Thyristor Semiconductor Products Page 78 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1008 II III IV I 0 1.0 2.0 3.0 4.0 5.0 6.0 2 4 6 8 10 12 14 I - mA Figure AN1008.9 Typical Triac Latching (I L ) Requirements for Four Quadrants versus Gate Current (I GT ) I H : Holding Current -- SCR and Triac The holding current is the DC principal on-state current below which the device will not stay in regeneration/on state after latching and gate signal is removed. This current is equal to or lower in value than the latching current (Figure AN1008.1 and Figure AN1008.2) and is related to and has the same temperature dependence as the DC gate trigger current shown in Figure AN1008.10. Both minimum and maximum holding current may be important. If the device is to stay in conduction at low-anode currents, the maximum holding current of a device for a given circuit must be considered. The minimum holding current of a device must be considered if the device is expected to turn off at a low DC anode current. Note that the low DC principal current condition is a DC turn-off mode, and that an initial on-state current (latching current) is required to ensure that the Thyristor has been fully turned on prior to a holding current measurement. Figure AN1008.10 Normalized DC Holding Current versus Case Temperature dv/dt, Static: Critical Rate-of-rise of Off-state Voltage - SCR and Triac Static dv/dt is the minimum rate-of-rise of off-state voltage that a device will hold off, with gate open, without turning 0 1.0 2.0 3.0 4.0 -65 -15 +65 +25 +125 -40 Junction Temperature (T J ) - C I H (T J = 25 C) Ratio of I H INITIAL ON-STATE CURRENT = 400 mA dc on. Figure AN1008.11 illustrates the exponential definition. This value will be reduced by a positive gate signal. This characteristic is temperature-dependent and is lowest at the maximum-rated junction temperature. Therefore, the characteristic is determined at rated junction temperature and at rated forward off-state voltage which is also a worst- case situation. Line or other transients which might be applied to the Thyristor in the off state must be reduced, so that neither the rate-of-rise nor the peak voltage are above specifications if false firing is to be prevented. Turn-on as result of dv/dt is non-destructive as long as the follow current remains within current ratings of the device being used. Critical dv/dt dv = 0.63 V D t t = RC 0 dt t 63% of V D V D Figure AN1008.11 Exponential Rate-of-rise of Off-state Voltage Defining dv/dt dv/dt, Commutating: Critical Rate-of-rise of Commutation Voltage -- Triac Commutating dv/dt is the rate-of-rise of voltage across the main terminals that a Triac can support (block without switching back on) when commutating from the on state in one half cycle to the off state in the opposite half cycle. This parameter is specified at maximum rated case temperature (equal to T J ) since it is temperature- dependent. It is also dependent on current (commutating di/dt) and peak reapplied voltage (line voltage) and is specified at rated current and voltage. All devices are guaranteed to commutate rated current with a resistive load at 50 Hz to 60 Hz. Commutation of rated current is not guaranteed at higher frequencies, and no direct relationship can be made with regard to current/ temperature derating for higher-frequency operation. With inductive loading, when the voltage is out of phase with the load current, a voltage stress (dv/dt) occurs across the main terminals of the Triac during the zero-current crossing. (Figure AN1008.12) A snubber (series RC across the Triac) should be used with inductive loads to decrease the applied dv/dt to an amount below the minimum value which the Triac can be guaranteed to commutate off each half cycle. Commutating dv/dt is specified for a half sinewave current at 60 Hz which fixes the di/dt of the commutating current. The commutating di/dt for 50 Hz is approximately 20% lower while I RMS AN1008.4) Explanation of Maximum Ratings and Characteristics for Thyristors (continued)

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