JP2011009081A - Discharge lamp-lighting device and projector device equipped with the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a discharge lamp-lighting device capable of carrying out abnormal detection immediately while downsizing and reducing cost, and to provide a projector device equipped with the same.SOLUTION: In the discharge lamp-lighting device, a detection part 7 for detecting failures such as going out of a lamp La or stopping of a switching circuit 10 is added to a current detection circuit 5. The detection part 7 is structured of: a series circuit consisting of a diode D11 and resistors R11, R12; and a peak hold circuit consisting of a capacitor C11 connected in parallel with the resistor R12, and detects a change of a switching current Is with the use of a resistor Rs fitted for controlling an output power or an output current of the switching circuit 10. When a detected result of the detection part 7 is to be a predetermined threshold value or smaller, the control circuit part 6 determines as an abnormal state with the lamp La turned off, and carries out an abnormal detection process for stopping a driving signal for output control of the switching circuit 10.

Description

  The present invention relates to a discharge lamp lighting device and a projector device including the same.

  2. Description of the Related Art Conventionally, there has been known an apparatus having a configuration in which an input power source is converted by a switching circuit to be controlled to a constant output voltage and load control is performed in a state where a relatively large impedance exists in series with a load. As a device of this type, for example, there is a discharge lamp lighting device using a resonant booster circuit by LC vibration as a method of obtaining a high voltage necessary for the initial discharge of the discharge lamp. An example of a discharge lamp lighting device having a resonant booster circuit using LC vibration is shown in FIG.

  The discharge lamp lighting device of FIG. 11 is connected between a switching circuit 10 composed of a step-down chopper circuit connected to a DC input power source E, an alternating circuit for converting the output of the switching circuit 10 into an alternating current, and an output terminal of the alternating circuit. And a load circuit 11 including an LC resonance circuit for generating a high voltage at startup. The switching circuit 10 includes a series circuit of a switching element Q1 composed of a MOSFET and a diode D1, and a series circuit of an inductor L1 and a capacitor C1 connected between both ends of the diode D1, and a step-down chopper for controlling an output voltage or output power. Configure the circuit. The alternating circuit is a full bridge connection of the switching elements Q2 to Q5, and the LC resonance circuit is an inductor L2 and a capacitor connected between the connection point of the switching elements Q2 and Q3 and the connection point of the switching elements Q4 and Q5. It consists of a series circuit of C2. A lamp (discharge lamp) La as a load is connected in parallel to the capacitor C2, and a high voltage is applied to the lamp La at the time of starting. The lamp La constitutes the load circuit 11 of the switching circuit 10 together with the alternating circuit and the LC resonance circuit.

  Further, the discharge lamp lighting device includes a voltage detection circuit 4 that detects an output voltage (a voltage across the capacitor C1) Vfb of the switching circuit 10, and a current detection circuit 5 that detects a switching current Is flowing through the switching element Q1 of the switching circuit 10. And a control circuit unit 6 that determines the operation timing of the switching elements Q1 to Q5. The control circuit unit 6 includes a microcomputer 1 and a logic circuit 2 that outputs a drive signal, and feeds back an output voltage Vfb detected by the voltage detection circuit 4 and a switching current Is detected by the current detection circuit 5 to perform switching. The operation timing of elements Q1-Q5 is determined. Here, the switching element Q1 of the switching circuit 10 is ON / OFF controlled by the drive circuit 3 that receives the drive signal from the logic circuit 2.

  In this type of discharge lamp lighting device, in the lamp La starting process, it is common to switch the operating states of the switching circuit 10 and the alternating circuit in the order of “starting voltage generation period”, “preheating period”, and “lighting period”. .

  Here, the starting voltage generation period is a period whose main purpose is to provide a starting voltage that promotes initial discharge of the lamp La. During this period, the switching circuit 10 is feedback-controlled so that the output voltage Vfb is fed back to the microcomputer 1 and the logic circuit 2 and the output voltage Vfb becomes a predetermined constant voltage. Then, the output (capacitor C1) of the switching circuit 10 at this time is used as a DC constant voltage source, and the alternating circuit is driven at an operating frequency f1 (for example, 40 to 150 kHz) commensurate with boosting by the inductor L2 and the capacitor C2. Therefore, during a no-load period until the lamp La is turned on, a predetermined high voltage for initial discharge is applied to the lamp La by a strong LC resonance operation by the inductor L2 and the capacitor C2, and the lamp La is lit (time). After t1), a relatively large series impedance is given to the lamp La by the inductor L2, and the lamp current is controlled to be substantially constant.

  The preheating period is a period in which the main purpose is to preheat (heat up) the electrodes of the lamp La, and control is performed so that the lamp La shifts to stable lighting (arc discharge) under the optimum conditions for the lamp life. Here, the electrode preheating is considered to be effective for extending the life of the lamp La by performing high frequency current. Therefore, during the preheating period, the switching circuit 10 is controlled so that the output voltage Vfb becomes a predetermined constant voltage by the same control as in the starting voltage generation period, and the alternating circuit is operated at the operating frequency f2 (for example, 30 to 80 kHz). By driving, a relatively large series impedance is given to the lamp La by the inductor L2, and a high-frequency preheating current optimum for preheating the lamp La is secured. At this time, generally, since a large amount of lamp current flows, the operating frequency f2 of the alternating circuit is set lower than the operating frequency f1 during the starting voltage generation period (f2 <f1).

  On the other hand, the lighting period is a period during which the lamp La is stably lit. In the lighting period, it is desirable that the operating frequency f3 of the alternating circuit is a much lower frequency (for example, 50 to 300 Hz) than the starting voltage generation period and the preheating period in consideration of the lamp life. Therefore, the inductor L2 does not function as a large impedance during the lighting period, and the voltage applied to the lamp La (hereinafter referred to as the lamp voltage Vla) and the output voltage Vfb of the switching circuit 10 have a relationship of Vla≈Vfb.

  During this lighting period, the switching circuit 10 feeds back, for example, a change in the lamp voltage Vla accompanying a change in mercury vapor pressure in the lamp La tube to the microcomputer 1 as a change in the output voltage Vfb detected by the voltage detection circuit 4. The switching frequency of the switching element Q1 and the peak threshold value (Ip threshold value) of the switching current Is are determined so that the output power or the output current matches Vla. Here, the current detection circuit 5 includes a resistor Rs that is a current detection element inserted between a connection point between the diode D1 and the capacitor C1 in the switching circuit 10 and the circuit ground, and a resistor connected between both ends of the resistor Rs. A peak detection value Ip of the switching current Is flowing through the resistor Rs is detected as a voltage across the capacitor C12. The voltage across the capacitor C12 is sent to the logic circuit 2 as an Ip detection signal, and the logic circuit 2 compares the peak detection value Ip with the Ip threshold value and performs control so as to obtain desired lamp power and current.

  In FIG. 12, the operating frequencies (alternating frequencies) f1, f2, and f3 of the alternating circuit during the starting voltage generation period, the preheating period, and the lighting period are shown in (a), and the output voltage Vfb (broken line) and the lamp voltage of the switching circuit 10 are shown. Vla (solid line) is shown in (b).

  Here, when the operating frequency of each period is determined as described above, the inductor L2 acts as a large series impedance with respect to the lamp La during the starting voltage generation period and the preheating period, and therefore, there is a relationship of Vfb ≠ Vla. The change in the lamp voltage Vla cannot be detected from the change in the output voltage Vfb. That is, during the starting voltage generation period and the preheating period, since the operating state (lighting and extinguishing) of the lamp La cannot be detected from the output voltage Vfb, the abnormality detection of the lamp La based on the output voltage Vfb has shifted to the lighting period. It is common to do this later.

  By the way, in recent years, in a short arc ultra-high pressure discharge lamp used in a projector device for image projection, the set time of the preheating period may be extended from several seconds to several tens of seconds in order to extend the life of the lamp La. Accordingly, if the abnormality of the lamp La is detected after the lighting period is started, the abnormality detection of the lamp La is significantly delayed from the conventional case, and the abnormality notification to the user is delayed or re-lighting is performed. This causes a problem that the start of operation is delayed.

  In order to solve this problem, a voltage detection circuit 8 capable of directly detecting the ramp voltage Vla is provided separately from the voltage detection circuit 5 that detects the output voltage Vfb of the switching circuit 10 as shown in FIG. It is conceivable to use the detection result at 8 for abnormality detection. However, in this case, it is necessary to configure the voltage detection circuit 8 with a high withstand voltage component capable of withstanding a high voltage at the time of starting the lamp La. By adding the voltage detection circuit 8, the discharge lamp lighting device is increased in size and cost. Is a problem.

  It is also conceivable to add a resistor for detecting an output current and detect whether the lamp La is turned on or off based on the detection result of the output current (see, for example, Patent Document 1). However, even in the method of detecting the output current, it is necessary to use an element that can withstand a relatively large amount of power as a resistor for detecting the output current. In this case also, the discharge lamp lighting device is increased in size and cost. Is a problem.

  On the other hand, when the switching circuit 10 is constituted by a chopper circuit as shown in FIG. 14, the level of the drive signal transmission from the control circuit unit 6 composed of the microcomputer 1 and the logic circuit 2 to the switching element Q1 at the floating potential. A shift circuit (drive circuit 3) is used, and a bootstrap circuit having a startup power supply loop may be used as a method of generating the upper stage power supply. In this case, the voltage Vbs of the upper power supply may drop due to the instantaneous power failure of the input power supply E or the voltage Vin of the input power supply E, the switching operation of the drive circuit 3 may stop, and the lamp La may turn off. In such a case, there is a problem that abnormality detection of the switching circuit 10 is delayed.

  That is, the bootstrap capacitor Cbs has a path (indicated by a broken line in FIG. 14) from the input power source E through the resistor R1 and the resistor constituting the voltage detection circuit 4 before the operation of the switching circuit 10 starts. The power supply is supplied only for the start-up. On the other hand, after the start of the operation of the switching circuit 10 in which the consumption current increases, the capacitor Cbs is further connected from the driving power supply (voltage Vcc) via the diode D2 when the diode D1 is in a conductive state (in FIG. 14, a solid line). In the circuit configuration shown in FIG.

  Here, if Vin ≦ Vfb due to instantaneous power failure or instantaneous voltage drop of the input power supply E, no current flows to the capacitor C1 even if the switching element Q1 is turned on. That is, no current flows through the inductor L1, and the diode D1 does not conduct when the switching element Q1 is turned off, so that power is not supplied from the drive power supply (Vcc) to the capacitor Cbs by the bootstrap circuit. Therefore, the voltage Vbs across the capacitor Cbs rapidly decreases, and the switching operation is stopped. Since the control circuit unit 6 cannot detect the stop of the drive circuit 3, the drive signal cannot be stopped, and the drive circuit 3 continues to receive the drive signal. As a result, although the power supply to the bootstrap capacitor Cbs is insufficient, the electric charge of the capacitor Cbs is consumed via the resistor R2 (indicated by a one-dot chain line in FIG. 14). I fall.

  Therefore, even after the power supply of the input power source E is restored, the voltage Vbs across the capacitor Cbs does not rise to a voltage that can drive the switching element Q1, and the switching circuit 10 cannot be restarted, so that the lamp La cannot be restarted.

  Further, as shown in FIG. 15, the output of the switching circuit 10 after the operation of the switching circuit 10 is stopped (time t2) includes a drive signal in a loop through the resistor R1 and the resistor constituting the voltage detection circuit 4. An output voltage Vfb is generated as a result of the loop through resistors R1 and R2 being combined. The output voltage Vfb at this time is often higher than the output voltage Vfb (≈Vla) immediately after the lamp La is turned on, and the state immediately after the lamp La is turned on is discriminated from the operation stop state of the switching circuit 10. Can not be converted. That is, since the output voltage Vfb is higher than the lamp voltage Vla, it is difficult to detect the stop of the switching circuit 10 using the change in the output voltage Vfb. Therefore, in the discharge lamp lighting device configured as described above, which detects an abnormality from the output voltage Vfb, it is not possible to detect the operation stop of the switching circuit 10 for a certain period of time (until time t3) after the lamp La is lit. I had to rely on returning to work. As a result, there is a problem that abnormality detection of the switching circuit 10 is delayed.

  In FIG. 15, the operating frequencies (alternating frequencies) f1, f2, and f3 of the alternating circuit during the starting voltage generation period, the preheating period, and the lighting period are shown in (a), the output voltage Vfb (broken line) of the switching circuit 10 and the lamp The effective value (solid line) of the voltage Vla is shown in (b). Further, in FIG. 15B, the effective value of the lamp voltage Vla at the time of normal lighting is indicated by a two-dot chain line.

JP-A-9-7783

  As described above, when priority is given to downsizing and cost reduction of the discharge lamp lighting device, it is difficult to quickly detect the abnormality of the lamp La and the switching circuit 10, and as a result, the abnormality is notified to the user. There is a problem that the operation is delayed or the operation start for relighting is delayed.

  The present invention has been made in view of the above-described reasons, and provides a discharge lamp spot device capable of promptly detecting an abnormality while allowing downsizing and cost reduction, and a projector apparatus including the discharge lamp spot device. The purpose is to do.

  The invention of claim 1 includes a switching circuit including a switching element that converts power so that the output voltage becomes a predetermined value by a switching operation of the switching element, and a current detection element that detects a switching current flowing through the switching element of the switching circuit. A current detection circuit that takes out the output of the current detection element by a detection circuit having a time constant set in accordance with the switching operation of the switching circuit, and for controlling the switching element of the switching circuit using the detection result of the detection circuit A discharge lamp lighting device that includes a control circuit unit that generates a drive signal and supplies the output power of the switching circuit to the lamp to light the lamp, and has a larger time constant than the detection circuit and outputs the current detection element The detection circuit has a detection unit that takes out the detection result of the detection unit. It is determined to be abnormal when a value below and having an abnormality detection means for stopping the drive signal.

  According to this configuration, the detection unit detects a switching current using a current detection element that is a part of a current detection circuit provided for output control of the switching circuit, and the abnormality detection unit includes the detection unit. Therefore, it is possible to realize abnormality detection without newly adding an element that can withstand relatively large electric power, leading to downsizing and cost reduction of the apparatus. Moreover, by detecting the abnormality from the detection result of the switching current, it is possible to quickly detect the abnormality due to the extinction of the lamp or the like as compared with the case of detecting the abnormality from the output voltage of the switching circuit.

  According to a second aspect of the present invention, in the first aspect of the invention, the control circuit unit in the level shift circuit includes a level shift circuit that transmits the drive signal to the switching element having a potential different from the stable potential of the control circuit unit. When generating a control power supply on the potential side different from the stable potential of the power supply, a bootstrap circuit having a startup power supply loop is used, and when the abnormality detection unit detects a detection result of the detection unit below a predetermined threshold value, It is determined that the switching operation of the switching circuit has stopped due to a voltage drop of the control power supply.

  According to this configuration, when a level shift circuit is used to transmit a drive signal from the control circuit unit to a switching element at a floating potential, and a bootstrap circuit having a startup power supply loop is used as a method of generating the control power supply, Even if an abnormality occurs in which the switching operation of the switching circuit stops due to the voltage drop, the abnormality can be detected promptly.

  According to a third aspect of the present invention, a power supply circuit using a boost chopper circuit and a switching current flowing through the switching element of the boost chopper circuit are detected by a current detection element, and a time constant set in accordance with the switching operation of the boost chopper circuit is set. A current detection circuit for taking out the output of the current detection element by a detection circuit having a control unit for controlling the switching element of the step-up chopper circuit using the detection result of the detection circuit, and an output voltage by switching operation of the switching element including the switching element A switching circuit that converts the output power of the power supply circuit so that becomes a predetermined value, and a control circuit unit that generates a drive signal for controlling the switching element of the switching circuit, and supplies the output power of the switching circuit to the lamp Discharge lamp lighting device for lighting the lamp, and in the detection circuit It has a detection unit that has a large time constant and takes out the output of the current detection element. When the detection result of the detection unit falls below a predetermined threshold value, the control unit determines that there is an abnormality and stops the drive signal. It has an abnormality detection means.

  According to this configuration, the detection unit detects the switching current using the current detection element that is a part of the current detection circuit provided for output voltage control of the boost chopper circuit, and the abnormality detection unit Since abnormality is judged using the detection result of the detection unit, abnormality detection can be realized without newly adding an element that can withstand relatively large power, leading to downsizing and cost reduction of the apparatus. Moreover, by detecting the abnormality from the detection result of the switching current, it is possible to quickly detect the abnormality due to the extinction of the lamp or the like as compared with the case of detecting the abnormality from the output voltage of the switching circuit.

  According to a fourth aspect of the present invention, the lamp restarting operation according to any one of the first to third aspects, wherein the abnormality detecting means determines that there is an abnormality and stops the drive signal, and then restarts the lamp after a predetermined time has elapsed. It is characterized by performing.

  According to this configuration, since the lamp restart operation is performed spontaneously after a certain time has elapsed after the drive signal is stopped, the time from the lamp turn-off to the restart can be shortened as much as possible.

  According to a fifth aspect of the present invention, the discharge lamp lighting device according to any one of the first to fourth aspects is provided, and an image is projected onto a screen using the lamp as a light source.

  According to this configuration, even when the preheating period is set to about several tens of seconds for extending the life of the lamp, it is possible to quickly detect an abnormality due to the extinction of the lamp or the like.

  In the present invention, the detection unit detects a switching current by using a part of a current detection circuit provided for output control of the switching circuit, and the abnormality detection unit uses the detection result of the detection unit to detect an abnormality. Therefore, there is an advantage that abnormality detection can be performed promptly while the size and cost of the apparatus can be reduced.

It is a schematic circuit diagram which shows the structure of Embodiment 1 of this invention. It is a schematic circuit diagram which shows the structure of a current detection circuit same as the above. It is a time chart which shows the operation example same as the above. It is a time chart which shows the operation example same as the above. It is a time chart which shows the operation example same as the above. It is a schematic circuit diagram which shows the structure of Embodiment 2 of this invention. It is a schematic circuit diagram which shows the other structure same as the above. It is explanatory drawing which shows operation | movement of Embodiment 3 of this invention. It is a schematic circuit diagram which shows the other structure of this invention. It is a schematic circuit diagram which shows other structure of this invention. It is a schematic circuit diagram which shows a prior art example. It is a time chart which shows operation | movement same as the above. It is a schematic circuit diagram which shows another prior art example. It is a schematic circuit diagram which shows another prior art example. It is a time chart which shows operation | movement same as the above.

(Embodiment 1)
As shown in FIG. 1, the discharge lamp lighting device of the present embodiment includes a switching circuit 10 composed of a step-down chopper circuit connected to a DC input power source E, an alternating circuit that converts the output of the switching circuit 10 into an alternating current, and And a load circuit 11 including an LC resonance circuit for generating a high voltage at the start, which is connected between output terminals of the alternating circuit. Further, the discharge lamp lighting device includes a voltage detection circuit 4 that detects an output voltage (a voltage across the capacitor C1) Vfb of the switching circuit 10, and a current detection circuit 5 that detects a switching current Is flowing through the switching element Q1 of the switching circuit 10. And a control circuit unit 6 that determines the operation timing of the switching elements Q1 to Q5. The basic configuration of these circuits is the same as that of the discharge lamp lighting device of FIG. 14 described in the background art section.

  The discharge lamp lighting device exemplified here is used in a projector device that projects an image on a screen using a short arc ultra-high pressure discharge lamp as a light source, and has a preheating period of about several tens of seconds for extending the life of the lamp La. Is set to

  Incidentally, in the discharge lamp lighting device of the present embodiment, as shown in FIG. 1, a detection unit 7 for detecting an abnormality such as extinction of the lamp La or stop of the switching circuit 10 is added to the current detection circuit 5. .

  That is, in the starting voltage generation period and the preheating period, the inductor L2 acts as the series impedance of the lamp La as described above, and therefore, the output voltage Vfb of the switching circuit 10 and the lamp voltage Vla have a relationship of Vfb ≠ Vla. The operating state of the lamp La cannot be detected from the change in the output voltage Vfb. However, during these periods, since the output voltage Vfb is controlled to be a predetermined constant voltage by the switching circuit 10, the current change of the switching circuit 10 becomes the change of the lamp operating state itself. Therefore, by detecting the change of the switching current Is flowing through the switching element Q1 of the switching circuit 10 by the detection unit 7, it is possible to detect the extinction of the lamp La.

  The current detection circuit 5 includes a resistor Rs which is a current detection element inserted between a connection point between the diode D1 and the capacitor C1 in the switching circuit 10 and the circuit ground, a resistor R13 and a capacitor connected between both ends of the resistor Rs. And a detection circuit including a series circuit of C12, and detects a current flowing through the resistor Rs as a voltage across the capacitor C12. The circuit constant of each element is determined so that the detection circuit including the resistor R13 and the capacitor C12 has a relatively small time constant (for example, less than the switching cycle of the switching circuit 10) in accordance with the switching operation of the switching circuit 10. The The voltage across the capacitor C12 is sent to the logic circuit 2 as an Ip detection signal, and is used to control the output power or output current of the switching circuit 10.

  As shown in FIG. 2, the detection unit 7 includes a peak hold circuit including a series circuit of a diode D11 and resistors R11 and R12, and a capacitor C11 connected in parallel to the resistor R12. A change in the switching current Is is detected using the resistor Rs. That is, the series circuit of the diode D11 and the resistors R11 and R12 is connected between both ends of the resistor Rs, and a voltage corresponding to the current flowing through the resistor Rs (hereinafter referred to as Is detection voltage) is generated between both ends of the capacitor C11. To do. The circuit constant of each element is determined so that the peak hold circuit as the detection unit 7 has a sufficiently large time constant as compared with the circuit including the resistor R13 and the capacitor C12 that generate the Ip detection signal. Depending on the configuration of the control circuit unit 6 that receives the detection result of the detection unit 7, a comparator that compares the voltage across the capacitor C11 (Is detection voltage) with the reference voltage and outputs the comparison result may be added. Good.

  Here, by setting the resistors R11 and R12 to an impedance (for example, 100 to 1000 times) sufficiently larger than the resistors Rs and R13, switching is performed without affecting the output power control that is the original function of the resistor Rs. It becomes possible to detect a change in the current Is. As a result, it is possible to detect a change in the switching current Is in a small size and at low cost without newly providing a large current detection element that can withstand high power.

  The control circuit unit 6 having the microcomputer 1 as a main configuration has a function as an abnormality detection unit that receives the detection result of the detection unit 7 and performs an abnormality detection process according to the detection result. If the Is detection voltage is equal to or lower than the predetermined threshold Vth, the control circuit unit 6 determines that the lamp La is in an abnormal state, and executes an abnormality detection process for stopping the output control drive signal of the switching circuit 10. To do.

  Next, operations in the starting voltage generation period, the preheating period, and the lighting period of the discharge lamp lighting device of the present embodiment will be described with reference to FIGS. 3 and 4, the operating frequency (alternating frequency) of the alternating circuit is (a), the effective value (represented by a solid line) of the output voltage Vfb (represented by a broken line) and the ramp voltage Vla of the switching circuit 10 is represented by (b), The effective value of the lamp current Ila is shown in (c), the power consumption Winv consumed in the load circuit 11 including the alternating circuit is shown in (d), and the Is detection voltage detected by the detector 7 is shown in (e). FIG. 3 shows an example of operation when the lamp La is normally lit, and FIG. 4 shows an example of operation when the lamp La is extinguished due to extinction during the starting voltage generation period.

  That is, when the lamp La is normally lit, as shown in FIG. 3, the output voltage Vfb of the switching circuit 10 is used as a DC constant voltage source during the starting voltage generation period and the preheating period, and is determined by the inductor L2 and the switching frequencies f1 and f2. A substantially constant power is supplied to the lamp La by the impedance, and an Is detection voltage corresponding to each output power is detected.

  On the other hand, as shown in FIG. 4, when the lamp La is once turned on (time t1) and then extinguished by turning off (time t2), high voltage is generated due to the strong resonance action of the inductor L2 and the capacitor C2 during the starting voltage generation period. Accordingly, large output power is consumed by the alternating circuit. Further, during the preheating period, the resonant action of the inductor L2 and the capacitor C2 is weakened, and the load power Winv consumed in the load circuit 11 including the alternating circuit is greatly reduced (no load operation). At this time (at the time of shifting to the preheating period), the Is detection voltage is not affected by the impedance action of the inductor L2, and greatly decreases as the load power Win changes. The control circuit unit 6 uses the change in the Is detection voltage, determines that the lamp La is in an abnormal state when the Is detection voltage is equal to or lower than a predetermined threshold Vth as shown in FIG. The drive signal for controlling the circuit 10 is stopped.

  With the configuration described above, the discharge lamp lighting device is relatively small and inexpensive, but the abnormality detection of the lamp La accompanying the prolonged preheating period is not delayed, and the abnormality is promptly (for example, within 1 second after startup). Detection processing can be performed. As a result, compared with the case where the lamp La is detected to be extinguished by the output voltage Vfb of the switching circuit 10, the abnormality detection process that is performed by detecting the extinction of the lamp La is started immediately after the preheating period is started. Can be expedited.

  In addition, although the structure which detects the state of the lamp | ramp La using the switching current Is of the switching circuit 10, and performs a predetermined | prescribed abnormality detection process is conventionally known (for example, refer Unexamined-Japanese-Patent No. 2002-324893), the said In the conventional example, in order to detect the switching current Is, it is necessary to newly add a resistor that can withstand large electric power. On the other hand, in this embodiment, a small time constant (for example, R = 470Ω, C = 0.22 nF) necessary for controlling the output power or output current of the switching circuit 10 is about several tens ns to several tens μs. Detection circuit (resistor R13, capacitor C12) for detecting the peak detection value Ip having a large time constant (for example, R = 1 MΩ) for the purpose of detecting an abnormality of the lamp La. , And a circuit having a C = 100 nF RC filter (detecting unit 7), the current detecting element (resistor Rs) is also used for detection. Accordingly, there is an advantage that the discharge lamp lighting device can be reduced in size and cost compared with the case where two different current detection circuits for different purposes are provided individually.

  Here, an increase in the lamp current Ila due to an abnormal discharge at the end of the life of the lamp La is detected by using a change in the switching current Is of the switching circuit 10, and if it exceeds a predetermined threshold, it is determined that the lamp La has reached an abnormal state. However, in this embodiment, the operating state of the lamp La is detected using the change in the switching current Is of the switching circuit 10, and it is determined that the lamp La is extinguished if the Is detection voltage is equal to or lower than a predetermined threshold value Vth. Shall.

  By the way, in this embodiment, as shown in FIG. 1, the switching circuit 10 is constituted by a chopper circuit, and is used to transmit a drive signal from the control circuit unit 6 including the microcomputer 1 and the logic circuit 2 to the switching element Q1 at the floating potential. A level shift circuit (drive circuit 3) is used, and a bootstrap circuit having a startup power supply loop is used as a method for generating an upper power supply (control power supply). Therefore, as described above, the voltage Vbs of the upper power supply may drop due to the instantaneous power failure or instantaneous voltage drop of the input power supply E, the switching operation of the drive circuit 3 may stop, and the lamp La may turn off. The reason is as described above. In short, the reason is that the control circuit unit 6 cannot promptly detect the stop of the switching circuit 10 due to the drop in the voltage Vbs of the upper power supply.

  In the present embodiment, from the detection result of the detection unit 7, an abnormality detection process for quickly detecting the switching operation stop of the drive circuit 3 due to the drop in the voltage Vbs of the upper power supply and returning to the control circuit unit 6 to stop the drive signal is performed. By executing it, the above problem can be solved.

  Hereinafter, the operation of the discharge lamp lighting device when the switching operation of the drive circuit 3 is stopped due to the decrease in the voltage Vbs of the upper power supply will be described with reference to FIG. In FIG. 5, the operating frequency (alternating frequency) of the alternating circuit is (a), the output voltage Vfb (represented by a broken line) and the effective value (represented by a solid line) of the lamp voltage Vla (b), and the lamp current Ila. (C), (d) shows the power consumption Winv consumed by the load circuit 11 including the alternating circuit, and (e) shows the Is detection voltage detected by the detection unit 7. In FIG. 5B, the effective value of the lamp voltage Vla at the time of normal lighting is indicated by a two-dot chain line.

  During the starting voltage generation period and the preheating period, after the lamp La is once turned on (time t1), when the switching operation of the drive circuit 3 is stopped due to the voltage Vbs drop of the upper power supply (time t2), the output voltage Vfb has a resistance R1. Then, a voltage is generated as a result of combining the loop via the resistors R1 and R2 according to the drive signal with the loop via the resistor constituting the voltage detection circuit 4. This voltage is often higher than the lamp voltage Vla immediately after the lamp La is turned on, and it is difficult to detect the stop of the switching operation using the change in the output voltage Vfb.

  On the other hand, since the Is detection voltage is a change of the switching current Is itself, it becomes substantially zero when the switching operation is stopped. The control circuit unit 6 uses the change in the Is detection voltage, and if the Is detection voltage becomes equal to or lower than the predetermined threshold Vth as shown in FIG. 5E, the switching operation is stopped at that time (time t2). The state is determined, and the drive signal output to the drive circuit 3 is stopped.

  As a result, even though the discharge lamp lighting device is relatively small and inexpensive, it is possible to promptly detect the stop of the switching operation due to the instantaneous power failure or the instantaneous voltage drop of the input power source E (for example, within 1 second after the activation). As a result, compared with the case where the stop of the switching operation is detected by the output voltage Vfb of the switching circuit 10, the start of the abnormality detection process performed by detecting the stop of the switching operation is performed immediately after the end of the preheating period and immediately after the stop of the switching operation. Can be expedited.

  Even if an integrated circuit (for example, HVIC) having a level shift function is used for the drive circuit 3, the same effect as described above can be obtained. Further, the current detection element may be any element that can detect a switching current, and is not limited to the resistor Rs, and for example, a current transformer or the like may be used.

(Embodiment 2)
As shown in FIG. 6, the discharge lamp lighting device according to the present embodiment includes a power supply circuit 20 having a commercial power supply AC as a power supply and having an active filter function for measures against distortion of the input current waveform from the commercial power supply AC (power factor improvement). The added point is different from the discharge lamp lighting device of the first embodiment.

  In the present embodiment, an abnormal state such as the extinction of the lamp La or the stop of the switching circuit 10 is detected by using the change in the switching current of the boost chopper circuit constituting the active filter of the power supply circuit 20.

  The power supply circuit 20 includes a rectifier DB for full-wave rectification of the commercial power supply AC and a boost chopper circuit connected to a DC output terminal of the rectifier DB, and inputs an output voltage of the boost chopper circuit to the switching circuit 10. The step-up chopper circuit includes a series circuit of a switching element Q20 including an inductor L20 and a MOSFET connected to the output of the rectifier DB, and a series circuit of a diode D20 and a capacitor C20 connected between both ends of the switching element Q20. .

  Further, the power supply circuit 20 includes a voltage detection circuit 24 that detects an output voltage (a voltage across the capacitor C20) Vout of the boost chopper circuit, a current detection circuit 25 that detects a switching current flowing through the switching element Q20 of the boost chopper circuit, And a control unit 21 that determines the operation timing of the switching element Q20. The control unit 21 feeds back the output voltage Vout detected by the voltage detection circuit 24 and the switching current detected by the current detection circuit 25, and changes the input current of the power supply circuit 20 along the sine wave of the commercial power supply AC voltage. And the output voltage of the power supply circuit 20 is controlled to a predetermined voltage.

  By the way, in this embodiment, the detection unit 27 for detecting an abnormality such as the extinction of the lamp La or the stop of the switching circuit 10 is replaced with the current detection circuit 5 for the booster chopper instead of the current detection circuit 5 for the switching circuit 10. 25. The detector 27 has the same configuration as the circuit shown in FIG.

  If an abnormality such as the extinction of the lamp La or the operation stop of the switching circuit 10 occurs, the output voltage of the power supply circuit (boost chopper circuit) 20 is constant, so that the load (load control circuit 30) viewed from the power supply circuit 20 is constant. The detection result (Is detection voltage) of the detection unit 27 changes due to the change in power consumption. Here, also in this embodiment, the operating frequency (alternating frequency) of the alternating circuit, the effective value of the output voltage Vfb and the lamp voltage Vla of the switching circuit 10, the effective value of the lamp current Ila, and the load circuit including the alternating circuit 11 and the Is detection voltage detected by the detection unit 27 are the same as those in FIGS. 3 to 5 described in the first embodiment. Therefore, by returning the detection result (Is detection voltage) of the detection unit 27 to, for example, the microcomputer 1 of the control circuit unit 6 and comparing it with the predetermined threshold value Vth, the same effect as in the first embodiment can be obtained.

  As a result, even when it is difficult to add the detection unit 7 to the load control circuit unit 30 or when the load control circuit 30 has no function of detecting a switching current as shown in FIG. It is possible to detect an abnormality in the load control circuit unit 30 without newly providing a current detection element. Even in the configuration described above, the detection unit 27 for detecting an abnormality using a part of the current detection circuit 25 provided for controlling the switching operation of the switching power supply (the power supply circuit 20 and the switching circuit 10) is provided. The configuration is the same as that of the first embodiment in that the drive signal for controlling the switching power supply (switching circuit 10) is stopped by the output of the detection unit 27.

  Other configurations and functions are the same as those of the first embodiment.

(Embodiment 3)
The discharge lamp lighting device according to the present embodiment has a restart function for performing a restart operation after a certain time (for example, 1 second) has elapsed after stopping output of the drive signal to the drive circuit 3 when an abnormality is detected. This is different from the discharge lamp lighting device of the first embodiment.

  In the present embodiment, as shown in FIG. 8, when the control circuit unit 6 detects the extinction of the lamp La or the stop of the switching circuit 10 after the start of the switching operation (time t1), the control circuit unit 6 controls the output of the switching circuit 10. An abnormality detection process for stopping the drive signal is performed (time t2). Thereafter, when a certain time (for example, 1 second) elapses, the control circuit unit 6 resumes output of the drive signal for output control of the switching circuit 10 and resumes the switching operation by the drive circuit 3 (time t3). As a result, the control circuit unit 6 can quickly and spontaneously try to restart without receiving a restart signal from the outside, so that the lamp La is extinguished as much as possible and the lighting is reliably performed. Can be improved.

  Other configurations and functions are the same as those of the first embodiment.

  By the way, the discharge lamp lighting device according to the present invention is not limited to those exemplified in each of the above-described embodiments, and has the same effect even if there are various modifications and corrections within the scope of the present invention. For example, even when the buck-boost circuit shown in FIG. 9 or the flyback circuit shown in FIG. 10 is used as a circuit for controlling the load, it is the same as the present invention by providing a detection unit in parallel with the resistor that detects the switching current. The effect is obtained.

3 Drive circuit (level shift circuit)
5 Current detection circuit 6 Control circuit (Abnormality detection means)
7 detector 10 switching circuit 20 power supply circuit C11 capacitor D11 diode Is switching current La lamp Q1-Q5, Q20 switching element R11, R12 resistance Rs resistance (current detection element)

Claims (5)

  A switching circuit including a switching element that converts power so that the output voltage becomes a predetermined value by a switching operation of the switching element, and a switching current flowing through the switching element of the switching circuit is detected by a current detection element, and the switching operation of the switching circuit Current detection circuit that takes out the output of the current detection element with a detection circuit having a time constant set in accordance with the control circuit, and a control circuit that generates a drive signal for controlling the switching element of the switching circuit using the detection result of the detection circuit And a discharge lamp lighting device for lighting the lamp by supplying the output power of the switching circuit to the lamp, and having a detection unit that has a larger time constant than the detection circuit and takes out the output of the current detection element When the detection result of the detection unit falls below a predetermined threshold, Is determined to be abnormal, the discharge lamp lighting apparatus characterized by having an abnormal detection means for stopping the drive signal.   A level shift circuit that transmits the drive signal to the switching element having a potential different from the stable potential of the control circuit unit is provided, and a control power source on the potential side different from the stable potential of the control circuit unit in the level shift circuit is generated. A bootstrap circuit having a startup power supply loop is used, and the abnormality detection means stops the switching operation of the switching circuit due to a voltage drop of the control power supply when the detection result of the detection unit becomes a predetermined threshold value or less. The discharge lamp lighting device according to claim 1, wherein the discharge lamp lighting device is determined to be abnormal.   A power detection circuit using a boost chopper circuit and a switching current flowing through the switching element of the boost chopper circuit are detected by a current detection element, and a current detection element having a time constant set in accordance with the switching operation of the boost chopper circuit A current detection circuit for taking out the output of the output, a control unit for controlling the switching element of the step-up chopper circuit using the detection result of the detection circuit, and a switching element including the switching element so that the output voltage becomes a predetermined value by the switching operation of the switching element A switching circuit that converts the output power of the power supply circuit and a control circuit unit that generates a drive signal for controlling the switching element of the switching circuit are provided to supply the output power of the switching circuit to the lamp and turn on the lamp. It is a lighting device and has a larger time constant than the detection circuit. It has a detection unit that takes out the output of the holding current detection element, and the control circuit unit has an abnormality detection means that determines that an abnormality occurs when the detection result of the detection unit falls below a predetermined threshold and stops the drive signal. A discharge lamp lighting device characterized by.   The said abnormality detection means performs the restarting operation | movement of the said lamp after progress for a fixed time, after determining that it is abnormal and stopping the said drive signal. Discharge lamp lighting device. A projector apparatus comprising the discharge lamp lighting device according to any one of claims 1 to 4, wherein an image is projected on a screen using the lamp as a light source.

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