Scanning apparatus having a fluorescent lamp and control method thereof
A scanning apparatus having a cold cathode fluorescent lamp includes a central processing unit (CPU) controlling a scan unit to be in one of the stand-by mode, a scan mode and a sleep mode and outputting a PWM signal having a variable duty ratio based on an operation mode of the scan unit; a filter unit receiving the PWM signal from the CPU, filtering the PWM signal, and outputting the filtered signal; a feedback unit detecting the voltage applied to the fluorescent lamp and outputting a feedback signal; a controlling unit controlling the illumination of the fluorescent lamp based on the voltage input from the feedback unit, the controlling unit outputting a control signal variably controlling the voltage applied to the fluorescent lamp depending on the filtered signal; and a lamp drive unit applying variable AC voltage to the fluorescent lamp based on the control signal, thereby driving the fluorescent lamp. Accordingly, it is possible to control the luminous-intensity of the fluorescent lamp, reduce preheating time of the fluorescent lamp, extending the fluorescent lamp's lifetime, and lowering the power consumption.
1. A scanning apparatus having a lamp irradiating a light onto a printing medium and operating in at least one operation mode, comprising:
a central processing unit outputting a Pulse Width Modulated (PWM) signal having a variable duty ratio in accordance with the operation mode of the scanning apparatus; and
a lamp control unit varying a voltage applied to the lamp in accordance with the duty ratio of the PWM signal and outputting the varied voltage,
wherein the lamp control unit comprises:
a filter unit removing a noise from the variable signal output from the central processing unit; and
a drive unit varying the voltage applied to the lamp in accordance with the output from the filter unit and outputting the varied voltage.
2. The scanning apparatus according to claim 1 , wherein the operation mode of the scanning apparatus comprises at least one among a sleep mode, a scan mode and a stand-by mode.
3. The scanning apparatus according to claim 1 , wherein the operation mode of the scanning apparatus comprises at least one among a copy mode, a scan mode and a fax mode.
4. The scanning apparatus according to claim 1 , wherein the signal is a square wave signal.
5. The scanning apparatus according to claim 1 , wherein the variable signal is a Pulse Width Modulated (PWM) signal.
6. The scanning apparatus according to claim 1 , wherein the lamp is preheated under a low temperature and low impedance, extending the lamp's lifetime by varying the voltage applied to the lamp in accordance with the operation mode of the scanning apparatus, reducing power consumption.
7. The scanning apparatus according to claim 1 , wherein the operation mode of the scanning apparatus is performed in accordance with a scanning resolution.
8. The scanning apparatus according to claim 7 , wherein the scanning resolution varies in accordance with a text mode, a photo mode and a mixed mode.
9. The scanning apparatus according to claim 1 , wherein the drive unit comprises a feedback unit detecting the voltage applied to the lamp and outputting the detected voltage as a feedback signal;
a controlling unit comparing the feedback signal output from the feedback unit with the signal output from the filter unit, and outputting a control signal for variable control; and
a lamp drive unit varying the voltage applied to the lamp in accordance with the output from the controlling unit, and outputting the varied voltage.
10. The scanning apparatus according to claim 3 , wherein the controlling unit receives a first input voltage and a second input voltage, amplifies a voltage difference between the first and second input voltages, and outputs the voltage difference to the lamp drive unit.
11. The scanning apparatus according to claim 10 , wherein the first input voltage is a summation of the voltage output from the feedback unit and a reference voltage output from a reference voltage source.
12. The scanning apparatus according to claim 11 , wherein the reference voltage is a DC voltage.
13. The scanning apparatus according to claim 9 , wherein the controlling unit includes an amplifier having an inverting terminal receiving a first input voltage and a non-inverting terminal receiving a luminous-intensity adjusting signal externally input as a second input voltage, amplifies the voltage difference of the second and first input voltages, and outputs an amplified voltage difference.
14. The scanning apparatus according to claim 13 , wherein a first resistor and a first capacitor of the controlling unit are connected in series between an output terminal of the amplifier and the non-inverting of the amplifier, canceling oscillation components of the output amplified voltage difference.
15. The scanning apparatus according to claim 14 , wherein a second resistor and a second capacitor of the controlling unit are connected in series between the output terminal of the amplifier and a ground terminal, rectifying a ripple voltage of the output amplified voltage difference.
16. The scanning apparatus according to claim 15 , wherein a third resistor limits an amount of current rectified and output by the amplifier, and outputs the limited current to the lamp drive unit.
17. A method of controlling a scanning apparatus having a lamp irradiating a light onto a printing medium and operating in at least one operation mode, the method comprising:
outputting a Pulse Width Modulation (PWM) signal having a variable duty ratio in accordance with the operation mode of the scanning apparatus; and
varying the voltage applied to the lamp in accordance with the duty ratio of the PWM variable signal and outputting the varied voltage,
wherein the varying the voltage comprises:
filtering the variable signal and outputting a filtered signal; and
varying the voltage applied to the lamp in accordance with the filtered signal.
18. The method according to claim 17 , wherein the varying the voltage comprises:
detecting the voltage applied to the lamp and outputting the detected voltage as a feedback signal;
comparing the feedback signal with the filtered signal, and outputting a control signal; and
varying the voltage applied to the lamp in accordance with the output control signal.
19. The method according to claim 17 , wherein the operation mode of the scanning apparatus comprises at least one among a sleep mode, a scan mode and a standby mode.
20. The method according to claim 17 , wherein the operation mode of the scanning apparatus comprises at least one among a copy mode, a scan mode and a fax mode.
21. The method according to claim 17 , wherein the variable signal is a Pulse Width Modulated (PWM) signal.
22. The method according to claim 17 , wherein the variable signal is a square wave signal.
23. The method according to claim 17 , wherein the lamp is preheated under a low temperature and low impedance, extending the lamp's lifetime by varying the voltage applied to the lamp in accordance with the operation mode of the scanning apparatus, reducing power consumption.
24. The method according to claim 17 , wherein the operation mode of the scanning apparatus is performed in accordance with a scanning resolution.
25. The method according to claim 24 , wherein the scanning resolution varies in accordance with a text mode, a photo mode and a mixed mode.