5 Pages
English

In today's power converter the commutation speed of the transistor and the operating frequencies are higher and higher Fast diodes used for freewheel snubber and rectifier functions become one of the main causes of the power losses In the range of 600V 1200V SGS THOMSON has developed a new family of ultrafast diodes Taking into account these new constraints which are different from one application to another SGS THOMSON proposes two series TURBOSWITCH ”A” and TURBOSWITCH ”B” The specific characteristics of these two series offer to the designer a double choice allowing him to use the best diode in this application

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Niveau: Supérieur, Doctorat, Bac+8
In today's power converter, the commutation speed of the transistor and the operating frequencies are higher and higher. Fast diodes used for freewheel, snubber, and rectifier functions become one of the main causes of the power losses. In the range of 600V-1200V, SGS THOMSON has developed a new family of ultrafast diodes. Taking into account these new constraints which are different from one application to another, SGS-THOMSON proposes two series : TURBOSWITCH ”A” and TURBOSWITCH ”B”. The specific characteristics of these two series offer to the designer a double choice, allowing him to use the best diode in this application. I. INTRODUCTION The choice of the optimum diode for a given applicationdependson the estimation of the power losses generated by the diode. This note explains how to calculate the different losses with information given in the datasheet and shows the difference between TURBOSWITCH”A” and TURBOSWITCH”B” and their respective advantages. II. LOSSES CALCULATION II.1 Conduction losses Conduction losses are estimated with the classical formula : Pcon = Vto IF(AV) + rd I2F(RMS) Vto : Threshold voltage (Fig.1) rd : Dynamical resistance (Fig.1) IF(AV) : Average current IF(RMS) : RMS current II.2. Turn on losses When the diode turns ON, the voltage across the diode increases to VFP (Peak forward voltage) before it decreases to 1.1 VF at the time tFR (Forward recovery time) (Fig.

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) APPLICATION NOTE NEW HIGH VOLTAGE ULTRA-FAST DIODES : TM THE TURBOSWITCHA and B SERIES B. Rivet In today's power converter, the commutation Fig.1 :Approximation of the forward characteristic speed of the transistor and the operating frequencies are higher and higher. Fast diodes used for freewheel, snubber, and I I F F rectifier functions become one of the main causes of the power losses. In the range of 600V-1200V, SGS THOMSON has developed a new family of ultrafast diodes. rd Taking into account these new constraints which are different from one application to another, SGS-THOMSON proposes two series : TURBOSWITCH ºAº and TURBOSWITCH ºBº. The specificcharacteristics of these two series offer to the designer adouble choice, allowing himVto V V F F to use the best diode in this application.
I. INTRODUCTION
The choice of the optimum diode for a given application depends on the estimation of the power losses generated by the diode. This note explains how to calculate the different losses with information given inthe datasheet and shows the difference between TURBOSWITCHºAº and TURBOSWITCHºBº and their respective advantages.
II. LOSSES CALCULATION
II.1 Conduction losses
Conduction losses are estimated with the classical formula :
Vto rd IF(AV) IF(RMS)
2 Pcon = VtoIF( AV)+ rd IF(RMS)
: Threshold voltage(Fig.1) : Dynamical resistance (Fig.1) : Averagecurrent : RMS current
TM : TURBOSWITCH is a trademark of SGS-THOMSON MIcroelectronics AN601/0193
II.2. Turn on losses When the diode turns ON, the voltage across the diode increases to VFP(Peak forward voltage) before it decreases to 1.1 VFat the time tFR (Forward recovery time) (Fig.2). Fig.2 :Turn ON waveforms
I F
V FP
1.1V F
(dIF/dt)ON
V F
t FP
t
t
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