JP4649729B2 - Power supply device and discharge lamp lighting device - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply device that converts a DC power supply to obtain a desired DC output, and a discharge lamp lighting device that lights a discharge lamp using such a power supply device.
[0002]
[Prior art]
An example of a conventional power supply device (hereinafter referred to as “conventional example 1”) is shown in FIG. This conventional example 1 includes a DC / DC conversion circuit 2 that converts the output of a DC power source 1 such as a battery, an output control circuit 61 that controls the output of the DC / DC conversion circuit 2, and a load circuit including a load 50. And 5. The DC / DC conversion circuit 2 is composed of a conventionally known boost converter (boost converter), and boosts from a low voltage power source (DC power source 1) like a battery to a voltage required by the load 50 such as a discharge lamp. It is.
[0003]
The output of the conventional example 1 is mainly adjusted by the DC / DC conversion circuit 2, the output current and the output voltage are detected at the output terminal of the DC / DC conversion circuit 2, and the power command output from the power command value generation circuit 601 is output. Based on the value, the control target value of the load current (lamp current) corresponding to the detected value of the load voltage (lamp voltage) is calculated by the current command value calculation unit 602, and feedback control is performed. The on / off control signal of the switching element 22 included in the DC / DC conversion circuit 2 is obtained by a triangular wave comparison method in which the output of the error amplifier 603 and the output of the triangular wave oscillator 604 are compared by a comparator 605. The switching signal has a constant frequency. By changing the on-duty ratio, a PWM signal for adjusting the output is obtained.
[0004]
On the other hand, as shown in FIG. 14, there is a conventional example (hereinafter referred to as “conventional example 2”) in which the load 51 is a discharge lamp and the DC / DC conversion circuit 2 is a flyback converter. This conventional example 2 includes a DC power source 1, a DC / DC conversion circuit 2 composed of a flyback converter, and a load circuit 5. The load circuit 5 is a discharge lamp from a DC voltage obtained by the DC / DC conversion circuit 2. An inverter circuit 3 for supplying an alternating voltage to 51 and a starting circuit 4 for applying a high voltage to start the discharge lamp 51 in an extinguished state are provided. Here, since the discharge lamp 51 changes in lamp voltage from a low condition to a high condition as compared with the power supply voltage of the DC power supply 1, the DC / DC conversion circuit 2 is flybacked to cope with such a load. It is desirable to configure with a converter. That is, in the DC / DC conversion circuit 2 composed of this flyback converter, when the switching element 22 is turned on, the current I1 flows from the DC power source 1 to the primary winding of the transformer 21 and energy is stored in the transformer 21. When the switching element 22 is turned off, the diode 23 is turned on by the counter electromotive force generated by the energy stored in the transformer 21, and the current I2 flows from the secondary winding to the capacitor 24, so that the output capacitor 24 is charged. By controlling the ON period and the OFF period of the switching element 22, the voltage of the output capacitor 24 can be changed from a low condition to a high condition as compared with the power supply voltage of the DC power supply 1. Note that there is a buck-boost converter (polarity inversion chopper circuit) as a step-up / down converter that realizes the same function.
[0005]
By the way, the output control circuit 62 of the conventional example 2 may be PWM control with a constant frequency as in the conventional example 1, but a battery having a large voltage fluctuation is used for the DC power source 1 and the output voltage fluctuation is changed like the discharge lamp 51. In order to drive a large load, the output control circuit 6 performs the following control.
[0006]
First, the power command value generation circuit 601 generates a power command value for determining the output power of the DC / DC conversion circuit 2, and the current command value calculation unit 602 receives the power command given from the power command value generation circuit 601. A current command value that is a control target of the output current of the DC / DC conversion circuit 2 is calculated from the value and the voltage across the capacitor 24. For this purpose, the voltage across the capacitor 24 of the DC / DC conversion circuit 2 is detected by the output voltage detection means and input to the current command value calculation unit 602 via the amplifier 607. The current command value calculated by the current command value calculation unit 602 becomes one input of the error amplifier 603. The other input of the error amplifier 603 receives an output current detected by an output current detecting means provided between the output of the DC / DC conversion circuit 2 and the input of the inverter circuit 3 via the amplifier 606. . The error amplifier 603 creates a primary peak current command from the current command value given from the current command value calculation unit 602 and the detected value of the output current input through the amplifier 606, and the inverting input terminal of the comparator 610. To enter.
[0007]
The detection value of the primary current I1 and the detection value of the secondary current I2 of the transformer 21 of the DC / DC conversion circuit 2 are input to the output control circuit 6. The detected value of the primary side current I1 is input to the non-inverting input terminal of the comparator 610. When the detected value becomes larger than the primary side peak current command, a reset signal is sent to the reset terminal of the oscillation circuit 608. The detected value of the secondary current I2 is input to the inverting input terminal of the comparator 609. The non-inverting input terminal of the comparator 609 is connected to the circuit ground. Therefore, when the detected value of the secondary current I2 becomes substantially zero, a set signal is sent from the comparator 609 to the set terminal of the oscillation circuit 608. The oscillation circuit 608 is configured to include a set / reset flip-flop, and the switching element 22 of the DC / DC conversion circuit 2 is controlled to be turned on / off by its Q output.
[0008]
That is, in the output control circuit 6 of the second conventional example, the output of the error amplifier 603 serving as an output adjustment value is used as the peak command value of the current I1 flowing to the primary side of the transformer 21, and the command value and the primary current I1 are detected. When the value is compared by the comparator 610 and the detected value exceeds the command value, the Q output of the oscillation circuit 608 becomes L level, and the switching element 22 is turned off. After the switching element 22 is turned off, all the energy of the transformer 21 is discharged to the secondary side, and it is detected by the comparator 609 that the secondary side current I2 has become substantially zero, and the output of the oscillation circuit 608 is set to H level. The switching element 22 is turned on. That is, as shown in FIG. 15, when the secondary current I2 of the transformer 21 becomes substantially zero, an operation mode for turning on the switching element 22 that controls the primary current I1 of the transformer 21 is called a current boundary mode. By operating in this current boundary mode, the utilization factor of the transformer 21 can be increased. In the oscillation circuit 608, as shown in FIG. 16, there is a case where a limit value is provided for the maximum off period of the switching element 22 and the switching element 22 is turned off before the secondary side current I2 becomes zero. In order to prevent an increase in peak current accompanying a decrease in the switching frequency of the switching element 22 when the lamp voltage is low as in the state where the lamp 51 is cold and the slope of the waveform of the secondary current I2 is small, The limit value is adjusted according to the state. The output control circuit 6 performs output control by adjusting the primary-side peak current value for turning off the switching element 22 by feedback control similar to that in the first conventional example.
[0009]
[Problems to be solved by the invention]
By the way, in the DC / DC conversion circuit 2 composed of the flyback converter of the conventional example 2, the magnetic flux density of the core of the transformer 21 tends to be high because the output power is once stored in the transformer 21, and the core of the core is used to prevent saturation. Miniaturization was difficult. In the case of the DC / DC conversion circuit 2 including the boost converter as in the conventional example 1, since the power supply to the load 51 is performed by the inductor 211 and the DC power source 1, the flyback converter and the back-up of the conventional example 2 are usually used. Although it is possible to lower the magnetic flux density of the inductor as compared with the boost converter, when the load 51 is a discharge lamp, the output adjustment becomes difficult because the load 51 is present from a load condition close to a short circuit.
[0010]
Furthermore, in a DC / DC conversion circuit that uses the boosting action of a transformer such as a forward converter, the magnetic flux of the transformer can be reduced. However, since the transformer turns ratio is defined by the maximum output voltage, In the case of a load with a wide voltage fluctuation range, the winding amount becomes large, and it becomes difficult to reduce the size of the transformer.
[0011]
The present invention has been made in view of the above circumstances, and an object of the present invention is to adjust the output even with a load having a large voltage fluctuation, thereby reducing the magnetic flux density of the transformer and reducing the size of the core. An object of the present invention is to provide a possible power supply device and discharge lamp lighting device.
[0012]
[Means for Solving the Problems]
  In order to achieve the above object, a first aspect of the present invention provides a DC / DC conversion circuit for converting a power supply voltage of a DC power source into a desired DC voltage, and a DC output of the DC / DC conversion circuit is adjusted and supplied to a load. The DC / DC conversion circuit includes a switching element, a transformer to which a power supply voltage of a DC power source is applied to the primary winding via the switching element, and a rectifier element in the secondary winding of the transformer. And a load circuit and a tertiary winding of a transformer are connected in series via at least an inductor between both ends of the capacitor.A power supply apparatus comprising a control circuit that controls on / off of the switching element to vary the DC output of the DC / DC conversion circuit, and the secondary winding of the tertiary winding of the transformer included in the DC / DC conversion circuit A part of the primary side closed circuit component is connected to the secondary side closed circuit of the transformer, and is also used as an inductance of the secondary side closed circuit including at least the secondary winding and the capacitor. The time constant determined is sufficiently larger than the switching cycle of the switching element by the control circuit.When the switching element is turned on, current flows from the DC power source to the primary winding and energy is stored in the transformer, and the voltage obtained by superimposing the voltage across the capacitor on the voltage generated in the tertiary winding causes the inductor to When the switching element is turned off, the energy stored in the transformer is discharged from the secondary winding to charge the capacitor, and a DC voltage is applied from the capacitor to the load circuit via the tertiary winding. Supplied. In this way, a DC voltage is supplied to the load circuit both when the switching element is on and off, and in particular, a DC voltage boosted by the transformer boosting action when the switching element is on is supplied to the load circuit. The accumulated energy can be reduced. As a result, the output can be adjusted even with a load having a large voltage fluctuation, and the core can be downsized by reducing the magnetic flux density of the transformer.Further, the transformer can be reduced in size by using the tertiary winding also as the secondary winding.
[0016]
  Claim2The invention of claim1In the present invention, one end of the secondary winding of the transformer is connected to one end of the primary winding via the capacitor, and the other end of the primary winding and the other end of the secondary winding are connected via a rectifier element. In this way, a closed circuit on the secondary side is formed, and a load circuit is connected to both ends of a series circuit of the primary and secondary windings of the transformer and the capacitor via at least an inductor, Claim1The same effect as that of the present invention is achieved.
[0017]
  Claim3The invention of claim1In the present invention, one end of the secondary winding of the transformer is connected to the DC power source via the rectifier element, and the other end of the secondary winding is connected to the DC power source via the capacitor, thereby closing the secondary circuit. And a load circuit is connected to both ends of a series circuit of a secondary winding of the transformer, the capacitor, and a DC power source via an inductor.1The same effect as that of the present invention is achieved.
[0018]
  Claim4The invention of claim1In this invention, a closed circuit on the secondary side is formed by connecting a series circuit of a rectifier element, the switching element, and the capacitor to both ends of the secondary winding of the transformer, and the secondary winding of the transformer, the capacitor, A load circuit is connected to both ends of a series circuit of switching elements via an inductor, and1The same effect as that of the present invention is achieved.
[0019]
  Claim5In order to achieve the above object, the invention of claim 1 to claim 14The discharge lamp is characterized by the fact that the load described in is used as a discharge lamp, and the output can be adjusted even with a load with large voltage fluctuations, and the core can be miniaturized by reducing the magnetic flux density of the transformer A device can be provided.
[0020]
  Claim6The invention of claim5The load circuit includes an inverter circuit that alternately supplies a direct current output of a DC / DC conversion circuit to supply the discharge lamp to the discharge lamp.5The same effect as that of the present invention is achieved.
[0021]
  Claim7The invention of claim5 or 6In the invention, the load circuit includes a starting circuit for applying a high starting voltage to the discharge lamp.5 or 6The same effect as that of the present invention is achieved.
[0022]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. However, each of the following embodiments includes the load circuit 5 having the same configuration as the load circuit 5 of the conventional example 2 in which the load 51 is a discharge lamp, but the load circuit 5 and the load 51 are limited to those of the embodiment. Instead, the technical idea of the present invention can be applied even when the load circuit 5 having another configuration or the load circuit 5 including the load 51 other than the discharge lamp is provided.
[0023]
  Before describing embodiments of the present invention, reference examples of the present invention will be described.
  Figure 1Reference exampleThe schematic circuit block diagram of this power supply device (discharge lamp lighting device) is shown. BookReference exampleIncludes a DC / DC conversion circuit 2 that converts a power supply voltage of a DC power supply 1 such as a battery into a desired DC voltage, and a DC output of the DC / DC conversion circuit 2 is adjusted and supplied to a load (not shown). And a load circuit 5. However, thisReference exampleSince the basic configuration is the same as that of the conventional example 2, the same components are denoted by the same reference numerals and the description thereof is omitted.
[0024]
The DC / DC conversion circuit 2 includes a switching element 22 composed of a transistor, a transformer 21 to which the power supply voltage of the DC power source 1 is applied to the primary winding n1 via the switching element 22, and a secondary winding of the transformer 21. A smoothing capacitor 24 connected to n2 via a diode 23 is provided, and the load circuit 5 and the tertiary winding n3 of the transformer 21 are connected in series between both ends of the smoothing capacitor 24 via at least an inductor 27. A ripple reducing capacitor 26 is connected in parallel to the smoothing capacitor 24, the tertiary winding n3, and the inductor 27.
[0025]
The control circuit 6 has, for example, a circuit configuration common to the control circuit of Conventional Example 1 or Conventional Example 2, and detects the output current and output voltage of the DC / DC conversion circuit 2, and the detected values are PWM control (see Conventional Example 1) that varies the on-duty ratio of the switching element 22 so as to obtain a desired value, or control that operates in the current boundary mode during steady state (see Conventional Example 2) is performed. However, the configuration of the control circuit 6 is not limited to this, and other control may be performed.
[0026]
  Next bookReference exampleThe circuit operation of the DC / DC conversion circuit 2 will be described.
[0027]
First, when the switching element 22 is turned on, a DC current I1 flows from the DC power source 1 to the primary winding n1 of the transformer 21 and energy is accumulated in the transformer 21, and a reverse induced voltage is applied to the secondary winding n2 of the transformer 21. However, no current flows because the diode 23 is connected. On the other hand, an induced voltage is generated in the tertiary winding n3 by boosting the input voltage on the primary side by the boosting action of the transformer 21, and the voltage obtained by superimposing the voltage across the smoothing capacitor 24 on the induced voltage of the tertiary winding n3. (Superimposed voltage) is supplied to the load circuit 5 via the inductor 27.
[0028]
On the other hand, when the switching element 22 is off, energy (particularly excitation energy) accumulated in the transformer 21 is discharged from the secondary winding n2 through the diode 23 to charge the smoothing capacitor 24. At this time, the output current I3 flowing through the tertiary winding n3 of the transformer 21 is stabilized by the inductor 27 which is a current limiting element. That is, by repeatedly turning the switching element 22 on and off by the control circuit 6, the DC / DC conversion circuit 2 can convert the power supply voltage of the DC power supply 1 into a DC voltage of a desired level. Here, the current boundary mode in which the control circuit 6 turns on the switching element 22 when the charging current I2 from the transformer 21 to the smoothing capacitor 24 becomes zero when the switching element 22 is turned off, and the primary winding n1 of the transformer 21. Alternatively, FIG. 2 and FIG. 3 show operation waveform diagrams in the continuous current mode in which a current always flows through the secondary winding n2.
[0029]
  Thus, the bookReference exampleIn the DC / DC conversion circuit 2 in FIG. 2, as described above, a DC voltage is supplied to the load circuit 5 both when the switching element 22 is turned on and when it is turned off. The energy stored in the transformer 21 can be reduced by supplying the direct current voltage to the load circuit 5 (see FIG. 3E). As a result, the output can be adjusted by the control circuit 6 even for a load with a large voltage fluctuation such as a discharge lamp, and the magnetic flux density φ of the transformer 21 can be lowered to reduce the size of the core.
[0030]
  (Embodiment1)
  FIG. 4 shows a schematic circuit configuration diagram of the power supply device (discharge lamp lighting device) of the present embodiment. This embodimentReference exampleThe secondary winding n2 is also used as the tertiary winding n3 of the DC / DC conversion circuit 2 in FIG.Reference exampleAnd in common. Therefore,Reference exampleThe same reference numerals are given to the same components as those in FIG.
[0031]
  In the DC / DC conversion circuit 2 according to the present embodiment, the anode of the diode 23 is connected to the connection point between one end of the secondary winding n2 of the transformer 21 and the inductor 27, and the cathode of the diode 23 and the secondary winding n2 are connected. A smoothing capacitor 24 is connected between the ends,Reference exampleThe secondary winding n2 has the function of the tertiary winding n3.
[0032]
Next, the circuit operation of the DC / DC conversion circuit 2 in this embodiment will be described.
[0033]
First, when the switching element 22 is turned on, a DC current I1 flows from the DC power source 1 to the primary winding n1 of the transformer 21 and energy is accumulated in the transformer 21, and the secondary winding n2 of the transformer 21 stores the primary winding n1. An induced voltage boosted to the turn ratio of the secondary winding n2 is generated, and a superimposed voltage of the induced voltage and the voltage across the smoothing capacitor 24 is supplied to the load circuit 5 via the inductor 27.
[0034]
On the other hand, when the switching element 22 is turned off, the energy accumulated in the transformer 21 is discharged from the secondary winding n2 through the diode 23 to charge the smoothing capacitor 24. That is, by repeatedly turning on and off the switching element 22 by the control circuit 6, a desired DC voltage stabilized by the inductor 27 can be supplied from the DC / DC conversion circuit 2 to the load circuit 5. Here, FIGS. 5 and 6 show operation waveform diagrams when the control operation by the control circuit 6 is in the current boundary mode and in the current continuous mode, respectively.
[0035]
Incidentally, it is possible to reduce the magnetic flux density φ of the transformer 21 when the power supply amount supplied to the load circuit 5 when the switching element 22 is on is larger than the power supply amount when the switching element 22 is off. For this reason, the resonant frequency between the capacitance of the smoothing capacitor 24 and the inductance on the secondary side of the transformer 21 is set to be sufficiently lower than the switching frequency of the switching element 22 by the control circuit 6.
[0036]
  Thus, also in the DC / DC conversion circuit 2 in this embodiment.Reference exampleIn the same manner as described above, a DC voltage is supplied to the load circuit 5 both when the switching element 22 is turned on and when it is turned off. In particular, a DC voltage boosted by the boosting action of the transformer 21 is supplied to the load circuit 5 As a result, the energy stored in the transformer 21 can be reduced (see FIG. 6E). Moreover, there is an advantage that the transformer 21 can be reduced in size by using the tertiary winding n3 also as the secondary winding n2. Further, the DC / DC conversion circuit 2 according to the present embodiment can boost the voltage higher than the step-up ratio of the transformer 21 as compared with the forward converter. In particular, when the load 51 is a discharge lamp, the steady state lighting is performed immediately before the start of discharge. However, it is not necessary to increase the number of turns of the transformer 21 in order to obtain such a high voltage, and there is an advantage that the transformer 21 can be reduced in size.
[0037]
  (Embodiment2)
  FIG. 7 shows a schematic circuit configuration diagram of the power supply device (discharge lamp lighting device) of the present embodiment. This embodiment is an embodiment1In the DC / DC conversion circuit 2, one end of the secondary winding n2 of the transformer 21 is connected to one end of the primary winding n1 through the smoothing capacitor 24, and the other end of the primary winding n1 and the secondary winding n2 are connected. Are connected via a diode 23 to form a closed circuit on the secondary side, and at least an inductor 27 is connected to both ends of the series circuit of the primary winding n1 and secondary winding n2 of the transformer 21 and the smoothing capacitor 24. It is characterized in that the load circuit 5 is connected via the, and other configurations are the embodiments.1And in common. Thus, the embodiment1The same reference numerals are given to the same components as those in FIG.
[0038]
In the DC / DC conversion circuit 2 of the present embodiment, one end of the switching element 22 is connected to the positive electrode of the DC power supply 1, and the primary winding n <b> 1 of the transformer 21 is connected between the other end of the switching element 22 and the negative electrode of the DC power supply 1. Is connected. A smoothing capacitor 24 is connected to one end of the primary winding n1 connected to the switching element 21 and one end of the secondary winding n2, and the other end of the secondary winding n2 is connected to the cathode of the diode 23 and the inductor. The anode of the diode 23 is connected to the negative electrode of the DC power source 1.
[0039]
Next, the circuit operation of the DC / DC conversion circuit 2 in this embodiment will be described.
[0040]
First, when the switching element 22 is turned on, a DC current I1 flows from the DC power source 1 to the primary winding n1 of the transformer 21 and energy is accumulated in the transformer 21, and the secondary winding n2 of the transformer 21 stores the primary winding n1. An induced voltage boosted to the turn ratio of the secondary winding n2 is generated, and a superimposed voltage of the induced voltage and the voltage across the smoothing capacitor 24 is supplied to the load circuit 5 via the inductor 27.
[0041]
On the other hand, when the switching element 22 is turned off, the energy accumulated in the transformer 21 is discharged from the primary winding n1 and the secondary winding n2 through the diode 23 to charge the smoothing capacitor 24. That is, by repeatedly turning on and off the switching element 22 by the control circuit 6, a desired DC voltage stabilized by the inductor 27 can be supplied from the DC / DC conversion circuit 2 to the load circuit 5.
[0042]
By the way, it is possible to reduce the magnetic flux density of the transformer 21 when the power supply amount supplied to the load circuit 5 when the switching element 22 is on is larger than the power supply amount when the switching element 22 is off. For this reason, the resonant frequency between the capacitance of the smoothing capacitor 24 and the inductance on the secondary side of the transformer 21 is set to be sufficiently lower than the switching frequency of the switching element 22 by the control circuit 6.
[0043]
  Thus, also in the DC / DC conversion circuit 2 in this embodiment.Reference exampleIn the same manner as described above, a DC voltage is supplied to the load circuit 5 both when the switching element 22 is turned on and off, and in particular, a DC voltage boosted by the boosting action of the transformer 21 is supplied to the load circuit 5 when the switching element 22 is turned on. As a result, the energy accumulated in the transformer 21 can be reduced, and the embodiment1Similarly, the transformer 21 can be reduced in size by using the tertiary winding n3 also as the secondary winding n2. In addition, since the energy stored in the transformer 21 is released to the smoothing capacitor 24 via the primary winding n1 and the secondary winding n2 when the switching element 22 is turned off, the number of turns of the secondary winding n2 of the transformer 21 is reduced. Further, there is an advantage that the transformer 21 can be miniaturized. Further, in the DC / DC conversion circuit 2 in the present embodiment, the embodiment is described.1Similarly to the forward converter, it is possible to boost the voltage more than the boost ratio of the transformer 21. In particular, when the load 51 is a discharge lamp, a voltage several times that at the time of steady lighting is required immediately before the start of discharge. In order to obtain such a high voltage, there is no need to increase the number of turns of the transformer 21, and there is an advantage that the transformer 21 can be miniaturized.
[0044]
  (Embodiment3)
  FIG. 8 shows a schematic circuit configuration diagram of the power supply device (discharge lamp lighting device) of the present embodiment. This embodiment is an embodiment1In the DC / DC conversion circuit 2, one end of the secondary winding n 2 of the transformer 21 is connected to the DC power source 1 through a rectifier element, and the other end of the secondary winding n 2 is connected to the DC power source 1 through a smoothing capacitor 24. A secondary closed circuit is formed by connection, and the load circuit 5 is connected to both ends of a series circuit of the secondary winding n2 of the transformer 21, the smoothing capacitor 24, and the DC power source 1 via an inductor 27. There are other configurations in the embodiment1And in common. Thus, the embodiment1The same reference numerals are given to the same components as those in FIG.
[0045]
In the DC / DC conversion circuit 2 of the present embodiment, one end of the primary winding n1 of the transformer 21 is connected to the positive electrode of the DC power source 1, and the other end of the primary winding n1 is connected to the DC power source 1 via the switching element 22. The negative electrode is connected. Then, one end of the secondary winding n2 of the transformer 21 is connected to the positive electrode of the DC power source 1 through the smoothing capacitor 24, and the other end of the secondary winding n2 is connected to the anode of the diode 23 and one end of the inductor 27. The cathode of the diode 23 is connected to the negative electrode of the DC power source 1.
[0046]
Next, the circuit operation of the DC / DC conversion circuit 2 in this embodiment will be described.
[0047]
First, when the switching element 22 is turned on, a DC current I1 flows from the DC power source 1 to the primary winding n1 of the transformer 21 and energy is accumulated in the transformer 21, and the secondary winding n2 of the transformer 21 stores the primary winding n1. An induced voltage boosted to the turn ratio of the secondary winding n2 is generated, and a voltage obtained by subtracting the power supply voltage of the DC power supply 1 from the superimposed voltage of the induced voltage and the voltage across the smoothing capacitor 24 is passed through the inductor 27. To the load circuit 5.
[0048]
On the other hand, when the switching element 22 is turned off, the energy accumulated in the transformer 21 is discharged from the secondary winding n2 through the diode 23 and the smoothing capacitor 24 is charged by the DC power source 1 as well. That is, by repeatedly turning on and off the switching element 22 by the control circuit 6, a desired DC voltage stabilized by the inductor 27 can be supplied from the DC / DC conversion circuit 2 to the load circuit 5. Here, FIGS. 9 and 10 show operation waveform diagrams when the control operation by the control circuit 6 is in the current boundary mode and in the current continuous mode, respectively.
[0049]
By the way, it is possible to reduce the magnetic flux density of the transformer 21 when the power supply amount supplied to the load circuit 5 when the switching element 22 is on is larger than the power supply amount when the switching element 22 is off. For this reason, the resonant frequency between the capacitance of the smoothing capacitor 24 and the inductance on the secondary side of the transformer 21 is set to be sufficiently lower than the switching frequency of the switching element 22 by the control circuit 6.
[0050]
  Thus, also in the DC / DC conversion circuit 2 in this embodiment.Reference exampleIn the same manner as described above, a DC voltage is supplied to the load circuit 5 both when the switching element 22 is turned on and off, and in particular, a DC voltage boosted by the boosting action of the transformer 21 is supplied to the load circuit 5 when the switching element 22 is turned on. As a result, the energy accumulated in the transformer 21 can be reduced, and the embodiment1Similarly, the transformer 21 can be reduced in size by using the tertiary winding n3 also as the secondary winding n2. In addition, since the smoothing capacitor 24 is charged not only from the energy stored in the transformer 21 when the switching element 22 is turned off but also from the DC power source 1 through the secondary winding n2, the ripple of the input current can be reduced. There is an advantage. Further, in the DC / DC conversion circuit 2 in the present embodiment, the embodiment is described.1And embodiments2Similarly to the forward converter, it is possible to boost the voltage more than the boost ratio of the transformer 21. In particular, when the load 51 is a discharge lamp, a voltage several times that at the time of steady lighting is required immediately before the start of discharge. In order to obtain such a high voltage, there is no need to increase the number of turns of the transformer 21, and there is an advantage that the transformer 21 can be miniaturized.
[0051]
11, the polarity of the secondary winding n2 of the transformer 21 is inverted, the anode of the diode 23 is connected to the negative electrode of the DC power supply 1, and the cathode is connected to one end of the secondary winding n2 and the inductor 27. The same operation and effect can be obtained with the circuit configuration.
[0052]
  (Embodiment4)
  FIG. 12 shows a schematic circuit configuration diagram of the power supply device (discharge lamp lighting device) of the present embodiment. This embodiment is an embodiment1In the DC / DC conversion circuit 2, a secondary closed circuit is formed by connecting a series circuit of a diode 23, a switching element 22 and a smoothing capacitor 24 to both ends of the secondary winding n 2 of the transformer 21. A characteristic is that the load circuit 5 is connected to both ends of a series circuit of the secondary winding n2, the smoothing capacitor 24, and the switching element 22 via an inductor 27, and the other configuration is an embodiment.1And in common. Thus, the embodiment1The same reference numerals are given to the same components as those in FIG.
[0053]
In the DC / DC conversion circuit 2 of the present embodiment, one end of the primary winding n1 of the transformer 21 is connected to the positive electrode of the DC power source 1, and the other end of the primary winding n1 is connected to the DC power source 1 via the switching element 22. The negative electrode is connected. Then, one end of the secondary winding n2 of the transformer 21 is connected to the connection point of the switching element 22 and the primary winding n1 via the smoothing capacitor 24, and the other end of the secondary winding n2 is connected to the anode of the diode 23 and the inductor. The cathode of the diode 23 is connected to the negative electrode of the DC power source 1.
[0054]
Next, the circuit operation of the DC / DC conversion circuit 2 in this embodiment will be described.
[0055]
First, when the switching element 22 is turned on, a DC current I1 flows from the DC power source 1 to the primary winding n1 of the transformer 21 and energy is accumulated in the transformer 21, and the secondary winding n2 of the transformer 21 stores the primary winding n1. An induced voltage boosted to a turn ratio of the secondary winding n2 is generated, and a superimposed voltage of the induced voltage and the voltage across the smoothing capacitor 24 is supplied to the load circuit 5 through the switching element 22 and the inductor 27. The
[0056]
On the other hand, when the switching element 22 is turned off, the energy accumulated in the transformer 21 is discharged from the secondary winding n2 through the diode 23, the DC power source 1 and the primary winding n1, and the DC capacitor 1 also causes the smoothing capacitor 24 to be discharged. Charge. That is, by repeatedly turning on and off the switching element 22 by the control circuit 6, a desired DC voltage stabilized by the inductor 27 can be supplied from the DC / DC conversion circuit 2 to the load circuit 5.
[0057]
By the way, it is possible to reduce the magnetic flux density of the transformer 21 when the power supply amount supplied to the load circuit 5 when the switching element 22 is on is larger than the power supply amount when the switching element 22 is off. For this reason, the resonant frequency between the capacitance of the smoothing capacitor 24 and the inductance on the secondary side of the transformer 21 is set to be sufficiently lower than the switching frequency of the switching element 22 by the control circuit 6.
[0058]
  Thus, also in the DC / DC conversion circuit 2 in this embodiment.Reference exampleIn the same manner as described above, a DC voltage is supplied to the load circuit 5 both when the switching element 22 is turned on and off, and in particular, a DC voltage boosted by the boosting action of the transformer 21 is supplied to the load circuit 5 when the switching element 22 is turned on. As a result, the energy accumulated in the transformer 21 can be reduced, and the embodiment1Similarly, the transformer 21 can be reduced in size by using the tertiary winding n3 also as the secondary winding n2. Embodiments3As well as the energy accumulated in the transformer 21 when the switching element 22 is turned off, the smoothing capacitor 24 is charged from the DC power source 1 through the primary winding n1 and the secondary winding n2, so that the input current ripple is reduced. Can be reduced. Moreover, since the smoothing capacitor 24 is charged not only through the secondary winding n2 but also through the primary winding n1 when releasing the energy of the transformer 21 when the switching element 22 is off, the secondary winding of the transformer 21 is charged. There is an advantage that the number of turns of n2 can be reduced and the transformer 21 can be reduced in size.
[0059]
【The invention's effect】
  The invention of claim 1 includes a DC / DC conversion circuit that converts a power supply voltage of a DC power source into a desired DC voltage, and a load circuit that adjusts a DC output of the DC / DC conversion circuit and supplies the DC power to a load. The / DC conversion circuit includes a switching element, a transformer to which the power supply voltage of the DC power supply is applied to the primary winding via the switching element, and a capacitor connected to the secondary winding of the transformer via the rectifying element. And a load circuit and a tertiary winding of a transformer are connected in series via at least an inductor between both ends of the capacitor.A power supply apparatus comprising a control circuit that controls on / off of the switching element to vary the DC output of the DC / DC conversion circuit, and the secondary winding of the tertiary winding of the transformer included in the DC / DC conversion circuit A part of the primary side closed circuit component is connected to the secondary side closed circuit of the transformer, and is also used as an inductance of the secondary side closed circuit including at least the secondary winding and the capacitor. The time constant determined is sufficiently larger than the switching cycle of the switching element by the control circuit.When the switching element is turned on, current flows from the DC power source to the primary winding and energy is stored in the transformer, and the voltage obtained by superimposing the voltage across the capacitor on the voltage generated in the tertiary winding causes the inductor to When the switching element is turned off, the energy stored in the transformer is discharged from the secondary winding to charge the capacitor, and a DC voltage is applied from the capacitor to the load circuit via the tertiary winding. Supplied. In this way, a DC voltage is supplied to the load circuit both when the switching element is on and off, and in particular, a DC voltage boosted by the transformer boosting action when the switching element is on is supplied to the load circuit. The accumulated energy can be reduced. As a result, it is possible to adjust the output even with a load having a large voltage fluctuation, and to reduce the magnetic flux density of the transformer and to reduce the size of the core.Furthermore, there is an effect that the transformer can be miniaturized by using the tertiary winding also as the secondary winding.
[0063]
  Claim2The invention of claim1In the present invention, one end of the secondary winding of the transformer is connected to one end of the primary winding via the capacitor, and the other end of the primary winding and the other end of the secondary winding are connected via a rectifier element. In this way, a closed circuit on the secondary side is formed, and a load circuit is connected to both ends of a series circuit of the primary and secondary windings of the transformer and the capacitor via at least an inductor, Claim1The same effect as that of the present invention can be obtained.
[0064]
  Claim3The invention of claim1In the present invention, one end of the secondary winding of the transformer is connected to the DC power source via the rectifier element, and the other end of the secondary winding is connected to the DC power source via the capacitor, thereby closing the secondary circuit. And a load circuit is connected to both ends of a series circuit of a secondary winding of the transformer, the capacitor, and a DC power source via an inductor.1The same effect as that of the present invention can be obtained.
[0065]
  Claim4The invention of claim1In this invention, a closed circuit on the secondary side is formed by connecting a series circuit of a rectifier element, the switching element, and the capacitor to both ends of the secondary winding of the transformer, and the secondary winding of the transformer, the capacitor, A load circuit is connected to both ends of a series circuit of switching elements via an inductor, and1The same effect as that of the present invention can be obtained.
[0066]
  Claim5The invention of claim 1 to claim 14The discharge lamp is characterized by the fact that the load described in is used as a discharge lamp, and the output can be adjusted even with a load with large voltage fluctuations, and the core can be miniaturized by reducing the magnetic flux density of the transformer There is an effect that the device can be provided.
[0067]
  Claim6The invention of claim5The load circuit includes an inverter circuit that alternately supplies a direct current output of a DC / DC conversion circuit to supply the discharge lamp to the discharge lamp.5The same effect as that of the present invention can be obtained.
[0068]
  Claim7The invention of claim5 or 6In the invention, the load circuit includes a starting circuit for applying a high starting voltage to the discharge lamp.5 or 6The same effect as that of the present invention can be obtained.
[Brief description of the drawings]
[Figure 1]Reference example of the present inventionFIG.
FIG. 2 is an operation waveform diagram in the case of the current boundary mode.
FIG. 3 is an operation waveform diagram in the case of the current continuous mode.
FIG. 4 Embodiment1FIG.
FIG. 5 is an operation waveform diagram in the case of the current boundary mode.
FIG. 6 is an operation waveform diagram in the case of the current continuous mode.
FIG. 7 is an embodiment.2FIG.
FIG. 8 is an embodiment.3FIG.
FIG. 9 is an operation waveform diagram in the case of the current boundary mode.
FIG. 10 is an operation waveform diagram in the case of the current continuous mode.
FIG. 11 is a schematic circuit configuration diagram showing another configuration of the above.
FIG. 12 is an embodiment.4FIG.
FIG. 13 is a schematic circuit configuration diagram showing a first conventional example.
FIG. 14 is a schematic circuit configuration diagram showing a second conventional example.
FIG. 15 is an operation waveform diagram in the case of the current boundary mode.
FIG. 16 is an operation waveform diagram in the case of the current continuous mode.
[Explanation of symbols]
1 DC power supply
2 DC / DC conversion circuit
5 Load circuit
6 Control circuit
21 transformer
n1 Primary winding
n2 secondary winding
n3 tertiary winding
22 Switching element
23 Diode
24 Smoothing capacitor
27 Inductor

Claims (7)

A DC / DC conversion circuit that converts a power supply voltage of a DC power supply into a desired DC voltage, and a load circuit that adjusts the DC output of the DC / DC conversion circuit and supplies it to a load, the DC / DC conversion circuit switching An element, a transformer to which a power supply voltage of a DC power supply is applied to the primary winding via the switching element, and a capacitor connected to the secondary winding of the transformer via the rectifier element, between both ends of the capacitor A power supply device in which a load circuit and a tertiary winding of a transformer are connected in series via at least an inductor, and a control circuit that varies the DC output of a DC / DC conversion circuit by controlling on / off of the switching element. The DC / DC converter circuit has a transformer tertiary winding also used as a secondary winding, and a part of the primary closed circuit component is connected to the secondary closed circuit of the transformer. Is, the power supply apparatus characterized by being sufficiently larger than the switching period of the switching element by the control circuit the time constant determined by the secondary side of the closed circuit inductance and the capacitor comprising at least two windings. One end of the secondary winding of the transformer is connected to one end of the primary winding via the capacitor, and the other end of the primary winding and the other end of the secondary winding are connected via a rectifier element 2 2. A closed circuit on the secondary side is formed, and a load circuit is connected to both ends of a series circuit of the primary and secondary windings of the transformer and the capacitor via at least an inductor. Power supply. A secondary side closed circuit is formed by connecting one end of the secondary winding of the transformer to a DC power source via a rectifier and connecting the other end of the secondary winding to the DC power source via the capacitor. power apparatus according to claim 1, characterized in that through the inductor formed by connecting the load circuit across the transformer secondary winding and the capacitor and the series circuit of the DC power supply. A closed circuit on the secondary side is formed by connecting a series circuit of the rectifier element, the switching element and the capacitor to both ends of the secondary winding of the transformer, and the secondary winding of the transformer, the capacitor and the switching element are connected in series. 2. The power supply device according to claim 1, wherein a load circuit is connected to both ends of the circuit via inductors . A discharge lamp lighting device, wherein the load described in claim 1 is a discharge lamp . 6. The discharge lamp lighting device according to claim 5 , wherein the load circuit includes an inverter circuit that alternately supplies a direct current output of a DC / DC conversion circuit and supplies the alternating current to the discharge lamp . The discharge lamp lighting device according to claim 5 , wherein the load circuit includes a starting circuit that applies a high voltage for starting to the discharge lamp.

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