DC Power Sources for the High Power RF Amplifiers

DC Power Sources for theHigh Power RF Amplifiers

By Rolf Wedberg

Review ESS Spoke RF Source

11 – 12 December 2012

Agenda

• DC Power supplies overview• Anode power supply

– Main components– Suppliers– Expected performance (simulation)– Simple simulation for ringing and envelope vs time

• Filament power supply• Grids power supplies

– Control grid– Screen grid (modulation)

• Summary

11 Dec 2012 Rolf Wedberg – DC Power Sources for the High Voltage Amplifiers 2

DC Power Supplies


DC Power Supplies: Overview


8.8VDC 8.8VDC

0

DC circuit

4 0 0 V

Filament power supply

Control grid supply1 3 0 0 V


4 0 0 V

1 3 0 0 V

Screen grid supply

Anode filter

0 0

Anode power supply

0

18 kV

Anode filter18 kV

0

1 Anode PS2 Filament PS’s2 Control-Grid PS’s2 Screen-Grid PS’s

Anode Power Supply


8.8VDC 8.8VDC

0

DC circuit

4 0 0 V




4 0 0 V

1 3 0 0 V

Screen grid supply

Anode filter

0 0

Anode power supply

0

18 kV

Anode filter18 kV

0

611 Dec 2012 Rolf Wedberg – DC Power Sources for the High Voltage Amplifiers

Anode Power Supply: Main Components

Vmax = 18 kV pulse width 3.5 ms Imax = 18 A pulse rate 14 Hz Series-switches Maximum voltage droop 1 kV dI/dt limiting with inductors Capacitor charger with voltage and power regulation

Two Outputs

In each output For both outputs

31 kW

From saf ety control

0

1 3 0 u F

Anode supply

5

I 3

0

Capacitor charger

Series switch

12

18kV

0 0

To anode

Volt. div ider

Pulse current monitor

3 phase 400 V

+ -

+ - S

To the other anode

DC current monitordV/dt monitor

From control

Optical f ibre

0To series switch control

Crowbar

To saf ety control

Anode Power Supply: Suppliers

• These components are not state-of-the-art• Readily available• Some examples:

– Capacitor Charger: FuG , TECHNIX– Capacitor: Nokian, Hivolt capacitors, ABB and others– Switches: Behlke, DTI and Gihomeq AB– Coils: Unitrafo, Transform and others– Assembly: High Voltage AB, JACO industries and others


Anode Power Supply: Performance

• Main problems:– Series switches current capability– Output voltage ringing due to the inductive outputs

• To check performance

11 Dec 2012 Rolf Wedberg – DC Power Sources for the High Voltage Amplifiers

– A simple simulation has been run to observe behaviour and ringing of the output voltage of the anode power supply

– Cable length, filters, cavity etc. have been included– Assumptions:

• Tetrode considered as a switch

8

Anode Power Supply Simulation

Anode Power Supply: Simplified circuit


Tit le

S ize D o c u m e n t N u m b e r R e v

D a t e : S h e e t o f

<D o c > R W

S im u la t io n o f a n o d e p o we r s u p p ly .

A

1 1W e d n e s d a y , N o v e m b e r 1 4 , 2 0 1 2

L 15 n H C 1

4 1 p F

R 10 . 1

Q value app. 300

+

-

+

-

S 1

S

V O N = 1 . 0 VV O F F = -1

0

L 6

0 . 1 u H

C 21 0 0 p F

C 31 0 0 p F

L 7

2 5 u H

L 8

1 6 u H

C c a b le1 n 0

00

L 5

7 0 0 u H

R 2

5

R 3

1 0 m

R 4

1 0 m

R 5

1 0 m

0

00

C 41 3 0 u F

L 21 n

0

L 31 n

L 45 n HC 5

4 1 p F

R 60 . 1 u

K 1

C O U P L I N G = 0 . 9 9K _ L in e a r

K K 2

C O U P L I N G = 1K _ L in e a r

0

R 70 . 1

V 1

F R E Q = 3 5 1 . 6 5 9 M E GV A M P L = 4V O F F = 0

A C =

R 8

0 . 1

T1

R 91 M E G

0

Anode DC connectionAnode filterAnode filterHigh voltage cableAnode power supply

Spoke cavityInput power coupler

Output power couplerWaveguide

SignalgeneratorTetrode

Anode cavity

L3 and L4

L1 and L2

The equivalent electric circuit used for the simulations:

Anode Power Supply: Transient regime


Order-of-magnitude estimate shows that the tetrode cavity voltage is stabilized after 20 us

0 µs 10 µs 20 µs 30 µs 40 µs 50 µs

-6 k

V

-4

kV

-

2 k

V

0

2

kV

4 k

V

6

kV

Enough time for the amplifier to be stable on every pulse

Filament Power Supply


8.8VDC 8.8VDC

0

DC circuit

4 0 0 V




4 0 0 V

1 3 0 0 V

Screen grid supply

Anode filter

0 0

Anode power supply

0

18 kV

Anode filter18 kV

0

Vmax 15VImax 200 ARamping for 8 min

Grids Power Supplies


8.8VDC 8.8VDC

0

DC circuit

4 0 0 V




4 0 0 V

1 3 0 0 V

Screen grid supply

Anode filter

0 0

Anode power supply

0

18 kV

Anode filter18 kV

0

Control grid• Max. output:• Voltage 400 VDC• Current 4 A• Positive terminal grounded• i.e Delta, FuG or Technix

Screen grid• Max. output:• Voltage 1300 VDC• Current 0.7 A• Negative terminal grounded• i.e FuG or Technix

Summary

• The Anode Power supply:– can be made of an assembly of commercial components– is special to use the power grid in an efficient way and designed for

the pulsed load• Grid and filament power supplies are ”off the shelf” commercial power

supplies

Thank you Rocio and Vitaliy for help with Power Point


Control Grid Connection

0

D 1D 2

R 1

1 k

R 2

1 k

V 1

2 0 0 V D CR B le e d

0

0

If positiv e switch of f RF within 100 us and control grid power supply in 20 ms.

Thales recommended control grid connection.

50 to 800 Ohm


The control grid voltage will become more negative during RF-pulse. Bootstrapping?The power supply is working with high output current into the bleeder resistor so that it may sink current during the RF-pulse.

1 3 0 0 VR 1 31 8 k

Screen grid supply

0

R F g ro u n d in g

0

Alternative without switch

1 3 0 0 V

Screen grid supply

R 1 41 8 k

0

R F g ro u n d in g 1

0

+-

+-S 1S

Alternative with switch


The Power Supply needs protection when there is an arc from the anode. The Screen grid may be used to modulate, turn off anode current between RF pulses.

Screen-grid Connection: Modulation

Documents

DC Power Sources for the High Power RF Amplifiers