ns to 1000ns (other on request) · Rise and fall times ­ 3-4ns (also depend on load capacitance and pulse amplitude) · Maximal repetition rate ­ up to 1kHz @ 4kV with convective cooling and up to
10kHz @ 4kV with forced air cooling (and higher at smaller voltages)
At the moment QBY-series includes two models ­ QBY-4001 base model and QBY4010 enhanced model equipped with cooling fans, which made it possible to increase the maximal repetition rate up to 10kHz @ 4kV and up to 100kHz at smaller voltages.
Appearance
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Connections, signals, signal descriptions

TRIGGER 1 (J1) and TRIGGER 2 (J2): SMA (TE connectivity 5-1814400-2)
Trigger pulse inputs ­ 5 V TTL; input impedance 50 ; trailing edge is active; fast transition (<2ns) is highly recommended.
TRIGGER 1 trailing edge determines the beginning of HV pulse at driver’s output. TRIGGER 2 trailing edge determines the end of HV pulse at driver’s output.
Important note! TRIGGER 2 pulse must be applied at least 10ns later than TRIGGER 1 pulse. Simultaneous applying of TRIGGER 1 and TRIGGER 2 can
lead to driver’s failure.
INTERFACE (X2): Molex Micro-Fit (43045-0602)

PIN (color) 1 (red) 2 (black) 3 (black)

DESIGNATION

DESCRIPTION

+24VDC 24VDC RETURN

+24VDC power supply is to be connected here. Power consumption 0.5A max.

GND

Common ground of interface signals (Enable, Ready, Voltage Program).

3

4 (green)
5 (blue) 6 (orange)

Voltage Program
Enable Ready

Pin 3 is galvanically connected to Pin 2 (via inductor).

Analog signal 0-3V determining the amplitude of high voltage pulses at driver’s output.

Calibration table is given below:

UIN, VDC < 1.77 1.80 1.83 1.90 2.02 2.21 2.39 2.57 2.69 2.88 3.00

UOUT, kVDC 0.00 0.08 0.19 0.40 0.80 1.40 2.00 2.61 3.00 3.60 4.02

Turns driver’s output on and off.

5V TTL, 10 kOhm input impedance.

Output signal returning driver’s ready status (driver is enabled, there is no internal fault or overheating and driver is ready to work).

HV OUTPUT (X3): JST SM02B-BHSS-1-TB

PIN (color) 1 (red)
2 (red)

DESIGNATION
HV OUTPUT POSITIVE
HV OUTPUT NEGATIVE

DESCRIPTION
High voltage output of the driver.
HV OUTPUT POSITIVE varies from 0V to +2kV relative to the ground.
HV OUTPUT NEGATIVE varies from 0V to -2kV relative to the ground.
Voltage difference between HV OUTPUT POSITIVE and HV OUTPUT NEGATIVE varies from 0V to 4kV relative to the ground.

Mating part (JST BHSR-02VS-1) is supplied together with the driver.
Jumpers and LEDs
In stand-alone mode driver can be controlled manually without applying most of interface signals from the controlling device.

ENABLE JUMPER (X1)

ON (Pins 1 & 2)

Driver will be enabled only when Enable signal is applied to Pin 5 of INTERFACE connector.

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VOLTAGE PROGRAM JUMPER (X4)
VOLTAGE PROGRAM TRIMPOT (R131)

ON (Pins 2 & 3) OFF ON OFF
–

Driver is enabled.
Driver is permanently disabled.
Output voltage is determined by the state of VOLTAGE PROGRAM TRIMPOT (R131 on PCB).
Output voltage is determined by Voltage Program signal applied to Pin 4 of INTERFACE connector.
Determines the driver’s output voltage when VOLTAGE PROGRAM JUMPER (X4) is on. Clockwise rotation increases the output voltage.

There is an ENABLE LED onboard indication the driver is enabled and ready to deliver HV pulses to the output.
Grounding and mounting
Grounding All the driver’s circuits (HV OUTPUT central point, 24VDC negative, INTEFACE common ground and trigger pulse returns) are galvanically interconnected to each other, although some
via inductors.

Driver is to be mounted with four M3 screws.

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Operations (in stand-alone mode) 1. Connect 24VDC power supply, pulse generator and Pockels cell to the driver 2. Ensure that power is off and driver is disabled (i.e. ENABLE JUMPER X1 is removed) 3. Turn on 24VDC power supply 4. Set VOLTAGE PROGRAM JUMPER (X4) on, then set VOLTAGE PROGRAM TRIMPOT accordingly to the desired output voltage (minimal, maximal, other) 5. Short Pins 2 and 3 of ENABLE JUMPER (X1) to enable the driver 6. Turn on pulse generator and apply pulses to TRIGGER 1 and TRIGGER 2. Keep minimal distance between trigger pulses (10ns).
Typical output
Polarity of the output Please note, driver’s output is bipolar. HV OUTPUT positive has positive voltage potential
relative to the ground (from 0V to +2kV), HV OUTPUT negative has negative voltage potential relative to the ground (from 0V to -2kV), their difference varies from 0V to 4kV.
Examples of waveforms:
4kV, 10ns pulse
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4kV, 100ns pulse

4kV, 1000ns pulse

Typical performance

Table below contains maximal repetition rate in dependence on output voltage and cooling conditions. Other setup parameters ­ total load capacitance 5pF, ambient temperature 25C:

4.0kV

3.0kV

2.0kV

1.5kV

1.0kV <0.7kV

QBY-4001, conductive cooling

1kHz

5kHz

15kHz 25kHz 40kHz 50kHz

QBY-4010, forced air cooling

10kHz

15kHz

30kHz

40kHz

80kHz 100kHz

Higher load capacitance and higher ambient temperature result in derated performance.

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Specifications

ELECTRICAL SPECIFICATION

Input Power 24VDC, 0.5A max HV Output Output type/polarity Bipolar Amplitude 0-4kV adjustable (other on request) Pulse width 10-1000ns adjustable (other on
request) Repetition rate Load and cooling dependent
· >1kHz @ 4kV, 5pF for QBY-4001 · >10kHz @ 4kV, 5pF for QBY-4010
See also Performance section above Rise/fall time 3-4ns
Delay time <10ns Jitter <0.2ns
Load requirements Load type Capacitive
Load capacitance <5pF recommended, 10pF max Protections From overheating (~80C) Cooling QBY-4001: convective cooling or forced air cooling with external fan QBY-4010: forced air cooling with integrated fans
Environmental Operating temperature -30…+60C

MECHANICAL SPECIFICATION

Size (LxWxH)

80x50x20 mm3 (see also the dimensional drawings below)

Weight Approx. 0.05 kg

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DIMENSIONAL DRAWINGS
QBY-4001 (bare PCB without fans) QBY-4010 (enclosed PCB with fans)
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Bench-top version Bench-top version (QBY-BT) with embedded pulse generator is available.
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