Leaded and SM resistors for electronic ballasts

Available now from Stewart Electronics, part of the Compstock Group, are a number of ranges of resistors suitable for use in lighting applications.

Available now from Stewart Electronics, part of the Compstock Group, are a number of ranges of resistors suitable for use in lighting applications.

Manufactured by Welwyn Components, devices include standard metal film/oxide and wirewound resistors for noncritical circuitry, fusible resistors for circuit protection and pulse-withstand resistors designed to survive the high surges caused during tube startup.

Ballasts have an inrush current during the initial start-up several times greater than their normal operating current and in general electronic ballasts have a higher inrush current than electromagnetic or hybrid ballasts.

Inrush-current-limiting resistors are designed to withstand these surges but to fuse safely should a fault occur, for example if a capacitor were to short circuit.

Devices for this application are available in both axial-leaded and surface-mount outlines.

The WFF series of axial-leaded fast fusible metal-film resistors are flameproof and feature predictable low-power fusing characteristics.

Devices are available rated at 0.25, 0.5 and 1W, with resistance ranges of 0R1-10, 0R1-27 and 0R15-22kohm, respectively.

Each features a thermal coefficient of resistance of 250ppm/C and is rated for operation over a wide temperature range of -55 to +155C.

Another common lighting application is in power factor control.

As a general rule electronic ballasts use a large capacitor reservoir associated with a bridge rectifier.

As a result the power factor is low, and so ballasts usually incorporate either a passive or active circuit to improve the power factor.

The compact surface-mount CR series is ideal for this application, with a resistance range from 1ohm to 100Mohm and tolerances down to 0.1%.

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