Dryness sensing circuit and sensing method of dryness

Patent metadata

Field	Value
Publication number	US-9897562-B2
Application number	US-201514735654-A
Country	US
Kind code	B2
Filing date	Jun 10, 2015
Priority date	Jan 16, 2015
Publication date	Feb 20, 2018
Grant date	Feb 20, 2018

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 first sensing electrode connected to a first node;
a second sensing electrode connected to a second node;
a non-inverting amplifier that includes an inverting terminal, a non-inverting terminal to supply a first power supply voltage, and an output terminal to output a first output voltage;
a filter device 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 the output terminal and the third node;
a voltage follower to provide a second output voltage based on a voltage at the third node; and
a voltage limiter comprising a first diode and a second diode, the first diode having a cathode terminal connected to the output terminal of the non-inverting amplifier and an anode terminal connected to the third node, and the second diode having a cathode terminal connected to the third node and an anode terminal connected to the ground,
wherein a dryness level of a dry target is to be determined based at least on the second output voltage, and
wherein the voltage at the third node is lower than a sum voltage of the first output voltage and a threshold voltage of the first diode.

2. 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.

3. 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.

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

5. The dryness sensing circuit of claim 4 , wherein the non-inverting amplifier includes first and second resistors connected to the inverting terminal and having an identical resistance value.

6. The dryness sensing circuit of claim 5 , further comprising a measurement unit for 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.

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 having a cathode terminal connected to a second power supplying terminal and an anode terminal 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. A dryness sensing circuit comprising:
a first sensing electrode connected to a first node;
a second sensing electrode connected to a second node;
a non-inverting amplifier that includes an inverting terminal, a non-inverting terminal to supply a first power supply voltage, and an output terminal to output a first output voltage;
a first filter device and a second filter device, wherein the first filter device includes a first filter resistor connected between the first node and a third node, a first auxiliary resistor connected between the first filter resistor and the third node, a first relay unit connected to both ends of the first auxiliary resistor, a filter capacitor connected between the third node and a ground, and the second filter device includes a second filter resistor connected between the output terminal and the third node, a second auxiliary resistor connected between the second filter resistor and the third node, and a second relay unit connected to both ends of the second auxiliary resistor;
a voltage follower to provide a second output voltage based on a voltage at the third node; and
a voltage limiter that includes a first diode and a second diode, the first diode having a cathode terminal connected to the output terminal of the non-inverting amplifier and an anode terminal connected to the third node, and the second diode having a cathode terminal connected to the third node and an anode terminal connected to the ground,
wherein a dryness level of a dry target is to be determined based at least on the second output voltage, and
wherein the voltage at the third node is lower than a sum voltage of the first output voltage and a threshold voltage of the first diode.

11. The dryness sensing circuit of claim 10 , wherein a resistance value of the first filter device is to vary based on whether the first relay unit is turned on, and a resistance value of the second filter device is to vary based on whether the second relay unit is turned on.

12. The dryness sensing circuit of claim 10 , wherein a resistance value of the first filter device is a sum resistance value of the first filter resistor and the first auxiliary resistor when the first relay unit is turned on, and is a resistance value of the first filter resistor when the first relay unit is turned off.

13. The dryness sensing circuit of claim 10 , wherein a resistance value of the second filter device is a sum resistance value of the second filter resistor and the second auxiliary resistor when the second relay unit is turned on, and is a resistance value of the second filter resistor when the second relay unit is turned off.

14. The dryness sensing circuit of claim 10 , further comprising a measurement unit for 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, and
wherein the measurement unit to control switching operation for each of the first and second relay units.

Assignees

• Lg Electronics Inc

Inventors

• Lee Hoonbong
• Kim Junghun

Classifications

• D06F58/38

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

• D06F2103/08

  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

• D06F2058/2819

  Textiles & Paper · mapped topic