High side supply shut down circuit

Details High side supply shut down circuit High side supply shut down circuit

2001-06-22

2003-10-14

Berhane, Adolf D. (Department: 2836)

Electricity: electrical systems and devices

Safety and protection of systems and devices

Circuit interruption by thermal sensing

Reexamination Certificate

active

06633475

ABSTRACT:

TECHNICAL FIELD
This invention relates to low cost high side supply shut down circuits, and, more particularly, to circuits that can deactivate a centralized high side supply. The invention may be used with high side supplied electrical loads, e.g. pressure regulators, solenoid valves, etc. Industrial Applicability includes use in vehicle electro-hydraulic transmission modules to respond in the event of a system-required supply shut down.
BACKGROUND
In some electronic or electromechanical systems, there are instances in which it is desired to protect an overall system from the adverse impact of an output load driver failure. An output load driver failure or malfunction means, in particular, the inability to control the output load driver. The only way to regain limited control over the system is to deactivate the central load supply, which permits bringing the overall system into a defined and safe mode. The malfunction of an output load driver could have devastating consequences on the overall system with the effect of damaging the downstream load, e.g. hydraulic sub-components, or other equipment. Such driver malfunctions may significantly damage other ancillary equipment (e.g. clutches), or may be dangerous to a human operator of the equipment.
This invention relates to high side supply shut down circuits, and, more particularly, to circuits that can deactivate a centralized high side supply, used with high side supplied electrical loads. Particularly useful examples include, e.g., pressure regulators, solenoid valves, etc., as part of a vehicle electro-hydraulic transmission module in the event of a system requested supply shut down. Such electro-hydraulic transmission modules have and will have everyday use in automobiles, trucks, buses, motorcycles, watercraft, airplanes, spacecrafts, and other engine driven vehicles.
FIG. 1
is a schematic diagram illustrating a prior art example of a solution to activate and deactivate a central supply voltage. Supply voltage
102
is connected between ground and the high side of switch
108
. The low side of switch
108
is connected to loads
118
,
122
,
126
. The first load
118
is connected in series to the low side of switch
108
. Transistor
116
is connected to the load
118
and to subsequent circuitry or, as indicated, to ground potential. The second load
122
is connected in series with switch
108
, as well, and the enabling transistor
120
couples load
122
to ground potential. Similarly, load
126
is connected in series on the low side of switch
108
and is enabled by transistor
124
to ground potential. The high sides of the load circuits
118
,
122
, and
126
are connected with each other and will be receiving power or no power depending on the operation of switch
108
. The enabling inputs
140
,
142
,
144
to transistors
116
,
120
,
124
would include any typical input, depending upon the environment in which the circuit is utilized and the required tasks to be undertaken.
Connected to the high side (supply voltage) of the relay switch
108
(also called relay terminals) is relay coil
80
that activates the relay switch
108
. The low side of relay coil
80
is connected to transistor
114
. In enabled operation, current would flow through relay coil
80
and through transistor
114
. The current through the relay coil
80
operates to close switch
108
(or here, the relay terminals
108
). With terminals
108
closed, power is supplied to the load circuits
118
,
122
, and
126
. In a predetermined sequence, if a deactivation signal is applied to the input
148
of transistor
114
, transistor
114
will be inactivated, thereby interrupting the current flow through relay coil
80
. When this current flow is interrupted, terminals
108
open and interrupt the power on loads
118
,
122
, and
126
. The deactivation or activation signal that can be applied to input
148
of transistor
114
is based on a pre-determined strategy or paradigm generated from the diagnostics and control module
160
(e.g. micro-controller or other electronics). If, for example, transistor
116
fails, which could be determined by the diagnostics feedback signal
150
and is not able to deactivate load
118
, the diagnostics and control module
160
will send a deactivation signal to the input
148
of transistor
114
. Transistor
114
will then interrupt the current flow through relay coil
80
. This will interrupt (open) the relay terminals
108
and consequently the power supply for all loads including load
118
, which was uncontrollable by transistor
116
. The same case example can be exercised regarding transistor
124
with the related feedback signal
152
, and transistor
120
with feedback signal
154
. In addition to the output driver feedback lines, the system has a feedback
156
for the actual supply voltage to the loads and a feedback
162
measuring the actual voltage
102
on the high side of the relay terminals. The feedback line
158
allows a plausibility check between the status of the relay terminals
108
and the drive status of the relay coil
80
. In case of an activated relay coil
80
, the low side feedback signal
158
of the relay coil
80
has to be plausible with the high side feedback signal
162
of relay terminals
108
and the low side feedback signal
156
of relay terminals
108
and vice versa.
FIG. 2
is a second prior art supply malfunction load protection strategy similar to that of the prior art solution in FIG.
1
. In
FIG. 2
, a high side semiconductor switch control circuit
86
(also called a field effect transistor, or FET) is substituted for the relay coil
80
and the relay terminals
108
in FIG.
1
. Instead of terminals
108
, as in
FIG. 1
, the drain source path of FET
86
is utilized in series with the supply voltage. Instead of relay coil
80
, as in
FIG. 1
, the gate of FET
86
is utilized as control input. In case of a shut down scenario, high side switch control circuit
86
would receive a disabling signal on control line
148
. With this disabling signal
148
, the power flow to loads
118
,
122
,
126
would be interrupted. Due to the non-existence of a separate drive circuit (coil
80
, as in
FIG. 1
) and switch circuit (terminals
108
, as in FIG.
1
), the feedback line
158
of
FIG. 1
is not required.
While the circuitry of
FIGS. 1 and 2
have been shown in the prior art, these circuits have significant drawbacks. Specifically, in automotive or other vehicle control systems such prior art solutions are based on more expensive semiconductor high side switches or relays that are not feasible for hybrid or surface mounted technology applicable to automotive controllers. High side switches require a charge pump circuit, which makes them cost ineffective and requires space on a hybrid or printed circuit board. Historically, the need for a redundant activation/deactivation path (relay solution,
FIG. 1
or high side driver circuit solution,
FIG. 2
) in automotive controllers was driven by the need to deactivate a faulty low side driver. The goal of such deactivation was to avoid damage to the attached external circuitry, i.e., attempting to limit repair to replacement of the automotive controller. However, that approach is no longer feasible because of upcoming integration of automotive controllers with the formerly external circuitry into non-repairable units. As a result of the circuit integration, the deactivation functionality can be reduced to a one-time malfunction event handling with the entire integrated circuit/controller unit being replaced. Damage to the downstream equipment (e.g. hydraulic sub-components) is no longer critical under these conditions. The goal of this deactivation strategy, in the case of an output driver malfunction, is to avoid devastating situations to other ancillary equipment (e.g. clutches), or danger to a human operator of this equipment.
Accordingly, there is a need in the art for an improved power supply shut down circuit that is suitable for surface mounting, and is cost effective, particularly for integrated cont

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