Wednesday, August 6, 2008

High Voltage, Low Noise DC/DC Converter Circuit Designs

Have you seen the Linear Technology application note on high voltage, low noise DC/DC converters? Ap notes don't get any better than this one. It includes circuits for high voltage power supplies rated from 200V to 1000V. It also addresses noise issues, and the effects of various voltage feedback techniques on transient response.

The ap note describes resonant Royer topologies (which produces power by utilizing sinusoidal waveforms instead of switched waveforms) and also flyback converters. It also describes methods of measuring output noise.

If you are planning to design a high voltage power supply for photomultipliers (PMT's) or other applications requiring low noise, low power in the range of hundreds of volts, you might want to peruse the ap note. It is Linear Technology Application Note 118.

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Wednesday, April 2, 2008

Extremely low cost high voltage power supplies

If you are looking for an extremely low cost high voltage power supply, a good place to look is consumer products that incorporate high voltage. For example there are electronic fly swatters that claim to produce 4kV! Of course the current is very low, and performance in terms of ripple, regulation and stability is not all that good. The electronic fly swatter may not even put out nearly the voltage claimed. However, if these performance related issues are not important in your application, or just need to generate a spark, you're in luck. Besides, you can find them for under $10, and sometimes even under $5. Other products to consider as a source of low cost high voltage are air purifiers, mosquito zappers, LCD display backlights, piezoelectric spark generators, and vehicle electronic ignitions.

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Saturday, January 19, 2008

High Voltage Op Amp

National Semiconductor has just introduced two high voltage op amps, types LME49811 and LME49830. Operating with supply voltage up to 200V rail-to-rail, this supports a typical output voltage up to 192V, peak-to-peak. With a properly designed output stage, an output power up to 500W can be generated. While the op amp is aimed at audio applications, it can also be used for high voltage power supply and high voltage amplifier applications. These op amps might also serve as post-regulators or active ripple reducer circuits on a high voltage power supply.

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Wednesday, October 24, 2007

Bear Gets into High Voltage

The company, Bear Power Supplies, claims that its new BPS Series high-voltage DC-to-DC converters have up to five times better efficiency and ten times better load regulation than similar products on the market. The output range has recently been increased to 300V models.

Notable specifications:

Operating Temperature: -55 to +85C. No heatsink or electrical derating required.

Load regulation: 3% change from no load to full load (pretty good for a proportional converter)

Size: 0.5 x 0.5 x 0.4 inches (12.7 x 12.7 x 10.2 mm)

(Sorry for the headline...)


Wednesday, July 4, 2007

High Voltage Transformers

High voltage transformers are used for isolating two sections of a circuit or system, and along with voltage multipliers, generate the output of high voltage power supplies. Some HV related issues that need to be addressed in the design include:
  • layer winding or universal winding (also know as pi winding)
  • volts per layer
  • compatibility with subsequent potting or encapsulation. (Incompatibility can cause failure of the potting material to cure, subsequent failure due to dielectrics in series, and other problems.)
  • clearance and creepage distances

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Tuesday, July 3, 2007

High Voltage Power Supplies

A high voltage power supply consists of the following sections:
  • ac to dc converter (for ac input types)
  • dc to ac converter which generally operates at 20kHz or above
  • high voltage transformer
  • voltage multiplier, consisting of hv capacitors and hv diodes in a configuration that, as the name implies, multiplies its input voltage by an integral amount (neglecting losses and inefficincies). This also serves as the rectifier, converting the ac back to dc.
  • output filter (to reduce the ripple to the desired amount)
  • hv divider to measure the output voltage
  • control and monitoring circuits
  • output hv connector

Sometimes known as high voltage generators, high voltage power supplies are available in pc board modules, larger modules and as rack mount high voltage power supplies. Very high voltage and very high power supplies can encompass an entire rack, and/or have an external high voltage section.

Both linear and switching mode configurations are available.

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