JP2015019461A - Discharge circuit and flash discharge lamp lighting device for discharging residual voltage of power storage element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To attain both rapid discharge of a residual voltage and prevention of overheat of a discharge circuit, in the discharge circuit for discharging the residual voltage of a storage element.SOLUTION: A discharge circuit 250 for discharging a residual voltage of a storage element 11 includes: a discharge switch circuit 30 connected in parallel to the storage element 11 and composed of a plurality of discharge resistors 32 and a plurality of switch elements 34 capable of changing the connection state of the plurality of discharge resistors 32; and a control circuit 40 controlling the operating state of the plurality of switch elements 34 so as to reduce the combined resistance value of the discharge resistors 32 connected in parallel to the storage element 11 when the residual voltage is discharged.

Description

  The present invention relates to a discharge circuit for discharging a residual voltage of a storage element and a flash discharge lamp lighting device equipped with the discharge circuit.

  In order to measure the performance of various solar energy utilizing devices such as the photoelectric conversion characteristics of solar cells, a pseudo solar irradiation device that irradiates an object to be irradiated with pseudo sunlight that reproduces the spectral distribution of natural sunlight is known. In this type of simulated sunlight irradiating device, a light source composed of a xenon lamp is installed in a box, and simulated sunlight is emitted from the radiation surface by irradiating light from the light source through an optical filter.

  In this apparatus, for example, a xenon lamp having a light emission length of 1000 mm or more (hereinafter referred to as “lamp”) is used, a direct-current lamp current is applied, and the lamp current value is adjusted by the lighting device, whereby the illuminance on the irradiated surface Is controlled. Generally, the lamp current at the time of lighting is several tens of amperes (for example, 70 A), the lamp voltage is about several hundred volts (for example, 500 V), and the lamp current / voltage is from several tens of milliseconds per one lighting. Energized / applied for several hundred milliseconds. This output state is controlled by constant current or constant power, and the performance of the irradiated object is measured during the lighting period.

  In the above case, the lamp power is 35 kW, and even if it is instantaneous (for example, 100 milliseconds), if this power is supplied directly from the commercial power supply, it will cause a failure in peripheral equipment of the same commercial power system, The problem is that large capacity contacts and wiring are required between the devices. Therefore, in general, a lighting device is provided in the irradiation device, and in the lighting device, power is stored in a storage element such as a capacitor, and the stored power is supplied to the lamp in response to a lighting command (for example, Patent Document 1).

  In such a flash lamp lighting device, leaving the state in which the large-capacity storage element is charged at a high voltage when the lighting device is not used (for example, after the end of use) is a maintenance or misuse. It is not preferable considering the situation of time. Therefore, when not in use, a discharge circuit is provided in the power storage element in order to discharge the residual energy of the power storage element and keep the remaining voltage sufficiently low. For example, Patent Document 2 discloses a discharge switch (S3) that closes when a discharge valve (8) is removed, and a discharge resistor that discharges charges accumulated in a capacitor (5) when the discharge switch is closed. A discharge lamp lighting device comprising (7) is disclosed. Such a configuration of residual voltage discharge can be applied to the flash lamp lighting device.

JP 2008-300632 A JP 2008-60051 A

  By the way, in the flash discharge lamp lighting device, it is necessary to discharge the charging energy of the large-capacity storage element as described above in a short time. In particular, when it is necessary to repeatedly turn on the flash discharge lamp (that is, charge and discharge of the storage element) at a relatively short period, such as during maintenance and shipping adjustment, the residual voltage of the storage element is discharged in a short time. It is preferred that For example, in the work of finely adjusting the angle of the lamp reflector in order to optimize the illuminance uniformity, the process of charging the storage element, the process of checking the illuminance uniformity by lighting the lamp flash, the process of discharging the remaining voltage of the storage element The steps of shutting off the main power source, finely adjusting the reflector and re-turning on the main power source are repeated. Therefore, if the time required for the process of discharging the residual voltage of the power storage element is long, the time required for the entire work is increased, which is not preferable. In addition, if the discharge resistor that has generated heat in the one-time residual voltage discharging step of the storage element is not dissipated until the next same step, the discharge resistor is overheated in the above repetition, which is not preferable. Therefore, it is preferable to avoid an overheated state of the discharge resistor while shortening the discharge time of the residual voltage.

  However, according to the configuration in which the discharge circuit of the power storage element is formed with one discharge resistor as in Patent Document 2, a reduction in discharge time and avoidance of an overheated state of the discharge resistor are in a trade-off relationship. That is, when the resistance value of the discharge resistor is low, the time required for the discharge is shortened, but the current flowing at the start of the discharge becomes excessive, causing heat generation. Therefore, it is necessary to use a resistance element having a large current rating or rated power for the discharge resistance, which is not preferable from the viewpoint of miniaturization and cost reduction. On the other hand, when the resistance value of the discharge resistor is high, the current flowing at the start of discharge is small and heat generation can be suppressed, but the time required for discharge becomes long. Therefore, it is not preferable from the viewpoint of work efficiency during maintenance, shipping adjustment, and the like.

  Accordingly, an object of the present invention is to achieve both rapid discharge of the residual voltage and suppression of overheating of the discharge circuit in the discharge circuit for discharging the residual voltage of the storage element. It is another object of the present invention to provide a compact and low-cost flash discharge lamp lighting device that can quickly discharge a residual voltage and has excellent maintainability.

  A discharge circuit for discharging a residual voltage of a storage element according to the present invention includes a plurality of discharge resistors connected in parallel to the storage element and a plurality of switch elements capable of changing a connection configuration of the plurality of discharge resistors. A switching circuit; and a control circuit that controls operation states of the plurality of switching elements so as to gradually reduce the combined resistance value of the discharge resistors connected in parallel to the storage element when discharging the residual voltage. According to this configuration, the combined resistance value of a plurality of discharge resistors connected in parallel to the storage element decreases as the residual voltage decreases, so that the discharge is accelerated particularly when the residual voltage is low, and the discharge time is significantly shortened. The Further, since the discharge resistors are sequentially switched, a resistance element having a small rated value can be used for each discharge resistor, and the discharge circuit can be reduced in size and cost.

  The discharge circuit further includes a voltage detection circuit that detects a residual voltage of the storage element. The control circuit has a plurality of switch elements so as to gradually reduce the combined resistance value of the discharge resistors connected in parallel with the storage element in response to a decrease in the residual voltage detected by the voltage detection circuit when the residual voltage is discharged. Control the operating state of As a result, the switching timing of the combined resistance value of the discharge resistors can be optimized to achieve a desired discharge time, and the power consumption in each discharge resistor can be reliably managed. Further, even when there are variations in the capacity and remaining voltage of the power storage element, the above-described effects can be surely enjoyed.

  In one embodiment, the plurality of discharge resistors are first to n-th discharge resistors in descending order of the resistance value, the plurality of switch elements are first to n-th switch elements, and k of 1 ≦ k ≦ n The series circuit of the kth discharge resistor and the kth switch element is connected in parallel to the storage element, and the control circuit selectively selects the kth switch element in order of k = 1 to k = n when discharging the residual voltage. To conduct. Here, it is preferable that the selective conduction of the kth switch element is performed by alternative conduction of the kth switch element from k = 1 to k = n. Thereby, the heat release of the discharge resistor opened after conduction is promoted, and the overheating of the discharge resistor in the repeated charging / discharging of the storage element is suppressed.

  In another embodiment, the plurality of discharge resistors are connected in series, and the control circuit controls the operation state of the plurality of switch elements so as to reduce the number of discharge resistors forming the discharge path when discharging the residual voltage. Configured. According to this configuration, a resistance element having a rated voltage corresponding to a voltage value obtained by dividing the stored voltage by the number of discharge resistors can be used as the discharge resistor, contributing to downsizing and cost reduction of the discharge circuit.

  Specifically, the plurality of discharge resistors include first to n-th discharge resistors connected in series, a first switch element is connected in series to the first discharge resistor, and the first switch element is a storage element. The first switch element and the series circuit of the first to nth discharge resistors are connected in parallel with the storage element by being connected to the low potential side terminal and the nth discharge resistor being connected to the high potential side terminal of the storage element. For k of 2 ≦ k ≦ n, the k-th switch element is connected between the connection point of the (k−1) -th discharge resistance and the k-th discharge resistance and the low potential side terminal. The control circuit is configured to cause the kth switch element to conduct in the order of k = 1 to k = n when discharging the residual voltage. Thus, since each switch element is connected to the low potential side terminal of the power storage element, a simple and inexpensive discharge circuit is realized when a semiconductor switch is used for each switch element.

  A flash discharge lamp lighting device of the present invention includes a charging circuit that includes a storage element and charges the storage element, the discharge circuit, and a current control circuit that controls a current supplied to the flash discharge lamp using the voltage of the storage element as a power source And a central control unit that performs overall control of the charging circuit, the discharging circuit, and the current control circuit. This provides a flash discharge lamp lighting device that achieves high maintainability by shortening the discharge time and miniaturization and cost reduction by suppressing heat generation.

It is a circuit block diagram which shows the flash discharge lamp lighting device of this invention. It is a figure which shows the charging circuit in the 1st Embodiment of this invention. It is a figure which shows operation | movement of the charging circuit in the 1st Embodiment of this invention. It is a figure which shows the charging circuit in the 2nd Embodiment of this invention. It is a figure which shows an example of the charging circuit in the 2nd Embodiment of this invention. It is a figure which shows operation | movement of the charging circuit in the 2nd Embodiment of this invention.

<Basic configuration>
FIG. 1 shows a circuit configuration diagram of a flash discharge lamp lighting device (hereinafter referred to as “lighting device”) of the present invention. The lighting device 100 includes a rectification input circuit 150, a charging circuit 200, a discharging circuit 250, a current control circuit 300, and a control unit (CPU) 400. The control unit 400 controls the charging circuit 200, the discharging circuit 250, and the current control circuit 300 in an integrated manner. In the above and the following description, it is convenient for each circuit element to belong to which circuit, and the present invention is not bound thereto.

  In addition, the lighting device 100, a flash discharge lamp 500 connected to the lighting device 100 (hereinafter referred to as “lamp 500”), a casing (not shown) containing the lamp 500, input means to the lighting device 100, and the like. By providing, a flash irradiation device can be configured. When the flash irradiation device is a pseudo-sunlight irradiation device, the lamp 500 is a xenon lamp.

  The rectification input circuit 150 includes a rectifier 1 and a smoothing capacitor 2, and the AC power supply AC is full-wave rectified by the rectifier 1 and smoothed by the smoothing capacitor 2. In this embodiment, a capacitor input type circuit is used as the rectification input circuit 150, but a power factor correction circuit or the like may be used. Further, when a DC power supply is used as an input power supply instead of the AC power supply, the rectification input circuit 150 is not necessary.

  The charging circuit 200 includes a full bridge circuit composed of transistors 3 to 6, a PWM control circuit 7, a step-up transformer 8, a rectifier 9, a current limiting coil 10, a storage element 11, a voltage detection circuit 12, a current detection resistor 13, and an error amplifier 14. And a reference power supply 15. The full bridge circuit is switching-controlled by the PWM control circuit 7, and the transistors 3 and 6 and the transistors 4 and 5 are alternately turned on / off and the conduction time thereof is controlled. The output of the full bridge circuit is connected to the primary winding of the step-up transformer 8, and a voltage corresponding to the turn ratio is generated on the secondary side. The voltage generated in the secondary winding of the step-up transformer is rectified by the rectifier 9, output via the current limiting coil 10, and charged in the storage element 11. In the present embodiment, the power storage element 11 is an electrolytic capacitor, but the power storage element 11 may be an electric double layer capacitor, a battery, or the like. The voltage detection circuit 12 includes a voltage dividing resistor.

  When receiving the charge start signal from the central control unit 400, the PWM control circuit 7 starts charging by driving the full bridge circuit at several tens kHz (for example, about 50 kHz). During the charging operation, the error amplifier 14 and the PWM control circuit 7 operate so that the current value detected by the current detection resistor 13 (voltage generated in the current detection resistor 13) becomes equal to the target value (voltage of the reference power supply 15). Then, charging is performed with a predetermined charging current. The charging method is not limited to constant current control. When the charging voltage detected by the voltage detection circuit 12 reaches a set voltage (for example, about 1000 V) sufficiently higher than the lamp voltage, the PWM control circuit 7 temporarily stops the operation of the full bridge circuit (or holds the charging voltage). And transition to the standby state. Here, the PWM control circuit 7 outputs a charge completion signal to the central control unit 400.

  In the present disclosure, a circuit including a full bridge and a step-up transformer is illustrated as the charging circuit 200, but other boost converter type circuits may be employed as long as the step-up operation and the charging operation are possible. . Furthermore, when the charging circuit 200 is supplied with power from a high voltage power source, the boosting function is not necessary.

  The discharge circuit 250 includes a discharge switching circuit 30, a control circuit 40, and a voltage detection circuit 50. The voltage detection circuit 50 includes voltage dividing resistors 51 and 52. For convenience of explanation, the control circuit 40 is shown as a separate control circuit from the central control unit 400, but the control circuit 40 may be included in the central control unit 400 or the PWM control circuit 7. In addition, since the voltage detection circuit 50 can be configured with a voltage dividing resistor similar to that of the voltage detection circuit 12, the voltage detection circuit 12 can also serve as the voltage detection circuit in the discharge circuit 250 without providing the voltage detection circuit 50. Good. In this case, the output of the voltage detection circuit 12 is input not only to the PWM control circuit 7 but also to the control circuit 40. The discharge switching circuit 30 will be described later. In FIG. 1, the wiring in the discharge circuit 250 is shown in a simplified manner.

  The current control circuit 300 includes a semiconductor switch 16 such as an IGBT, a choke coil 17, a diode 18, a capacitor 19, a current detection resistor 20, a PWM control circuit 21, and an error amplifier 22, and constitutes a step-down chopper circuit. The current control circuit 300 also includes an igniter circuit 350. The igniter circuit 350 includes a start circuit 23 and a pulse transformer 24, and a secondary winding of the pulse transformer 24 is connected in series to the choke coil 17.

  The current control circuit 300 starts operation in response to a lighting signal from the central control unit 400 by using the voltage charged in the storage element 11 as a power source. When the PWM control circuit 21 of the current control circuit 300 starts operating in response to the lighting signal, a DC voltage substantially equal to the voltage of the storage element 11 is applied to both ends of the lamp 500 at the start of operation. On the other hand, the starting circuit 23 of the igniter circuit 350 is activated in response to the lighting signal to generate a pulse voltage in the primary winding of the pulse transformer 24, and the primary / secondary turns ratio of the pulse transformer 24 in the secondary winding. A high-pressure pulse corresponding to is generated. As a result, a voltage obtained by superimposing a high-voltage pulse on the voltage of the power storage element 11 is applied to the lamp 500, and dielectric breakdown of the lamp 500 occurs.

  When the lamp 500 is broken down, a limited current from the current control circuit 300 is input to the lamp 500 using the voltage of the power storage element 11 as a power source. The semiconductor switch 16 is switched by controlling the conduction time by the PWM control circuit 21. During the period when the semiconductor switch 16 is on, a current flows through the path of the storage element 11 → the semiconductor switch 16 → the choke coil 17 → the secondary winding of the pulse transformer 24 → the lamp 500 → the storage element 11. On the other hand, during the period when the semiconductor switch 16 is off, a current flows in the path of the choke coil 17 → the secondary winding of the pulse transformer 24 → the lamp 500 → the diode 18 → the choke coil 17 based on the electric power stored in the choke coil 17. Flowing. The capacitor 19 smoothes the output to the lamp 500 and suppresses or eliminates the ripple component of the lamp current. The lamp current is detected by the current detection resistor 20, and a voltage signal (detection voltage) proportional to the detected lamp current is input to the negative input terminal of the error amplifier 22. A voltage signal proportional to the set value of the lamp current is input from the central control unit 400 to the positive input terminal of the error amplifier 22. The conduction time of the semiconductor switch 16 is PWM controlled by the PWM control circuit 21 so that both inputs of the error amplifier 22 are equal. Thereby, the constant current direct current lighting of the lamp 500 which uses the electrical storage element 11 as a power source is performed.

  Here, when the discharge circuit 250 receives a residual voltage discharge signal indicating a command for discharging the residual voltage of the power storage element 11 from the central control unit 400, the discharge circuit 250 starts an operation of the residual voltage discharge. Details of the discharge operation by the discharge circuit 250 will be described later. At the end of the remaining voltage discharging operation by the discharging circuit 250, the central control unit 400 can output a recharging signal to the charging circuit 200 as necessary, and the charging circuit 200 can recharge the storage element 11. Thereby, the lamp discharge can be started immediately with respect to the next lighting signal.

  In the above basic configuration, each embodiment will be described below. In each embodiment, the discharge switching circuit 30 of the discharge circuit 250 is connected in parallel to the power storage element 11, and the switch that can change the connection configuration of the discharge resistors 32-1 to 32-n and the discharge resistors 32-1 to 32-n. Elements 34-1 to 34-n are provided. Note that 2 ≦ n. The switch elements 34-1 to 34-n may be semiconductor switches such as MOSFETs and IGBTs, or may be mechanical switches such as relay switches. Then, the control circuit 40 operates the switch elements 34-1 to 34-n so as to decrease the combined resistance value of the discharge resistors 32-1 to 32-n connected in parallel to the power storage element 11 when the residual voltage is discharged. Control the state. Here, with respect to the decrease in the residual voltage detected by the voltage detection circuit 50, the switch element so that the combined resistance value of the discharge resistors 32-1 to 32-n connected in parallel to the storage element 11 decreases stepwise. The operation states of 34-1 to 34-n are controlled. In the following description, the discharge resistors 32-1 to 32-n and the switch elements 34-1 to 34-n are collectively referred to as a representative or a part thereof, and the discharge resistor 32 and the switch, respectively. The element 34 is assumed.

Embodiment 1. FIG.
In the first embodiment, the first to nth discharge resistors 32-1 to 32-n and the corresponding first to nth switch elements 34-1 to 34-n are connected in series in descending order of resistance. Each series circuit is connected in parallel to the storage element 11. When the remaining voltage is discharged, the control circuit 40 selectively turns on the switch element 34k in the order of k = 1 to k = n.

  FIG. 2 shows details of the discharge circuit 250 according to the present embodiment. In this example, the case of n = 3 is shown, but the present embodiment is established even if n = 2 or 4 ≦ n. In the following description, the low potential side node of the power storage element 11 is referred to as a node NL, and the high potential side node is referred to as a node NH.

  The discharge switching circuit 30 includes a series circuit of a discharge resistor 32-1 and a switch element 34-1, a series circuit of a discharge resistor 32-2 and a switch element 34-2, and a series of a discharge resistor 32-3 and a switch element 34-3. A circuit is provided, and each series circuit is connected in parallel to the storage element 11. When the resistance values of the discharge resistors 32-1, 32-2 and 32-3 are R1, R2 and R3, respectively, it is assumed that R1> R2> R3.

  When the residual voltage is discharged, the control circuit 40 selectively turns on the switch elements 34-1, 34-2 and 34-3 in this order according to the decrease in the residual voltage detected by the voltage detection circuit 50. As described above with reference to FIG. 1, the voltage detection circuit 50 includes a voltage dividing circuit of resistors 51 and 52, and an output thereof is input to the control circuit 40.

  FIG. 3 shows the operation of the discharge circuit 250 according to the present embodiment. The upper graph shows the remaining voltage Vr of the storage element 11 detected by the voltage detection circuit 50, and the lower graph shows the operating states of the switch elements 34-1 to 34-3 (conductive when ON, open when OFF). . In the upper graph, the solid line indicates the change in the residual voltage Vr due to the discharge configuration of the present embodiment, and the broken line indicates the change in the residual voltage Vr when the discharge is continued only by the discharge resistor 32-1 as a comparative example. In addition, the horizontal axis of each graph shows the elapsed time from the start of discharge.

  The discharge of the residual voltage is started at time t0. It is assumed that the switch elements 34-1 to 34-3 are in the OFF state and the storage element 11 is charged with the voltage V0 (V0 = 900 V in this example) until just before time t0. At time t0, the control circuit 40 turns on the switch element 34-1 to connect the discharge resistor 32-1 to the power storage element 11 in parallel. The switch elements 34-2 and 34-3 are maintained in the OFF state.

  When the remaining voltage Vr becomes equal to or lower than the first set value V1 (V1 = 700 V in this example) at time t1, the control circuit 40 turns off the switch element 34-1 and turns on the switch element 34-2 to discharge resistance. 32-2 is connected to the electricity storage element 11 in parallel. The switch element 34-3 is maintained in the OFF state. Here, since the resistance value R2 of the discharge resistor 32-2 is smaller than the resistance value R1 of the discharge resistor 32-1, the discharge speed becomes faster than when the discharge is continued only by the discharge resistor 32-1 (broken line).

  When the remaining voltage Vr becomes equal to or lower than the second set value V2 (V2 = 400 V in this example) at time t2, the control circuit 40 turns off the switch element 34-2 and turns on the switch element 34-3 to discharge resistance. 32-3 is connected to the electricity storage element 11 in parallel. Note that the switch element 34-1 is maintained in the OFF state. Here, since the resistance value R3 of the discharge resistor 32-3 is smaller than the resistance value R2 of the discharge resistor 32-2, the discharge speed is further increased as compared with the case where the discharge is continued only by the discharge resistor 32-2.

  When the remaining voltage Vr decreases to the safe voltage V3 (for example, V3 = 50 V) at time t3, the discharge operation is finished. After time t3, the switch element 34-3 may be maintained in the ON state or may be in the OFF state.

Here, assuming that the capacity of the storage element 11 is C, the discharge times in the comparative example (broken line) and in the present embodiment (solid line) are compared. In the case of the comparative example, the time T _C1 (= t0 to t4) required for discharge is expressed by the following formula:
T _C1 = R1 × C × In (V0 / V3)
= 2.89 × R1 × C (Formula 1)
It is represented by On the other hand, in the case of the present embodiment, the time T _E1 (= t0 to t3) relating to discharge is expressed by the following formula:
T _E1 = R1 × C × In (V0 / V1) + R2 × C × In (V1 / V2) + R3 × C × In (V2 / V3)
= (0.41 * R1 + 0.56 * R2 + 2.08 * R3) * C (Formula 2)
It is represented by “Ln” represents a natural logarithm.

Here, R1: R2: R3 = 900 (V0): 700 (V1): 400 (V2) = 9: 7: 4. This is because the resistance elements having the same rated current are used by making the initial currents flowing through the discharge resistors 32 substantially equal. Thus, when R1: R2: R3 = 9: 7: 4, the discharge time T _E1 = 1.77 × R1 × C is shortened from Equation 2. Note that the ratio of R1: R2: R3 is not limited to the above as long as the initial current and power consumption flowing through each discharge resistor 32 are equal to or lower than the rated current and rated power. For example, if R1: R2: R3 = 3: 2: 1 in the setting of V0 to V3, the discharge time T _E1 = 1.48 × R1 × C is shortened from Equation 2 and the discharge time T _C1 = It can be about half of 2.89 × R1 × C.

  In addition, the power consumption of each of the discharge resistors 32-1 to 32-3 is about one-third that when the discharge is performed only with each of the discharge resistors. Therefore, as each discharge resistor 32, a small and inexpensive resistor element having a small rated power can be adopted. Further, due to the selective conduction of the switch element 32, the switch element 32 is dissipated in the OFF state after the ON state. Thereby, the heat release of the discharge resistor opened after conduction is promoted, and the overheating of the discharge resistor during repeated charging / discharging of the storage element is further suppressed. Furthermore, by distributing the discharge current path, stress (for example, loss due to internal resistance) related to each switch element 34 is also reduced.

  As described above, according to the discharge circuit 30 of the present embodiment, when the residual voltage is discharged, the switch element 34 is configured so that the combined resistance value of the discharge resistors 32-1 to 32-3 connected in parallel to the power storage element 11 decreases. The operating states of -1 to 34-3 are controlled. Therefore, when the residual voltage is lowered, the discharge rate is accelerated and the discharge time is greatly shortened. Further, since the discharge resistors 32 are sequentially switched, a resistance element having a small current rating can be used for each discharge resistor 32, and the discharge circuit 30 can be reduced in size and cost. In addition, since the decrease in the combined resistance value follows the decrease in the residual voltage, the switching timing of the combined resistance value of the discharge resistor 32 is optimized to achieve a desired discharge time, and the power consumption in each discharge resistor 32 is reliably managed. can do. And even when the capacity | capacitance and residual voltage of the electrical storage element 11 have dispersion | variation, said effect can be enjoyed reliably.

  In the present embodiment, the switch elements 34-1 to 34-n are selectively turned on and only one discharge resistor 32 is connected in parallel to the power storage element 11 at the same time. -1 to 34-n may be progressively conducted. That is, as the remaining voltage Vr decreases, the switch element 34 that is turned on is the switch element 34-1, the switch elements 34-1 and 34-2, the switch elements 34-1 to 34-3, and the switch element 34-1. ..., 34-4,..., All switch elements 34-1 to 34-n may be provided. When progressive conduction is performed in the configuration shown in FIG. 2, assuming that the resistance values of the discharge resistors 32-1, 32-2 and 32-3 are R11, R12 and R13, respectively, R11 = R1, 1 / (1 / R11 + 1 / R12) = R2, 1 / (1 / R11 + 1 / R12 + 1 / R13) = If R11, R12, and R13 are selected so as to be R3, a voltage change similar to that shown in the upper graph of FIG. 3 can be obtained. Can do. However, the heat dissipation effect (in the OFF state after the ON state) of the discharge resistor 32 as in the first embodiment cannot be obtained.

Embodiment 2. FIG.
In the first embodiment, the discharge resistors 32 are connected in parallel to the storage element 11. However, in the present embodiment, the discharge resistors 32-1 to 32-n connected in series are connected to the storage element 11. Shows a configuration connected in parallel. In the present embodiment, the control circuit 40 controls the operating state of each switch element 34 so as to reduce the number of discharge resistors 32 that form a discharge path when the power storage element 11 is discharged.

  In the present embodiment, a series circuit of a switch element 34-1 and discharge resistors 32-1 to 32-n is connected between the low potential node NL and the high potential node NH. For k of 2 ≦ k ≦ n, the switch element 34-k is connected between the connection point between the discharge resistor 32- (k−1) and the discharge resistor 32-k and the low potential node NL. Then, the control circuit 40 makes the switch element 34-1k conductive in the order of k = 1 to k = n when discharging the residual voltage.

  FIG. 4 shows details of the discharge circuit 250 according to the present embodiment. As described above, the discharge circuit 250 includes the discharge switching circuit 30, the control circuit 40, and the voltage detection circuit 50. Similar to the first embodiment, the voltage detection circuit 50 includes voltage dividing resistors 51 and 52. In this example, the case of n = 3 is shown, but the present embodiment is established even if n = 2 or 4 ≦ n.

  In the discharge switching circuit 30, one terminal of the switch element 34-1 is connected to the low potential node NL, the discharge resistor 32-1 is connected to the other terminal of the switch element 34-1, and the discharge resistors 32-1 to 32. -3 are connected in series, and the discharge resistor 32-3 is connected to the high potential node NH. The switch element 34-2 is connected between the connection point between the discharge resistor 32-1 and the discharge resistor 32-2, and the low potential node NL, and the switch element 34-3 is connected to the discharge resistor 32-2 and the discharge resistor 32-3. And the low potential node NL.

  The control circuit 40 causes the switch elements 34-1 to 34-3 to be made conductive alternatively or progressively in this order during discharging. That is, at the start of discharge, the control circuit 40 first turns on the switch element 34-1 and turns off the switch elements 34-2 and 34-3. Thereafter, the control circuit 40 turns on the switch element 34-2. At this time, the switch element 34-1 may be in an OFF state as an alternative conduction mode, or may be maintained in an ON state as a progressive conduction mode. Note that the switch element 34-3 is maintained in the OFF state. Thereafter, the control circuit 40 turns on the switch element 34-3. At this time, as an alternative conduction mode, the switch elements 34-1 and 34-2 may be in an OFF state, or both may be maintained in an ON state as the same progressive mode.

  As described above, each switch element 34 may be a semiconductor switch or a mechanical switch. However, since the low potential side terminals of all the switch elements 34 are connected to the low potential side node NL, each switch element 34. Can be configured with a semiconductor element such as a MOSFET to provide a simple and inexpensive configuration. FIG. 5 shows a circuit diagram of an example in which each switch element 34 is formed of a MOSFET. The drain terminal of each switch element 34 is connected to each resistance element, the source terminal is connected to the low potential side node NL, and the gate signal from the control circuit 40 is input to the gate terminal.

  FIG. 6 shows the operation of the discharge circuit 250 according to the present embodiment. The upper graph shows the remaining voltage Vr of the storage element 11, and the lower graph shows the operating states of the switch elements 34-1 to 34-3 (conductive when ON, open when OFF). As in FIG. 3, in the upper graph, the solid line represents the change in the residual voltage Vr due to the discharge configuration of the present embodiment, and the broken line represents a comparative example of the series circuit of the discharge resistors 32-1, 32-2 and 32-3. The change of the residual voltage Vr when a connection is continued is shown. Note that the change in the residual voltage Vr shown in the upper graph is the same as that in FIG. 3 according to the first embodiment, and thus detailed description thereof is omitted. In the present embodiment, the conduction of the switch element 34 is performed progressively, but even if the conduction of the switch element 34 is alternatively performed, the change in the residual voltage Vr shown in the upper graph is the same. It will be a thing.

  The discharge of the residual voltage is started at time t0. It is assumed that the switch elements 34-1 to 34-3 are in the OFF state and the storage element 11 is charged with the voltage V0 (V0 = 900 V in this example) until just before time t0. At time t0, the control circuit 40 turns on the switch element 34-1 to connect the discharge resistors 32-1 to 32-3 to the power storage element 11 in parallel. The switch elements 34-2 and 34-3 are maintained in the OFF state.

  When the remaining voltage Vr becomes equal to or lower than the first set value V1 (V1 = 700 V in this example) at time t1, the control circuit 40 turns on the switch elements 34-1 and 34-2 to substantially turn on the discharge resistor 32. -2 and 32-3 are connected to the storage element 11 in parallel. Here, “substantially” means that although the discharge resistor 32-1 is physically connected to the power storage element 11, it is short-circuited by the switch element 34-2, and therefore functions as a resistance element. 2 and 32-3. The switch element 34-3 is maintained in the OFF state. Here, since the resistance value R2 + R3 of the series circuit of the discharge resistors 32-2 and 32-3 is smaller than the resistance value R1 + R2 + R3 of the series circuit of the discharge resistors 32-1, 32-2 and 32-3, The discharge rate becomes faster than when the circuit continues to discharge (broken line).

  When the remaining voltage Vr becomes equal to or lower than the second set value V2 (in this example, V2 = 400 V) at time t2, the control circuit 40 turns on the switch elements 34-1 to 34-3 to substantially discharge the discharge resistor 32. −3 is connected in parallel to the electricity storage element 11. Here, since the resistance value R3 of the discharge resistor 32-3 is smaller than the resistance value R2 + R3 of the series circuit of the discharge resistors 32-2 and 32-3, the discharge value is further discharged than when the discharge is continued by the series circuit. Increases speed.

  When the remaining voltage Vr decreases to the safe voltage V3 (for example, V3 = 50V) at time t3, the discharge operation is finished. Note that after time t3, the switch elements 34-1 to 34-3 may be maintained in an ON state or may be in an OFF state.

Here, assuming that the capacity of the storage element 11 is C, the discharge times in the comparative example (broken line) and in the present embodiment (solid line) are compared. In the case of the comparative example, the time T _C2 (= t0 to t4) required for discharge is expressed by the following formula:
T _C2 = (R1 + R2 + R3) × C × In (V0 / V3)
= 2.89 × (R1 + R2 + R3) × C (Formula 3)
It is represented by On the other hand, in the case of the present embodiment, the time T _E2 (= t0 to t3) relating to discharge is expressed by the following formula:
T _E2 = (R1 + R2 + R3) × C × In (V0 / V1) + (R2 + R3) × C × In (V1 / V2) + R3 × C × In (V2 / V3)
= (3.05 × R1 + 0.97 × R2 + 0.41 × R3) × C (Formula 4)
It is represented by “Ln” represents a natural logarithm.

Here, R1: R2: R3 = 1: 1: 1. This is because resistance elements having the same rated voltage are used by equalizing the voltage applied to each discharge resistor 32. Thus, when R1 to R3 are equal, the discharge time T _C2 = 8.67 × R1 × C from Equation 3 and the discharge time T _E2 = 4.43 × R1 × C from Equation 4. Thus, the discharge time T _E2 in this embodiment is reduced to about half of the discharge time T _C2 of Comparative Example. Note that the ratio of R1: R2: R3 is not limited to the above as long as the voltage applied to each discharge resistor 32 is equal to or lower than the rated voltage of each resistance element.

  According to the above configuration, a resistance element having a small rated voltage corresponding to a voltage value obtained by dividing the charge setting voltage by the number of discharge resistors can be used as the discharge resistor, and the discharge circuit can be reduced in size and cost. In addition, the power consumption of each of the discharge resistors 32-1 to 32-3 is about one-third that when the entire discharge is performed with only one discharge resistor 32. Therefore, as each discharge resistor 32, a small and inexpensive resistor element having not only a small rated voltage but also a small rated power can be employed. Further, since the discharge current path is distributed, the stress on each switch element 34 is also reduced.

  Also in the configuration of the present embodiment, when the residual voltage is discharged, the combined resistance value of the discharge resistors 32-1 to 32-3 connected in parallel to the power storage element 11 decreases, so that the discharge speed is accelerated when the residual voltage is lowered. The discharge time is greatly shortened. Since the discharge resistors 32 are sequentially switched, a resistance element having a small rated voltage can be used for each discharge resistor 32, and the discharge circuit 30 can be reduced in size and cost. In addition, since the decrease in the combined resistance value follows the decrease in the residual voltage, the switching timing of the combined resistance value of the discharge resistor 32 is optimized to achieve a desired discharge time, and the power consumption in each discharge resistor 32 is reliably managed. can do. And even when the capacity | capacitance and residual voltage of the electrical storage element 11 have dispersion | variation, said effect can be enjoyed reliably.

  As described above, according to the first and second embodiments, in the discharge circuit 250 for discharging the residual voltage of the storage element 11, both rapid discharge of the residual voltage and suppression of overheating of the discharge circuit 30 are achieved. This is the issue. Further, by mounting such a discharge circuit 250, there is provided a lighting device 100 that realizes a reduction in charge and discharge cycles, that is, a reduction in cost and a reduction in cost due to high maintainability capable of shortening a lighting cycle and suppression of heat generation. .

Modified example.
Although the most preferred embodiment of the present invention has been described above, the present invention is not limited to the above configuration, and various modifications are possible as described below.

(1) Modification of switching timing of switch element 34 In each of the above-described embodiments, the configuration in which the operation state of each switch element 34 is controlled in response to the remaining voltage Vr being equal to or less than a predetermined set value has been described. In the case where the variation in the capacitance C of the storage element is small and the remaining voltage Vc is fixed, the operation state of each switch element 34 is controlled every time a fixed set time obtained experimentally is obtained. Also good. In this case, the voltage detection circuit 50 is unnecessary.

(2) Modification of the number of simultaneous connections In the above-described embodiments, the configuration in which the plurality of switch elements 34 are selectively or progressively connected is shown. However, the plurality of switch elements 34 are sequentially and repeatedly connected. It may be. For example, the two switch elements 34- (k-1) and 34-k may be selectively turned on sequentially from k = 2 to k = n. That is, first, the switch elements 34-1 and 34-2 are turned on, then the switch elements 34-2 and 34-3, then the switch elements 34-3 and 34-4, and finally the switch element 34. -(N-1) and 34-n may be turned on.

(3) Addition of notification means In each of the embodiments described above, a notification for notifying the user of a display indicating that the remaining voltage Vr of the power storage element 11 has become equal to or less than the safe voltage V3 (or still exceeds the safe voltage V3) Means may be provided. For example, when the residual voltage Vr detected by the voltage detection circuit 50 becomes 50 V or less, the control circuit 40 outputs a residual voltage discharge completion signal to the central control unit 400, and the central control unit 400 notifies the notification means. It can be set as the structure which performs. The notification means includes light emission by a light emitting body such as an LED, visual notification by display on a display such as a liquid crystal display, auditory notification by a buzzer sound, voice guidance, etc., or unlocking (or locking) the casing of the irradiation device, etc. It is only necessary to provide an operational notification according to or a combination thereof.

11 Storage element 30 Discharge switching circuit 32, 32-1, 32-2, 32-3, 32-n Discharge resistor 34, 34-1, 34-2, 34-3, 34-n Switch element 40 Control circuit 50 Voltage Detection circuit 100 Flash discharge lamp lighting device (lighting device)
200 charging circuit 250 discharging circuit 300 current control circuit 400 central control unit 500 flash discharge lamp (lamp)

Claims (7)

A discharge circuit for discharging the residual voltage of the storage element,
A discharge switching circuit comprising a plurality of discharge resistors connected in parallel to the power storage device and a plurality of switch elements capable of changing a connection configuration of the plurality of discharge resistors;
A discharge circuit comprising: a control circuit that controls an operation state of the plurality of switch elements so as to reduce a combined resistance value of discharge resistors connected in parallel to the power storage element when the residual voltage is discharged; The discharge circuit according to claim 1, further comprising a voltage detection circuit that detects a residual voltage of the storage element,
The control circuit gradually reduces the combined resistance value of the discharge resistors connected in parallel to the power storage elements with respect to the decrease in the residual voltage detected by the voltage detection circuit when the residual voltage is discharged. A discharge circuit configured to control operating states of the plurality of switch elements; 3. The discharge circuit according to claim 1, wherein the plurality of discharge resistors include first to n-th discharge resistors in descending order of resistance values, and the plurality of switch elements include first to n-th switch elements. For k of 1 ≦ k ≦ n, a series circuit of a kth discharge resistor and a kth switch element is connected in parallel to the power storage element,
A discharge circuit configured to selectively conduct the k-th switch element in the order of k = 1 to k = n when discharging the residual voltage;   4. The discharge circuit according to claim 3, wherein the selective conduction of the kth switch element is performed by alternative conduction of the kth switch element from k = 1 to k = n. Discharged circuit. The discharge circuit according to claim 1 or 2, wherein the plurality of discharge resistors are connected in series,
A discharge circuit configured to control operation states of the plurality of switch elements so that the control circuit reduces the number of discharge resistors forming a discharge path when the residual voltage is discharged; 6. The discharge circuit according to claim 1, wherein the plurality of discharge resistors include first to n-th discharge resistors, and the first to n-th discharge resistors are connected in series. A first switch element is connected in series to a resistor, the first switch element is connected to a low potential side terminal of the power storage element, and the nth discharge resistor is connected to a high potential side terminal of the power storage element. Thus, the first switch element and the series circuit of the first to nth discharge resistors are connected in parallel to the power storage element, and the kth switch element is k−1 for k of 2 ≦ k ≦ n. Connected between the connection point of the discharge resistance and the kth discharge resistance and the low potential side terminal,
A discharge circuit configured to cause the k-th switch element to conduct in the order of k = 1 to k = n when discharging the residual voltage; A charging circuit for charging the power storage element, including the power storage element;
The discharge circuit according to any one of claims 1 to 6,
A current control circuit for controlling the current supplied to the flash discharge lamp using the voltage of the storage element as a power source;
A flash discharge lamp lighting device comprising: a central control unit that performs overall control of the charging circuit, the power supply unit, and the current control circuit.

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