A solid state modular -36 kV, 24 A crowbarless DC power supply is designed, developed and demonstrated for full range 24-pulse input and low ripple output with low stored energy for biasing vacuum tube based high power RF amplifiers. Special care has been taken to achieve full range 24 pulsed 11 kV input system with lower input harmonics and higher input power factor. An optimized control strategy is adopted in this power supply, which has unique capability to provide ripple free output. Input section of this power supply is completely independent of its output control section. So the variation of the input line voltages, setting of the output voltages and the number of faulty modules of this power supply do not affect its input and output performance parameters. This power supply achieves current THD ≤ 6%, voltage THD ≤ 0.8%, input power factor ≥ 0.97, output voltage stability ≤ 0.4%, peak to peak output voltage ripple ≤ 0.72% and output stored energy < 10 Joule. The adopted scheme neither needs any input line filter nor needs any crowbar for protecting sensitive RF amplifiers. The adopted scheme is simpler to implement, cost effective and has potential to meet stringent input and output performances demanded by high power RF amplifiers. 

High power radio frequency (RF) amplifiers demand stringent input and output performances from their bias power supplies. Low input harmonics and high input power factor (IPF) are crucial input performance requirements, while low output ripple, low output stored energy and tight output voltage stability are crucial output performance requirements of these power supplies. A solid state modular -36 kV, 24 A crowbarless DC power supply is designed and  developed which uniquely achieves full range 24-pulse input and low ripple output simultaneously, specifically important for biasing vacuum tube based high power  RF amplifiers. In the adopted scheme, the variation of the input line voltages, setting of the output voltages and the number of faulty modules of this power supply do not affect its input and output performance parameters.

Salient features of -36 kV, 24 A DC power supply

1. Full range 24-pulsed input system, which achieves low input harmonics and high IPF, thereby completely avoiding input filter in three phase 11 kV line.
2. Full range low ripple output, irrespective of input and output voltages and number of faulty power modules, thereby completely avoiding crowbar for protecting sensitive RF amplifier.
3. Control is on intermediate low voltage, even though both the input and output of this power supply are on the high voltages.  
4. Input section is completely independent of the output control section. So the variation of input voltage, output set voltage and number of faulty modules of this power supply neither affect the input harmonics and IPF nor output voltage ripple.
5. Online isolation of faulty modules and auto staggering of healthy modules.
6. Flexibility of increasing the output voltage by adding number of DC-DC power modules having higher isolation in them.
7. High system reliability and availability due to active redundancy incorporated in this modular power supply.
8. It is a unique scheme, which inherently achieves both 24 pulsed 11 kV input system as well as full range low ripple output simultaneously. It achieves better input and output performances at lower cost compared to existing schemes employed worldwide and so is likely to gain popularity for biasing high power RF amplifiers.

INTRODUCTION

High power radio frequency (RF) amplifiers demand stringent input and output performances from their bias power supplies. Low input harmonics and high input power factor are crucial input performance requirements, while low output ripple, low output stored energy and tight output voltage stability are crucial output performance requirements of these power supplies. Most of these requirements are contradictory in nature, posing major challenge to the designer. In addition, the common drawback of prior schemes of controlled DC power supplies is that, with increase in control range, both input and output performances deteriorate. A solid state modular -36 kV, 24 A crowbarless DC power supply is designed, developed and demonstrated for full range 24-pulse input and low ripple output with low stored energy for biasing high power tube based RF amplifiers. Special care has been taken to achieve full range 24 pulsed 11 kV input system with lower input harmonics and higher input power factor. An optimized control strategy is adopted in this power supply, which has unique capability to provide ripple free output. Input section of this power supply is completely independent of its output control section. So the variation of the input line voltages as well as setting of the output voltages and even the number of faulty modules of this power supply do not affect its input and output performance parameters at all. Active redundancy has been incorporated in this modular power supply to improve its reliability significantly. Eight out of seventy two number of power modules are kept as active redundant so that failure of up to eight number of power modules does not affect the operation of this power supply. Wire burn test has been carried out on this power supply to ensure that energy dumped during arcing of RF amplifier is below 10 Joule. The adopted scheme neither needs any input line filter nor needs any crowbar for protecting sensitive RF amplifiers.

Performance parameters of power supply at -36 kV, 3 A DC operating point

INFRASTRUCTURE

• Infrastructure facilities for fabrication and testing of various subsystem of this high voltage DC power supply like transformer rectifier unit, DC-DC power modules, HF transformers and digital control-protection system.
• Measuring instruments like HV probes, current probes, oscilloscope, multimeters, meggar etc. Various sources of measuring instruments are commercially available for the manufacturer to augment the infrastructure.
• Some of the test equipment or subsystems or test load required for commercial production and testing of this power supply may be sub-contracted by the party, if the related infrastructure is not available with them under the same roof.

SPACE

• Floor area ≥ 500 square feet

MANPOWER

• Trained professionals having technical background and expertise in the fields of high voltage systems, input switchgears, multi-pulsed converter transformers, DC-DC power converters, high frequency (HF) transformers and digital control-protection system, etc.