JP6515338B2 - Switching power supply device and projection type video display device - Google Patents

Description

  The present disclosure relates to a switching power supply device and a projection type video display device provided with the switching power supply device.

  Patent Document 1 discloses a current resonance type switching power supply device represented by an LLC converter device.

JP, 2014-64353, A

  The present disclosure is an LLC switching power supply device capable of stably supplying power by controlling to a predetermined output voltage even when a large load fluctuation occurs in a circuit to which power is supplied (hereinafter, also referred to as “load circuit”). And a projection type video display provided with the switching power supply.

  A switching power supply according to the present disclosure includes: a transformer including a primary winding and a secondary winding divided into a plurality of winding units; and a resonant capacitor forming a resonant circuit including the primary winding as a component. It is extracted from the first switching element and the second switching element provided on the primary winding side, a plurality of rectifying diodes for extracting the voltage induced in the secondary winding in units of windings, and the plurality of rectifying diodes An output voltage switching circuit that switches and outputs a voltage, a current detection circuit that detects a current flowing through the load circuit, and a control unit that controls the output voltage switching circuit based on a detection result of the current detection circuit.

  The projection type video display apparatus in this indication is provided with a light source part and a switching power supply which supplies electric power to a light source part. The switching power supply device includes a transformer including a primary winding and a secondary winding divided into a plurality of winding units, a resonant capacitor forming a resonant circuit including the primary winding as a component, and a primary The first switching element and the second switching element provided on the winding side, a plurality of rectifying diodes for taking out the voltage induced in the secondary winding in winding units, and the voltages taken out from the plurality of rectifying diodes An output voltage switching circuit that switches and outputs, a current detection circuit that detects a current flowing to the light source unit, and a control unit that controls the output voltage switching circuit based on a detection result of the current detection circuit.

  The LLC switching power supply device according to the present disclosure is effective as a power supply device capable of supplying stable power controlled to a predetermined output voltage even to a load circuit that may cause a large load fluctuation.

FIG. 1 is a perspective view schematically showing an example of the appearance of a projection type image display apparatus provided with a switching power supply apparatus of the LLC system in the first embodiment. FIG. 2 is a block diagram schematically showing one configuration example of a projection type video display device provided with the switching power supply device of the LLC system in the first embodiment. FIG. 3 is a circuit diagram showing one configuration example of the switching power supply device and the light source unit in the first embodiment. FIG. 4 is a diagram schematically showing an operation example of the switching power supply device according to the first embodiment. FIG. 5 is a diagram schematically showing an operation example of the switching power supply device according to the first embodiment. FIG. 6 is a diagram schematically showing an operation example of the switching power supply device according to the first embodiment. FIG. 7 is a diagram schematically showing an operation example of the switching power supply device according to the first embodiment.

  Hereinafter, embodiments will be described in detail with reference to the drawings as appropriate. However, the detailed description may be omitted if necessary. For example, detailed description of already well-known matters and redundant description of substantially the same configuration may be omitted. This is to avoid unnecessary redundancy in the following description and to facilitate understanding by those skilled in the art.

  It should be noted that the attached drawings and the following description are provided to enable those skilled in the art to fully understand the present disclosure, and they are not intended to limit the claimed subject matter.

  In the description, the same symbols, symbols, and numerals indicate the same components unless otherwise described. Further, unless otherwise described, components not essential to the present invention are not shown.

Embodiment 1
The first embodiment will be described below with reference to FIGS. 1 to 7.

[1-1. Constitution]
FIG. 1 is a perspective view schematically showing an example of the appearance of a projection-type image display apparatus 100 provided with a switching power supply device 28 of the LLC system in the first embodiment.

  The projection type video display apparatus 100 projects video light generated according to a video signal input from the outside onto the screen 500. The projection display apparatus 100 is an example of a projection display apparatus.

  FIG. 2 is a block diagram schematically showing a configuration of a projection-type image display apparatus 100 including the switching power supply device 28 of the LLC system in the first embodiment. In FIG. 2, the flow of signals is indicated by solid arrows, and the flow of light is indicated by white arrows.

  In addition, the projection type video display apparatus 100 shown in FIG. 2 is an example of a projection type video display apparatus, and the projection type video display apparatus in this Embodiment is not limited to the structure shown in FIG. 2 at all.

  The projection type video display apparatus 100 includes a light source unit 10 which is an example of a light source unit, a light source drive unit 20, a main control unit 30 which is an example of a control unit, an image generation unit 40, and a light guide optical system 50. And a projection optical system 60.

  The light source unit 10 includes a plurality of semiconductor laser diodes (not shown in FIG. 2), which are an example of semiconductor light source elements. The light source unit 10 can cause a phosphor (not shown) to emit light using laser light output from the semiconductor laser diode as excitation light. And the light source part 10 is comprised so that the emitted light of this fluorescent substance and a laser beam may be emitted as illumination light.

  The light guide optical system 50 includes optical members (not shown) such as various lenses, mirrors, and rod integrators. The light guide optical system 50 is configured to guide the illumination light emitted from the light source unit 10 to the image generation unit 40 using these optical members.

  The image generation unit 40 includes an element for spatially modulating light, such as a digital micro mirror device (DMD) or a liquid crystal panel. Then, the video generation unit 40 is configured to spatially modulate the illumination light emitted from the light source unit 10 according to a video signal input from the outside using the elements, and generate video light.

  The projection optical system 60 includes an optical member such as a lens or a mirror. The projection optical system 60 is configured to magnify the image light generated by the image generation unit 40 and to project the image light onto the screen 500 using these optical members.

  The main control unit 30 is configured to control the entire projection-type image display apparatus 100 including the light source drive unit 20, the image generation unit 40, and the like.

  The light source drive unit 20 includes a switching power supply device (hereinafter, simply referred to as “switching power supply device”) 28 of the LLC system, and is configured to generate electric power necessary for driving the light source unit 10 and supply it to the light source unit 10 It is done. The switching power supply device 28 will be described later.

  The configuration and operation of each block included in the projection type image display apparatus 100 are substantially the same as a generally used projector except for the configurations of the switching power supply device 28 and the light source unit 10 included in the light source drive unit 20. Therefore, the detailed description is omitted.

  Next, the configurations of the switching power supply device 28 and the light source unit 10 in the present embodiment will be described.

  FIG. 3 is a circuit diagram showing one configuration example of the switching power supply device 28 and the light source unit 10 in the first embodiment. In FIG. 3, the light source drive unit 20, the light source unit 10, and the main control unit 30 are shown.

  The light source drive unit 20 includes a switching power supply device 28 which is an example of a switching power supply device, and an FET drive circuit 25. The switching power supply device 28 is an LLC converter device (current resonance type switching power supply device). The light source unit 10 is an example of a load circuit to which the switching power supply device 28 supplies power.

  The switching power supply device 28 includes a DC power supply Vin which is an example of a DC power supply device, a switching element Q1 which is an example of a first switching element, a switching element Q2 which is an example of a second switching element, a transformer T which is an example of a transformer, and a capacitor Cq, a capacitor Cr which is an example of a resonant capacitor, diodes D1, D2, D3, D4 which are an example of a rectifying diode, a capacitor C1 which is an example of a first capacitor, a capacitor C2 which is an example of a second capacitor, an output voltage switching circuit A switching element Q3 as an example, a current detection circuit 23 as an example of a current detection circuit, a voltage detection circuit 24 as an example of a voltage detection circuit, a microcomputer 21 as an example of a control unit, and control as an example of a control unit A circuit 22;

  The DC power supply Vin is an example of a power supply device capable of outputting DC power. The DC power supply Vin may be installed outside the switching power supply device 28 or outside the light source drive unit 20.

  The switching elements Q1 and Q2 are electrically connected in series to each other and connected in series to both terminals of the DC power supply Vin. The switching element Q1 is disposed on the positive side of the DC power supply Vin, and the switching element Q2 is disposed on the negative side (or the ground side) of the DC power supply Vin. The switching (switching operation) of switching on and off of the switching elements Q 1 and Q 2 is controlled by the control circuit 22. Hereinafter, the conduction state of the switching element is referred to as “on”, and the interruption state is referred to as “off”. In the present embodiment, an example in which an N-channel FET (Field Effect Transistor) is used as the switching elements Q1 and Q2 is described, but the present disclosure is not limited to this configuration.

  The transformer T includes a primary winding L1 and a secondary winding L2. The primary winding L1 is an example of a primary winding, and the secondary winding L2 is an example of a secondary winding. One end of the primary winding L1 is connected to an electrical connection point between the switching element Q1 and the switching element Q2. The current output from the DC power supply Vin is supplied to the primary winding L1 through the switching element Q1 and its connection point. In the present embodiment, the number of turns of the primary winding L1 of the transformer T is referred to as "n1". Further, although an example in which n1 is 36 turns and the number of turns of the secondary winding L2 is 24 turns is shown in the present embodiment, the present disclosure is not limited to this configuration.

  In the primary winding L1 of the transformer T, as shown in FIG. 3, an excitation inductance Lm and a leakage inductance Lr corresponding to the coupling coefficient of the transformer T are present. Although the primary winding L1, the excitation inductance Lm of the primary winding L1, and the leakage inductance Lr are separately shown in FIG. 3, the inductance Lr, which is independent of the primary winding L1, is shown. Lm does not exist.

  The other end of the primary winding L1 is connected to one end of the capacitor Cr, and the other end of the capacitor Cr is connected to the negative side (or the ground side) of the DC power supply Vin. As described above, in the switching power supply device 28, by electrically connecting the primary winding L1 and the capacitor Cr in series, a current resonance circuit is formed by the excitation inductance Lm, the leakage inductance Lr, and the capacitor Cr. This current resonance circuit is an example of a current resonance circuit. The resonant operation of this current resonance circuit induces a voltage in the secondary winding L2 of the transformer T.

  The capacitor Cq is a capacitor for voltage resonance for reducing electrical loss in the switching elements Q1 and Q2, and is electrically connected in parallel to the primary winding L1.

  In the switching power supply device 28 according to the present embodiment, the secondary winding L2 of the transformer T is divided into four winding units L21, L22, L23, and L24. The four winding units L21, L22, L23, and L24 are an example of a plurality of winding units. In the present embodiment, the number of turns of each of the winding unit L22 and the winding unit L23 is described as "n2", and the number of turns of each of the winding unit L21 and the winding unit L24 is described as "n3". Further, although an example in which n2 is eight turns and n3 is four turns is shown in the present embodiment, the present disclosure is not limited to this configuration.

  The diodes D1, D2, D3 and D4 are examples of rectifying diodes for rectifying a voltage generated in the secondary winding L2. The anode of the diode D1 is electrically connected to one end of the winding unit L21. The anode of the diode D2 is electrically connected to the electrical connection point between the other end of the winding unit L21 and one end of the winding unit L22. The anode of the diode D3 is electrically connected to the electrical connection point between the other end of the winding unit L23 and one end of the winding unit L24. The anode of the diode D4 is electrically connected to the other end of the winding unit L24. The cathode of the diode D1 and the cathode of the diode D4 are electrically connected to each other, and the cathode of the diode D2 and the cathode of the diode D3 are electrically connected to each other. Each cathode of the diodes D1 to D4 is an example of a plurality of voltage output terminals.

  The capacitor C1 is an example of a capacitor for smoothing the voltage. One end of capacitor C1 is electrically connected to the electrical connection point between the cathode of diode D1 and the cathode of diode D4, and the other end is the other end of winding unit L22 and one end of winding unit L23. It is electrically connected to the electrical connection point.

  The capacitor C2 is an example of a capacitor for smoothing the voltage. One end of capacitor C2 is electrically connected to the electrical connection point between the cathode of diode D2 and the cathode of diode D3, and the other end is the other end of winding unit L22 and one end of winding unit L23. It is electrically connected to the electrical connection point.

  Thus, the other end of the capacitor C1 and the other end of the capacitor C2 are electrically connected to each other.

  With this configuration, the voltage rectified by the diode D1 or the diode D4 is smoothed by the capacitor C1. In addition, the voltage rectified by the diode D2 or the diode D3 is smoothed by the capacitor C2.

  The switching element Q3 is an example of an output voltage switching circuit for selecting and switching an output voltage generated in the secondary winding L2 of the transformer T in units of windings. In the present embodiment, an example in which an N-channel FET is used as the switching element Q3 is shown, but the present disclosure is not limited to this configuration.

  The drain terminal of the switching element Q3 is connected to one end of the capacitor C1 (electrical connection point between the cathode of the diode D1 and the cathode of the diode D4), and the source terminal of the switching element Q3 is one end of the capacitor C2 (diode D2 It is connected to the electrical connection point between the cathode and the cathode of the diode D3. The source terminal of the switching element Q3 is also electrically connected to the light source unit 10 and the voltage detection circuit 24. The gate terminal of the switching element Q3 is connected to the microcomputer 21, and the control signal output from the microcomputer 21 is supplied to this gate terminal. Thus, the microcomputer 21 can control the on / off switching (switching operation) of the switching element Q3.

  As described above, the light source unit 10 is connected to the source terminal of the switching element Q3. Therefore, when switching element Q3 becomes conductive (on state), an output voltage obtained by being rectified by diode D1 or diode D4 of the output voltage of secondary winding L2 and smoothed by capacitors C1 and C2 (hereinafter referred to as The “first output voltage” is supplied to the light source unit 10. When the switching element Q3 is cut off (off state), an output voltage obtained by rectifying with the diode D2 or the diode D3 of the output voltage of the secondary winding L2 and smoothing with the capacitor C2 (hereinafter referred to as “second output The voltage (referred to as “voltage”) is supplied to the light source unit 10.

  The light source unit 10 includes a first light source module 11, a second light source module 12, and a resistor R for current detection.

  The first light source module 11 and the second light source module 12 are an example of a light source module. The resistor R is an example of a current detection resistor for detecting the current flowing to the first light source module 11 and the second light source module 12.

  The resistor R is connected in series between the first light source module 11 and the second light source module 12. The first light source module 11 and the second light source module 12 are electrically connected in series with the resistor R interposed therebetween. The first light source module 11 is electrically connected to the source terminal of the switching element Q3, and the second light source module 12 is electrically connected to the electrical connection point between the other end of the capacitor C1 and the other end of the capacitor C2. Connected.

  The first light source module 11 includes a plurality of semiconductor laser diodes 11a, an FET 11b, and an FET driver 11c. The FET 11 b is an example of a shorting switching element. In the present embodiment, an example in which the FET 11b is an N-channel FET is shown, but the present disclosure is not limited to this configuration. Moreover, although the number of semiconductor laser diodes 11 a included in the first light source module 11 is, for example, eight, the present disclosure is not limited to this number.

  The plurality of semiconductor laser diodes 11a are electrically connected to one another in series. The FET 11 b is electrically connected in parallel to the plurality of semiconductor laser diodes 11 a connected in series. The drain terminal of the FET 11b is connected to one end (anode) of the plurality of semiconductor laser diodes 11a connected in series, and the source terminal of the FET 11b is connected to the other end (cathode). Therefore, when the FET 11b is turned on, both terminals (the anode at one end and the cathode at the other end) of the plurality of semiconductor laser diodes 11a connected in series are shorted.

  The FET driver 11c has a configuration in which an LED (Light Emitting Diode) and a photocell are integrated. In the FET driver 11c, when the LED emits light, an electromotive force is generated in the photocell. The photovoltaic cell of the FET driver 11c is electrically connected between the gate terminal and the source terminal of the FET 11b so that the output of the photovoltaic cell is supplied to the gate terminal of the FET 11b. When the LED emits light, the FET 11b is turned on (conductive state), and when the LED is not emitting light, the FET 11b is turned off (cut off). As described above, in the first light source module 11, the switching between the light emission and the non-light emission of the LED of the FET driver 11c is controlled, whereby the switching between the on and off of the FET 11b is controlled.

  Then, when the FET 11b is turned off, no current flows in the FET 11b, and current flows in the semiconductor laser diode 11a, so that the semiconductor laser diode 11a emits light. Further, when the semiconductor laser diode 11a is in an insulated state due to a failure or the like, by turning on the FET 11b, a current flows to the FET 11b, so a current path which does not pass through the semiconductor laser diode 11a can be secured. .

  The second light source module 12 has substantially the same configuration as the first light source module 11, and includes the plurality of semiconductor laser diodes 12a, the FET 12b, and the FET driver 12c, similarly to the first light source module 11. Since the description will be repeated, the description of the second light source module 12 is omitted.

  The current detection circuit 23 is electrically connected to both ends of the current detection resistor R, and is configured to measure the voltage at both ends of the resistance R to detect the current flowing to the light source unit 10. Information indicating the detected current value is supplied from the current detection circuit 23 to the microcomputer 21.

  The FET drive circuit 25 controls light emission / non-emission of each of the LED of the FET driver 11 c of the first light source module 11 and the LED of the FET driver 12 c of the second light source module 12 based on the control signal from the microcomputer 21 It is configured to Thus, the on / off switching of the FET 11 b of the first light source module 11 and the FET 12 b of the second light source module 12 are controlled by the microcomputer 21.

  For example, when the microcomputer 21 detects a failure of the semiconductor laser diode 12 a, it turns on the FET 12 b via the FET drive circuit 25. Thus, in the light source unit 10, the current path of the current flowing through the semiconductor laser diode 11a is secured by the FET 12b in the on state, so that the light emission of the semiconductor laser diode 11a can be maintained.

  The voltage detection circuit 24 is electrically connected to the source terminal of the switching element Q3, and is configured to detect the voltage of the source terminal of the switching element Q3. Thus, the voltage detection circuit 24 can detect the voltage of the power supplied from the secondary winding L2 of the transformer T to the light source unit 10. Information indicating the detected voltage value is supplied from the voltage detection circuit 24 to the microcomputer 21.

  The microcomputer 21 is configured to monitor the voltage detected by the voltage detection circuit 24, that is, the output voltage of the secondary winding L2, and to supply the control circuit 22 with information indicating the detected voltage. There is.

  The control circuit 22 is an oscillation circuit configured to alternately turn on the switching element Q1 and the switching element Q2. Hereinafter, the number of repetitions of the on state and the off state per unit time (for example, one second) will be referred to as “switching frequency fs”.

  The control circuit 22 is configured to control the switching operation of the switching elements Q1 and Q2 based on the voltage information supplied from the microcomputer 21. In the switching power supply device 28, when the switching frequency fs of the switching elements Q1 and Q2 changes, the output voltage of the secondary winding L2 changes. Therefore, control circuit 22 compares the voltage detected by voltage detection circuit 24 with a preset value for comparison, and controls switching frequency fs of switching elements Q1 and Q2 based on the comparison result. Thus, the switching power supply 28 can keep the output voltage of the secondary winding L2 substantially constant.

  The microcomputer 21 may compare the voltage detected by the voltage detection circuit 24 with the preset value for comparison. Then, information representing the comparison result may be supplied from the microcomputer 21 to the control circuit 22.

  However, when a large load fluctuation occurs in the load circuit, the output voltage of the switching power supply 28 may have to be changed beyond the controllable range of the switching frequency fs. When such a situation occurs, it is difficult to maintain the output voltage of the secondary winding L2 at an appropriate voltage only by controlling the switching frequency fs.

  Therefore, in switching power supply device 28 shown in the present embodiment, microcomputer 21 is configured to monitor the current detected by current detection circuit 23 and to control the switching operation of switching element Q3 based on the result. There is. Details of this operation will be described later.

  The memory 26 stores, for example, information related to the state of a circuit described later according to an instruction of the microcomputer 21. Although FIG. 3 shows an example in which the memory 26 is disposed outside the light source drive unit 20, the memory 26 may be provided in the switching power supply device 28 or in the light source drive unit 20. It may be provided. Alternatively, it may be built in the microcomputer 21.

[1-2. Operation]
The outline of the operation of the switching power supply 28 shown in FIG. 3 will be described below.

  In the switching power supply device 28, first, the switching element Q1 is turned on and the switching element Q2 is turned off, whereby the current (for example, the positive direction) output from the DC power supply Vin to the primary winding L1 of the transformer T Current flows). Next, the switching element Q1 is turned off, and the switching element Q2 is turned on, so that a current (for example, a current in the negative direction) flows from the capacitor Cr to the primary winding L1 of the transformer T in the reverse direction. Flows. This phenomenon occurs when the current resonance circuit composed of the capacitor Cr, the excitation inductance Lm, and the leakage inductance Lr resonates. As described above, in the switching power supply device 28, by alternately switching on and off the switching elements Q1 and Q2, current in the positive direction and current in the negative direction alternately flow in the primary winding L1 of the transformer T. And, by repeating these operations, a voltage is induced on the secondary winding L2 side of the transformer T.

  The voltage induced on the secondary winding L2 side of the transformer T is rectified by the diodes D1, D2, D3 and D4, and smoothed by the capacitors C1 and C2. At this time, the switching frequency fs of the switching elements Q1 and Q2 is controlled by the control circuit 22 so as to obtain a predetermined output voltage.

  Generally, in the LLC type switching power supply, voltage and current respectively resonate, and therefore occur when the first switching element (for example, switching element Q1) and the second switching element (for example, switching element Q2) are switched on and off. Power loss and noise can be reduced. However, the switching power supply apparatus of the LLC system has a narrower control range of the output voltage as compared with the switching power supply apparatus of the PWM control system. Therefore, the LLC switching power supply apparatus is not suitable for a power supply source to a load circuit having a relatively large load fluctuation.

  By the way, in the projection type image display apparatus 100 mentioned as an example in this embodiment, in the light source section 10, the first light source module 11 configured by connecting a plurality of semiconductor laser diodes 11a in series, and a plurality of semiconductor laser diodes The second light source module 12 configured by connecting in series 12a is connected in series. Therefore, if any of the plurality of semiconductor laser diodes 11a and 12a is broken or a disconnection (hereinafter referred to as an "open failure") occurs, the current path of the current flowing through the light source unit 10 is cut off. The current does not flow to any semiconductor laser diodes, and all the semiconductor laser diodes are in a non-emission state.

  In order to prevent the occurrence of such a situation, the switching element connected in parallel to the semiconductor laser diode having an open failure may be turned on to secure the current path of the current flowing through the light source unit 10. For example, when an open failure occurs in the semiconductor laser diode 12a, the light emission of a normal semiconductor laser diode 11a can be maintained by turning on the FET 12b and providing a current path passing through the FET 12b.

  However, when such a condition occurs, a large load fluctuation occurs in the load circuit to which power is supplied from the switching power supply device 28. For example, in the above-described example, when the FET 12 b is turned on, the second light source module 12 is substantially shorted. Therefore, the load of the load circuit seen from the switching power supply device 28 is halved from the circuit in which the first light source module 11 and the second light source module 12 are connected in series to the circuit of the first light source module 11 alone. The reverse is also true. If such a large load fluctuation occurs in the load circuit, the current flowing in the load circuit may fluctuate significantly, so it is desirable to appropriately reduce the output voltage of the switching power supply 28 in accordance with the load fluctuation. For example, when the FET 12b is turned on due to an open failure of the second light source module 12, the output voltage of the switching power supply 28 is appropriately reduced to substantially the same as before the occurrence of the open failure in the first light source module 11. The current can flow. However, in such a case, it is difficult to maintain the output voltage of the switching power supply 28 at an appropriate voltage simply by controlling the switching frequency fs.

  The switching power supply device 28 shown in the present embodiment is configured to be able to supply stable power to the load circuit even when such a large load fluctuation occurs in the load circuit.

  Hereinafter, the operation of each of the switching power supply devices 28 when the semiconductor laser diodes 11a and 12a are all normal (first operation) and when one of the semiconductor laser diodes has an open failure (second operation) Will be described with reference to FIGS. 4 to 7.

  4 to 7 schematically show an operation example of the switching power supply device 28 according to the first embodiment. In FIGS. 4 to 7, the flow of current is indicated by a broken line.

[1-2-1. First operation]
When both the semiconductor laser diodes 11a and 12a operate normally, the load of the load circuit seen from the switching power supply 28 is relatively large. In such a case, in the switching power supply device 28, the microcomputer 21 turns on the switching element Q3 so that the output voltage does not decrease.

  The control circuit 22 turns on the switching element Q1 and turns off the switching element Q2. Thereby, as shown in FIG. 4, a current flows from the DC power supply Vin to the primary winding L1, and a voltage is induced in the winding units L22 and L21 of the secondary winding L2. The induced voltage is rectified by the diode D1 and smoothed by the capacitors C1 and C2.

  Next, the control circuit 22 turns off the switching element Q1 and turns on the switching element Q2. As a result, as shown in FIG. 5, a current in the reverse direction flows from the capacitor Cr to the primary winding L1, and a voltage is induced in the winding units L23 and L24 of the secondary winding L2. The induced voltage is rectified by the diode D4 and smoothed by the capacitors C1 and C2.

  By these operations, the voltage between both terminals of the capacitors C1 and C2 becomes the first output voltage V1, and the power of the first output voltage V1 is supplied to the light source unit 10.

  At this time, the microcomputer 21 supplies the control circuit 22 with information (information indicating the voltage value of the first output voltage V1) based on the voltage value detected by the voltage detection circuit 24. The control circuit 22 controls (feedback control) the switching frequency fs of the switching elements Q1 and Q2 based on the information supplied from the microcomputer 21 so that the first output voltage V1 does not fluctuate.

1-2-2. Second operation]
When an open failure occurs in one or both of the semiconductor laser diodes 11a and 12a, a break occurs in the current path through which the current has flowed, and the current does not flow in the current detection resistor R. When the current does not flow in the resistor R, that is detected by the current detection circuit 23, and information indicating the detection result is supplied from the current detection circuit 23 to the microcomputer 21. The microcomputer 21 receiving the information determines that an open failure has occurred in any of the semiconductor laser diodes. Then, the microcomputer 21 temporarily lowers the output voltage of the DC power supply Vin via, for example, the main control unit 30. This is to prevent an overvoltage from being applied to the load circuit (for example, the light source unit 10) in the process of the operation described below.

  When information indicating that current does not flow in the resistor R is supplied from the current detection circuit 23 to the microcomputer 21, the microcomputer 21 is opened to either the first light source module 11 or the second light source module 12. It is unclear whether a failure has occurred. Therefore, the microcomputer 21 first drives the FET driver 11c of the first light source module 11 via the FET drive circuit 25 to turn on the FET 11b. Thus, the terminals of the semiconductor laser diode 11a connected in series are short-circuited.

  If an open failure occurs in the semiconductor laser diode 11a, a current flows in the resistor R. Therefore, the microcomputer 21 receives the detection result (detection result indicating that the current flows to the resistor R) supplied from the current detection circuit 23, and determines that the open failure has occurred in the first light source module 11. it can. The determination result (information indicating that an open failure has occurred in the first light source module 11) is stored in the memory 26 by the microcomputer 21.

  On the other hand, if the current does not flow in the resistor R, the microcomputer 21 detects the current in the current detection circuit 23 (the detection result indicating that the current does not flow in the resistor R). It can be determined that an open failure has occurred. In this case, the microcomputer 21 returns the FET 11b to the OFF state via the FET drive circuit 25.

  Next, the microcomputer 21 drives the FET driver 12 c of the second light source module 12 via the FET drive circuit 25 to turn on the FET 12 b. Thus, the terminals of the semiconductor laser diode 12a connected in series are short-circuited.

  If an open failure occurs in the semiconductor laser diode 12a, a current flows in the resistor R. Therefore, the microcomputer 21 receives the detection result (detection result indicating that the current flows to the resistor R) supplied from the current detection circuit 23, and determines that the second light source module 12 has an open failure. it can. Then, the determination result (information indicating that the second light source module 12 has an open failure) is stored in the memory 26 by the microcomputer 21.

  When the FET 11b or FET 12b is turned on and current starts to flow to the light source unit 10, a voltage corresponding to the number of turns (n2 + n3) of the secondary winding L2 is generated from the secondary winding L2 of the transformer T ing. This voltage is lower than the first output voltage V1 by the amount by which the output voltage of the DC power supply Vin is lowered.

  Next, the microcomputer 21 supplies power at a stable output voltage (appropriate current) to the load circuit (e.g., the light source unit 10) whose load has decreased even while the switching element Q3 is maintained in the on state. Determine whether it is possible.

  The microcomputer 21 previously stores the correspondence between the number of open failure light source modules and the on / off of the switching element Q3. Although not illustrated, an example of the correspondence in the case where the light source unit 10 includes four light source modules, for example, will be described. For example, when the number of open failure light source modules is zero or one, the microcomputer 21 determines that power can be supplied at a stable output voltage while the switching element Q3 is kept on, and is open When the number of failed light source modules is two or more, it is determined that power supply at a stable output voltage is difficult unless the switching element Q3 is turned off (overcurrent may flow in the load circuit). It may be preset in advance. Note that these numerical values and correspondences are merely examples, and the present disclosure is not limited to these numerical values and correspondences at all.

  As described above, when the microcomputer 21 determines that the power supply with the stable output voltage is possible, the switching element Q3 is maintained in the on state. If the microcomputer 21 determines that power supply at a stable output voltage is difficult (overcurrent may flow in the load circuit), the switching element Q3 is turned off. Then, the microcomputer 21 stores, in the memory 26, information indicating that the switching element Q3 has been turned off.

  Thereafter, the microcomputer 21 restores the output voltage of the DC power supply Vin, which has been temporarily lowered, to the original voltage value.

  Subsequently, the on / off switching operation of the switching elements Q1 and Q2 is controlled as follows by the microcomputer 21 and the control circuit 22, and an output voltage is generated in the secondary winding L2 of the transformer T. At this time, if the switching element Q3 is in the on state, the output voltage is the first output voltage V1. If the switching element Q3 is in the off state, the output voltage is as follows.

  The control circuit 22 turns on the switching element Q1 and turns off the switching element Q2. Thereby, as shown in FIG. 6, a current flows from the DC power supply Vin to the primary winding L1, and a voltage is induced in the winding unit L22 of the secondary winding L2. The induced voltage is rectified by the diode D2 and smoothed by the capacitor C2.

  By this operation, the voltage between both terminals of the capacitor C2 becomes the second output voltage V2, and the power of the second output voltage V2 is supplied to the light source unit 10. At this time, the voltage generated in the winding unit (L22 + L21) is rectified by the diode D1 and smoothed by the capacitor C1. However, since the switching element Q3 is in the off state, the power stored in the capacitor C1 is not supplied to the light source unit 10.

  Next, the control circuit 22 turns off the switching element Q1 and turns on the switching element Q2. As a result, as shown in FIG. 7, a current in the reverse direction flows from the capacitor Cr to the primary winding L1, and a voltage is induced in the winding unit L23 of the secondary winding L2. The induced voltage is rectified by the diode D3 and smoothed by the capacitor C2.

  By this operation, the voltage between both terminals of the capacitor C2 becomes the second output voltage V2, and the power of the second output voltage V2 is supplied to the light source unit 10. At this time, the voltage generated in the winding unit (L23 + L24) is rectified by the diode D4 and smoothed by the capacitor C1. However, since the switching element Q3 is in the off state, the power stored in the capacitor C1 is not supplied to the light source unit 10.

  As described above, when the switching element Q3 is in the off state, among the voltages induced in the secondary winding L2 of the transformer T, the second output voltage V2 rectified by the diodes D2 and D3 and smoothed by the capacitor C2 is The switching power supply unit 28 supplies the load circuit (light source unit 10). The second output voltage V2 is a voltage corresponding to the number of turns n2 of the winding units L22 and L23 of the secondary winding L2, and the ratio of the number of turns of the winding units L21 to L24 (ratio of n2 to n3) Accordingly, the voltage is lower than the first output voltage V1. For example, if the number of turns n2 = 8 and the number of turns n3 = 4, the second output voltage V2 is 2/3 the voltage of the first output voltage V1.

  Thus, the operation of the switching power supply 28 after the switching element Q3 is turned off is the above-described first operation except that the second output voltage V2 generated is lower than the first output voltage V1. The operation is substantially the same as the operation of the switching power supply 28 described above. That is, the microcomputer 21 supplies information based on the voltage value detected by the voltage detection circuit 24 (information indicating the voltage value of the second output voltage V2) to the control circuit 22, and the control circuit 22 receives the information from the microcomputer 21. The switching frequency fs of the switching elements Q1 and Q2 is controlled (feedback control) based on the supplied information so that the second output voltage V2 does not fluctuate.

  In the operation example shown in the first embodiment, the first output voltage V1 is set to a voltage at which an appropriate current flows in the first light source module 11 and the second light source module 12 operating normally, and the second output voltage It is assumed that V2 is set to a voltage at which an appropriate current flows through the first light source module 11 alone or the second light source module 12 alone. However, the present disclosure is not limited to this configuration. It is desirable that the first output voltage V1 and the second output voltage V2 be appropriately set according to the configuration of the light source unit 10. Further, the switching power supply device 28 may output the third output voltage V3 or the fourth output voltage V4 according to the configuration of the light source unit 10.

  When the projection display apparatus 100 is activated, the microcomputer 21 reads the information stored in the memory 26 and performs various settings based on the read information. For example, in the case of the above-described example, the memory 26 receives failure information (for example, information indicating that an open failure has occurred in the second light source module 12) related to the light source unit 10 from the switching power supply device 28 Information on the voltage of the output power (for example, information indicating that the switching element Q3 is set to the off state and the second output voltage V2 is selected) is stored. In this case, the microcomputer 21 operates as follows each time the projection display apparatus 100 is activated after these pieces of information are stored in the memory 26. That is, the FET driver 12c of the second light source module 12 is driven via the FET drive circuit 25, the FET 12b is turned on, and the terminals of the series connected semiconductor laser diodes 12a are shorted. Further, the switching element Q3 is turned off. After these settings are made, the switching power supply 28 is operated.

[1-3. Effect etc]
As described above, in the present embodiment, the switching power supply device includes a transformer including a primary winding and a secondary winding divided into a plurality of winding units, and a resonance including a primary winding as a component. Resonant capacitor forming a circuit, first switching element and second switching element provided on primary winding side, and a plurality of rectifying diodes for taking out voltage induced in secondary winding in units of winding An output voltage switching circuit that switches and outputs voltages extracted from a plurality of rectifier diodes, a current detection circuit that detects a current flowing through a load circuit, and control that controls the output voltage switching circuit based on detection results in the current detection circuit And a unit.

  The switching power supply may further include a voltage detection circuit configured to detect a voltage supplied to the load circuit. The control unit may control the first switching element and the second switching element based on the detection result in the voltage detection circuit.

  In this switching power supply device, the control unit may temporarily lower the voltage supplied to the primary winding based on the detection result in the current detection circuit.

  The projection type video display apparatus in this indication is provided with a light source part and a switching power supply which supplies electric power to a light source part. The switching power supply device includes a transformer including a primary winding and a secondary winding divided into a plurality of winding units, a resonant capacitor forming a resonant circuit including the primary winding as a component, and a primary The first switching element and the second switching element provided on the winding side, a plurality of rectifying diodes for taking out the voltage induced in the secondary winding in winding units, and the voltages taken out from the plurality of rectifying diodes An output voltage switching circuit that switches and outputs, a current detection circuit that detects a current flowing to the light source unit, and a control unit that controls the output voltage switching circuit based on a detection result of the current detection circuit.

  The light source unit may include a plurality of light source modules having a plurality of semiconductor light source elements electrically connected in series. The plurality of light source modules may be electrically connected in series with a current detection resistor interposed therebetween. The current detection circuit may detect the current flowing through the resistor.

  Further, each of the light source modules may include a shorting switching element configured to be able to short between both terminals of a plurality of semiconductor light source elements connected in series. Then, the control unit may control each of the shorting switching elements based on the detection result in the current detection circuit.

  In the present embodiment, primary winding L1 is an example of a primary winding, and secondary winding L2 is an example of a secondary winding. The transformer T is an example of a transformer. The capacitor Cr is an example of a resonance capacitor, and a current resonance circuit formed by the excitation inductance Lm, the leakage inductance Lr, and the capacitor Cr is an example of a resonance circuit. The switching element Q1 is an example of a first switching element, and the switching element Q2 is an example of a second switching element. The switching power supply 28 is an example of a switching power supply. The winding units L21, L22, L23, and L24 are an example of a plurality of winding units. The diodes D1, D2, D3 and D4 are examples of rectifying diodes. The switching element Q3 is an example of an output voltage switching circuit. The current detection circuit 23 is an example of a current detection circuit. The microcomputer 21, the control circuit 22, and the main control unit 30 are an example of a control unit. The voltage detection circuit 24 is an example of a voltage detection circuit. The light source unit 10 is an example of a light source unit and an example of a load circuit. The projection type video display apparatus 100 is an example of a projection type video display apparatus. The semiconductor laser diodes 11a and 11b are examples of semiconductor light source elements. The first light source module 11 and the second light source module 12 are examples of light source modules. The resistor R is an example of a resistor for current detection. The FET 11 b and the FET 12 b are examples of the shorting switching element.

  Generally, in the LLC switching power supply, the control range of the output voltage is narrower than that of the PWM control switching power supply. Therefore, the LLC switching power supply apparatus is not suitable for a power supply source to a load circuit having a relatively large load fluctuation. For example, if the load circuit is configured to short the fault location in the event of a failure, the load in the load circuit may fluctuate relatively significantly. Therefore, the LLC switching power supply is not suitable for supplying power to such load circuits.

  For example, when an open failure occurs in the light source module provided in the light source unit, which is an example of the load circuit, the projection display apparatus 100 described in the present embodiment determines the failure location based on the detection result in the current detection circuit. Identify and control the shorting switching element so as to short the fault. Therefore, a current path avoiding an open failure can be secured to maintain the light emission of a normal light source module, but the load in the load circuit may fluctuate relatively relatively.

  However, as the switching power supply device of the present disclosure shows one example in the first embodiment, one or more of the plurality of light source modules provided in the light source section are shorted due to an open failure, etc. When a relatively large load fluctuation occurs in the circuit, the switching element Q3, which is an example of the output voltage switching circuit, is switched from the on state to the off state to change the output voltage. Thus, the voltage output from the secondary winding of the transformer T can be set to the second output voltage V2 lower than the first output voltage V1 which is the output voltage when the switching element Q3 is in the on state. Therefore, although the switching power supply of the present disclosure is an LLC switching power supply, stable power supply is possible by controlling the output voltage to a predetermined value even when a large load fluctuation occurs in the load circuit.

(Other embodiments)
As described above, Embodiment 1 has been described as an example of the technology disclosed in the present application. However, the technology in the present disclosure is not limited to this, and can also be applied to embodiments in which changes, replacements, additions, omissions, and the like have been made. Further, each component described in the first embodiment can be combined to make a new embodiment.

  Therefore, other embodiments will be exemplified below.

  In the first embodiment, the configuration in which the light source unit 10 includes the two light source modules of the first light source module 11 and the second light source module 12 has been described. However, the present disclosure is not limited to this configuration. It is desirable that the light source unit includes an appropriate number of light source modules so as to generate the light amount required in the projection type video display device. For example, the light source unit may include three or more light source modules. Even if the light source unit includes three or more light source modules, the number of resistors R for current detection may be one. It is desirable that the arrangement position of the resistor R and the current detection circuit at that time be appropriately set.

  In the first embodiment, an example in which the secondary winding L2 of the transformer T is divided into four winding units L21, L22, L23, and L24 has been described. However, the present disclosure is not limited to this configuration. The secondary winding L2 of the transformer T preferably includes an appropriate number of winding units according to the number of light source modules included in the light source unit. For example, the secondary winding L2 of the transformer T may be divided into six or more winding units. When the secondary winding L2 is divided into six or more winding units, a diode for voltage rectification, a capacitor for voltage smoothing, etc. should be appropriately added according to the number of winding units. Is desirable. Further, it is desirable that the output voltage switching circuit be appropriately configured according to the number of voltage output terminals.

  Although not described in the first embodiment, no current flows through the resistor R when the FET 11b is in the on state and the FET 12b is in the off state, and current also flows through the resistor R when the FET 11b is in the off state and the FET 12b is in the on state. If not, the microcomputer 21 can determine that an open failure has occurred in both the first light source module 11 and the second light source module 12. In that case, the microcomputer 21 may display, for example, an error message indicating that an open failure has occurred in both the first light source module 11 and the second light source module 12 on the display unit (not shown). Further, this error message may be replaced by lighting or blinking of an LED or the like provided in the projection type video display.

  In the first embodiment, when an open failure occurs in any of the semiconductor laser diodes, the output voltage of the DC power supply Vin is temporarily lowered, but the present disclosure is not limited to this operation. For example, the microcomputer 21 may switch the switching element Q3 from on to off when the open failure is confirmed. This operation can also prevent an overcurrent from flowing in the load circuit.

  In the first embodiment, a configuration example in which the microcomputer 21, the control circuit 22, and the main control unit 30 are separated is shown, but a plurality or all of these may be integrated as one control unit. Alternatively, the output of the voltage detection circuit 24 may be configured to be directly input to the control circuit 22. Alternatively, the microcomputer 21 may be configured to directly control the output voltage of the DC power supply Vin.

  The present disclosure is applicable to a switching power supply device of LLC type and a projection type video display device provided with the switching power supply device.

10 light source unit 11 first light source module 11a, 12a semiconductor laser diode 11b, 12b FET
11c, 12c FET driver 12 second light source module 20 light source drive unit 21 microcomputer 22 control circuit 23 current detection circuit 24 voltage detection circuit 25 FET drive circuit 26 memory 28 switching power supply device 30 main control unit 40 image generation unit 50 light guide optical System 60 Projection optical system 100 Projection type display device Vin DC power supply Q1, Q2, Q3 Switching element T Transformer L1 Primary winding L2 Secondary winding L21, L22, L23, L24 Winding unit Lr Leakage inductance Lm Excitation inductance C1 , C2, Cr, Cq Capacitors D1, D2, D3, D4 Diode R resistance

Claims (8)

A transformer comprising a primary winding and a secondary winding divided into a plurality of winding units;
A resonant capacitor forming a resonant circuit including the primary winding as a component;
A first switching element and a second switching element provided on the primary winding side;
A plurality of rectifying diodes for extracting the voltage induced in the secondary winding in units of the winding;
An output voltage switching circuit that switches and outputs voltages extracted from the plurality of rectifier diodes;
A current detection circuit that detects the current flowing in the load circuit;
A control unit that controls the output voltage switching circuit based on a detection result of the current detection circuit;
A switching power supply comprising: Further comprising a voltage detection circuit configured to detect a voltage supplied to the load circuit,
The control unit
Controlling the first switching element and the second switching element based on the detection result of the voltage detection circuit;
The switching power supply device according to claim 1. The control unit
Temporarily reducing the voltage supplied to the primary winding based on the detection result in the current detection circuit;
The switching power supply device according to claim 1. A light source unit,
A switching power supply for supplying power to the light source unit;
A projection type image display device provided with
The switching power supply device
A transformer comprising a primary winding and a secondary winding divided into a plurality of winding units;
A resonant capacitor forming a resonant circuit including the primary winding as a component;
A first switching element and a second switching element provided on the primary winding side;
A plurality of rectifying diodes for extracting the voltage induced in the secondary winding in units of the winding;
An output voltage switching circuit that switches and outputs voltages extracted from the plurality of rectifier diodes;
A current detection circuit that detects a current flowing through the light source unit;
A control unit that controls the output voltage switching circuit based on a detection result of the current detection circuit;
Projection type video display device provided with The light source unit is
A plurality of light source modules having a plurality of semiconductor light source elements electrically connected in series;
The plurality of light source modules are electrically connected in series with a current detection resistor interposed therebetween;
The current detection circuit detects a current flowing through the resistor.
The projection type video display apparatus of Claim 4. Each of the light source modules is
A shorting switching element configured to be able to short between both terminals of the plurality of semiconductor light source elements connected in series;
The control unit is configured to control each of the shorting switching elements based on a detection result in the current detection circuit.
The projection type video display apparatus of Claim 5. Each of the light source modules is
A shorting switching element configured to be able to short between both terminals of the plurality of semiconductor light source elements connected in series;
The control unit is configured to control each of the shorting switching elements based on a detection result in the current detection circuit.
The projection type video display apparatus of Claim 5. The control unit
Temporarily reducing the voltage supplied to the primary winding based on the detection result in the current detection circuit;
The projection type video display apparatus of Claim 4.

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