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SMART 3D 4WIRE ACTUATOR DRIVER Disclosure Number: IPCOM000012216D
Publication Date: 2003-Apr-17
Document File: 3 page(s) / 88K

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ID 612288

Smart 3D 4wire actuator driver

Tilt actuators for CD and DVD

For CD/DVD player/writer the light spot is being kept on track and focus by an optical lens. In order to do this on a rotating disc is the lens is constantly positioned in place using a linear motor. This linear is called an actuator.

For a conventional CD player this actuator takes care of two movements:

Focus and tracking.

With the increasing number of bytes that one optical disk must be able to store the angle between the light spot and disc becomes also important.

This movement “tilt” is there fore added to the new generation actuators.

The tilting actuator.

Different tilting actuators

The simplest way to make a tilting actuator is to add an extra coil to provide the tilt movement.

This would require a strait forward 3 H-bridges driver.

An other way to make a tilting actuator is to split-up the focus coils in two separate coils.

(The focus coil moves the lens closer or further to the disc so the light spot stay in focus on the disc.)

With a split up focus coil you have in fact two focus coils that you can steer separately.
If you tell one side of the lens to go up (focus 1) and the other side to go down (focus 2) you have established a tilt function.

It is also possible to do this trick with the radial coil.

One important conclusion is that for a tilting actuator you will always need 3 electrical coils.

Since each coil has two connection terminals a tilting actuator would have basically 6 connection terminals.

For mechanical reasons it would be preferable to have only 4 connection terminals.

By connecting the 3 terminals the number of connection is reduced from 6 to 4 wires.

See drawing.

� � � � � � � �

Figure 1 Reducing from 6 wire to 4 wire.

Applying tilt

If just look at the focus function and connect the two separate focus coils toge...