JP2011155747A - Power source device, and lighting fixture - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power source device in which a voltage across a capacitor for drive is secured even when performing operation according to a PWM signal, and to provide a lighting fixture. <P>SOLUTION: The power source device 1 includes a back converter composed of: a series circuit consisting of the first switching element Q1 and a diode D1, which is connected across the output terminals of a DC power source E; and a series circuit consisting of an inductor L1 and a capacitor C1, which is connected across both ends of the diode D1. A control circuit 2 switches on or switches off the first switching element Q1, using the capacitor Cs for drive as a power source. The second switching element Q2 which constitutes a charging path from a capacitor Cc for charge to the capacitor Cs for drive when switched on, is connected across both ends of the diode D1. The second switching element Q2 is switched on just before the start of an ON period in every ON period of ON-OFF drive periods of the first switching element Q1. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

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

  Conventionally, as shown in FIG. 14, a diode bridge DB as a DC power source that outputs DC power (pulsating power) by full-wave rectifying AC power input from an AC power source AC, and one end of the diode bridge DB. A first switching element Q1 composed of an N-channel MOSFET connected to the output terminal on the high voltage side of the first switching element Q1 and a diode bridge DB in series with the first switching element Q1 on the lower voltage side than the first switching element Q1. A diode D1 connected in the opposite direction to the output of the output, an output circuit including an inductor L1 that forms a loop with the diode D1, and a load connected thereto, and a control circuit 2 that drives the first switching element Q1 on and off. A power supply is provided.

  In the power supply device 1 of FIG. 14, the output circuit includes a series circuit of an inductor L1 and a boosting switching element Qb connected between both ends of the diode D1, and a booster connected in parallel to the booster switching element Qb. This is a so-called boost converter (boost chopper circuit) composed of a series circuit of a diode Db and a capacitor C1. That is, both ends of the capacitor C1 are connected to the load Z as output ends, and DC power is output to the load Z. Further, in the above case, the first switching element Q1, the diode D1, the inductor L1, and the capacitor C1 constitute a so-called buck converter (step-down chopper circuit). Then, the control circuit 2 controls the driving unit 2a for driving the first switching element Q1 on and off, and the driving unit 2a so as to keep the voltage across the capacitor C1 (that is, the output voltage of the power supply device 1) constant. And a feedback unit 2b for driving the switching element Qb on and off.

  In this type of power supply device 1, the diode D1 and the output circuit are interposed between the output terminal on the low voltage side of the diode bridge DB, which is a DC power supply, and the terminal on the low voltage side of the first switching element Q1. Therefore, in order for the driving unit 2a of the control circuit 2 to be a power source used for driving the first switching element Q1, one end is one end on the low voltage side of the first switching element Q1 (that is, the first switching element Q1 and the diode D1). A driving capacitor Cs connected between the two is provided. Furthermore, a charging capacitor Cc is provided as a charging power source that is connected to the other end of the driving capacitor Cs and is supplied with electric power from the diode bridge DB via the resistor Rc to charge the driving capacitor. In other words, during a period in which current flows through the loop of the diode D1 and the output circuit, the potential at one end on the low voltage side of the first switching element Q1 substantially matches the potential at the output end on the low voltage side of the diode bridge DB. The driving capacitor Cs is charged by the current supplied from the charging capacitor Cs through the charging diode Dc. At this time, the current for charging the driving capacitor Cs flows in the loop including the inductor L1.

  Further, in the example of FIG. 14, the control circuit 2 counts a predetermined charging time after the power is turned on, and during the charging time counting, the boosting switching element Qb is turned on by an output via the OR circuit OR1. Timer section 2c. That is, during the period when the boosting switching element Qb is turned on by the above operation, the driving capacitor Cs is charged by the current flowing through the inductor L1 and the boosting switching element Qb.

  However, when the driving capacitor is charged through the path through the inductor L1 as described above from the state where the driving capacitor Cs is not charged at all, for example, immediately after the power is turned on, the driving is performed by the action of the inductor L1. It can be considered that it takes time until the capacitor Cs for charging is sufficiently charged, and it is difficult to control the voltage across the driving capacitor Cs.

  On the other hand, Patent Document 1 is provided with a switch (not shown) for turning on and off a short circuit between both ends of the diode D1, and before the control circuit 2 starts on / off driving of the first switching element Q1, the charging capacitor Cc. A technique is also disclosed in which the above-described switch is turned on during a period in which the voltage at both ends is lower than a predetermined value. With this configuration, charging can be performed through a path that passes through the switch and not through the inductor L1, so that the voltage across the driving capacitor can be stabilized in a relatively short time.

Japanese Patent Laid-Open No. 2002-354783

  Here, consider a case where PWM control is performed. That is, the control circuit 2 performs an on-period operation in which the voltage across the capacitor C1 is kept constant by repeatedly turning on and off the first switching element Q1 according to the input PWM signal, and the first switching element Q1. One of the operations in the off period in which is maintained in the off state is performed. In this case, the output power increases as the ratio of the ON period in one cycle of operation increases (that is, the ON duty increases).

  Conventionally, the switch that short-circuits both ends of the diode D1 is a period in which the voltage across the charging capacitor Cc is lower than a predetermined value, that is, immediately after the power source is turned on (that is, immediately after the DC power source E starts to output DC power). It was only turned on. Therefore, when the PWM control as described above is performed, if the voltage across the driving capacitor Cs decreases during the off period, the first switching element Q1 may not be turned on at the start of the next on period. there were.

  The present invention has been made in view of the above reasons, and an object thereof is to provide a power supply device and a lighting fixture in which a voltage across a driving capacitor is ensured even when an operation according to a PWM signal is performed. There is to do.

  The invention of claim 1 is directed to a DC power source that outputs DC power, a first switching element having one end connected to the output end of the DC power source, and in series with the first switching element and to the output of the DC power source. A diode connected in the reverse direction, an output circuit including an inductor that forms a loop with the diode and connected to a load, a driving capacitor having one end connected between the first switching element and the diode, and a driving capacitor A charging power source that is connected to the other end of the diode and is supplied with electric power from a DC power source to charge the driving capacitor, a second switching element that turns on and off a short circuit between both ends of the diode, and an on / off drive of the second switching element And a control circuit for driving the first switching element on and off using a driving capacitor as a power source, In response to the applied PWM signal, an on period operation in which the first switching element is repeatedly turned on and off while the second switching element is maintained in an off state, and an off period in which the first switching element is maintained in an off state. Immediately before switching the operation from the off period to the on period, the driving capacitor is maintained by turning on the second switching element while maintaining the first switching element in the off state. A charging operation of charging the battery is performed.

  According to the present invention, since the charging operation is performed immediately before the ON period for each ON period, the voltage across the driving capacitor is reduced during the OFF period in the operation according to the PWM signal. In addition, since the voltage across the driving capacitor is secured by the charging operation, the first switching element can be turned on and off as the on-period starts.

  According to a second aspect of the invention, there is provided a PWM signal generation circuit for inputting a PWM signal to the control circuit according to the first aspect of the invention, and the PWM signal generation circuit has a signal level of a reset signal input from the outside at a predetermined level. A PWM signal for continuing the operation in the off period is input to the control circuit for a certain period.

  According to a third aspect of the present invention, in the first or second aspect of the present invention, the control circuit and the second switching element are integrated in one integrated circuit.

  According to the present invention, the number of components can be reduced and the size can be reduced as compared with the case where the second switching element is configured with components separate from the control circuit.

  According to a fourth aspect of the present invention, in any one of the first to third aspects of the present invention, a zero cross detecting means for detecting a zero cross of a current flowing through the inductor of the output circuit, and a current detecting means for detecting a current flowing through the inductor of the output circuit; The control circuit controls the first switching element to be on when the zero cross is detected by the zero cross detecting means during operation during the ON period, and the current detected by the current detecting means reaches a predetermined upper limit value. When the first switching element is turned off when the current reaches, the current detected by the current detection means does not reach the predetermined upper limit value even after a predetermined time has elapsed since the zero cross was detected by the zero cross detection means. A charging operation is started.

  According to a fifth aspect of the present invention, in any one of the first to fourth aspects, the output circuit has a capacitor connected between both ends of the diode as a series circuit with the inductor.

  According to the present invention, it is possible to output DC power using both ends of the capacitor as output ends.

  According to a sixth aspect of the present invention, in any of the first to fourth aspects of the present invention, the output circuit has two capacitors connected between both ends of the diode as a series circuit with the inductor, and the control circuit has the input The first operation mode in which the operation in the on period and the operation in the off period are performed according to the switching signal, and the second operation mode in which the second switching element and the first switching element are alternately turned on and off. It is possible to operate with

  According to the present invention, during the period in which the control circuit operates in the first operation mode, for example, DC power can be output using one end of the capacitor of the output circuit as an output end, and the control circuit can output the second operation mode. During the operation period, AC power can be output with both ends of the capacitor of the output circuit as output ends.

  A seventh aspect of the invention includes the power supply device according to any one of the first to sixth aspects, and an appliance main body that holds the power supply device, and an electric light source as a load by electric power output from the output circuit. It is made to light.

  According to the first aspect of the present invention, the control circuit performs an on period operation in which the first switching element is repeatedly turned on and off while maintaining the second switching element in an off state in accordance with the input PWM signal; One of the operations in the off period of maintaining one switching element in the off state is performed, and immediately before switching the operation from the off period to the on period, the first switching element is maintained in the off state while maintaining the first switching element in the off state. 2 Since the charging operation of charging the driving capacitor is performed by turning on the switching element, the charging operation is performed immediately before the ON period for each ON period. Even if the voltage across the driving capacitor drops during the off period, the voltage across the driving capacitor is reduced by the charging operation. Since the coercive, it is possible to on-off driving of the first switching element at the start of the ON period.

  According to the invention of claim 3, since the control circuit and the second switching element are integrated in one integrated circuit, compared with the case where the second switching element is constituted by a component separate from the control circuit, Miniaturization is possible by reducing the number of parts.

  According to the invention of claim 5, since the output circuit has the capacitor connected between both ends of the diode as a series circuit with the inductor, it is possible to output DC power using both ends of the capacitor as output ends.

  According to the invention of claim 6, the output circuit has two capacitors connected between both ends of the diode as a series circuit with the inductor, and the control circuit has an ON period according to the input switching signal. And the second operation mode in which the second switching element and the first switching element are alternately turned on / off are possible. In the period in which the control circuit operates in the first operation mode, for example, DC power can be output with one end of one of the capacitors of the output circuit as the output terminal, and in the period in which the control circuit operates in the second operation mode. AC power can be output using one end of the capacitor of the output circuit as an output end.

It is a circuit block diagram which shows Embodiment 1 of this invention. It is a block diagram which shows the principal part same as the above. It is explanatory drawing which shows the same operation | movement when the on-duty of a PWM signal is about 0.5, The signal level of PWM signal Vp, the signal level of delay signal Vpd, and the ON / OFF state of the 1st switching element Q1 The time change with the on-off state of the 2nd switching element Q2 is shown. It is explanatory drawing which shows the same operation | movement when the on-duty of a PWM signal is 1, and shows the time change with the on-off state of the 1st switching element Q1, and the on-off state of the 2nd switching element Q2. It is explanatory drawing which shows an example of operation | movement of the example of a change same as the above, and shows the time change with the signal level of PWM signal Vp, the ON / OFF state of the 1st switching element Q1, and the ON / OFF state of the 2nd switching element Q2. It is a circuit block diagram which shows another example of a change same as the above. It is a circuit block diagram which shows Embodiment 2 of this invention. It is a circuit block diagram which shows the principal part same as the above. It is explanatory drawing which shows an example of operation | movement same as the above, and is the signal level of the delay signal Vpd, the detection voltage Vd, the induced voltage ZCD, the on-off state of the 1st switching element Q1, and the on-off state of the 2nd switching element Q2. Shows time change. It is a circuit block diagram which shows Embodiment 3 of this invention. (A) (b) is explanatory drawing which shows the form of the connection of the electrical light source with respect to each same, (a) shows the state to which the discharge lamp La was connected as an electrical light source, (b) is an electrical light source. As shown, the LED array LED is connected. It is a disassembled perspective view which shows an example of the lighting fixture using the same as the above. It is a disassembled perspective view which shows another example of the lighting fixture using the same as the above. 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.

(Embodiment 1)
In the present embodiment, as shown in FIG. 1, DC power for lighting the light emitting diode array LED is output.

  More specifically, the power supply device 1 of the present embodiment includes a DC power supply E whose output terminal on the low voltage side is connected to the ground, and an N channel whose drain is connected to the output terminal on the high voltage side of the DC power supply E. A first switching element Q1 composed of a MOSFET of type, a diode D1 having a cathode connected to the source of the first switching element Q1 and an anode connected to the ground, and a connection point between the diode D1 and the first switching element Q1. By outputting an appropriate voltage to the inductor L1 having one end connected thereto, the capacitor C1 having one end connected to the other end of the inductor L1 and the other end connected to the ground, and the gate of the first switching element Q1, a first voltage is output. And a control circuit 2 for driving the switching element Q1 on and off. It is connected to the D. That is, the well-known buck converter is comprised by the 1st switching element Q1, the diode D1, the inductor L1, and the capacitor | condenser C1. Further, the inductor L1 and the capacitor C1 constitute an output circuit in the claims.

  The DC power supply E includes a diode bridge DB that performs full-wave rectification of AC power input from the AC power supply AC via a known low-pass filter LPF, and a known boost that converts a DC output of the diode bridge DB into a DC output of a predetermined voltage. It consists of a converter. That is, a series circuit of an inductor L0 and a switching element Q0 is connected between the output ends of the diode bridge DB, and a series circuit of a diode D0 and a capacitor C0 is connected in parallel to the switching element Q0. Furthermore, this embodiment has a power supply driving circuit E1 that drives the switching element Q0 of the DC power supply E on and off. The power supply drive circuit E1 changes the on-duty of the switching element Q0 as needed to keep the output voltage of the DC power supply E constant, for example. Since such a power supply drive circuit E1 can be realized by a known technique, detailed illustration and description thereof will be omitted.

  In the present embodiment, the control circuit 2 includes a driving capacitor Cs that serves as a power source for driving the first switching element Q1. One end of the driving capacitor Cs is connected to the source of the first switching element Q1. Furthermore, the present embodiment includes a charging capacitor Cc as a charging power source for charging the driving capacitor Cs. The charging capacitor Cc is made of, for example, an electrolytic capacitor, and one end (low voltage side) is connected to the ground, while the other end (high voltage side) is the side not connected to the first switching element Q1 in the driving capacitor Cs. To the terminal (that is, the terminal on the high voltage side) via a charging diode Dc. Further, the other end (high voltage side) of the charging capacitor Cc is connected to the high voltage side DC output terminal of the diode bridge DB via the resistor Rc, and the charging capacitor Cc is connected to the output of the diode bridge DB. It is charged from time to time. Note that, instead of connecting the charging capacitor Cc to the DC power supply E via the resistor Rc as described above, a current for charging the charging capacitor Cc may be generated using, for example, a transformer (not shown). .

  Furthermore, a series circuit of a resistor Rd and a switching element Q2 made of an N-channel MOSFET is connected in parallel between both ends of the diode D3.

  Here, during the period in which the current flows through the inductor L1, the driving capacitor Cs includes the power receiving capacitor Cc, the diode Dc, the driving capacitor Cs, the inductor L1, the capacitor C1, and the light emitting diode array LED. The battery is charged by a current flowing in a loop composed of a parallel circuit.

  In addition, during the period in which the second switching element Q2 is on, the driving capacitor Cs includes a series circuit of a charging capacitor Cc, a diode Dc, a driving capacitor Cs, a resistor Rd, and the second switching element Q2. It is charged by the current flowing in the loop composed of

  Next, the operation of the control circuit 2 will be described. The control circuit 2 receives the PWM signal Vp from the PWM signal generation circuit 3, and operates according to the input PWM signal Vp.

  First, the PWM signal Vp will be described. The PWM signal Vp has an on-duty of 0 to 1, and when the on-duty is neither 0 nor 1, the signal level (for example, voltage value) is periodically changed between the H level and the L level. A rectangular wave to be switched. Further, the PWM signal generation circuit 3 is input with a reset signal Vrs that takes either the H level or the L level, and the on-duty is set to 0 during the period when the reset signal Vrs is at the H level. The signal level of the PWM signal Vp output to the control circuit 2 is fixed to L level. The on-duty of the PWM signal Vp output by the PWM signal generation circuit 3 during the period when the reset signal Vrs is at the L level may be determined according to a program held in advance in the PWM signal generation circuit 3, for example. It is good also as what is determined according to the input from the outside.

  Note that the correspondence between the signal level of the reset signal Vrs and the operation is not limited to the above, and conversely, when the reset signal Vrs is at the L level, the PWM signal Vp may be fixed at the L level. . The reset signal Vrs may be input from the outside, or the reset signal Vrs is detected by detecting an abnormality such as a short circuit, an overcurrent, or a no-load state where no load is connected across the capacitor C1. An abnormality detection circuit (not shown) for outputting may be provided in the power supply device 1. Since the abnormality detection circuit as described above can be realized by a well-known technique, detailed illustration and description are omitted.

  The control circuit 2 increases the output power as the on-duty of the PWM signal Vp (that is, the ratio of the H level time in one cycle) is higher.

  Specifically, as shown in FIGS. 2 and 3, the control circuit 2 includes a delay circuit 21 that outputs a delay signal Vpd obtained by delaying the input PWM signal Vp by a predetermined delay time td, and a PWM signal Vp. An oscillation circuit 22 that generates a drive signal that is a rectangular wave having a sufficiently high frequency with respect to the frequency of the signal, and an AND circuit AND that takes a logical product of the delay signal Vpd output from the delay circuit 21 and the output of the oscillation circuit 22. Have The first switching element Q1 is turned on while the output of the AND circuit AND is at the H level, and the first switching element Q1 is turned off while the output of the AND circuit AND is at the L level. That is, during the period in which the delay signal Vpd is at the H level, the period (hereinafter referred to as “normal operation”) in which the first switching element Q1 is periodically turned on and off at the frequency of the drive signal is performed (hereinafter referred to as “normal operation”). Hereinafter, it is referred to as an “on period”. Furthermore, the period during which the delay signal Vpd is at the L level is a period during which the first switching element Q1 is maintained in the off state (hereinafter referred to as “off period”). The ratio of the on period Ton to the sum of the on period Ton and the off period Toff matches the on duty of the PWM signal Vp.

  Further, the control circuit 2 includes a subtracting circuit 23 that generates an output for driving the second switching element Q2 by subtracting the delay signal Vpd from the input PWM signal Vp and aligning the negative part to the L level. That is, the second switching element Q2 is turned on while the output of the subtraction circuit 23 is at the H level, and the second switching element Q2 is turned off while the output of the subtraction circuit 23 is at the L level.

  Therefore, as shown in FIG. 3, the second switching element Q2 is turned on once every on-period Ton, while the first switching element Q1 is kept off for the delay time td immediately before the start of the on-period Ton. As a result, a charging operation in which the driving capacitor Cs is charged is performed.

  Further, when the on-duty of the PWM signal Vp is 1 continuously from the time when the power source is turned on and the output of the DC power from the DC power source E is started, immediately after the power source is turned on as shown in FIG. The second switching element Q2 is turned on and the first switching element Q1 is turned off only during the delay time td, and thereafter, the first switching Q1 is repeatedly turned on and off while the second switching element Q2 is maintained in the off state. The normal operation to be driven is continued.

  According to the above configuration, the peak value of the charging current when the second switching element Q2 is turned on and the charging of the driving capacitor Cs is started is suppressed by the action of the resistor Rd as a so-called current limiting resistor.

  For example, when detecting or controlling an abnormality based on the current flowing through the second switching element Q2, the voltage across the resistor Rd can be used for detecting the current flowing through the second switching element Q2.

  Further, since the charging operation is performed for each on-period Ton, even if the voltage of the driving capacitor Cs decreases during the off-period Toff, the first switching element Q1 is reliably turned on with the start of the on-period Ton. Can do.

  Further, since the diode D1 is provided separately from the second switching element Q2 and is connected in parallel to the series circuit of the second switching element Q2 and the resistor Rd, during the period when the second switching element Q2 is turned off. No loss due to the resistance Rd occurs.

  Instead of using the delay circuit 21, as shown in FIG. 5, the control circuit 2 sets the period in which the PWM signal Vp is at the H level as it is as the on period Ton and the period in which the PWM signal Vp is at the L level as it is as the off period Toff. In addition, the second switching element Q2 may always be turned on (that is, a charging operation is performed) during the off period Toff. In this case, immediately after the power source is turned on and the output of the DC power from the DC power source E is started, the power source is turned on and the DC power source E is turned on so that the charging operation is performed even if the PWM signal Vp is at the H level. Immediately after the output of the DC power is started, separate control is required. Since the output for driving the second switching element Q2 as described above can be generated using, for example, a negation circuit (not shown) that negates the PWM signal Vp, detailed illustration and description thereof are omitted.

  Further, the DC power source E is not limited to the boost converter as described above, and a battery may be used as shown in FIG. 6 or another known DC power source may be used.

  Further, the charging operation may be intermittently performed a plurality of times for each ON period. If this configuration is adopted, electrical stress may be further suppressed.

(Embodiment 2)
Since the basic configuration of the present embodiment is the same as that described in the first embodiment with reference to FIGS.

  In the present embodiment, instead of determining the on / off switching timing of the first switching element Q1 during the on-period Ton based on the output of the oscillation circuit 22 as in the first embodiment, it flows through the inductor L1 constituting the output circuit. It is determined based on current (hereinafter referred to as “circuit current”) IL.

  Specifically, instead of providing the oscillation circuit 22 in the control circuit 2, as shown in FIG. 7, a timing circuit 4 for generating a drive signal and inputting it to the control circuit 2 is provided. Further, the inductor L1 is provided with a secondary winding. One end of the secondary winding that is on the high voltage side when the circuit current IL is increased is connected to the timing circuit 4 and the other end is connected to the ground. Yes. Further, a current detection resistor Ri as current detection means for detecting the circuit current IL is connected between the capacitor C1 and the diode D1. That is, the voltage (hereinafter referred to as “detection voltage”) Vd at the connection point between the current detection resistor Ri and the capacitor C1 is proportional to the circuit current IL, and this detection voltage Vd is input to the timing circuit 4. .

  As shown in FIG. 8, the timing circuit 4 includes a first comparator CP1 in which a predetermined first reference voltage Vr1 is input to an inverting input terminal and a detection voltage Vd is input to a non-inverting input terminal, and an inverting input terminal. A second comparator CP2 to which a predetermined second reference voltage Vr2 is input and a voltage induced in the secondary winding of the inductor L1 (hereinafter referred to as “induced voltage”) ZCD is input to the non-inverting input terminal. And an RS type flip-flop circuit FF in which the reset terminal R is connected to the output terminal of the first comparator CP1 and the set terminal S is connected to the output terminal of the second comparator CP2. The output terminal Q is an output terminal that outputs a drive signal.

  That is, when the first switching element Q1 is turned on, the detection voltage Vd gradually increases as the circuit current IL gradually increases as shown in FIG. 9, and eventually the detection voltage Vd reaches the first reference voltage Vr1. The first switching element Q1 is turned off. Then, the circuit current IL starts to decrease, and when the circuit current IL eventually reaches zero, the induced voltage ZCD rises and exceeds the second reference voltage Vr2, whereby the zero crossing of the circuit current IL is detected and the second comparator CP2 flips the circuit current IL. The input voltage to the set terminal S of the circuit FF becomes H level. Then, the first switching element Q1 is turned on again, and the same operation is repeated thereafter. That is, the second comparator CP2 is the zero cross detection means in the claims, and a value obtained by dividing the first reference voltage Vr1 by the resistance value of the current detection resistor Ri is a predetermined upper limit value in the claims. Only at the beginning of the ON period Ton, the ON control of the first switching element Q1 is performed after the charging operation according to the rising edge of the delay signal Vpd, not according to the detection of the zero cross as described above.

  The timing circuit 4 includes a timer circuit TM that counts the elapsed time since the last zero cross is detected (that is, after the output of the second comparator CP2 becomes H level). The timer circuit TM has a start terminal S connected to the output terminal of the second comparator CP2, a reset terminal R connected to the output terminal of the first comparator CP1, and an output terminal F connected to the control circuit 2. . The timer circuit TM normally sets the output to the control circuit 2 to L level, and starts measuring a predetermined standby time tc when the induced voltage ZCD rises and the output of the second comparator CP2 becomes H level. . The timer circuit TM resets the time when the output of the first comparator CP1 becomes H level during the time of the standby time tc, and then again when the output of the second comparator CP2 becomes H level. Start timing from zero. The timer circuit TM sets the output to the control circuit 2 to the H level when the timing of the standby time tc is completed without the output of the first comparator CP1 becoming the H level. The control circuit 2 performs a charging operation of turning on the second switching element Q2 while maintaining the first switching element Q1 in the off state during a period in which the output of the timer circuit TM is at the H level. Thus, for example, when the load such as the light emitting diode array LED is removed and the circuit current IL does not flow, the charging operation is performed regardless of the PWM signal Vp. In the example of FIG. 9, the induced voltage ZCD rises as the circuit current IL decreases to 0 even when the delay signal Vpd becomes L level. At this time, the delay signal Vpd becomes L level. The on control of the first switching element Q1 is not performed. The output of the timer circuit TM is returned to the L level, for example, when the delay signal Vpd becomes the H level.

  As the current detection means, instead of providing the current detection resistor Ri as described above, a resistor Rd connected in series to the second switching element Q2 may be used. However, when the diode D1 is separately provided as in the first embodiment and this embodiment without using the parasitic diode of the second switching element Q2 as the flywheel diode, the current detection resistor Ri is separately provided from the resistor Rd. It is desirable from the viewpoint of accuracy.

(Embodiment 3)
Since the basic configuration of the present embodiment is the same as that of the first embodiment, description of the common parts is omitted.

  In this embodiment, the diode D1 is omitted as shown in FIG. 10, and the parasitic diode of the second switching element Q2 functions as a flywheel diode. As a result, even when the second switching element Q2 is turned off, a loss at the resistor Rd occurs, but the number of components is reduced, and the manufacturing cost can be reduced. The omission of the diode D1 as described above is also possible in the first and second embodiments. Conversely, in the present embodiment, a separate diode D1 may be provided as in the first and second embodiments.

  In the present embodiment, the control circuit 2 switches the operation mode in accordance with the input switching signal, and the control circuit 2 switches the operation mode so that the light-emitting diode array LED is turned on. In addition to power output, AC power output for lighting the discharge lamp La shown in FIG. 11A is also possible. The switching signal may be input from the outside of the power supply device 1, or according to a user's operation input or according to detection of impedance between terminals 11 a, 12 a, 12 b, 13 a, and 13 b described later. Then, a switching circuit (not shown) for inputting a switching signal to the control circuit 2 may be provided. Since the switching circuit as described above can be realized by a well-known technique, detailed illustration and description thereof will be omitted.

  Further, in the present embodiment, one of a hot cathode type discharge lamp La having a pair of filaments and lighting with AC power input between the filaments and a light emitting diode array LED lighting with DC power is selected. Connection is possible.

  More specifically, in the present embodiment, a terminal (hereinafter referred to as “DC”) connected to the anode side of the light emitting diode array LED between the inductor L1 and a capacitor (hereinafter referred to as “first capacitor”) C1. 11a) is provided. Further, a second capacitor C2 is added between the first capacitor C1 and the ground, and both ends of the second capacitor C2 are connected to one end of one filament of the discharge lamp La or the cathode of the light emitting diode array LED, respectively. Terminals (hereinafter referred to as “shared terminals”) 12a and 12b are provided. That is, the shared terminals 12a and 12b are short-circuited with each other when the light-emitting diode array LED is connected. Such a short circuit may be performed by the load itself such as the light emitting diode array LED as described above, or is controlled to be on during the first operation mode to be described later and during the second operation mode to be described later. A switching element (not shown) that is controlled to be off may be provided between the shared terminals 12a and 12b.

  Furthermore, in this embodiment, in order to preheat each filament of the discharge lamp La, one end is connected to the connection point of the switching elements Q1 and Q2, and the other end is connected to the ground via the third capacitor C3. A transformer T1 having a winding is provided. The transformer T1 has two secondary windings, and one end of each secondary winding is connected to one of the shared terminals 12a and 12b. Further, two alternating currents connected to the other end of the secondary winding one by one and connected to the other end of one filament of the discharge lamp La (that is, one end on the side where the shared terminals 12a and 12b are not connected). Terminals 13a and 13b are provided.

  Next, the operation of the control circuit 2 in this embodiment will be described.

  Since the operation in the first operation mode executed during the period in which the output of the DC power is instructed by the switching signal may be any of the operations described in the first and second embodiments, the description thereof is omitted. During this period, DC power is output from the terminals 11, 12a, 12b at both ends of the first capacitor C1.

  In the second operation mode executed during the period in which the output of the AC power is instructed by the switching signal, the control circuit 2 performs an operation of alternately turning on and off the first switching element Q1 and the second switching element Q2. Do. That is, the first and second switching elements Q1 and Q2, the inductor L1, and the first and second capacitors C1 and C2 operate as a known half-bridge inverter, and are connected to one filament of the discharge lamp La. AC power is output between 12a and 13a and terminals 12b and 13b connected to the other filament. Moreover, at the time of starting, each filament of the discharge lamp La is preheated by the current induced in each secondary winding of the transformer T1. In the second operation as described above, the power output to the discharge lamp La includes the resonance frequency of the resonance circuit formed by the inductor L1, the first and second capacitors C1 and C2, and the discharge lamp La, and the control circuit 2. Varies depending on the relationship with the frequency (hereinafter referred to as “operation frequency”) at which the first and second switching elements Q1, Q2 are alternately turned on and off. Therefore, the control circuit 2 detects the output power to the discharge lamp La based on the voltage across the resistor Rd, and changes the operating frequency as needed so that the output power to the discharge lamp La becomes a predetermined target value. Feedback control may be performed.

  Here, in each of the above embodiments, the second switching element Q2 may be configured as a one-chip integrated circuit together with the control circuit 2, and other elements may be integrated. The elements integrated with the control circuit 2 include, in addition to the second switching element Q2, a resistor Rd connected in series with the second switching element Q2, and a charging capacitor Cc and a driving capacitor Cs. The driving capacitor Cs may be integrated if technically possible. By appropriately integrating as described above, it is possible to reduce the number of components and reduce the size. Further, when the second switching element Q2 is integrated, compared to the case where only the control circuit 2 is configured as an integrated circuit, the integrated circuit constituting the control circuit 2 is connected to the gate of the second switching element Q2. Terminals can be reduced. In this case, the second switching element Q2 can be formed as a DMOS (Double-Diffused MOSFET) structure using a known technique called a high breakdown voltage process.

  Even when a P-channel MOSFET is used as the first switching element Q1 in place of the N-channel MOSFET as described above, the first switching element Q1 is connected to a lower voltage side than the diode D1. When the circuit configuration is as described above, the driving capacitor Cs as described above is required. In this case, since the parasitic diode of the first switching element Q1 is also opposite to the output of the DC power supply E, the drain of the first switching element Q1 is connected to the DC power supply E and the source is connected to the diode D1. The

  The various power supply devices 1 described in the above embodiments can be housed as shown by, for example, the arrow A1 in the fixture body 51 as shown in FIGS. . The appliance main body 51 holds an electrical light source such as a light emitting diode array LED and a discharge lamp La connected to the power supply device 1 by an appropriate means according to the form of the electrical light source. Since the instrument main body 51 as described above can be realized by a well-known technique, detailed illustration and description thereof are omitted. Instead of the light emitting diode array LED, another known electrical light source that is lit with DC power, such as an organic EL, may be connected.

DESCRIPTION OF SYMBOLS 1 Power supply device 2 Control circuit 3 PWM signal generation circuit 5 Lighting fixture 51 Appliance main body C1 Capacitor (a part of output circuit in a claim)
Cc Charging capacitor (Charging power source in claims)
CP2 second comparator (zero cross detection means in claims)
Cs Driving capacitor D1 Diode E DC power supply L1 Inductor (part of output circuit in claims)
Q1 first switching element Q2 second switching element Ri current detection resistor (current detection means in claims)

Claims (7)

A DC power source that outputs DC power;
A first switching element having one end connected to the output end of the DC power supply;
A diode connected in series with the first switching element and opposite to the output of the DC power supply;
An output circuit including an inductor that forms a loop with a diode and connected to a load;
A driving capacitor having one end connected between the first switching element and the diode;
A charging power source connected to the other end of the driving capacitor and supplied with power from a DC power source to charge the driving capacitor;
A second switching element for turning on and off a short circuit between both ends of the diode;
A control circuit for driving the second switching element on and off and driving the first switching element on and off using a driving capacitor as a power source;
The control circuit operates in an on period in which the first switching element is repeatedly turned on and off while maintaining the second switching element in an off state according to the signal level of the input PWM signal, and the first switching element is in the off state. One of the off-period operations of maintaining
Immediately before switching the operation from the off period to the on period, a charging operation is performed in which the driving capacitor is charged by turning on the second switching element while maintaining the first switching element in the off state. Power supply. A PWM signal generation circuit for inputting the PWM signal to the control circuit;
The PWM signal generation circuit inputs a PWM signal to the control circuit so as to continue the operation in the off period during a period in which the signal level of the reset signal input from the outside is a predetermined level. The power supply described.   The power supply device according to claim 1 or 2, wherein the control circuit and the second switching element are integrated in one integrated circuit. Zero-cross detection means for detecting the zero-cross of the current flowing through the inductor of the output circuit;
Current detection means for detecting the current flowing in the inductor of the output circuit,
The control circuit turns on the first switching element when the zero cross is detected by the zero cross detecting means during the operation of the on period, and when the current detected by the current detecting means reaches a predetermined upper limit value To turn off the first switching element,
2. The charging operation is started when the current detected by the current detecting means does not reach the predetermined upper limit value even if a predetermined time has elapsed after the zero cross is detected by the zero cross detecting means. The power supply device according to any one of?   The power supply apparatus according to claim 1, wherein the output circuit includes a capacitor connected between both ends of the diode as a series circuit with the inductor. The output circuit has two capacitors connected across the diode as a series circuit with the inductor,
The control circuit alternately turns on and off the first operation mode in which the operation in the on period and the operation in the off period are performed, and the second switching element and the first switching element, according to the input switching signal. The power supply device according to any one of claims 1 to 4, wherein the power supply device can operate in the second operation mode.   A power supply device according to any one of claims 1 to 6 and an appliance main body that holds the power supply device are provided, and an electric light source as a load is turned on by electric power output from an output circuit. lighting equipment.

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