Discharge lamp lighting device and image display device with switching frequency
View Patent ↗An output of a load voltage detector is read by an A/D converter, and a reference value Is and a switching frequency are decided by a microcomputer. In order that the decided switching frequency can be achieved, a SET signal is inputted from a switching frequency counting unit to a drive controller, and a switching element is turned on. When a current flowing through the switching element, which is detected by a resistor, exceeds the reference value Is of a reference arithmetic unit, a RESET signal is inputted from a current detector to the drive controller, and the switching element is turned off. Thereafter, the reference value Is and the switching frequency are set so that the switching element can be turned on at the next time at timing when a regenerative current of a diode turns to substantial zero. As described above, the switching frequency is controlled in response to a state of a discharge lamp while controlling the switching element to turn on at the timing when the regenerative current turns to substantial zero without bringing up a cost increase of a discharge lamp lighting device.
1. A discharge lamp lighting device including a switching circuit that controls power supplied to a discharge lamp, in which, in the switching circuit, a switching frequency is controlled in response to a state of the discharge lamp, energy stored in an inductance component when a switching element is turned on is released when the switching element is turned off, and the switching element is controlled to turn on at a timing when a current for releasing the energy turns to substantial zero, the discharge lamp lighting device comprising:
a load voltage detector that detects a load voltage;
a switching frequency counting unit that performs time measurement for setting the switching frequency based on the voltage detected from the load voltage detector so that predetermined power of the discharge lamp can be achieved;
a current detector that detects that the current flowing through the switching circuit has reached a predetermined reference value;
a reference arithmetic unit that sets the predetermined reference value based on the voltage detected from the load voltage detector so that the switching element can be turned on and after the timing when the current for releasing the energy turns to substantial zero at the switching frequency set by the switching frequency counting unit; and
a drive controller that controls the switching element to turn on upon receiving a signal of the switching frequency counting unit, and controls the switching element to turn off upon receiving an output signal of the current detector.
2. The discharge lamp lighting device according to claim 1 , further comprising:
an input voltage detector that detects an input voltage of the switching circuit,
wherein, based on the input voltage detected from the input voltage detector and the load voltage detected from the load voltage detector, the switching frequency and the predetermined reference value are set so that the predetermined power of the discharge lamp can be achieved.
3. The discharge lamp lighting device according to claim 1 , wherein the switching frequency and the predetermined reference value are set so that the switching element can turn on at timing of a peak voltage of a free oscillation voltage generated when the current for releasing the energy becomes substantially zero.
4. The discharge lamp lighting device according to claim 1 , wherein, when the switching frequency set based on the voltage detected from the load voltage detector is superimposed on an operation-prohibited range, the switching frequency counting unit sets the switching frequency at a fixed frequency other than the operation-prohibited range.
5. An image display device, comprising:
the discharge lamp lighting device according to claim 1 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
6. The discharge lamp lighting device according to claim 2 , wherein the switching frequency and the predetermined reference value are set so that the switching element can turn on at timing of a peak voltage of a free oscillation voltage generated when the current for releasing the energy becomes substantially zero.
7. The discharge lamp lighting device according to claim 2 , wherein, when the switching frequency set based on the voltage detected from the load voltage detector is superimposed on an operation-prohibited range, the switching frequency counting unit sets the switching frequency at a fixed frequency other than the operation-prohibited range.
8. The discharge lamp lighting device according to claim 3 , wherein, when the switching frequency set based on the voltage detected from the load voltage detector is superimposed on an operation-prohibited range, the switching frequency counting unit sets the switching frequency at a fixed frequency other than the operation-prohibited range.
9. The discharge lamp lighting device according to claim 6 , wherein, when the switching frequency set based on the voltage detected from the load voltage detector is superimposed on an operation-prohibited range, the switching frequency counting unit sets the switching frequency at a fixed frequency other than the operation-prohibited range.
10. An image display device, comprising:
the discharge lamp lighting device according to claim 2 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
11. An image display device, comprising:
the discharge lamp lighting device according to claim 3 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
12. An image display device, comprising:
the discharge lamp lighting device according to claim 4 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
13. An image display device, comprising:
the discharge lamp lighting device according to claim 6 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
14. An image display device, comprising:
the discharge lamp lighting device according to claim 7 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
15. An image display device, comprising:
the discharge lamp lighting device according to claim 8 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.
16. An image display device, comprising:
the discharge lamp lighting device according to claim 9 ;
a discharge lamp turned on by the discharge lamp lighting device;
an image display mechanism that transmits therethrough or reflects thereon light from the discharge lamp; and
an optical system that projects transmission light or reflection light, which passes through the image display means, on a screen.