Drive Circuit

• US 20100236092A1
• Filed: 12/11/2006
• Published: 09/23/2010
• Est. Priority Date: 01/17/2006
• Status: Active Grant

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Causier, Stephen James
• Granted Patent: US 7,944,116 B2
• Time in Patent Office: Days
• US Class Current: 34/572
• CPC Class Codes: B05B 17/0607 generated by electrical means, e.g. piezoelectric transducers
• CPC Class Codes: B06B 1/023 and stepped in amplitude, e.g. square wave, 2-level signal
• CPC Class Codes: H02M 7/537 using semiconductor devices only, e.g. single switched pulse inverters
• CPC Class Codes: H10N 30/802 Drive or control circuitry or methods for piezoelectric or electrostrictive devices not otherwise provided for

Abstract

A drive circuit for a high-frequency agitation source includes a signal generator generating a train of low voltage square-wave pulses at a drive frequency, a booster including a boost inductor generating a back EMF and configured to produce a high-voltage pulse train in response to the low-voltage square-wave pulse train and a filter producing a drive signal having a pre-determined harmonic of the drive frequency, the drive signal being used to drive the high-frequency agitation source. The drive circuit is particularly suitable for use with piezoelectric crystals.

Claims

1. A drive circuit for a high-frequency agitation source, the drive circuit comprising signal generating means for generating a train of low voltage square-wave pulses at a drive frequency, boost means including a boost inductor for generating a back EMF, the boost means being arranged to produce a high-voltage pulse train in response to the low-voltage square-wave pulse train and filter means for producing a drive signal having a pre-determined harmonic of the drive frequency, the drive signal being used to drive the high-frequency agitation source.

2. A drive circuit according to claim 1, wherein the high-frequency agitation source is a piezoelectric crystal.

3. A drive circuit according to claim 1 or 2, wherein the filter means comprises a low-pass filter.

4. A drive circuit according to claim 3, wherein the filter means comprises an inductor in series with the high-frequency agitation source and a capacitor in parallel with the high-frequency agitation source.

5. A drive circuit according to any one of the preceding claims, further including a DC power source and a power rail supplied by the DC power source.

6. A drive circuit according to claim 5, wherein the boost inductor is connected in parallel between the power rail of the DC power source and ground.

7. A drive circuit according to claim 5 or 6, wherein the boost means further comprises switching means for switching the power rail on or off in response to the train of low-voltage square-wave pulses.

8. A drive circuit according to any one of the preceding claims, wherein the drive frequency is in the region of 1.5-2 MHz.

9. A drive circuit according to any one of the preceding claims, wherein the boost inductor generates a back EMF greater than 50 V.

11. A nebuliser incorporating the drive circuit according to any one of the preceding claims.

12. A hand dryer incorporating the nebuliser as claimed in claim 11.

10. A drive circuit as hereinbefore described with reference to the accompanying drawings.