Download February 24, 2009 CERN J. Matheson, Rutherford Lab D

Power Protection for Staves/Supermodules
Two Approaches
• Purpose of circuit: Provide an alternate current path for serial power
current on the module level to prevent disabling an entire stave in
case of an open in the module. It also gives a module level of control
allowing a specific module to be turned on and off.
• Prototype Circuits for both approaches
• Measurement Results for both
• Future Effort
February 24, 2009 CERN
J. Matheson, Rutherford Lab
D. Lynn, J Kierstead, BNL
Rutherford Laboratory AC-DC
Protection Circuit
Rutherford Lab Protection Circuit
Theory of Operation
•
Serially addressable switches are used to select and turn on a local
oscillator. Isolation is maintained by feeding the output from the oscillator to
a capacitor
•
The capacitively coupled AC oscillator output drives a ladder of diodes and
capacitors giving a DC voltage gain of x 4
•
The DC voltage then turns on a MOSFET which in turn supplies current to
the base of the shunt transistor dropping the voltage to the VCESat of the
transistor
•
To test this circuit the diode/capacitor ladder and MOSFET was constructed
using discrete components. A signal generator was substituted for the
addressable switch and oscillator. The output of the MOSFET attached to
existing serial power boards. Two modules were switched on and off in
loaded and unloaded states with the results in the next slides.
Rutherford Laboratory AC-DC
Protection Circuit
• Shown are results of switching
adjacent modules on and off
with no load.
4.5
4
output (V)
3.5
3
CH3
2.5
CH4
2
1.5
1
0.5
0
-1.00E-04
0.00E+00
1.00E-04
2.00E-04
3.00E-04
4.00E-04
time (s)
switching off no 2 (no load)
5
4.5
4
3.5
output (V)
• Some perturbation is seen in
the module that is not switched
but it is not excessive
switching off no 1 (no load)
3
CH3
2.5
CH4
2
1.5
1
0.5
0
-1.00E-04
0.00E+00
1.00E-04
2.00E-04
time (s)
3.00E-04
4.00E-04
Rutherford Laboratory AC-DC
Protection Circuit
• Shown is the same test as in
the previous slide except that
the modules are loaded
switching off no 1 (with load)
5
4.5
4
output (V)
3.5
• As can be seen loading
produces little difference in
response.
3
CH3
2.5
CH4
2
1.5
1
0.5
0
-1.00E-04
0.00E+00
1.00E-04
2.00E-04
3.00E-04
4.00E-04
time (s)
switching off no 2 (with load)
5
4.5
4
output (V)
3.5
3
CH3
2.5
CH4
2
1.5
1
0.5
0
-1.00E-04
0.00E+00
1.00E-04
2.00E-04
time (s)
3.00E-04
4.00E-04
Brookhaven Over-voltage and Slow Control
Bypass Protection Circuit
•
•
•
•
•
Shown below are the segments of the circuit.
The green circle is the dummy module
Strategy is that module should have both slow control and real time protection. Also, when bypass
is used the voltage drop across the module should be as small as possible.
The red circle is the low resistance slow control bypass. DCS enable/disable through a serial
addressable latch. The zener shown protects the gate of the MOSFET from both under and over
voltage. Less than 100 mV voltage drop is achievable
The blue circle is the over-voltage protection latch. At a selected voltage (e.g. 2.5 V) the zener
conducts and turns the both bipolar transistor pair latch and MOSFET on. This provides real time
protection
Brookhaven Over-voltage and Slow Control
Bypass Protection Circuit
•
•
•
•
Shown are 3 simulated modules with the
Brookhaven proposed protection on each
module
Again, the blue circle is the over-voltage
protection which turns on when the voltage rises
above a set point. The turn on time has been
measured as being on the order of 100 ns. The
circuit latches and requires a power recycle to
reset. The overall low voltage achievable in this
approach is about 0.6-0.7 volts.
The over-voltage protection circuit has been
prototyped with discrete components as shown
in the picture to the right of the circuit on a Euro.
The red circle and adjacent components are the
slow control protection circuit. This was tested a
3 module serial chain for characteristics. And
achieves a low voltage across the module of
about 100 mV
Slow Control Bypass Response When Switched
•
Shown is the slow control “bypass
on” response (top plot) and
“bypass” off response (bottom
plot) for the middle of 3 modules
•
The orange curve is the voltage
across a module and the green
curve is voltage on the gate of the
bypass MOSFET with respect to
the ground of the serial chain.
•
The module voltage is pulled
down to about 100 mV when the
bypass is enabled.
•
The top and bottom modules show
a similar response to this.
Slow Control Bypass Response in Adjacent
Module
• This is similar to the previous
slide except that the orange
curve shows the voltage
across the top module when
the middle module is switched.
• As shown there is a small
perturbation that occurs on
adjacent modules when a
module is switched on or off.
• The bottom module shows a
similar perturbation to the top
module.
Bypass MOSFET Vishay 1450
VTHR Tuning
•
•
•
•
The MOSFET has a gate
threshold voltage that is too large
for this application
This was adjusted by exposing the
MOSFET to gamma radiation to
shift it to a lower value
Shown is a curve showing the
response with vg = vd at different
gamma doses. At 500 krad the
value is about right.
This approach is used only to tune
the circuit in the prototype and
would not be used in the final
design.
With this the over-voltage circuit
can lower the voltage across the
module to 0.6 – 0.7 volts
Vishay 1450 Mosfet
vg = vd
1.2
100 krad
1.0
id (amps)
•
200 krad
0.8
300 krad
0.6
400 krad
0.4
500 krad
unirradiated
0.2
0.0
0
0.5
1
vg (volts)
1.5
Future Effort
•
Can make prototype version of this circuit using discrete
commercial components and optimizing for size. These
could be used in stave prototypes (Stave 09?)
•
Just beginning to investigate how much of circuit can be
incorporated in a single chip. Need to determine which
processes are available and what components and
component characteristics are of available (e.g. FET
breakdown and turn on thresholds).