Magnetic coil driving circuit for magnetic contactor

Patent metadata

Field	Value
Publication number	US-2017222428-A1
Application number	US-201715412002-A
Country	US
Kind code	A1
Filing date	Jan 21, 2017
Priority date	Feb 2, 2016
Publication date	Aug 3, 2017
Grant date	—

Abstract

The magnetic coil driving circuit of the magnetic contactor according to the present invention comprises a semiconductor switch configured to open or close a circuit for magnetizing or demagnetizing a magnetic coil; a pulse width modulation unit configured to output a pulse signal as a control signal for turning on or off the semiconductor switch; a control unit configured to output a control signal for changing a pulse width of the pulse signal to the pulse width modulation unit; and a temperature detection and protection unit configured to detect a temperature inside the magnetic contactor, output an output signal for turning off the semiconductor switch when the temperature exceeds an allowable temperature, and control the semiconductor switch by the pulse signal from the pulse width modulation unit when the temperature is within the allowable temperature.

First claim

What is claimed is:

1 . A magnetic coil driving circuit for magnetic contactor, the magnetic coil driving circuit comprising:
a semiconductor switch connected in series to a magnetic coil and configured to magnetize the magnetic coil upon turning on and demagnetize the magnetic coil upon turning off; a pulse width modulation unit connected to the semiconductor switch and configured to output a pulse signal to the semiconductor switch as a control signal for turning on or off the semiconductor switch; a control unit connected to the pulse width modulation unit and configured to output a control signal for changing a pulse width of the pulse signal in order to perform control to increase the amount of electric current flowing through the magnetic coil when the magnetic coil is initially magnetized and perform control to decrease the amount of electric current flowing through the magnetic coil when the magnetization of the magnetic coil is maintained; and a temperature detection and protection unit connected to the semiconductor switch and configured to detect a temperature inside the magnetic contactor, output an output signal for turning off the semiconductor switch in a high-temperature state when the temperature exceeds an allowable temperature, and to make the semiconductor switch be controlled by the pulse signal from the pulse width modulation unit in a normal state when the temperature is within the allowable temperature.

2 . The magnetic coil driving circuit of claim 1 , wherein the temperature detection and protection unit comprises at least one thermal variable resistor having a resistance value that varies with a change in temperature.

3 . The magnetic coil driving circuit of claim 1 , wherein the temperature detection and protection unit comprises:
at least one thermal variable resistor having a resistance value that varies with a change in temperature; and at least one variable resistor connected in parallel with the thermal variable resistor.

4 . The magnetic coil driving circuit of claim 1 , wherein the temperature detection and protection unit comprises:
a temperature detection unit configured to output a first voltage that varies with a change in temperature inside the magnetic contactor; and a comparator configured to compare the first voltage which is output from the temperature detection unit and a second voltage which is a predetermined reference voltage.

5 . The magnetic coil driving circuit of claim 1 , wherein the temperature detection and protection unit comprises:
a temperature detection unit configured to output a first voltage that varies with a change in temperature inside the magnetic contactor; a first comparator configured to compare the first voltage, which is output from the temperature detection unit, and a second voltage, which is a predetermined reference voltage; and a second comparator having a first input terminal connected to an output terminal of the first comparator and a second input terminal connected to an output terminal of the pulse width modulation unit, the second comparator being configured to compare an input signal from the first input terminal and an input signal from the second input terminal and output a switching control signal for controlling a switching of the semiconductor switch.

6 . The magnetic coil driving circuit of claim 4 , wherein, when the temperature inside the magnetic contactor exceeds the allowable temperature and a temperature state is in a high-temperature state, the comparator is configured to output a digital signal having a logical value 0.

7 . The magnetic coil driving circuit of claim 5 , wherein:
the second comparator is configured with an AND gate; and when the temperature inside the magnetic contactor exceeds the allowable temperature and a temperature state is in a high-temperature state, the first comparator is configured to output a digital signal having a logical value 0.

8 . The magnetic coil driving circuit of claim 5 , wherein:
the second comparator is configured with an AND gate; when the temperature inside the magnetic contactor is within the allowable temperature and a temperature state is in a normal state, the first comparator is configured to output a digital signal having a logical value 1; and the semiconductor switch is turned on or off depending on the pulse signal from the pulse width modulation unit.

9 . The magnetic coil driving circuit of claim 5 , wherein:
the second comparator is configured with an AND gate; when the temperature inside the magnetic contactor exceeds the allowable temperature and a temperature state is in a high-temperature state, the first comparator is configured to output a digital signal having a logical value 0; and the semiconductor switch is turned off independently of the pulse signal from the pulse width modulation unit.

10 . The magnetic coil driving circuit of claim 1 , further comprising a voltage detection unit configured to detect a voltage of an AC power source supplied to the magnetic contactor,
wherein the control unit is configured to compare the voltage of the AC power source detected by the voltage detection unit with a reference voltage and output a control signal for opening the magnetic contactor to the pulse width modulation unit when the voltage of the AC power source exceeds the reference voltage.

Assignees

• Lsis Co Ltd

Inventors

• Choi Jaehyuk

Classifications

• H01H2047/025

  with taking into account of the thermal influences, e.g. change in resistivity of the coil or being adapted to high temperatures · CPC title

• H02H7/222 Primary

  for switches · CPC title

• F02D2041/2065

  the control being related to the coil temperature · CPC title

• H01H47/002 Primary

  Monitoring or fail-safe circuits · CPC title

• H01F2007/1888

  using pulse width modulation · CPC title