Power Electronics

Smart Drivers Simplify and Optimize Motor Control

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Consumer appliance and industrial applications are generating demand for sophisticated motor control circuits that can simplify system designs, reduce space requirements for control circuitry and ensure high levels of efficiency and robust fault protection. Semiconductor manufacturers have responded by developing motor driver and motor control components in the form of monolithic ICs as well as compact multichip modules.

Some of the new components reflect trends in the appliance marketplace away from single-phase ac induction motors going to high-voltage brushless dc (BLDC) motors. The latter offer higher levels of efficiency (from 50% to 90%), less acoustic noise and vibration, and higher power density. The latest ICs and modules also reflect the trend toward variable-speed motor control designs.

Among the recently developed components is a family of monolithic smart motor drivers from STMicroelectronics (see the table). These drivers are members of the powerSPIN platform (www.st.com/powerspin), which provides a basis for scalable motion control designs. The device family includes eight drivers aimed at dual dc or bipolar stepper motors (part numbers L6205 , L6225, L6206, L6226, L6207, L6227, L6208 and L6228) and two drivers targeting BLDC motors (L6235 and L6229). Besides the chips, the platform supports product development with evaluation boards, PC software and application notes.

The powerSPIN devices are fabricated in BCDIII, ST's robust 60-V mixed-signal process that combines bipolar, CMOS and isolated DMOS structures. This process allows all of the control and power circuitry required to drive the motor to be integrated on a single die. For example, the L6208 integrates all the circuitry required to drive a two-phase stepper motor, including a dual DMOS full bridge, a constant off-time PWM current controller that performs chopping regulation, and a phase-sequence generator.

Similarly, for driving three-phase brushless dc motors, the L6235 integrates a three-phase DMOS bridge, a constant off-time PWM current controller and decoding logic for single-ended Hall sensors. Both chips feature nondissipative overcurrent protection on the high-side power MOSFETs and thermal shutdown. The L620x devices and the L6235 are rated at 5.6 A pk (2.8 ARMS), while the L622x devices are rated at 2.8 A pk, 1.4 ARMS. Devices also can be easily connected in parallel to double these ratings and are designed for an 8-V to 52-V operating voltage range.

Fairchild Semiconductor (www.fairchildsemi.com) recently introduced the Motion-Smart Power Modules (SPMs) designed for low-power (below 100 W), BLDC motor applications such as those in home appliances. The Motion-SPM multichip modules combine six fast-recovery MOSFETs (FRFETs) and three half-bridge, high-voltage ICs (HVIC) in a 29-mm × 120-mm Tiny-DIP, small enough for the control circuit to fit into the motor.

The Motion-SPMs' FRFETs optimize system efficiency by lowering switching and conduction losses during low-current conditions. For ruggedness, they provide a wider reverse bias safe operating area than IGBTs of similar ratings. By using the MOSFETs' body diodes as freewheeling diodes, Motion-SPMs eliminate the need for additional components, improving efficiency and noise immunity. The gate-driver ICs increase reliability through a high-isolation, 5-V CMOS/TTL interface and UVLO protection features. Additional features include high-speed level-shifting function that permits operation from a single power supply voltage, a technique that eliminates the need for opto-isolation. The 500-V, 2-A FSB50250 and the 500-V, 3-A FSB50450 are priced each at $7.20 and $8.26, respectively, in quantities of 100.

From Zetex Semiconductors (www.zetex.com), the ZXBM1015 is a single-phase motor predriver for variable- or fixed-speed control of single-phase BLDC fans, blowers and pumps. The ZXBM1015 includes a current monitor that enables supply current on startups and stall to be kept permanently within OEM specifications.

The ZXBM1015 produces a PWM output to drive an external H-bridge that, in turn, drives the motor windings. Its integral current monitoring circuit measures the voltage across a low-value external resistor in the low side of the H-bridge and deduces how much current the motor is taking during each PWM cycle. If it takes too much, the pre-driver backs off the PWM drive to reduce the current drawn.

The pre-driver IC also offers a configurable phase commutation delay, allowing OEMs to accurately meet the requirements of different motor sizes. In addition, the device is compatible with thermistor, voltage and PWM control inputs and is compatible with any type of Hall-effect sensor. The 1000-piece price of the ZXBM1015 is $0.88 each.

International Rectifier (IR; ww.irf.com) has expanded its iMOTION integrated design platform with several new products. One is the IR3103 motor drive IC, a half-bridge FredFET with gate-driver IC. Packaged in an 11-pin mini-SIP, this device can drive applications up to 180 W without a heatsink. The IR3103 simplifies the design of compact, two- and three-phase half-bridge inverter motor drives for appliances such as fans and refrigerator compressors.

Propagation delays for the high-side and low-side power FredFET devices are matched for better synchronization of switching characteristics and lower power dissipation. In addition, the device can operate up to a maximum input of 500 V at temperatures up to 150°C. Also featured is a bootstrap diode for the high-side driver section. The IR3103 is priced at $1.25 each in quantities of 10,000.

Meanwhile, IR also has released a series of high-voltage IGBT control ICs with a sophisticated set of protection functions. The series consists of 1200-V and 600-V gate-driver ICs and current-sense interface ICs for a variety of applications, including inverterized motor drives, general-purpose inverter circuits, switched-mode power supplies and UPSs.

Although IR has previously introduced current-sensing ICs with 600-V ratings, the new parts are the first rated as high as 1200 V. Similarly, the company previously offered “dumb” 1200-V rated gate drivers. However, the new 1200-V gate drivers integrate safety features that previously required external glue logic or programming of the host system's DSP. These gate drivers protect against ground faults and other overcurrent conditions, such as shoot-through and shorts to supply rails.

For appliance motor drives and a wide range of general-purpose inverter circuits, the 1200-V HVICs also are available in 600-V versions. For more on these components, including pricing, see “HVICs for Motion Control Take on Higher Voltages and Safety Features” at http://powerelectronics.com/news/hvic-motion-control. The theory behind the operation and application of these parts also is discussed in “ICs Protect IGBTs and Sense Currents in Motor Drives,” Power Electronics Technology, April 2005, pp. 34-39.

Table. Recently developed driver ICs and modules.
Vendor Model Applications Features Package
Fairchild Semi-conductor FSB50250 and FSB50450 Motion-Smart Power Modules BLDC motors in home appliances (below 100 W) Modules combine six fast- recovery MOSFETs and three half-bridge, high-voltage ICs 29 mm × 12 mm, 23-lead Tiny-DIP
International Rectifier IR3103 motor drive IC Two- and three-phase half-bridge inverter motor drives for ac induction and BLDC motors • Half-bridge FredFET with gate driver
• Needs no heatsink for motor drives up to 180 W
11-pin mini SIP
International Rectifier IR22381Q /2277S/22771S/
2214SS/22141SS
1200-V gate driver ICs and current-sensing ICs
(IR21381Q /2177S/21771S/
2114SS/21141SS are 600-V versions of these devices)
• AC induction motor drives up to 15 hp
• BLDC and ac motor drives
• 400-V ac 3-phase systems
• 1200-V IGBT gate driver ICs protect against ground faults, shoot-through, and short to supply rails
• 1200-V rating on current-sensing ICs
64-lead MQFP,16-lead SOIC, and 24-lead SSOP
STMicro-electronics L6205/6225/6206/
6226/6207/ 6227/
6208/6228/ 6235/6229 smart motor drivers
Dual dc or bipolar stepper motors and BLDC motors Two-phase stepper motor driver has:
• Dual DMOS full bridge
• PWM controller
• Phase sequence generator
PowerDIP24, PowerSO36 and SO24
Zetex Semi-conductors ZXBM1015 single-phase motor predriver Variable or fixed speed control of single-phase brushless dc fans, blowers and pumps • PWM output to drive H-bridge
• Current monitoring
• Configurable phase commutation delay
Miniature TSSOP20

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