JP3105302U - Constant current LED board - Google Patents

Abstract

An object of the present invention is to realize a constant-current LED board with small variations in current, high efficiency, and easy power supply design in applications in which a large number of LEDs are simultaneously driven with a uniform current.
A constant current circuit (3) is provided for each set of LEDs (2) connected in series, and the output current of each constant current circuit is equalized to equalize the current of all LEDs. As a result, even when a battery (such as a lead storage battery) is used as a power supply, there is no need to provide a constant voltage circuit (such as a DC-DC converter), and a wide voltage range from a low voltage at the end of discharging to a high voltage at the completion of charging. A constant illuminance can be obtained in the range, and there is no efficiency reduction due to the constant voltage circuit.
[Selection] Figure 2

Description

  The present invention relates to a constant-current LED board having a small variation in current and easy to design a power supply.

Lighting or display devices that use LEDs have the advantage that power consumption is small and hardly deteriorated for the brightness, so that there is an advantage that the need for replacement can be saved, and the lighting and display devices are practically used in various fields.
Among them, an ultra-bright white LED can obtain brightness higher than that of a conventional incandescent light bulb, and has recently been receiving particular attention because of its low price and stable quality.
When LEDs are used for lighting, it is usually necessary to illuminate a large number of LEDs side by side since the required brightness cannot be obtained with one LED. However, the characteristics of the LEDs used may not be completely uniform. Therefore, if the same voltage is applied by connecting in parallel, the current of each LED varies.
On the other hand, if all are connected in series, the current will be uniform, but a high DC voltage will be required.In general, several LEDs and a resistor to reduce the variation in current are connected in series to form a set. Is widely used as a practical circuit.

  However, when the resistance value is increased, the current approaches a constant value, but the power loss increases. Therefore, there is a disadvantage that a relatively small resistance value has to be used while allowing some variation.

  In lighting applications, this drawback is a major obstacle for efficient use of LEDs. Specifically, there has been a problem that an excessive current flows through some of the LEDs to shorten the service life, or that an excessively small current cannot provide a required illuminance.

  As a remedy, there is a method of using a constant current circuit to make the current of each LED uniform. FIG. 1 is an explanatory diagram showing a mounting form of an electric circuit by this method, and is an external view as viewed from a mounting surface of an LED. In FIG. 1, 2 is an LED, and 3 is a constant current circuit. However, an area necessary for mounting the constant current circuit must be secured.

  The problem to be solved is that a large number of LEDs cannot be driven with a uniform current under the conditions of a practical power supply voltage and low cost and high efficiency.

  The most important feature of the present invention is to provide a constant current circuit for each set of several LEDs connected in series in order to drive a large number of LEDs with a uniform current.

  Since the constant current LED board of the present invention is provided with a constant current circuit for each set of several LEDs connected in series, the current of each LED can be equalized without connecting all the LEDs in series. This can be realized within a practical power supply voltage range, and there is an advantage that there is no problem even if the power supply voltage fluctuates within an allowable range.

  The purpose of providing a constant current for each set of several LEDs connected in series has been realized without using a chip transistor and a chip resistor to minimize the mounting area and increase the cost.

  FIG. 2 is a circuit diagram of one embodiment of the present invention. Reference numeral 4 denotes a DC power supply.

  The constant current circuit 3 has a function of making the current flowing through a pair of LEDs 2 connected in series constant. However, there is an appropriate range for the voltage of the DC power supply. Since the subject of the present invention is a circuit configuration for driving a large number of LEDs with a uniform current, the description of the constant current circuit is omitted.

  In recent years, transistors and resistors have been made into chips for surface mounting and have become very inexpensive. By using them, an inexpensive and compact constant current circuit is realized. If mass production is possible, further cost reduction can be expected by using IC.

  As a simple method of obtaining a constant current, a constant current diode can be used, but the cost is high and a required current value may not be obtained in some cases.

  In the embodiment of FIGS. 1 and 2, if the constants of the constant current circuits are made uniform by the constant current circuits provided for each pair of LEDs 2 connected in series, the current becomes substantially uniform as a whole. Even when a battery (such as a lead-acid battery) is used as the power supply, there is no need to provide a constant voltage circuit (such as a DC-DC converter), and it is constant over a wide voltage range from a low voltage at the end of discharge to a high voltage at the completion of charging. Illuminance is obtained, and there is no reduction in efficiency due to the constant voltage circuit.

  The constant current LED board of the present invention can be directly connected to a power supply with a large fluctuation in power supply voltage, such as a battery, without providing a circuit in the middle. Since long and efficient lighting can be easily obtained, it can be applied to various lighting applications or decorative applications.

It is explanatory drawing which showed the implementation method of the constant current LED board. (Example of mounting form) It is explanatory drawing which showed the implementation method of the constant current LED board. (Circuit example)

Explanation of reference numerals

1 board 2 LED
3 Constant current circuit 4 DC power supply

Claims (1)

A constant-current LED characterized by dividing a large number of LEDs into a plurality of groups, providing a constant current circuit for each group, and equalizing the currents of all the LEDs by equalizing the output currents of the respective constant current circuits. substrate.

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