JP2011250546A - Power supply unit and luminaire using the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply unit and a luminaire using the same capable of suppressing electrical stress against both of overvoltage state and surge.SOLUTION: A power supply unit includes: a dc-dc converter 11 converting and outputting output power of a direct current power supply E, having a switching element Q0; a drive part DR driving the switching element Q0; and a control part 2 controlling the drive part DR. Moreover, the power supply unit further includes two comparators 31 and 32, while each of these compares an input voltage Vin from the direct current power supply E to a predetermined threshold level, when the input voltage Vin exceeds the threshold level, it stops the drive part DR. The second comparator 32 has the higher threshold level and a smaller time constant than the first comparator 31. In case of overvoltage state in which a state in which the input voltage Vin is slightly high continues a prolonged period, electrical stress is suppressed by an action of the first comparator 31. In case of surge in which the input voltage Vin suddenly elevates, the electrical stress is suppressed by an action of the second comparator 32.

Description

  The present invention relates to a power supply device and a lighting device using the power supply device.

  Conventionally, a power supply device using a switching converter that appropriately converts and outputs electric power input from a DC power supply has been provided (see, for example, Patent Document 1).

  An example of this type of power supply is shown in FIG. This power supply device has at least one switching element, converts the output power of the DC power supply E and outputs it to the load circuit LO in the subsequent stage, and drives each switching element of the switching converter 1. A drive unit DR and a control unit 2 that controls the drive unit DR are provided.

  The switching converter 1 is, for example, a well-known DC-DC converter that converts the output voltage of the DC power supply E, and the load circuit LO is, for example, an inverter that converts DC power output from the switching converter 1 into AC power and an AC output from the inverter. It consists of a discharge lamp that is turned on by electric power.

  Here, a case where a plurality of loads are connected to the DC power source E as in the case where the DC power source E is an automobile battery, and an inductive load such as a motor or an electromagnetic relay is connected to the plurality of loads. When the inductive load is stopped, the input voltage from the DC power source E temporarily rises, and this voltage rise causes excessive electrical stress on the circuit components of the switching converter 1. There is such a possibility.

  Therefore, the power supply device of FIG. 8 includes a first comparison unit 31 that compares the input voltage Vin from the DC power supply E to the switching converter 1 with a predetermined first threshold value and generates an output corresponding to the comparison result. When the output indicating that the input voltage Vin exceeds the first threshold is input from the first comparison unit 31, the control unit 2 stops driving each switching element in the switching converter 1 ( That is, the drive unit DR is controlled so as to stop the operation of the drive unit DR. Thereby, the electrical stress concerning each circuit component is suppressed.

  More specifically, the first comparison unit 31 includes a voltage dividing circuit that divides the input voltage Vin, a capacitor that smoothes the voltage divided by the voltage dividing circuit, and a voltage across the capacitor as a predetermined reference voltage. A comparator that compares and generates an output according to the comparison result. The output of the comparator is input to the control unit 2. That is, the reference voltage is a voltage obtained by multiplying the first threshold value by the voltage dividing ratio of the voltage dividing circuit.

  Input voltage

JP 2004-273172 A

  By the way, as a method for preventing a malfunction in which the output of the first comparison unit 31 is changed due to noise mixed in the input voltage Vin and the drive unit DR is stopped although it is not necessary to stop the drive unit DR. The method of raising the reference voltage in the 1st comparison part 31 and the method of raising the capacitance of the capacitor | condenser in the 1st comparison part 31 can be considered.

  However, when the reference voltage in the first comparison unit 31 is increased, the first threshold value is also increased. Therefore, an abnormality in which the state where the input voltage Vin is slightly higher than the normal value continues for a long time (hereinafter referred to as “overvoltage state”). Drive unit DR cannot be stopped. For example, in an automobile, the above-described overvoltage state may occur due to aged deterioration of a battery serving as the DC power source E.

  On the other hand, when the capacitance of the capacitor in the first comparison unit 31 is increased, the time constant of the voltage dividing circuit and the capacitor in the first comparison unit 31 increases, so that an abnormality (such as an abrupt increase in the input voltage Vin) ( Hereinafter, the response to “surge” is delayed. For example, in the case of an automatic person, the above-described surge occurs when a disconnection or poor contact occurs between the battery and another load connected to the battery during the period when the battery is charged. There is a load dump surge.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a power supply device capable of suppressing electrical stress against both an overvoltage state and a surge, and a lighting device using the same. There is.

  The power supply device of the present invention includes a switching converter that has at least one switching element and converts and outputs input power from a DC power supply, a driving unit that drives each switching element of the switching converter, and the drive A control unit that controls the switching unit, and the input voltage from the DC power source to the switching converter is compared with a predetermined first threshold, and each switching element in the switching converter is driven when the input voltage exceeds the first threshold. A first comparison unit for stopping the input, and comparing the input voltage from the DC power source to the switching converter with a predetermined second threshold value higher than the first threshold value, and when the input voltage exceeds the second threshold value, Second to stop driving each switching element in the switching converter Each of the first comparison unit and the second comparison unit includes a voltage dividing circuit that divides the input voltage, a capacitor that smoothes the voltage divided by the voltage dividing circuit, and A comparator that compares the voltage across the capacitor with a predetermined reference voltage and generates an output in accordance with the comparison result. In the first comparator, the reference voltage is divided into the first threshold by the voltage dividing circuit. The reference voltage is a value obtained by multiplying the second threshold by the voltage dividing ratio of the voltage dividing circuit, and at least the input voltage is from 0V to the second voltage. The first comparison unit and the second comparison unit are configured such that when the voltage is changed stepwise to a voltage higher than the threshold value, the second comparison unit is stopped before the first comparison unit is stopped. Each smell with the comparison part Characterized in that the circuit constants are determined, respectively.

  Another power supply apparatus according to the present invention includes a switching converter that has at least one switching element and converts and outputs input power from a DC power supply, and a driving unit that drives each switching element of the switching converter. A control unit that controls the drive unit, and a first comparison unit that compares an input voltage from the DC power source to the switching converter with a predetermined first threshold and generates an output according to the comparison result, The control unit controls the driving unit to stop driving each switching element in the switching converter when an output indicating that the input voltage exceeds the first threshold is input from the first comparison unit. An input voltage from the DC power source to the switching converter is a predetermined value higher than the first threshold value. A second comparison unit for comparing with a second threshold, wherein the first comparison unit and the second comparison unit are respectively divided by the voltage dividing circuit for dividing the input voltage and the voltage dividing circuit. A capacitor for smoothing the voltage, and a comparator for comparing the voltage across the capacitor with a predetermined reference voltage and generating an output in accordance with the comparison result. In the first comparison section, the reference voltage is the first voltage The threshold value is a value obtained by multiplying the voltage dividing circuit by the voltage dividing circuit, and the reference voltage in the second comparison unit is a value obtained by multiplying the second threshold value by the voltage dividing ratio of the voltage dividing circuit, and at least the When the input voltage changes stepwise from 0V to a voltage higher than the second threshold, the output of the comparator at the second comparison unit is changed before the output of the comparator at the first comparison unit changes. As shown, the circuit constants are determined in each of the first comparison unit and the second comparison unit, and the voltage across the capacitor exceeds the reference voltage in the second comparison unit. It is characterized by comprising current increasing means for temporarily increasing the charging current of the capacitor in the first comparison unit during the period.

  In the above power supply device, the voltage across both switching elements of the switching converter is compared with a predetermined third threshold value, and each switching element in the switching converter is driven when the voltage across the voltage exceeds the third threshold value. It is desirable to provide a third comparison unit that stops the operation.

  Further, in the power supply device described above, the effective value of the output voltage of the switching converter is compared with a predetermined fourth threshold value, and each switching element in the switching converter is driven when the effective value exceeds the fourth threshold value. It is desirable to include a fourth comparison unit that is stopped.

  The illumination device of the present invention includes any one of the power supply devices described above and an electrical light source that is turned on by the output power of the switching converter.

  According to the present invention, in the case of an overvoltage state where the input voltage is slightly high for a long time, the electrical stress is suppressed by the operation of the first comparison unit, and in the case of a surge in which the input voltage rises rapidly, Electrical stress is suppressed by the operation of the two comparison units.

It is a circuit block diagram showing an embodiment of the present invention. It is a circuit block diagram which shows an example of the principal part same as the above. The input voltage Vin, the voltage Vc1 / Rt1 obtained by dividing the voltage Vc1 across the capacitor in the first comparison unit by the voltage dividing ratio of the voltage dividing circuit, and the voltage Vc2 across the capacitor in the second comparing unit divided by the voltage dividing ratio of the voltage dividing circuit. It is explanatory drawing which shows an example of a time change with the voltage Vc2 / Rt2. It is a disassembled perspective view which shows the same as the above. It is a circuit block diagram which shows the example of a change same as the above. It is a circuit block diagram which shows the principal part of another example of a change same as the above. It is explanatory drawing which shows an example of the time change of the input voltage Vin in the example of FIG. 6, the both-ends voltage Vc1 of the capacitor | condenser in a 1st comparison part, and the output S2 of a 2nd comparison part. It is a circuit block diagram which shows a prior art example.

  The best mode for carrying out the present invention will be described below with reference to the drawings.

  As shown in FIG. 2, the present embodiment is connected to a DC power source E and a high-pressure discharge lamp DL as an electric light source, and turns on the high-pressure discharge lamp DL using the DC power source E as a power source. The high-pressure discharge lamp DL is a light-transmitting bulb made of a material such as glass, in which an electrode and a high-pressure metal vapor are sealed, and an arc discharge is generated between the electrodes in the metal vapor. It uses light emission from time to time and is also called an HID lamp (High Intensity Discharge lamp). The DC power source E is a battery mounted on, for example, an automobile (not shown), and the high-pressure discharge lamp DL is a headlamp, for example.

  More specifically, in the present embodiment, a DC voltage (hereinafter referred to as “output voltage”) obtained by converting a voltage value of a DC voltage (hereinafter referred to as “input voltage”) Vin input from the DC power source E via the input filter IF. The DC-DC converter 11 serving as a switching converter that outputs Vdc and the output of the DC-DC converter 11 that is input via the auxiliary start circuit ST are converted into AC power and output via the output filter OF. The inverter 12 which inputs into the high pressure discharge lamp DL, and the control part 2 which respectively controls the DC-DC converter 11 and the inverter 12 are provided. That is, when the output of the DC-DC converter 11 is input to the high-pressure discharge lamp DL via the inverter 12, the high-pressure discharge lamp DL is turned on.

  The input filter IF has a normal mode choke (inductor) connected between the output terminal on the high voltage side of the DC power supply E and the DC-DC converter 11, and one end thereof is connected to one end of the normal mode choke. The LC low-pass filter is composed of two across-the-line capacitors whose other end is connected to the ground. One of the above across-the-line capacitors (right side in FIG. 2) is an electrolytic capacitor with a relatively high capacitance, so that the instantaneous fluctuation of the input voltage Vin is compared for both the decrease width and the increase width. Can be kept small.

  The DC-DC converter 11 includes a transformer T0 having a primary winding with an input voltage Vin input to one end thereof, and a switching element Q0 composed of an NMOS connected between the other end of the primary winding of the transformer T0 and the ground. A diode D0 having a cathode connected to one end of the secondary winding of the transformer T0, an output capacitor having one end connected to the anode of the diode D0 and the other end connected to the ground together with the other end of the secondary winding of the transformer T0 C0 and a well-known flyback converter that uses the voltage Vdc across the output capacitor C0 as an output voltage. That is, when the switching element Q0 is periodically turned on / off, the input voltage Vin from the DC power source E is converted into an output voltage Vdc corresponding to the on-duty of the switching element Q0 and output. As the diode D0, a diode called a fast recovery diode (FRD) having a relatively short reverse recovery time is used.

  Further, the present embodiment includes a drive unit DR that drives the switching element Q0 of the DC-DC converter 11 on and off according to the control of the control unit 2. Specifically, the drive unit DR receives the rectangular-wave drive signal HF from the control unit 2, and turns on the switching element Q0 during a period in which the signal level of the drive signal HF is H level. The switching element Q0 is driven on and off so that the switching element Q0 is turned off during the period when the level is L level. Since such a driving unit DR can be realized by a known electronic circuit, detailed illustration and description thereof are omitted.

  The inverter 12 includes a full bridge circuit in which two series circuits of two switching elements Q1 to Q4 are connected in parallel between the output terminals of the DC-DC converter 11. That is, the control unit 2 controls each switching element Q1 so that the switching elements Q1 to Q4 positioned diagonally to each other are simultaneously turned on and at least one of the switching elements Q1 to Q4 connected in series to each other is turned off. By periodically turning on and off Q4, the output voltage Vd of the DC-DC converter 11 is converted into a rectangular wave AC voltage and output. In order to prevent the switching elements Q1 to Q4 connected in series with each other from being simultaneously turned on and the output terminals of the DC-DC converter 11 from being short-circuited, one set of switching elements Q1 and Q4 located diagonally to each other. A period (dead time) in which all the switching elements Q1 to Q4 are turned off is provided between the period in which the switching elements Q2 and Q3 are turned on. As the switching elements Q1 to Q4 of the inverter 12, for example, IGBTs, MOSFETs, or bipolar transistors can be used.

  In addition, the present embodiment includes a starting unit 13 that generates a high voltage pulse for starting the high-pressure discharge lamp DL, and a starting power source unit 14 that generates a power source for the starting unit 13.

  The starting power supply unit 14 rectifies and boosts the voltage induced in the secondary winding of the transformer T0 of the DC-DC converter 11 and inputs the voltage to the starting unit 13. Specifically, for example, the well-known Cockcroft-Walton It can be configured with a circuit.

  The starting unit 13 includes a transformer T1 in which a secondary winding is inserted in a conductive path from the inverter 12 to the high-pressure discharge lamp DL, a spark gap SG and a capacitor C1 connected between both ends of the primary winding of the transformer T1. The connection point between the primary winding of the transformer T1 and the spark gap SG is connected to the starting power supply unit 14, and the connection point between the spark gap SG and the capacitor C1 is connected to the ground. That is, immediately after the power is turned on, the capacitor C1 of the starter 13 is charged by the output of the starter power supply 14. When the voltage across the capacitor C1 rises sufficiently and dielectric breakdown occurs in the spark gap SG, an induced voltage is generated in the secondary winding due to the discharge current of the capacitor C1 that flows rapidly in the primary winding in the transformer T1. The high-voltage discharge lamp DL starts lighting (that is, starts) by starting discharge in the high-pressure discharge lamp DL by a high voltage pulse generated by superimposing the induced voltage on the output voltage Vdc of the DC-DC converter 11. .

  The start-up auxiliary circuit ST is a DC-DC converter immediately after the start of lighting of the high-pressure discharge lamp DL (that is, the start of discharge in the high-pressure discharge lamp DL). 11 is a circuit that secures an input voltage to the inverter 12 so that the high-pressure discharge lamp DL does not disappear during a period of about 100 μs in which the output voltage Vdc of 11 temporarily decreases. Since such a start assist circuit ST can be realized by a known technique, detailed illustration and description thereof will be omitted.

  The control unit 2 monitors the output voltage Vdc and the output current of the DC-DC converter 11, and controls the drive unit DR by feedback control so that the output power of the DC-DC converter 11 is set to a predetermined target power. The control unit 2 as described above can be realized by a known technique using an integrated circuit in which a digital circuit, an A / D conversion circuit, and a D / A conversion circuit are integrated.

  Furthermore, the present embodiment monitors the voltage at each predetermined location of the circuit (hereinafter referred to as “target voltage”) and stops the drive unit DR when the target voltage exceeds a predetermined threshold. The four comparison units 31 to 34 are provided. Each of the comparison units 31 to 34 is composed of a series circuit of two resistors and divides the target voltage, a capacitor that smoothes the voltage divided by the voltage dividing circuit, and both ends of the capacitor A voltage is input to the non-inverting input terminal, and the inverting input terminal includes a converter to which a reference voltage for each of the comparison units 31 to 34 is input. An output terminal of the comparator is used as an output terminal.

  As a method for reflecting the outputs of the comparison units 31 to 34 in the operation of the drive unit DR, for example, as shown in FIG. 2, the outputs of the comparison units 31 to 34 (second comparison unit 32 in the figure) are at the H level. A method of connecting a switching element (an NPN type bipolar transistor in the figure) that is turned on only during a period between the signal path of the drive signal HF and the ground is conceivable. In the above method, the switching element Q0 of the DC-DC converter 11 is in the OFF state because the input to the driving section DR is fixed to the L level by turning off the switching element during the period when the outputs of the comparison units 31 to 34 are at the H level. Maintained. Furthermore, if a switching element similar to the above is also provided in the signal path from the control unit 2 to the inverter 12, the inverter 12 is stopped when the DC-DC converter 11 is stopped (that is, each switching element Q1 of the inverter 12). It is also possible to keep Q4 in the OFF state.

  Each of the first comparison unit 31 and the second comparison unit 32 uses the input voltage Vin as a target voltage, and the second comparison unit 32 stops the drive unit DR (that is, the reference voltage Vr2 in the second comparison unit 32). Is divided by the voltage dividing ratio Rt2 of the voltage dividing circuit, hereinafter referred to as “second threshold value”.) Vt1 is a threshold value (that is, the first comparing unit 31) at which the first comparing unit 31 stops the driving unit DR. A voltage obtained by dividing the reference voltage Vr1 at 31 by the voltage dividing ratio Rt1 of the voltage dividing circuit (hereinafter referred to as “first threshold value”) is set higher than Vr1 / Rt1.

  In the example of FIG. 1, the output of the first comparison unit 31 is input to the control unit 2, and the control unit 2 outputs the drive signal HF to the L level during the period when the input from the first comparison unit 31 is at the H level. The control unit 2 is interposed between the first comparison unit 31 and the drive unit DR such that the drive unit DR is stopped by maintaining the level. For this reason, with respect to the first comparison unit 31, a time lag occurs due to A / D conversion and D / A conversion in the clock of the control unit 2 and the input / output of the control unit 2. The time until the change of the output S1 is reflected in the operation of the drive unit DR is long.

  Here, in any of the comparison units 31 to 34, as the voltage dividing ratio of the voltage dividing circuit, the resistance value of the resistor on the high voltage side of the voltage dividing circuit, and the capacitance of the capacitor are smaller, the comparing unit becomes higher after the target voltage reaches the threshold value. The time required until the outputs S1 and S2 of the output signals 31 and 32 change (that is, become H level) is shortened, that is, the response is accelerated.

  With regard to the first comparison unit 31 and the second comparison unit 32, when at least the input voltage Vin increases stepwise from 0V to a voltage higher than the second threshold value Vt2, the output S1 of the first comparison unit 31 is used. Circuit constants such as the resistance value of each resistor of the voltage dividing circuit, the capacitance of the capacitor, and the reference voltage so that the driving unit DR is stopped by the output S2 of the second comparison unit 32 faster than the driving unit DR is stopped. Are determined respectively.

  Thus, as shown in FIG. 3, when a surge occurs in which the input voltage Vin rises from the normal value Vn to the peak value Vp higher than the second threshold value Vt in a relatively short time, the capacitor in the first comparison unit 31 The voltage Vc1 / Rt1 obtained by dividing the voltage at both ends of Vc1 by the voltage dividing ratio Rt1 (= Vr1 / Vt1) of the voltage dividing circuit reaches the first threshold value Vt1 (that is, the voltage Vc1 across the capacitor is the first reference voltage Vr1 = Rt1 × Vt1). Voltage Vc2 obtained by dividing the voltage Vc2 across the capacitor in the second comparator 32 by the voltage dividing ratio Rt2 (= Vr2 / Vt2) from the timing t1 when the output S1 of the first comparator 31 changes. / Rt2 reaches the second threshold value Vt2 (that is, the voltage Vc2 across the capacitor reaches the second reference voltage Vr2 = Rt2 × Vt2), and the output S of the second comparison unit 32 Timing t2 when 2 changes is first.

  When an overvoltage state occurs in which the peak value Vp is equal to or greater than the first threshold value Vt1 and less than the second threshold value Vt2 and the input voltage Vin exceeds the first threshold value Vt1, a second is generated. The output S1 of the first comparison unit 31 changes without the output S2 of the comparison unit 32 changing.

  That is, in the case of an overvoltage state where the input voltage Vin is slightly high for a long time, the electrical stress is suppressed by the operation of the first comparison unit 31, and in the case of a surge in which the input voltage Vin increases rapidly, the second comparison is performed. Electrical stress can be suppressed by the operation of the unit 32.

  The third comparison unit 33 uses the voltage across the switching element Q0 of the DC-DC converter 11 (drain-source voltage) as a target voltage. That is, when a voltage equal to or higher than the third threshold obtained by dividing the reference voltage in the third comparison unit 33 by the voltage dividing ratio of the voltage dividing circuit is applied to the switching element Q0, the driving unit DR is operated by the operation of the third comparison unit 33. Stopped.

  Further, the fourth comparison unit 34 uses the output voltage Vdc of the DC-DC converter 11 as a target voltage. That is, the output voltage Vdc of the DC-DC converter 11 rises so rapidly that the feedback control by the control unit 2 cannot follow due to, for example, the extinction of the high pressure discharge lamp DL, and the reference voltage in the fourth comparison unit 34 is divided. When the output voltage Vdc exceeds the fourth threshold value divided by the circuit voltage division ratio, the driving unit DR is stopped by the operation of the fourth comparison unit 34, thereby protecting each circuit component from overvoltage.

  By the way, when the output of the inverter 12 is inverted, the output power to the high-pressure discharge lamp DL is temporarily reduced, so that the turn-off easily occurs. Therefore, in order to prevent such disappearance, the output voltage Vdc of the DC-DC converter 11 is increased by temporarily increasing the on-duty of the switching element Q0 in the DC-DC converter 11 when the output of the inverter 12 is inverted. Control may be performed. In such a case, the output voltage Vdc at the time of inversion of the output of the inverter 12 is based on a period during which the output voltage Vdc is temporarily increased. The third threshold value and the fourth threshold value are determined so that the comparison unit 33 and the fourth comparison unit 34 do not stop the drive unit DR.

  Here, in this embodiment, since the both-ends voltage of the switching element Q0 and the output voltage Vdc of the DC-DC converter 11 are also input to the control unit 2, they are performed by the third comparison unit 33 and the fourth comparison unit 34. Such a stop when the voltage across the switching element Q0 or the output voltage Vdc of the DC-DC converter 11 rises can be realized by the control unit 2 alone. However, the provision of the third comparison unit 33 and the fourth comparison unit 34 speeds up the response by an amount that does not cause a time lag due to A / D conversion or the like compared with the case where the above operation is realized only by the control unit 2. There is an advantage that the stress can be further suppressed.

  Each circuit component constituting the power supply device as described above is mounted on a printed wiring board PB as shown in FIG. 4, for example, and this printed wiring board PB is housed in the case 4. FIG. 4 shows an input connector CN1 and an electric wire PC1 that electrically connect the printed wiring board PB and the DC power source E, and an output connector CN2 and an electric wire PC2 that electrically connect the printed wiring board PB and the starting circuit 13. Is shown. The case 4 will be described in detail with reference to FIG. 4. The case 4 includes a body 41 having an accommodation recess 40 in which the printed wiring board PB is accommodated, and a cover 42 that is coupled to the body 41 and closes the accommodation recess 40. It consists of. The cover 42 is provided with three screwing portions 42a each provided with a through hole through which a screw is inserted and fixed with a screw passing through the through hole. The body 41 and the cover 42 are coupled to each other by attaching each screwing portion 42a to a mounting surface (not shown) on which the body 41 is installed so that the body 41 is between the cover 42 and the mounting surface. It may be carried out by being sandwiched between them, or may be realized by using known means such as fitting. If the material and structure of the case 4 are appropriately selected, it is possible to ensure the heat dissipation and waterproofness of each circuit component mounted on the printed wiring board PB. Since the case 4 and the connectors CN1 and CN2 as described above can be realized by a well-known technique, detailed illustration and description are omitted.

  The electrical light source is not limited to the high-pressure discharge lamp DL, and for example, a light emitting diode LED may be used as shown in FIG. In this case, all of the inverter 12, the starter 13, and the starter power supply 14 can be omitted.

  Further, the present invention can be applied even when another known switching power source such as a forward converter is used instead of the DC-DC converter 11 including the flyback converter as described above.

  Further, as the DC power supply E, a known DC power supply circuit such as a boost converter or a buck converter may be used instead of the battery. In this case, as the power supply of the DC power supply circuit, for example, an AC power supply that is full-wave rectified by a diode bridge can be used.

  Further, instead of directly reflecting the output S2 of the second comparison unit 32 in the operation of the driving unit DR as described above, during the period in which the voltage Vc2 across the capacitor exceeds the reference voltage Vr2 in the second comparison unit 32. It is good also as a structure by which the charging current to the capacitor | condenser of the 1st comparison part 31 is increased temporarily. Even in this case, when a surge occurs such that the output S2 of the second comparison unit 32 changes before the output S1 of the first comparison unit 31, the operation of the second comparison unit 32 causes the first comparison unit to operate. The time until the output of the output 31 becomes the H level is shortened, so that electrical stress is suppressed. Specifically, for example, as shown in FIG. 6, a series circuit of a switching element Qs and a resistor Rs that are turned on only during a period in which the voltage Vc2 across the capacitor exceeds the reference voltage Vr2 in the second comparison unit 32. The first comparison unit 31 is connected in parallel to the resistance on the high voltage side of the voltage dividing circuit. That is, during the period in which the voltage Vc2 across the capacitor exceeds the reference voltage Vr2 in the second comparison unit 32, the charging current to the capacitor in the first comparison unit 31 temporarily increases, and the switching element Qs And the resistor Rs constitute a current increasing means. In the example of FIG. 6, the voltage dividing ratio Rt1 in the first comparison unit 31 increases during the period when the switching element Qs is on, and as a result, the first threshold value Vt1 decreases. Furthermore, in the example of FIG. 6, the comparator of the second comparison unit 32 inverts the output by reversing the input of the non-inverting input terminal and the inverting input terminal with respect to the example of FIG. A PNP type bipolar transistor is used. The time changes of the input voltage Vin, the voltage Vc1 across the capacitor in the first comparison unit 31 and the output S2 of the second comparison unit 32 are as shown in FIG. When the second comparison unit 32 is not provided as shown by the thin line b, the output S1 of the first comparison unit 31 changes at a relatively late timing tb, whereas the output S2 of the second comparison unit 32 When the charging current of the capacitor in the first comparison unit 31 is increased as indicated by the thick line a after the change, the output S1 of the first comparison unit 31 changes at a timing ta earlier than the above.

2 Controller 11 DC-DC converter (switching converter)
31 1st comparison part 32 2nd comparison part 33 3rd comparison part 34 4th comparison part DL High pressure discharge lamp (electrical light source)
DR drive unit LED light emitting diode (electrical light source)
Q0 switching element Qs switching element (part of current increasing means)
Rs resistance (part of current increasing means)

Claims (5)

A switching converter that has at least one switching element and converts and outputs input power from a DC power supply;
A drive unit for driving each switching element of the switching converter;
A control unit for controlling the driving unit;
A first comparison unit that compares an input voltage from the DC power source to the switching converter with a predetermined first threshold value and stops driving each switching element in the switching converter when the input voltage exceeds the first threshold value; ,
The input voltage from the DC power source to the switching converter is compared with a predetermined second threshold value that is higher than the first threshold value, and each switching element in the switching converter is driven when the input voltage exceeds the second threshold value. A second comparison unit for stopping,
Each of the first comparison unit and the second comparison unit includes a voltage dividing circuit that divides the input voltage, a capacitor that smoothes the voltage divided by the voltage dividing circuit, and a voltage across the capacitor. A comparator that generates an output according to the comparison result compared with a predetermined reference voltage;
In the first comparison unit, the reference voltage is a value obtained by multiplying the first threshold value by a voltage dividing ratio of the voltage dividing circuit. In the second comparing unit, the reference voltage is set to the second threshold value of the voltage dividing circuit. A value multiplied by the partial pressure ratio,
At least when the input voltage changes stepwise from 0V to a voltage higher than the second threshold, the stop by the second comparator is performed before the stop by the first comparator. The power supply apparatus is characterized in that each circuit constant is determined in each of the first comparison unit and the second comparison unit. A switching converter that has at least one switching element and converts and outputs input power from a DC power supply;
A drive unit for driving each switching element of the switching converter;
A control unit for controlling the driving unit;
A first comparison unit that compares an input voltage from the DC power source to the switching converter with a predetermined first threshold and generates an output according to the comparison result;
The control unit controls the driving unit to stop driving each switching element in the switching converter when an output indicating that the input voltage exceeds the first threshold is input from the first comparison unit. To do,
A second comparison unit that compares an input voltage from the DC power source to the switching converter with a predetermined second threshold value that is higher than the first threshold value;
Each of the first comparison unit and the second comparison unit includes a voltage dividing circuit that divides the input voltage, a capacitor that smoothes the voltage divided by the voltage dividing circuit, and a voltage across the capacitor. A comparator that generates an output according to the comparison result compared with a predetermined reference voltage;
In the first comparison unit, the reference voltage is a value obtained by multiplying the first threshold value by a voltage dividing ratio of the voltage dividing circuit. In the second comparing unit, the reference voltage is set to the second threshold value of the voltage dividing circuit. A value multiplied by the partial pressure ratio,
When at least the input voltage changes stepwise from 0V to a voltage higher than the second threshold, the output of the comparator is changed in the second comparison unit before the output of the comparator is changed in the first comparison unit. Each circuit constant is determined in each of the first comparison unit and the second comparison unit so that the output changes.
The second comparison unit includes a current increasing unit that temporarily increases a charging current of the capacitor in the first comparison unit during a period in which a voltage across the capacitor exceeds the reference voltage. Power supply.   A third comparison for comparing the voltage across the switching elements of any one of the switching converters with a predetermined third threshold and stopping the driving of each switching element in the switching converter when the voltage across the terminals exceeds the third threshold. The power supply device according to claim 1, further comprising a unit.   A fourth comparison unit that compares the effective value of the output voltage of the switching converter with a predetermined fourth threshold value and stops driving of each switching element in the switching converter when the effective value exceeds the fourth threshold value. The power supply device according to claim 1, wherein the power supply device is a power supply device.   An illuminating device comprising: the power supply device according to claim 1; and an electric light source that is turned on by output power of the switching converter.

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