JP5835168B2 - Indicator drive circuit - Google Patents

Description

  The present invention relates to an indicator driving circuit that appropriately controls lighting and extinction of an on-vehicle indicator.

  An example of an indicator driving circuit that appropriately drives an on-vehicle indicator is described in Patent Document 1. The indicator is composed of a light emitting component such as an LED (Light Emitting Diode), for example, and the indicator driving circuit is composed of an ECU (Electronic Control Unit) including a preventive safety system for in-vehicle use.

  The ECU gives an alarm when the indicator is turned on, and applies a desired voltage or current to the indicator circuit including the indicator when the indicator is in operation, that is, when the indicator is turned on. Here, a system in which the output of the indicator driving circuit is grounded when not operating, that is, when not lit is generally employed.

JP 2009-204712 A

  However, in such an indicator drive circuit, if noise from the power line of the vehicle motor drive system is superimposed on the wire harness connecting the ECU and the indicator circuit, the level of the noise waveform increases in the indicator circuit and the ground circuit. As a result, the cycle lengthened and the level itself increased, which could lead to inappropriate lighting of the indicator.

  In view of the above problems, an object of the present invention is to provide an indicator driving circuit that can prevent inappropriate lighting of an indicator.

In order to solve the above problem, an indicator driving circuit according to the present invention is an indicator driving circuit that selects an operation or non-operation of an indicator, and between the input and output of the indicator driving circuit is in the non-operation state. A cutting means for cutting the output and an inverter for inverting the output with respect to the input, wherein the cutting means is interposed between the inverter and an output terminal of the indicator driving circuit.

  According to the present invention, the input and the output in the indicator driving circuit are disconnected by the disconnecting means when not operating, so that inappropriate lighting due to the noise of the indicator can be prevented.

It is a circuit diagram which shows the premise structure of the indicator drive circuit 1 of the Example by this invention. It is a schematic diagram which shows the propagation mode of the noise in the premise structure of the indicator drive circuit 1 of an Example. It is a schematic diagram which shows the aspect in which the noise in the premise structure of the indicator drive circuit 1 of an Example is increased. It is a schematic diagram which shows the concept of the indicator drive circuit 1 of an Example. It is a schematic diagram which shows the specific circuit structure of the indicator drive circuit 1 of an Example.

  Hereinafter, embodiments for carrying out the present invention will be described with reference to the accompanying drawings. The indicator drive circuit 1 of the present embodiment is, for example, an ECU, and includes a known inverter as a precondition. The inverter includes an input terminal IN, an output terminal OUT, a power supply terminal Vdd, and includes a ground circuit G. The output terminal OUT is connected to the indicator circuit 3 via the wire harness 2.

  The indicator circuit 3 includes an indicator 4 constituted by, for example, an LED, includes a current limiting resistor R in series with the indicator 4, includes a voltage adjusting capacitor C in parallel with the indicator 4, and a wire harness at a branch point P A rectifying diode D is included on the second side. The indicator 4 also includes a ground circuit G.

  The ECU constituting the indicator drive circuit 1 is, for example, a preventive safety system ECU for a vehicle, and applies a desired voltage or current to the indicator 4 based on the operation of the inverter when the indicator 4 is turned on, that is, for example. Alert other people outside. Further, the ECU grounds the output terminal OUT of the inverter by the ground circuit G when the indicator 4 is turned off, that is, not operating.

  Here, there is a case where the wire harness 2 between the indicator drive circuit 1 and the indicator circuit 3 runs in parallel with, for example, a harness of a power supply line of a motor system mechanism such as a power seat of a vehicle or a mirror actuator. In this case, as shown in FIG. 2, the induction noise of the motor system is coupled by the capacitive coupling between adjacent harnesses, and the induction noise gets on the wire harness 2, and is applied to the harness line in the indicator circuit 3 of the indicator 4. Invite noise to propagate. If this noise level exceeds the operation threshold voltage of the indicator 4, the indicator 4 will be lighted incorrectly when the ECU is not operating.

  In addition, when induction noise is applied to the wire harness 2, the following mechanism causes an increase in noise level and an increase in period. That is, as shown in FIG. 3, when inductive noise propagates to the wire harness 2 as indicated by a circle 1, it is half-wave rectified as indicated by a circle 2 by an indicator 4 that is a diode D or LED, and a negative voltage component. Is removed. Further, as indicated by circle 3, the waveform is smoothed by the parasitic capacitance between the ground line indicated by the broken line connecting the ground circuit G in the indicator circuit 3 and the ground circuit G in the indicator drive circuit 1 and the power supply line of the motor system mechanism. As a result, the level of the waveform increases and the period becomes longer.

  When this noise gets on the wire harness 2 again via the ground circuit G, the inverter, and the output terminal OUT and reaches the indicator circuit 3, the indicator 4 is erroneously turned on. In particular, the longer the period of noise, the more inconvenience that erroneous lighting of the indicator 4 is easily recognized by human eyes.

  In view of this, the indicator drive circuit 1 of this embodiment is the indicator drive circuit 1 that selects the operation or non-operation of the indicator 4 and between the input terminal IN (input) and the output terminal OUT (output) of the indicator drive circuit 1. 4 is included as shown in FIG.

  A specific configuration of the cutting means 11 is a MOSFET 11 (Metal-Oxide-Semiconductor Field-Effect Transistor) shown in FIG. Here, the inverter inverts the output with respect to the input, the MOSFET 11 is interposed between the inverter and the output terminal OUT of the indicator driving circuit 1, and the MOSFET 11 is operated by a DSP 12 (Digital Signal Processor) inside the ECU. Turned on and turned off when not operating.

  That is, when the indicator 4 is not operating, that is, when not lit, the output terminal OUT of the indicator driving circuit 1 is disconnected from the ground circuit G when the MOSFET 11 is turned off as shown in FIG. Therefore, the waveform is smoothed by the parasitic capacitance with the power supply line of the motor system mechanism from the ground line indicated by a broken line connecting the ground circuit G in the indicator circuit 3 and the ground circuit G in the indicator drive circuit 1. It is possible to prevent the noise whose level is increased and the period is lengthened from being propagated to the wire harness 2. Thereby, the erroneous lighting by the noise of the indicator 4 can be prevented.

  Although the preferred embodiments of the present invention have been described in detail above, the present invention is not limited to the above-described embodiments, and various modifications and substitutions are made to the above-described embodiments without departing from the scope of the present invention. be able to.

  For example, a relay having a mechanical contact in place of the MOSFET 11 can be inserted between the inverter and the output terminal OUT as a cutting means. In this case, the DSP 12 turns off the coil terminal of the relay when not in operation and turns it on during operation.

  The present invention relates to an indicator driving circuit that selectively controls lighting of an indicator. In particular, the indicator is erroneously turned on when the indicator is turned off based on noise from the power supply system of the motor drive system and noise amplification in the vehicle. Can be more appropriately prevented. Thereby, the reliability of the alarm of the indicator controlled by the preventive safety system ECU can be enhanced.

1 Indicator drive circuit (ECU)
11 MOSFET (cutting means)
12 DSP
2 Wire harness 3 Indicator circuit 4 Indicator D Diode C Capacitor R Resistance P Branch point Vdd Power supply terminal IN Input terminal OUT Output terminal G Ground circuit

Claims (1)

An indicator driving circuit for selecting operation or non-operation of an indicator,
Cutting means for cutting between the input and output of the indicator driving circuit in the case of the non-operation ;
An inverter for inverting the output with respect to the input,
The indicator driving circuit according to claim 1, wherein the cutting means is interposed between the inverter and an output terminal of the indicator driving circuit.

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