AU2017201929A1 - Lighting apparatus - Google Patents

Abstract

There is provided a lighting apparatus that can surely exhibit protection functions while avoiding a malfunction of the protection functions. A lighting apparatus according to an embodiment includes a power conversion circuit configured to supply electric power to an illumination load connected to an output and a safety circuit configured to detect an abnormality of the illumination load and a thermal abnormality and stop the conversion circuit on the basis of at least one data of an output voltage, which is a voltage of the output of the power conversion circuit, and an output current, which is an electric current flowing to the illumination load. The safety circuit stops the power conversion circuit earlier when the safety circuit detects the abnormality of the illumination load than when the safety circuit detects the thermal abnormality. 8864139_1 (GHMatters) P105559.AU ACQUIRE DATA OF DETECTION VOLTAGE Vdet AND DETECTION -S1 CURRENT Idet1 CALCULATE OUTPUT POWER S2 CALCULATION VALUE Pcal Vd et -! Vov Yes S4 Idet1 I=loc?-, 71 No OUTPUT, LATCH Idet22-!Ifit Yes S Tflt ELAINTERRUPT No OUTPUT, LATCH Tflt2 ELAPSES? No Yes S S9 RELEASE LATCH Pcal= Povr Yes and Tovr ELAPSES? INTERRUPT S 10 :4No OUTPUT, Fl G. 3

Description

LIGHTING APPARATUS

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2016-187619, filed on September 26, 2016; the entire contents of which are incorporated herein by reference

FIELD

An embodiment of the invention relates to a lighting apparatus.

BACKGROUND

Various protection functions are incorporated in a lighting apparatus that lights a variety of luminaires including an LED luminaire. The respective protection functions need to operate to surely protect the lighting apparatus when a deficiency occurs.

The lighting apparatus is sometimes protected from, for example, an overvoltage and an overcurrent due to an abnormality of a luminaire connected to an output. However, for example, in the case of a lighting apparatus in which an output current and output power can be set later, depending on the set output current and output power, it is likely that output power of the lighting apparatus is exceeded even within a protection region of an overvoltage and an overcurrent.

If normal operation is performed, when the protection functions of the lighting apparatus work, the lighting apparatus stops and illumination goes out. Therefore, it is also necessary to reduce such a malfunction of the protection functions.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a block diagram illustrating a lighting apparatus according to an embodiment; FIG. 2 is a diagram illustrating operation ranges of protection functions of the lighting apparatus of the embodiment; and FIG. 3 is an example of a flowchart for describing the operation of the lighting apparatus of the embodiment.

DETAILED DESCRIPTION

In general, according to one embodiment, there is provided a lighting apparatus including: a power conversion circuit configured to supply electric power to an illumination load connected to an output; and a safety circuit configured to detect an abnormality of the illumination load and a thermal abnormality and stop the conversion circuit on the basis of at least one data of an output voltage, which is a voltage of the output of the power conversion circuit, and an output current, which is an electric current flowing to the illumination load. The safety circuit stops the power conversion circuit earlier when the safety circuit detects the abnormality of the illumination load than when the safety circuit detects the thermal abnormality.

An embodiment of the invention is described below with reference to the drawings.

Note that the drawings are schematic or conceptual. Relations between thicknesses and widths of portions, ratios of the sizes among the portions, and the like are not always the same as real ones. Even if the same portions are shown, dimensions and ratios of the portions are sometimes shown different depending on the drawings.

Note that, in the specification and the drawings, components same as the components already shown in the drawings and described are denoted by the same reference numerals and signs and detailed description of the components is omitted as appropriate. FIG. 1 is a block diagram illustrating a lighting apparatus according to the embodiment.

As shown in FIG. 1, a lighting apparatus 10 of the embodiment includes a power converting section 20, a control circuit 30, and a safety circuit 40. The lighting apparatus 10 includes AC terminals 11a and 11b and output terminals 11c and 11 d. The lighting apparatus 10 is connected to an AC power supply 1 via the AC terminals 11a and 11b. The AC power supply 1 is, for example, a commercial power supply. The lighting apparatus 10 is connected to an illumination unit 2 via the output terminals 11c and 11 d. The illumination unit 2 includes a light-emitting element 2a. A plurality of light-emitting elements 2a may be connected in series. The illumination unit 2 includes connection terminals 3a and 3b. The connection terminals 3a and 3b are respectively connected to the output terminals 11c and 11 d of the lighting apparatus 10.

The lighting apparatus 10 includes a dimming signal terminal 11e. A dimming signal is input to the lighting apparatus 10 via the dimming signal terminal 11 e. The input dimming signal is an illumination control signal such as a DALI (Digital Addressable Lighting Interface).

The lighting apparatus 10 receives supply of AC power from the AC power supply 1 and lights the illumination unit 2 at brightness or the like set by the dimming signal.

The lighting apparatus 10 changes a resistance value of a current detector 122 described below to thereby set an electric current supplied to the illumination unit 2. That is, illumination units having different power capacities can be connected to the lighting apparatus 10 and lit within a range of an output power capacity of the lighting apparatus 10.

The power converting section 20 includes a rush-current prevention circuit 22, a rectifying and smoothing circuit 24, and a DC-DC converter 26.

The rush-current prevention circuit 22 is connected between the AC terminal 11a and the rectifying and smoothing circuit 24. The rush-current prevention circuit 22 suppresses a rush current flowing into the rectifying and smoothing circuit 24 at a post stage when a power supply is turned on.

The rectifying and smoothing circuit 24 is connected between the rush-current prevention circuit 22 and the DC-DC converter 26. The rectifying and smoothing circuit 24 includes a rectifier circuit and a smoothing circuit. The smoothing circuit may be an active smoothing filter. The rectifying and smoothing circuit 24 rectifies and smoothes an AC voltage to convert the AC voltage into a DC voltage and outputs the DC voltage.

The DC-DC converter 26 is connected between the rectifying and smoothing circuit 24 and the output terminals 11c and 11 d. The DC-DC converter 26 converts a DC voltage including a pulsating flow output from the rectifying and smoothing circuit 24 into a constant voltage or a constant current and supplies the DC voltage to a load. The DC-DC converter 26 sets electric power corresponding to the dimming signal, supplies the electric power to the load, and controls, for example, brightness of the illumination unit 2, which is the load.

Although not shown in the figure, the DC-DC converter 26 includes, for example, a switching power supply circuit of a chopper type. The switching power supply circuit is, for example, a chopper of a falling voltage type. A type of the switching power supply circuit is not limited to the falling voltage type and may be a rising voltage type, a rising-falling voltage type, and the like. The type of the switching power supply circuit can be optionally set according to input and output voltages, output power, and the like.

The DC-DC converter 26 includes a voltage detector 121 and the current detector 122. The voltage detector 121 is connected between the output terminals 11c and 11 d. The voltage detector 121 is, for example, a resistance voltage divider. The voltage detector 121 includes resistors 121a and 121b connected in series. An output voltage of the voltage detector 121 is output from a connection node of the resistors 121a and 121b. That is, the voltage detector 121 detects an output voltage of the lighting apparatus 10 and outputs a voltage proportional to the output voltage as a detection voltage Vdet. The detection voltage Vdet is input to the safety circuit 40.

The current detector 122 is connected in series to an output line of the DC-DC converter 26. The current detector 122 is, for example, a resistor. One end of the current detector 122 is grounded on the inside of the DC-DC converter 26. The other end of the current detector 122 is connected to the output terminal 11 d.

The current detector 122 detects an electric current flowing to the output line of the DC-DC converter 26, converts the electric current into a voltage value, and outputs the voltage value. When the illumination unit 2 is connected to the output, the current detector 122 detects an electric current flowing to the illumination unit 2 and outputs the electric current as a detection current Idetl having a dimension of the voltage value. The detection current Idetl is input to each of the control circuit 30 and the safety circuit 40.

The control circuit 30 includes a dimming control circuit 131, a PWM circuit 132, a current control amplifier 133, and a reference power supply 134. A dimming signal is input to the dimming control circuit 131 via the dimming signal terminal 11 e. The dimming control circuit 131 converts the input dimming signal into, for example, a dimming PWM signal and outputs the dimming PWM signal.

The PWM circuit 132 is connected to an output of each of the dimming control circuit 131 and the current control amplifier 133. An output of the PWM circuit 132 is supplied to the power converting section 20. When the power converting section 20 includes a power factor improvement circuit, the output of the PWM circuit 132 is supplied to each of the power factor improvement circuit and the DC-DC converter 26.

An output of the current detector 122 is connected to one input of the current control amplifier 133. The reference power supply 134 is connected to the other input. The current control amplifier 133 amplifies an error between the detection current Idetl output from the current detector 122 and a value Iref of a reference power supply and outputs the error.

The PWM circuit 132 generates a driving signal according to the output of the current control amplifier 133. When the detection current Idetl is larger than the value Iref of the reference power supply, a duty ratio of the driving signal is small. When the detection current Idetl is smaller than the value Iref of the reference power supply, the duty ratio of the driving signal is large.

The DC-DC converter 26 is, for example, a falling voltage type chopper. An output voltage and an output current of the DC-DC converter 26 are set according to a duty ratio of a switching element. The DC-DC converter 26 operates such that the switching element switches according to the duty ratio of the driving signal output by the PWM circuit 132 and the detection current Idetl is equal to the value Iref of the reference power supply.

The PWM circuit 132 repeats operation and non-operation according to the dimming PWM signal output by the dimming control circuit 131. When the PWM circuit 132 operates, electric power is supplied to the output. When the PWM circuit 132 does not operate, electric power is not supplied to the output. Brightness during lighting of the illumination unit 2 changes according to a duty of the electric power supplied to the output. The dimming PWM signal is set according to a dimming signal. Therefore, the illumination unit 2 is dimmed according to the dimming signal.

The safety circuit 40 is connected to an output of each of the voltage detector 121 and the current detector 122. The detection voltage Vdet and the detection current Idetl are input to the safety circuit 40.

The safety circuit 40 includes an overvoltage detecting section 141 that performs overvoltage detection serving as abnormality detection of an illumination load, an overcurrent detecting section 142 that performs overcurrent detection serving as thermal abnormality detection, a power calculating section 143, an overpower detecting section 144, and an abnormal-current detecting section 145. Outputs of the overvoltage detecting section 141, the overcurrent detecting section 142, the overpower detecting section 144, and the abnormal-current detecting section 145 are connected to an AND circuit 146. The AND circuit 146 outputs a stop signal HLT when the output of any one of the overvoltage detecting section 141, the overcurrent detecting section 142, the overpower detecting section 144, and the abnormal-current detecting section 145 becomes active.

The overvoltage detecting section 141 has an overvoltage threshold Vov concerning the detection voltage Vdet. The voltage detecting section 141 receives an input of the detection voltage Vdet output from the voltage detector 121. The overvoltage detecting section 141 compares the detection voltage Vdet and the overvoltage threshold Vov. When the detection voltage Vdet exceeds the overvoltage threshold Vov, the safety circuit 40 supplies the stop signal HLT to the control circuit 30.

The overcurrent detecting section 142 has an overcurrent threshold loc concerning the detection current Idetl. The overcurrent detecting section 142 receives an input of the detection current Idetl output from the current detector 122. The overcurrent detecting section 142 compares the detection current Idetl and the overcurrent threshold loc. When the detection current Idetl exceeds the overcurrent threshold loc, the safety circuit 40 supplies the stop signal HLT to the control circuit 30. A period Tov or Toe after the detection value of each of the overvoltage detecting section 141 and the overcurrent detecting section 142 exceeds the threshold thereof until the stop signal HLT is supplied from the safety circuit 40 is favorably zero. When the period Tov or Toe is not zero, the period Tov or Toe is favorably as short as possible. The period Tov or Toe is at least sufficiently shorter than periods after other protection functions described below detect thresholds until the stop signal HLT is supplied.

The power calculating section 143 calculates detection power Peal, which is a product of the detection voltage Vdet and the detection current Idetl input to the power calculating section 143, and outputs the detection power Peal. An output of the power calculating section 143 is connected to the overpower detecting section 144. The overpower detecting section 144 has an overpower threshold Povr concerning the detection power Peal. When the detection power Peal exceeds the overpower threshold Povr, the safety circuit 40 supplies the stop signal HLT to the control circuit 30.

The safety circuit 40 favorably outputs the stop signal HLT when a state in which the detection power Peal exceeds the overpower threshold Povr continues for a preset period Tovr or more. The safety circuit 40 does not output the stop signal HLT when the state in which the detection power Peal exceeds the overpower threshold Povr continues for a period less than the period Tovr. As described above, the period Tovr is set to a long time compared with the period Tov or Toe.

The control circuit 30 receives the stop signal HLT and stops oscillating operation. Therefore, the lighting apparatus 10 stops the operation. The power supply to the illumination unit 2 is interrupted.

In the case described above, the stop signal HLT output by the safety circuit 40 is, for example, at a low level. When the AC power supply 1 of the lighting apparatus 10 is interrupted and the control circuit 30 and the safety circuit 40 are restarted by turning on the AC power supply 1 again to restart the lighting apparatus 10, a state of the low level of the stop signal HLT is released. Therefore, when the safety circuit 40 detects an excessively large output voltage or an excessively large output current, the safety circuit 40 can stop the operation of the lighting apparatus 10 and maintain a state of the stop.

The stop signal HLT sent by the safety circuit 40 may be a low-level one-shot signal having a preset pulse width. The control circuit 30 includes a latch circuit. The control circuit 30 receives an input of the low-level one-shot signal and stops oscillating operation. A state of the stopped oscillating operation is latched.

The safety circuit 40 is connected to the output of the current control amplifier 133 of the control circuit 30. The current control amplifier 133 supplies a current control signal Idet2 to the safety circuit 40. The safety circuit 40 has an abnormal current threshold Iflt concerning the current control signal Idet2. The abnormal current threshold Iflt is set to, for example, a voltage at which the output of the current control amplifier 133 is saturated.

The safety circuit 40 supplies the stop signal HLT to the control circuit 30 when a state in which the current control signal Idet2 exceeds the abnormal current threshold Iflt continues for a period Tfltl or more. The period Tfltl is set to a sufficiently long time compared with the period Tov or Toe.

In this case, for example, the stop signal HLT is at the low level. The state of the low level is maintained. The stop signal HLT in the state of the low level is inverted to a high level after a preset period Tflt2 elapses. The stop signal HLT is inverted to the high level, whereby the stop state of the control circuit 30 is released. The control circuit 30 resumes the operation.

That is, when a state in which the output of the current control amplifier 133 rises or falls to a saturation level continues, the safety circuit 40 recognizes that an abnormality is present in the current detection signal Idet2. The lighting apparatus 10 repeats the operation state and the stop state until the abnormal state is eliminated.

In the example described above, the light-emitting diode is used as the light-emitting element 2a in the lighting apparatus. An abnormal current can be detected using the current control amplifier. When the lighting apparatus outputs a constant voltage, in the same manner as described above, it is possible to perform abnormal voltage detection using the voltage control amplifier.

The safety circuit 40 may be a semiconductor device that operates according to steps of a computer program stored in a not-shown storage device such as a memory of a microcomputer, a microcontroller, or the like. When the safety circuit 40 is the microcomputer or the like, each of the overvoltage detecting section 141, the overcurrent detecting section 142, the power calculating section 143, the overpower detecting section 144, and the abnormal-current detecting section 145 of the safety device 40 may be executed as a part or all of steps, a part or all of which are included in the computer program.

The operation of the lighting apparatus of the embodiment is described. FIG. 2 is a diagram illustrating operation ranges of protection functions of the lighting apparatus of the embodiment.

In FIG. 2, an output current of the lighting apparatus 10 is plotted on the horizontal axis and an output voltage of the lighting apparatus 10 is plotted on the vertical axis. A range in which the lighting apparatus 10 can safely operate is shown as a normal operation region. A region other than the normal operation region is an operation stop region.

As shown in FIG. 2, the lighting apparatus 10 has a maximum voltage that can be output. When the output voltage of the lighting apparatus 10 exceeds the maximum voltage, an overvoltage protection function operates. For example, a threshold of the overvoltage protection function is set to, for example, 110% of the maximum output voltage of the lighting apparatus 10. When the output voltage of the lighting apparatus 10 exceeds the threshold of the overvoltage protection function, the lighting apparatus 10 stops the oscillating operation of the control circuit 30 to thereby stopping the operation. A state of the stop is a latch operation released when the control circuit 30 is restarted by, for example, turning on the power supply again.

The lighting apparatus 10 has a maximum current that can be output. When the output current of the lighting apparatus 10 exceeds the maximum current, an overcurrent protection function operates. For example, a threshold of the overcurrent protection function is set to, for example, 110% of the maximum current of the lighting apparatus 10. When the output current of the lighting apparatus 10 exceeds the threshold of the overcurrent protection function, the lighting apparatus 10 stops the oscillating operation of the control circuit 30 to thereby stop and latch the operation. For release of the latch operation, the control circuit 30 is restarted by, for example, turning on the power supply again.

The overvoltage protection function and the overcurrent protection function are provided for the purpose of protecting the lighting apparatus 10 from an abnormal state caused by an abnormality of the illumination unit 2 or the like connected to the outside of the lighting apparatus 10. Therefore, the overvoltage protection function and the overcurrent protection function operate to quickly interrupt the lighting apparatus 10 after detection of the abnormal state such that the lighting apparatus 10 can be more safely protected. A state of the protection is maintained. To release the protection state, the power supply needs to be turned on again.

The lighting apparatus 10 has maximum power that can be output. When electric power output by the lighting apparatus 10 exceeds the maximum power, an overpower protection function operates. A threshold of the maximum power is indicated by an alternate long and short dash line in FIG. 2. When the output voltage is the overvoltage threshold Vov and an output current that can be fed is represented as 11, the threshold Povr of the overpower protection function is VovxM. When the output current is the overcurrent threshold loc and an output voltage that can be output is represented as V1, the threshold Povr of the overpower protection function is V1 xloc. VovxM is substantially equal to V1 xloc. The alternate long and short dash line in FIG. 2 is a line indicating equal power that the lighting apparatus 10 can output.

The threshold Povr of the overpower protection function is set to, for example, 100% of the maximum power that the lighting apparatus 10 can output.

The lighting apparatus 10 interrupts the output when, after the output power exceeds the threshold Povr of the overpower protection function, a state of overpower is continued after the elapse of the preset period Tovr. The lighting apparatus 10 stops the oscillating operation of the control circuit 30 to thereby stop the operation and latches a state of the stop. For release of the latch operation, the control circuit 30 needs to be started again by, for example, turning on the power supply again.

The overpower protection function is provided in order to protect the lighting apparatus 10 when an illumination unit having power consumption larger than the maximum output power of the lighting apparatus 10 is connected to the output. When the lighting apparatus 10 outputs excessively large power, the lighting apparatus 10 itself or components on the inside generate heat.

Temperature could rise according to the elapse of time and exceed an allowable temperature. On the other hand, even if excessively large power is output for a short time, since a temperature rise is small, it is possible to keep the temperature within the allowable temperature.

Therefore, in the lighting apparatus 10 of the embodiment, the operation of the overpower protection function interrupts the output of the lighting apparatus 10 when an overpower state continues exceeding the predetermined period Tovr.

Consequently, it is possible to surely protect the lighting apparatus 10 during the overpower output while preventing a malfunction in which the lighting apparatus 10 stops operation in an instantaneous overpower state.

An abnormal current protection function operates when a state in which the output current is larger than a value set by the value Iref of the reference power supply continues. When the detection current Idetl outputted from the current detector 122 is larger than the value Iref of the reference power supply, the current control amplifier 133 outputs, for example, a high-level voltage. When the output current of the lighting apparatus 10 is in a normal range, the detection current Idetl returns to the normal range. For example, when some abnormality is present in the current detector 122 and, although the output current is flowing, a state in which the detection current Idetl corresponding to a current value of the output current is not output continues, the current control amplifier 133 continues to output a high-level control signal. When a level of the control signal exceeds the threshold Iflt and continues for a preset period Tfl71, the safety circuit 40 supplies the stop signal HLT to the control circuit 30.

The control circuit 30 receives the stop signal HLT and stops the oscillating operation. Therefore, the output to the lighting apparatus 10 is interrupted.

Further, after sending the stop signal HLT, when the preset period Tflt2 elapses, the safety circuit 40 supplies a restart signal to the control circuit 30. The control circuit 30 receives the restart signal, restarts, and supplies the output current to the load. Thereafter, when the detection current Idetl is not normally output, the safety circuit 40 supplies the stop signal HLT to the control circuit 30 again and stops the lighting apparatus 10. The lighting apparatus 10 repeats the operation described above. FIG. 3 is an example of a flowchart for describing the operation of the lighting apparatus of the embodiment.

As shown in FIG. 3, in step S1, the safety circuit 40 acquires respective data of the detection voltage Vdet and the detection current Idetl. The acquired data are temporarily stored in, for example, a register in the safety circuit 40.

In step S2, the safety circuit 40 calculates an output power calculation value Peal using the detection voltage Vdet and the detection current Idetl.

In step S3, the safety circuit 40 compares the detection voltage Vdet and the overvoltage threshold Vov. When the detection voltage Vdet is the overvoltage threshold Vov or more, the safety circuit 40 transitions the processing to step S4.

In step S4, the safety circuit 40 transmits the stop signal HLT to the control circuit 30. The control circuit 30 stops the oscillating operation according to the stop signal HLT. Therefore, the lighting apparatus 10 stops the operation and the output is interrupted.

When the detection voltage Vdet is lower than the overvoltage threshold Vov in step S3, the safety circuit 40 transitions the processing to the next step S5.

In step S5, the safety circuit 40 compares the current control signal Idet2 and the abnormal current threshold If It. When a state in which the current control signal Idet2 is the abnormal current threshold Iflt or more elapses the period Tfltl, the safety circuit 40 transitions the processing to step S6.

In step S6, the safety circuit 40 supplies the stop signal HLT to the control circuit 30.

In step S7, after sending the stop signal HLT, the safety circuit 40 determines whether the predetermined period Tflt2 elapses. The safety circuit 40 stays on standby until the period Tflt2 elapses. When the period Tflt2 elapses, the safety circuit 40 transitions the processing to step S8.

In step S8, the safety circuit 40 sends a stop release signal to the control circuit 30. The control circuit 30 receives the stop release signal, starts the oscillating operation, and restarts. Therefore, the lighting apparatus 10 restarts and supplies an electric current to the output.

When the current control signal Idet2 is lower than the abnormal current threshold Iflt in step S5, the safety circuit 40 transitions the processing to step S9.

In step S9, the safety circuit 40 compares the output power calculation value Peal and the output power threshold Povr. When the output power calculation value Peal is the output power threshold or more and the predetermined period Tovr elapses, the safety circuit 40 transitions the processing to step S10.

In step S10, the safety circuit 40 supplies the stop signal HLT to the control circuit 30. The control circuit 30 stops the oscillating operation according to the stop signal HLT and latches a state of the stop.

When the output power calculation value Peal is smaller than the overpower threshold Povr in step S9, the safety circuit 40 returns to the first step S1 and repeats the processing described above.

Note that the flowchart described above is an example and is not limited to the procedure described above. For example, after acquiring the data in step S1, the safety circuit 40 may perform the determination in step S3. Thereafter, the safety circuit 40 may perform the calculation of the output power calculation value Peal. After the determination of the output power in step S9, the safety circuit 40 may perform the determination of an abnormal current.

When performing the detection of an abnormal current (step S5), the safety circuit 40 may determine whether the output power is excessively large (step S9).

An effect of the lighting apparatus 10 of the embodiment is described.

Since the lighting apparatus 10 of the embodiment includes the safety circuit 40, the lighting apparatus 10 can perform the over power protection in addition to the overvoltage protection and the overcurrent protection. For example, in the case of a lighting apparatus that can change an output current supplied to a load by changing setting (a resistance value) of the current detector 122, an output power capacity is sometimes exceeded even if a voltage and an electric current of an output are within rated values of the lighting apparatus. More specifically, when the output power capacity of the lighting apparatus 10 is 100 W, both of a load of 100 V and 1 A and a load of 10 V and 10 A can be used.

For example, when a load of 15 V and 10 A is connected to the output, power consumption is 150 W. In such a case, when the overvoltage protection is set to 110 V and the overcurrent protection is set to 11 A, neither the overvoltage protection function nor the overcurrent protection function operates. This is a state in which the lighting apparatus 10 is outputting overpower. If such a state is left untouched, the lighting apparatus 10 falls into an overheated state, leading to a failure or the like soon. In the lighting apparatus 10 of the embodiment, for example, the overpower function operates at 110 W (110% of a rated output). Therefore, it is possible to protect the lighting apparatus 10 from a deficiency such as breakage.

When power consumption of the load is larger than the output power capacity of the lighting apparatus 10, the lighting apparatus 10 generates heat when excessively large output power is supplied. However, because of heat resistance and heat capacity of the lighting apparatus 10 and the components and the members configuring the lighting apparatus 10, the heat generation due to the power application needs certain degree of time until reaching heat generation that leads to breakage. For example, in FIG. 2, even if the overpower threshold is exceeded in a state of X marks, the lighting apparatus 10 does not stop and can continue the operation if the operation enters the normal operation region as indicated by an arrow within the period Tovr.

In the lighting apparatus 10 of the embodiment, for the operation of the overpower protection function, a period in which electric power is applied needs to continue for the predetermined period Tovr. With the period Tovr, for example, in the case of transient excessively large power, it is possible to stably continue safe operation without causing the overpower protection to unnecessarily operate.

In the lighting apparatus 10 of the embodiment, since the safety circuit 40 includes the abnormal current protection function, it is possible to protect the lighting apparatus 10 from breakage and the like caused by an excessively large current due to a deficiency and the like of the components on the inside of the lighting apparatus 10 besides problems due to the load connected to the outside.

The safety circuit 40 can detect a state in which the detection current Idetl does not rise to the value Iref of the reference power supply 134 because of a short-circuit or the like of the switching element in the DC-DC converter 26 or the current detector 122. In FIG. 2, although the lighting apparatus 10 is operating within the overcurrent threshold as indicated by triangle marks, when a value of the output current does not reach a specified value even if time elapses, the safety circuit 40 determines that there is a deficiency on the inside of the lighting apparatus 10. The operation of the lighting apparatus 10 is stopped. Since the operation of the lighting apparatus 10 is stopped, heat generation of the lighting apparatus 10 is suppressed.

In the lighting apparatus 10 of the embodiment, when the lighting apparatus 10 is determined as having an abnormal current and stopped by the abnormal current protection function, after the stop, when the period Tflt2 elapses, the lighting apparatus 10 restarts. When the restarted lighting apparatus 10 returns to the normal operation, the lighting apparatus 10 can continue the operation.

When the abnormal current protection function operates, the lighting apparatus 10 repeats the interruption and the restart, whereby the illumination unit 2, which is the load, flashes. According to the flashing of the illumination unit 2, a user can recognize that a deficiency occurs in the lighting apparatus 10 and can take accurate action such as power supply interruption.

Concerning the operation of the abnormal current protection function, by appropriately setting a duty cycle of the interruption and the restart, it is possible to suppress a temperature rise in a deficiency occurrence part or the like and realize safe protection. Note that, after a predetermined period elapses during the operation of the abnormal current protection function or after the repetition of the interruption and the restart is performed a predetermined number of times, the lighting apparatus 10 may be interrupted.

According to the embodiment described above, it is possible to realize the lighting apparatus that can surely exhibit the protection functions while avoiding a malfunction of the protection functions.

While certain embodiments have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.

In the claims which follow and in the preceding description of the invention, except where the context requires otherwise due to express language or necessary implication, the word “comprise” or variations such as “comprises” or “comprising” is used in an inclusive sense, i.e. to specify the presence of the stated features but not to preclude the presence or addition of further features in various embodiments of the invention.

It is to be understood that, if any prior art publication is referred to herein, such reference does not constitute an admission that the publication forms a part of the common general knowledge in the art, in Australia or any other country.

Claims (11)

1. THE CLAIMS DEFINING THE INVENTION ARE AS FOLLOWS:

   1. A lighting apparatus comprising: a power conversion circuit configured to supply electric power to an illumination load connected to an output; and a safety circuit configured to detect an abnormality of the illumination load and a thermal abnormality and stop the conversion circuit on the basis of at least one of an output voltage, which is a voltage of the output of the power conversion circuit, and an output current, which is an electric current flowing to the illumination load, the safety circuit stopping the power conversion circuit earlier when the safety circuit detects the abnormality of the illumination load than when the safety circuit detects the thermal abnormality.
2. 2. The apparatus according to claim 1, wherein, when output power, which is a product of the output voltage and the output current, exceeds a first threshold and continues for a first period, the safety circuit determines this as the thermal abnormality and stops the power conversion circuit.
3. 3. The apparatus according to claim 1, wherein, when the output current or the output voltage does not reach a set value and a period in which the output current or the output voltage does not reach the set value continues for a second period, the safety circuit determines this as the thermal abnormality and stops the power conversion circuit.
4. 4. The apparatus according to claim 2, wherein, when the output current or the output voltage does not reach a set value and a period in which the output current or the output voltage does not reach the set value continues for a second period, the safety circuit determines this as the thermal abnormality and stops the power conversion circuit.
5. 5. The apparatus according to claim 4, wherein the safety circuit maintains a state of the stop of the power conversion circuit after the first period elapses.
6. 6. The apparatus according to claim 4, wherein, when the safety circuit stops the power conversion circuit after elapse of the second period, the safety circuit starts the power conversion circuit again after elapse of a third period longer than the second period.
7. 7. The apparatus according to claim 4, wherein when a state in which the output voltage exceeds a second threshold continues for a fourth period or a state in which the output current exceeds a third threshold continues for a fifth period as an abnormality of the illumination load, the safety circuit stops the power conversion circuit and maintains a state of the stop, and the fourth period and the fifth period are shorter than the first period and the second period.
8. 8. The apparatus according to claim 7, wherein after comparing the output voltage and the second threshold, the safety circuit determines whether the second period elapses, and after determining whether the second period elapses, the safety circuit compares the output power and the first threshold.
9. 9. The apparatus according to claim 6, wherein, after the fourth period or the fifth period elapses, when the third period elapses, the safety circuit maintains a state of the stop of the power conversion circuit.
10. 10. The apparatus according to any one of claims 1 to 9, wherein loads having different power capacities can be connected to the output of the power conversion circuit.
11. 11. The apparatus according to any one of claims 1 to 10, wherein the safety circuit includes a microcomputer.