Thyristor Semiconductor Products Page 81 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1009 Examples of Gate Terminations Primary Purpose (1) Increase dv/dt capability (2) Keep gate clamped to ensure V DRM capability (3) Lower t q time Related Effect - Raises the device latching and holding current Primary Purpose (1) Increase dv/dt capability (2) Remove high frequency noise Related Effects (1) Increases delay time (2) Increases turn-on interval (3) Lowers gate signal rise time (4) Lowers di/dt capability (5) Increases t q time Primary Purpose (1) Decrease DC gate sensitivity (2) Decrease t q time Related Effects (1) Negative gate current increases holding current and causes gate area to drop out of conduction (2) In pulse gating gate signal tail may cause device to drop out of conduction Primary Purpose - Related Effects - positive and negative gate current may inhibit conduction or bring about sporadic anode current Primary Purpose (1) Supply reverse bias in off period (2) Protect gate and gate supply for reverse transients (3) Lower t q time Related Effects - Isolates the gate if high impedance signal source is used without sustained diode current in the negative cycle Zener optional Primary Purpose - Decrease threshold sensitivity Related Effects (1) Affects gate signal rise time and di/dt rating (2) Isolates the gate Primary Purpose - Isolate gate circuit DC component Related Effects - In narrow gate pulses and low impedance sources, I gt followed by reverse gate signals which may inhibit conduction Curves for Average Current at Various Conduction Angles SCR maximum average current curves for various conduction angles can be established using the factors for maximum average current at conduction angle of: 30 = 0.40 x Avg 180 60 = 0.56 x Avg 180 120 = 0.84 x Avg 180 The reason for different ratings is that the average current for conduction angles less than 180 is derated because of the higher RMS current connected with high peak currents. Note that maximum allowable case temperature (T C ) remains the same for each conduction angle curve but is established from average current rating at 180 conduction as given in the data sheet for any particular device type. The maximum T C curve is then derated down to the maximum junction (T J ). The curves illustrated in Figure J for the non-sensitive SCR series is 125 C. 80 85 90 95 100 105 110 115 120 125 0 2 4 6 8 10 12 14 16 Average On-state Current [I T (AV)] - Amps Maximum Allowable Case Temperature (T C ) - C 180 90 30 60 120 Current: Halfwave Sinusoidal Load: Resistive or Inductive Conduction Angle: As Given Below Case Temperature: Measured as Shown on Dimensional Drawings Conduction Angle 7.2 10.8 12.8 5.1 Figure AN1009.4 Typical Curves for Average On-state Current at Various Conduction Angles versus T C for a SXX20L SCR. Double-Exponential Impulse Waveform A double-exponential impulse waveform or waveshape of current or voltage is designated by a combination of two numbers (t r /t d or t r x t d s). The first number is an exponential rise time (t r ) or wave front and the second number is an exponential decay time (t d ) or wave tail. The rise time (t r ) is the maximum rise time permitted. The decay time (t d ) is the minimum time permitted. Both the t r and the t d are in the same units of time, typically microseconds, designated at the end of the waveform description as defined by ANSI/IEEE C62.1-1989. Miscellaneous Design Tips and Facts (continued)

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