JP2009177977A - Power circuit and method of controlling the same, power circuit for projector and projector - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a power circuit improving a power-conversion efficiency while improving a power factor and a method of controlling the power circuit, and to provide a power circuit for a projector and the projector. <P>SOLUTION: The power circuit includes a full-wave rectifier 10, a step-up circuit 20 for stepping up an output voltage from the full-wave rectifier 10 to output a DC voltage, and a control circuit 30 for controlling the output voltage from the step-up circuit 20 at a desired voltage. The power circuit has a partial step-up control circuit 40 controlling the control circuit 30 so that the output voltage from the step-up circuit 20 surpasses the output voltage from the full-wave rectifier 10 for a saturation period in which the absolute value of the input voltage of the full-wave rectifier 10 surpasses the desired voltage. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a power supply circuit and a control method therefor, a power supply circuit for a projector, and a projector.

  As a circuit for converting an AC power source into a DC power source, a power source circuit using a capacitor input type rectifier circuit in which a rectifier and a smoothing capacitor are combined is known. However, the capacitor input type rectifier circuit has a problem that the power factor is small because the input current flows only near the peak of the AC voltage.

Therefore, a power circuit using a power factor correction (PFC) circuit combining a rectifier and a booster circuit has been developed as a circuit that improves the power factor of a power circuit using a capacitor input type rectifier circuit.
International Publication No. 2003/047080 Pamphlet

  In order to operate the booster circuit, it is necessary to set an output voltage higher than the input voltage. An output that operates even at the highest input voltage, especially when multiple input voltages are assumed (for example, use in multiple countries or regions with different household power supply voltages) It is necessary to set the voltage. However, when the output voltage is increased, the power loss due to the switch element used in the booster circuit increases, so that there is a problem that the power conversion efficiency as the power supply circuit decreases.

  The present invention has been made in view of the above problems, and provides a power supply circuit and a control method thereof, a power supply circuit for a projector, and a projector that improve power conversion efficiency while improving the power factor. Objective.

  (1) A power supply circuit of the present invention controls a full-wave rectifier circuit, a booster circuit that boosts the output voltage of the full-wave rectifier circuit and outputs a DC voltage, and controls the output voltage of the booster circuit to a desired voltage. A power supply circuit including a control circuit, wherein the output voltage of the booster circuit exceeds the output voltage of the full-wave rectifier circuit in a saturation period in which the absolute value of the input voltage of the full-wave rectifier circuit exceeds a given voltage As described above, the control circuit includes a partial boost control circuit that performs partial boost control.

  According to the present invention, the average output voltage can be lowered while maintaining the state in which the output voltage of the booster circuit exceeds the input voltage, and the power factor improvement effect by the booster circuit can be reduced, so that the power supply circuit with improved power conversion efficiency It becomes possible to provide.

  (2) In this power supply circuit, the booster circuit includes a switch element that can control an output voltage, and the control circuit corresponds to a control unit that controls the switch element and an output voltage of the booster circuit. A detection unit configured to output a voltage to the control unit, wherein the control unit controls the switch element so that an output voltage of the detection unit becomes a predetermined value; The partial boost control may be performed by controlling the detection unit so as to lower the output voltage of the detection unit.

  (3) In this power supply circuit, the partial boost control circuit may have a full-wave rectification unit in an input stage and receive the same input voltage as the full-wave rectification circuit.

  (4) A power supply circuit for a projector according to the present invention includes a step-down circuit that inputs and steps down an output voltage of the power supply circuit.

  (5) The projector according to the present invention includes the power supply circuit for the projector.

  (6) A method for controlling a power supply circuit according to the present invention includes a full-wave rectifier circuit, a booster circuit that boosts an output voltage of the full-wave rectifier circuit and outputs a DC voltage, and outputs an output voltage of the booster circuit to a desired voltage. A control method of a power supply circuit including a control circuit for controlling the output voltage of the booster circuit during a saturation period in which an absolute value of an input voltage of the full-wave rectifier circuit exceeds a given voltage. The control circuit is partially boosted so as to exceed the output voltage of the circuit.

  According to the present invention, the average output voltage can be lowered while maintaining the state where the output voltage of the booster circuit is higher than the input voltage, thereby improving the power factor of the booster circuit. It is possible to provide a control method.

  DESCRIPTION OF EMBODIMENTS Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. The embodiments described below do not unduly limit the contents of the present invention described in the claims. Moreover, not all of the configurations described below are essential constituent requirements of the present invention.

1. Power Supply Circuit and Control Method of Power Supply Circuit (1) Configuration of Power Supply Circuit According to this Embodiment FIG. 1 is an example of a circuit diagram of a power supply circuit according to this embodiment.

  The power supply circuit 1 according to the present embodiment includes a full-wave rectifier circuit 10. The full-wave rectifier circuit 10 performs full-wave rectification on the AC input voltage AC, that is, outputs a voltage corresponding to the absolute value of the input voltage regardless of whether the input voltage is positive or negative. The full-wave rectifier circuit 10 may be a diode bridge circuit 50 including diodes D1 to D4 as shown in FIG.

  The power supply circuit 1 according to the present embodiment includes a booster circuit 20. The booster circuit 20 boosts the output voltage of the full-wave rectifier circuit 10 and outputs a DC voltage Vout. The booster circuit 20 can be in various known and known forms. In the present embodiment, the booster circuit 20 is composed of a boost chopper circuit.

  The boost chopper circuit may include a coil 21, a diode 22, a switch element 23, and a capacitor 24. The switch element 21 may be constituted by a transistor, for example. In the present embodiment, one end of the coil 21 is connected to the output terminal of the full-wave rectifier circuit 10, and the other end of the coil 21 is connected to the anode of the diode 22 and one end of the switch element 23. The cathode of the diode 22 is connected to one end of the capacitor 24 and to the output terminal of the boost chopper circuit. The other end of the switch element 23 and the other end of the capacitor 24 are connected to the ground potential. A control signal is input to the control terminal of the switch element 23 from a control circuit 30 described later, and ON / OFF of the switch element 23 is controlled. For example, a PWM (Pulse Width Modulation) control signal may be used as the control signal.

  Here, when the switch element 23 is turned on, a current flows through the coil 21, and energy is stored in the coil 21. Thereafter, when the switch element 23 is turned OFF, the energy stored in the coil 21 charges the capacitor 24 via the diode 22. As a result, the input voltage of the step-up chopper circuit, that is, the output voltage of the full-wave rectifier circuit 10 is stepped up, and a DC voltage Vout corresponding to the ratio of the time when the switch element 23 is turned on is generated at both ends of the capacitor 24.

  The power supply circuit 1 according to the present embodiment includes a control circuit 30. The control circuit 30 controls the output voltage of the booster circuit 20 to a desired voltage. The control circuit 30 may include a control unit 31 that controls the switch element 23 and a detection unit 32 that outputs a voltage Vm corresponding to the output voltage Vout of the booster circuit 20 to the control unit 31. Further, the control unit 31 may control the switch element 23 so that the output voltage Vm of the detection unit 32 becomes a predetermined value.

  The control unit 31 may be a known and well-known power factor correction control circuit, an example of which is shown in FIG. The control unit 31 illustrated in FIG. 3 includes an error amplifier 311, a capacitor 312, an input voltage detection circuit 313, a multiplier 314, a current detection circuit 315, an error amplifier 316, a zero current detection circuit 317, an RS latch circuit 318, and a buffer amplifier 319. It is configured to include. Hereinafter, the operation of the control unit 31 shown in FIG. 3 will be briefly described.

  When the switch element 23 is turned on, a current flows from the coil 21 via the switch element 23. The current from the coil 21 rises linearly from zero. When this current is detected by the current detection circuit 315 and reaches a reference value determined by the output voltage of the multiplier 314, a reset signal is output from the error amplifier 316 to the RS latch circuit 318, and the switch element 23 is turned OFF. .

  When the switch element 23 is turned off, a current flows from the coil 21 through the diode 22. The current from the coil 21 decreases linearly and returns to zero. When the current from the coil 21 returns to zero, a set signal is output from the zero current detection circuit 317 to the RS latch circuit 318, and the switch element 23 is turned on again.

  The reference value determined by the output voltage of the multiplier 314 described above is determined by the following operation.

  The error amplifier 311 compares the output voltage Vm of the detection unit 32 with the reference voltage Vref and outputs it. The capacitor 312 smoothes the output voltage of the error amplifier 311. As a result, the input voltage from the error amplifier 311 to the multiplier 314 is a positive predetermined value or a substantially DC voltage of the ground potential.

  The input voltage detection circuit 313 outputs to the multiplier 314 a voltage corresponding to the output voltage of the full-wave rectifier circuit 10, that is, the input voltage of the booster circuit 20.

  The multiplier 314 outputs the product of the output voltage of the error amplifier 311 smoothed by the capacitor 312 and the output voltage of the input voltage detection circuit 313 to the error amplifier 316. That is, when the output voltage of the error amplifier 311 is a positive predetermined value, the multiplier 314 outputs a voltage proportional to the AC input voltage subjected to full-wave rectification. On the other hand, when the output voltage of the error amplifier 311 is the ground potential, the multiplier 314 outputs the voltage of the ground potential.

  Therefore, when the output voltage Vm of the detection unit 32 is smaller than the reference voltage Vref, the control unit 31 performs ON / OFF control of the switch element 23 to boost the booster circuit 20, and the output voltage of the detection unit 32 becomes the reference voltage. When the voltage is larger than Vref, the switch element 23 is kept OFF and the booster circuit 20 is controlled not to be boosted. Note that part or all of the control unit 31 may be configured as a semiconductor integrated circuit.

  The detection unit 32 may have a known and well-known configuration that outputs a voltage Vm corresponding to the output voltage Vout of the booster circuit 20 to the control unit 31. An example of the configuration of the detection unit 32 is shown in FIG. The detection unit 32 shown in FIG. 4 includes a first resistor 321 (resistance value is R1), a second resistor 322 (resistance value is R2), and a third resistor 323 (resistance value is R3). And a switch 324.

  Here, the output voltage of the detection unit 32 when the switch 324 is OFF is Vm1, and the output voltage of the output voltage of the detection unit 32 when the switch 324 is ON is Vm2.

  When the switch 324 is OFF, the detection unit 32 outputs a voltage Vm1 represented by the following formula (1) proportional to the output voltage Vout of the booster circuit 20 to the control unit 31.

  When the switch 324 is ON, the detection unit 32 outputs a voltage Vm2 represented by the following expression (2) proportional to the output voltage Vout of the booster circuit 20 to the control unit 31.

  Here, the relationship represented by the following formula (3) is established.

  Therefore, the relationship Vm1> Vm2 is established.

  That is, even if Vout is constant, the output voltage Vm from the detection unit 32 to the control unit 31 can be changed by switching the switch 324.

  In the present embodiment, the second resistor 322, the third resistor 323, and the series circuit of the switch 324 are connected in parallel and Vm can be switched in two stages. And a series circuit of switches may be connected in parallel to the second resistor 322 so that Vm can be switched in multiple stages.

  The power supply circuit 1 according to the present embodiment includes a partial boost control circuit 40. The partial boost control circuit 40 is configured so that the output voltage of the booster circuit 20 exceeds the output voltage of the full-wave rectifier circuit 10 during a saturation period in which the absolute value of the input voltage of the full-wave rectifier circuit 10 exceeds a given voltage Vth. The control circuit 30 is partially boosted. The partial boost control circuit 40 may have a full-wave rectifier 41 in the input stage, and may receive the same input voltage as the full-wave rectifier circuit 10. The full-wave rectifying unit 41 may be a diode bridge circuit 50 including diodes D1 to D4 as shown in FIG.

  FIG. 5 is a circuit diagram of a partial boost control circuit 400 which is an example of the configuration of the partial boost control circuit 40. The input voltage Vin is an AC input voltage that has been full-wave rectified, and may be, for example, the output voltage of the full-wave rectifier 41 or the output voltage of the full-wave rectifier circuit 10.

  The partial boost control circuit 400 shown in FIG. 5 includes resistors 401 to 404, an NPN transistor 405, and capacitors 406 to 407.

  The input voltage Vin is divided by resistors 401 and 402, and the voltage Vd is input to the base of the NPN transistor 405. Therefore, ON / OFF of the NPN transistor 405 is determined by the value of the voltage Vd. That is, the voltage Vth can be arbitrarily set by adjusting the voltage dividing ratio of the resistors 401 and 402.

  The operation of the partial boost control circuit 400 shown in FIG. 5 will be briefly described below using the waveform diagram shown in FIG. A solid line in FIG. 6A indicates the input voltage Vin. The solid line in FIG. 6B indicates the output voltage Vo.

  When the NPN transistor 405 is turned off by the voltage Vd, the output voltage Vo becomes a voltage close to the power supply voltage Vcc (period T1). When the input voltage Vin increases and the voltage Vd increases and the transistor 405 is turned on, the output voltage Vo becomes a voltage close to 0 V (period T2). After that, when the input voltage Vin drops, the voltage Vd drops, and when the transistor 405 is turned off again, the output voltage Vo again becomes a voltage close to the power supply voltage Vcc (period T3).

  For example, when the switch 324 of the detection unit 32 is switched by the change of the output voltage Vo, the voltage of the booster circuit 20 is increased during a saturation period in which the absolute value of the input voltage of the full-wave rectifier circuit 10 exceeds a given voltage Vth. The control circuit 30 can be controlled so that the output voltage exceeds the output voltage of the full-wave rectifier circuit 10.

(2) Operation of Power Supply Circuit According to this Embodiment An example of the operation of the power supply circuit 1 according to this embodiment will be described with reference to the waveform diagram shown in FIG.

  FIG. 7A shows a voltage waveform of the AC input voltage AC. In the present embodiment, the positive peak voltage is Vac. FIG. 7B shows the voltage waveform of the output voltage of the full-wave rectifier circuit 10 (that is, the input voltage of the booster circuit 20) Vin. The output voltage Vin of the full-wave rectifier circuit 10 corresponds to the absolute value of the AC input voltage AC. When the partial boost control circuit 40 includes the full-wave rectification unit 41, the output voltage waveform of the full-wave rectification unit 41 is also the waveform shown in FIG.

  FIG. 7C shows a voltage waveform of the output voltage Vo of the partial boost control circuit 40. The partial boost control circuit 40 is configured so that the output voltage Vin of the full-wave rectifier circuit 10 (that is, the absolute value of the input voltage of the full-wave rectifier circuit 10) exceeds the given voltage Vth during the saturation period (period Tp). The control circuit 30 is controlled so that the output voltage of 20 exceeds the output voltage of the full-wave rectifier circuit 10. Therefore, the output voltage Vo operates so as to be different between the saturation period (period Tp) and the normal operation period (period Tn) other than the saturation period. In the present embodiment, the output voltage in the normal operation period (period Tn) is Vo1, and the output voltage in the saturation period (period Tp) is Vo2. The voltage Vth may be a voltage that satisfies the relationship Vth <Vac. For example, when the peak voltage Vac is 370V, the voltage Vth may be 270V.

  FIG. 7D is a waveform diagram showing the relationship between the output voltage Vout of the booster circuit 20 and the voltage waveform of the output voltage Vin of the full-wave rectifier circuit 10. The control circuit 30 controls the output voltage Vout of the booster circuit 20 to exceed the output voltage Vin of the full-wave rectifier circuit 10 based on the output voltage Vo of the partial booster control circuit 40. For example, the output voltage Vout of the booster circuit 20 may be controlled to increase when the output voltage Vo of the partial booster control circuit 40 becomes smaller than a predetermined value. In the present embodiment, the output voltage of the booster circuit 20 in the normal operation period (period Tn) is Vout1, and the output voltage of the booster circuit 20 in the saturation period (period Tp) is Vout2. The voltage Vout1 may be a voltage that satisfies the relationship Vout1 <Vac. The voltage Vout1 is a voltage that satisfies the relationship Vout1> Vth. Furthermore, the voltage Vout2 is a voltage that satisfies the relationship of Vout2> Vout1 and Vout2> Vac. For example, when the peak voltage Vac is 370V, the voltage Vout1 may be 300V and the voltage Vout2 may be 390V.

  Next, an example of the operation of the power supply circuit 1 according to the present embodiment will be described in order of time.

  First, when the output voltage Vin of the full-wave rectifier circuit 10 is lower than the voltage Vth (normal operation period; period Tn), the output voltage Vo of the partial boost control circuit 40 is the voltage Vo1. At this time, the control circuit 30 controls the booster circuit 20 so that the output voltage Vout of the booster circuit 20 becomes the output voltage Vout1 in the normal operation period.

  Next, in a period in which the output voltage Vin of the full-wave rectifier circuit 10 is higher than the voltage Vth (saturation period; period Tp), the output voltage Vo of the partial boost control circuit 40 is the voltage Vo2. At this time, the control circuit 30 controls the booster circuit 20 so that the output voltage Vout of the booster circuit 20 becomes the output voltage Vout2 during the saturation period.

  In the present embodiment, the configuration is described in which the output voltage Vout of the booster circuit 20 in the saturation period is controlled to be a rectangular wave, but the state where the output voltage Vout of the booster circuit 20 exceeds the input voltage Vin is described. Any waveform can be used as long as it can be maintained.

  For example, as shown in FIG. 8A, a configuration may be adopted in which the waveform of the output voltage Vout of the booster circuit 20 in the saturation period is stepped. Further, for example, as shown in FIG. 8B, a configuration may be adopted in which the waveform of the output voltage Vout of the booster circuit 20 in the saturation period is controlled to be a boosted waveform following the input voltage waveform. In this case, a limiter may be provided so that the output voltage Vout of the booster circuit 20 does not exceed a predetermined value.

  In this embodiment, the case where an AC voltage having a voltage Vac higher than the voltage Vth is input has been described. However, when an AC voltage having a voltage Vac not exceeding the voltage Vth is input, there is a saturation period. Without a normal operation period. Accordingly, even in this case, the power supply circuit 1 operates without causing any particular problem.

(3) Effects of the power supply circuit and the power supply circuit control method according to the present embodiment According to the power supply circuit and the power supply circuit control method according to the present embodiment, the output voltage Vout of the booster circuit 20 exceeds the input voltage Vin. Therefore, the average output voltage can be lowered while obtaining the power factor improvement effect by the booster circuit 20. For example, even when an input voltage of a plurality of voltages is assumed, a voltage smaller than an output voltage that operates even at the highest input voltage can be set as the output voltage Vout1 in the normal operation period. For example, even when the peak voltage Vac of the input voltage is constant, a voltage smaller than the peak voltage Vac can be set as the output voltage Vout1 during the normal operation period. Therefore, it is possible to provide a power supply circuit with improved power conversion efficiency and a method for controlling the power supply circuit.

  Further, when the partial boost control circuit 40 is configured to perform the partial boost control by controlling the detection unit 32, even if a part or all of the control unit 31 is implemented as an IC, it is usually implemented as an IC. By controlling the detection unit 32 that has not been performed, partial boosting control can be performed.

  Furthermore, when the partial boost control circuit 40 has a full-wave rectifier 41 in the input stage and receives the same input voltage as the full-wave rectifier circuit 10, it is not affected by the booster circuit 20 or the like. The partial boost control circuit 40 can appropriately detect the input voltage, and more appropriate control is possible. In addition, even when a filter for removing harmonics is arranged at the subsequent stage of the full-wave rectifier circuit 10, the partial boost control circuit 40 can appropriately detect the input voltage, and more appropriate control is possible.

2. Projector Power Supply Circuit FIG. 9 is an example of a circuit diagram of the projector power supply circuit according to the present embodiment. Note that portions common to the power supply circuit of FIG. 1 are denoted by the same reference numerals, and detailed description thereof is omitted.

  A projector power supply circuit 2 according to the present embodiment includes a power supply circuit 1. The configuration of the power supply circuit 1 is as already described with reference to FIGS. 1 to 5 and includes the full-wave rectifier circuit 10, the booster circuit 20, the control circuit 30, and the partial booster control circuit 40. The operation of the power supply circuit 1 is as already described with reference to FIGS.

  Projector power supply circuit 2 according to the present embodiment includes a step-down circuit 60. The step-down circuit 60 receives the output voltage Vout of the power supply circuit 1 and steps down to output a DC voltage Vdout.

  The step-down circuit 60 can have various known and well-known configurations. For example, a configuration such as a step-down chopper circuit 600 illustrated in FIG. The step-down chopper circuit 600 includes a switch element 601, a diode 602, a coil 603, and a capacitor 604, and the control circuit 605 may control the output voltage Vdout by switching ON / OFF of the switch element 601. . Further, for example, a configuration such as a flyback converter 610 shown in FIG. The flyback converter 610 includes a switch element 611, a flyback transformer 612, a diode 613, and a capacitor 614, and the control circuit 615 controls the output voltage Vdout by switching on / off of the switch element 611. Also good.

  According to the projector power supply circuit according to the present embodiment, the average output voltage of the booster circuit 20 at the front stage can be lowered, so that the conversion efficiency is improved also in the step-down circuit 60 at the rear stage. Therefore, it is possible to provide a projector power supply circuit having high conversion efficiency as a whole. Further, according to the projector power supply circuit according to the present embodiment, by including the step-down circuit 60 in the subsequent stage, even if the output voltage Vout of the previous step-up circuit 20 is different between the saturation period and the normal operation period, the step-down circuit 60 makes it possible to output a DC constant voltage.

3. Projector FIG. 11 is an example of a circuit diagram of a projector according to the present embodiment.

  Projector 100 according to the present embodiment includes a power supply circuit 200. The power supply circuit 200 generates and outputs a DC voltage 222 based on the input voltage 172 from the AC power supply 170. Note that an EMI filter 110 for removing radiated noise and conductive noise is included between the AC power supply 170 and the power supply circuit 200, and the power supply circuit 200 generates a DC voltage 222 based on the output voltage 112 of the EMI filter 110. It may be generated and output.

  The power supply circuit 200 may have the same configuration as the power supply circuit 1 described above, and includes a full-wave rectifier circuit 210, a booster circuit 200, a control circuit 230, and a partial booster control circuit 240. In the present embodiment, the operation of the power supply circuit 200 is the same as the operation of the power supply circuit 1.

  Projector 100 according to the present embodiment may include a flyback converter 120. The flyback converter 120 insulates the primary side and the secondary side by the flyback transformer 122 and generates a DC voltage 124 obtained by stepping down the DC voltage 222 output from the booster circuit 220 on the secondary side of the flyback transformer 122. It outputs to the cooling fan drive circuit 130 mentioned later.

  Projector 100 according to the present embodiment may include cooling fan drive circuit 130 and cooling fan 140. The cooling fan drive circuit 130 outputs a drive voltage 132 to the cooling fan 140.

  Projector 100 according to the present embodiment may include a ballast circuit 150 and a lamp 160. The ballast circuit 150 generates a lamp driving current 154 based on the output voltage 222 of the booster circuit 220 and drives the lamp 160. The ballast circuit 150 may include a step-down chopper circuit 152 that steps down the DC voltage 222.

  According to the projector according to the present embodiment, since the conversion efficiency of the step-up circuit and the step-down circuit (flyback converter, step-down chopper circuit) is improved, it is possible to provide a projector that is more power efficient than the related art.

  The present invention includes configurations that are substantially the same as the configurations described in the embodiments (for example, configurations that have the same functions, methods, and results, or configurations that have the same objects and effects). In addition, the invention includes a configuration in which a non-essential part of the configuration described in the embodiment is replaced. In addition, the present invention includes a configuration that exhibits the same operational effects as the configuration described in the embodiment or a configuration that can achieve the same object. Further, the invention includes a configuration in which a known technique is added to the configuration described in the embodiment.

  For example, in the power supply circuit 1 according to the present embodiment, the partial boost control circuit 40 is configured to perform the partial boost control by controlling the detection unit 32, but the configuration for directly controlling the control unit 31, for example, It may be configured to control the reference voltage Vref.

  Further, for example, in the power supply circuit 1 according to the present embodiment, the partial boost control circuit 40 has the configuration including the full-wave rectifier 41 in the input stage, but the partial boost of the output voltage of the full-wave rectifier circuit 10 is performed. A configuration in which the input voltage of the control circuit 40 is used may be employed.

FIG. 5 illustrates an example of a structure of a power supply circuit according to this embodiment. FIG. 5 illustrates an example of a structure of a power supply circuit according to this embodiment. FIG. 5 illustrates an example of a structure of a power supply circuit according to this embodiment. FIG. 5 illustrates an example of a structure of a power supply circuit according to this embodiment. FIG. 5 illustrates an example of a structure of a power supply circuit according to this embodiment. 4A and 4B illustrate an example of operation of a power supply circuit according to this embodiment. 4A and 4B illustrate an example of operation of a power supply circuit according to this embodiment. 4A and 4B illustrate an example of operation of a power supply circuit according to this embodiment. The figure for demonstrating an example of a structure of the power supply circuit for projectors which concerns on this Embodiment. The figure for demonstrating an example of a structure of the power supply circuit for projectors which concerns on this Embodiment. FIG. 4 is a diagram for explaining an example of a configuration of a projector according to the present embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Power supply circuit, 2 Projector power supply circuit, 10 Full wave rectifier circuit, 20 Booster circuit, 21 Coil, 22 Diode, 23 Switch element, 24 Capacitor, 30 Control circuit, 31 Control part, 32 Detection part, 40 Partial boost control circuit 41 Full-wave rectifier, 50 Diode bridge circuit, 60 Step-down circuit, 100 Projector, 110 EMI filter, 112 Output voltage, 120 Flyback converter, 122 Flyback transformer, 124 DC voltage, 130 Cooling fan drive circuit, 132 Drive voltage , 140 cooling fan, 150 ballast circuit, 152 step-down chopper circuit, 154 drive current, 160 lamp, 170 AC power supply, 172 input voltage, 200 power supply circuit, 210 full-wave rectifier circuit, 220 booster circuit, 222 DC voltage, 23 Control circuit, 240 partial boost control circuit, 311 error amplifier, 312 capacitor, 313 input voltage detection circuit, 314 multiplier, 315 current detection circuit, 316 error amplifier, 317 zero current detection circuit, 318 RS latch circuit, 319 buffer amplifier, 321 to 323 resistor, 324 switch, 400 partial boost control circuit, 401 to 404 resistor, 405 NPN transistor, 406 to 407 capacitor, 600 step-down chopper circuit, 601 switch element, 602 diode, 603 coil, 604 capacitor, 605 control circuit, 610 Flyback converter, 611 switch element, 612 flyback transformer, 613 diode, 614 capacitor, 615 control circuit, D1-D4 diode

Claims (6)

A full-wave rectifier circuit;
A booster circuit that boosts the output voltage of the full-wave rectifier circuit and outputs a DC voltage;
A power supply circuit including a control circuit for controlling the output voltage of the booster circuit to a desired voltage;
A portion that performs partial boost control of the control circuit so that the output voltage of the booster circuit exceeds the output voltage of the fullwave rectifier circuit in a saturation period in which the absolute value of the input voltage of the fullwave rectifier circuit exceeds a given voltage A power supply circuit including a boost control circuit. The power supply circuit according to claim 1,
The booster circuit includes a switch element capable of controlling an output voltage,
The control circuit includes a control unit that controls the switch element, and a detection unit that outputs a voltage corresponding to the output voltage of the booster circuit to the control unit,
The control unit controls the switch element so that the output voltage of the detection unit becomes a predetermined value,
The power supply circuit according to claim 1, wherein the partial boosting control circuit performs the partial boosting control by controlling the detection unit so as to lower an output voltage of the detection unit during the saturation period. A power supply circuit according to claim 1 or 2,
The partial boost control circuit has a full-wave rectifier in an input stage and receives the same input voltage as the full-wave rectifier circuit.   4. A projector power supply circuit, comprising: a step-down circuit for inputting and stepping down an output voltage of the power supply circuit according to claim 1.   A projector comprising the power supply circuit for a projector according to claim 4. A full-wave rectifier circuit;
A booster circuit that boosts the output voltage of the full-wave rectifier circuit and outputs a DC voltage;
A control method of a power supply circuit including a control circuit for controlling an output voltage of the booster circuit to a desired voltage,
Partial boost control of the control circuit so that the output voltage of the booster circuit exceeds the output voltage of the fullwave rectifier circuit in a saturation period in which the absolute value of the input voltage of the fullwave rectifier circuit exceeds a given voltage. A method for controlling a power supply circuit.

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