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PPM awarded Investors in People – GOLD

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Investors in people gold logo

PPM is awarded Investors in People – GOLD

Pulse Power and Measurement Ltd (PPM) has been awarded the Investors in People Gold standard, joining the top 14% of accredited organisations across the UK who believe in realising the potential of their people. PPM was established in 1994 and employs 35 people. In 2014, PPM were awarded the investors in people silver award after the first assessment.

PPM’s Business Divisions

PPM Power – High voltage, pulse power and power electronics – www.ppmpower.co.uk

ViaLite Communications – RF over fibre equipment for communications – www.vialite.com

PPM Test – Electromagnetic compatibility (EMC) test equipment – www.ppmtest.com

PPM Systems – Antennas and RF systems for defence – www.ppmsystems.com

Business improvement through people management

Investors in People is the UK’s leading accreditation for business improvement through people management. “We’d like to congratulate PPM on their Gold standard”, said Paul Devoy, head of Investors in People. “Such a high level of accreditation is the sign of great people management practice and shows an organisation committed to being the very best it can be. ”

stuart-at-work qi-at-work

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Intelligent gate drivers for silicon carbide MOSFETs


One of the few disadvantages of SiC MOSFETs is that the technology requires careful consideration of the gate driver circuit. But, an intelligent gate driver can provide a lot more than just optimised switching performance…agile-switch-silicon-carbide-mosfet-gate-driver

Silicon carbide – better than silicon

Silicon Carbide (SiC) MOSFETs have a number of key benefits over Silicon IGBT’s for high power applications such as battery charging, traction drives, induction heating, renewable energy inverters and welding. Switching and static losses are lower.  Reverse recovery losses are almost nil. Also, there is relatively little change in loss as switching frequency is increased, resulting in efficient operation at hundreds of kHz.  Moreover, SiC does not exhibit deterioration of these parameters with temperature unlike IGBT’s, avoiding the need to derate the current specification for operation at higher temperatures. System level efficiency gains are therefore available for lower cooling needs, higher power density and reduced size and weight.

Gate driver circuit needs consideration

Careful consideration must be given to the gate driver circuit to optimise the performance of the device. However, an intelligent gate driver can provide more than just optimised switching performance:

  • Active clamping (augmented turn-off) means lower switching losses, better protection and reduced ringing.
  • Advanced fault detection means enhanced reliability and better diagnostics
  • Configurability enables design flexibility, voltage protection and master/slave paralleling

Active clamping (augmented turn-off)

Inserting one or more intermediate levels in the gate voltage between on and off reduces ringing, switching losses and inductance-induced overshoot voltages. In a short circuit condition, this also helps reduces stress on the component.


Augmented turn-off uses one or more intermediate voltage steps to reduce ringing, losses and overshoots.


The two plots above contrast a conventional gate drive solution with augmented turn off. The result is a reduction in Vce overshoot from 700v to 500v.

Advanced fault detection

Temperature and high voltage monitoring – An intelligent gate driver provides the isolation and functionality to support monitoring of temperature and the DC link voltage. Sophisticated monitoring means effective diagnostics and ultimately translates to improved reliability. For example, both under-voltage and over-voltage protection can shield a SiC MOSFET from voltages that would impact its long-term reliability by pulling the gate to Vgs.

Overcurrent protection – Silicon carbide MOSFETs have only a limited capability to withstand short circuits. Therefore, response time is critical. Augmented turn-off also plays an important role in controlling the aftermath of a short circuit because the MOSFET is being shut down in a high current condition.


Software settings – Every inverter design is unique. An intelligent gate driver enables configuration of settings for :

  • Augmented turn-off
  • Undervoltage and overvoltage lockout
  • Desaturation detection
  • Dead time
  • Fault lockout
  • Automatic reset

Drivers are also configurable for parameters such as overcurrent, blanking time and response time.

Intelligent master/slave paralleling – High frequency switching requires precise synchronisation of input triggers to avoid current imbalances. Master/slave technology allows the drive signal to be split locally at the power module, resulting in better performance and reliability due to reduced propagation delay. Plug and play connectivity to slave drivers enables easy use and significant cost savings.


One of the few downsides of silicon carbide is that the gate driver circuit needs careful consideration. However, using an intelligent gate driver brings significant additional benefits such as lower switching losses, longer lifetime and reduced ringing, as well as configurability advantages such as design flexibility, voltage protection and master/slave paralleling.

View AgileSwitch intelligent gate drivers

agile-switch-fuji-product-catalog-3-638 agile-switch-fuji-product-catalog-9-638agileswitch-logo__v_PPM Power square logo

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NY3 axial lead HV capacitors from Dean Technology

Dean Technology has announced the NY3 series of high voltage, class II, ceramic capacitors.   The new range features a unique axial egress lead arrangement that allows for a higher creepage distance than typical radial leaded parts. This makes them ideal for applications in air or other conditions with demanding dielectric requirements. Standard capacitors are available from 10,000 to 20,000 volts with capacitance up to 6,800pF. Custom versions are also available in many other configurations.  Dean supplies the NY3 series in two dielectric materials: Y5P and Y5U.  However, other temperature-rated ceramics are available in this type of package.

NY3 series components are available now from PPM Power.


Dean Technology, Inc. are based in Texas USA and manufacture high voltage components, assemblies and power supplies. The Dean Technology product lines includes HV Component Associates (HVCA), CKE, and High Voltage Power Solutions (HVPSI).

  • HVCA products include high voltage diodes, rectifiers, bridge rectifiers and ceramic disk capacitors.
  • CKE products include high power silicon rectifiers, MOVs and silicon carbide varistors.
  • HVPSI products includes high voltage power supplies, multipliers and test equipment.

HVCA, CKE and HVPSI product lines are available from PPM Power.

Dean square logo v2CKE logo square v4HVCA logo square v2

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Reasons you should be using PLECS for power electronics simulation


download-1    download download-2   

1. PLECS is designed specifically for power electronics engineers

PLECS is high-speed simulation software (plus optional hardware) designed specifically for engineers developing power electronics in a commercial environment.

2. PLECS is the best system-level simulation tool around

Other software packages may allow highly accurate modelling of individual elements, but in power electronics, understanding the interactions between system elements is critical to optimising performance. Early system level system testing can have a significant impact on the efficiency of a project as it allows more optimum definition of subsystems

3. You can use it from initial concept evaluation right through to hardware in the loop (HIL) testing.

The PLECS RT Box supports hardware in the loop (HIL). So, PLECS can be used to support a development project right the way through from initial concept evaluation, software in the loop (SIL) and processor in the loop (PIL) right the way through to testing real code on real hardware. This avoids the discontinuity and additional effort of using multiple platforms at different stages of the project.

4. PLECS is available as a standalone solution

The version of PLECS known as PLECS Standalone doesn’t require any other software. Moreoever, PLECS Standalone uses its own independent solvers which enable faster calculation.

5. A version of PLECS is available which integrates with MATLAB/Simulink

The version of PLECS known as PLECS Blockset integrates with MATLAB and its graphical user interface Simulink. This allows organisations already using MATLAB/Simulink to integrate PLECS with their existing work.

6. A huge library of components

PLECS includes a huge library of ideal and non-ideal components. In addition, new components can easily be created, either by modifying existing PLECS components or by combining multiple discrete components to create a more complex one.

7. You can model thermal, magnetic and mechanical as well as electrical performance.

No other software that allows system level modelling of thermal, magnetic and mechanical as well as electrical characteristics. In a practical context these aspects are critical to a successful development process.

8. You get a month’s trial for free

You can download the full software and trial it free for a month – just download one of the files on the PLECS downloads page and give PPM a call on 01793 784389. We’ll give you the key to start your free trial.



PLECS image



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Silicon carbide high voltage switches from Behlke

Robust and transient-proof, PPM can now supply silicon carbide, HV switches from German manufacturer Behlke.

The SiC range is in addition to the existing portfolio of low on-resistance HV variable switches based on Trench FET technology. The silicon carbide range has low dynamic switching losses and extremely low turn-on losses. In many cases the switches require no additional cooling due to the extremely low on-resistance. The on-time is controllable via a TTL signal and the units are robust with regards to overload and voltage reversal. These devices are ideal for industrial power applications and have excellent dv/dt immunity against high voltage transients.

Available features

  • Flange housing, tubular housing or standard DAP housing
  • Internal control unit
  • High current terminals
  • HV pig-tails, bus-bars or bolts.

Summary of electrical specifications

  • Max voltage range 6kV to 160kV
  • Peak currents from 150A to 6000A
  • On resistance from 0.02 to 5.44Ω
  • On-time from 120 to 250ns

Silicon Carbide versus Silicon

Silicon carbide(SiC) devices such as diodes, thyristors, MOSFETs, IGBTs and IGCTs offer better performance than standard silicon devices in nearly all relevant parameters. The energy required to excite electronics from the valence band across to the conduction band is much higher for silicon carbide than for silicon alone. Consequently, silicon carbide devices can tolerate far higher voltages and temperatures than equivalent silicon devices. Alternatively, SiC components with the same voltage rating can be made much smaller. Such a reduction in size means lower resistance, less thermal energy lost and higher efficiency. In short, silicon carbide is faster, smaller, more robust and more efficient. For power electronics, SiC promises higher power, high voltages and higher frequencies.


For more information see low on-resistance variable switches or call PPM on 01793 784389.

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15W floating DC-DC bipolar power supplies 1kV to 6kV – Ultravolt FLHV

Ultravolt FLHV 15W floating DC-DC bipolar power supply - feature image

PPM can now supply a new series of 15W enhanced floating hot-deck bipolar power supplies from Ultravolt.  The FLHV high voltage power supplies provide an output that can float on a high voltage bias supply up to 5 kV above or below the input ground reference. The units are available with 1kV, 2kV, 4kV and 6kV ratings.  The high input/output isolation supports floating electronics on high voltage. Notable performance characteristics include a high output stability of less than ±0.5% from no load to full load and accurate monitoring (±2.0%) of the floating bias supply output voltage and current.

Ultravolt FLHV 15W floating DC-DC bipolar power supply

Performance & Features

  • High output stability of less than ±0.5%
  • Accurate monitoring (±2.0%)
  • Excellent unit-to-unit repeatability
  • No pre-loading required
  • Reduced input current
  • Standard digital-ready, fully featured interface
  • Programmable output range on a fixed input
  • Standard enable/disable control pin

Example Applications

  • Electrostatic chucks (ESC)
  • Electron multipliers (CEM
  • Photo multiplier tubes (PMT)
  • HV bias (e-beam, i-beam, energy analyzers)
  • Gate supplies
  • Pulse generators
  • Amplifier rails
  • Other floating electronics

Product LayoutSchematic of FLHV series power supply

Product Range

Part Number Max. Power (W) Max. Voltage (V) Current (mA) Ripple (% rated V) Load Regulation (% rated V)
1FLHV24-BP15 15 Multiple outputs, see datasheet See datasheet 0.05 0.1
2FLHV24-BP15 15 Multiple outputs, see datasheet See datasheet 0.05 0.1
4FLHV24-BP15 15 Multiple outputs, see datasheet See datasheet 0.05 0.1
6FLHV24-BP15 15 Multiple outputs, see datasheet See datasheet 0.05 0.1



FLHV Series Datasheet

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4kV fast recovery diodes now on standard release

UFHV series - high current, medium voltage, fast recovery axial lead diodes

UFHV series - high current, medium voltage, fast recovery axial lead diodes

Dean Technology have announced that the UFHV series – high current, medium voltage, fast recovery axial lead diodes are now listed as standard parts because improvements in the manufacturing process have led to the series being made more economical to produce. As a result, Dean are able to increase availability. With current ratings ranging from 350 to 550 mA, the UFHV series is very flexible. Plus, a maximum reverse recovery time of 75ns and a maximum surge current of 30A represents exceptional performance versus cost – making them a very good value choice.

The compact DO-41 package is well-suited for small to medium power applications., including power supplies and multipliers found in instrumentation, plasma displays and electrophoresis applications. Available in 2kV/850mA ,3kV/825mA and 4kV/800mA versions, the diodes are available in bulk, tape+reel and ammo box packaging and is RoHS compliant. Delivery leadtime is typically from stock to 8 weeks. Please contact sales@ppm.co.uk for more information, pricing and samples.

  • UFHV series – high current, medium voltage, fast recovery
  • Available as 2kV, 3kV or 4kV max repetitive peak reverse voltage
  • Max reverse recovery time 75ns
  • Max surge current 30A
  • Max reverse current 5uA


Part number Max repetitive pk reverse voltage (V) Max forward voltage drop (V) Max average fwd current (mA) Max reverse current(A) Max surge current rating (A) Typ junction capacitance (pF) Max junction temp (°C) Max reverse recovery time (nS) Op. Temp (°C) L (in.) D (in.) d (in.) l (in.)
UFHV2K 2000 3 550 5 30 12 150 75 -55 to 150 0.2 0.1 0.034 1
UFHV3K 3000 4.1 400 5 30 8 150 75 -55 to 150 0.2 0.1 0.034 1
UFHV4K 4000 5.5 350 5 30 6 150 75 -55 to 150 0.2 0.1 0.034 1

For more information on other diodes supplied by PPM, please see the axial lead diodes product page or the high voltage diode / diode assemblies page.

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Using the programmable output pins on a Z+ power supply

The Z+ has two programmable output pins that can be controlled from the front panel or via a computer through the bundled graphical user interface over USB. These can be used to control isolation or polarity reversal relays, for example, without the need of a separate programmable logic controller (PLC). The programmable outputs are located on the rear of the units, with slightly different layouts for the low voltage (10V – 100V) and high voltage (160V – 650V) models.

Z+ pinouts

Pinouts for low voltage (left) and high voltage (right) models

TDK Lambda Z series GUI image

On the low voltage and high voltage models the programmable outputs are located at pins 1 and 6, with slightly different connectors on each model. Pin out diagrams are shown above. Internally the programmable outputs are controlled via open collector FETs each shunted by a 27V Zener diode. The outputs are rated to 25V maximum and can sink a maximum current of 100mA. These values should not be exceeded.

internal characteristics of Z programmable outputs

The internal characteristics of the programmable outputs

Combining programmable pins with relays

The programmable pins can be used in conjunction with relays to give additional functionality to the Z+ power supplies. Two useful examples are shown below

Z+ relay circuit example 1

Example showing the use of the programmable outputs and relays to switch between local and remote sensing.

Z+ relay circuit example 2

Example showing the use of the programmable outputs and relays to switch polarity at the load


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HV ceramic resistors now available as axial-leaded and slab types.

PPM can now supply high voltage ceramic resistors in axial leaded and slab types, manufactured by specialist Swedish manufacturer Kanthal.  The 500BA ceramic slab resistors and BA100 & 200 axial-leaded ceramic resistors extend a high voltage ceramic portfolio already including tubular, disk/washer and water cooled resistors.

Kanthal bulk ceramic resistorsHigh peak power and high energy

Both the axial leaded and slab types provide excellent performance where high peak power or high-energy pulses must be handled in a small size. The bulk construction produces an inherently non-inductive resistor and allows energy and power to be uniformly distributed through the entire resistor body. Therefore, there is no film or wire to fail. Maximum continuous operating temperature of both types is specified at 230°C. The standard dielectric coating is recommended for use in air, and the oil-resistant coating is recommended for use in oil. Custom designs are also available.

  • Axial leaded resistors available with peak voltage of up to 25kV and resistance values from 2ohms to 7.5Mohm.
  • Slab resistors can support a peak voltage of up to 65kV and range in resistance from 1ohm to 1.8Mohm.

More information on each range can be found on the ceramic resistors page.

Typical Applications

The 500BA series of ceramic slab resistors and BA100 & 200 series of axial-leaded ceramic resistors are ideal for applications such as:

  • DC Coupling and Filter Cap Discharge
  • Voltage Balancing
  • Pre-charge / Inrush Limit
  • Voltage Divider
  • Filter
  • Snubber
  • Crowbar
  • Measuring
  • EMI / EFI Test
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Choosing a high voltage switch

Due to advances in semiconductor technologies, solid-state switches can now substitute thyratrons, ignitrons, spark gaps and electromechanical high voltage relays. TTL control input and low power electronics replace expensive heater supplies and drivers found in older systems. A high voltage switch can be chosen that meets application, system or load type criteria such as voltage, current, frequency and on-time. However, some extra work is required to ensure optimal performance of the switch in the application.

High voltage switches are composed of an array of semiconductors controlled by a sophisticated trigger mechanism. Overvoltages and high peak currents can be destructive so care must be taken when choosing a switch to ensure that specification limits are never exceeded. Also, the high dV/dt and dI/dt created by switching events requires care to be taken with circuit layout, wiring, shielding and grounding so that cross-talk and over-voltages are kept to a minimum.

Behlke HV switch HTS161-01How is power dissipated?

The equations below show how the power dissipated in the switch is proportional to the resistance R, capacitance CL and frequency f in each case. Typically not much can be done to escape the effects of the voltage but resistance, capacitance and frequency can be minimised to limit power losses.

equations for power dissipation in a HV switchPower dissipated inside a high voltage switch for frequencies <100Hz (left) and >100Hz (right)

The static on-resistance R will be given on the datasheet for each switch and the load capacitance CL should be known or estimated conservatively. The value for PD should then be compared with the value given on the datasheet.

HV switch spec table extraact

If the value for power dissipation is greater than that given on the datasheet then additional cooling options may be needed. The power dissipation for a variety of cooling options is usually listed to help identify the correct solution.

Different types of switch

Different switch technologies suit different applications. High voltage switches supplied by PPM use four main technologies to cover 1kV – 140kV and 15A – 16kA:

  • MOSFET – (Metal Oxide Semiconductor Field Effect Transistor)
  • IGBT (Insulated Gate Bipolar Transistor
  • MCT (MOS-controlled Thyristor)
  • SCR (Silicon-Controlled Rectifier)

Critical low frequency or resistive load applications may use a low on-resistance switch to help to reduce ohmic losses. Push-pull types have two switches in a half-bridge configuration. This enables the load to be actively discharged to provide a very fast falling edge.

Analysing and modelling the system

The final choice may come down to factors that only become apparent when analysing the entire system. Modelling the entire system using software such as PLECS or SPICE will enable you to optimize parameters and finalise your switch selection. For example, inductive loads or large stray inductance will generate reverse voltages which could damage the switch. Using freewheeling diodes can protect the semiconductors within the switch from these events.

Avoiding damage to the switch

The values specified by the manufacturer should not be exceeded as this may destroy the internal MOSFETs or the trigger circuit. Particular care must be taken with cable routing and shielding as large voltage and current transients on the high voltage circuit can induce significant instantaneous voltages on low level control lines. Subtle overcurrent and overvoltage events should be identified initially at low voltages so as not to create long term reliability issues in the full system at full load. Initial system testing should be done at low voltages to check there are no obvious issues. Overvoltages will scale with voltage – checks should be done to ensure low and high voltage signals remain in the correct limits determined by the switch or other components. Tests should be done at low operating voltages first before increasing to the full high voltage value.

PPM supply fixed on-time switches, variable on-time switches and pulsed power switch assemblies.  The full range offered by PPM can be found in the high voltage switches section.

Fixed On-Time Switches

  On-Time Description Maximum Voltage Maximum Current Switch On-time
Fixed thyristor/SCR switches Current Depending 4 – 150 kV 1 – 16 kA > 35 us
General Purpose Fixed MOSFET Switches Fixed 4 – 150 kV 15 – 200 A 100 – 300 ns
Low Impedance MOSFET Switches Fixed 0.5 – 40 kV 70 – 1600 A 150 ns
Ultra-Fast MOSFET Switches Fixed 3 – 12 kV 60 – 200 A 120 – 200 ns
Low On-Resistance Fixed MOSFET Switches Fixed 3 – 24 kV 60 – 1040 A 150 – 250 ns

Variable On-Time Switches

  On-Time Description Maximum Voltage Maximum Current Switch On-time
General Purpose Variable MOSFET Switches Variable 0.5 – 36 kV 12 – 640 A > 50 ns
High di/dt MOSFET Switches Variable 3 – 36 kV 200 – 3200 A > 300 ns
Low Capacitance MOSFET Switches Variable 3 – 140 kV 30 – 800 A > 60 ns
Low On-Resistance Variable MOSFET Switches Variable 0.5 – 21.6 kV 125 – 3750 A > 150 ns
AC MOSFET Switches Variable 1.2 – 36 kV 12 – 130 A > 50 ns
General Purpose IGBT Switches Variable 3 – 36 kV 800 – 9600 A > 0.2 us
Variable Thyristor/MCT Switches Variable 4 – 18 kV 3 kA > 1 us
Push-Pull MOSFET Switches Variable 2x 1.2 – 140 kV 2x 12 – 200 A > 50 ns
Pulser Switches Variable (2x) 3 – 12 kV (2x) 15 – 80 A > 50 ns

Pulsed Power Switch Assemblies

  On-Time Description Maximum Voltage Maximum Current Current Rise Rate
Pulsed Power Stacks Variable 30 kV 20 – 50 kA 10 – 30 kA/us


Pulsed Power Switch Assemblies

Pulsed power stacks

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More Information?

Telephone +44 (0)1793 784389 or email: sales@ppm.co.uk