WO1988007130A1 - Digitalized hybridizable current-regulating circuit for positive and negative current control circuits - Google Patents

Abstract

A circuit arrangement for regulating positive and negative currents passing through an electromagnetic consumer has at least one measuring resistance connected in series with the consumer and a digital input stage having at least one digital/analog converter.

Description

 Digitized hybridizable current control circuit for positive and negative control currents

State of the art

The invention relates to a circuit arrangement for regulating positive and negative currents through an electromagnetic consumer with a series connection of at least one measuring resistor and the consumer. Such a circuit arrangement is known, for example, from DE-OS 33 25 044 and is used in connection with internal combustion engines for current regulation by means of a direct current controller, for example a solenoid valve for metering fuel. In the known circuit, either a series connection of two or a bridge connection of four current control elements, in each case in series with the measuring resistor and the consumer, is provided.

Furthermore, for example from DE-OS 33 23 694 a P u lsd a uer / voltage voltage converter with an integrating device is known in which an operational amplifier is connected to a capacitance. Before each conversion, the output value of the integrating device can be set to a selectable initial value by bridging the integrating device. Furthermore, the output value can be stored by means of a switching element. A current control circuit which operates according to the "sample-and-hold" principle with capacitances is relatively slow and entails a not inconsiderable expenditure on software and hardware, namely for the timing, memory requirement and the generation of the control signals or for the capacities which are highly accurate ( Sample) and large (hold). For the latter reason, such circuits can also be practically not represented in an integrated design. Since they work analogously, they are also not compatible with computers.

Advantages of the invention

The circuit arrangement according to the invention for controlling positive and negative currents through an electromagnetic consumer with a series connection of at least one measuring resistor and the consumer, in which a digital input stage is provided which has at least one digital / analog converter, has the particular advantage that due to the digita len mode of operation a very quick reaction of the circuit arrangement to changed operating conditions is achieved »The control is extremely simple because one command is sufficient. Large and precise capacities are no longer required, and therefore extensive integration or hybridization of the circuit can be carried out. With the circuit arrangement according to the invention, a high-precision two-quadrant current control with simultaneous suppression of interference signals by short settling times can be achieved.

In an advantageous embodiment of the invention, two 4-bit digital / analog converters are provided; good resolution can be achieved with the eight bits. The output signal of the converter is advantageously in one or each of an amplifier circuit converted into a proportional current signal. If the input stage is provided with a control circuit to which not only the (8-bit) input signals but also other digital control signals can be applied, the control by the software is particularly simple since all digital signals can be transferred in parallel.

In the case of a current control circuit downstream of the input stage with a current / voltage converter, the inputs of which are supplied with the proportional current signal or a signal derived from a high-precision voltage source, preferably a bandgap reference source, and the output signal of which a voltage signal derived from the proportional current signal is connected receive particularly accurate voltage signal. As a result of the use of a bandgap reference, the entire circuit arrangement can be implemented as a completely balanced output stage hybrid. This leads to increased operational safety and cost savings, since there is no need for testing and / or adjustment work in the control unit.

Particularly great advantages result if, according to a further advantageous embodiment of the invention, a switching circuit is connected to the control circuit, from which switching devices can be actuated in response to the digital control signals. These each switch on a range signal from the high-precision voltage source or an associated range current path with the associated measuring resistor of the consumer. By dividing the entire current range into preferably three ranges, a particularly high resolution in the range of one per thousand can be achieved with little effort. These current sources can be switched to the consumer by means of further switching devices which can be actuated by the switching circuit and are arranged between current sources and the consumer; the current control is then switched off and the current through the consumer is determined only by these current sources. This offers advantages with regard to special operating conditions, for example in the case of a fuel cut-off in internal combustion engines. Furthermore, exceptional operating states should also be manageable and for this purpose, according to a further advantageous embodiment of the invention, it is provided that the changeover switch can be acted upon by an emergency operation signal and, in response to this, switches off switching devices arranged in the respective areas.

In the circuit arrangement according to the invention, protective circuits can also be provided in a simple manner, for example against short-circuiting of the consumer or excessive supply voltages. All of the embodiments described above can be integrated or hybridized.

drawing

The invention is explained in more detail below with reference to an exemplary embodiment shown in the drawing, from which further advantages and features emerge. 1 shows an advantageous embodiment of a circuit according to the invention and FIG. 2 shows its construction as a hybrid with an integrated circuit and external components.

Description of the embodiment

Regeln des Stroms dureh einen elektromagnetischen Drucksteller, der in einer Bypass-Leitung einer mechanischen Einspritzanlage einer Brennkraftmaschine angeordnet ist. Über αie Beeinflussung des Steuerstroms für den Drucksteller laßt sich so eine elektronische Korrektur bei einer mechanischen Einspritzung erreichen. Es ist offenbar, daß hierfür eine hohe Genauigkeit sowohl in Hinblick auf die Auflosung als auch die Reproduzierbarkeit erforderlich ist.The embodiment is a scarf

Regulation of the current by an electromagnetic pressure actuator, which is arranged in a bypass line of a mechanical injection system of an internal combustion engine. An electronic correction in mechanical injection can thus be achieved by influencing the control current for the pressure actuator. It is evident that this requires a high level of accuracy in terms of both resolution and reproducibility.

1 shows a circuit arrangement which essentially has two parts, an input stage 10 and the actual current control circuit 40. The current I _S through a pressure regulator DS is to be controlled as a function of digital input information D0, D1, ..., D8, which are present with additional control information D8,, .., D11 at the input of the input stage.

For this purpose, the input stage 10 has a 12-bit latch 12 which is put into operation by means of an EN (enable) command. The digital input signals D0, ..., D7 are transferred in parallel to two downstream digital / analog converters 14, 24. Each of the converters 14, 24 is designed as a 4-bit converter and consequently the first four bits D0,..., D3 are applied to the digital / analog converter 14 and the second four bits D4 to the other digital / analog converter 24 , ..., D7 handed over. At the same time, the control information D8, ..., D11 is transferred via a line 22 to a changeover circuit 116, the function of which will be explained in more detail below.

An associated amplification circuit is connected downstream of each of the digital / analog converters 14 or 24, and zuar an amplifier circuit 16, 18, 20 for the converter 14 and an amplifier circuit 26, 28, 30 for the converter 24. The output signal of the converter 14 is fed to one input (+) of an operational amplifier 16, the other input (-) with a terminal of a resistor 20 (1 kiloohm) and the emitter of an npn transistor 18 is connected. The other terminal of resistor 20 is connected to ground. In a corresponding manner, the output of the digital / analog converter 24 is connected to one input (+) of an operational amplifier 26, the other input (-) of which is connected to a connection of a resistor 30 (16 kilohms), the other connection of which is connected to ground, and connected to the emitter of an NPN transistor 28. The collectors of the transistors 18, 28 are connected to one another. A current of up to 1.70 mA can be emitted by the transistors 18, 28 on the collector side. Furthermore, in the input stage 10 there is also a module, schematically referred to as a reference current source, in which a voltage source 32 leads to an input (-) of an operational amplifier 34, the other input (+) of which is connected to a voltage divider made up of resistors 36, 38 which is connected to a high-precision reference voltage source 52 is connected and is supplied by it with a reference voltage U _R of 3.750 V. The two reference sources 32 and 52 are designed as bandgap sources that do not require any adjustment per se, but the reference source 52 can be adjusted on the IC for drift optimization.

The reference voltage source 52 is also connected to a voltage divider composed of resistors 54, 56, 58, 60 and 62, of which the latter (62) can be trimmed. The taps of the voltage divider lead to four connection points of a switch 46. In detail, these connection points are designated (from top to bottom in FIG. 1) 3, 2, 1 and SAS and thus give three control ranges 3, 2 and 1 and a special area SAS (fuel cut-off), which are explained in more detail below.

The switch 46, that is to say its range selection, is controlled via the switching circuit 116, as indicated by an arrow correspondingly marked with (46), as a function of the digital control information D8,..., D11.

The collective tap of the switch 46 is connected to an input (+) of a current / voltage converter 42, the other input (-) of which is the amplified output signal (0 to 1.7 mA) of the analog / digital converter 14, 24. This amplified signal therefore generates a voltage drop of up to 1.7 V at a resistor 44 connected to the input (-), the other terminal of which is connected to the output of the current / voltage converter 42, since the resistor 44 has a resistance value of 1 kilohm . The corresponding range signal of the switch 46 is therefore connected to this 1.7 V. Resistors 54 to 62 are selected so that, starting from UR = 3.750 V, there is a voltage of 3.625 V at connection 3 of switch 46, 3.410 V at connection 2, 3.070 V at connection 1 and 3.188 V at connection SAS. The voltage U _S at the output of the current / voltage converter 42 is therefore (in the area 3) (1.7 + 3.625) V = 5.325 V. Accordingly, in areas 2 and 1 there are maximum voltages U _S of 5.11 and 4, respectively. 77 V.

The voltage U _S is present as a control voltage at an input (+) of an operational amplifier 50 connected as a comparator, the other input (-) of which is connected to the collective tap of a switch 48, the individual taps 48.1, 48.2 and 48.3 of which are each connected to a measuring resistor stand RM1, RM2 or RM3 are connected. While switch 46 therefore uses its taps 46.1, 46.2 and 46.3 to select the reference voltage for the respective area 1, 2 and 3, switch 48 assigns the measuring resistor RM1, RM2 and RM3 associated with the respective area. The switches 46, 48 are therefore correspondingly controlled synchronously via the switching circuit 116, which is further indicated by the arrow marked (48).

The output of the comparator 50 is connected to the base of a transistor 64 (area 1), 74 (area 2) and 84 (area 3). Since the circles for areas 1, 2 and 3 essentially correspond to one another, only area 1 is discussed in detail below.

The collector of transistor 64 is connected to ground, the emitter is connected to a current source 94 and to the base of a further transistor 66 and to a connection of a switch 68, the other connection of which is connected to ground. The switch 68 can be controlled by the switching circuit 116. The collector of transistor 66, like the other connection of current source 94, is connected to a supply voltage U _B. The emitter of the transistor 66 is connected to the terminal 48.1 of the switch 48 and the measuring resistor RM1 for the area 1, which is connected in series with the consumer, the pressure regulator DS and consequently through which the current I _S flows. Furthermore, the emitter of the transistor 66 is connected to a current source 70 which can be connected to ground via a switch 72 which can be actuated by the switching circuit 116.

Corresponding components are provided in the other two areas 2 and 3, namely transistors 74 and 84 corresponding to transistor 64 and transistor 66 corresponding to transistor 66 sistors 76 and 86. αer current source 94, current sources 96 and 95, switch 68, switches 78 and 88, measuring resistor RM1, measuring resistors RM2 and RM3, current source 70, current sources 80 and 90, and switch 72, switches 82 and 92 .

In the operating state shown in FIG. 1, area 1 is active and areas 2 and 3 are inactive. This results from the position of the switches 46 and 48, in which the taps 46.1 and 48.1 are switched through. Further, the switch 68 opens, transistor 66 would otherwise be blocked, and switch 72 is closed. By blocking the transistors 76, 86 as a result of the closed switches 78, 88, the regions 2 and 3 are switched off.

Where it is connected to the measuring resistors RM1, RM2 and RM3, the pressure actuator DS is also connected to an input of an operational amplifier 106, at the other input of which the highly precise voltage UR is applied. The output of the operational amplifier 106 is connected to the base of a transistor 108, the emitter of which is connected to ground and the collector of which is connected to the other connection of the pressure actuator DS. The operational amplifier 50, with one of the power output stages 66, 76 or 86 (depending on the position of the switch 48), represents a voltage follower and therefore the voltage U _{S is established} at the associated terminal X, Y or Z, provided the terminal current

I _x , I _y , I _z assumes values in the range of the terminal load capacity, namely I _x = -25 ... 10 mA, I _y -50 ... 10 mA and 145 ... 10 mA (or 45 mA (current sources

118 and 90)). This current-amplified signal U _x , U _y or

U _z is used via the associated range measuring resistor RM1, RM2 or RM3, the operational amplifier 106 and the power output stage 108 to regulate the consumer current Iς according to the relationship: I _S = (U _{x, y, z} - U _R ) / RM1,2, 3rd The common connection of the measuring resistors RM1, RM2, RM3 and the pressure actuator DS is also connected to an input (+) of a comparator 104, the other input (-) of which is at 1.7 V. The comparator 104 is used for short-circuit detection. If a short circuit occurs at the pressure actuator DS, that is to say terminal K is at ground potential, the comparator 104 switches off the current paths via the transistors 66, 76, 86 via its output, which is connected to the switches 68, 78, 88.

Furthermore, an overvoltage protection circuit 114 is shown schematically in FIG. 1, which outputs a corresponding output signal to the switching circuit 116 in the event of overvoltage conditions and causes the switching circuit 116 to switch off all analog functions (everything except 10, 16).

In addition to the "normal" operating state, in which, depending on the control information D8,..., D11 present, one of the areas 1, 2 or 3 is switched on and in the selected area the current I _{S is} regulated by the consumer DS with extremely high resolution , there are two further operating states in which special conditions prevail. One of the operating states is the overrun fuel cutoff (SAS). In this case, a certain current level is to be delivered to the pressure actuator DS, without being influenced by the input information DO, ..., D7. For this purpose, the switch circuit 116 actuates several switches on the basis of a specific bit combination D8,..., D11, specifically switch 46 with tap 46. SAS is switched through and switches 110 (current source 118) and 112 (current source 100) become switched simultaneously. If the current sources 100, 118 are connected to the circuit with DS, all three areas (RM1, RM2, RM3) are switched off at the same time, that is to say the regulation of I _S is overridden. The current I _S through DS is then only determined by the current sources 100, 102 and 118, 90. The second exceptional operating condition concerns an emergency operation. For this purpose, a corresponding signal NL is given to the switching circuit 116, which then deactivates both the areas 1, 2 and 3 and the overrun fuel cutoff. The current source 102 now remains as the only (non-switched) current source.

The following operating values were achieved with the circuit arrangement according to the invention shown in FIG. 1:

t schematisch. wie die in Figur 1 dargestellte Schaltungsanordnung 10, 40 in einer integrierten Schaltung zum überwiegenden Teil integriert ist. Insgesamt wird ein Hybrio erhalten, bei dem die integrierte Schaltung mit den drei Meßwiderständen RM1, RM2 und RM3 sowie zusätzlichen Kondensatoren für Schutz- und Entstörzwecke Deschaltet ist. Die Klemmenbezeichnungen "A", "B" und so weiter in Figur 2 entsprechen den Klemmenbezeichnungen von Ficiur 1. in the range 1: I _S from -10 mA to +15 mA with a resolution of 0.098 mA; in the range 2 I _S between -10 mA and +40 mA with a resolution of 0.196 mA; in the 3 I _{S range} from -10 mA to +126 mA with a resolution of 0.533 mA; with overrun cut-off: I _S less than or equal to -45 mA; and in emergency operation: I _S between -1 mA and +1 mA. The resolution corresponds to the LSB (least significant bit) of the 8-bit input signal. The maximum control current in area 3 could be increased up to 140 mA. With the digital / analog converter, an LSB corresponds to a current of 0.098 mA. The extraordinarily high resolution that can be achieved with the circuit arrangement according to the invention can be seen from a comparison of the 0.098 with the 140 mA, namely this corresponds to a resolution in the range of 0.7 ° / oo, ie less than one per thousand. The advantage that can be achieved with the invention is, in particular, that the high resolution of 0.098 mA is only achieved in the range (Is = -10 ... 15 mA) in which it is actually required. In this way, the otherwise required effort of an analog / digital conversion, which above all would not be technically feasible as a fully integrated solution, can be avoided and the full integration can be realized in this way. In this way, an extremely finely graduated control of the pressure actuator DS and thus a very precise correction of a mechanical injection system for internal combustion engines can be provided electronically. Figure 2

t schematic. how the circuit arrangement 10, 40 shown in FIG. 1 is largely integrated in an integrated circuit. Overall, a hybrio is obtained in which the integrated circuit with the three measuring resistors RM1, RM2 and RM3 and additional capacitors for protection and interference suppression purposes is switched off. The terminal designations "A", "B" and so on in FIG. 2 correspond to the terminal designations of Ficiur 1.

Claims

Claims 1. Circuit arrangement for controlling positive and negative currents through an electromagnetic consumer with a series circuit of at least one measuring resistor and the consumer, characterized in that a digital input stage (10) for receiving digital input signals (D0, ..., D7) is provided, which has at least one digital / analog converter (14, 24). 2. Circuit arrangement according to claim 1, characterized in that two 4-bit digital / analog converters (14, 24) are provided. 3. Circuit arrangement according to claim 1 or 2, characterized in that the digital / analog converter (14, 24) is followed by an amplification circuit (16, 18, 26, 28) from which a current signal proportional to the output voltage of the digital / analog converter can be emitted is. 4. Circuit arrangement according to claim 1, 2 or 3, characterized in that the input stage (10) with a control circuit (12) for receiving the digital input signals (D0, ..., D7) for the digital / analog converter (14, 24) and for receiving digital control signals (D8, ..., D11). 5. Circuit arrangement according to claim 3 or 4, characterized in that the input stage (10) is followed by a current control circuit (40) having a current / voltage converter (42), at one input (-) the proportional current signal and at the other Input (+) a signal derived from a high-precision voltage source (52), preferably a bandgap source (52), and from which a voltage signal can be emitted at its output, which is used to generate a control voltage (U _S ) via a resistor ( 44) voltage signal derived from the proportional current signal is applied. 6. Circuit arrangement according to claim 5, characterized in that the control voltage (Uς) is connected to an input (+) of a control circuit (50) which optionally has a range power output stage (66; 76; 86) for providing a voltage follower (50, 66; 76v; 86), whose output voltage (U _x , U _y , U _z ) is applied via a range measuring resistor (RM1, RM2, RM3) to an input of a control circuit (106), at the second input of which a signal (U _R ) of the high-precision voltage source (52) for regulating the consumer current (I _S ) according to the relationship I _S = (U _{x, y, z} - U _R ) / RM1,2,3. 7. Circuit arrangement according to one of claims 4 to 6, characterized in that a switching circuit (116) is connected to the control circuit (12), of which in response to the digital control signals (D8, ..., D11) switching devices (46, 48, 72, 82, 92) can be actuated, by means of which an area signal from the high-precision voltage source (52) or an associated area current path, in which a measuring resistor (RM1, RM2, RM3) is located, of the consumer (DS) can be switched on . 8. Circuit arrangement according to claim 7. dadurcn gekennzeionnet that three area signals and three area measuring resistors (RM1, RM2, RM3) are provided. 9. Circuit arrangement according to claim 7 or 8, characterized in that the switching circuit (116) actuatable switching devices (110, 112) are provided, which are arranged between the current sources (100, 118) and the consumer (DS). 10. Circuit arrangement according to one of claims 7 to 9, characterized in that the switching circuit (116) can be acted upon by an emergency operation signal (NL) and in response to this in the respective areas (1, 2 and 3) arranged switching devices (68, 78, 88, 72, 82, 110, 92) switches off, so that the consumer (DS) is de-energized (I _S = 0 ± 1 mA). 11. Circuit arrangement according to one of claims 1 to 10, characterized in that a monitoring circuit (104) connected to the consumer (DS) is provided, from which a switch-off signal can be emitted in the event of a short circuit at the consumer (DS). 12. Circuit arrangement according to one of claims 1 to 11, characterized in that an overvoltage protection circuit (114) is provided, from which a switch-off signal can be emitted when a supply voltage (U _B ) is exceeded, preferably to the switching circuit (116 ).