DE102010015095A1 - Driver circuit for controlling surge in supply voltage to inductive load e.g. motor of motor car, has over-voltage detection circuits detecting voltage surge and controlling pre-driver to switch off low-side switch - Google Patents

Abstract

The circuit (1) has an integrated circuit (3) receiving a voltage (UBAT) and comprises a voltage generator (32) for generating another voltage (V5) whose absolute value is less than the former voltage. A low-side switch (43) is provided between a load (71) and a ground terminal (33). A pre-driver (5) selectively switches and turns off the low-side switch. Two over-voltage detection circuits (31, 51) detect a surge of the latter voltage and control the pre-driver to switch off the low-side switch when the voltage is detected as surge.

Description

The invention relates to a driver circuit and an assembly of a driver circuit and a load. Particularly in the case of vehicles, care must be taken that the functions of, for example, a transmission or a motor control reliably switch off in the event of overvoltage of the supply voltage.

In the patent EP 1 155919 B1 It is described that there are two different power grids in a vehicle, one operating at a voltage of 12V and one at a voltage of 42V. However, there is a particular risk that short circuits will occur between the two networks, causing the lower voltage network to experience an overvoltage affecting the functionality of the components connected to the lower voltage. In this case, the components are destroyed or malfunction. As a result, it can not be predicted which signals the component outputs at its outputs. If one of these defective components due to the overvoltage is a driver, for example a solenoid valve, this can lead to the solenoid valve switching uncontrollably, as a result of which malfunctions, for example of the drive or of the transmission, occur.

It is for example from the WO 2001/061855 known, in a chip, also called integrated circuit to provide an overvoltage protection. This overvoltage verifies that the supply voltage exceeds a threshold to turn off the output driver.

However, the problem arises that an overvoltage protection circuit on the chip can also be defective, which nevertheless leads to malfunction.

The WO 2005/106230 A1 shows an electronic control device in which a microcontroller is used and an operating voltage is monitored. Two voltage monitoring devices are provided, which operate in different voltage ranges, so that the output stage can be switched off reliably. An embodiment is described according to which one of the voltage monitors is provided in an output stage of an engine control unit. Nevertheless, it can happen that, especially with rapidly increasing operating voltage, there is no need for a desired switch-off.

The object of the invention is to provide a driver circuit for a load that allows safe switching off in case of overvoltages.

This object is solved by the subject matter of the independent claim. Advantageous embodiments emerge from the subclaims.

According to the invention, a driver circuit for a load is provided, wherein the driver circuit includes a first integrated circuit. The first integrated circuit receives a first voltage and has a voltage generator for generating a second voltage. The amount of the second voltage is smaller than the amount of the first voltage. The driver circuit also includes a power switch between the load and a first voltage terminal and a predriver provided in a second integrated circuit. The pre-driver is provided for selectively turning on and off the circuit breaker.

The driver circuit also includes a first overvoltage detection circuit in the first integrated circuit for detecting an overvoltage of the second voltage and for driving the pre-driver in the event of a detected overvoltage such that the pre-driver turns off the power switch.

A second overvoltage detection circuit is provided in the pre-driver for detecting the overvoltage of the second voltage.

The driver circuit has the advantage that, even if the first integrated circuit fails, it can still be ensured that the power switch is reliably switched off in the event of an overvoltage. It is advantageous to provide this second overvoltage detection circuit in the predriver since this ensures a short signal path between the overvoltage detection circuit and the power switch. There is thus no longer the danger that the signal path between the second overvoltage detection circuit and the power switch will become inoperative with a rapid increase of the voltage before the switch-off signal has passed from the second overvoltage detection circuit to the power switch. In addition, the arrangement immediately before the circuit breaker is advantageous because spikes, i. H. short signal peaks are avoided during shutdown. This prevents the circuit breaker opens for short pulses, whereby the driven device, for example, a transmission switch is activated for a short time, which would be detrimental to the wear of the gearshift switch.

It is also possible to fabricate the predriver in a more robust technology than the technology of the first integrated circuit, so that even if very large overvoltages, if the first integrated circuit is already destroyed, the circuit breaker is still safely switched off.

In one embodiment, a second power switch is provided between the load and a second terminal of the first voltage. Even in this configuration with a high-side switch and a low-side switch, in the case of a normal voltage, d. H. no overvoltage, the load is completely disconnected from the first voltage.

If the first overvoltage detection circuit and the second overvoltage detection circuit have substantially the same threshold for detecting an overvoltage, it will not lead to different results of overvoltage detection with only slight overvoltage. In essence, this means that the overvoltage detection circuits have the same nominal value, although there may be small deviations due to production.

In one embodiment, the switching threshold of the first overvoltage detection circuit and the switching threshold of the second overvoltage detection circuit are adjustable. This makes it possible to compensate for production-related deviations of the switching thresholds.

In one embodiment, in a third integrated circuit, a further pre-driver for the second power switch is provided, wherein in the further pre-driver, a third overvoltage detection circuit is provided for driving the further pre-driver in the event of a detected overvoltage of the second voltage such that the second pre-driver the second power switch off.

This configuration is particularly advantageous if the load is to be switched to a high-impedance state in the event of an overvoltage.

In a preferred embodiment, a further integrated circuit for driving the pre-driver is provided at normal voltage of the second voltage. This has the advantage that a microcontroller with a variety of functions and with a large computing capacity can be used to perform the control of the load, such as a solenoid valve.

Preferably, the predriver has a higher voltage with respect to the second voltage than the first integrated circuit. This ensures the dielectric strength even at very high overvoltages.

The invention also relates to an assembly of a driver circuit according to one of claims 1 to 8 and a load which is driven by this driver circuit. This load has, for example, a magnetic switch. Magnetic switches have an impedance with a high inductive component.

Finally, the invention also relates to the use of an assembly according to the invention in a motor vehicle, wherein the first voltage is provided by the vehicle battery. Particularly here, the use of the assembly is particularly advantageous because the vehicle should switch as safely as possible in a safe state even with short circuits between different power supply networks.

In summary, two independent monitoring units monitor the second voltage and detect overvoltage conditions. A first overvoltage block operates in a manner of a standard voltage range, for example between 5 and 7 volts, if the second voltage is nominally 5 volts. The second overvoltage block operates in an extended range of up to, for example, 20V. This means that this block operates up to 20V when all other blocks have already stopped working and are destroyed or in an unknown state.

In general, better behavior in the event of a fault is provided in safety-relevant applications such as drive or gearbox.

The invention will now be shown by way of example with reference to the figure.

1 shows a circuit diagram of a circuit with inductive loads and the associated driver circuit for the inductive loads.

1 shows a circuit diagram of a circuit 1 , the inductive loads 71 and 72 and has the associated driver circuit. The driver circuit includes a microcontroller 2 , a system basic chip 3 , a first predecessor 5 , a second predriver 6 , a low-side switch 43 , a first high-side circuit 40 and a second high-side circuit 44 , The driver circuit is powered by a first voltage UBAT, which is between a first connection 34 and the ground connection 33 is operated. The connection 34 is connected to a first pole of a vehicle battery of a vehicle while the ground connection 33 is connected to the second pole of the vehicle battery. The vehicle battery has a nominal voltage of 12 V, but the battery voltage UBATT can be between 6 V and 40 V. The high Voltages arise in the event of a sudden disconnection of the battery, whereby inductances in the vehicle electrical system reduce their energy.

The system base chip 3 is constructed as an integrated circuit which serves as a central control circuit and power supply circuit for the driver circuit. The system base chip 3 receives the first voltage UBAT and generates it in a generator 32 three supply voltages for the remaining driver circuit. On line V5 becomes a potential of the nominal value of 5V, on line V33 becomes a potential of the nominal amount of 3.3V and on line V15 a potential of nominal value of 1.5V is output. In addition, the system basic chip is 3 via a SPI (Serial Peripheral Interface) bus to the microcontroller 2 connected. The system base chip 3 also generates a signal RST C for generating a reset of the microcontroller 2 and a signal NDDRV for disabling the low-side switch 43 and the high-side circuits 40 and 44 ,

Unless otherwise indicated, all potentials are given in relation to ground potential. The voltage between the line V5 and the ground is referred to as voltage U5.

An error occurs if there is a short circuit between the connection 34 and line V5 is coming. In the system base chip is an overvoltage detection circuit 31 provided that checks if the voltage U5 between the line V5 and the ground 33 is greater than 5.2V. The system base chip 3 is implemented as an integrated circuit in a BCD (Bipolar, CMOS, DMOS) technology. This technology is functional against overvoltages of voltage U5 to 7V. For voltages greater than 7 V, it can no longer be guaranteed that the system base chip 3 still outputs the correct output signals. For large overvoltages, the system basic chip 3 even permanently damaged.

The microcontroller 2 receives via supply lines V5, V33 and V15 respectively supply potentials of 5 V, 3.3 V and 1.5 V. These supply potentials and the ground potential uses the microcontroller 2 for the supply of its circuits with electrical energy. The microcontroller 2 calculates the times for opening and closing the solenoid valves 71 and 72 and accordingly outputs the control signals DRVH and DRVL.

The first predriver 5 implemented as an integrated circuit receives the control signal DRVL which is basic from the system 3 output control signal NDDRV and the power supply potential 5 V. The first predriver 5 includes a surge detection circuit 51 as well as an AND gate 52 , The first predriver 5 uses the power supply potential 5 V and the ground 33 as supply voltage. At the same time, in the overvoltage detection circuit 51 checks if voltage U5 is above 5.2V.

If the voltage is below, the overvoltage detection circuit will give 51 at their exit 511 a high potential. Otherwise, if an overvoltage is detected, the overvoltage detection circuit is present 51 at their exit 511 a low potential. This also gives the AND gate 52 a low potential on the output LDRV of the pre-driver 5 out. Because the output LDRV of the pre-driver 5 directly to the gate of the low-side switch 43 is connected, the low-side switch turns off 43 out.

The provision of the overvoltage detection circuit 51 in the first predriver 5 has the advantage that a safe switch-off is guaranteed, even if the supply voltage rises rapidly. Otherwise there would be a danger that the circuits on the signal path between the overvoltage detection circuit 51 and the low-side switch 43 are already broken before the low-side switch 43 was turned off. In addition, spikes are at the gate of the low-side switch 43 avoided.

In addition to the SPI bus (Serial Peripheral Interface), the system basic chip can also support other buses such as For example, support the CAN (Controller Area Network) or a LIN (Local Interconnect Network) bus.

The voltage U5 is particularly critical to the functioning of the driver circuit. For this purpose, the voltage U5 must be monitored for a possible undervoltage. The system base chip monitors 3 in that the voltage U5 does not become less than 5 V-10%. In addition, the voltage U5 must be checked for overvoltage. This is done in the system base chip 3 with the help of its overvoltage detection circuit 31 , If the system base chip 3 detects that overvoltage is present, the signal NDDRV is connected in such a way that with the help of the predriver 5 and 6 the high-side circuits 40 and 44 and the low-side switch 43 turned off.

The microcontroller 2 works only up to a supply voltage of 5.5 V. If the voltage U5 exceeds this value, it is very likely that the microcontroller 2 is destroyed and thus is then in an unknown state. With the help of the system base chip 3 the drivers are high-side circuits 40 . 44 and low-side switches 43 shut down to ensure that all outputs of the circuit 1 be switched off. When switching off, there may still be energy in the magnetic switches 71 and 72 are located. But this energy will come shortly after the low-side switch turns off 43 consumed so that thereafter the system is in a safe state.

The second predriver 6 contains an AND gate 61 and a drive logic 62 , The second predriver 6 is supplied by the voltage U5. The AND gate 61 receives the control signals DRVH from the microprocessor 2 and the control signal NDDRV from the system base chip 3 , If both provide high potential, the AND gate provides 61 at its output EN also a high potential. Otherwise, there is a negative potential at the output EN. The logic unit 62 controls the outputs of the pre-driver HDRV1, HDRV2 and RBP.

The high-side circuit 40 contains a high-side switch 42 and a battery circuit breaker 41 , The same applies to the high-side circuit 44 a high-side switch 46 and a battery circuit breaker 45 on. The high-side switches 42 and 46 as well as the battery protection switches 41 and 45 are each formed as NMOS transistors. The battery circuit breaker has the function of a Reverse Battery Protection (RPB).

The source and the bulk of the battery circuit breaker 41 are with the connection 34 while its drain connects to the drain of the high-side switch 42 is connected and its gate to the output RBP of the pre-driver 6 connected is.

The gate of the high-side switch 42 is from the HDRV output of the pre-driver 6 controlled. The source of the high-side switch 42 is with a first connection 711 of the magnetic switch 71 connected. The second connection 710 of the magnetic switch 71 is with the drain of the low-side switch 43 connected, its source and bulk with the mass 33 are connected. The gate of the low-side switch 43 is from the LDRV output of the pre-driver 5 driven. The source and the bulk of the battery circuit breaker 45 is with the connection 34 connected while the drain of the battery circuit breaker 45 with the drain of the high-side switch 46 connected is. Source and bulk of the Hight-Side-Switch 46 are with a first connection 721 of the magnetic switch 72 connected. The gate of the high-side switch 46 is with the output HDRV2 of the pre-driver 6 connected.

The second connection 720 of the magnetic switch 72 is also connected to the drain of the low-side switch 43 connected.

The low-side switch 43 thus serves as a common low-side switch for all solenoid valves. By changing the current through the solenoid valves 71 a magnetic field is generated which opens or closes the valve. The magnetic switches 71 and 72 have an impedance whose size fraction is due to the inductance.

In another embodiment, not shown in the figure, two further solenoid valves are connected, which are each driven by a further high-side circuit. However, the second connection of these respective solenoid valves is in each case connected to the drain of the low-side switch 43 connected.

The overvoltage detection circuit 51 also detects an overvoltage of the voltage U5. The switching threshold is also at 5.2 V. The switching thresholds of the overvoltage detection circuits 51 and 31 may also be set between 5.2 and 5.5 V in further embodiments.

The first predriver 5 is made in such a technology that it works even up to 20V. The overvoltage detection circuit 51 can be in the same technology as the overvoltage detection circuit 31 be realized. However, make sure that the pre-driver 5 Total up to 20 V works. If there is a short circuit between the terminal 34 and the line V5 comes and thus the voltage between the line V5 and the ground rises to 15 V, for example, the first predriver is still functional and switches the low-side switch 43 via the signal LDRV.

In an extended overvoltage condition of a voltage greater than 7V on line V5, most likely all of the driver devices are down to the first predriver 5 and the high-side circuits 40 and 44 as well as the low-side switch 43 destroyed. As a result, the destroyed components are in an unknown state and it is not sure if the high-side circuits 40 and 41 are turned off. By switching off the common low-side switch 43 but ensures that the current path through the magnetic switch 71 and 72 is interrupted. After a brief dismantling of the still in the magnetic switches 71 and 72 Thus, no magnetic field can be rebuilt so that the magnetic switches are safely turned off.

In alternative embodiments, the overvoltage circuit is in the second predriver 6 ,

In further alternative embodiments, both are in the first predriver 5 as well as in the second predriver 6 Overvoltage detection blocks 51 ,

The low-side switch 43 and the high-side switches 40 and 44 are constructed of power transistors that can handle at least 46 V, and thus the maximum possible battery voltage.

LIST OF REFERENCE NUMBERS

1

circuit

2

microprocessor

3

System Basis Chip

5

first predecessor

6

second predriver

32

voltage generator

31

Overvoltage detection circuit

33

Dimensions

34

connection

40

High-side circuit

41

Battery breaker

42

High-side switch

43

Low-side switch

44

High-side circuit

45

Battery breaker

46

High-side switch

51

Overvoltage detection circuit

52

AND gate

61

AND gate

62

logic

71

first magnetic switch

72

second magnetic switch

511

output

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 1155919 B1 [0002]
• WO 2001/061855 [0003]
• WO 2005/106230 A1 [0005]

Claims (11)

Driver circuit for a load ( 71 ), comprising: - a first integrated circuit ( 3 ) receiving a first voltage (VBAT) and a voltage generator ( 32 ) for generating a second voltage (U5) whose magnitude is less than the magnitude of the first voltage (UBAT); - a first connection ( 33 ) and a second port ( 34 ) at which the first voltage (UBAT) is provided; - a circuit breaker ( 43 ) between the load ( 71 ) and the first connection ( 33 ); A pre-driver provided in a second integrated circuit ( 5 ) for selectively switching on and off the circuit breaker ( 43 ); A first overvoltage detection circuit ( 31 ) in the first integrated circuit ( 3 ) for detecting an overvoltage of the second voltage (U5) and for driving the pre-driver ( 5 ) in the event of a detected overvoltage such that the predriver ( 5 ) the circuit breaker ( 43 ) turns off; A second overvoltage detection circuit ( 51 ) in the predecessor ( 5 ) for detecting an overvoltage of the second voltage (U5). Driver circuit according to claim 1, characterized in that a second circuit breaker ( 42 ) is provided between the load ( 71 ) and the second connection ( 34 ). Driver circuit according to claim 2, characterized in that a second load ( 72 ) and between a first connection ( 721 ) of the second load ( 72 ) and the first connection ( 34 ) a third circuit breaker ( 44 ) is provided. Driver circuit according to one of claims 1 to 3, characterized in that the first overvoltage detection circuit ( 31 ) and the second overvoltage detection circuit ( 52 ) have substantially the same switching threshold for detecting an overvoltage. Driver circuit according to one of claims 1 to 4, characterized in that the switching threshold of the first overvoltage detection circuit ( 31 ) and the switching threshold of the second overvoltage detection circuit ( 51 ) are adjustable. Driver circuit according to one of claims 2 to 4, characterized in that in a third integrated circuit, a further predriver ( 6 ) for the second circuit breaker ( 42 ), wherein in the further predriver ( 6 ) a third overvoltage detection circuit is provided for driving the second pre-driver ( 6 ) in the event of a detected overvoltage of the second voltage such that the second predriver ( 6 ) the second circuit breaker ( 42 ) turns off. Driver circuit according to one of the preceding claims, characterized in that a further integrated circuit ( 2 ) is provided for driving the pre-driver ( 5 ) at normal voltage of the second voltage (U5). Driver circuit according to one of Claims 1 to 7, characterized in that the predriver ( 5 ) a higher withstand voltage with respect to the second voltage (U5) than the first integrated circuit ( 3 ) having. An assembly of a driver circuit according to any one of claims 1 to 8 and a load. Assembly according to claim 9, characterized in that the load ( 71 ) has a magnetic switch. Use of the assembly according to claim 9 or 10 in a motor vehicle, wherein the first voltage (UBAT) is provided by a vehicle battery.

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