November 27, 2007

Low loss (VF = 1.7 V), with high withstand voltage and ultra-high speed (27 ns, the world's fastest class) achieved
FMXK Series Fast Recovery Diodes Developed
= Ideal for PFC circuits of LCD TVs, PDP TVs, etc. =

Sanken Electric Co., Ltd. announces the development of the FMXK Series, three types of fast recovery diodes which are ideal for power factor correction (PFC) circuits used in PDP TVs, LCD TVs, and other applications.  Having a high withstand voltage of 600 V, these diodes achieve both ultra-high speed (27 ns, the world’s fastest class) and low loss (VF = 1.7 V).  Sample shipments will begin in late November 2007, with shipments in volume planned to begin the following April.  Sample units will be priced at 170 yen for the 8 A FMXK-1086S, 200 yen for the 10 A FMXK-1106S, and 350 yen for the 20 A FMXK-2206S.
1. Development Background and Product Overview
  PFC circuits*1 which control higher harmonics and reduce reactive power are being mounted more and more in electronic devices such as flat-screen TVs and PC displays, irrespective of foreign or domestic use, in compliance with international harmonic current controls*2.

Switching circuits comprising elements such as ICs and diodes are frequently used in the PFC circuits of LCD and other flat-screen TVs.

Although the PFC circuit suppresses higher harmonic currents, the circuit itself consumes the power, resulting in the increase of power consumption throughout the entire electronic device. Therefore, loss reduction on diodes and other components in use has become an issue to be tackled.

Until now, loss caused by diodes has commonly been reduced by shortening reverse recovery time (trr).  Given the characteristics of diodes, shortening reverse recovery time (trr) leads to increased forward voltage (VF) and augmented loss, but this has been handled heretofore by sacrificing VF somewhat and shortening trr.

Sanken therefore has developed a proprietary new processing technology called local lifetime control technology*3 and has commercialized the FMXK Series fast recovery diodes by achieving both ultra-high speed (trr = 27 ns, max.) and low loss (VF = 1.7V), while maintaining a high withstand voltage of 600 V.

The FMXK Series also achieves noise reduction by reducing current change rate at the reverse recovery time.  Furthermore, considering the conditions under which the products are actually to be used, ultra-high speed over the entire range of operating temperatures (trr = 50 ns, typical, at 100°C) has been achieved by minimizing increase of trr at high temperatures.

*1. Power factor correction (PFC) circuits
These circuits are installed in electronic devices to clear the harmonic current controls and improve power losses.

*2.  Harmonic current controls
These are controls set by groups such as the International Electrotechnical Commission (IEC) and the Japan Industrial Standards (JIS) Committee.  If the load connected to a commercial power supply is an electronic equipment having a switching power supply, the current flowing through the equipment is not sinusoidal, but is a distorted current wave form with an out-of-sync pulse, known as a higher harmonic wave.  Higher harmonic waves generate reactive power, so this generation is regulated for the sake of energy conservation.

*3.  Local lifetime control technology
This is a proprietary process of Sanken, for optimizing and controlling factors such as the impurity concentration and diffusion structure within a process, for the sake of balancing speed increase and noise reduction.  Cores (recombination centers) must be formed to reduce the minority carrier, in order to increase speed.  The conventional technology uses heavy metal dispersion, but recombination centers are formed throughout and VF increases.  With the new technology, in the depth direction, instead of heavy metal being dispersed, scattering of charged particles allows recombination centers to be formed only where they are needed.
2. Features
(1)  Employs local lifetime control technology
<1> Ultra-high speed over entire range of operating temperatures

(trr = 27 ns, max., 4% reduction from conventional products; trr = 50 ns, typical, at 100°C, 7% reduction from conventional products)
<2> Low forward voltage
(VF = 1.7 V, max., 14% reduction from conventional products)
<3>  Low noise (Small current change rate at the reverse recovery time)
(dir/dt = 95A/μs, typical example)
(2) Lineup of three types: 8 A, 10 A, and 20 A.  Selectable to suit the circuit.
(3)  TO220F (full-mold) package
3. Applications
  • PFC circuits installed in flat-screen TVs and the like
  • Drive circuits for plasma display television panels
4. Electrical characteristics of the FMXK Series
Parameter Symbol Rating Unit
FMXK-1086S FMXK-1106S FMXK-2206S
Reverse voltage VRM 600 V
Forward current IF 8 10 10 × 2 A
Forward voltage VF 1.7 max. 1.7 max. 1.7 max. V
Reverse current IR 100 max. 100 max. 100 max. μA
Reverse recovery time trr 27 max. 27 max. 27 max. ns
reverse recovery time
H·trr 50 typ. 50 typ. 50 typ. ns
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