CN110177407B - Lighting control device for light emitting element and lighting device - Google Patents

Abstract

The invention provides a lighting control device for a light emitting element and a lighting device. In a lighting control device for a light emitting element, generation of an impact current flowing to a protection element when a power supply is turned on is suppressed. A lighting control device for performing lighting control of a light source including a light emitting element and a protection element connected in parallel with the light emitting element, the lighting control device comprising: an inductive element having one end connected to a current path connected to a power supply; a switching element connected between the other end of the inductive element and a reference potential end; a capacitive element connected between the other end of the inductive element and the reference potential end; and a bypass diode having one end connected to a current path connected to the power supply and a cathode of the light emitting element and the other end connected to the capacitive element and an anode of the light emitting element.

Description

Lighting control device for light emitting element and lighting device

Technical Field

The present invention relates to a technology for controlling the lighting state of a light-emitting element such as an LED.

Background technique

In recent years, light-emitting elements such as LEDs have been widely used in various lighting devices such as vehicle lamps. In controlling the lighting state of the light-emitting element, for example, a step-up and step-down circuit including a DC-DC converter is used (for example, refer to Patent Document 1). In addition, in order to protect the circuit from overcurrent, a protection element (for example, a Zener diode) is sometimes connected in parallel with the light-emitting element.

However, when using a step-up/step-down circuit to control the lighting state of a light-emitting element, an overcurrent may flow to a protection element connected in parallel with the light-emitting element when the power is turned on, sometimes causing damage to the protection element. This is because when the power is turned on, the capacitor connected to the output side of the step-up/step-down circuit is not charged, so a current path is formed from the power supply through the protection element to the capacitor, thereby generating an inrush current.

Prior Art Literature

Patent Document 1: Japanese Patent Application Publication No. 2013-109939

Summary of the invention

One of the objects of a specific embodiment of the present invention is to provide a technology capable of suppressing the generation of an inrush current flowing to a protection element when power is turned on in a lighting control device for a light emitting element.

A lighting control device (a) of one embodiment of the present invention is used to control the lighting of a light source, wherein the light source includes a light-emitting element and a protection element connected in parallel with the light-emitting element, and the lighting control device includes: (b) an inductive element, one end of which is connected to a current path connected to a power supply; (c) a switching element, which is connected between the other end of the inductive element and a reference potential end; (d) a capacitive element, which is connected between the other end of the inductive element and the reference potential end; and (e) a bypass diode, one end of which is connected to the current path connected to the power supply and the cathode of the light-emitting element, and the other end is connected to the capacitive element and the anode of the light-emitting element.

A lighting device according to one aspect of the present invention includes: the lighting control device described above; and a light source controlled by the lighting control device.

In this specification, the concept of “connection” includes not only a case where a circuit element is directly connected to another circuit element, but also a case where a circuit element is indirectly connected to another circuit element through the intervention of another element.

According to the above configuration, in the lighting control device for a light emitting element, it is possible to suppress the generation of an inrush current that flows to the protection element when the power is turned on.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram showing the overall structure of a vehicle lamp according to an embodiment.

FIG. 2 is a circuit diagram showing a detailed configuration of a lighting control circuit according to an embodiment.

FIG. 3 is a circuit diagram showing a detailed configuration of a lighting control circuit according to a comparative example.

Description of symbols

1: control substrate, 2: light source, 3: battery, 14: lighting control circuit, 21: coil, 22: diode, 23: transistor, 24: capacitor, 25: bypass diode, 31: light emitting element, 32: Zener diode.

Detailed ways

Fig. 1 is a block diagram showing the overall structure of a vehicle lamp according to an embodiment. The vehicle lamp shown in the figure receives power from a battery 3 to irradiate light, and is composed of a control substrate 1 and a light source 2. A relay 4 is connected between the battery 3 and the control substrate 1. The light source 2 is composed of one or more light-emitting elements (e.g., LEDs).

The control substrate 1 includes an input connector 11, a reverse connection protection circuit 12, an input filter 13, a lighting control circuit (lighting control device) 14, and a current detection circuit 15. The input connector 11 is a connector for connecting the control substrate 11 to the battery 3. The reverse connection protection circuit 12 is connected between the battery 3 and the lighting control circuit 14, and cuts off the voltage to protect the lighting control circuit 14 when the lighting control circuit 14 is reversely connected to the battery 3. The input filter 13 is a filter circuit that prevents noise components and the like from being input to the lighting control circuit 14.

The lighting control circuit 14 is used to control the lighting state of the light emitting element included in the light source 2 by receiving power from the battery 3, and is composed of a DC-DC converter, etc. The current detection circuit 15 detects the current flowing through the light emitting element of the light source 2. The lighting control circuit 14 performs lighting control in a manner such that the magnitude of the current detected by the current detection circuit 15 is constant.

FIG2 is a circuit diagram showing a detailed structure of a lighting control circuit according to an embodiment. In order to simplify the description, the current detection unit 15 is omitted from the diagram. The lighting control circuit 14 shown in the diagram includes a coil (inductive element) 21, a diode 22, a transistor 23, a capacitor (capacitive element) 24, and a bypass diode 25. The coil 21, the transistor 23, and the capacitor 24, among the above-mentioned components, constitute a boost circuit (DC-DC converter).

One end of the coil 21 is connected to a current path connected to the battery 3, and the other end is connected to the anode of the diode 22 and the drain of the transistor 23. The anode of the diode 22 is connected to the other end of the coil 21 and the drain of the transistor 23, and the cathode is connected to one end of the capacitor 24 and the anode of the light emitting element 31 of the light source 2.

The gate of transistor 23 is connected to a control unit (not shown), the drain is connected to an intermediate connection point between coil 21 and diode 22, and the source is connected to a reference potential terminal (ground terminal). A control signal is provided to the gate by the control unit. In addition, a field effect transistor is used as an example of a switching element here, but a bipolar transistor may also be used.

One end of the capacitor 24 is connected to the intermediate connection point between the diode 22 and the light emitting element 31 of the light source 2, and the other end is connected to the reference potential terminal. One end of the bypass diode 25 is connected to the current path connected to the battery 3, and the other end is connected to the other end of the diode 22 and one end of the capacitor 24.

The light source 2 includes a light emitting element 31 and a Zener diode (protection element) 32 connected in parallel to the light emitting element 31. The light emitting element 31 has an anode connected to the lighting control circuit 14 and a cathode connected to a current path connected to the battery 3.

The anode side of the Zener diode 32 is connected to the cathode side of the light emitting element 31, and the cathode side is connected to the anode side of the light emitting element 31. In other words, the anode side of the Zener diode 32 is connected to the current path connected to the battery 3, and the cathode side is connected to the lighting control circuit 14.

When the power is turned on to the lighting control circuit 14, the current flows as shown by the thick dotted line in the figure. Specifically, the current flowing out from the current path connected to the battery 3 reaches the capacitor 24 through the bypass diode 25, and charges the capacitor 24. By charging the capacitor 24, the potential difference between the two ends of the Zener diode 32 of the light source 2 is eliminated, so that overcurrent can be prevented from flowing through the Zener diode 32.

FIG3 is a circuit diagram showing the detailed structure of the lighting control circuit of the comparative example. The difference from the lighting control circuit of the above-mentioned embodiment is that the bypass diode 25 is not included. When the lighting control circuit 14a of this comparative example is powered on, the flow of current becomes the flow shown by the thick dotted line in the figure. Specifically, the current flowing out from the current path connected to the battery 3 reaches the capacitor 24 through the Zener diode 32 of the light source 2, and the capacitor 24 is charged. In the period before the capacitor 24 is charged, an overcurrent will instantaneously flow through the Zener diode 32, and the possibility of damage, etc., increases.

According to the above-described embodiment, in the lighting control device for a light emitting element, it is possible to suppress the generation of a rush current that flows to the protection element (Zener diode) when the power is turned on.

In addition, the present invention is not limited to the contents of the above-mentioned embodiments, and various modifications can be made and implemented within the scope of the main purpose of the present invention. For example, the structure of the boost circuit in the lighting control circuit shown in the above-mentioned embodiment is only an example and is not limited to this. In addition, the light source may include multiple light-emitting elements. In addition, a vehicle lamp is shown as an example of a lighting device, but the use of the lighting device is not limited to this.

Claims (3)

1. A lighting control device is characterized in that the lighting control device is used for controlling the lighting of a light source, the light source comprises a light-emitting element and a protection element connected with the light-emitting element in parallel,

The lighting control device includes:

an inductive element having one end connected to a current path connected to a power supply;

a switching element connected between the other end of the inductive element and a reference potential end;

A capacitive element having one end connected to the other end of the inductive element via a diode, and the other end connected to the reference potential end; and

And a bypass diode having one end connected to a current path connected to the power supply and a cathode of the light emitting element and the other end connected to the capacitive element and an anode of the light emitting element.

2. The lighting control device of claim 1, wherein,

The protection element is a zener diode connected in parallel such that an anode is connected to a cathode of the light emitting element and a cathode is connected to an anode of the light emitting element.

3.A lighting device, comprising:

the lighting control device according to claim 1 or 2; and

And a light source controlled by the lighting control device.