FR2623948A1 - CIRCUIT DEVICE FOR MONITORING MULTIPLE POWER OUTPUTS CONNECTED IN PARALLEL, IN PARTICULAR FOR DETECTING SHORT CIRCUITS IN DRIVING EQUIPMENT IN A VEHICLE AIR CONDITIONING INSTALLATION - Google Patents

Abstract

a) Circuit device for monitoring several power outputs connected in parallel, in particular for detecting short circuits in drive equipment in an air conditioning system of a vehicle. b) Circuit device characterized in that there is provided a rocker 28, an electronic switch 31 being connected in series with the measuring resistor 30, the switch whose control input is connected to the output of the rocker 28, this electronic switch 31 being constructed so that it is closed when flip-flop 28 is positioned and open when flip-flop 28 is reset, while the output potential of flip-flop 28 is exploited for the detection of shorts. circuits. c) The invention relates to a circuit device for monitoring several power outputs connected in parallel, in particular for detecting in an air conditioning installation of a vehicle.

Description

Circuit device for monitoring multiple outputs

  power units connected in parallel, in particular for detecting short circuits in drive equipment in an air-conditioning system

of a vehicle. "

  The invention starts from a circuit device

  to monitor multiple power outputs

  in parallel, this device comprising a

  measuring resistor, through which all power outputs pass, and having a comparison device, which compares the measurement voltage falling on the measuring resistor with a reference voltage, which is set to a larger value than that of the measuring voltage, which falls on the measuring resistor, due to the current

  total crossing this resistance when switching on

  simultaneously with a maximum number of power outputs, and this comparison device generates a control pulse as soon as the measurement voltage

exceeds the reference voltage.

  With such circuits, so-called monitoring circuits, it is possible, for example, to detect short circuits in the power outputs and, possibly, all

  the power outputs can be switched off

  cooked. Such monitoring circuits are preferred as short circuit protection end stages. In a known circuit device of the type

  initially mentioned for a step-by-step motor

  driphasé, playing the role of training equipment in an air conditioning system of a vehicle,

  the four phases of this stepping motor are controlled

  by means of a shift register and a Darlington circuit by a microcomputer. The total current of the phases flows through the measuring resistor. In case of short circuit,

  the voltage falling on the measuring resistor

  the reference voltage, and the measuring device

  reason constituted by a comparator, connects to the

  mass. The mass potential at the exit of the comparator

  in the microcomputer triggers an order

  interruption, which switches off the final stages.

  Darlington, through its

  trigger input of the output. In the program

  In the case of interruption, this state is maintained by a diode until all the end stages are switched off, after appropriate control by the microcomputer. In a control mode, to detect an interruption in at least one phase of the motor not to

  not, all phases are ordered individually-

  is lying. With a second comparator, the voltage falling on the measuring resistor is then compared with

  a second reference voltage. This second comparison

  switch to ground when measuring voltage

  exceeds the second reference voltage. If the

  the controller does not switch to ground, the potential

  both at the output of the comparator is interpreted by the microcomputer as an interruption. The second reference voltage is set at a lower value

  to that of the measuring voltage, which falls on the

  measure, because of the current flowing through this

  resistance in the case of an intact phase.

  The circuit device according to the invention

  The invention is characterized in that a flip-flop is provided which is positioned by an interlocking pulse.

  at the beginning of each switching signal for the

  power, and which is reset

  by the control pulse, an electronic switch

  that being connected in series with the measuring resistance

  a switch whose control input is connected to

  the output of the flip-flop, this electronic switch

  that being made so that it is closed when

  the scale is positioned and opened when

  it is reset, while the potential

  the output of the weighbridge, is used for the de-

short circuit protection.

  This circuit device has the advantage of a direct disconnection of all the outputs

  power, through the electrical switch

  tronic, during the intervention of a short circuit on at least one output power. For this power off circuit, this circuit device does not include a Darlington circuit with a trip input of the output, but, on the contrary, the amplification circuit for the switched power outputs can be realized from in any way. When a short circuit occurs, the flip-flop is reset. The potential to

  the output of the rocker blocks, on the one hand, the

  electronic device and serves, on the other hand, to detect

  short circuit for the microcomputer which

  starts the control and indication programs

appropriate.

  The circuit device is economical, so that its cost price is hardly noticeable in the case of an engine intended to be used on a

  motor vehicle. But this device avoids

  expensive parations on the engine, or the premature exchange of the latter. Other features of the invention

  advantageous supplements and improvements

  of the circuit device defined above.

  According to one characteristic of the invention, the output potential of the flip-flop is compared with the potential of the switching signals and it is concluded that

  a short circuit when in the presence of communication signals

  mutation, the exit potential of the flip-flop corresponds to

  set to reset the flip-flop.

  According to another characteristic of the invention

  tion, the scale and the comparison device are

  constituted by a comparator, at the inverted input of

  which is applied the measurement voltage, while at the non inverted input of this comparator, is applied

  the reference voltage, the triggering pulses

  being applied to the non-inverted input of the

  parator and the comparator is now by reaction

  in its ON state corresponding to the position state

the rocker.

  According to another characteristic of the invention

  the non-inverted input of the comparator is connected

  on the one hand, to an electrode of a capacitor whose other electrode is connected to a signal conductor carrying the latching pulses, and, on the other hand, to a first voltage tap of a first voltage divider, comparator output

  being connected to a second voltage tap of potential

  higher voltage divider, the input

  of the comparator being connected to the

  voltage of a second voltage divider, in the

  whose lower end is the measuring resistance

connected to zero potential.

  According to another characteristic of the invention

  the electronic switch takes the form of a field effect transistor, preferably a field effect transistors, semiconductor oxide metal (MOS cell) whose gate is connected to the output

of the comparator.

  Finally, according to another characteristic of

  the invention, the switching signals and the pulses

  in synchronism with these sys-

  are generated by a microcomputer and for

  the detection of short circuits the outputs of the compa-

  are connected with a microphone input

computer.

  By completing the circuit device with a comparator, and providing a control mode,

  the monitoring circuit can also be used

  used to record interruptions on each

individual power.

  The invention will be explained in more detail

  hereinafter with the aid of an exemplary embodiment

  shown in the accompanying drawings, in which: - Figure 1 is a circuit diagram of a

  control circuit for a four-step stepper motor

  phased with an integrated monitoring circuit; - FIG. 2 is a diagram of the control signals at the outputs 1 to 5 of a microcomputer

  in the control circuit of Figure 1.

  - Figure 3 shows an example of how

  the four connected power outputs of the cir-

cooked control of Figure 1.

  The control circuit, represented diagrammatically

  FIG. 1, for a stepper motor with

  four-phase continuous current, includes a micro-

  computer 19 with the control outputs 1 to 5 and a power switch 20 with four outputs of

  connected in parallel 11 to 14. The switching

  In the simplest case, as shown in FIG. 3, the power unit 20 may be composed of four transistors 21 to 24 in parallel, the bases of which are connected to the control inputs at 18, the collectors to the outlets 11. 14, and the transmitters at a common input 25 of the power switch 20. In a preferred embodiment of the invention, the power switch 20 is

  however realized in the form of a Darling-

  your. The stepper motor 26, which takes the form of a brushless DC motor, is connected, on the one hand, by its four phases, to the power outputs 11 to 14, and on the other hand to the voltage VB battery from a vehicle battery. In addition, a zener diode 27 is connected in parallel to the

  power switch 20, in order to limit the over-

  tensions. At the control outputs 1 to 5 of the micro-

  computer 19, the control signals are applied

  shown in Figure 2. With the signals of

  command inputs 1 to 4, the four phases

  Steps of the stepping motor 26 are connected in a cyclic succession, while the control signal at the control output 5 has start-up or start-up pulses for a monitoring circuit.

  This monitoring circuit has a base

  and a comparison device which are

  by a comparator 28. From this monitoring circuit

  launches, is also part of a measuring resistor which in series with a field effect transistor, hereinafter referred to as FET 31 is connected, on the one hand, to the input 25 of the power switch 20, and other on the other hand, at zero potential. The junction point between the FET 31 and the measurement resistor 30 is connected by

  via a resistor 32, at the inverting input

  comparator 28, which at the same time connects

  by means of a resistor 33, to a

  stabilized supply voltage Vcc for the micro-

  calculator 19. So, we have at the inverted input of the

  comparator 28, a voltage which is identical or

  proportional to the measuring voltage UM falling on the measuring resistor 30. At the non-inverted input of the comparator 28, a reference voltage is applied

  Urefi which is taken from a voltage divider

  sion constituted by the resistors 34, 35, 36 and 37 and which is connected to the battery voltage VB. The junction point between the resistors 35 and 36 is then connected to the non-inverted input of the comparator 28, while the point of junction between the resistors

  34 and 35 is connected to the output of the comparator 28.

  The latter is also connected to the FET grid 31

  and, through a resistor 38, to a

  6 of the microcomputer 19. With the monitoring circuit just described, a short circuit monitoring of the power outputs is obtained.

11 to 14 of the control circuit.

  In order to complete this monitoring function with interrupt detection, it is

  provided a second comparator 39 whose input not

  poured is connected to the measuring resistor 30 by

  through resistance 32. At the inverse input

  comparator 39, a second voltage is applied.

  reference contract UrefZ, which is also deducted from

  from the voltage divider constituted by the

  34 to 37, and this at the junction point between the resistors 36 and 37. The output of the comparator 39 is connected, via a resistor 40, to

  the supply voltage Vcc and at an input 7 of the

  19. To carry out the detection of

  disruption, it is planned a special control mode

  of the microcomputer 19, in which a command

  sequential dividend of power outputs 11 to

14 is performed.

  The operating mode of the circuit of

  monitoring which has just been described, is as follows: At each switching on of one of the power outputs 11 to 14, via the outputs

  1 to 4 of the microcomputer 19, an impulse

  start-up is generated by the latter at its

  5. The positive edge of the start pulse sets the integrated latch to the comparator 28, in its position state, in which the output

  of the comparator 28 takes the logic H. The FET 31 de-

  conductor and the rocker or the comparator 28 is maintained in its position state or

  well in its ON state via the retro-

action.

  The reference voltage Urefi is fixed at

  a value greater than that of the voltage of

  which falls on the measuring resistor 30 due to the total current flowing through this resistor when simultaneously connecting a maximum number of power outputs. Expressed as equality, this translates as: Urefl> n. est. RM n being the number of power outputs switched on simultaneously (in this case, always two), is

  being the phase current and RM the value of the resistance

Measuring time 30.

  In the normal operating state, the

  applied to the non-inverted input of the comparator

  28 will always be lower than the reference voltage.

26-23948

  Urefl. If, however, a short circuit occurs

  in one of the power outputs 11 to 14, the current flowing through the measurement resistor 30 increases beyond the permissible limit value. The voltage at the non-inverted input of the comparator 28 thus becomes greater than the reference voltage Urefl at the inverted input. As a result, the scale changes from its ON state

  in its initial state or OFF state and the output of the

  Rator 28 takes logic L. As a result, the FET 31

  is blocked and the stepping motor 26 is turned off.

  cooked. Simultaneously, in the microcomputer 19, by comparing the control potentials with the control outputs 1 to 4 (logic H) and the output potential

  comparator 28 or at input 6 of the micro-

  calculator 19 (logical L), it is concluded that

  circuit. For interrupt detection, a special control mode is delivered by the microcomputer 19, in which mode always a single output of

  power 11 to 14 is engaged; The reference voltage

  Uref2 at the uninverted input of the second comparator

  39 is set at a value smaller than the

  measuring voltage which falls on the measuring resistor due to the current flowing through this resistance in

  the case where the power output 11 to 14 is intact.

  Expressed as equality, this translates as: Uref2 <iS.RM is the phase current of the stepper motor 26

  during the control mode, and RM the value of the

measuring resistance 30.

  When the charging circuit is not in-

  interrupted, the falling tension on the resistance of me-

  30 and applied to the non-inverted input of the

  39, is greater than the reference voltage Ur.f2. As a result, the output of the comparator 39 is at the logic H. If the charging circuit at the output of one of the power outputs 11 to 14 is interrupted, then the voltage on the measurement resistor 30 is zero and the output comparator 39 takes the logic L. In the microcomputer 19, by comparing the control potentials on the control outputs 1 to 4 (logic H) and the potential on the input 7 (logic

L), we conclude at the interruption.

R E V E N D I CATIONS

  1.- Circuit device for monitoring a plurality of power outputs connected in parallel, this device comprising a measurement resistor, through which all the outputs

  of power, and comprising a device for comparing

  sound, which compares the measuring voltage falling on the measuring resistor with a reference voltage, which is set to a value greater than that of the measurement voltage, which falls on the measuring resistor, due to the total current flowing through. this

  resistance when a name is simultaneously

  maximum power output, and this comparison device generates a control pulse as soon as

  measuring voltage exceeds the reference voltage

  A circuit device characterized in that there is provided a flip-flop (28) which is set by a latching pulse at the beginning of each switching signal for the power outputs (11 to 14) and which is reset initial state by the impulse of

  control, an electronic switch (31) being connected

  in series with the measuring resistor (30),

  an actuator whose control input is connected to the output of the flip-flop (28), the electronic switch (31) being constituted so that it is closed when the flip-flop (28) is positioned and open when the flip-flop (28) is reset, while the output potential of the flip-flop (28) is exploited

  for the detection of short circuits.

  2. Circuit device according to the

  cation 1, characterized in that the output potential of the flip-flop (28) is compared with the potential of the

  switching signals and that one concludes with a short-

  when, in the presence of switching signals, the output potential of the flip-flop (28) corresponds to

  that of the rocker (28) reset.

  3.- Circuit device according to any one

  shell of claims 1 or 2, characterized in that

  the flip-flop and the comparator are constituted by a comparator (28), at the inverted input of which the measurement voltage (UM) is applied, whereas at the non-inverted input of this comparator,

  is applied the reference voltage (Urefl), the im-

  latching pulses being applied to the non-inverted input of the comparator (28) and the comparator

  (28) maintaining by reaction in its ON state cor-

  corresponding to the positioning state of the rocker (28).

  4. Circuit device according to the

  3, characterized in that the non-inverted input of the comparator (28) is connected, on the one hand, to a

  electrode of a capacitor (29) whose other electro-

  of is connected to a signal conductor carrying the latching pulses, and, secondly, to a first voltage tap (35, 36) of a first voltage divider (34 to 37), the output of the co5 macerator (28) being connected to a second higher potential voltage tap (34, 35) of the voltage divider (34 to 37), the inverted input of the comparator (28) being connected to the voltage tap of a second

  voltage divider (30, 32, 33) in the lower branch

  which is the measuring resistor (30)

connected to zero potential.

  5. Circuit device according to the

  cation 4, characterized in that the electrical switch

  tronic takes the form of a field effect transistor (31), preferably a field effect transistor, a semiconductor oxide metal (MOS cell) whose gate is connected to the output of the comparator

(28).

  6.- Circuit device according to any one

  conque of claims 1 to 5, characterized in that

  switching signals and triggering pulses

  in synchronism with these signals, are generated

  by a microcomputer (19) and for detecting shortcircuits, the outputs of the comparator

  (28) are connected with an input (6) of the micro-

calculator (19).