Low Noise 5V to 400–1000V Adjustable HV Supply (1–200µA) for Portable System

[Zaim01]

Hi,

We are designing a compact, battery-powered system that requires a regulated high-voltage DC output with the following specifications:

• Input: 5V

• Output: Adjustable 400V to 1000V

• Load current: 1µA to 200µA

• Very low ripple and noise

• High efficiency and small form factor

The supply will be used as a bias source for sensitive detectors (e.g., APD/PMT-type devices), so output stability and low noise are critical. The output must remain stable across the specified load range.

I am currently considering a closed-loop flyback topology with post-filtering, but I am open to alternative architectures.

Could you please recommend:

• Suitable controller ICs from your portfolio?

• Relevant reference designs or evaluation boards?

• Design techniques for minimizing ripple and noise at these voltage levels?

Any guidance or application notes would be greatly appreciated.

Thank you.

[Peter BENSCH]

In principle, this can be done with a flyback, but the effort required in relation to the output power is probably too great and a flyback would be significantly oversized. You should therefore consider something that has been used for many decades to generate high voltages with low output currents: a voltage multiplier, i.e. something similar to a Cockcroft-Walton generator. With 12..13 stages, you should achieve 1kV with some control reserve; 15...22nF capacitors should be sufficient.

Advantages:

• Minimal system volume (no large, expensive and complex transformers are required)
• Ripple and noise can be easily controlled with sufficiently high frequency and RC filters
• Voltage can be regulated via the switching frequency (~100kHz...few MHz) and/or PWM

Disadvantages:

• Sufficiently high voltage capacitors
• Many high-voltage ultrafast diodes due to the necessary multiplier stages

You should urgently observe the usual precautions to minimise ripple and noise:

• Layout with star-shaped GND, strictly separated from the signal grounds (reference voltage, opamp controller, etc)
• Air and creepage distances sufficiently large and also as far away as possible from the signal paths

There are a few devices in the portfolio of STMicroelectronics that you can use in such a voltage multiplier:

• STM32 as PWM generator, e.g. STM32C011 / STM32G030 / STM32F030
• TSZ121 as precision opamp with ultra-low bias current
• TS431 as reference

Hope that helps?

Regards
/Peter

[RobK1 · Accepted solution]

This application note by the late, great Jim Williams might be of some interest to you:

AN118: High Voltage, Low Noise, DC/DC Converters A Kilovolt with 100 Microvolts of Noise | Analog Devices

[Zaim01]

Thanks Peter for the answer its helpful.

[Zaim01]

Thanks. this is exactly what i was looking for.