JP2009223857A - Vehicular display device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a vehicular display device that controls an illuminating light source at a stable switching frequency even in a light load condition. <P>SOLUTION: The vehicular display device includes an illumination means 6, an adjustment means 3 for adjusting the brightness of the illumination means 6, a dimmer circuit 5 for driving the illumination means 6, a control means 4 for controlling the dimmer circuit 5 by a PWM control signal matching dimmer data set by the adjustment means 3, an intermittent or PFM switching power circuit 1 for receiving a primary voltage to generate a secondary voltage for driving the illumination means 6 via the dimmer circuit 5, and a current load circuit 2 for forcibly increasing a current load on the switching power circuit 1 in response to a switching signal from the control means 4 when the control means 4 determines whether an adjustment level set by the adjustment means 3 is a light load mode and affirms a light load mode. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a vehicle display device provided with illumination means, and is particularly suitable for a vehicle display device that performs luminance adjustment by PWM control.

Conventional vehicle display devices, for example, in addition to speedometer illumination, indicator illumination for indicating when the headlamp is in a high beam state, and the remaining amount of fuel are below a predetermined threshold value. For example, Japanese Patent Application Laid-Open No. H10-228707 discloses a control of an illumination light source for alarming while adjusting the luminance by PWM (pulse width modulation) driving.
Japanese Patent Laid-Open No. 2004-325324

  However, some of these power sources use intermittent or PFM (pulse frequency modulation) type switching power supply circuits. However, when the power supply to the illumination light source as a load is light (for example, in the case of low luminance illumination) (Case) has a characteristic that the switching frequency of the power supply circuit changes. Therefore, since the frequency band in which switching noise is generated also changes, there is a problem that noise countermeasures are difficult.

  Accordingly, an object of the present invention is to provide a vehicle display device that can control the illumination light source at a stable switching frequency even in the case of a light load. It is to provide.

  The vehicle display device according to the present invention includes a lighting unit, an adjusting unit for adjusting the brightness of the lighting unit, a dimming circuit for driving the lighting unit, and the adjustment. A control means for controlling the dimming circuit by a PWM control signal corresponding to the dimming data set by the means, and a secondary voltage for inputting the primary voltage and driving the illuminating means via the dimming circuit. The control unit determines whether the intermittent or PFM type switching power supply circuit to be generated and the adjustment range set by the adjustment unit are in the light load mode, and based on the determination result, in the light load mode In some cases, a current load circuit for forcibly increasing the current load of the switching power supply circuit based on a switching signal from the control means is provided.

  According to a second aspect of the present invention, in the vehicle display device according to the first aspect, the current load circuit includes a resistor that sets an increase amount of the load of the switching power supply circuit, and a switching signal of the control means. And a transistor for switching whether or not to apply a current load to the resistor.

  The present invention provides an adjustment unit for adjusting the brightness of the illumination unit, a dimming circuit that drives the illumination unit, and a PWM control signal corresponding to dimming data set by the adjustment unit. With respect to a vehicle display device including a control means for controlling a circuit, the illumination light source can be controlled at a stable switching frequency even in the case of a light load.

  Embodiments to which the present invention is applied will be described below with reference to the accompanying drawings.

  FIG. 1 is a block diagram showing an electrical configuration relating to an illumination structure, which is an embodiment in which the present invention is applied to a vehicle meter. The vehicular instrument includes a switching power supply circuit 1, a current load circuit 2, an adjustment unit 3, a control unit 4, a dimming circuit 5, and an illumination unit 6.

  The switching power supply circuit 1 inputs a primary voltage from a battery or generator that is mounted on a vehicle and serves as a drive power supply, and generates a secondary voltage that drives the adjusting means 3, the control means 4, the dimming circuit 5, and the illumination means 6. This is an intermittent type or PFM type switching power supply circuit.

  The current load circuit 2 forcibly increases the current load of the switching power supply circuit 1 based on a switching signal from the control means 4 described later. The current load circuit 2 includes a resistor 21 that sets an increase amount of the load of the switching power supply circuit 1 and a transistor 22 that switches whether or not to apply a current load to the resistor 21 based on a switching signal from the control means 4 described later. And.

  The adjustment means 3 is an interface for adjusting the illumination brightness of the vehicle meter, and can be applied with a switch provided at a position where the vehicle user can operate on the instrument panel. The adjusting unit 3 outputs a signal based on the operation to the control unit 4. The adjusting means 3 is not based on a manual switch operation, and an external light sensor for automatically adjusting light according to the illuminance of external light can also be applied.

  The control unit 4 can be a microcomputer, sets dimming data based on a signal from the adjusting unit 3, and outputs a PWM control signal in an adjustment range corresponding to the dimming data to the dimming circuit 5.

  The control unit 4 determines whether or not the PWM control signal output to the dimming circuit 5 is equal to or greater than a predetermined adjustment range (duty ratio). This determination makes it possible to determine whether or not the load state on the illumination means 6 in the switching power supply circuit 1 is the light load mode (a state in which dark illumination is promoted). The control means 4 issues a switching signal for operating the current load circuit 2 to the transistor 22 of the current load circuit 2 in the light load mode. As a result, the switching power supply circuit 1 can supply a secondary power supply with a stable switching frequency because the load of the resistor 21 is increased, and thus the switching power supply circuit 1 is not in an extremely light load state.

  Further, the control means 4 issues a switching signal for stopping the operation of the current load circuit 2 to the transistor 22 of the current load circuit 2 when not in the light load mode (a state in which bright illumination is promoted). As a result, an unnecessary current load of the resistor 21 can be reduced, and a total load in the switching power supply circuit 1 can be reduced to suppress a ripple current and heat generation of the switching power supply circuit 1.

  The dimming circuit 5 adjusts the brightness of the illumination means 6 based on the PWM control signal from the control means 4. In this case, the dimmer circuit 5 can be a transistor, and adjusts the brightness by repeatedly supplying and stopping the power to the illumination means 6 based on the PWM control signal.

  A light emitting diode can be applied as the illumination means 6, and in this case, the indicator, dial, liquid crystal panel, etc. of the vehicle instrument are transmitted and illuminated by the power supplied via the dimming circuit 5.

  Such a vehicular display device includes an illuminating means 6, an adjusting means 3 for adjusting the brightness of the illuminating means 6, a dimming circuit 5 for driving the illuminating means 6, and a dimming set by the adjusting means 3. Control means 4 for controlling the dimming circuit 5 with a PWM control signal corresponding to the data, and an intermittent type or PFM for inputting a primary voltage and generating a secondary voltage for driving the illuminating means 6 through the dimming circuit 5 The control means 4 determines whether or not the adjustment range set by the switching power supply circuit 1 of the type and the adjustment means 3 is in the light load mode, and based on this determination result, the control is performed in the light load mode. And a current load circuit 2 for forcibly increasing the current load of the switching power supply circuit 1 based on a switching signal from the means 4.

  Therefore, since the illumination light source can be controlled at a stable switching frequency even in the case of a light load, it becomes easy to specify a frequency band in which switching noise occurs, and a vehicle display device can be obtained by a simple noise countermeasure. Can be designed. Further, when the load is not light, the operation of the current load circuit 2 can be stopped, and an unnecessary current load by the resistor 21 at this time is reduced, and the total load in the switching power supply circuit 1 is reduced. Thus, ripple current and heat generation of the switching power supply circuit 1 can be suppressed.

  Further, the current load circuit 2 includes a resistor 11 that sets an increase amount of the load of the switching power supply circuit 1, a transistor 12 that switches whether to apply a current load to the resistor 11 based on a switching signal of the control means 4, Thus, the operation of the current load circuit 2 can be switched based on the switching signal from the control means 4. Therefore, a stable switching frequency can be controlled with a simple configuration.

  The vehicle display device of the present invention has been described by way of example in the configuration of the embodiment described above, but the present invention is not limited to this, and the gist of the present invention is also achieved in other configurations. It goes without saying that various improvements and design changes can be made without departing from the scope.

The block diagram which shows the structure of embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Switching power supply circuit 2 Current load circuit 3 Adjustment means 4 Control means 5 Dimming circuit 6 Illumination means

Claims (2)

Lighting means;
Adjusting means for adjusting the brightness of the illumination means;
A light control circuit for driving the illumination means;
Control means for controlling the dimming circuit by a PWM control signal corresponding to dimming data set by the adjusting means;
An intermittent or PFM type switching power supply circuit for inputting a primary voltage and generating a secondary voltage for driving the illumination means via the dimming circuit;
It is determined by the control means whether the adjustment range set by the adjustment means is a light load mode,
Based on the determination result, in the light load mode, a current load circuit for forcibly increasing the current load of the switching power supply circuit based on a switching signal from the control means;
A vehicle display device characterized by comprising:
  The current load circuit includes a resistor for setting an increase amount of the load of the switching power supply circuit, and a transistor for switching whether or not to apply a current load to the resistor based on a switching signal of the control means. The vehicular display device according to claim 1.

Images