JP2005073431A - Power supply device and discharge lamp lighting device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-sized, low-cost power supply device, wherein even if the state of load voltage, load current, or the like largely fluctuates, surges can be suppressed to be constant with sureness and power can be transmitted to a load more effectively, and to provide a discharge lamp lighting device. <P>SOLUTION: The snubber circuit of a DC/DC converter is comprised of a capacitor 7 one end of which is connected with the connecting node between a primary winding 2a and a switching element 4, a reactor 9 connected between the other end of the capacitor 7 and the connecting node between the switching element 4 and a direct-current voltage source 1, a diode 8 whose anode is connected with the connecting node between the other end of the capacitor 7 and the reactor 9, a capacitor 10 connected between the cathode of the diode 8 and the connecting node between the switching element 4 and the direct-current voltage source 1, and a diode 11 whose anode is connected with the connecting node between the diode 8 and the capacitor 10. The cathode of the diode 11 is connected with the connecting node between a capacitor 6 and a load circuit 12. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a power supply circuit that converts the output of a DC voltage source to supply it to a load, and a discharge lamp lighting device.

Some conventional DC / DC converters convert the output of a DC voltage source by operating a switching element connected to a transformer at a high frequency, and some surge voltage generated in the switching element due to a leakage inductance of the transformer. Have been made to suppress the loss and reduce the loss generated in the switching element. A common matter of these prior arts is that the energy of the surge generated in the switching element is mainly returned to the power supply side and regenerated. (For example, see Patent Document 1)
JP 2002-101657 A

  However, in the above conventional configuration, as described above, the energy of the surge generated in the switching element is mainly fed back to the power source side and regenerated, so that it is insufficient in terms of effectively transmitting power to the load circuit. was there. Also, when a snubber circuit is provided, if the state of load voltage, load power, etc. fluctuates greatly, it will be difficult to always obtain the ideal snubber circuit operation, resulting in an excessive surge occurring in the switching element. was there.

  Furthermore, since an active switching element and a large and expensive part such as a transformer are required, there is a problem of hindering downsizing and cost reduction of the apparatus.

  The present invention has been made in view of the above reasons, and its purpose is to always be able to reliably suppress surges even when the state of load voltage, load power, etc. fluctuates greatly, and to supply power to the load. It is an object of the present invention to provide a compact and low-cost power supply device and a discharge lamp lighting device that transmit more effectively.

  To achieve the above object, the invention of claim 1 is directed to a DC voltage source, a series circuit of a primary winding of a transformer connected between both ends of the DC voltage source and a switching element, and when the switching element is OFF. A first diode for supplying a positive potential output obtained by rectifying the voltage generated in the transformer to the load circuit, a first capacitor having one end connected to a midpoint of connection between the primary winding and the switching element, The other end of the capacitor-a reactor connected between the connection midpoints of the switching element and the DC voltage source; a second diode having an anode connected to the midpoint of connection between the other end of the first capacitor and the reactor; The cathode of the diode in FIG. 2-a second capacitor connected between the connection midpoints of the switching element and the DC voltage source, and an anode connected at the midpoint of connection between the second diode and the second capacitor And a third diode, characterized in that the cathode of the third diode is connected to the positive potential input side of the load circuit.

  According to the present invention, even when the state of load voltage, load power, etc. fluctuates greatly, it is possible to always reliably suppress surges, transmit power more effectively to the load, Cost can be configured.

  The invention of claim 2 loads a DC voltage source, a series circuit of a transformer primary winding and a switching element connected between both ends of the DC voltage source, and a positive potential output obtained by rectifying the voltage generated in the transformer. A first capacitor supplied to the circuit, a first capacitor having one end connected to a midpoint of connection between the primary winding and the switching element, and the other end of the first capacitor-connection between the switching element and the DC voltage source A reactor connected between the midpoints; and a second diode having an anode connected to the midpoint of connection between the other end of the first capacitor and the reactor; and the cathode of the second diode is connected to the positive potential input side of the load circuit It is characterized by being connected to.

  According to the present invention, even when the state of the load voltage, load power, etc. fluctuates greatly, it is possible to always reliably suppress surge and to transmit power more effectively to the load. Further, it can be configured in a smaller size and at a lower cost.

  According to a third aspect of the present invention, in the first or second aspect, the transformer is an autotransformer.

  According to this invention, further miniaturization and cost reduction can be achieved by using an autotransformer.

  The invention according to claim 4 is characterized in that the load circuit of the power supply device according to any one of claims 1 to 3 uses a discharge lamp as a load.

  According to this invention, it is possible to provide a discharge lamp lighting device that exhibits the same effect as any one of the first to third aspects.

  As described above, in the present invention, even when the state of load voltage, load power, etc. fluctuates greatly, it is possible to always suppress surge reliably and transmit power more effectively to the load. In addition, there is an effect that it can be configured in a small size and at a low cost.

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

(Embodiment 1)
The configuration of the power supply device of this embodiment is shown in FIG. A series circuit of the primary winding 2a of the transformer 23a and the switching element 4 is connected between the positive electrode and the negative electrode of the DC voltage source V1, and the secondary rectifier diode 5 is connected to one end of the secondary winding 3a of the transformer 23a. The cathode is connected, the anode of the diode 5 is connected to the midpoint of connection between the switching element 4 and the DC voltage source 1, and a secondary smoothing capacitor is connected to the series circuit of the secondary winding 3 a and the secondary rectifier diode 5. 6 and the load circuit 12 are connected in parallel.

  And as a snubber circuit part provided in the DC / DC converter part comprised as mentioned above, one end of the capacitor 7 is connected to the connection middle point (point a) between the primary winding 2a and the switching element 4, and the capacitor A reactor 9 is connected between the other end of 7 and a connection midpoint between the switching element 4 and the DC voltage source 1, and an anode of a diode 8 is connected to a connection midpoint between the other end of the capacitor 7 and the reactor 9, A capacitor 10 is connected between the cathode-switching element 4 of the diode 8 and the midpoint of connection between the DC voltage source 1, and an anode of the diode 11 is connected to the midpoint of connection between the diode 8 and the capacitor 10. Is connected to the midpoint of connection between the capacitor 6 and the load circuit 12. Each winding direction of the primary winding 2a and the secondary winding 3a of the transformer 23a is as shown in the figure.

  First, the operation of the DC / DC converter unit serving as the main circuit of this embodiment will be described. When the switching element 4 is on, a current I4 flows from the DC voltage source 1 through the primary winding 2a of the transformer 23a and the switching element 4 (see FIG. 2A), and energy is stored in the transformer 23a. . When the switching element 4 is turned off, the energy stored in the transformer 23a is discharged as a current from the secondary winding 3a to the capacitor 6 through the diode 5, and the capacitor 6 smoothes the energy released by the transformer 23a and supplies it to the load circuit 12. Supply voltage. The polarity of the transformer 23a and the diode 5 is such that the load voltage Vo at both ends of the load circuit 12 is a positive potential. Therefore, the load voltage Vo is higher than the negative electrode (ground potential) of the DC voltage source 1.

  Next, the operation of the snubber circuit section will be described using the operation waveforms of the respective sections at normal load shown in FIGS. Assuming that the turns ratio of the transformer 23a is n and the transformer 23a is an ideal transformer (the coupling between the primary and secondary is 1), when the switching element 4 is turned off, the primary winding 2a A voltage of Vo / n (load voltage / turns ratio) is generated. However, since the transformer 23a actually has a leakage inductance and is not an ideal transformer, a voltage exceeding Vo / n is generated in the primary winding 2a, and the voltage exceeding Vo / n is generated by the DC voltage source 1. The voltage Vi and the polarized voltage are applied to the switching element 4 (point a) as a surge voltage.

  Therefore, in the present embodiment, the switching element 4 that is on between the times t0 and t1 and off at the times t1 to t3 has the voltage V4 at the point a due to the leakage inductance of the transformer 23a when the switching element 4 is off (FIG. 2 (d)). When an excessive voltage is to be generated at time (time t1 to t2), this energy is a by a closed circuit including a capacitor 7, a diode 8, and a capacitor 10 connected between both ends of the switching element 4 connected to the point a. From the point, current I7 (FIG. 2B) is temporarily stored in capacitor 7 (FIG. 2C) and capacitor 10. When the switching element 4 is on, the energy stored in the capacitor 7 is transferred to the reactor 9 by a closed circuit including the capacitor 7, the switching element 4, and the reactor 9. The energy transferred to the reactor 9 charges the capacitor 10 via the diode 8 when the switching element 4 is off.

  With the above operation, the voltage V10 is generated in the capacitor 10. Incidentally, the capacitor 6 is connected in parallel to the capacitor 10 via the diode 11, and when the load voltage Vo falls below the voltage V 10, the charge of the capacitor 10 charges the capacitor 6 and supplies power to the load circuit 12. Become. At this time, a charging current I11 (FIG. 2 (e)) flows from the capacitor 10 to the capacitor 6 via the diode 11. By this operation, the voltage V10 is maintained at substantially the same value as the load voltage Vo. Further, the voltage V7 generated in the capacitor 7 is basically kept at substantially the same value as the voltage Vi.

  As a result of the above operation, the surge voltage generated in the switching element 4 can be kept below about the sum of V10 (≈Vo) and V7 (≈Vi). That is, the voltage V4 when the switching element 4 is turned off is kept substantially below Vo + Vi, and an excessive voltage is not applied to the switching element 4. Therefore, it is possible to select an element with lower withstand voltage and better characteristics. Loss reduction in the power supply device, size reduction, and cost reduction are possible. 3A to 3F show the operation waveforms of the respective parts when the load is relatively heavy, which are substantially the same as the waveforms at the normal load shown in FIGS. 2A to 2F, and the load voltage Even when the state of load and load power fluctuates greatly, the same effect as described above can be obtained.

  Furthermore, in the present embodiment, all of the energy that originally becomes a surge recovered by the snubber circuit unit is directly supplied to the load side, and more than the conventional snubber circuit unit that regenerates all or much of the recovered energy to the power source side. Efficiency can be improved. In particular, a great effect can be obtained when switching a large current such as during heavy load.

(Embodiment 2)
The configuration of the power supply device of the present embodiment is shown in FIG. 4, and the DC / DC converter that is the main circuit with respect to the configuration of the first embodiment is configured to be a boost type configuration using an autotransformer 23 b, and the DC voltage A series circuit of the primary winding 2b of the transformer 23b and the switching element 4 is connected between the positive electrode and the negative electrode of the source V1, and an output terminal of the secondary winding 3b connected in series with the primary winding of the transformer 23b An anode of the secondary rectifying diode 5 is connected, and a secondary smoothing capacitor 6 and a load circuit 12 are respectively connected between the cathode-switching element 4 of the secondary rectifying diode 5 and the DC voltage source 1. Connected.

  As in the first embodiment, the snubber circuit unit provided in the DC / DC converter unit configured as described above has one end of the capacitor 7 at the connection midpoint (point a) between the primary winding 2b and the switching element 4. A reactor 9 is connected between the other end of the capacitor 7 and the connection midpoint between the switching element 4 and the DC voltage source 1, and the anode of the diode 8 is connected at the connection midpoint between the other end of the capacitor 7 and the reactor 9. Is connected, a capacitor 10 is connected between the cathode-switching element 4 of the diode 8 and the midpoint of connection between the DC voltage source 1, and an anode of the diode 11 is connected at the midpoint of connection between the diode 8 and the capacitor 10. The cathode of the diode 11 is connected to the midpoint of connection between the capacitor 6 and the load circuit 12. Each winding direction of the primary winding 2b and the secondary winding 3b of the transformer 23b is as shown in the figure.

  First, the operation of the DC / DC converter unit serving as the main circuit of this embodiment will be described. When the switching element 4 is on, a current flows from the DC voltage source 1 through the primary winding 2b of the transformer 23b and the switching element 4, and energy is stored in the transformer 23b. When the switching element 4 is turned off, the energy stored in the transformer 23b is discharged as a current from the primary winding 2b and the secondary winding 3b to the capacitor 6 via the diode 5, and the capacitor 6 smoothes the energy released by the transformer 23b. Then, a voltage is supplied to the load circuit 12. Since the DC voltage source 1 is added to the current discharge loop during the above operation, the DC / DC converter of this embodiment is a step-up type.

  Next, the operation of the snubber circuit unit will be described. Assuming that the turns ratio of the transformer 23b is n and the transformer 23b is an ideal transformer (the coupling between the primary and secondary is 1), when the switching element 4 is turned off, the primary winding 2b Voltage of (Vo−Vi) / (n + 1) is generated. However, since the transformer 23b actually has a leakage inductance and is not an ideal transformer, a voltage exceeding (Vo−Vi) / (n + 1) is generated in the primary winding 2a, and this (Vo−Vi) / A voltage obtained by applying a voltage exceeding (n + 1) to the voltage Vi of the DC voltage source 1 is applied to the switching element 4 (point a) as a surge voltage.

  The specific operation of the snubber circuit unit of the present embodiment is the same as that of the first embodiment, and the surge voltage can be kept below a predetermined voltage, and an excessive voltage is not applied to the switching element 4. Therefore, it is possible to select an element having a lower withstand voltage and better characteristics, and it is possible to reduce the loss and reduce the size of the power supply device.

  In addition, all of the energy that originally becomes a surge, recovered by the snubber circuit, is directly supplied to the load side, and the efficiency is improved compared to the conventional snubber circuit that regenerates all or much of the recovered energy to the power supply side. be able to. In particular, a great effect can be obtained when switching a large current such as during heavy load.

(Embodiment 3)
The configuration of the power supply device of this embodiment is shown in FIG. In contrast to the configuration of the first embodiment, the capacitor 10 and the diode 11 in the snubber circuit section are eliminated, and the cathode of the diode 8 is directly connected to the high voltage side of the secondary smoothing capacitor 6, that is, the output of the DC / DC converter. The charging current I8 flows to the capacitor 6 via the diode 8. Therefore, the same effects as those of the first embodiment can be obtained, and further downsizing and cost reduction can be achieved.

  The snubber circuit unit of this embodiment can also be applied to the second embodiment in which the DC / DC converter has an autotransformer configuration.

(Embodiment 4)
In the present embodiment, as shown in FIG. 6, a full-bridge type inverter circuit 20 in which the load circuit 12 of the third embodiment is configured by switching elements 13 to 16, and a discharge lamp 17 that is lit with a rectangular wave output of the inverter circuit 20. The discharge lamp lighting device includes an igniter 18 that is connected between the inverter circuit 20 and the discharge lamp 17 and starts the discharge lamp 17.

  The inverter circuit 20 is configured by connecting a series circuit of the switching elements 13 and 14 and a series circuit of the switching elements 15 and 16 in parallel. The switching elements 13 and 16 and the switching elements 14 and 15 are alternately connected, for example, about 400 Hz. By switching at a low frequency, the output of the DC / DC converter is converted into an alternating output, and the connection midpoint of the switching elements 13 and 14 and the connection midpoint of the switching elements 15 and 16 are connected via the igniter 18 to the discharge lamp. 17, the discharge lamp 17 is turned on in a rectangular wave alternating current.

  The igniter 18 is for starting the discharge lamp 17 with dielectric breakdown. Before the discharge lamp 17 such as a metal halide lamp reaches a lighting state (referred to as starting here), the impedance takes a very large value, and in order to start in such a state, for example, about several kV to about 20 kV This voltage must be applied to the discharge lamp 17 to cause the discharge lamp 17 to break down. The general igniter 18 applies a pulsed high voltage to the discharge lamp 17 using the boosting effect of the transformer.

  By the way, in the case of mercury-free metal halide lamps currently being developed for automobile headlamps, in order to obtain a quick rise in luminous flux necessary for automobile headlamps, a few seconds after lighting for a rating of 35 W Approximately three times as much power is required, and the load voltage Vo (lamp voltage) at that time is lower than that during steady lighting due to the characteristics of the metal halide lamp. This embodiment is particularly suitable because it can always reliably suppress surges even when the state of load voltage, load power, etc. fluctuates greatly with respect to such a load.

  In addition, the load circuit 12 including the discharge lamp 17, the igniter 18, and the inverter circuit 20 of the present embodiment may be applied to the first and second embodiments, and the same effect as described above can be obtained as a discharge lamp lighting device.

It is a figure which shows the structure of Embodiment 1 of this invention. (A)-(f) It is a figure which shows the operation | movement waveform of each part at the time of normal load same as the above. (A)-(f) It is a figure which shows the operation | movement waveform of each part at the time of heavy load same as the above. It is a figure which shows the structure of Embodiment 2 of this invention. It is a figure which shows the structure of Embodiment 3 of this invention. It is a figure which shows the structure of Embodiment 4 of this invention.

Explanation of symbols

1 DC voltage source 2a Primary winding 3a Secondary winding 4 Switching element 5 Secondary rectifier diode 6 Secondary smoothing capacitor 7, 10 Capacitor 8, 11 Diode 9 Reactor 12 Load circuit 23a Transformer

Claims (4)

Loaded with a DC voltage source, a series circuit of a transformer primary winding connected between both ends of the DC voltage source and a switching element, and a positive potential output obtained by rectifying the voltage generated in the transformer when the switching element is off A first capacitor supplied to the circuit, a first capacitor having one end connected to a midpoint of connection between the primary winding and the switching element, and the other end of the first capacitor-connection between the switching element and the DC voltage source A reactor connected between the midpoints, a second diode having an anode connected to the midpoint of connection between the other end of the first capacitor and the reactor, a cathode-switching element of the second diode, and a DC voltage source being connected A second capacitor connected between the points, and a third diode having an anode connected to a midpoint of connection between the second diode and the second capacitor. Power apparatus characterized by connecting the cathode to the positive potential input side of the load circuit. A DC voltage source, a series circuit of a primary winding of a transformer and a switching element connected between both ends of the DC voltage source, and a first output for supplying a positive potential output obtained by rectifying a voltage generated in the transformer to a load circuit A first capacitor having one end connected to a connection point between the diode, the primary winding and the switching element; and a reactor connected between the other end of the first capacitor and the connection point between the switching element and the DC voltage source. And a second diode having an anode connected to a midpoint of connection between the other end of the first capacitor and the reactor, the cathode of the second diode being connected to the positive potential input side of the load circuit, Power supply. 3. The power supply device according to claim 1, wherein the transformer is an autotransformer. 4. A discharge lamp lighting device, wherein the load circuit of the power supply device according to claim 1 uses a discharge lamp as a load.

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