Current-supply control unit, fusing device, image forming apparatus, and current-supply control method

1. A current-supply control unit for controlling current supply to a heating element, comprising:

a voltage detector to detect voltage at both ends of the heating element;

a heating element control unit to control a duty cycle of current supply for the heating element based on the voltages detected by the voltage detector when current is supplied to the heating element; and

a plurality of heating elements connected in parallel and a plurality of heating element control units, each of the plurality of heating element control units connected serially to a corresponding one of the heating elements,

wherein, when the plurality of heating elements is started to be supplied with current simultaneously, the voltage detector conducts voltage detection at a stage after the heating element control unit connected in series to the heating element having the greatest activation current among the plurality of heating elements.

2. The current-supply control unit of claim 1 , wherein the voltage detector is disposed between the heating element control unit and the heating element.

3. The current-supply control unit of claim 1 , further comprising a main controller to output a control signal to the heating element control unit,

wherein the main controller outputs a heating element ON signal to the heating element control unit to start current supply to the heating element without setting a duty limit of current,

wherein the heating element control unit supplies current to the heating element without setting the duty limit of current based on the heating element ON signal output from the main controller,

wherein the voltage detector detects alternating current (AC) voltage at both ends of the heating element supplied with current and converts the AC voltage to direct current (DC) voltage,

wherein the main controller determines a value of the AC voltage based on the converted DC voltage converted by the voltage detector and sets an upper limit of duty cycle of current to be supplied to the heating element based on the determined AC voltage,

wherein the main controller outputs a heating element ON signal to the heating element control unit to supply current having the set upper limit of duty cycle to the heating element,

wherein the heating element control unit controls current-supply to the heating element based on the set upper limit of duty cycle of current.

4. The current-supply control unit of claim 3 , wherein the current having the set upper limit of duty cycle is repeatedly supplied to the heating element until a temperature of the heating element reaches a target temperature.

5. A fusing device, comprising:

the current-supply control unit of claim 1 ; and

a heating element supplied with current using the current-supply control unit.

6. An image forming apparatus, comprising:

the fusing device of claim 5 ; and

an image forming unit to form an image on a recording sheet using the fusing device.

7. A method of controlling current supply to a heating element, comprising:

detecting voltage at both ends of the heating element using a voltage detector;

controlling a duty cycle of current supplied to the heating element based on the voltages detected at both ends of the heating element in the detecting step when current is supplied to the heating element; and

connecting a plurality of heating elements in parallel to a plurality of heating element control units, each of the plurality of heating element control units connected serially to a corresponding one of the heating elements,

wherein, when the plurality of heating elements is started to be supplied with current simultaneously, the voltage detector conducts voltage detection at a stage after the heating element control unit connected in series to the heating element having the greatest activation current among the plurality of heating elements.

8. A non-transitory computer readable carrier medium storing a program for executing a method of controlling current supply to a heating element, which when executed causes a computer to perform the method of controlling current supply to the heating element, the method comprising the steps of claim 7 .

9. A current-supply control unit for controlling current supply to a heating element, comprising:

a voltage detector to detect voltage at both ends of the heating element;

a heating element control unit to control a duty cycle of current supply for the heating element based on the voltages detected by the voltage detector when current is supplied to the heating element; and

a plurality of heating elements connected in parallel and a plurality of heating element control units, each of the plurality of heating element control units connected serially to a corresponding one of the heating elements,

wherein, when the plurality of heating elements is started to be supplied with current non-simultaneously, the voltage detector conducts voltage detection at a stage after the heating element control unit connected in series to the heating element activated earliest among the plurality of heating elements.

10. The current-supply control unit of claim 9 , wherein the voltage detector is disposed between the heating element control unit and the heating element.

11. The current-supply control unit of claim 9 , further comprising a main controller to output a control signal to the heating element control unit,

wherein the main controller outputs a heating element ON signal to the heating element control unit to start current supply to the heating element without setting a duty limit of current,

wherein the heating element control unit supplies current to the heating element without setting the duty limit of current based on the heating element ON signal output from the main controller,

wherein the voltage detector detects alternating current (AC) voltage at both ends of the heating element supplied with current and converts the AC voltage to direct current (DC) voltage,

wherein the main controller determines a value of the AC voltage based on the converted DC voltage converted by the voltage detector and sets an upper limit of duty cycle of current to be supplied to the heating element based on the determined AC voltage,

wherein the main controller outputs a heating element ON signal to the heating element control unit to supply current having the set upper limit of duty cycle to the heating element,

wherein the heating element control unit controls current-supply to the heating element based on the set upper limit of duty cycle of current.

12. The current-supply control unit of claim 11 , wherein the current having the set upper limit of duty cycle is repeatedly supplied to the heating element until a temperature of the heating element reaches a target temperature.

13. A fusing device, comprising:

the current-supply control unit of claim 9 ; and

a heating element supplied with current using the current-supply control unit.

14. An image forming apparatus, comprising:

the fusing device of claim 13 ; and

an image forming unit to form an image on a recording sheet using the fusing device.