U.S. patent application number 13/715323 was filed with the patent office on 2016-11-24 for method and aparatus for high side transistor protection.
This patent application is currently assigned to CONTINENTAL AUTOMOTIVE SYSTEMS, INC.. The applicant listed for this patent is CONTINENTAL AUTOMOTIVE SYSTEMS, INC.. Invention is credited to Daniel Kisslinger da Silva.
Application Number | 20160341783 13/715323 |
Document ID | / |
Family ID | 48653896 |
Filed Date | 2016-11-24 |
United States Patent
Application |
20160341783 |
Kind Code |
A9 |
Kisslinger da Silva;
Daniel |
November 24, 2016 |
METHOD AND APARATUS FOR HIGH SIDE TRANSISTOR PROTECTION
Abstract
A method and apparatus for detecting a high energy event in a
transistor includes performing the steps of: monitoring a gate to
source voltage of a transistor during transistor start up,
continuously determining a derivative of the monitored gate to
source voltage with respect to time, and detecting a high energy
event when the derivative of the gate to source voltage exceeds a
predetermined threshold.
Inventors: |
Kisslinger da Silva; Daniel;
(Troy, MI) |
|
Applicant: |
Name |
City |
State |
Country |
Type |
CONTINENTAL AUTOMOTIVE SYSTEMS, INC. |
Auburn Hills |
MI |
US |
|
|
Assignee: |
CONTINENTAL AUTOMOTIVE SYSTEMS,
INC.
Auburn Hills
MI
|
Prior
Publication: |
|
Document Identifier |
Publication Date |
|
US 20130162284 A1 |
June 27, 2013 |
|
|
Family ID: |
48653896 |
Appl. No.: |
13/715323 |
Filed: |
December 14, 2012 |
Related U.S. Patent Documents
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Application
Number |
Filing Date |
Patent Number |
|
|
61579241 |
Dec 22, 2011 |
|
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Current U.S.
Class: |
1/1 |
Current CPC
Class: |
H03K 2217/0027 20130101;
G01R 19/16519 20130101; G01R 19/16576 20130101; G01R 31/2621
20130101; H03K 17/0822 20130101; G01R 19/16571 20130101 |
International
Class: |
G01R 31/26 20060101
G01R031/26 |
Claims
1. A method for detecting a high energy event in a transistor
comprising the steps of: monitoring a gate to source voltage of a
transistor during transistor start up; continuously determining a
derivative of the monitored gate to source voltage with respect to
time; and detecting a high energy event when the derivative of the
gate to source voltage exceeds a predetermined threshold.
2. The method of claim 1, further comprising the step of starting a
timer block when a gate driver switches said transistor on, and
delaying said step of detecting a high energy event when the
derivative of the gate to source voltage exceeds a predetermined
threshold until a blank time has elapsed.
3. The method of claim 2, wherein said blank time is a time period
for said derivative with respect to time to reflect said gate to
source voltage entering a Miller Plateau region.
4. The method of claim 2, wherein said blank time is less than a
time period required for said gate to source voltage to exit a
Miller Plateau region.
5. The method of claim 4, wherein said blank time is less than half
said time period required for said gate to source voltage to exit a
Miller Plateau region.
6. The method of claim 1, further comprising the step of switching
said transistor open when a high energy event is detected.
7. The method of claim 1, wherein said steps of monitoring a gate
to source voltage of a transistor during transistor start up and
determining a derivative of the monitored gate to source voltage
with respect to time are performed by a hardware
differentiator.
8. The method of claim 7, wherein said hardware differentiator is
an Op-Amp differentiator.
9. The method of claim 1, wherein said step of monitoring a gate to
source voltage of a transistor during transistor start up is
performed by a voltage probe and said step of determining a
derivative of the monitored gate to source voltage with respect to
time is performed by a software differentiator.
10. The method of claim 1, wherein said step of monitoring a gate
to source voltage of a transistor during transistor start up
comprises monitoring a metal-oxide semiconductor field effect
transistor (MOSFET).
11. The method of claim 10 wherein said MOSFET is a high side
transistor inside an electrical control unit.
12. The method of claim 10, wherein said MOSFET is in a direct
injection driver for a powertrain electrical control unit.
13. A transistor protection circuit comprising: a transistor
including a gate node, a source node, and a drain node; a
differentiator connected to said gate node at a first input and
said source node at a second input, wherein said differentiator has
a differential output; a timer block connected to said differential
output, wherein said timer block includes a control scheme operable
to cause said timer block to perform the step of detecting a high
energy event when the derivative of the gate to source voltage
exceeds a predetermined threshold after an initial blank time has
elapsed.
14. The transistor protection circuit of claim 13, wherein said
initial blank time is a time required for said differential output
to reflect a gate to source voltage of the transistor entering a
Miller Plateau region.
15. The transistor protection circuit of claim 14, wherein said
blank time is less than a time required for said gate to source
voltage of said transistor to exit said Miller Plateau region.
16. The transistor protection circuit of claim 15, wherein said
blank time is at least 50% shorter than said time required for said
gate to source voltage of said transistor to exit said Miller
Plateau region.
17. The transistor protection circuit of claim 16, wherein said
transistor is a metal oxide semiconductor field effect transistor
(MOSFET).
18. The transistor protection circuit of claim 13, wherein said
transistor is a high side input transistor for an electrical
control unit.
19. The transistor protection circuit of claim 18, wherein said
transistor is in a direct injection driver in a powertrain
electrical control unit.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
[0001] This application claims priority to U.S. Provisional
Application No. 61/579,157, which was filed on 22 Dec. 2011 and is
incorporated herein by reference.
TECHNICAL FIELD
[0002] The present disclosure is directed toward transistor
monitoring, and more specifically toward high-side Metal Oxide
Semiconductor Field Effect Transistor (MOSFET) monitoring for a
direct injection driver in a powertrain Electronic Control Unit
(ECU).
BACKGROUND OF THE INVENTION
[0003] Powertrain electric control units (ECUs) for vehicles, such
as cars, utilize high side transistors (transistors that switch a
high voltage side of a load) and low side transistors (transistors
that switch a low ground side of a load) to control the inputs to
and outputs from the ECUs. High amounts of energy can be dissipated
in a high side transistor during a high energy event, such as a
short circuit to ground or a battery fault causing a voltage spike.
Dissipation of the energy from the high energy event can damage the
high side transistor.
[0004] One currently used way to protect the high side transistor
from such an event is to utilize a sense resistor in series with
the high side transistor and monitor the voltage across the sense
resistor in real time using a voltage monitoring circuit. When the
voltage monitoring circuit detects a voltage in excess of a
predefined threshold, the high side transistor is turned off,
preventing excess power dissipation within the high side
transistor. This technique provides highly accurate results,
however the monetary and weight costs associated with utilizing an
appropriately sized sense resistor and voltage monitoring circuit
are cost prohibitive for some applications, such as vehicle control
units.
[0005] Another approach used to protect high side transistors from
a high energy event involves monitoring a drain to source node
voltage of the high side transistor. In this approach, when the
drain to source node voltage exceeds a predetermined threshold,
with the high side transistor is saturated, the monitor detects
that a high energy event is occurring and appropriate action is
taken to protect the transistor. Due to the nature of MOSFET type
transistors, however, there is a time period after receiving a
control signal turning the transistor on and before the transistor
is fully on or saturated. Within that time period the voltage
across the drain to source nodes of the transistor steadily
declines to zero volts, and during the switching on time period a
high energy event is not detectable across the drain to source
modes of the transistor. As a result, protection circuits cannot
respond to high energy events occurring during the switching time
period, and the high side transistor can be damaged.
SUMMARY OF THE INVENTION
[0006] Disclosed is a method for detecting a high energy event in a
transistor including the steps of: monitoring a gate to source
voltage of a transistor during transistor start up, continuously
determining a derivative of the monitored gate to source voltage
with respect to time, and detecting a high energy event when the
derivative of the gate to source voltage exceeds a predetermined
threshold.
[0007] Also disclosed is a transistor protection circuit including
a transistor having a gate node, a source node, and a drain node, a
differentiator connected to the gate node at a first input and the
drain node at a second input, wherein the differentiator has a
differential output, a timer block connected to the differential
output, wherein the timer block includes a control scheme operable
to cause the timer block to perform the step of detecting a high
energy event when the derivative of the gate to source voltage
exceeds a predetermined threshold after an initial blank time has
elapsed.
[0008] These and other features of the present invention can be
best understood from the following specification and drawings, the
following of which is a brief description.
BRIEF DESCRIPTION OF THE DRAWINGS
[0009] FIG. 1 illustrates an example direct injection driver
circuit for a powertrain electrical control unit including a high
side transistor protection scheme.
[0010] FIG. 2 illustrates a flowchart demonstrating a method for
identifying high energy events in a high side transistor.
[0011] FIG. 3 illustrates a graph demonstrating sample voltages and
currents across a high side transistor of a direct injection driver
circuit during standard operation of a powertrain electric control
unit operation.
DETAILED DESCRIPTION OF AN EMBODIMENT
[0012] FIG. 1 illustrates a direct injection driver circuit 10 for
a powertrain electrical control unit (ECU), including a protection
scheme for a high side transistor 20. The high side transistor 20
includes a drain node 20d, a gate node 20g and a source node 20s.
The drain node 20d is connected to a power source VBoost, and the
high side transistor 20 controls the connection of the power source
VBoost to a drain node of a second transistor 22 and a load 60. The
load 60 is fuel injector. A controller 30, including a gate driver,
is connected to the gate node 20g of the high side transistor 20,
and controls the operational state of the high side transistor 20
with a high gate driver output turning on the high side transistor
20 and a low gate driver output turning off the high side
transistor 20. A low side transistor 24 connects the load 60 to a
ground or neutral point. A similar or identical protection scheme
can be applied to the second transistor 22 to achieve the same
effect.
[0013] Also connected to the gate node 20g is one input of a
differentiator 40. A second input of the differentiator 40 is
connected to the source node 20s of the high side transistor 20.
This connection arrangement allows the differentiator 40 to measure
the gate to source voltage of the high side transistor 20 and to
output a derivative with respect to time of the measured gate to
source voltage. The output of the differentiator 40 is connected to
an input 52 of a timer block 50. The differentiator 40 includes an
operational amplifier 42, a resistor 44 and a capacitor 46 arranged
in a standard differentiator configuration. The timer block 50 also
receives a gate driver output as an input 54. The timer block 50 is
connected to the gate driver in controller 30, and includes an
output 56 that sends a warning signal to the controller 30 when a
high energy event, such as a short to ground or a battery fault, is
detected. The second transistor 22 can also be protected via a
similar protection circuit.
[0014] During operation of the circuit 10, the gate driver in the
controller 30 turns the high side transistor 20 on. The gate driver
output is also provided to the timer block 50 via timer block input
54, and the timer block 50 begins operating simultaneous to the
high side transistor 20 turning on (when the gate driver output
from the controller 30 goes high). When the high side transistor 20
initially turns on, the gate to source voltage of the high side
transistor 20 begins ramping up to a Miller Plateau region, and
then steadies off for the duration of the Miller Plateau region.
Once the duration of the Miller Plateau has elapsed, the gate to
source voltage of the high side transistor 20 begins climbing again
until it reaches a steady closed operating voltage. The
differentiator 40 provides a continuing derivative with respect to
time of the gate to source voltage of the high side transistor 20
with respect to time to the timer block 50 via input 52. When a
pre-defined blank time period has expired, the timer block 50
compares the derivative of the gate to source voltage of the high
side transistor 20 to a preset threshold and determines that a high
energy event is occurring if the derivative with respect to time
exceeds the threshold.
[0015] The derivative with respect to time of the gate to source
voltage of the high side transistor 20 reflects the rate of change
of the gate to source voltage. Thus, the derivative value of a
properly operating high side transistor 20 is at or near zero until
the end of the Miller Plateau period because the gate to source
voltage stays steady during the Miller Plateau. Alternatively, the
derivative value of a high side transistor 20 experiencing a high
energy event during the Miller Plateau is significantly above
zero.
[0016] The preset time period utilized in the timer block 50 before
which the derivative value is compared to a threshold is referred
to as the blank time, is defined during assembly of the circuit,
and is set to a time period that is shorter than the time period
from the gate driver turning the high side transistor 20 on to the
end of the Miller Plateau. In some examples, the blank time period
of the transistor protection scheme is less than half the time
period from transistor turns on until the end of the Miller
Plateau.
[0017] The illustrated differentiator 40 is a standard operational
amplifier (Op-Amp) differentiator and uses the capacitor 46 and the
resistor 44 to define the constants of the differentiator 40.
Alternate styles of differentiators, or alternate methods of
differentiating the gate to source voltage of the high side
transistor 20, can be used to the same affect and require minimal
alteration to the illustrated circuit. One example alternate that
can be used is a software based differentiator in the controller 30
and a standard voltage probe connected to the gate node 20g and the
source node 20s of the high side transistor 20.
[0018] FIG. 2 illustrates a flowchart demonstrating the method
performed by the circuit described above (and illustrated in FIG.
1) in greater detail. Initially, the gate driver in the controller
30 turns on the high side transistor 20 in a "switch on transistor"
step 110. Once the gate driver outputs the on signal, the timer
block 50 also begins a blank timer in a "Begin Timer Block" step
120 and the voltage differentiator 40 begins monitoring the
gate-source voltage in a "Monitor and derivate gate to Source
Voltage" step 130. Both the "Begin Timer Block" step 120 and the
"Monitor and derivate gate to Source Voltage" step 130 begin
simultaneously. The blank time is an amount of time required for
the derivative of the gate to source voltage of the high side
transistor to reflect the Miller Plateau and to level off at
approximately 0. In addition to monitoring the drain-source voltage
of the high side transistor 20, the voltage differentiator 40 also
continuously determines a derivative with respect to time of the
monitored drain to source voltage in the "Monitor and Derivate gate
to Source Voltage" step 130. The derivative value (the output of
the differentiator 40) is passed to the timer block 50.
[0019] The timer block 50 continuously checks to determine if the
blank time period has elapsed in a "Has Blank Time Elapsed" step
150. If the blank time period has not elapsed, the method continues
monitoring the drain to source voltage in the monitor and derivate
gate to source voltage step 130.
[0020] When blank time has elapsed, the process compares the
continuous derivative with respect to time of the gate-source
voltage of the high side transistor 20 to a threshold in a "Compare
Gate--Source Voltage Derivative to Threshold" step 160. If the
threshold is exceeded in a comparison step 170, the controller 30
determines that a high energy event has occurred in a "High Energy
Event Detected" step 190. If, the threshold is not exceeded in
comparison step 170, the controller determines that no high energy
event is occurring in a "No High Energy Event Detected" step
180.
[0021] When a high energy event is detected by the controller 30,
an alert is created, and the controller 30 responds to the high
energy event in an "Alert and Respond" step 192. In one example
response to a high energy event, the high side transistor 20 is
immediately switched to an open mode. Switching the high side
transistor 20 open protects the high side transistor 20 from excess
energy dissipation by preventing any energy from passing through
the transistor 20, and extends the expected life cycle of the
transistor.
[0022] FIG. 3 illustrates a graph 200 demonstrating sample voltages
and currents across a high side transistor 20 during standard
operation of a powertrain electric control unit. The graph 200
includes a gate to source voltage section 202 and a drain to source
voltage and current section 204.
[0023] Illustrated in the gate to source voltage section is a gate
to source voltage 210 and a derivative 220 with respect to time of
the gate to source voltage 210. The X axis of the graph 200 starts
at T=0, where T is the time and T=0 is the initial time at which
the high side transistor 20 receives an on signal. When the high
side transistor 20 is initially switched on, at T0, the gate to
source voltage 210 begins ramping up to a Miller Plateau region 212
that is reached at T2. The Miller Plateau region 212 lasts between
T2 and T4, after which the gate to source voltage 210 begins rising
steadily to a closed region 214. The derivative 220 of the gate to
source voltage 210 is a high value until T2 when a Miller Plateau
region 222 is entered. Shortly after the Miller Plateau region 222
is entered, the derivative value 220 falls to almost 0, at T3, and
remains steady at almost 0 until T4, when the gate to source
voltage exits the Miller Plateau region 222. At T4, the derivative
value 220 rises until it evens out at the same value as the gate to
source voltage 210 in the closed region 214.
[0024] If, however, a high energy event occurs during the Miller
Plateau region 212, 222, the derivative value 220 will not fall to
near zero during transistor switch on, and will remain high
relative to the expected derivative valve. The gate to source
voltage of the transistor 20 during a high energy event is
illustrated as a dashed line 270. Thus, the timer block 50 can
compare the derivative value 220 to a threshold shortly after T3,
where the derivative value 220 has dropped corresponding to the
Miller Plateau. As can be seen in the graph 200, the time period
from T0 to T3(time and period 240) is significantly shorter than
the time period from T0 to T4 (the switch on time period 230). In
some examples, the time period from T0 to T3 (time period 240) is
less than half the time period from T0 to T4 (the switch on time
period 230). Thus, the disclosed protection scheme can detect a
high energy event occurring during switching significantly earlier
than a system using the drain to source voltage, which cannot
detect a high energy event until after the high side transistor 20
is fully on.
[0025] The drain to source voltage and current section 204
illustrates the voltage measurements, and the current measurements
of the drain to source nodes 20d, 20s of the high side transistor
20. As can be seen, in the Miller Plateau region 262, the drain to
source voltage is steadily declining until it reaches close to 0
volts at T4, when the Miller Plateau region is exited. The drain to
source current 260 is at 0 amps when the transistor 20 is closed
and begins ramping up from 0 at T1. A high energy event occurring
during the switch on time period 230 (between T0 and T4) induces a
current spike. However, as the current is ramping up during that
time period, the current spike is not noticed by threshold
detection and the drain to source voltage can not be used to detect
high energy events before the transistor is fully on.
[0026] While the above disclosure is described with regards to high
side transistor protection for a direct injection driver electrical
control unit, it is understood that similar protection schemes can
be applied to any MOSFET, and are not limited applications within a
direct injection driver. Similarly the protection scheme is
likewise functional to protect low side transistors from high
energy events occurring within an ECU, or high energy events
originating on a neutral line. Thus, the disclosed protection
scheme can be utilized in conjunction with any MOSFET with minimal
modification and still fall within the instant disclosure.
[0027] It is further understood that any of the above described
concepts can be used alone or in combination with any or all of the
other above described concepts. Although an embodiment of this
invention has been disclosed, a worker of ordinary skill in this
art would recognize that certain modifications would come within
the scope of this invention. For that reason, the following claims
should be studied to determine the true scope and content of this
invention.
* * * * *