The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

DEVELOPMENT OF HIGH-POWER HIGH-VOLTAGE
DC POWER SUPPLY BASED ON SERIES RESONANT TECHNOLOGYFOR MW CLASS RF AMPLIFIER
Manabu Souda, Choji Yamazaki, Fusao Saito, Toshiba Corporation, Japan
Masahito Yoshii, Chihiro Ohmori, KEK, Japan
Masanobu Yamamoto, Fumihiko Tamura, JAERI, Japan
Abstract
High-power high-voltage dc power supply has beendeveloped based on series resonant converter technology
for a MW class RF amplifier. For low-voltage ripple, an
IGBT inverter consisting of 1400 V-600 A devices isdrives with a maximum switching frequency of 31.2 kHz.
A performance test was carried out using an RFamplifier. We examined this power supply under twodifferent conditions. One was with a voltage of 10 kV
under a 1-sec rectangular-wave output current. Thevoltage ripple was 21 VPP with a peak current output of 92
A. The other was with the same voltage under a 24-msec
half-sine wave output current. The voltage deviation was
150 VPP during the 24-msec half-sine wave output.
A protection test for a short circuit in the RF amplifier
was also examined. The test wire was not fuse. Therefore
it was proved that this dc power supply can protect RF
amplifier from a short circuit fault without a crowbar
circuit.
These experiments showed that the dc power supply
had a low voltage ripple and high-speed response, thus
verifying that it performed well for the MW class RF
amplifier.

INTRODUCTION
In Japan KEK and JAERI are proceeding with a joint
project to produce a high-intensity Proton synchrotron
accelerator. The synchrotron requires a MW class RF
amplifier to accelerate a proton beam. The anode dc
power supply for this amplifier required high power, highvoltage and high stability. In addition, this power supply
needed small voltage ripple, which affects the protonbeam, and a constant voltage, which is made under highspeed response with changes of output current.
For a conventional anode dc power supply for an RF
amplifier based on thyristor converter technology, a large
capacitance dc filter is necessary to reduce the voltage
ripple caused by the convert utility voltage (50/60Hz),
therefore the energy into an RF amplifier is large in caseof a short circuit fault. As a result, a protection circuit socalled “crowbar” circuit has been indispensable forconventional thyristor power supply systems.
To solve the above problems, we have developed ahigh-power dc power supply for an RF amplifier based onseries resonant converter technology. With this technology,
switching frequency can be made quite high. As a result,dc filter capacitance can be reduced. The dc power supply
has three advantages for a high-power RF amplifier.

First, the voltage ripple, which affects the proton beam,
is small. Second, the change of output current in a rapidcycle, the voltage deviation is small. Third, no crowbar
circuit exists.
This paper describes the design and the experimental
investigation of the power supply.

DESIGN OF DC POWER SUPPLY1) Specification
The dc power supply based on series resonant
technology is specified in Table 1. Figure1 shows a block
diagram of the dc power supply system. The system
consists of an input circuit that contains a utility
transformer and rectifier converter, a main circuit and acontroller. The main circuit includes fifteen inverter units
and a H.V. output section.
Table 1:Specifications of the dc power supply
Item

Specification

Output voltage

10 kV (maximum 13kV)

Output current

92 A

Output power

peak 1.2MW (duty 60%)

Efficiency> 80 %

Voltage ripple rate

< 0.2 %0-P (@10 kV)

Voltage deviation< 1.0%0-P (@24-msec halfsine wave output current)

Energy poured into tube incase of short circuit fault< 50 J2) Dc input circuit
The dc power supply requires a dc input voltage ofabout 700 V, from the utility voltage stepped down
through a 1.7 MW transformer (6.6 kV/505 V) andconverted to dc voltage by a 12 pulse-rectifier converter,
which were put in an outside oil tank.

3) Inverter unit
The IGBT inverter consists of four arms and each arm
consists of two paralleled IGBT devices. Thay are 1400
V-600 A devices. They are provided with built-in freewheel diodes (FWD) to carry reverse current. The
switching frequency is 31.2 kHz maximum. The inverter
is designed to operate under zero current switching mode,
where the IGBTs turned off while reverse current isflowing through the FWD in order to minimize switchinglosses at turn-off period. The snubber circuit could beThe 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

13kV-92A

high frequency
transformer2Ω

3φ6.6kV

100µH

18µF
CT
<oil tank><IGBT inverter>

Same 14 style circuit of above figure<dc input circuit>
Voltagereference+<DSP>*

Feed-forward-PI<H.V. section><Inverter unit><high voltage rectifiers><Main circuit>
A/Dswitching timing system+
A/D<controller>>

To IGBT’s gates<dc power supply>

Figure 1 Schematic diagram of dc power supply for high power RF amplifier
removed since the IGBT’s over voltage at turn-off does
not arise.
The resonant circuit consists of 1.5 µF resonantcapacitance and the total circuit inductance that consistsof a bus inductance and a leakage inductance of the highfrequency transformer. In order to maintain the zerocurrent switching (ZCS) condition under the highfrequency operation of IGBT, the leakage inductance ofthe high frequency transformer must be low. Thistransformer is composed of two units. In each unit, thesecondary winding is wound between two primarywindings to obtain a high coupling factor between the twowindings and to minimize leakage inductance.
Secondary winding is connected to high voltage fullbridge diode rectifiers, which are connected in series.
These rectifiers consist of twenty diode devices in series.
They are 1000 V-20 A devices with the specification ofultra fast recovery to reduce recovery loss.
Figure 2 shows an external view of the inverter unit.
The resonant circuit and high voltage rectifiers areinstalled in an oil tank for cooling and insulation.

about 1/10 compared to the conventional dc power supply.
Therefore the energy that pours into a load in case of ashort circuit fault reduces dramatically. Then a crowbar
circuit can be removed. A resistance of 2 ohm isconnected in series at the output circuit because most ofcapacitance energy is consumed when a short circuit fault
occurs. Moreover, connecting a 100 µH air core coil inseries is aimed at both decreasing peak current of a shortcircuit and choking for voltage ripple.

5) Controller
The controller quickly maintains the output voltage
collect by changing the IGBT switching interval. The
output voltage is detected by the voltage divider at theH.V. section and is kept constantly by the feedback
control system. Furthermore, feed-forward control
maintains the output voltage at a constant value against asudden change of the load current. The feed-forward
control detects the output current and converts it directly
the IGBT switching interval.
Figure3 shows an external view of the dc power
supply’s main circuit. It’s dimensions of were
4500mm(W) x 2000mm(D) x 2650mm(H).

EXPERIMENTAL RESULT

Figure2 External view of invert unit

4) H.V. Output section
At the H.V. output section, the filter capacitance of
18µF is charged by the resonant currents, outputting from15 inverter units. Because 15 inverter units are multiple
connected and operated with equivalent frequency of 468
kHz ( = 15*31.2 kHz), the filter capacitance is reduced by

The performance test was carried out on the dc power
supply with a high power RF amplifier that was able tooutput 1MW to drive tetrode tubes (TH588) by push-pull.
Figure 4 shows a schematic diagram of the test circuit.
The 100 m coaxial cable was connected between the dc
power supply output and the anode of the tubes. Bychanging the control grid level, the RF amplifier output
power was changed. Output voltage of the dc power
supply was measured at the end of the coaxial cable, andthe output current was measured at the cathode of thetubes in the RF amplifier with shunt resistance.
The performance of dc power supply was confirmedwith three kind of test. Firstly, voltage ripple wasevaluated under 1-sec rectangular wave output current at10kV. Secondly, voltage deviation was evaluated under24-msec half-sine wave output current at 10kV. Lastly,
protection test against a short circuit was carried out.

The 14th Symposium on Accelerator Science and Technology, Tsukuba, Japan, November 2003

Figure 5 shows the output voltage waveforms when theoutput current was a 1-sec rectangular wave. The current
changed repeatedly from 5 A at the bottom to 92 A at thepeak. The voltage deviation was 600 V when changing
from 5 A to 92 A. The ripple voltage was 21Vpp (0.1%0-p)
for 92 A.
Figure 6 shows the output voltage waveform when theoutput current was a 24-msec half-sine wave. The peakcurrent was 92 A while the idling current was 5 A. The
voltage deviation was 150 Vpp (0.75%0-p) in the 24-msec
half-sine wave output.
The protection test for a short circuit fault inside theRF amplifier was performed with 100m coaxial cable. A
short gap and a test wire (φ=0.3mm, L=200mm) wereconnected in series at the end of the coaxial cable. This
test was carried out at the highest voltages in ouroperation: 13kV. Figure 7 shows the voltage and current
waveforms in this test. The test wire did not fuse, because
a resistance of 2 ohm in the dc power supply consumed
the most of its energy storing the dc filter capacitance.
From the results of above three tests, it was confirmedthat the power supply has satisfied the specification inTable 1.

exhibited high accurate voltage stability against the rapidchange of the output current.
A protection test against a short circuit was also
examined. The test wire was not fuse. Therefore it wasproved that this dc power supply can protect RF amplifier
from a short circuit fault without a crowbar circuit.
The experiment showed that the dc power supply had
good performance for a MW class amplifier.
46A

Currents: 25A/div
21V
Voltage: 50V/div
20ms

Figure 5 Output voltage under 1 sec rectangularwave output current.
46A

Currents: 25A/div

150V

4ms
Voltage: 100V/div

Figure 3 External view of dc power supply main circuit
HV probe

RF amplifier

MA cavity

Figure 6 Output voltage under 24-msec half-sinewave output current.

3φ−
6.6kV

voltage:2kV/div
Shuntresistances
dc input circuit

Current:1kA/div

dc power supply

50µs

Figure4 Schematic diagram of performance test circuit

CONCLUSION
A high-power, high-voltage dc power supply has beendeveloped utilizing series resonant converter technology
for a MW class RF amplifier. The dc power supply has
been shown the excellent performance of low-voltage
ripple and high-speed voltage control. The low-voltage
ripple performance has been attained by 15 inverter units
which are multiple connected and operated withequivalent frequency of 468 kHz.
Moreover, the voltage control system which varies theswitching interval corresponding to the load current has

Figure7 Voltage and current wave of protection test.

REFERENCES[1] M. Souda, F.Endo and C. Yamazaki “Development ofhigh power, high voltage dc power supply for pulsedpower application and accelerators”, Proc. of 13th
International Conference on High-Power Particle
Beams (BEAMS2000), 2000, pp930-933.