Miscellaneous active electrical nonlinear devices – circuits – and – Gating – Utilizing three or more electrode solid-state device
Reexamination Certificate
2000-03-16
2001-02-27
Cunningham, Terry D. (Department: 2816)
Miscellaneous active electrical nonlinear devices, circuits, and
Gating
Utilizing three or more electrode solid-state device
C327S437000, C327S170000
Reexamination Certificate
active
06194951
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method for driving an integrated power output stage for switching loads connected to terminals of a voltage source. The invention also relates to a device for carrying out this method.
U.S. Pat. No. 5,315,174 discloses such a device for driving a load using a power output stage, in which a steepness of switching edges of the power transistor connected in series with the load to the terminals of a voltage source can be adjusted, on the basis of external control signals (which can also be stored), to be either steep at first and then shallower, or just shallow.
U.S. Pat. No. 5,568,081 discloses a device for driving a power output stage, in which the steepness of the turn-on and turn-off edges of the power transistors can be adjusted on the basis of external control signals. In addition, during periods of the output signal when the di/dt derivative for output current against time is large, shallow turn-on and turn-off edges can be chosen, and during periods of the output signal when the di/dt derivative for output current against time is small, steep turn-on and turn-off edges can be chosen.
U.S. Pat. No. 5,617,051 discloses a device for limiting voltage overshoot, in which the change or rate of change in the output voltage is measured. If predetermined values are exceeded, the output is fed back to the drive circuit so that the overshoot behavior is reduced as a result of the switching edges being flattened.
Power output stages are used in large numbers particularly in the field of engine control in motor vehicles. Depending on the application, the individual loads are driven sporadically, at a fixed driving frequency or depending on engine speed, with switching times which have to be adhered to more or less exactly. The more precisely the switching times have to be adhered to, the steeper the rising and falling edges required for the output stage switches directly switching the load; for less time-critical applications, freewheeling diodes are connected in parallel with the loads.
If the loads are driven on the basis of engine speed, in which case exact turn-on times, for example for fuel injection or ignition, are usually required, then the interference spectrum produced by the steep edges of the switching signals has a broad bandwidth. Loads driven at a fixed frequency form a fixed interference frequency and are therefore more critical.
Each type of driving for these loads requires specially matched power output stages. The large number of power output stages required results in that integrated multiple drivers are used, e.g. quadruple or octuple drivers, and, in the near future, ICs with even more drivers as a result of higher integration density, which need to be matched to the particular application using external components, at high cost. In this context, it is common practice to make the switching edges of the power switches just as steep as the application requires to keep the radiated interference as low as possible.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a device for driving an integrated power output stage which overcome the above-mentioned disadvantages of the prior art methods and devices of this general type, which allows the power output stage itself to recognize whether the load which is to be switched needs to be driven with shallow or steep switching edges, and to set itself to this.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method for driving an integrated power output stage having a limit switch for switching a load connected to terminals of a voltage source in series with the limit switch, a control unit generates control signals for driving the integrated power output stage, the method which includes:
measuring a voltage at a junction point between the load and the limit switch if the load is disconnected resulting in a measured voltage;
comparing the measured voltage with a predetermined threshold value resulting in a comparison result;
storing a value associated with the comparison result over a course of operation;
turning on and off the limit switch to have shallow turn-on and turn-off edges with a first predetermined current when the value has a first, low signal level; and
turning on and off the limit switch to have steep turn-on and turn-off edges with a second current if the value q has a second, high signal level, the second current being a higher current than the first predetermined current.
In accordance with an added feature of the invention, there is the step of connecting a freewheeling diode between the junction point and a positive terminal of the voltage source for limiting the voltage at the junction point.
With the foregoing and other objects in view there is further provided, in accordance with the invention, in combination with a control unit supplying a control signal and having an on-board voltage supply with a positive terminal and a negative terminal, a device for switching a load, including:
a limit switch having a control input and connected to the load;
a first driver having two driver switches containing a first driver switch and a second driver switch connected in series with each other at a junction point and connected between the positive terminal and the negative terminal of the on-board voltage supply, the driver switches having control inputs receiving the control signal and the junction point of the driver switches is connected to the control input of the limit switch;
a comparator having a first input connected to a junction point between the load and the limit switch, a second input receiving a threshold value, and an output;
an RS flipflop having a Set input connected to the output of the comparator, a Reset input connected to the negative terminal, and an output;
a switching logic circuit having a NAND gate with a first input, a second input, and an output, an AND gate with a first input, a second input, and an output, and an inverter with an input and an output, the output of the RS flipflop connected to the first input of the NAND gate and the first input of the AND gate, and the control signal received by the second input of the AND gate directly and to the second input of the NAND gate via the inverter; and
a second driver having two driver switches, containing a first driver switch and a second driver switch connected in series between the positive terminal and the negative terminal of the on-board voltage supply, the first driver switch of the second driver having a control input connected to the output of the NAND gate, the second driver switch of the second driver having a control input connected to the output of the AND gate, and a junction point between the two driver switches of the second driver connected to the control input of the limit switch.
In accordance with an added feature of the invention, the limit switch and the driver switches of the first driver and the second driver are integrated MOSFET switches.
In accordance with another feature of the invention, the first driver switch of the first driver and the first driver switch of the second driver are P-channel MOSFETs, and the limit switch, the second driver switch of the first driver, and the second driver switch of the second driver are N-channel MOSFETs.
In accordance with an additional feature of the invention, there are a plurality of resistors, the driver switches of the first driver and the second driver are bipolar transistors, and each of the bipolar transistors have one of the resistors connected in series with it.
In accordance with a further added feature of the invention, there are a plurality of current sources, the driver switches of the first driver and the second driver are bipolar transistors, and each of the bipolar transistors have one of the current sources connected in series with it.
In accordance with another additional feature of the invention, the control unit has an output delivering an output signal, and the Set input of the RS fl
Cunningham Terry D.
Greenberg Laurence A.
Lerner Herbert L.
Siemens Aktiengesellschaft
Stemer Werner H.
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