1. Microwave Amplifier Power Supply
High Voltage
Switching Power Supply Design
at System Level
Sharing Industry Experience with EE136
Alex Chen
MONDAY December 1, 2003

2. BASICS of Traveling Wave Tube (TWT) Amplifier
Reference:
BASICS of Traveling Wave Tube (TWT) Amplifier

3. Key Notes of TWTA: Heater/Filament is closest to Cathode Voltage.
Heater and Cathode act as electron gun, and they are on the side RF Input.
Collectors sits on RF output.
Electrons are fired from Cathode and received from Collectors.
RF signal is amplified through bunching effect after traveling along the path of Helix coil.*
Higher Cathode voltage  Higher RF Power *
Advantage of TWTA (over solid state amplification) is the linearity and output power*
TWTA Efficiency: 50% to 60% vs. Solid State: 25% to 30%
Ranges of Frequency for TWTA: 1Ghz – 40 Ghz
*Additional Information:

4. Application of TWTA Point to Point Communication
Satellite communication and Rader Appz
Missile tracking application for military
Television live broadcasting
LIVE news vans with satellite dishes on the roof carry TWTA inside

5. TYPICAL OPERATING CONDITIONS POWER SUPPLY REQUIREMENTS
Specification of Communication TWT: MODEL NO. MEC 5417D From TELEDYNE Electronics
TYPICAL OPERATING CONDITIONS
POWER SUPPLY REQUIREMENTS
ELEMENT
VOLTAGE
CURRENT
VOLTAGE MIN
VOLTAGE MAX
CURRENT MAX
HEATER
-6 Vdc
1.6 A
-5.8 Vdc
-6.6 Vdc
2 A
HELIX
W/RF
GROUND
7 mA
10 mA
W/O RF
1 mA
GRID ON
200 Vdc
0.5 mA
100 Vdc
250 Vdc
GRID OFF
-200 Vdc
0.1 mA
-500 Vdc
CATHODE (Ek) kV
290 mA
-10 kV
-11 kV
325 mA
COLLECTOR W/ RF #1
6.1 kV
75 mA
56% x Ek + 2%
125 mA #2
4.4 kV
208 mA
40% x Ek + 2%

6. Key Notes for Reading the Specification of TWTA:
Cathode (Ek) Voltage is NEGATIVE.
Collector 1/2 reference to Cathode Voltage
Collector Voltages read POSITIVE
Heater Voltage also references Ek
Test Equipments (Ex: 1kX Divider) are reference to Ground
GROUND
Collector 1
Collector 2
Cathode
Heater Comparing Relative Voltages
-10kV
+6kV
+4kV
-6V

7. Who are in Business? (Power Supply Manufactures)

8. Left: 600W Tri-band CW TWTA Right: Power Supply
Products of ETM Electromatic Inc.
Interchangeable module-type Power Supply
Left: 600W Tri-band CW TWTA Right: Power Supply

9. More Products
Astrium Project for Skynet: -15kV Cathode Voltage Power Supply (Far Left) -RF Amplifier by CPI (Right) with input RF source (front) Output dummy load (back)
4-Astrium Units Combined for Project Skynet

10. High Voltage Filters Ready to be Tested
Right: High-Voltage Filters after assembly ready to be tested Left: Potted filters to be retested (*Potting materials = High-Voltage Insulation)

11. Testing High-Voltage
High-Voltage modules are tested in flouriner (liquid insulator) before potted with liquid silicone rubber

12. Our Customers

13. Block Diagram of Switching PS
~ +
~ -
HV Filter
~ -
~ +
~ -
~ +
~ -
~ +
DIODE
Block Diagram of Switching PS

14. My Current Machine: 10kV 4-Collectors Test Set for L3

15. Major Components Input Filter or PFC H-Bridge: Buck + Full-Bridge
Pulse Width Modulation for H-Bridge
Diode
High-Voltage Filter
Heater
Grid Modulator
AC Fan Driver for cooling
Logic & Control
Human Interface Control
Low Voltage Power Supply
RED: Topics will not be discussed in class

16. Presentation Notes: Input Filter H-Bridge PWM Board Diode
LRC filtering with delay and soft-start
Phase Loss detection circuit
H-Bridge
Isolated Buck Converter to Full-Bridge
PWM controls Buck Converter.
Duty of Full-Bridge is fixed at 50%.
The use of transformers for gate driver circuits
PWM Board
Controls both buck drive and full-bridge.
Master/Slave Configuration for Buck to Full-Bridge
Gate Driver Chips
Pre/Post Regulation
Diode
Primary and Secondary Transformers
Voltage Doublers Circuit
High-Voltage diodes are used for rectification
High-Voltage Filter
RC Low Pass Filter
Feedback sense from Cathode Voltage to PWM
Post Regulation
Arc Detection

17. Fast Heater 400Hz Sinus Fan Driver Forward Regulator
Presentation Notes (continue):
Fast Heater
Forward Regulator
Same chip as PWM chip
Two different voltage reference
Single-shot re-triggerable chip
Voltage Sense / Current Sense
400Hz Sinus Fan Driver
Boost, Half Bridge, Flyback
Hi/Low sides driver
Microcontroller with oscillator
Over voltage / Over Current Detection