Now available from RF and microwave component specialist Link Microtek is a range of high-speed PIN diodes that are made from high-resistively epitaxial silicon material, passivated with silicon dioxide to achieve high levels of stability and reliability.
Capable of operating with as little as +10mA forward bias, the devices are ideal for RF switching applications in telecommunications, radar and ECM systems, and they can also be used as current-controlled resistors in attenuator-type applications over the frequency range from UHF to Ku band.
Available from www.usbid.com - Diode Silicon Epitaxial Planar Type - 015AZ2.0~015AZ12 is designed for Constant Voltage Regulation Applications. Toshiba Diode Silicon Epitaxial Planar Type 015 AZ 2.0 • 015AZ2.0-X. Flash memory may be ordered from USBid catalog page http://www.usbid.com/search/AddPartNoLogin_action.cfm
PFC diodes are needed
Choosing a suitable diode is the easiest and most cost-effective way of reducing both the peak power and the average switching losses in the MOSFET.
Conventional ultra fast epitaxial diodes are optimized for low forward voltage as well as short recovery time. Diodes for use in power factor correction circuits have higher forward voltage but much shorter reverse recovery times in order to reduce the transistor losses
Active power factor correction has a number of advantages, which result from removing the effect of power line voltage variations:
• Greater efficiency and better line voltage regulation in the downstream switched mode converter stages.
• Use of a smaller reservoir capacitor for a given hold-up time, because energy storage is always at a higher voltage than the peak of the rectified mains.
• Lower peak current in the mains input rectifier diodes and lower ripple current in the reservoir capacitor
• Operation over the full international range of power line voltages (90-V - 277-V AC rms) without range switching
In contrast, ultra fast epitaxial diodes designed for power factor correction need to have much faster reverse recovery in order to reduce the MOSFET switching losses.
The reverse recovery time of a BYC5 power factor correction diode is typically 15 ns at 500 A/-Mu s, 25 Celsius, and the maximum forward voltage is 2.8 V at 5 A, 25 Celsius. This represents the optimum trade-off between forward voltage and reverse recovery time in this application
Thursday, January 25, 2007
Tuesday, January 23, 2007
The Basics of Heat Sinks
The overall efficiency of various heat-sink types mainly depends on the following three factors:
• material.
• surface area,
• structure or shape
Cooling capabilities relate directly to the surface area; the larger the surface area, the more heat that can be dissipated. Physical structure is yet another factor. Proper structure increases turbulent airflow which creates a more competent heat sink.
The heat-sink material is also critical. Copper, for example, has excellent cooling qualities compared to aluminum because the thermal conductivity of copper is much higher than the conductivity of aluminum. At room temperature, copper has a thermal conductivity of exactly 401 W/m-K. Aluminum is 235 W/m-K. Therefore, a heat sink made of copper dissipates more significantly more heat than a heat sink made from aluminum.
One such example is the Pin Fin Heat Sinks 628-65ABT3
• material.
• surface area,
• structure or shape
Cooling capabilities relate directly to the surface area; the larger the surface area, the more heat that can be dissipated. Physical structure is yet another factor. Proper structure increases turbulent airflow which creates a more competent heat sink.
The heat-sink material is also critical. Copper, for example, has excellent cooling qualities compared to aluminum because the thermal conductivity of copper is much higher than the conductivity of aluminum. At room temperature, copper has a thermal conductivity of exactly 401 W/m-K. Aluminum is 235 W/m-K. Therefore, a heat sink made of copper dissipates more significantly more heat than a heat sink made from aluminum.
One such example is the Pin Fin Heat Sinks 628-65ABT3
Monday, January 22, 2007
Home appliances become more efficient with new ICs
Trends in appliance motors
Permanent magnet synchronous motors are beginning to replace split-phase induction motors in appliances as a means of boosting efficiency while reducing part costs. PM synchronous motors work at variable speeds and may become part of the appliance structure itself, perhaps eliminating the need for separate gearboxes and belt drives used to harness power from induction motors. Component IRMC xxx family through USBid
Integrated chips in PMS motors
Integrated circuits aimed at managing motors and power supplies may help boost the efficiency of
consumer goods such as air conditioners, washer/dryers, refrigerators, and video games. Special interface chips for appliances and switching power supplies that facilitate the use of advanced motors and controls can all be found through USBid. One new chip targets permanent-magnet synchronous (PMS) motors that are now being designed into major appliances. These motors are starting to be specified in place of ordinary split-phase induction motors, which have served in washer/dryers and refrigerators for decades. Besides being more energy efficient, PMS motors are smaller than comparable induction motors and less expensive as well because they use less steel. PMS motors have also begun showing up in condensing units of split-system residential air conditioners. There is also a single-rotary compressor incorporating a PMS motor that is said to be as efficient as more-expensive scroll compressors. The chipmakers are targeting motors in condensing units specifically with the development of what it calls an iMotion integrated power-design platform. It lets appliance makers control PMS motors with variable-speed sinusoidal current control. This control technique eliminates the need for Hall-effect sensors that would ordinarily be necessary to gauge rotor position. The platform, dubbed the IRMCxx family and can ordered through USBid, is billed as an IC, complete with power-factor correction. The only feedback it needs for operation comes from a dc link-current sensor. It runs embedded motor-control algorithms with an independent application layer processor that handles tasks specific to different classes of appliances. The chip can be keyed to different kinds of appliances through the use of appliance-specific high-voltage IC sections and intelligent power modules already in place.
Integrated chips used in air conditioners
For example, the air-conditioning platform incorporates a proprietary algorithm for interior PMS motors driving both the AC compressor and fan. Combined with application-specific HVICs and discrete trench IGBTs to handle the output power, the controller is said to hit 95% converter efficiency. In this regard it works with individual PMS motor manufacturers to tune converter parameters for best efficiency. Digital controls on the chips consist of a Motion Control Engine (MCE) that implements the sensorless algorithm in hardware, plus an embedded analog signal engine that handles all signal-conditioning and conversion circuits for single-current shunt sensorless control. The MCE executes the sensorless field-oriented control algorithm in about 11 _sec. This speedy execution is key to handling fan and compressor motors simultaneously. An application layer processor on the chip defines the operation of the air-conditioning system independently from the MCE that controls the fan and compressor motors. The intent of this separate processor is to let appliance makers focus on application issues rather than on motor control. Appliance makers may locate the PMS chips (IRMC) through Get Parts Fast a USBid, Inc. sourcing site.
Trends in appliance motors
Permanent magnet synchronous motors are beginning to replace split-phase induction motors in appliances as a means of boosting efficiency while reducing part costs. PM synchronous motors work at variable speeds and may become part of the appliance structure itself, perhaps eliminating the need for separate gearboxes and belt drives used to harness power from induction motors. Component IRMC xxx family through USBid
Integrated chips in PMS motors
Integrated circuits aimed at managing motors and power supplies may help boost the efficiency of
consumer goods such as air conditioners, washer/dryers, refrigerators, and video games. Special interface chips for appliances and switching power supplies that facilitate the use of advanced motors and controls can all be found through USBid. One new chip targets permanent-magnet synchronous (PMS) motors that are now being designed into major appliances. These motors are starting to be specified in place of ordinary split-phase induction motors, which have served in washer/dryers and refrigerators for decades. Besides being more energy efficient, PMS motors are smaller than comparable induction motors and less expensive as well because they use less steel. PMS motors have also begun showing up in condensing units of split-system residential air conditioners. There is also a single-rotary compressor incorporating a PMS motor that is said to be as efficient as more-expensive scroll compressors. The chipmakers are targeting motors in condensing units specifically with the development of what it calls an iMotion integrated power-design platform. It lets appliance makers control PMS motors with variable-speed sinusoidal current control. This control technique eliminates the need for Hall-effect sensors that would ordinarily be necessary to gauge rotor position. The platform, dubbed the IRMCxx family and can ordered through USBid, is billed as an IC, complete with power-factor correction. The only feedback it needs for operation comes from a dc link-current sensor. It runs embedded motor-control algorithms with an independent application layer processor that handles tasks specific to different classes of appliances. The chip can be keyed to different kinds of appliances through the use of appliance-specific high-voltage IC sections and intelligent power modules already in place.
Integrated chips used in air conditioners
For example, the air-conditioning platform incorporates a proprietary algorithm for interior PMS motors driving both the AC compressor and fan. Combined with application-specific HVICs and discrete trench IGBTs to handle the output power, the controller is said to hit 95% converter efficiency. In this regard it works with individual PMS motor manufacturers to tune converter parameters for best efficiency. Digital controls on the chips consist of a Motion Control Engine (MCE) that implements the sensorless algorithm in hardware, plus an embedded analog signal engine that handles all signal-conditioning and conversion circuits for single-current shunt sensorless control. The MCE executes the sensorless field-oriented control algorithm in about 11 _sec. This speedy execution is key to handling fan and compressor motors simultaneously. An application layer processor on the chip defines the operation of the air-conditioning system independently from the MCE that controls the fan and compressor motors. The intent of this separate processor is to let appliance makers focus on application issues rather than on motor control. Appliance makers may locate the PMS chips (IRMC) through Get Parts Fast a USBid, Inc. sourcing site.
Wednesday, January 10, 2007
Where Does One Find Digital ICs
If you have ever tried to find the first generation of digital ics you know what a night mare that can be. Luckily there are sites like Buy Parts Fast and Locate IC out there. Just make sure you know your part number like S1680160 and you are set
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