JP2009231107A - Power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power supply device for reducing a switching loss and noises of switch elements while reducing the number of the switch elements. <P>SOLUTION: The power supply device includes: a voltage generating circuit 13 for turning on/off a DC power supply Vin to generate pulse voltage; a first AC voltage generating circuit 1a having a first switch means Q2 and connected to a position where the pulse voltage generated by the voltage generating circuit is applied, for generating first AC voltage of positive/negative unsymmetrical waveform with the on/off operation of the first switch means and outputting it to one end of each of loads 7-1 to 17-n; and a second AC voltage generating circuit 1b having a second switch means Q4 and connected to a position where the pulse voltage generated by the voltage generating circuit is applied, for generating second AC voltage of a positive/negative unsymmetrical waveform with the on/off operation of the second switch means and outputting it to the other end of each of the loads. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a DC power supply device that converts a DC voltage to another DC voltage via a transformer, and a power supply device that includes an AC power supply device that converts a DC voltage to an AC voltage via a transformer, and in particular, loads an AC voltage as a load. The present invention relates to a technique for lighting a discharge lamp by supplying it to the discharge lamp.

  The AC power supply device converts a DC voltage into an AC voltage via a transformer, and can drive a load with the AC voltage. As an example of a device in which a load is connected to the AC power supply device, a discharge lamp lighting device that lights a cold cathode discharge lamp as a load with an AC voltage is known.

  A cold cathode discharge lamp (CCFL: Cold Cathode Fluorescent Lamp) is generally lit when an AC power supply device is applied with a voltage of several tens of kHz to several hundreds of thousands to several hundreds of volts. There is also a fluorescent tube called an external electrode fluorescent lamp (EEFL). The external electrode fluorescent lamp and the cold cathode discharge lamp have different electrode structures, there is almost no difference, and the light emission principle is the same as that of the cold cathode discharge lamp. For this reason, the AC power supply device for lighting the external electrode fluorescent lamp and the cold cathode discharge lamp is the same in principle. For this reason, the following description will be made using a cold cathode discharge lamp (abbreviated as a discharge lamp).

  The discharge lamp and the AC power supply device are used for a liquid crystal TV, a liquid crystal monitor, a lighting device, a liquid crystal display device, a signboard, and the like. The characteristics required for the AC power supply device are: (a) the AC voltage frequency is about 50 kHz; (b) the voltage applied to the discharge lamp is an AC voltage and has a positive / negative symmetrical waveform.

  Regarding (a), the voltage frequency applied to the discharge lamp is generally about 10 kHz to 100 kHz. This is determined by the user in consideration of various characteristics such as the luminance characteristics and efficiency characteristics of the discharge lamp and the luminance characteristics when the discharge lamp is incorporated in a set. The AC power supply device is driven at a determined frequency or a frequency in the vicinity thereof. For this reason, it is often impossible to set or change the frequency due to the convenience of the AC power supply device. Since liquid crystal TVs, liquid crystal monitors, lighting devices, and the like are often used in the vicinity of approximately 50 kHz, hereinafter, a 50 kHz AC power supply device is used.

  As for (b), generally, the voltage applied to the discharge lamp is an alternating voltage and needs to have a positive and negative symmetrical waveform. The discharge lamp has a glass tube shape, and mercury, a rare gas, or the like is sealed inside. Light is emitted even when a DC voltage is applied to the discharge lamp. However, the internal mercury is shifted to one side, and the brightness at both ends of the discharge lamp gradually becomes different, so the life is remarkably shortened. For this reason, an AC voltage is applied to the discharge lamp. However, even if an AC voltage is used, if there is a difference between positive and negative voltage waveforms, the distribution of mercury may be biased. For this reason, it is required to apply a positive / negative symmetrical waveform. Ideally, a sine wave or a trapezoidal wave is good, and there are many application systems that actually apply a sine wave voltage.

  In addition, a liquid crystal TV or the like has various signal systems such as video processing signals and audio processing signals, and their frequencies and the driving frequency of the AC voltage interfere with each other, which may adversely affect images and sounds. For this reason, it is often required to operate the drive frequency of the AC voltage at a constant frequency that does not cause interference.

  FIG. 4 shows a circuit configuration diagram of a discharge lamp lighting device employing a conventional non-resonant half bridge circuit. In this discharge lamp lighting device, a DC voltage of a DC power source Vin is switched based on gate signals Q1g and Q2g shown in FIG. 5 by switching elements Q1 and Q2 made of MOSFETs or the like to generate a rectangular wave voltage, and a reactor L1 and a capacitor A sine wave voltage that is symmetric with respect to C2 is converted to a desired voltage value by the transformer T1, and the voltage Vout is output from the capacitor C2. According to this, since the sine wave voltage Vout having positive and negative symmetry can be easily obtained by the two switch elements, it is advantageous in terms of cost.

  Next, the operation of the discharge lamp lighting device will be described according to the timing chart shown in FIG. When the switch element Q1 is turned on from time t11 to time t12, the capacitor C1 is charged and a current flows through the primary winding P1 of the transformer T1. From time t13 to time t14, when the switch element Q2 is turned on, the capacitor C1 is discharged, and a current flows in the reverse direction through the primary winding P1 of the transformer T1. Thereby, an alternating current flows through the primary winding P1.

  In the period from time t12 to time t13 and from time t14 to time t15, the current flowing through the primary winding P1 is mainly due to the series-parallel resonance action of the capacitance components of the capacitors C1 and C2 and the inductance component of the primary winding P1. Oscillates, and a period in which the diodes D1 and D2 are conductive occurs. The currents flowing on the negative side in the current waveforms Q1i and Q2i are the currents flowing in the diodes D1 and D2, respectively. Here, focusing on time t11, the switching element Q1 is turned on when the diode D2 is conducting. Since the diode has a storage effect, the diode passes a current in the opposite direction for a very short period. That is, a short-circuit current flows from the switch element Q1 to the switch element Q2. The amount and time of the short-circuit current are mainly determined by the reverse recovery time characteristics of the diode D2. If this time is a short diode, the short-circuit current can be reduced, but in principle it is not zero. That is, a switching loss occurs at the moment when the switch element Q1 is turned on at time t11.

  Similarly, at time t13, a switching loss occurs at the moment when the switching element Q2 is turned on due to the reverse recovery time characteristic of the diode D1. Moreover, since a short circuit current flows, it is disadvantageous also in terms of noise. That is, each switch element Q1, Q2 performs a hard switching operation.

  FIG. 6 shows a circuit configuration diagram of a discharge lamp lighting device adopting a conventional resonance type full bridge circuit. In this discharge lamp lighting device, the DC voltage of the DC power source Vin is switched based on the gate signals Q1g to Q4g shown in FIG. 7 by the switching elements Q1 to Q4 to generate a rectangular wave voltage, and the filter of the reactor L1 and the capacitor C2 A positive and negative sine wave voltage is obtained by the action, converted into a desired voltage value by the transformer T1, and the voltage Vout is output from the capacitor C2.

  As shown in the timing chart of FIG. 7, the switch element Q1 and the switch element Q2 are complementarily turned on / off by gate signals Q1g and Q2g having a predetermined dead time. The switch element Q3 and the switch element Q4 are complementarily turned on / off by gate signals Q3g and Q4g having a predetermined dead time. The first arm gate signals Q1g and Q2g by the switch elements Q1 and Q2 and the second arm gate signals Q3g and Q4g by the switch elements Q3 and Q4 have a phase difference of 180 degrees. In FIG. 7, Q1v to Q4v are drain-source voltages of the switch elements Q1 to Q4, Q1i to Q4i are drain currents of the switch elements Q1 to Q4, and VT is a voltage across the series circuit of the primary winding P1 and the reactor L1. , Vs1 is the voltage across the secondary winding S1.

  Since the circuit shown in FIG. 6 performs the resonance operation according to the timing chart shown in FIG. 7, no switching loss occurs when each switch element is turned on. In addition, since a positive and negative sine wave voltage is obtained as an output voltage, it is used as an AC power supply that emphasizes efficiency characteristics or noise characteristics. However, since four switch elements are required, it is disadvantageous in terms of cost.

  FIG. 8 shows an arrangement example 1 of a conventional discharge lamp lighting device. In FIG. 8, it is the figure which looked at liquid crystal TV which is a discharge lamp lighting device from the back side. Discharge lamps 7-1 to 7-n are provided on the front side of the panel 13a. The inverter board 11a is arranged near the right side of the panel 13a, and the discharge lamp 7-1 is connected via the connectors 15a and 15b and the electric wires 9a and 9b. Connect to ~ 7-n. FIG. 9 shows a circuit example 1 of the arrangement example 1 of the discharge lamp lighting device shown in FIG.

  However, in the circuit example 1 of FIG. 9, the circuit cannot be configured when the panel size, that is, the discharge lamp becomes longer than a certain length. This is because the longer the discharge lamp, the higher the impedance of the discharge lamp, so that a higher output voltage is required for the transformer T1. The higher the output voltage, the more difficult the insulation structure and safety measures of the transformer, and the larger the transformer and the higher the cost. In general, the output voltage is about 2000 to 2500 Vrms.

  When the discharge lamp is long, the output voltage of each of the transformers T1 and T2 can be halved by operating the transformer T1 and the transformer T2 in opposite phases using the discharge lamp lighting device shown in FIG. it can. FIG. 11 is a diagram showing an arrangement example 2 of the circuit example 2 of the discharge lamp lighting device shown in FIG. However, in FIG. 11, the output wiring of the secondary winding S2 of the transformer T2 becomes long. Since the output wiring has a high voltage and a high frequency, the longer the output wiring, the higher the leakage current and the lower the efficiency. It also becomes a source of noise.

  A circuit example 3 shown in FIG. 12 solves the problem of the arrangement example 2 shown in FIG. In the discharge lamp lighting device shown in FIG. 12, inverter boards 11d and 11e are arranged at both ends of the panel 13a, and the AC voltage of the AC power supply device mounted on the inverter board 11d and the AC of the AC power supply device mounted on the inverter board 11e. The voltage is operated at a phase difference of 180 degrees and applied to the discharge lamps 7-1 to 7-n at both ends. The control circuit 10b switches the switch elements Q1 to Q4 to output a positive / negative sine wave voltage to the secondary winding S1 of the transformer T1. The control circuit 10c provides a 180-degree phase difference to the switching elements Q1 to Q4 to switch the switching elements Q5 to Q8 and outputs a positive / negative sine wave voltage to the secondary winding S2 of the transformer T2. According to this, since the high-voltage and high-frequency wiring can be arranged in the shortest distance, it is often used particularly in a large liquid crystal panel.

For example, there is Patent Document 1 as a conventional technique.
JP-A-8-162280

  However, in the circuit example 3 of FIG. 12, two AC power supply devices are necessary, and therefore, when a full bridge circuit is applied, eight switch elements are necessary. In addition, the half-bridge circuit can be applied to make four switching elements. However, since the hard switching operation is performed as described above, it is disadvantageous in terms of switching loss and noise. Further, in the circuit example 3 shown in FIG. 12, since two control circuits of the control circuit 10b and the control circuit 10c are provided and it is necessary to synchronize between the control circuits, the number of control circuits increases and the cost becomes high.

  In addition to the AC power supply device, the entire system such as a liquid crystal TV needs a DC power supply device for signal processing and audio output.

  The subject of this invention is providing the power supply device which can reduce the switching loss of a switch element, and noise while reducing the number of switch elements by combining an AC power supply device and a DC power supply device.

  In order to solve the above-mentioned problems, the invention of claim 1 includes a voltage generation circuit that generates a pulse voltage by intermittently connecting a DC power supply, and a first switch means, and the pulse voltage generated by the voltage generation circuit is A first AC voltage generating circuit connected to a position to be applied, generating a first AC voltage having a positive / negative asymmetric waveform by turning on / off the first switch means, and outputting the first AC voltage to one end of the load; and second switch means And connected to a position where a pulse voltage generated by the voltage generating circuit is applied, and generates a second AC voltage having a positive / negative asymmetric waveform by turning on / off the second switch means and outputs the second AC voltage to the other end of the load. And a second AC voltage generation circuit.

  According to a second aspect of the present invention, there is provided the power supply device according to the first aspect, further comprising a first control circuit that alternately turns on the first switch means and the second switch means in synchronization with the pulse voltage. And

  According to a third aspect of the present invention, in the power supply device according to the second aspect, the first control circuit turns off the first switch means and the second switch means during a period in which the pulse voltage is applied. To do.

  According to a fourth aspect of the present invention, in the AC power supply device according to any one of the first to third aspects, the first AC voltage generating circuit is induced with a primary winding connected to the first switch means. A first transformer having a secondary winding for outputting a voltage to be generated as the first AC voltage, and the second AC voltage generation circuit is induced with the primary winding connected to the second switch means. A second transformer having a secondary winding for outputting a voltage to be output as the second AC voltage.

  According to a fifth aspect of the present invention, in the power supply device according to the fourth aspect, the first AC voltage generation circuit includes a first capacitor connected between a secondary winding of the first transformer and one end of the load. And the second AC voltage generation circuit includes a second capacitor connected between the secondary winding of the second transformer and the other end of the load.

  According to a sixth aspect of the present invention, in the power supply device according to the fourth aspect, the first AC voltage generation circuit includes a primary of the first transformer between a secondary winding of the first transformer and one end of the load. A leakage inductance between the winding and the secondary winding, and the second AC voltage generation circuit is connected to the primary winding of the second transformer between the secondary winding of the second transformer and the other end of the load. It has a leakage inductance between the winding and the secondary winding.

  According to a seventh aspect of the present invention, there is provided the power supply device according to the first aspect, wherein the voltage generating circuit is connected in series between both electrodes of the DC power source, and a third switch means for generating a pulse voltage by turning on / off, A fourth switch means, and a third winding means or a primary winding of a third transformer connected in parallel to the fourth switch means and a third capacitor, and the third switch means and the fourth switch means A third series resonant circuit to which a pulse voltage generated by on / off is applied; a rectifying / smoothing circuit for rectifying and smoothing a pulse voltage generated in the secondary winding of the third transformer to extract a DC output voltage; and the DC And a second control circuit for alternately turning on and off the third switch means and the fourth switch means based on an output voltage.

  According to an eighth aspect of the present invention, in the power supply device according to the seventh aspect, the first control circuit is configured to synchronize with the third switch means or the fourth switch means in the on state of the second control circuit. The first switch means and the second switch means are alternately turned on / off every other period with respect to the operating frequency of the switch means and the fourth switch means.

  According to a ninth aspect of the present invention, in the power supply device according to the seventh aspect, the first control circuit is configured to synchronize with the third switch means or the fourth switch means in the on state of the second control circuit. The first switch means and the second switch means are alternately turned on / off every other cycle with respect to the operating frequency of the switch means and the fourth switch means, and the first switch means and the second switch means It is characterized by having a function of repeatedly turning on / off of the first switch means and the second switch means completely in an intermittent cycle.

  According to the present invention, the first AC voltage generation circuit receives the pulse voltage of the voltage generation circuit, generates the first AC voltage having a positive / negative asymmetric waveform by turning on / off the first switch means, and outputs it to one end of the load. The second AC voltage generating circuit generates a second AC voltage having a positive / negative asymmetric waveform when the pulse voltage is applied and turns on / off the second switch means and outputs it to the other end of the load. The applied voltage has a positive / negative symmetrical waveform. Accordingly, since the voltage across the load has a positive / negative symmetrical waveform, it is difficult to reduce the life due to the deviation of mercury. Further, by combining the AC power supply device and the DC power supply device, the number of switch elements can be reduced, and the switching loss and noise of the switch elements can be reduced.

  In addition, the first control circuit is synchronized with the turn-on of the third switch means or the fourth switch means, and the first control circuit performs the first operation every other cycle with respect to the operating frequency of the third switch means and the fourth switch means. Since the switch means and the second switch means are alternately turned on / off, the voltage applied to both ends of the load has a positive / negative symmetrical waveform.

  Hereinafter, embodiments of a power supply device of the present invention will be described in detail with reference to the drawings. In the following embodiments, a case where the AC power supply device of the present invention is applied to a discharge lamp lighting device will be described. This discharge lamp lighting device is configured by connecting a discharge lamp as a load to the AC power supply device of the present invention.

  In this example, the load is a discharge lamp, but the load may not be a discharge lamp, and the AC power supply apparatus of the present invention may be applied to other loads.

  1 is a diagram showing a configuration of a power supply device according to a first embodiment of the present invention. The power supply device shown in FIG. 1 includes a DC / DC converter unit 13 and an inverter unit composed of an inverter board 1a and an inverter board 1b arranged at both ends of the panel 3a.

  In the DC / DC converter unit 13, a series circuit of a switch element Q11 made of MOSFET or the like and a switch element Q12 made of MOSFET or the like is connected to both ends of the DC power source Vin. Connected between the drain and source of switch element Q12 is a third series resonant circuit including reactor L10, primary winding P10 of transformer T10, and capacitor C10. A rectifying / smoothing circuit including a diode D10 and a capacitor C11 is connected to both ends of the secondary winding S10 of the transformer T10, and a voltage across the capacitor C10 is supplied to the load 12 as a DC output voltage Vo.

 A control circuit 5a is connected to a connection point between the capacitor C10 and the load 12. The control circuit 5a controls the DC output voltage Vo to be a desired voltage by applying gate signals Q11g and Q12g to the switch elements Q11 and Q12 to turn on and off the switch elements Q11 and Q12.

  The diodes D11 and D12 between the drain and source of the switch elements Q11 and Q12 may be parasitic diodes of the switch elements Q11 and Q12. Reactor L10 may be a leakage inductance between primary winding P10 and secondary winding S10 of transformer T10.

  Next, the operation of the DC / DC converter unit 13 will be described with reference to the timing chart of FIG.

  In FIG. 2, Q11g and Q12g are gate signals of the switch elements Q11 and Q12, Q12v is a drain-source voltage of the switch element Q12, C10i is a current flowing through the capacitor C10, and D10i is a current flowing through the diode D10.

  As shown in FIG. 2, in the period of period 1 / f = T, gate signals Q11g and Q12g are alternately applied from the control circuit 5a to the switch elements Q11 and Q12, and the switch element Q11 and the switch element Q12 have a frequency f. Turn on and off alternately with.

  Note that a dead time during which both the gate signals Q11 and Q12 are at the L level is provided between the gate signal Q11g and the gate signal Q12g in order to prevent the switching elements Q11 and Q12 from being turned on simultaneously.

  When the switching element Q11 is turned on at time t10, the input voltage Vin is applied to the third series resonance circuit including the reactor L10, the primary winding P10 of the transformer T10, and the capacitor C10, and the capacitor C10 is connected to the third series resonance circuit. A current C10i in the charging direction flows. Immediately after the switching element Q11 is turned on, a current flows in a direction in which the capacitor C10 is discharged by a resonance operation.

  Next, when the switch element Q11 is turned off and the switch element Q12 is turned on at time t11, the current C10i flowing through the third series resonance circuit is switched in the direction of discharging the capacitor C10 and is stored in the transformer T10 and the capacitor C10. The discharged energy is discharged to the output through the secondary winding S10. Immediately after the switching element Q12 is turned on, a current flows in the direction of charging the capacitor C10 by the resonance operation.

  As described above, when the switching element Q11 and the switching element Q12 are alternately turned on and off alternately, assuming that the on-duty of the switching element Q11 is Don, the capacitor C10 repeats charging / discharging around the voltage of Vin × Don.

  During the ON period of the switch element Q12, the voltage of the capacitor C10 is discharged to the secondary side of the transformer T10. For this reason, the DC output voltage Vo is approximately Vin × Don × (S10 / P10). That is, the control circuit 5a controls the on-duty of the switch element Q11 and the switch element Q12, thereby adjusting the DC output voltage Vo to a desired voltage.

  Next, the inverter unit will be described. In the inverter board 1a, a series circuit of the capacitor C1, the reactor L1, the primary winding P1 of the transformer T1, and the switch element Q2 is connected between the connection point of the switch element Q11 and the switch element Q12 and the ground. Yes. The regenerative diode D5 has an anode connected to the drain of the switch element Q2 and one end of the primary winding P1, and a cathode connected to a connection point between the switch element Q11 and the switch element Q12 and one end of the capacitor C1. Yes.

  A capacitor C2 is connected in parallel to both ends of the secondary winding S1 of the transformer T1, and one end is commonly connected to a connection point (non-ground potential side) between the secondary winding S1 and the capacitor C2 of the transformer T1. Ballast capacitors Ca1 to Can are connected. The other ends of the ballast capacitors Ca1 to Can are connected to one ends (a side) of the discharge lamps 7-1 to 7-n. An AC voltage having a positive / negative asymmetric waveform is output to the capacitor C2 through the filter of the reactor L1 and the capacitor C2.

  Next, in the inverter board 1b, a series circuit of the capacitor C3, the reactor L2, the primary winding P2 of the transformer T2, and the switch element Q4 is provided between the connection point of the switch element Q11 and the switch element Q12 and the ground. It is connected. The regenerative diode D6 has an anode connected to the drain of the switch element Q4 and one end of the primary winding P2, and a cathode connected to a connection point between the switch element Q11 and the switch element Q12 and one end of the capacitor C3. Yes.

  A capacitor C4 is connected in parallel to both ends of the secondary winding S2 of the transformer T2, and one end is commonly connected to a connection point (non-ground potential side) between the secondary winding S2 and the capacitor C4 of the transformer T2. Ballast capacitors Cb1 to Cbn are connected. The other ends of the ballast capacitors Cb1 to Cbn are connected to the other ends (b side) of the discharge lamps 7-1 to 7-n. An AC voltage having a positive / negative asymmetric waveform is output to the capacitor C4 through the filter of the reactor L2 and the capacitor C4.

  The diodes D2 and D4 between the drains and sources of the switch elements Q2 and Q4 may be parasitic diodes of the switch elements Q2 and Q4. Further, the reactor L1 may be a leakage inductance between the primary winding P1 and the secondary winding S1 of the transformer T1, and the reactor L2 is a circuit between the primary winding P2 and the secondary winding S2 of the transformer T2. It may be a leakage inductance between them. Capacitors C2 and C4 may use parasitic capacitance such as wiring. In that case, the capacitors C2 and C4 can be eliminated or downsized.

  Further, a leakage inductance between the primary winding P1 and the secondary winding S1 of the transformer T1 may be provided between the secondary winding S1 of the transformer T1 and one end of the discharge lamps 7-1 to 7-n. good. Further, a leakage inductance between the primary winding P2 and the secondary winding S2 of the transformer T2 is provided between the secondary winding P2 of the transformer T2 and the other ends of the discharge lamps 7-1 to 7-n. Also good.

  The control circuit 5b alternately turns on / off the switch elements Q2 and Q4 with a predetermined dead time by the gate signals Q2g and Q4g. Further, the control circuit 5b alternately applies the gate signals Q2g and Q4g to the switch elements Q2 and Q4 every other period with respect to the operating frequency of the DC / DC converter unit 13 in synchronization with the switching element Q12 being turned on.

  Next, the operation of the inverter unit will be described with reference to the timing chart of FIG. In FIG. 3, Q11g, Q12g, Q2g, and Q4g are the gate signals of the switch elements Q11, Q12, Q2, and Q4, Q12v, Q2v, and Q4v are the drain-source voltages of the switch elements Q12, Q2, and Q4, and Q11i, Q12i, and Q2i , Q4i are drain currents of the switch elements Q11, Q12, Q2, Q4, Vs1, Vs2 are transformers T1, voltages across the secondary windings S1, S2 of the transformer T2, and Vab is both ends of the discharge lamps 7-1 to 7-n. Is the voltage applied to.

  First, at time t20, when the switching element Q12 is turned on by the gate signal Q12g, a current Q12i flows. In synchronization with this, the gate signal Q2g is applied to the switch element Q2 from the control circuit 5b, the switch element Q2 is turned on, and the current Q2i flows. At this time, since the switch element Q12 is on, the potential at the connection point of the switch elements Q11 and Q12 is approximately 0V. For this reason, no voltage is applied from the outside to the first series resonant circuit of the capacitor C1, the reactor L1, and the primary winding P1 of the transformer T1, and a current flows in a direction in which the electric charge of the capacitor C1 is discharged.

  Next, at time t21, when the switch element Q12 is turned off by the gate signal Q12g and the switch element Q11 is turned on by the gate signal Q11g, a current Q11i flows, and the input voltage Vin passes through the switch element Q11 to the first series resonance circuit. Applied. For this reason, the current flowing through the first series resonance circuit changes in the direction of charging the capacitor C1.

  Next, at time t22, when the gate signal Q2g applied to the switch element Q2 from the control circuit 5b becomes L level, the switch element Q2 is turned off by the gate signal Q2g, and the current flowing through the first series resonance circuit is a diode. The direction is changed to reset the transformer T1 through D5.

  At time t23, when switch element Q11 is turned off by gate signal Q11g and switch element Q12 is turned on again by gate signal Q12g, current Q12i flows. In synchronization with this, the gate signal Q4g is applied to the switch element Q4 from the control circuit 5b, the switch element Q4 is turned on, and the current Q4i flows. At this time, since the switch element Q12 is on, the potential at the connection point of the switch elements Q11 and Q12 is approximately 0V. For this reason, no voltage is applied from the outside to the second series resonance circuit of the capacitor C3, the reactor L2, and the primary winding P2 of the transformer T2, and a current in a direction for discharging the electric charge of the capacitor C3 flows.

  At time t24, when the switch element Q12 is turned off by the gate signal Q12g and the switch element Q11 is turned on by the gate signal Q11g, the input voltage Vin is applied to the second series resonance circuit through the switch element Q11. For this reason, the current flowing through the second series resonance circuit changes in the direction of charging the capacitor C3.

  Next, at time t25, when the gate signal Q4g applied to the switch element Q4 from the control circuit 5b becomes L level, the switch element Q4 is turned off by the gate signal Q4g, and the current flowing through the second series resonant circuit is a diode. The direction is changed to reset the transformer T2 through D6.

  At time t26, when switch element Q11 is turned off by gate signal Q11g, the operation from time t20 to time t25 is repeated.

  As described above, when the switching element Q2 and the switching element Q4 are turned on / off every other period with respect to the operating frequency of the DC / DC converter unit 13, the resonance operation of the first series resonance circuit and the second series resonance circuit results in: As shown in FIG. 3, positive and negative asymmetric voltages such as the secondary winding voltage Vs1 and the voltage Vs2 are generated in the secondary winding S1 of the transformer T1 and the secondary winding S2 of the transformer T2.

  Since the switching elements Q2 and Q4 are alternately turned on / off every other period with respect to the operating frequency of the DC / DC converter unit 13, the secondary winding Vs1 of the transformer T1 and the secondary winding Vs2 of the transformer T2 Is a similar state with a 180 degree phase shift.

  When the secondary winding voltage Vs1 is applied to one end of the discharge lamps 7-1 to 7-n and the secondary winding voltage Vs2 is applied to the other end of the discharge lamps 7-1 to 7-n, the discharge lamp 7 A differential voltage between the secondary winding voltage Vs1 and the secondary winding voltage Vs2 is applied to both ends of −1 to 7-n. That is, the voltage Vab applied across the discharge lamps 7-1 to 7-n has a positive / negative symmetrical waveform. Therefore, since the voltage between both ends of the discharge lamps 7-1 to 7-n has a positive / negative symmetrical waveform, the lifetime is hardly reduced due to the deviation of mercury.

  The control circuit 5b controls the ON width of the switch elements Q2 and Q4 based on the current values of the discharge lamps 7-1 to 7-n, the winding currents of the transformers T1 and T2, the currents of the switch elements Q2 and Q4, and the like. By doing so, the power, current, and luminance of the discharge lamp can be controlled.

  In the power supply device of the first embodiment, when the switch elements Q2, Q4, Q11, and Q12 are turned on, the current flowing through the switch elements Q2, Q4, Q11, and Q12 is zero or a negative current. Current does not flow, and switching loss and switching noise can be reduced.

  The DC / DC converter unit 13 is generally operated at a frequency of about 50 kHz to 100 kHz in consideration of switching loss and transformer iron loss. On the other hand, the frequency of the alternating voltage applied to the discharge lamp is determined to be 30 kHz to 50 kHz according to the request of the panel manufacturer or set manufacturer. In order to operate the DC / DC converter unit 13 at this frequency, it is necessary to increase the core size because of the saturation magnetic flux density of the transformer.

  However, in the power supply device of Example 1, the operating frequency (for example, 100 KHz) of the DC / DC converter unit 13 is twice the frequency of the AC voltage (for example, 50 KHz) applied to the discharge lamps 7-1 to 7-n. Therefore, the core of the transformer T10 can be reduced in size and the cost can be reduced.

  In addition, in a discharge lighting device such as a liquid crystal TV, in order to adjust the luminance widely, not only the effective value of the AC voltage applied to the discharge lamp is controlled, but also the inverter is intermittently oscillated to adjust the luminance of the discharge lamp. Yes. In the power supply device of the first embodiment, in order to perform the intermittent oscillation operation of the inverter, it is only necessary to stop the oscillation of only the switch elements Q2 and Q4, and the operation of the DC / DC converter unit 13 is not affected. Further, the inverter may be operated / stopped.

  As described above, in the power supply device of the first embodiment, the number of switch elements used is the same as that of a conventional full-bridge inverter, resonance operation can be performed, positive and negative sine wave voltages can be applied to both ends of the discharge lamp, and direct current can be applied. Voltage can also be output. For this reason, in the whole DC / DC converter part 13 and the power supply apparatus of an inverter part, while reducing the number of switch elements, the switching loss and noise of a switch element can be reduced.

  In the power supply device of the first embodiment, the DC / DC converter unit 13 controls the duty of the switch element Q11 with a fixed frequency. However, when there is no regulation of the frequency of the AC voltage applied to the discharge lamp, for example, the switch element Q12 The output voltage may be controlled by changing the ON width of the switch element Q11 while fixing the ON period.

  In the first embodiment, power is supplied to the secondary side of the transformers T1 and T2 during the ON period of the switch element Q12. However, power is supplied to the secondary side of the transformers T1 and T2 during the ON period of the switch element Q11. It is good also as a structure to supply.

  In the discharge lamp lighting device according to the first embodiment, there are a plurality of discharge lamps. However, a single discharge lamp may be used.

It is a figure which shows the structure of the discharge lamp lighting device of Example 1 of this invention. It is a timing chart of each part of the discharge lamp lighting device of Example 1 of the present invention. It is a detailed timing chart of each part of the discharge lamp lighting device of Example 1 of the present invention. It is a circuit block diagram of the discharge lamp lighting device which employ | adopted the conventional non-resonance type | mold half bridge circuit. It is a timing chart of each part of the discharge lamp lighting device shown in FIG. It is a circuit block diagram of the discharge lamp lighting device which employ | adopted the conventional resonance type full bridge circuit. It is a timing chart of each part of the discharge lamp lighting device shown in FIG. It is a figure which shows the example 1 of arrangement | positioning of the conventional discharge lamp lighting device. It is a figure which shows the circuit example 1 of the example 1 of arrangement | positioning of the discharge lamp lighting device shown in FIG. It is a figure which shows the circuit example 2 of the conventional discharge lamp lighting device. It is a figure which shows the example 2 of an arrangement | positioning of the circuit example 2 of the discharge lamp lighting device shown in FIG. It is a figure which shows the circuit example 3 of the conventional discharge lamp lighting device.

Explanation of symbols

T1, T2, T10 Transformers P1, P2, P10 Primary windings S1, S2, S10 Secondary windings C1-C4, C10, C11 Capacitors Ca1-Can, Cb1-Cbn Ballast capacitors D1-D8, D10-D12 Diode Q1 ~ Q8, Q11, Q12 Switch elements L1, L2, L10 Reactors Vin, Vina, Vinb DC power supplies 1a, 1b, 11a-11e Inverter boards 3a, 13a Panels 7-1 to 7-n Discharge lamps 5a, 5b, 10b, 10c Control circuit 12 Load 13 DC / DC converter section

Claims (9)

A voltage generation circuit that generates a pulse voltage by intermittently connecting a DC power supply;
Having a first switch means, connected to a position to which a pulse voltage generated by the voltage generation circuit is applied, and generating a first AC voltage having a positive / negative asymmetric waveform by turning on / off the first switch means. A first AC voltage generation circuit that outputs to one end;
Having a second switch means, connected to a position to which a pulse voltage generated by the voltage generation circuit is applied, and generating a second AC voltage having a positive / negative asymmetric waveform by turning on / off the second switch means. A second AC voltage generation circuit that outputs to the other end of
A power supply apparatus comprising:   2. The power supply apparatus according to claim 1, further comprising a first control circuit that alternately turns on the first switch means and the second switch means in synchronization with the pulse voltage.   3. The power supply apparatus according to claim 2, wherein the first control circuit turns off the first switch means and the second switch means during a period in which the pulse voltage is applied. The first AC voltage generation circuit includes a first transformer having a primary winding connected to the first switch means and a secondary winding that outputs an induced voltage as the first AC voltage;
The second AC voltage generation circuit includes a second transformer having a primary winding connected to the second switch means and a secondary winding that outputs an induced voltage as the second AC voltage. The power supply device according to any one of claims 1 to 3, wherein the power supply device is characterized. The first AC voltage generation circuit includes a first capacitor connected between a secondary winding of the first transformer and one end of the load.
5. The power supply device according to claim 4, wherein the second AC voltage generation circuit includes a second capacitor connected between a secondary winding of the second transformer and the other end of the load. The first AC voltage generation circuit has a leakage inductance between the primary winding and the secondary winding of the first transformer between the secondary winding of the first transformer and one end of the load,
The second AC voltage generation circuit has a leakage inductance between the primary winding and the secondary winding of the second transformer between the secondary winding of the second transformer and the other end of the load. The power supply device according to claim 4, wherein: The voltage generation circuit includes:
A third switch means and a fourth switch means connected in series between both poles of the DC power supply and generating a pulse voltage by turning on / off;
A primary winding of a third transformer and a third capacitor connected in parallel to the third switch means or the fourth switch means, and is generated by ON / OFF of the third switch means and the fourth switch means A third series resonant circuit to which a pulse voltage is applied;
A rectifying / smoothing circuit for rectifying and smoothing a pulse voltage generated in the secondary winding of the third transformer and extracting a DC output voltage;
A second control circuit for alternately turning on and off the third switch means and the fourth switch means based on the DC output voltage;
The power supply device according to claim 1, further comprising:   The first control circuit is in one cycle with respect to the operating frequency of the third switch means and the fourth switch means of the second control circuit in synchronization with the turning on of the third switch means or the fourth switch means. 8. The power supply apparatus according to claim 7, wherein the first switch means and the second switch means are alternately turned on / off.   The first control circuit is in one cycle with respect to the operating frequency of the third switch means and the fourth switch means of the second control circuit in synchronization with the turning on of the third switch means or the fourth switch means. The first switch means and the second switch means are alternately turned on / off alternately, and the on / off of the first switch means and the second switch means is repeated in an intermittent cycle, or the first 8. The power supply device according to claim 7, wherein the power supply device has a function of completely stopping on / off of the switch means and the second switch means.

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