STR83145

STR83145 AND STR84145 INTERIM ISSUE (subject to change without notice) August 16, 1994 Data Sheet 28190 LATCHED, UNIVERSAL INPUT-VOLTAGE SWITCHES Intended for power supplies with universal inputs (85 V to 265 V rms), the STR83145 and STR84145 latched, universal input-voltage switches incorporate timing, control, and drive circuitry with a highcurrent triac (bidirectional triode thyristor) switch. Each device senses the applied ac line potential and automatically switches the rectifier and associated capacitors between a voltage-doubler configuration (for line voltages to 141 V) and a full-bridge configuration (for line voltages greater than 149 V). This eliminates the possibility of user error with adjustable jumpers or switches. Also, the related switch-mode power stage need operate only over a reduced range of dc input voltages when compared with "wide input" power supplies using a bridge rectifier only. The reduction in dc input voltage range permits the use of lowervoltage capacitors and leads to a reduction in power stage stresses and power dissipation. The STR83145 and STR84145 differ only in their maximum ac current rating (10 A and 12 A, respectively). The internal sensitive-gate triac is switched by a temperaturecompensated constant-current gate driver driven by a 15 kHz pulse train to reduce power dissipation. The switch-over voltage is accurately set during manufacture for consistent operation. An user-adjustable delay is provided to ensure start-up in the full-b...