Pulse width modulation apparatus and apparatus for driving light source having the same
View Patent ↗Provided are a pulse width modulation (PWM) apparatus and a light source-driving apparatus including the PWM apparatus. The PWM apparatus includes a voltage division part, a capacitor part, a first operational amplifier, a first noise reduction part, and a second operational amplifier. The voltage division part divides and outputs an input voltage. The capacitor part charged by an input current or discharged for provides a charge voltage. The first operational amplifier operates according to a result of comparing a divided voltage output from the voltage division part with the charge voltage output from the capacitor part. The first noise reduction part removes a high frequency noise of the divided voltage. The second operational amplifier converts a signal generated from the capacitor part into a pulse width modulation signal by a dimming control signal.
1. A pulse width modulation apparatus comprising:
a voltage division part dividing and outputting an input voltage;
a capacitor part charged by an input current or discharged for providing a charge voltage;
a first operational amplifier operating according to a result of comparing the divided voltage output from the voltage division part with the charge voltage output from the capacitor part;
a first noise reduction part removing a high frequency noise of the divided voltage; and
a second operational amplifier converting a signal generated from the capacitor part into a pulse width modulation signal by a dimming control signal.
2. The pulse width modulation apparatus according to claim 1 , wherein the voltage division part is connected to an output terminal of the first operational amplifier to form a feedback path.
3. The pulse width modulation apparatus according to claim 1 , wherein the voltage division part supplies the divided voltage corresponding to a square wave pulse to the first operational amplifier according to whether the first operational amplifier is a high state or a low state.
4. The pulse width modulation apparatus according to claim 1 , wherein the capacitor part is connected to an inverting terminal of the first operational amplifier and a non-inverting terminal of the second operational amplifier.
5. The pulse width modulation apparatus according to claim 1 , wherein the capacitor part comprises at least one capacitor to output a triangle wave signal.
6. The pulse width modulation apparatus according to claim 1 , wherein the first operational amplifier operates on an open-collector mode.
7. The pulse width modulation apparatus according to claim 1 , wherein the first noise reduction part comprises at least one capacitor, one end of the capacitor being connected to the voltage division part, the other end of the capacitor being grounded.
8. The pulse width modulation apparatus according to claim 1 , wherein the first noise reduction part makes an edge of the divided voltage output from the voltage division part rounded.
9. The pulse width modulation apparatus according to claim 1 , comprising a second noise reduction part formed at an output terminal of the second operational amplifier, the second noise reduction part removing a high frequency noise from the pulse width modulation signal.
10. The pulse width modulation apparatus according to claim 9 , wherein the second noise reduction part comprises at least one capacitor of which one end is grounded.
11. A pulse width modulation apparatus comprising:
a triangle wave-generating circuit outputting a triangle wave signal by comparing a first voltage with a second voltage of a charged capacitor part, the first voltage being generated by removing a high frequency noise from an input voltage of the triangle wave-generating circuit; and
a pulse width modulation circuit converting the triangle wave signal output from the triangle wave-generating circuit into a pulse width modulation signal according to a dimming control signal.
12. The pulse width modulation apparatus according to claim 11 , wherein the triangle wave-generating circuit comprises an operational amplifier, the first voltage is divided and input to a non-inverting terminal of the operational amplifier, and the second voltage is input to the inverting terminal of the operational amplifier.
13. The pulse width modulation apparatus according to claim 11 , wherein the triangle wave-generating circuit comprises an operational amplifier, the triangle wave signal is input to a non-inverting terminal of the operational amplifier, and the dimming control signal is input to an inverting terminal of the operational amplifier.
14. The pulse width modulation apparatus according to claim 11 , wherein the pulse width modulation circuit comprises a second noise reduction part removing a high frequency noise from the pulse width modulation signal.
15. The pulse width modulation apparatus according to claim 11 , wherein the pulse width modulation circuit comprises a dimming voltage control part supplying a predetermined base voltage to a voltage of the dimming control signal.
16. A light source-driving apparatus comprising:
a pulse width modulation part including a triangle wave-generating circuit and a pulse width modulation circuit, the triangle wave-generating circuit outputting a triangle wave signal by comparing a square wave pulse without a high frequency noise to a charged reference voltage, the pulse width modulation circuit converting the triangle wave signal output from the triangle wave-generating circuit into a pulse width modulation signal according to a dimming control signal;
a control part outputting a control signal for controlling a light source according to the pulse width modulation signal; and
a switching part converting input power into alternating current power according to the control signal of the control part.
17. The light source-driving apparatus according to claim 16 , wherein the triangle wave-generating circuit comprises:
a voltage division part dividing an input voltage for converting the input voltage into a square wave pulse;
a capacitor part charged by an input current or discharged for providing the triangle wave signal;
a first operational amplifier operating according to a result of comparing the square wave pulse output from the voltage division part with a charge voltage output from the capacitor part; and
a first noise reduction part removing the high frequency noise from the square wave pulse input to the first operational amplifier.
18. The light source-driving apparatus according to claim 17 , wherein the pulse width modulation circuit comprises a second operational amplifier converting the triangle wave signal output from the capacitor part into the pulse width modulation signal according to the dimming control signal.
19. The light source-driving apparatus according to claim 17 , comprising a transformer supplying a raised voltage to the light source using the alternating current power of the switching part,
wherein the first noise reduction part includes at least one capacitor having one end connected to the voltage division part and the other end connected to the ground.
20. The light source-driving apparatus according to claim 18 , comprising a second noise reduction part formed at an output terminal of the second operational amplifier, the second noise reduction part removing a high frequency noise from the pulse width modulation signal.