Method and device for diving an integrated power output stage

• US 6,194,951 B1
• Filed: 03/16/2000
• Issued: 02/27/2001
• Est. Priority Date: 09/15/1998
• Status: Expired due to Fees

• Current Assignee: Continental Automotive GmbH (Continental AG)
• Original Assignee: Siemens AG
• Inventors: Allmeier, Franz
• Primary Examiner(s): Cunningham, Terry D.
• Application Number:
  US09/527,121
• Time in Patent Office: 348 Days
• Field of Search: 327/424, 327/434, 327/436, 327/437, 327/170, 327/374, 327/379, 326/87
• US Class Current: 327/424
• CPC Class Codes: H03K 17/04206 in field-effect transistor switches
• CPC Class Codes: H03K 17/167 using parallel switching arrangements

Abstract

A voltage U_A that can be measured at a junction point between a load and a limit switch when the load is disconnected is compared with a predetermined threshold value W. The limit switch is turned on and off with a predetermined current associated with shallow turn-on and turn-off edges when U_A<W, or is turned on and off with a higher current associated with steep turn-on and turn-off edges when U_A>W.

Claims

1. 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 comprises:

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 has a second, high signal level, the second current being a higher current than the first predetermined current.

2. The method according to claim 1, which comprises connecting a freewheeling diode between the junction point and a positive terminal of the voltage source for limiting the voltage at the junction point.

3. 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, comprising:

a limit switch having a control input and connected to the load;

a first driver having two driver switches including 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, said driver switches having control inputs receiving the control signal and said junction point of said driver switches connected to said control input of said limit switch;

a comparator having a first input connected to a junction point between the load and said limit switch, a second input receiving a threshold value, and an output;

an RS flipflop having a Set input connected to said output of said 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, said output of said RS flipflop connected to said first input of said NAND gate and said first input of said AND gate, and the control signal received by said second input of said AND gate directly and to said second input of said NAND gate via said inverter; and

a second driver having two driver switches, including 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, said first driver switch of said second driver having a control input connected to said output of said NAND gate, said second driver switch of said second driver having a control input connected to said output of said AND gate, and a junction point between the two driver switches of said second driver connected to said control input of said limit switch.

4. The device according to claim 3, wherein said limit switch and said driver switches of said first driver and said second driver are integrated MOSFET switches.

5. The device according to claim 4, wherein said first driver switch of said first driver and said first driver switch of said second driver are P-channel MOSFETs, and said limit switch, said second driver switch of said first driver, and said second driver switch of said second driver are N-channel MOSFETs.

6. The device according to claim 3, including a plurality of resistors, said driver switches of said first driver and said second driver are bipolar transistors, and each of said bipolar transistors have one of said resistors connected in series with it.

7. The device according to claim 3, including a plurality of current sources, said driver switches of said first driver and said second driver are bipolar transistors, and each of said bipolar transistors have one of said current sources connected in series with it.

8. The device according to claim 3, wherein the control unit has an output delivering an output signal, and said Set input of said RS flipflop is connected to the output of the control unit and receives the output signal.

9. The device according to claim 3, wherein the control unit has outputs supplying driving signals having an amplitude associated with a desired steepness for turn-on and turn-off edges of said limit switch, and said control input of said driver switches of said second driver are directly connected to the outputs of the control unit for receiving the driving signals having the amplitude for controlling the desired steepness for the turn-on and turn-off edges of said limit switch.