Drive circuit

• US 7,944,116 B2
• Filed: 12/11/2006
• Issued: 05/17/2011
• Est. Priority Date: 01/17/2006
• Status: Expired due to Fees

• Current Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Original Assignee: Dyson Technology Limited (Beeswax Holdings UK Limited)
• Inventors: Causier, Stephen James
• Primary Examiner(s): ROSENAU, DEREK JOHN
• Application Number:
  US12/160,969
• Publication Number:
  US 20100236092A1
• Time in Patent Office: 1,618 Days
• Field of Search: 310/317, 310/318, 310/314
• US Class Current: 310/317
• 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 hand dryer, comprising:

a nebulizer,

the nebulizer comprising a drive circuit for a high-frequency agitation source, the drive circuit comprising;

a signal generating stage generating a train of low voltage square-wave pulses at a drive frequency,

a boost stage including a boost inductor for generating a back EMF, the boost stage being configured to produce a high-voltage pulse train in response to the low-voltage square-wave pulse train, and

a filter stage producing from the high-voltage pulse train 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. The drive circuit of claim 1, wherein the high-frequency agitation source is a piezoelectric crystal.

3. The drive circuit of claim 1, wherein the filter stage comprises a low-pass filter.

4. The drive circuit of claim 3, wherein the filter stage comprises an inductor in series with the high-frequency agitation source and a capacitor in parallel with the high-frequency agitation source.

5. The drive circuit of claim 1, further comprising a DC power source and a power rail supplied by the DC power source.

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

7. The drive circuit of claim 5, wherein the boost stage further comprises a switch that switches the power rail on or off in response to the train of low-voltage square-wave pulses.

8. The drive circuit of claim 1, wherein the drive signal frequency produced by the drive circuit is in the region of 1.5-2 MHz.

9. The drive circuit of claim 1, wherein the boost inductor generates a back EMF greater than 50 V.