Dryness sensing circuit and sensing method of dryness

Patent metadata

Field	Value
Publication number	US-2016209345-A1
Application number	US-201514735654-A
Country	US
Kind code	A1
Filing date	Jun 10, 2015
Priority date	Jan 16, 2015
Publication date	Jul 21, 2016
Grant date	—

Abstract

A dryness sensing circuit and a dryness sensing method are provided. The dryness sensing circuit and the dryness sensing method set a time constant of a resistor and capacitor short for liquidity of dryness determination algorithm and minimize a noise effect of a power supply.

First claim

What is claimed is:

1 . A dryness sensing circuit comprising:
a sensing electrode connected between first and second nodes; a non-inverting amplifier amplifying a first power supply voltage to output a first output voltage; a filter unit comprising a first filter resistor connected between the first node and a third node, a filter capacitor connected between the third node and a ground, and a second filter resistor connected between an output terminal of the non-inverting amplifier and the third node; and a voltage follower outputting a voltage of the third node as a second output voltage, wherein a dryness level of a dry target based on the second output voltage.

2 . The dryness sensing circuit of claim 1 , wherein the first and second filter resistors are variable resistors of which resistance values are varied according to the dryness level of the dry target.

3 . The dryness sensing circuit of claim 1 , wherein the non-inverting amplifier and the voltage follower are single power supply operational amplifiers.

4 . The dryness sensing circuit of claim 3 , wherein the non-inverting amplifier receives the first power supply voltage through a non-inverting terminal and comprises first and second resistors connected to an inverting terminal and having an identical resistance value.

5 . The dryness sensing circuit of claim 4 , further comprising a measurement unit measuring the second output voltage, wherein the first power supply voltage is a voltage value identical to a measurement limit value of the measurement unit

6 . The dryness sensing circuit of claim 1 , wherein the first filter resistor has a value greater than about 100 kΩ and not greater than about 1.5 MΩ,
the second filter resistor has a value greater than about 10 kΩ and not greater than about 500 kΩ, and
the filter capacitor has a value of about 0.01 μF.

7 . The dryness sensing circuit of claim 1 , further comprising a protection unit comprising a first output resistor connected between an output terminal of the voltage follower and a fourth node, and a second output resistor connected between the fourth node and the ground.

8 . The dryness sensing circuit of claim 7 , further comprising an output diode of which a cathode terminal is connected to a second power supplying terminal and an anode terminal is connected to the fourth node; and
an output capacitor connected between the fourth node and the ground.

9 . The dryness sensing circuit of claim 8 , wherein a second power supply voltage from the second power supply terminal is identical to the first power supply voltage.

10 . The dryness sensing circuit of claim 1 , further comprising a static electricity protection unit comprising a first capacitor and a first diac connected together in parallel and connected between the first node and the ground, and a second capacitor and a second diac connected to each other in parallel and connected between the ground and earth ground.

11 . The dryness sensing circuit of claim 1 , further comprising a voltage limiting unit comprising a first diode of which a cathode terminal is connected to an output terminal of the non-inverting amplifier and an anode terminal is connected to the third node, and a second diode of which a cathode terminal is connected to the third node and an anode terminal is connected to the ground.

Assignees

• Lg Electronics Inc

Inventors

• Lee Hoonbong
• Kim Junghun

Classifications

• D06F2103/08

  Humidity · CPC title

• D06F58/38

  of drying, e.g. to achieve the target humidity · CPC title

• G01N27/048 Primary

  for determining moisture content of the material · CPC title

• G01N27/045

  Circuits (measuring resistance per se G01R27/00, e.g. G01R27/22) · CPC title

• D06F34/18

  Condition of the laundry, e.g. nature or weight · CPC title