ICs, modules, and board subassemblies designed specifically for power supply applications simplify the power supply engineer's task and reduce time to market. By combining functions at either the chip or package level, semiconductor manufacturers can include additional features. Surface mount technology is essential for integrated circuits but has expanded to other components including transformers. This section discusses a variety of hardware choices from suppliers to help engineers design power supplies.
SURFACE MOUNT TRANSFORMERS
Frontier Electronics surface mount CCFL inverter transformers address PDA, laptop, dash board, monitor, digital camera, and display applications. The low profile and high power units handle output voltages from 750 to 1600V ac at operating frequencies from 40 to 200 kHz and power ratings from 1.2 to 6W. With efficiency ratings from 78 to 80 percent, the design uses a special segmented flanged bobbin to avoid voltage flash over. Sizes are available from 12.3ื10.8ื3.0 mm to 25.2ื15.2ื8.5 mm. For more information on Frontier Electronics', surface mount transformers, go tohttp://rbi.ims.ca/4416-674.
THREE-PHASE IGBT GATE DRIVER BOARD
Applied Power Systems AP1491 Gate Driver is a fully integrated IGBT driver for three-phase bridge or full bridge circuit applications. The units include dc link voltage sensing, diagnostic LEDs, overvoltage protection, current sensing, and heatsink temperature sensing capability. Designed to provide industrial OEMs the capability of developing high power industrial IGBT inverters, the gate driver controls up to six IGBTs at currents in excess of 1200A. The reliable, field-proven approach incorporates the isolated power supplies and protection features required for safe operation of IGBT power stages. Units include undervoltage lock-out, automatic dead time generation, and shoot through protection. A single 26-pin header handles all I/O and input power. For maximum safety, the unit isolates analog feedback of all critical power stage parameters including the dc bus voltage, output phase current, and device temperature. For more information on Applied Power Systems' AP-1491 IGBT Gate Drive Boards, go tohttp://rbi.ims.ca/4416-675(driver circuits, AP1491).
POWER MANAGEMENT ICS
Microchip Technology Inc.'s TC1303/TC1304 and TC1313 power management ICs combine a synchronous buck switching regulator, low dropout regulator (LDO), and power-good function into a single-chip solution. The synchronous buck dc-dc converter has a pulse width modulation (PWM) oscillator that operates at a fixed frequency of 2.0 MHz when the load is heavy. With a light current in the stand-by mode, the regulator's low-current operating mode uses pulse frequency modulation (PFM). The dc-dc regulator has adjustable and fixed-output voltage modes to meet the design requirements of the end application. The LDO regulator has a typical dropout voltage of 137 mV at a 200 mA load allowing it to operate with minimum differential voltage. A single 1.0 ตF ceramic capacitor stabilizes the output. The power-good function provides a signal when the power is within specific limits. For more information on Microchip's new power management ICs, go tohttp://rbi.ims.ca/4416-676.
PFC SMART POWER MODULE
Fairchild Semiconductor's SPM FSAB20PH60 PFC Smart Power Module (SPM) implements Partial Power Factor Correction Switching Converter (PSC) circuit methodology for high efficiency. By triggering the IGBTs in the module at every line current half cycle, the unit provides 97percent of power factor (typical) and complies with the IEC61000-3-2 standard. The approach provides improved electromagnetic interference (EMI) characteristics compared to higher frequency switching topologies. The module's design combines four rectifier diodes, two IGBTs, a gate-driver IC, and a thermistor in a single package. Direct Bonded Copper (DBC) substrate packaging technology provides an isolation voltage rating of 2500 VRMS and a thermal resistances of Rqjc(IGBT) equal to 2.8C/W for the IGBTs and Rqjc(DIODE) of 2.6C/W for the diodes. The compact design measures only 44ื26.8 mm. The units specifically target 1 to3 kW air conditioners but also address other consumer appliance applications from 50W to 3 kW. For more information on Fairchild Semiconductor's Smart Power Module, go tohttp://rbi.ims.ca/4416-677.
HIGH-FREQUENCY BUCK REGULATOR
National Semiconductor Corp's LM5005 is a high- frequency buck regulator that steps down an input voltage of 7 to 75V to provide a regulated 2.5A power supply, adjustable from 1.225 to 65V. The high-voltage switching regulator has an integrated 75-V N-channel MOSFET and current-mode pulse-width modulation (PWM) to produce a 2.5A output current. The control method reduces the controller's noise sensitivity through an internal emulated inductor current ramp. This allows designers to take full advantage of the unit's 75-V input and 500 kHz frequency capabilities and control very small duty cycles. The integrated features include current limit, thermal shutdown and remote shutdown capability, which provide a smaller overall footprint for implementing a step-down switching regulator with minimal external components. The LM5005 operates over a programmable frequency range from 50 to 500 kHz and targets 48V telecom, automotive, and industrial power supply applications. For more information on National Semiconductor's LM5005, go tohttp://rbi.ims.ca/4416-679.
Transera Electronics' epoxy-encapsulated transformers provide improved shock/vibration and humidity/moisture resistance, enhanced mechanical strength, and better insulation reliability for mechanical and insulation advantages over non-encapsulated transformers. The use of epoxy instead of tape or paper insulation provides reduced winding temperature differential so the transformers may be used in higher ambient temperature environments. Highly automated winding, laminating, and encapsulation processes reduce the cost and provide consistent quality for these units. Available in ratings from 0.08 to 150 VA, the transformers come in low profile, print-line, and mini-line formats for flexible installation and optimal space utilization. The transformers target a variety of applications such as HVAC systems, metering, medical, and circuit boards, among others. For more information on Transera's encapsulated transformers, go tohttp://rbi.ims.ca/4416-678.