JP2015080955A - Power source circuit of vehicle instrument - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source circuit of a vehicle instrument capable of protecting an electronic component even in a case where a fluctuation of a power source voltage that is supplied to a vehicle instrument becomes violent.SOLUTION: A power source circuit of a vehicle instrument supplies power supply to a control circuit 5 or the like which is a load circuit. It includes a surge voltage suppressing circuit 1 between a battery power source B and the load circuit. A surge current suppressing circuit 2 is provided between the surge voltage suppressing circuit 1 and the load circuit. As the load circuit the control circuit 5 is provided. The control circuit 5 controls driving of a switching circuit 3 which suppresses occurrence of a dark current in a state a vehicle is stopped, in the surge current suppressing circuit 2.

Description

  The present invention relates to a power supply circuit for supplying stable power to a load circuit constituting a vehicle meter.

  Conventionally, as a vehicle instrument for displaying vehicle information such as a vehicle speed and an accumulated travel distance, there is one disclosed in Patent Document 1, for example. These vehicle meters are connected to a battery that can stably supply power, and display various vehicle information using this power. Various sensors mounted on the vehicle also operate based on the power supply from the battery.

  However, in the case of a vehicle with a small battery and a small power supply capacity mounted on the vehicle, or a vehicle with a small power supply capacity due to power consumption such as discharge, the proportion of power supply voltage supplied from the vehicle generator to the vehicle meter is high. For example, as disclosed in Patent Document 2, an input electrolytic capacitor or a transistor provided in the power supply circuit to prevent instantaneous interruption is caused because the power supply is intermittent and the voltage fluctuation becomes severe. And a surge protection circuit composed of a Zener diode and a base resistor.

JP 2002-1104056 A Japanese Patent Laid-Open No. 64-23722

  However, when a surge voltage / power supply noise is applied, or in a vehicle with a large power supply ratio from the generator, a power supply with a large voltage fluctuation is supplied to the vehicle instrument, particularly at the time of starting the engine. For this reason, the electrolytic capacitor is repeatedly charged, and an inrush current frequently flows through the transistor. As a result, when this configuration is applied to the vehicle instrument, electronic components such as transistors and electrolytic capacitors may be damaged, which is a problem.

  SUMMARY OF THE INVENTION Accordingly, the present invention focuses on the above-mentioned problems, and an object thereof is to provide a power circuit for a vehicle instrument that can protect electronic components even when the power supply voltage supplied to the vehicle instrument varies greatly. And

  A power supply circuit for a vehicle instrument according to the present invention is a power supply circuit for a vehicle instrument that supplies power to a load circuit, and includes a surge voltage suppression circuit between a battery power supply and the load circuit, and the surge voltage suppression circuit and the load A surge current suppression circuit is provided between the circuit and the circuit.

  The load circuit includes a control unit, and the control unit drives and controls a switch circuit that suppresses generation of dark current when the vehicle is in an operation stop state in the surge current suppression circuit.

The figure which shows the circuit structure in embodiment of this invention.

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

  FIG. 1 is a diagram showing a circuit configuration of a power supply circuit of a vehicle meter, and shows a configuration from stabilization of power supplied from a battery power supply B of the vehicle to supply to a load circuit.

  The vehicle meter A is connected to an on-vehicle battery power source B and an ignition switch IG, and includes a surge voltage suppression circuit 1, a surge current suppression circuit 2, a switch circuit 3, a stabilized power circuit 4, and a control circuit (control means) 5. It is provided on the circuit board. The battery power source B is equipped with a generator and a regulator (not shown).

  A constant voltage, for example, a 5 V voltage supplied to a load circuit such as the control circuit 5 is supplied from a battery power supply B mounted outside the vehicle meter A via the stabilized power supply circuit 4, and the battery power supply B and the stabilized power supply are supplied. 4, a surge voltage suppression circuit 1 and a surge current suppression circuit 2, and a capacitor C for preventing momentary disconnection in which one end is grounded.

  The capacitor C has a positive electrode connected to a wiring between the transistor TR2 and the load-side stabilized power supply circuit 4, and a negative electrode is grounded. The capacity of the capacitor C is set based on the current consumption of the load so that the fluctuation of the voltage supplied to the load side can be smoothed.

  The surge voltage suppression circuit 1 can be the same as the surge protection circuit shown in the conventional example, and a transistor (for example, an NPN transistor) TR1 interposed in the connection wiring between the battery power supply B and the stabilized power supply circuit 4 includes: The cathode of the Zener diode ZD is connected to the base terminal of the transistor TR1, and the anode of the Zener diode ZD is connected to the ground. The Zener diode ZD and the base terminal of the transistor TR1 are connected to the collector terminal via the resistor R1. This resistor R1 is used to limit the current flowing through the Zener diode ZD when a surge voltage is applied. The surge voltage can be absorbed by the action of the Zener diode ZD.

  The surge current suppression circuit 2 is configured by using the transistor TR2 and the resistors R2, R3, and R4. The path through which the current flows through the resistor R4 by the switch means 3 and the transistor TR2 that is limited by the resistors R2 and R3. The flow path can be switched. Since the surge current suppression circuit 2 can limit the maximum load current, the surge current flowing through the transistor TR1 can be limited, and electronic components such as the transistor TR1 and the capacitor C can be protected.

  The switch circuit 3 switches the current path of the surge current suppression circuit 2 based on a control signal from the control means 5, and supplies a signal adjusted for operating the transistor TR2 to the base terminal of the transistor TR2. .

  The stabilized power supply circuit 4 generates drive power for the control circuit 5 and the like, and in this case, a regulator for generating 5V is applied. The stabilized power circuit 4 outputs the driving power when the battery power B is connected regardless of the state of the ignition switch IG.

  The control circuit 5 can be a microcomputer that is driven by power supply from the stabilized power supply circuit 4 and controls the display of the vehicle meter A based on vehicle information input via a cable (not shown). It is. The control circuit 5 can detect the state of the ignition switch IG, and outputs a control signal for controlling the switch circuit 3 based on this state.

  The control circuit 5 controls the switch circuit 3 so that the base current of the transistor TR2 flows when the ignition switch IG shifts from OFF to ON, and the surge current can be suppressed by the transistor TR2. At this time, even if the engine is started by the vehicle user's starter operation, each component can be protected from the surge current.

  Further, the control circuit 5 outputs a control signal for stopping the base current of the transistor TR3 when the ignition switch IG shifts from OFF to ON, and suppresses current from flowing through the resistor R2 and R3 paths, Power consumption while the vehicle is stopped can be suppressed. In this case, current flows through the resistor R4 in the surge current suppression circuit 2, and the stabilized power supply circuit 4 and the control circuit 5 in the power saving mode can be operated.

  Therefore, when the ignition switch IG is on, which has a large voltage fluctuation of the power source that operates the engine and the generator, the electronic components can be protected from surge voltage and surge current, while the power consumption is low and stable with only battery power source. In the ignition switch IG off state, which is a power supply state, the surge current suppression circuit 2 can be switched to a state with a small dark current (a current path with reduced power consumption).

  The vehicle instrument power supply circuit is a vehicle instrument power supply circuit that supplies power to the control circuit 5 or the like serving as a load circuit, and includes a surge voltage suppression circuit 1 between the battery power supply B and the load circuit. A surge current suppression circuit 2 is provided between the suppression circuit 1 and the load circuit.

  Therefore, even when the fluctuation of the power supply voltage supplied to the vehicle meter A becomes severe, the power circuit of the vehicle meter can protect the electronic components mounted on the transistor, the capacitor, and the load circuit.

  Further, the load control circuit includes a control circuit 5, and the control circuit 5 controls the surge current in the surge current suppression circuit 2 by driving and controlling the switch circuit 3 that suppresses the generation of dark current when the vehicle is stopped. Even if the circuit 2 is configured, it can be switched to a small power consumption state. In the above-described embodiment, the vehicle is determined to be in an operation stop state based on the OFF state of the ignition switch IG, and the starter device is switched to the surge current countermeasure state when the ignition switch IG that is the operating condition is ON. Can be migrated.

  Although the present invention has been described by way of example in the configuration of the above-described embodiment, the present invention is not limited to this, and various other configurations can be used without departing from the spirit of the present invention. Of course, it is possible to improve the design and change the design. For example, the control circuit 5 has been described as an example of the load circuit. However, when the ignition switch IG is on, a light source including a light emitting diode that is driven and controlled by the control circuit 5, a liquid crystal display, and a pointer for indicating a measured value are driven. A circuit for displaying vehicle information such as a motor can also be configured as a load circuit.

  The present invention can be applied, for example, as a power circuit for a vehicle instrument mounted on a moving body including an automobile, a motorcycle, an agricultural machine, or a construction machine.

DESCRIPTION OF SYMBOLS 1 Surge voltage suppression circuit 2 Surge current suppression circuit 3 Switch circuit 4 Stabilization power supply circuit 5 Control circuit (control means)
A Vehicle instrument B Battery power supply C Capacitors TR1, TR2, TR3 Transistors R1, R2, R3, R4 Resistor ZD Zener diode

Claims (2)

In the power circuit of a vehicle instrument that supplies power to the load circuit,
A surge voltage suppression circuit is provided between the battery power source and the load circuit,
A power supply circuit for a vehicle instrument, wherein a surge current suppression circuit is provided between the surge voltage suppression circuit and the load circuit. A control means is provided as the load circuit,
2. The vehicle instrument power supply circuit according to claim 1, wherein the control unit drives and controls a switch circuit that suppresses generation of dark current when the vehicle is in an operation stop state in the surge current suppression circuit. 3.

Images