Controller for a High Frequency Agitation Source

• US 20090026883A1
• Filed: 02/07/2007
• Published: 01/29/2009
• Est. Priority Date: 02/08/2006
• Status: Active Grant

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Douglas, Paul Graham, Croft, Nathan James
• Granted Patent: US 7,825,564 B2
• Time in Patent Office: Days
• US Class Current: 310/315
• CPC Class Codes: B06B 1/0261 taken from a transducer or electrode connected to the driving transducer

Abstract

A controller for a high-frequency agitation source includes a signal generator to generate a drive signal having a variable duty cycle. The drive signal is used to drive the high-frequency agitation source. The controller also includes a temperature detector to detect the temperature of the high-frequency agitation source. The controller is configured to vary the duty cycle of the drive signal in response to the temperature of the high-frequency agitation source. By varying the duty cycle of the drive signal, the average power supplied to the piezoelectric crystal can be varied while still maintaining a fixed amplitude of oscillation. This allows the temperature of a high-frequency agitator, for example, a piezoelectric crystal, to be controlled.

Claims

1. A controller for a high-frequency agitation source, comprising:

a signal generator to generate a drive signal having a variable duty cycle and being used to drive the high-frequency agitation source, a temperature detector to detect a temperature of the high-frequency agitation source, wherein the controller is configured to vary the duty cycle of the drive signal in response to the temperature of the high-frequency agitation source.

2. A controller as claimed in claim 1, wherein the controller varies the duty cycle in order to prevent the temperature of the high-frequency agitator exceeding a pre-determined operating temperature.

3. A controller as claimed in claim 1 or 2, wherein the duty cycle is set to a maximum value by the controller at the start of an operation of the high-frequency agitation source.

4. A controller as claimed in claim 1 or 2, wherein the controller is further configured to control the drive signal in response to a first pre-determined requirement and to determine when the first pre-determined requirement has been satisfied.

5. A controller as claimed in claim 4, wherein the first pre-determined requirement is that the duty cycle is reduced below a pre-determined value.

6. A controller as claimed in claim 4, wherein the first pre-determined requirement is the detection that a pre-determined time period has elapsed.

7. A controller as claimed in claim 4, wherein the first pre-determined requirement is the detection of a pre-determined temperature condition.

8. A controller as claimed in claim 4, wherein the controller is configured to cause the drive signal to switch off when the first pre-determined requirement is satisfied.

9. A controller as claimed in claim 1 or 2, wherein the controller is arranged to cause the drive signal to switch off in the event that no change of temperature is observed when the high-frequency agitator is operated.

10. A controller as claimed in claim 1 or 2, wherein the controller is arranged to cause the drive signal to switch off when the temperature exceeds a pre-determined maximum value.

11. A controller as claimed in claim 1 or 2, wherein the controller determines a maximum operation time for which the drive signal shall remain on and causes the drive signal to switch off when the maximum operation time is exceeded.

12. A controller as claimed in claim 1 or 2, wherein the controller detects the temperature of the high-frequency agitator at pre-determined intervals.

13. A drive circuit comprising the controller as claimed in claim 1 or 2.

14. A drive circuit as claimed in claim 13, comprising a further temperature detector to detect the temperature of at least a part of the drive circuit, the controller being configured to vary the maximum duty cycle of the drive signal in response to the temperature of the at least a part of the drive circuit.

15. A nebuliser comprising the drive circuit as claimed in claim 13.

16. A hand dryer comprising the nebuliser as claimed in claim 15.

17. (canceled)