JP2000306685A - LED lighting circuit - Google Patents

Abstract

(57) [Summary] [PROBLEMS] To reduce a current flowing to an LED when an AC power supply is turned on. SOLUTION: A plurality of AC power supplies 1 are connected in series via at least a capacitor 2 and a rectifier 3 according to the purpose.
An LED lighting circuit for connecting the ED4, wherein a resistor 5 is connected in series with the LED4, and the resistor 5 and the LED
The constant voltage diode 6 is connected in parallel to the series circuit of FIG.
At the time of steady lighting of the ED 4, the voltage across the series circuit of the resistor 5 and the LED 4 does not reach the breakover voltage of the constant voltage diode 6. This is an LED lighting circuit in which the voltage between both ends reaches the breakover voltage of the constant voltage diode 6 and the constant voltage diode 6 can be turned on.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to an LED (light emitting diode) lighting circuit.

[0002]

2. Description of the Related Art In order to reduce the cost of an LED lighting circuit connected to an AC power supply, an LED is connected to the AC power supply via at least a capacitor and a rectifying element, and the capacitance of the capacitor is selected. An LED lighting circuit in which the current at the time of steady lighting is adjusted to a predetermined current is assumed.

[0003]

However, when the AC power supply is turned on, a large charging current transiently flows through the capacitor to generate an inrush current, which exceeds the instantaneous maximum rated current of the LED, and the LED is destroyed. It should be noted that there is a problem to be solved that may cause fear. The present invention has been made in view of such problems to be solved, and has as its object to reduce a current flowing through an LED when an AC power supply is turned on.

[0004]

Means for solving the problems are as described in the claims.

[0005]

BEST MODE FOR CARRYING OUT THE INVENTION Next, an embodiment of the present invention will be described. However, this is merely an exemplary embodiment adopted based on the present invention, and the present invention is described based on matters specific to the embodiment. Therefore, the technical scope of the present invention should be determined based on the matters stated in the claims and matters substantially equivalent to the matters.

The illustrated embodiment is an LED lighting circuit in which a plurality of LEDs 4 are connected in series to an AC power supply 1 via at least a capacitor 2 and a rectifier 3 according to the purpose, and a resistor 5 is connected in series with the LEDs 4. A constant voltage diode 6 is connected in parallel with the series circuit of the resistor 5 and the LED 4.
The voltage across the ED4 series circuit is
Does not reach the breakover voltage (Zener voltage) of
When an inrush current is generated by turning on the AC power supply 1, the resistor 5
This is an LED lighting circuit in which the voltage across the series circuit of the LED 4 and the LED 4 reaches the breakover voltage of the constant voltage diode 6 and the constant voltage diode 6 can be turned on.

The resistor 7 is connected to the capacitor 2 if necessary.
Are connected in series to adjust the current value at the time of steady lighting of the LED 4 and contribute to the reduction of the inrush current value. And
By operating the switch 8, the AC power supply 1 is supplied to the LED lighting circuit or cut off. The switch 8 may not be provided, and the order of the capacitor 2, the rectifying element 3, and the resistor 7 is not limited to the illustrated case.

According to the present embodiment, the constant voltage diode 6 having a breakover voltage higher than the voltage across the series circuit of the resistor 5 and the LED 4 when the LED 4 is steadily lit.
Is selected. Therefore, at the time of steady lighting of the LED 4, the constant voltage diode 6 is kept off, and there is no unnecessary power consumption. When an inrush current is generated by turning on the AC power supply 1, the resistance 5
The inrush current flows through the resistor 5 and the voltage across the resistor 5 increases. Then, the voltage between both ends of the series circuit of the resistor 5 and the LED 4 also increases, reaches the breakover voltage of the constant voltage diode 6, and the constant voltage diode 6 is turned on. Therefore, since the rush current that tries to flow into the LED 4 also flows through the constant voltage diode 6, the current flowing through the LED 4 can be prevented from exceeding the maximum rated current at that moment, and LE
D4 can be prevented from being broken.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 AC power supply 2 Capacitor 3 Rectifier 4 LED 5 Resistance 6 Constant voltage diode

Claims (1)

[Claims] 1. An LED lighting circuit for connecting an LED to an AC power supply via at least a capacitor and a rectifying element, wherein a resistor is connected in series to the LED, and a constant voltage diode is connected in parallel to a series circuit of the resistor and the LED. During steady operation of the LED, the voltage across the series circuit of the resistor and the LED does not reach the breakover voltage of the constant voltage diode, and when an inrush current occurs due to the turning on of an AC power supply, the series circuit of the resistor and the LED is connected. An LED lighting circuit in which a voltage between both ends reaches a breakover voltage of the constant voltage diode, and the constant voltage diode is enabled.