JPS60153522A - Circuit apparatus for connecting, interrupting and monitoring operation of electric load - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to the operative connection of an electrical load having a switching device controlled by a microcomputer with constant periodicity and variable pulse width control. , relates to a circuit device for interrupting and monitoring.

BACKGROUND OF THE INVENTION In a circuit arrangement known from DE 31 35 805 A1, an electrical load is connected via a high-power field-effect transistor, which simultaneously causes a current to flow through the load circuit. It is used as a current measuring device. In such a circuit arrangement, the field-effect transistors are connected intermittently depending on the current strength by a regulating circuit, in which case the control circuit reduces the switching-on period as the current strength of the load-current circuit increases. . In the case of a short circuit, the switching-on period is short and fast, ie it is selected so short that damage to the field-effect transistor is prevented. In this way, in the known circuit, the average value of the current strength is maintained at a predetermined value by means of the regulating circuit.

Problem to be Solved by the Invention The circuit arrangement described above can therefore only be used for loads which are either switched on at a given average current value or completely switched off. For loads, such as electromagnetic regulators, for example, for which it is desired to change the closing position continuously depending on the average value of the current, the known circuit arrangements cannot be used.

In the present invention, an electrical load is connected and disconnected which can be switched between an active state and a rest state, and at the same time can also be operated in any number of switching stages between an active connected state and a disconnected state. It would also be desirable to provide a monitoring circuit arrangement. A regulating element for a no-load speed regulator of an internal combustion engine that can be controlled in this way is already known from DE 32 23 168 A1, in which the regulating element is controlled by a microcomputer via a switching device. However, when the period of the control pulse of the microcomputer is constant, the ξ pulse width is changed to affect the operating position of the adjustment element.

Structure of the Invention The circuit arrangement according to the invention for connecting, disconnecting and monitoring an electrical load comprises: a) a measuring resistor of a load current circuit which takes out a measuring voltage which changes depending on the instantaneous value of the load current; Two threshold switches are provided which are supplied with the measuring voltage, one of which is adjusted to the maximum permissible current average value as an overload switching device, and the other threshold switch is adjusted to the maximum permissible current average value as a short-circuit switching device. b) The microcomputer interrogates the output state of the short-circuit switching device at a first point in time during each control period and controls the switching device when the switching device responds.
and C) the microcomputer interrogates the output state of the overload switching device during the control/ξ-rus period at a second point in time, and the switching device responds. Subsequent control ξ
The feature is that the .ξ lus width of the lus is reduced by a fixed value.

In an embodiment of the invention, when a short circuit occurs in the load current circuit, the cutoff signal of the short circuit switching device is processed by the microcomputer as follows, that is, in that case only the load
Although immediately cut off via the switching device, the microcomputer's monitoring signal (watchdog) generated with the control pulse is generated over the entire pulse width of the original control pulse in order to further monitor the execution of the program. It is very advantageous to do so.

Description of examples The invention will now be explained in more detail with reference to the illustrated embodiments.

In the exemplary embodiment shown in FIG. 1, an adjustment magnet 10 is provided as an electrical load for regulating the no-load speed of a diesel engine (not shown), which is represented by an inductance. The adjustment magnet 10 is connected to the positive terminal of the vehicle's electrical system. A diode 11 is connected antiparallel to the regulating magnet 10 in order to shunt the current if the regulating magnet 10 is interrupted. A transistor switching device 12 is connected in series to the adjusting magnet 10, and a control connection terminal 12'a of the transistor switching device is connected to a series resistor 1.
3 and the microcomputer 15 via the amplifier 14.
o jlill II output side 15a. The other control 1 output side 15b has a monitoring signal (watchdog)
The monitoring signal is used in a known manner (see DE 2903638 A1) to monitor the execution of a program in a microcomputer. A measuring resistor 16 is still connected downstream of the switching device 12, the connection terminal of the measuring resistor 16 facing away from the switching device 12 being connected to ANIS. In order to monitor the strength of the current in the regulating magnet 1o, i1 depends on the temporary value of the load current.
The measured voltage that drops across the 1+1 constant resistor 16 is connected to the connection terminal 16.
a to two comparators 17 and 18 which are operated as threshold switches. In that case, a predetermined reference voltage is applied to the positive input of the comparator. The two reference voltages are provided by a voltage divider 19, in which one partial resistance 19a is connected to a positive potential and another partial resistance 19b is connected between the two comparators 17 and 18; And the third partial resistor 19c is connected to ground. In order to protect the ratio caps 17 and 18 from overvoltage, connect the connecting terminal 16a of the measuring resistor 16 to which the measuring voltage is applied.
5. via a series resistor 20 and a Zener diode 21 connected to ground; Limited to IV. In order to eliminate high-frequency interference voltages and smooth the measured voltage, the negative inputs of both comparators 17 and 18 are also connected to a respective RC
It has an anti-jamming device 22. The first comparator 17 is used as a short-term switching device. The reference voltage of the first comparator is adjusted to 1.5V on the positive input side. The second comparator 18 is used as an overload switching device. The reference voltage on the positive input side of the second comparator is 1. ○V is correspondingly smaller. The output sides of the comparators 17 and 18 are respectively the microphone o, :7 and the signal input side of the computer 15 1'5 e.
and 15d. Another signal input side 15
A rotational speed signal for measuring the rotational speed of the internal combustion engine is supplied to the microcomputer 15 via e. In order to supply the negative input of comparator 18 with a measuring voltage corresponding to the average current value, comparator 18 is connected upstream with a series resistor 24 and a capacitor 25 connected to ground.

- Next, the operation of the circuit device shown in FIG. 1 will be explained in detail using the signals shown in FIG. The control signal Is generated at the output 15a of the microcomputer 15 on the first time axis a
It is shown. The control signal Is has a predetermined frequency f=60Hz given by the microcomputer 15 and has a period T of the microcomputer 15. 256 to be processed continuously by the microcomputer 15
, in which case the time increment of ξ rus width is continuously calculated anew by the microcomputer in each case as a function of the measured rotational speed. Based on the frequency and width of the control ξ pulse Is, a position is created in the regulating magnet that is determined by the average value of the current and, depending on that position, the amount of fuel required for the no-load rotation of the internal combustion engine
, p, m, are adjusted to the no-load rotational speed. For example, the no-load rotation speed is 600 based on the load of the internal combustion engine.
When the voltage drops below r, p, m, this is detected by the microcomputer 15 and the ξ pulse width of the control @l-ξ pulse Is increases, thereby increasing the ξ pulse width of the control pulse Is. As a result, the current average value increases and the regulating magnet 10 opens the fuel supply channel a little more, so that the internal combustion engine increases the amount of fuel supplied as the engine speed increases. On the other hand, if the no-load rotational speed is very high, the .xi. pulse width of the control .xi. pulse Is decreases and the fuel supply is accordingly suppressed.

The second time axis shows a current l flowing through the adjusting magnet 10, the current i producing a correspondingly variable voltage drop across the measuring resistor 16. On the third time axis C, a monitoring signal (
A guard dog) is shown. 'In a first time portion A, the circuit arrangement of FIG. 1 is operated without disturbance. The corresponding voltage drop across the measuring resistor 16 is the result of the series resistor 20 and the RC noise removal stage 2.
2 to the negative inputs of both comparators 17 and 1δ. However, in comparator 18, the increase in measured voltage is attenuated by charging capacitor 25. In normal operation, the current average value Im is below the critical value for overloading the regulating magnet 10, so that both comparators 17 and 18 do not react. The microcomputer controls the first pulse of 40 μs after the start of the control pulse Ia during each control pulse Ia.
Since the output state of the comparator 17 is interrogated at time t1, as a result, under normal conditions, the microcomputer 1
The 0-fold signal is read and switched from the input side 15c of 5. Similarly, at a second time t2, 800 μs after the start of the control pulse ξ during each control pulse Is, the second comparator 1
8 is interrogated, and as a result, from the input side 15d of the microcomputer 15, 0-
The signal is read twice. Comparators 17 and 18 at time t1
and t2, the microcomputer 15 determines the control norm ξIs depending on the rotational speed of the internal combustion engine.
occurs. The calculated value of the pulse width can then be controlled by the microcomputer 15, if appropriate, by other parameters such as air temperature or engine temperature.

Still time portion B shows the case in which a short circuit occurs in the current circuit of the adjusting magnet 10. The current l has a very large value and a correspondingly large voltage drop occurs across the measuring resistor 16. This voltage drop is applied via series resistor 20 and noise removal stage 22 to the negative inputs of comparators 17 and 18. In this case, comparator 17 first reacts. At time t1, a 1- signal is read in at input 15c of microcomputer 15. The program of the microcomputer 15 is executed at time t.
When the 1-signal is read on the input side 15c, the microcomputer 15 output 14111 '5 a control ξ
The configuration is such that the pulse Is is immediately shut off.

As a result, the switching device 12 and thus the adjusting magnet 1o are also switched off via the amplifier 14. However, the microcomputer 1 generated on the output side 15b in synchronization with the control pulse Is
Since the monitoring signal wd of 5 occurs over the original full pulse width in the case of the response of the comparator 17, a fault in the program sequence of the microcomputer 15 can be detected by the monitoring signal wd. The above-mentioned process is repeated with the start of each successive control pulse ξ Is. The switching device 12 is programmed accordingly.
is finally shut off after a predetermined number of control pulses in the event of a short circuit, and can be instructed via the signal output side of another microcomputer 15 (not shown). The short connection period in the event of a short circuit and the capacitor 2 being re-made at the start of each control pulse.
5, the second comparator 18 is no longer switched on.

Assume that in time portion C the current average value Im exceeds the maximum allowable limit. A voltage drop across the corresponding measuring resistor 16 does not cause the comparator 17 to react, since the reference voltage of the comparator is relatively high. In contrast, the comparator 18, which has a relatively small reference voltage on the positive input side,
In response to time t2 of control pulse Is, a 1- signal is therefore read at input 011115d of microcomputer 15. Based on this signal, the correspondingly configured microcomputer 15 program then executes the next program. Shrink. As a result, the current average value Im also decreases somewhat. Also, the current average value Im is changed to the comparator 18 by the control/ξ pulse Is at time t2.
- If it is still large enough to generate a signal, during the next program execution the control noise ξ is also reduced by the time increment Δt. In this way, the average current value of the adjustment magnet 10 is gradually reduced until it reaches the permissible value again.

Since a large number of control pulses Is are sent out via the output 15a of the microcomputer 15 during the execution of the program, the pulse width of the control pulse Is is determined by the comparator 18.
In each case, only at the start of a new program execution is the time increment Δt reduced. However, in FIG. 2, for the sake of simplicity, only one constraint 11 pulse Is is shown in each time portion B and C for the execution of one zologram. It may also be advantageous if the microcomputer 15 can reduce the width of the .xi. pulse only if a large number of successive control .xi. pulses Is' division comparators 18 are activated. The average current value is reduced only if, for example, the microcomputer 15 detects that a permissible value of 2.3 A is exceeded during ten measurement cycles. In this way, an undesirably rapid decrease in the current average value Im in the adjusting magnet 10 is prevented. Interruption due to short circuit is detected by comparator 17.
It is adjusted to the current value of OA.

ADVANTAGEOUS EFFECTS OF THE INVENTION The circuit arrangement according to the invention makes it possible to carry out short-circuit monitoring and current control with a very large average current value, regardless of the switching state of the load to be controlled via the switching device in each case. Therefore, it is advantageous. Further, according to the present invention, load control j
This is advantageous because both overcurrent monitoring and short circuit monitoring can be performed by the same microcomputer at low cost.

[Brief explanation of the drawing]

FIG. 1 is a schematic circuit diagram showing a circuit device for connecting, disconnecting, and controlling (Ml) and monitoring the adjusting magnet by a microcomputer according to the present invention, and FIG. 2 is a signal line diagram explaining the operation of the circuit device in FIG. Yes. 1o: Adjustment magnet, 12: Transistor switching device,
15...Microcomputer, 16...Measuring resistor, 17.18...Comparator, 22...RC jamming countermeasure deviceContinued from page 10 Inventor Tart Neufer Earl 0 Inventor Hartmud Zweb Doyle 25 Federal Republic of Stuttgart Oberer Bau/Waltweg 39

Claims (1)

[Claims] 1. A circuit device for operational connection, disconnection and monitoring of an electrical load, which has a switching device controlled by a microcomputer using control pulses of constant period and variable ξ pulse width, a) Measuring resistance (1
6) and two threshold switches (17, 18,) to which the extracted measurement voltage is supplied; one of the threshold switches is used as an overload switching device (18) to control the maximum allowable current average value ( Im) and the other threshold switch is adjusted to the permissible operating connection current value as a short-circuit switching device (17), and b) the microcomputer (15) is adjusted at a first instant (t, ), interrogate the output state of the short-circuit switching device (17) during the period of each control pulse (Is), and immediately cut off the control pulse ('Is) if the switching device (17) responds. and C) the microcomputer (15) performs control and control at the second time point (t2).
Overload switching device (18) in the period of ξrus (Is)
and a switching device (18) for interrogating the output state of the
For connection, disconnection, and monitoring of electrical loads, characterized in that the width of the subsequent control ξrus (Is) is reduced by a fixed value (Δt) when the circuit device. 2. The microcomputer (15) reduces the ξ pulse width of the control ξ pulse (Is) only at the start of program execution when the overload switching device (18) responds. The circuit device according to scope 1. 3. In order to monitor the program sequence in case the short-circuit switching device (17) reacts, the control flil
2. The circuit device according to claim 1, wherein the supervisory signal ('wd) generated in synchronization with s) is generated over the entire original ξ pulse width.