LED failure prevention

SIDAC(Bidirectional Thyristor) Development


Shindengen Electric Manufacturing Co., Ltd. (headquartered in Otemachi, Chiyoda-ku, Tokyo, Japan)

has developed SIDACs(bidirectional thyristors) optimal for combating total darkening of LEDs due to open faults. Mass production began in April 2010.

 The product we have now developed comes in two types, K1VZL09, with a 10 V break-over voltage (typ.), and K1VZL20, with 20 V. Connect these bidirectional thyristors in parallel with LEDs in a light fixture, and, when an LED fails in open mode, they can bypass just the LED that broke, maintain the lighting of the other LEDs connected serially, and prevent total darkening.

 We are expanding our business mainly in fields such as signals and emergency guide lights in which darkening is not acceptable, and we are also moving into the automotive market, where LED installation is increasing.

 These products were displayed at the 2nd LED/OLED Lighting Technology Expo: Lighting Japan (sponsored by Reed Exhibitions Japan) at Tokyo Big Sight from April 14 (Wed.) to April 16 (Fri.).



● LED open fault bypass device to prevent total darkening
● Bypass function maintained even in power reset
● The industry's first low holding current IH (20 mA max.)
● Low loss in on state (during bypass function)
  (Compared to Zener diodes, 1/5 or less)
● Uses a compact surface mounting 1F package ideal for saving space


 As environmental awareness rises, LED lighting is gradually penetrating markets. Correspondingly, light fixtures that shine LEDs in serial connection are starting to become common.

 In light fixtures that connect LEDs serially, when one LED has an open fault, all the other serially connected LEDs darken. What's more, the LED with the open fault may cause other LEDs to break by inviting raised voltage (in a constant current circuit).

 To avoid such mishaps, the old way was to connect Zener diodes (hereafter ZDs) in parallel with the LEDs. However, the ZDs used for bypass had high Vz (reverse voltage), more than the LEDs'. They would emit much heat in the on state (using the bypass function), making issues to address in the circuit.

 We have long paid attention to the characteristics of our proprietary SIDAC power semiconductors, used for lightning surge protection, pulse generators, etc. Thus we have developed 2 power semiconductors optimally suited to addressing LED failure.

 SIDACs have a reliable protection function: triggered by a slight voltage increase, they transition to the on state immediately when breakover voltage is applied. They also have low forward loss, only about 1/5 that of ZDs', allowing for reduction in the number of components to address heat.

 Mainly in signals and emergency guide lights in which darkening is not acceptable, we are expanding into street lighting, and we intend to get into the automotive market as well.



●K1VZL09 static characteristics

Diode curve tracer voltage-current waveform

●Experimental verification

K1VZL09, connected in parallel, bypasses the broken LED and keeps the other LEDs shining.


3.Product Names and Main Specifications Chart, Form

Product name Recommended No.
of serial LEDs
voltage (typ.) [V]
Holding current
(max.) [mA]
Off-state current
(max.) [µA]

On-state current
(max.) [A]

On-state voltage
(max.) [V]
K1VZL09 1~2S -40~+125 10 20 5 1 1.2
K1VZL20 3~5S 20

  Form: L 5 mm, W 2.5 mm, H 2 mm 2-terminal surface mounting pkg. (1F-PKG)



4. Applications

  • Lights for which darkening is unacceptable, including street lights, emergency guide lights, floodlights, and signals
  • Lights difficult for maintenance, including downlights and work lights
  • Automobiles, etc.

5.Production Plant

  • Akita Shindengen Co., Ltd. and others.

6.Sample Timeframe, Mass Production Timeframe

  • Sample timeframe: Both K 1VZL09 and K1VZL20 from Feb. 2010
  • Mass production timeframe: Both K 1VZL09 and K1VZL20 planned for Apr. 2010

7.Sample Price

  • Sample price: Both K1VZL09 and K1VZL20 are 80 yen


 Shindengen Electric Manufacturing Co., Ltd.
 Electronic Device Div. Electronic Device Div. Group Electronic Device Sales Div. Sales Dept.

  * Listed information were update on March 25nd, 2010.