Thyristor Semiconductor Products Page 74 Thyristor

2014 Littelfuse, Inc. Specifications are subject to change without notice. Revised: 12/14/14 Teccor brand Thyristors AN1008 Introduction Data sheets for SCRs and Triacs give vital information regarding maximum ratings and characteristics of Thyristors. If the maximum ratings of the Thyristors are surpassed, possible irreversible damage may occur. The characteristics describe various pertinent device parameters which are guaranteed as either minimums or maximums. Some of these characteristics relate to the ratings but are not ratings in themselves. The characteristic does not define what the circuit must provide or be example, a minimum value is indicated for the dv/dt because this value depicts the guaranteed worst-case limit for all devices of the specific type. This minimum dv/dt value represents the maximum limit that the circuit should allow. Maximum Ratings V RRM : Peak Repetitive Reverse Voltage -- SCR The peak repetitive reverse voltage rating is the maximum peak reverse voltage that may be continuously applied to the main terminals (anode, cathode) of an SCR. (Figure AN1008.1) An open-gate condition and gate resistance termination is designated for this rating. An increased reverse leakage can result due to a positive gate bias during the reverse voltage exposure time of the SCR. The repetitive peak reverse voltage rating relates to case temperatures up to the maximum rated junction temperature. Reverse Breakdown Voltage Forward Breakover Voltage Specified Minimum Off - State Blocking Voltage (V DRM ) +I -I +V -V Minimum Holding Current (I H ) Voltage Drop (v T ) at Specified Current (i T ) Latching Current (I L ) Off - State Leakage Current - (I DRM ) at Specified V DRM Specified Minimum Reverse Blocking Voltage (V RRM ) Reverse Leakage Current - (I RRM ) at Specified V RRM Figure AN1008.1 V-I Characteristics of SCR Device V DRM : Peak Repetitive Forward (Off-state) Voltage SCR The peak repetitive forward (off-state) voltage rating (Figure AN1008.1) refers to the maximum peak forward voltage which may be applied continuously to the main terminals Explanation of Maximum Ratings and Characteristics for Thyristors (anode, cathode) of an SCR. This rating represents the maximum voltage the SCR should be required to block in the forward direction. The SCR may or may not go into conduction at voltages above the V DRM rating. This rating is specified for an open-gate condition and gate resistance termination. A positive gate bias should be avoided since it will reduce the forward-voltage blocking capability. The peak repetitive forward (off-state) voltage rating applies for case temperatures up to the maximum rated junction temperature. Triac The peak repetitive off-state voltage rating should not be surpassed on a typical, non-transient, working basis. (Figure AN1008.2) V DRM should not be exceeded even instantaneously. This rating applies for either positive or negative bias on main terminal 2 at the rated junction temperature. This voltage is less than the minimum breakover voltage so that breakover will not occur during operation. Leakage current is controlled at this voltage so that the temperature rise due to leakage power does not contribute significantly to the total temperature rise at rated current. Breakover Voltage Specified Minimum Off-state Blocking Voltage (V DRM ) +I -I +V -V Minimum Holding Current (I H ) Voltage Drop (v T ) at Specified Current (i T ) Latching Current (I L ) Off-state Leakage Current - (I DRM ) at Specified V DRM Figure AN1008.2 V-I Characteristics of Triac Device I T : Current Rating SCR For RMS and average currents, the restricting factor is usually confined so that the power dissipated during the on state and as a result of the junction-to-case thermal resistance will not produce a junction temperature in excess of the maximum junction temperature rating. Power dissipation is changed to RMS and average current The average current for conduction angles less than 180 is derated because of the higher RMS current connected with high peak currents. The DC current rating is higher than the average value for 180 conduction since no RMS component is present.

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