JP2005168146A - Switching power supply device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a switching power supply device capable of realizing further power-saving during low power consumption without using a constitution for executing the power supply without involving a power factor improving part. <P>SOLUTION: A current, which flows in a negative line 4 between a bridge diode 2 and a step-up chopper circuit 5 having a power factor improving function, is detected with an output power detecting circuit 11. When the detected output power exceeds a prescribed amount, a comparison circuit 14 executes the output for turning on the power factor improving function of the step-up chopper circuit 5 to the step-up chopper circuit 5. When the detected output power is less than the prescribed amount, the comparison circuit 14 executes the output for turning off the power factor improving function of the step-up chopper circuit 5 to the step-up chopper circuit 5. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to a switching power supply device used as a DC power supply for electrical equipment.

  Since electric devices such as facsimiles, telephones, copiers, other OA devices and home appliances require a stable and constant operating voltage, a switching power supply device that outputs a stabilized voltage has been conventionally used. . Also, in recent years, there are an increasing number of electrical devices that need to be supplied with power during standby other than the original operation (normal mode), that is, during low power consumption (power saving mode). The switching power supply device must always supply power to the electrical equipment. On the other hand, it is necessary to save power due to the recent energy situation. Therefore, it is important to reduce the power consumption of the switching power supply device during standby, which has a larger time ratio than the original operation time.

  By the way, the following are widely known as switching power supply devices. That is, the rectified voltage (pulsating flow) obtained from the AC power supply by the rectifier circuit is smoothed by the smoothing circuit and converted to a DC voltage. This DC voltage is interrupted by the switching element, and the switching output is supplied to the output rectifying / smoothing circuit to obtain an arbitrary DC voltage.

  In such a switching power supply device, when the smoothing circuit on the input side is a capacitor input type, the input current flows only during a period when the voltage after rectification is higher than the charging voltage of the input smoothing capacitor. There was a problem that the conduction angle was narrow and the power factor was lowered. Therefore, in order to solve this problem, conventionally, a switching power supply device including a boost chopper circuit having a power factor correction function has been used.

  However, the switching power supply device provided with such a boost chopper circuit saves power because the power factor is improved and reactive power is reduced, but compared with a switching power supply device that does not have a power factor improvement function, Since power loss accompanying the power factor improvement operation of the boost chopper circuit occurs, the power conversion efficiency is degraded accordingly. In particular, the power factor improvement function is operated even in a low power consumption state where there is no need for power factor improvement, such as when the device is on standby, and wasted power is wasted.

  Patent Document 1 discloses a power supply device configured to supply power to a device without going through a power factor improvement unit when the device is in a power saving mode.

In Patent Document 2, the output of the step-up chopper circuit is converted into a voltage by a transformer having an auxiliary winding on the primary side, a desired voltage is supplied to a load, and the positive voltage induced in the auxiliary winding is a capacitor. A switching power supply device is disclosed in which the output power supplied to the load is detected by introducing the power into the capacitor and the power factor correction function is not functioned according to the output power.
Japanese Patent Laid-Open No. 11-136858 (published on May 21, 1999) JP 2001-95236 A (published on April 6, 2001)

  However, in the power supply device disclosed in Patent Document 1, in order to be able to supply power without going through the power factor improvement unit, a power supply path without going through the power factor improvement unit, and In response to the switching mechanism between the power supply path via the power factor improvement unit and the power supply path not via the power factor improvement unit, a circuit equipped with a switch, a rectifier, etc. is required separately from the power factor improvement unit, and the number of parts is large. There was a problem of becoming.

  Further, in the switching power supply device disclosed in Patent Document 2, a lot of noise components are included in the positive voltage induced in the auxiliary winding of the transformer, and the positive voltage depends on the degree of coupling of the transformer. And depends on the load. That is, the output power detected using the positive voltage often includes an error. As a result, even when the electrical device is in the power saving mode, there is a problem that the power factor improving function is functioning, and sufficient power saving cannot be achieved.

  The present invention has been made in view of the above-described problems, and an object of the present invention is to further reduce power consumption at the time of low power consumption without using a configuration for supplying power without going through a power factor improvement unit. An object of the present invention is to provide a switching power supply device that can be used.

  In order to solve the above-described problem, a switching power supply according to the present invention is a switching power supply that converts a voltage output from a rectifier circuit by a DC-DC converter and supplies power to a load. The DC converter includes a pulse transformer and a main switching element provided in series with the primary winding of the pulse transformer, and an output voltage of the rectifier circuit is applied to output an input voltage to the DC-DC converter. However, the power factor improving means capable of turning on / off the power factor improving function for improving the power factor by expanding the conduction angle with respect to the output voltage of the rectifier circuit, and a current corresponding to the primary current of the pulse transformer. An input current detecting means for detecting and a capacitor are provided, the output of the input current detecting means is led into the capacitor, and the capacitor is charged. Output power detecting means for detecting the output power supplied to the load, determination means for determining whether or not the output power detected by the output power calculating means is a predetermined amount or more, and detection The power factor improvement function is turned on when the determination means determines that the output power is greater than or equal to a predetermined amount, while the determination means determines that the detected output power is less than the predetermined amount. And a power factor improvement function control means for turning off the power factor improvement function in the case of being performed.

  In order to solve the above problem, the switching power supply device of the present invention is configured such that the input current detecting means is a current transformer having a current path between the power factor improving means and the rectifier circuit as a primary side. It is characterized by being.

  In order to solve the above problem, the switching power supply device of the present invention is configured such that the output of the input current detection means is introduced into the capacitor via a diode and an element that quantitatively suppresses the charging current of the capacitor. It is characterized by that.

  In order to solve the above problems, the switching power supply device of the present invention is characterized in that the element is a resistor or an inductor.

  In the switching power supply device of the present invention, in order to solve the above-described problem, the determination unit determines that the detected output power is equal to or greater than a predetermined amount when the voltage value across the capacitor is equal to or greater than a predetermined voltage value. It is characterized by doing.

  In order to solve the above problems, the switching power supply device of the present invention is characterized in that the determination means includes a Zener diode, and the Zener voltage of the Zener diode corresponds to the predetermined voltage value.

  In order to solve the above problem, the switching power supply apparatus according to the present invention has an opening / closing means for supplying or shutting off the operating power to the power factor improving means when the power factor improving function control means is closed or opened. When the power factor improving means is not functioned, the opening / closing means shuts off the operating power supply to the power factor improving means.

  In the switching power supply device of the present invention, in order to solve the above problems, the opening / closing means is a transistor, and the power factor improvement function control means does not conduct the transistor when the power factor improvement means does not function. It is characterized by.

  In order to solve the above-described problem, the switching power supply device of the present invention is a switching power supply device that converts the voltage output from the rectifier circuit by a DC-DC converter and supplies power to a load. It is possible to turn on / off the power factor improvement function that improves the power factor by widening the conduction angle with respect to the output voltage of the rectifier circuit while the output voltage of the circuit is applied and the input voltage to the DC-DC converter is output. Power factor improvement means, and a control signal indicating the size of the load supplying power is received from the outside, and the power factor improvement function control for controlling on / off of the power factor improvement function by the control signal And a means.

  In order to solve the above-described problem, the switching power supply apparatus according to the present invention is configured such that the power factor correction function control unit supplies or shuts off the operation power to the power factor correction unit by closing or opening according to the control signal. And the switching means shuts off the operating power supply to the power factor improving means when the power factor improving means is not functioning.

  As described above, the switching power supply of the present invention is a switching power supply that converts the voltage output from the rectifier circuit into a voltage by a DC-DC converter and supplies power to a load. Comprises a pulse transformer and a main switching element provided in series with the primary winding of the pulse transformer, while the output voltage of the rectifier circuit is applied to output the input voltage to the DC-DC converter, A power factor improving means capable of turning on / off a power factor improving function for improving a power factor by expanding a conduction angle with respect to an output voltage of the rectifier circuit, an input current detecting means, an output power detecting means, and a judging means; The power factor improvement function is turned on when the determination means determines that the detected output power is greater than or equal to a predetermined amount, while the detected output Force is configured to and a power factor improving function control means for turning off said power factor improving function when it is determined by said determining means is less than a predetermined amount.

  Therefore, by detecting the current corresponding to the primary current of the pulse transformer, the power factor improving function of the power factor improving means is controlled according to the size of the load, and power is supplied to the load. Therefore, the power factor improvement function can be functioned when the load is in the normal mode, and the power factor improvement function can be prevented from functioning when the load is in the power saving mode. That is, when the load is in the power saving mode, it is possible to further save power by the power required for the power factor improving function of the power factor improving means.

  In addition, when the load is in the power saving mode, an input voltage can be applied to the DC-DC converter through the power factor improving means without operating the power factor improving function. Does not require a separate circuit. Therefore, the number of parts required for the another circuit can be reduced.

  As described above, there is an effect that it is possible to provide a switching power supply device that can further reduce power consumption at the time of low power consumption without using a configuration for supplying power without going through the power factor improvement unit.

  As described above, the switching power supply device according to the present invention has a configuration in which the input current detection unit is configured by a current transformer having a current path between the power factor improvement unit and the rectifier circuit as a primary side. is there.

  Therefore, the output of the input current detection means has a sine wave shape that does not include a negative component, and is not affected by other components, and therefore does not include noise. Therefore, by introducing the output voltage into the capacitor and charging the capacitor, there is no error in the output power supplied to the detected load, and the output power can be detected more accurately than in the past. Can do. In other words, the power saving mode state of the load can be detected with high accuracy, and the power factor improvement means can be prevented from functioning more reliably in the power saving mode, so that further power saving can be achieved.

  As described above, the switching power supply device of the present invention is configured such that the output of the input current detection means is introduced into the capacitor via a diode and an element that quantitatively suppresses the charging current of the capacitor. .

  Therefore, the charging voltage can be limited in a state where the charging voltage of the capacitor is proportional to the output power supplied to the load. Thereby, the output power can be detected based on the charging voltage, and the power consumption in the output power detection means can be reduced.

  As described above, the switching power supply device of the present invention has a configuration in which the element is a resistor or an inductor.

  Therefore, it is possible to detect the output power with a simple circuit configuration by changing the charging voltage of the capacitor in proportion to the output power supplied to the load.

  As described above, the switching power supply device according to the present invention has a configuration in which the determination unit determines that the detected output power is equal to or greater than a predetermined amount when the voltage value across the capacitor is equal to or greater than the predetermined voltage value. is there.

  Therefore, it is possible to easily determine whether or not the output power is greater than or equal to a predetermined amount by comparing the voltage value at both ends of the capacitor with the predetermined voltage value.

  As described above, in the switching power supply device of the present invention, the determination unit has a Zener diode, and the Zener voltage of the Zener diode corresponds to the predetermined voltage value.

  Therefore, there is an effect that the determination means can be realized by a simple configuration including a Zener diode.

  In the switching power supply device of the present invention, as described above, the power factor improvement function control means has an opening / closing means, and when the power factor improvement means is not functioned, the opening / closing means is the power factor improvement means. The operation power supply is cut off.

  Therefore, when the opening / closing means is in the closed state, the operating power is supplied to the power factor improving means and the power factor can be improved, whereas when the opening / closing means is in the open state, the operating power is not supplied to the power factor improving means. There is an effect that power saving can be achieved.

  As described above, in the switching power supply device of the present invention, the opening / closing means is a transistor, and the power factor improvement function control means is configured not to conduct the transistor when the power factor improvement means is not functioned.

  Therefore, when the determination means determines that the output power is greater than or equal to a predetermined amount, the operating power is supplied to the power factor improvement means to turn on the transistor. Thereby, power factor improvement can be performed. On the other hand, if the determination means determines that the output power is less than a predetermined amount, the transistor is not turned on, and therefore no operating power is supplied to the power factor correction means. Thereby, power saving can be achieved. As described above, the opening / closing means can be realized by a simple configuration of a transistor.

  As described above, the switching power supply device of the present invention is a switching power supply device that converts the voltage output from the rectifier circuit by a DC-DC converter and supplies power to the load, and outputs the output of the rectifier circuit. A power factor capable of turning on / off a power factor improvement function for improving a power factor by expanding a conduction angle with respect to an output voltage of the rectifier circuit while a voltage is applied to output an input voltage to the DC-DC converter. Improvement means, and power factor improvement function control means for receiving an external control signal indicating the magnitude of the load supplying power and controlling on / off of the power factor improvement function by the control signal. It is the composition which is provided.

  Therefore, by receiving a control signal from the outside, the power factor improving function of the power factor improving means is controlled according to the size of the load, and power is supplied to the load. Therefore, the power factor improvement function can be functioned when the load is in the normal mode, and the power factor improvement function can be prevented from functioning when the load is in the power saving mode. That is, when the load is in the power saving mode, it is possible to further save power by the power required for the power factor improving function of the power factor improving means.

  Further, since the control signal is received from the outside, it is not necessary to provide a means for determining whether or not the load is in the power saving mode state in the switching power supply device, and therefore the number of parts can be further reduced. Further, since the control signal is not affected by the components in the switching power supply device, it is obvious that noise or the like does not enter. Therefore, when the load is in the power saving mode, the power factor improving means can be prevented from functioning more reliably, and therefore further power saving can be achieved.

  Furthermore, the output power supplied to the load in the power saving mode usually varies depending on the type of the load, but it is not necessary to change the setting in the switching power supply by receiving the control signal from the outside. It is possible to flexibly cope with various types of loads.

  Further, when the load is in the power saving mode, the power factor improving means can be used in a state where the power factor improving function is not functioned, and there is no need to provide a circuit different from the power factor improving means as in Patent Document 1. . Therefore, the number of parts required for the another circuit can be reduced.

  As described above, there is an effect that it is possible to provide a switching power supply device that can further reduce power consumption at the time of low power consumption without using a configuration for supplying power without going through the power factor improvement unit.

  In the switching power supply device of the present invention, as described above, the power factor improvement function control means has an opening / closing means for supplying or shutting off the operating power to the power factor improvement means by closing or opening according to the control signal. When the power factor improving means is not functioned, the opening / closing means shuts off the operating power supply to the power factor improving means.

  Therefore, the opening / closing means is closed in response to the control signal, and the operating power is supplied to the power factor improving means to improve the power factor, while the opening / closing means is open in response to the control signal. Is not supplied to the power factor improving means, and thus the power can be saved.

[Embodiment 1]
An embodiment of the switching power supply device according to the present invention will be described below with reference to FIGS.

  FIG. 1 is an electric circuit diagram showing a schematic configuration of the switching power supply device according to the present embodiment. The switching power supply device includes a bridge diode 2 connected to a commercial AC power supply 1, a power factor improving means having a power factor improving function, such as a boost chopper circuit (power factor improving means) 5, a smoothing capacitor 7, a voltage A conversion circuit 8, an output power detection circuit 11, a comparison circuit 14, and a positive output terminal 9 and a negative output terminal 10 connected to the output terminal of the voltage conversion circuit 8 are provided. In this switching power supply device, the voltage output from the bridge diode 2 is input to the DC-DC converter after the smoothing capacitor 7 after passing through the step-up chopper circuit 5. The DC-DC converter converts this voltage and supplies power to the load.

  The bridge diode (rectifier circuit) 2 performs full-wave rectification on the AC voltage obtained from the AC power source 1, and generates an applied voltage to the primary side of a transformer 22 (described later) provided in the voltage conversion circuit 8. A step-up chopper circuit 5 is connected to the output terminal of the bridge diode 2 via a positive polarity line 3 and a negative polarity line 4. The step-up chopper circuit (power factor improving means) 5 boosts the rectified voltage output from the bridge diode 2 to expand the current inflow period to the smoothing capacitor 7, that is, a DC-DC converter for the output voltage of the bridge diode 2. Widen the conduction angle to reduce harmonics and improve power factor. This power factor improvement function can be turned on / off. Note that the negative polarity line 4 is a line that applies the same potential to the smoothing capacitor 7 and the voltage conversion circuit 8 while maintaining the same potential in the boost chopper circuit 5. The smoothing capacitor 7 is connected between the positive polarity line 6 and the negative polarity line 4 connected to the output terminal of the boost chopper circuit 5. The voltage conversion circuit 8 is connected to the positive polarity line 6 and the negative polarity line 4.

  The AC voltage obtained from the AC power source 1 is rectified and smoothed through the bridge diode 2, the step-up chopper circuit 5, and the smoothing capacitor 7. The smoothed voltage is input to the voltage conversion circuit 8. The voltage conversion circuit 8 converts the input voltage into a desired voltage, and then supplies the converted voltage to a load (electric device) (not shown) via the positive output terminal 9 and the negative output terminal 10. The switching operation of the FET 19 is controlled so that the voltage between the positive output terminal 9 and the negative output terminal 10 is maintained at a predetermined DC voltage. An output power detection circuit 11 is provided in the negative polarity line 4 at the output end of the bridge diode 2. The comparison circuit 14 receives an input from the output power detection circuit 11 and outputs it to the boost chopper circuit 5.

  The output power detection circuit (output power detection means) 11 also serves as input current detection means for detecting a current flowing in the negative line 4 between the bridge diode 2 and the boost chopper circuit 5. The output power detection circuit 11 outputs this detection result to the comparison circuit 14. The comparison circuit (determination means) 14 receives the detection result, determines whether to turn on or off the power factor correction function of the boost chopper circuit 5, and sends the determination result to the boost chopper circuit 5. The currents flowing through the negative polarity line 4 are respectively applied to the negative polarity line 4 between the voltage conversion circuit 8 and the boost chopper circuit 5 and also to the negative polarity line 4 between the boost chopper circuit 5 and the bridge diode 2. The waveform flows corresponding to the magnitude of the load connected to the positive output terminal 9 and the negative output terminal 10.

  When the boost chopper circuit 5 receives the determination result that the power factor correction function is not functioned, the boost chopper circuit 5 stops the boost function. As a result, the output voltage of the bridge diode 2 is output to the smoothing capacitor 7 as it is, and the power loss can be reduced by the amount consumed by the boost chopper circuit 5. That is, the output voltage of the bridge diode 2 passes through the boost chopper circuit 5. At this time, the power factor is not improved, but since the electric device receiving power from the switching power supply is in the power saving mode, the power factor does not need to be improved and there is no problem.

  On the other hand, when receiving the determination result for operating the power factor correction function, the boost chopper circuit 5 operates the boost function to boost the output voltage of the bridge diode 2. Thereby, a power factor is improved.

  FIG. 2 is an electric circuit diagram showing a control means for the power factor correction function in the step-up chopper circuit 5 in the switching power supply device shown in FIG.

  As shown in FIG. 2, the operation power supply of the boost chopper circuit 5 is supplied from the voltage conversion circuit 8 to the boost chopper circuit 5 through the operation power supply line 13. The operation power supply line 13 is connected to a chopper control circuit (power factor improvement function control means) 12 provided in the boost chopper circuit 5. The chopper control circuit 12 has opening / closing means such as a switch, for example, and the power factor improvement function can be caused to function by the opening / closing operation. That is, when the power factor improvement function is functioned, the chopper control circuit 12 closes the switch (ON) so that the operation power is supplied to the boost chopper circuit 5. On the other hand, when the power factor correction function is not functioned, the chopper control circuit 12 opens the switch (off) so that the operation power is not supplied to the boost chopper circuit 5. Thus, since the power factor correction function can be prevented from functioning by shutting off the operating power supply to the boost chopper circuit 5, it is not necessary to provide a circuit different from the boost chopper circuit as in Patent Document 1. Therefore, the number of parts required for the another circuit can be reduced.

  Note that the operation power supply of the step-up chopper circuit 5 does not necessarily have to be supplied from the voltage conversion circuit 8 and may be supplied from another power supply line or the positive polarity line 3. However, even in such a case, the step-up chopper circuit 5 is connected to the line via the chopper control circuit 12 for controlling the supply and cutoff of the operating power.

  FIG. 3 is an electric circuit diagram showing an internal configuration of the voltage conversion circuit 8 and the output power detection circuit 11 in the switching power supply device as shown in FIG. In the switching power supply according to the present embodiment, for example, a PWM control type flyback converter circuit is employed. Note that members having the same functions as those in FIG. 2 are denoted by the same reference numerals, and detailed description thereof is omitted.

  Between the positive line 6 and the negative line 4, a series circuit of a primary winding 22 a of a transformer (pulse transformer) 22 and a field effect transistor (FET) (main switching element) 19 is connected. Yes. The secondary winding 22 c of the transformer 22 forms a series circuit with the diode 23, and this series circuit is connected to the smoothing capacitor 24. The relationship between the current inflow direction with respect to the primary winding 22a and the secondary winding 22c of the transformer 22, the direction of the magnetic flux generated by the current, and the direction of the mutual induction electromotive force is as shown by the polarity in the figure. Is connected to the secondary winding 22 c so that the cathode side is connected to the positive output terminal 9. The smoothing capacitor 24 is connected between the positive output terminal 9 and the negative output terminal 10.

  The current flowing in the negative electrode surname line 4 between the voltage conversion circuit 8 and the smoothing capacitor 7 is equal to the current flowing in the primary winding 22 a of the transformer 22, that is, the primary current of the transformer 22. Further, a current corresponding to the current flowing between the smoothing capacitor 7 and the primary winding 22 a of the transformer 22 flows between the smoothing capacitor 7 and the step-up chopper circuit 5. Therefore, a current corresponding to the primary current of the transformer 22 flows through the negative line 4 between the step-up chopper circuit 5 and the bridge diode 2.

  A PWM control circuit 15 is connected to the gate electrode of the FET 19. A smoothing capacitor 21 is connected to the PWM control circuit 15, and a startup power supply (not shown) for charging the smoothing capacitor 21 is connected to the smoothing capacitor 21. Further, a series circuit of the auxiliary winding 22 b of the transformer 22 and the diode 20 is connected to the smoothing capacitor 21. The relationship between the current inflow direction to the auxiliary winding 22b, the direction of the magnetic flux generated by the current, and the direction of the mutual induced electromotive force is as shown by the polarity in the figure, and the cathode side of the diode 20 is connected to the positive terminal of the smoothing capacitor 21. Has been.

  When the AC power source 1 is connected to the switching power source device, a rectified voltage is output from the bridge diode 2 to the positive polarity line 3 and the negative polarity line 4. At this time, since the step-up chopper circuit 5 is not yet operated, the rectified current is not improved in power factor and is output to the smoothing capacitor 7 as it is.

  A start-up power supply (not shown) charges the capacitor 21, and when the charging voltage reaches a predetermined voltage or higher, the PWM control circuit 15 starts operation. The FET 19 is driven by the PWM control circuit 15 and performs on / off control of the current flowing through the primary winding 22 a of the transformer 22. The embodiment illustrated here relates to a flyback converter circuit, and an induced voltage is generated in the secondary winding 22 c of the transformer 22 during the OFF period of the FET 19. The induced voltage is rectified and smoothed by the diode 23 and the capacitor 24, and supplied from the positive output terminal 9 and the negative output terminal 10 to a load (not shown).

  An output voltage detection circuit (not shown) detects a voltage between the positive output terminal 9 and the negative output terminal 10. Information on the detected voltage is transmitted to the PWM control circuit 15 via a photocoupler (not shown). The PWM control circuit 15 controls the ON period of the FET 19 based on the received information, and as a result, controls the output voltage to a predetermined value.

  When the switching power supply device starts up, the PWM control circuit 15 and other auxiliary circuits (not shown) are driven by the current supplied from the auxiliary winding 22b of the transformer 22 via the diode 20. The operation of the startup power supply (not shown) is stopped.

  Next, the internal configuration and function of the output power detection circuit 11 will be described. The output power detection circuit 11 connected to the negative polarity line 4 at the output end of the bridge diode 2 includes a current transformer (input current detection means) 40. The current transformer 40 is connected with a negative line 4 serving as a current path between the output terminal of the bridge diode 2 and the step-up chopper circuit 5 as a primary side. Further, the output power detection circuit 11 includes a circuit for introducing the output voltage of the current transformer 40 as an output of the current transformer 40 to the capacitor 16 via the diode 17 and the resistor (element) 18 and charging the capacitor 16. Yes.

  By the operations of the PWM control circuit 15 and the step-up chopper circuit 6, a full-wave rectified sinusoidal current flows in the negative polarity line 4 of the bridge diode 2, and a full-wave rectified sinusoidal voltage is induced in the current transformer 40. A current flows into the capacitor 16 through the diode 17 and the resistor 18. Here, as the output power to the load (not shown) increases, the effective value of the current flowing through the current transformer 40 increases, and a larger amount of current flows into the capacitor 16 accordingly. That is, the voltage applied to the capacitor 16 follows the effective value of the input current, and does not include noise or the like generated by components in the switching power supply device, such as the transformer 22. Thereby, the output power detection circuit 11 can detect the output power supplied to the load (not shown) with high accuracy.

  FIG. 4 shows waveforms of the current transformer primary side, which is the input current, the secondary side voltage of the current transformer 40, and the charging voltage of the capacitor 16, for each of the power saving mode and the normal mode. A voltage similar to the current waveform flowing on the primary side of the current transformer 40 is generated on the secondary side of the current transformer 40. Since the output of the current transformer 40 has a sine wave shape that does not include a negative component and is not affected by other components, noise is not included. In addition, the charging voltage of the capacitor 16 rapidly increases at the switching point from the power saving mode to the normal mode.

  The resistor 18 is an element for quantitatively suppressing the charging current of the capacitor 16 and limiting the charging voltage of the capacitor 16. Since the charging voltage of the capacitor 16 can be limited, the power consumed by the output power detection circuit 11 can be reduced. The charging voltage of the capacitor 16 limited by the resistor 18 changes in proportion to the output power supplied to a load (not shown). Thereby, even if the charging voltage of the capacitor 16 limited by the resistor 18 is used, the output power supplied to the load (not shown) can be detected with high accuracy.

  The resistor 18 preferably has a high resistance value. Thereby, the current flowing into the capacitor 16 can be suppressed, and the power consumed in the output power detection circuit 11 can be further reduced. Therefore, the output power detection function can be achieved with a small amount of power consumption. In addition, the resistor 18 can be replaced with an inductor, and this element may be any element that suppresses the charging current quantitatively. By using the resistor 18 or the inductor as an element for quantitatively suppressing the charging current of the capacitor 16, the charging voltage of the capacitor 16 is changed in proportion to the output power supplied to the load with a simple circuit configuration. And output power can be detected.

  The charging voltage of the capacitor 16 is transmitted to the comparison circuit (determination means) 14. The comparison circuit 14 compares the charging voltage of the capacitor 16 with a reference voltage provided in the comparison circuit 14. Here, the reference voltage is set to the charging voltage of the capacitor 16 corresponding to the maximum value of the output power when the load (not shown) that outputs power from the positive output terminal 9 and the negative output terminal 10 is in the power saving mode. Thus, the comparison circuit 14 can determine whether or not the load is in the power saving mode. That is, the comparison circuit 14 determines that the electric device is in the power saving mode when the charging voltage of the capacitor 16 is lower than the reference voltage, and the electric circuit when the charging voltage of the capacitor 16 is higher than the reference voltage. It can be determined that the device is in the normal mode. That is, in the switching power supply device, it is possible to self-determine whether the electric device that supplies power is in the normal mode or the power saving mode.

  When the charging voltage of the capacitor 16 is lower than the reference voltage, that is, when the comparison circuit 14 determines that the electric device is in the power saving mode, the comparison circuit 14 indicates that the electric device is in the power saving mode. The determination result is sent to the boost chopper circuit 5. The chopper control circuit 12 provided on the operation power supply line 13 of the boost chopper circuit 5 that has received the determination result turns off the internal switch. As a result, the supply of the operating power from the operating power supply line 13 to the boost chopper circuit 5 is stopped, the power factor improving function does not function, and the power loss can be reduced correspondingly.

  When the charging voltage of the capacitor 16 is larger than the reference voltage, that is, when the comparison circuit 14 determines that the electric device is in the normal mode, the comparison circuit 14 indicates that the electric device is in the normal mode. The determination result is sent to the boost chopper circuit 5, and the switch of the chopper control circuit 12 provided on the operation power supply line 13 of the boost chopper circuit 5 that has received the determination result is turned on. As a result, the operating power is supplied from the operating power supply line 13 to the boost chopper circuit 5, and the boost chopper circuit 5 operates to improve the power factor.

  Thus, the comparison circuit 14 determines that the detected output power is equal to or greater than a predetermined amount when the voltage value across the capacitor 16 is equal to or greater than the predetermined voltage value. Therefore, it is possible to easily determine whether or not the output power is greater than or equal to the predetermined amount by comparing the voltage value across the capacitor 16 with the predetermined voltage value.

  Next, the internal configurations and functions of the boost chopper circuit 5 and the comparison circuit 14 will be described with reference to FIG. FIG. 5 is an electric circuit diagram showing a specific configuration of boost chopper circuit 5 and comparison circuit 14 in FIG. In addition, the same code | symbol is attached | subjected to the member which has the same function as FIG. 3, and detailed description is abbreviate | omitted.

  In the step-up chopper circuit 5, a series circuit including a resistor 26 and a resistor 27 is connected between the positive polarity line 3 and the negative polarity line 4 with the resistance 26 as the positive polarity side line 3 side. Is connected to the input terminal 40 of the power factor correction control circuit 30. A series circuit including a resistor 31 and a resistor 32 is connected in parallel with the smoothing capacitor 7 between the positive polarity line 6 and the negative polarity line 4 with the resistor 31 as the positive polarity line 6 side. The connection point with 32 is connected to the input terminal 41 of the power factor correction control circuit 30. Between the connection point of the resistor 26 and the positive line 3 and the connection point of the resistor 31 and the positive line 6, a series circuit including the choke coil 25 and the diode 29 connects the choke coil 25 to the bridge diode. Connected as two sides. The cathode of the diode 29 is connected to the positive polarity line 6. Further, the switching transistor 28 is connected between the connection point of the choke coil 25 and the diode 29 and the negative polarity line 4, and the gate electrode of the switching transistor 28 is the output terminal of the power factor correction control circuit 30. 42.

  The series circuit including the resistor 26 and the resistor 27 steps down the voltage between the positive polarity line 3 and the negative polarity line 4 by resistance voltage division and inputs the voltage from the input terminal 40 to the power factor correction control circuit 30. The series circuit composed of the resistor 31 and the resistor 32 steps down the charging voltage of the smoothing capacitor 7 by resistance voltage division and inputs the voltage from the input terminal 41 to the power factor correction control circuit 30.

  The power factor correction control circuit 30 sends a drive signal for the switching transistor 28 from the output terminal 42 to control the switching transistor 28 on / off.

  The boosting mechanism is usually the same as a general boosting chopper circuit. During the ON period of the switching transistor 28, a current flows from the positive line 3 of the bridge diode 2 through the choke coil 25 to the switching transistor 28, and excitation energy is accumulated in the choke coil 25. When the switching transistor 28 is turned off, the boosted current flows from the positive polarity line 3 of the bridge diode 2 into the smoothing capacitor 7 through the choke coil 25 and the diode 29 by the excitation energy.

  The power factor correction control circuit 30 monitors the charging voltage level of the smoothing capacitor 7 at the input terminal 41, and when the charging voltage level is higher than a predetermined voltage, the peak value of the current waveform flowing through the choke coil 25 is low overall. Thus, the switching transistor 28 is controlled to be turned on / off, and conversely, when the charging voltage level is lower than a predetermined voltage, the switching transistor 28 is set so that the peak value of the current waveform flowing through the choke coil 25 is increased as a whole. ON / OFF control. Thereby, the charging voltage of the smoothing capacitor 7 becomes a predetermined constant voltage value.

  The comparison circuit 14 shown in FIG. 3 includes an NPN transistor 35, a Zener diode 36, and resistors 34 and 37. The cathode of the Zener diode 36 is connected to the connection point between the resistor 18 and the capacitor 16, and the base of the NPN transistor 35 is connected to the anode of the Zener diode 36 via the resistor 37. Furthermore, the emitter of the NPN transistor 35 is connected to the other terminal of the capacitor 16. The collector of the NPN transistor 35 is connected via a resistor 34 to the base of a PNP transistor 33 of the chopper control circuit 12 described later.

  When the charging voltage of the capacitor 16 is larger than the Zener voltage of the Zener diode 36, a current flows from the cathode toward the anode, the NPN transistor 35 is turned on, and the collector of the NPN transistor 35 becomes a low voltage level. When the charging voltage of the capacitor 16 is smaller than the Zener voltage of the Zener diode 36, no current flows from the cathode to the anode, so that the NPN transistor 35 is turned off and the collector of the NPN transistor 35 is at a high voltage level. become.

  The chopper control circuit 12 comprises a PNP transistor (opening / closing means) 33, the emitter is connected to the positive terminal of the capacitor 21, and the collector is connected to the operation power supply receiving terminal 43 of the power factor correction control circuit 30, In addition, the base is connected to the collector of the NPN transistor 35 via a resistor 34 that serves as a base current limiting resistor. As described above, when the charging voltage of the capacitor 16 is larger than the Zener voltage of the Zener diode 36, the NPN transistor 35 is turned on, the voltage level of the base of the PNP transistor 33 is lowered to the low level, and the PNP transistor 33 is turned on. Therefore, the operating power is supplied from the operating power supply line 13 and the power factor correction control circuit 30 operates. On the contrary, when the charging voltage of the capacitor 16 is smaller than the Zener voltage of the Zener diode 36, the NPN transistor 35 is turned off, the base voltage level of the PNP transistor 33 is raised to a high level, and the PNP transistor 33 is turned off. The operation power is not supplied from the operation power supply line 13, and the operation of the power factor correction control circuit 30 is stopped.

  As described above, the comparison circuit 14 includes the Zener diode 36, and the Zener voltage of the Zener diode 36 corresponds to the predetermined voltage value compared with the voltage value across the capacitor 16. Therefore, the determination means can be realized by a simple configuration including the Zener diode 36. Further, by using an opening / closing means having a simple configuration such as the PNP transistor 33 which is a switch element, a power factor improvement control means can be realized with a simple configuration.

  As described above, the switching power supply according to the present embodiment includes the power factor improving means such as the boost chopper circuit 5 having the power factor improving function and the FET (main switching element) 19 having the switching function. A switching power supply device that supplies the output voltage from the power factor improving means to the load via the FET 19, has a capacitor 16, and is connected to the negative polarity line 4 at the output end of the bridge diode 2. An output power detection circuit (output power detection means) 11 that detects the output power supplied to the load by introducing the output voltage of the current transformer 40 into the capacitor 16 and charging the capacitor 16 is detected. The comparison circuit (determination means) 14 for determining whether or not the output power is greater than or equal to a predetermined amount and the detected output power is greater than or equal to the predetermined amount. A chopper that turns on the power factor improving function of the power factor improving means when judged by the circuit 14 and turns off the power factor improving function of the power factor improving means when judged to be less than a predetermined amount. And a control circuit (power factor improvement function control means) 12.

  Therefore, by detecting the current corresponding to the primary current of the transformer 22, the power factor improving function of the power factor improving means is controlled according to the size of the load, and power is supplied to the load. Therefore, the power factor improvement function can be functioned when the load is in the normal mode, and the power factor improvement function can be prevented from functioning when the load is in the power saving mode. That is, when the load is in the power saving mode, it is possible to further save power by the power required for the power factor improving function of the power factor improving means.

  In addition, when the load is in the power saving mode, an input voltage can be applied to the DC-DC converter through the power factor improving means without operating the power factor improving function. Does not require a separate circuit. Therefore, the number of parts required for the another circuit can be reduced.

  As described above, it is possible to provide a switching power supply device that can further save power during low power consumption without using a configuration for supplying power without going through the power factor improving unit.

In addition, a switching power supply that can self-determine the state of power supplied to the load within the switching power supply and cannot receive a signal from the connected electrical device, such as an AC adapter. Can be realized.
[Embodiment 2]
Another embodiment of the switching power supply device according to the present invention will be described below with reference to FIG. For convenience of explanation, members having the same functions as those in the drawings described in the first embodiment are given the same reference numerals, and descriptions thereof are omitted.

  FIG. 6 is a circuit diagram showing a specific configuration example of the switching power supply device according to the present embodiment.

  The difference from the first embodiment is that the transistor side of the photocoupler 38 is connected to the base of the PNP transistor 33 of the chopper control circuit 12 via a resistor 34 which is a base current limiting resistor, instead of the comparison circuit 14 of FIG. It is that. Further, the output power detection circuit 11 of FIGS. 1 to 3 and FIG. 5 is not provided. The collector of the transistor of the photocoupler 38 is connected to the resistor 34, and the emitter is grounded. In addition, a control signal 39 from an electric device (not shown) (not shown) is input to the photocoupler 38.

  The control signal 39 is a signal indicating the size of the load supplied with power by the switching power supply device. For example, when an electrical device as a load is connected and the electrical device is in the power saving mode, the control signal 39 is at a low level. When the electric device is in the normal mode, it becomes a high level signal. Since the control signal 39 is directly derived from the electric device, the operation state of whether the electric device is in the power saving mode or the normal mode can be indicated with higher accuracy.

  When the control signal 39 is at a low level, the transistor side of the photocoupler 38 is off, the base voltage level of the PNP transistor 33 is raised to a high level, and the PNP transistor 33 is turned off. The power is not supplied, and the operation of the power factor correction control circuit 30 is stopped. Conversely, when the control signal 39 is at a high level, the transistor side of the photocoupler 38 is turned on, so that the voltage level at the base of the PNP transistor 33 is lowered to a low level and the PNP transistor 33 is turned on. The power factor correction control circuit 30 operates by supplying the operation power from the power supply.

  As described above, the switching power supply according to the present embodiment is a switching power supply that supplies power factor improving means such as the boost chopper circuit 5 having a power factor improving function and the output voltage from the boost chopper circuit 5 to a load. A chopper that receives a control signal 39 according to the operating state of the load from the outside and controls whether the power factor improvement function of the boost chopper circuit 5 is turned on or off by the control signal 39 A control circuit (power factor improvement function control means) 12 is provided.

  According to the above configuration, the power factor improving function of the step-up chopper circuit 5 is controlled based on the state of the load, and power is supplied to the load. Therefore, the power factor improvement function can be functioned when the load is in the normal mode, and the power factor improvement function can be prevented from functioning when the load is in the power saving mode. That is, when the load is in the power saving mode, it is possible to further save power by the amount of power required for the boost chopper circuit 5.

  In addition, since the control signal 39 is received from the outside, it is not necessary to provide a means for determining whether or not the load is in the power saving mode state in the switching power supply device, so that the number of parts can be further reduced. Furthermore, since the control signal 39 is not affected by the components in the switching power supply device, it is obvious that noise or the like does not enter. Therefore, when the load is in the power saving mode, the boost chopper circuit 5 can be prevented from functioning more reliably, and thus further power saving can be achieved.

  Further, the output power supplied to the load in the power saving mode usually varies depending on the type of the load, but it is not necessary to change the setting in the switching power supply by receiving the control signal 39 from the outside. It is possible to flexibly cope with various types of loads.

  In addition, when the load is in the power saving mode, an input voltage can be applied to the DC-DC converter through the power factor improving means without operating the power factor improving function. Does not require a separate circuit. Therefore, the number of parts required for the another circuit can be reduced.

  As described above, it is possible to provide a switching power supply device that can further save power during low power consumption without using a configuration for supplying power without going through the power factor improving unit.

  Further, the PNP transistor 33 is closed in response to the control signal 39, so that the operating power is supplied to the power factor improving means and the power factor is improved. On the other hand, the PNP transistor 33 is opened according to the control signal 39, so that the operating power supply is not supplied to the power factor improving means, so that power saving can be achieved. Further, by using an opening / closing means having a simple configuration such as the PNP transistor 33 which is a switch element, a power factor improvement control means can be realized with a simple configuration.

  The present invention is not limited to the above-described embodiments, and various modifications are possible within the scope shown in the claims, and embodiments obtained by appropriately combining technical means disclosed in different embodiments. Is also included in the technical scope of the present invention.

  The present invention can be used for a switching power supply device.

1, showing an embodiment of the present invention, is a circuit block diagram illustrating a configuration of a switching power supply device. FIG. FIG. 2 is a circuit block diagram showing the configuration of the switching power supply device of FIG. 1 in more detail. FIG. 3 is a circuit block diagram showing the configuration of the switching power supply device of FIG. 2 in more detail. FIG. 4 is a waveform diagram showing various voltage / current waveforms in an output power detection circuit provided in the switching power supply device of FIG. FIG. 4 is a circuit block diagram showing the configuration of the switching power supply device of FIG. 3 in more detail. The other embodiment of this invention is shown and it is a circuit block diagram which shows the structure of a switching power supply device.

Explanation of symbols

2 Bridge diode (rectifier circuit)
5 Boost chopper circuit (Power factor improvement means)
11 Output power detection circuit (output power detection means)
12 Chopper control circuit (Power factor improvement function control means)
14 Comparison circuit (determination means)
16 Capacitor 18 Resistance (element)
22 Transformer (pulse transformer)
22a Primary winding 33 PNP transistor (opening / closing means, transistor)
36 Zener diode 39 Control signal 40 Current transformer (input current detection means)

Claims (10)

A switching power supply that supplies voltage to a load by converting a voltage after being output from a rectifier circuit by a DC-DC converter,
The DC-DC converter includes a pulse transformer and a main switching element provided in series with the primary winding of the pulse transformer,
On / off of a power factor improvement function for improving the power factor by widening the conduction angle with respect to the output voltage of the rectifier circuit while the output voltage of the rectifier circuit is applied to output the input voltage to the DC-DC converter Power factor improvement means that can
Input current detecting means for detecting a current corresponding to a primary current of the pulse transformer;
An output power detecting means for detecting the output power supplied to the load by introducing an output of the input current detecting means into the capacitor and charging the capacitor;
Determining means for determining whether or not the output power detected by the output power determining means is a predetermined amount or more;
When the determination means determines that the detected output power is greater than or equal to a predetermined amount, the power factor improvement function is turned on, while the detection means indicates that the detected output power is less than the predetermined amount. A switching power supply comprising: a power factor correction function control unit that turns off the power factor correction function when judged.   2. The switching power supply device according to claim 1, wherein the input current detection unit includes a current transformer having a current path between the power factor improvement unit and the rectifier circuit as a primary side.   2. The switching power supply device according to claim 1, wherein an output of the input current detection unit is introduced into the capacitor via a diode and an element that quantitatively suppresses a charging current of the capacitor.   The switching power supply device according to claim 3, wherein the element is a resistor or an inductor.   2. The switching power supply device according to claim 1, wherein the determination unit determines that the detected output power is equal to or greater than a predetermined amount when a voltage value across the capacitor is equal to or greater than a predetermined voltage value. The determination means has a Zener diode,
6. The switching power supply device according to claim 5, wherein a Zener voltage of the Zener diode corresponds to the predetermined voltage value. The power factor improvement function control means has an opening / closing means for supplying or shutting off the operation power to the power factor improvement means by closing or opening,
The switching power supply device according to any one of claims 1 to 6, wherein when the power factor improving means is not functioned, the opening / closing means shuts off an operating power supply to the power factor improving means. The opening / closing means is a transistor;
8. The switching power supply device according to claim 7, wherein the power factor improvement function control means does not conduct the transistor when the power factor improvement means does not function. A switching power supply that supplies voltage to a load by converting a voltage after being output from a rectifier circuit by a DC-DC converter,
On / off of a power factor improvement function for improving the power factor by widening the conduction angle with respect to the output voltage of the rectifier circuit while the output voltage of the rectifier circuit is applied to output the input voltage to the DC-DC converter Power factor improvement means that can
Power factor improvement function control means for receiving a control signal indicating the size of the load supplying power from the outside and controlling on / off of the power factor improvement function by the control signal. A switching power supply device. The power factor improvement function control means has an opening / closing means for supplying or shutting off the operating power to the power factor improvement means by closing or opening according to the control signal,
10. The switching power supply device according to claim 9, wherein when the power factor improving means is not functioned, the switching means shuts off an operating power supply to the power factor improving means.

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