JP3294211B2 - Switching power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching power supply for converting power from AC to DC or from DC to DC, and more particularly to a switching power supply capable of converting power with high efficiency and high power factor.

[0002]

2. Description of the Related Art As a switching power supply of this kind,
A switching power supply 41 (hereinafter, referred to as “power supply 4
1 ") is conventionally known. This power supply 4
Reference numeral 1 denotes, for example, a forward type DC / DC converter, which includes a transformer 11. The power supply 41
Is composed of an input circuit 12 having an input filter and a rectifier circuit such as a diode bridge in a primary circuit on a primary winding 11a side of a transformer 11, and an active filter circuit for improving a power factor and having a smoothing capacitor on an output side. A boost converter 13, a primary switching circuit 14a including a DC / DC converter using a switching element such as an FET, and a switching control circuit 1
5, 16 and an insulating circuit 17 for insulating the primary circuit and the secondary circuit from each other and transmitting a feedback signal from the secondary circuit side to the primary circuit side. A secondary rectifying / smoothing circuit 21;
An output voltage detection circuit 27 is provided.

In the power supply device 41, when a power switch (not shown) is turned on, the input circuit 12 converts the pulsating current VR generated by full-wave rectification of the input AC VIN input from the AC power supply 2 to the boost converter 13 And the input filter prevents leakage of switching noise to the AC power supply 2 side. Next, the boost converter 13 boosts the pulsating flow VR to generate a boosted DC voltage VUDC stabilized at a predetermined voltage. At this time, the switching control circuit 1
5 controls the frequency or duty ratio of the switching signal SS1 output to the boost converter 13 so that the boosted DC voltage VUDC is stabilized at a predetermined voltage, and the current waveform of the input current IIN flowing from the AC power supply 2 is a sine wave. The switching of the boost converter 13 is controlled so as to approximate The switching control circuit 15 also controls the boost converter 1 according to the voltage change of the boost DC voltage VUDC.
The control response speed at the time of controlling the switching of No. 3 is regulated to a somewhat slow speed (for example, several hundred mS, and the control response frequency is, for example, several Hz). As a result, the switching control of the boost converter 13 is performed without following the ripple voltage superimposed on the boost DC voltage VUDC. As a result, a sufficient power factor improving effect can be obtained. When the control response speed of the switching control circuit 15 is as fast as several hundred μS, the switching control is performed in response to the instantaneous value of the ripple voltage, so that the current waveform of the input current IIN contains many harmonic components. As a result, a sufficient power factor improving effect cannot be obtained.

[0004] Next, the primary switching circuit 14a
In accordance with the switching signal SS2 output from the switching control circuit 16, the boost DC voltage VUDC is switched via the primary winding 11a of the transformer 11. As a result, a voltage is induced in the secondary winding 11b of the transformer 11.
At this time, the secondary rectifying / smoothing circuit 21 rectifies and smoothes the induced voltage to generate an output voltage VO and output it to a load circuit outside the device.

An output voltage detecting circuit 27 detects the output voltage VO and outputs a feedback signal SFS to the insulating circuit 17 based on the value of the output voltage VO. Next, the insulating circuit 17 outputs the feedback signal SFP generated based on the feedback signal SFS to the switching control circuit 16. At this time, the switching control circuit 16 stabilizes the output voltage VO to the rated voltage by controlling the frequency or the duty ratio of the switching signal SS2 based on the feedback signal SFP. In this case, the switching control circuit 16 controls the voltage of the output voltage VO so that the output voltage VO can be stabilized at the rated voltage by following the voltage change of the output voltage VO even in a transient state such as when the power is turned on or when the load suddenly changes. Primary switching circuit 14 according to the change
The control response speed at the time of controlling the switching of a is specified to be a relatively high speed (for example, several hundred μS, and the control response frequency is, for example, several KHz). Therefore, the output voltage VO is stabilized at the rated voltage while the superimposed ripple component is compressed. As described above, according to this power supply device 41, the power factor can be improved by controlling both the switching operations of boost converter 13 and primary switching circuit 14a, and output voltage V can be maintained even in a transient state.
O can be stabilized.

However, in this power supply device 41, boost converter 13 and primary switching circuit 14a are connected to switching control circuit 15 and switching control circuit 16
However, since each of them is controlled, not only the circuit configuration becomes complicated, but also the increase in the number of components causes an increase in manufacturing cost and an increase in the size of the apparatus.
In addition, since the boost converter 13 and the primary switching circuit 14a perform switching independently, there is a problem that mutual interference may be caused by the switching frequency. Furthermore, even if both the boost converter 13 and the primary switching circuit 14a can be operated with a high conversion efficiency of, for example, 90%, the conversion efficiency of both as a whole is reduced to 81%. There is also a problem that it causes a decrease in For this reason, power supply devices 51 and 61 shown in FIGS. 5 and 6, respectively, have been conventionally used. In this specification, the same components will be denoted by the same reference numerals, without redundant description.

As shown in FIG. 5, the power supply device 51 is provided with a primary switching circuit 14b which is a step-down converter for performing switching by a current resonance circuit method, for example, instead of the primary switching circuit 14a in the power supply device 41. . In the power supply device 51, the primary switching circuit 14b switches the boosted DC voltage VUDC generated by the boost converter 13 with an FET or the like, thereby generating an output voltage VO proportional to the boosted DC voltage VUDC at a predetermined ratio. I do. In this case, in the current resonance circuit method, it is difficult in principle to perform PWM control for changing the duty ratio. Therefore, the switching control circuit 15 uses the feedback signal SFP input through the output voltage detection circuit 27 and the insulation circuit 17 to control the duty ratio. By controlling the frequency or the duty ratio of the switching signal SS1, the voltage value of the boost DC voltage VUDC generated by the boost converter 13 is controlled, thereby stabilizing the output voltage VO.

As described above, according to the power supply device 51,
Since the primary switching circuit 14b performs switching by the current resonance circuit method, the switching noise is reduced. Therefore, there is an advantage that a built-in input filter in the input circuit 12 can be easily configured. In addition, since the switching control circuit 15 only needs to perform switching control on the boost converter 13, the configuration can be simplified, so that the manufacturing cost of the device can be reduced and the device can be downsized. In addition, since the current resonance circuit method generally has high efficiency, the conversion efficiency of the entire device can be improved as compared with the power supply device 41.

On the other hand, the power supply device 61 shown in FIG. 6 is configured in a one-converter system, and is configured without employing the boost converter 13 and the switching control circuit 15 in the power supply device 41. Further, in the power supply device 61, in order to improve the power factor, the input circuit 12 is configured without using a smoothing capacitor, unlike a capacitor input system in which a smoothing capacitor is provided on the output side. . Therefore, the primary switching circuit 14b
Causes a voltage to be induced in the secondary winding 11b of the transformer 11 by directly switching the pulsating flow VR.

According to the power supply device 61, since it is a one-converter system, mutual interference due to the switching frequency can be prevented, and since it can be simply configured, the manufacturing cost of the device can be reduced, and the device can be downsized. The conversion efficiency of the whole device can be improved.

[0011]

However, the conventional power supply units 51 and 61 have the following problems. That is, in the power supply device 51, the boosting converter 13 is controlled by the switching control circuit 15, thereby stabilizing the output voltage VO. Therefore, FIG.
As shown in (a), when the voltage of the input AC VIN rises sharply, the effective voltage VINrms of the input AC VIN also rises sharply, as shown in FIG. Also, as shown in FIG. 3C, when a connection failure or the like occurs in the load, the load current IO sharply decreases. In these cases, in the power supply device 51, the switching control of the switching control circuit 15 with respect to the voltage change of the output voltage VO is regulated to a control response speed of several hundred milliseconds in order to obtain a power factor improving effect. Therefore, the power supply device 51 cannot instantaneously follow the voltage change of the output voltage VO and stabilize. Therefore, as shown in FIG. An overshoot waveform that greatly exceeds the upper limit voltage VU or an undershoot waveform that greatly lowers the lower limit voltage VL that is the lower limit of the allowable range with respect to the rated voltage Va appears in the output voltage VO. As a result, there is a problem that the load circuit may be damaged.

On the other hand, in the conventional power supply device 61, the pulsating flow VR
In the voltage range where the instantaneous value is large, for example, near the peak voltage, the output voltage VO can be sufficiently stabilized. However, since the input circuit 12 has no smoothing capacitor, the voltage of the input AC VIN decreases. Time (that is, pulsating flow V
In the vicinity of the valley of R), there is insufficient energy.
As a result, the power supply device 61 has a problem that it is difficult to sufficiently stabilize the output voltage VO. In this case, it is possible to employ an energy regeneration system in which energy is stored in a capacitor or the like when the instantaneous value of the input AC VIN is large, and energy is released from the capacitor near the valley of the pulsating flow VR. . However, in such a case, there is a problem that the configuration of the device becomes complicated.

Further, even if the output voltage VO can be stabilized by the energy regeneration method, the following problems occur. That is, the primary switching circuit 14a
Since the control response speed is as fast as several hundred μS, as shown in FIG. 7 (e), when the ripple voltage is superimposed on the output voltage VO, it follows the ripple voltage quickly. As a result, the current waveform of the input current IIN is greatly distorted as shown in FIG. 3F, and as a result, the power factor deteriorates to about 0.85. In this case, it is conceivable to regulate the control response speed of the switching control of the primary switching circuit 14a to a speed as high as tens of milliseconds. However, even in such a case, the power factor is deteriorated to about 0.9 as a result of distortion as shown in FIG. Therefore, the conventional power supply device 61 has a problem that a sufficient power factor improvement effect cannot be expected.

The present invention has been made to solve such a problem, and has been made to reduce the size and cost and increase the efficiency.
Moreover, it is an object of the present invention to provide a switching power supply device that can guarantee a reliable stabilizing operation and a sufficient power factor improving effect.

[0015]

According to a first aspect of the present invention, there is provided a switching power supply unit for generating an output voltage by switching an input voltage, and detecting a voltage of the output voltage. in the switching power supply and a feedback control unit for controlling the switching of the switching unit on the basis of the detected voltage with the switching unit, boosting power factor correction
The output voltage of the converter and the boost converter for power factor improvement
2 converter including a step-down converter for stepping down to a predetermined voltage
It consists of over capacitor circuit scheme, the feedback control unit, out
Output voltage to stabilize the output voltage to the rated voltage.
Output voltage detection circuit that detects at a slow detection response speed,
Control of a voltage higher than the pressure and lower than the upper limit voltage of the device
When the output voltage reaches the voltage,
Upper limit voltage for detecting output voltage with fast detection response speed
The detection circuit and the lower limit voltage of the equipment lower than the rated voltage
The output voltage reaches the lower limit control voltage
The output voltage is detected at a faster detection response speed than the output voltage detection circuit.
A detection device having at least a lower limit voltage detection circuit for detecting voltage
Output section and the detection voltage detected by the detection section.
Control the switching of the boost converter for power factor improvement.
Stabilizes the output voltage to the rated voltage and
Limit within the voltage range from the control voltage to the lower limit control voltage
And a switching control circuit .

According to a second aspect of the present invention, there is provided a switching power supply.
2. The switching power supply according to claim 1, wherein an upper limit system is set.
Your voltage and a lower limit control voltage is characterized by being relatively variably defined with respect to the rated voltage.

According to a third aspect of the present invention, there is provided a switching power supply.
3. The switching power supply according to claim 1, wherein each voltage detection circuit has a variable detection response speed.
Characterized in that it is configured.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of a switching power supply (hereinafter referred to as "power supply") according to the present invention will be described below with reference to the accompanying drawings. Note that the same components as those of the conventional power supply devices 41, 51, 61 are denoted by the same reference numerals, and redundant description will be omitted.

As shown in FIG. 1, the power supply device 1 is composed of, for example, a forward type DC / DC converter, and a primary circuit 11a side of a transformer 11 has an input circuit 12, a primary switching circuit 14a , A switching control circuit 16 and an insulating circuit 17,
1, a secondary rectifying / smoothing circuit 21, resistors 22 to 25 for voltage detection, an upper limit voltage detection circuit 26, an output voltage detection circuit 27, and a lower limit voltage detection circuit 2
8 is provided. The voltage detection circuits 26 to 28 constitute a detection unit according to the present invention, and the switching control circuit 16, the insulation circuit 17, the resistors 22 to 25, and the voltage detection circuits 26 to 28 constitute the feedback control unit 2.
9a is formed.

In the above configuration, the resistors 22 to 25 are
This is for dividing the output voltage VO. Each of the resistance values is a predetermined ratio (for example, 1) of the divided voltage V2 at the connection point of the resistors 22 and 23 to the divided voltage V1 at the connection point of the resistors 23 and 24. .1), and the divided voltage V3 at the connection point between the resistors 24 and 25 with respect to the divided voltage V1 is predetermined so as to have a predetermined ratio (for example, 0.9 times).

On the other hand, each of the voltage detection circuits 26 to 28 is constituted by, for example, an operational amplifier circuit. Each operational amplifier circuit receives a divided voltage at one input portion of the operational amplifier and a predetermined voltage. The feedback system formed by the time constant circuit is connected between the output section and the other input section. In this case, the time constant in the feedback system of each voltage detection circuit can be defined to a fixed time by using a capacitive element such as a capacitor and a resistor. In addition, by using a varicap diode, for example, as a capacitive element as a feedback system, the time constant can be easily varied from the outside. Hereinafter, an example in which the time constant is fixed will be described.

The time constant in the feedback system of the output voltage detection circuit 27, that is, the detection response speed of the output voltage detection circuit 27 is
For example, it is defined as 200 mS (5 Hz as a detection response frequency). Therefore, the output voltage detection circuit 27
Does not respond to the ripple voltage superimposed on the pulsating current VR obtained by full-wave rectification of the commercial alternating current, but only responds to the gradual fluctuation of the output voltage VO. Feedback signal SFS generated by amplification
Outputs 1. The time constant in the feedback system of the upper limit voltage detection circuit 26, that is, the detection response speed of the upper limit voltage detection circuit 26 is, for example, 1 mS (the detection response frequency is 1 KH
z). Therefore, the upper limit voltage detection circuit 26 immediately responds to a ripple voltage superimposed on the output voltage VO or a sudden change in the output voltage VO.
A feedback signal SFS2 generated by amplifying the divided voltage V2 is output. Further, the time constant in the feedback system of the lower-limit voltage detection circuit 28, that is, the detection response speed of the lower-limit voltage detection circuit 28 is specified to, for example, 1 mS (the detection response frequency is 1 KHz). Therefore,
The lower limit voltage detection circuit 28 also responds immediately to the ripple voltage and the rapid fluctuation of the output voltage VO, and in that case, outputs a feedback signal SFS3 generated by amplifying the divided voltage V3. Note that the upper limit voltage detection circuit 2
6 and the lower limit voltage detection circuit 28 may have different detection response speeds.

The insulating circuit 17 is composed of, for example, a photocoupler or a signal transmitting transformer. The insulating circuit 17 converts the feedback signals SFS1 to SFS3 into new feedback signals while maintaining the secondary circuit and the primary circuit insulated from each other. S
The signal is converted to FP and output to the switching control circuit 16.

In this power supply device 1, when a power switch (not shown) is turned on, the input circuit 12 performs full-wave rectification on the input AC VIN output from the AC power supply 2 shown in FIG. The pulsating flow VR shown in FIG. 3B is generated, and the pulsating flow VR is output to the primary switching circuit 14a. At the same time, the input circuit 12
Prevent leakage of switching noise to the side. Then
The primary switching circuit 14a switches the pulsating flow VR via the primary winding 11a of the transformer 11 according to the switching signal SS2 output from the switching control circuit 16. Thereby, the secondary winding 11b of the transformer 11
Voltage is induced at At this time, the secondary rectification smoothing circuit 21
Rectifies and smoothes the induced voltage to produce an output voltage VO
Is generated and output to a load circuit outside the device.

On the other hand, the output voltage detecting circuit 27 generates a feedback signal S generated based on the input divided voltage V1.
FS1 is output to the insulation circuit 17. Next, the insulating circuit 17
Outputs the feedback signal SFP generated based on the feedback signal SFS1 to the switching control circuit 16. At this time, the switching control circuit 16 controls the frequency or duty ratio of the switching signal SS2 in real time based on the feedback signal SFP, thereby stabilizing the output voltage VO to the rated voltage.
In this case, the output voltage VO is, for example, ± 1 with respect to the rated voltage.
When the output voltage is within the range of about 0%, the detection response speed of the output voltage detection circuit 27 is set to a low speed, and as a result, it does not immediately respond to the ripple voltage superimposed on the output voltage VO.
As shown in FIG. 3C, the current waveform of the input current IIN input to the input circuit 12 is kept substantially sinusoidal. Therefore, since the power factor is also maintained at approximately the value 1, a very good power factor improving effect can be obtained.

On the other hand, when the effective voltage VINrms of the input AC VIN sharply rises as shown in FIG. 3D, or when the load current IO suddenly decreases due to a sudden load change as shown in FIG. And the voltage of the output voltage VO also tends to rise sharply. At this time, when the output voltage VO reaches the upper limit control voltage VUC, the upper limit voltage detection circuit 26 insulates the feedback signal SFS2 generated based on the input divided voltage V2 as shown in FIG. Output to the circuit 17 instantaneously. Next, the insulating circuit 17 outputs the feedback signal S generated based on the feedback signal SFS2.
FP is output to the switching control circuit 16. At this time,
The switching control circuit 16 receives the feedback signal SFP.
To control the switching operation of the primary switching circuit 14a by immediately controlling the frequency or duty ratio of the switching signal SS2 in real time. In this case, since the detection response speed of the upper limit voltage detection circuit 26 is set at a high speed, the output voltage VO overshoots greatly exceeding the upper limit voltage VU of the device as shown in FIG. Without being limited to the upper limit control voltage VUC.

Conversely, when the voltage of the input AC VIN drops sharply, or when the load current IO suddenly increases due to a sudden change in load, the voltage of the output voltage VO also tends to drop sharply. At this time, as shown in FIG.
Reaches the lower limit control voltage VLC, the lower limit voltage detection circuit 28 instantaneously outputs the feedback signal SFS3 generated based on the input divided voltage V3 to the insulating circuit 17. Next, the insulating circuit 17 outputs the feedback signal SFS.
3 is output to the switching control circuit 16. Also at this time, the switching control circuit 16 immediately controls the frequency or duty ratio of the switching signal SS2 in real time based on the feedback signal SFP. Also in this case, since the detection response speed of the lower limit voltage detection circuit 28 is set to a high speed, the output voltage VO becomes as shown in FIG.
It is limited to the lower control voltage VLC without causing an undershoot that drops significantly below the lower voltage limit VL of the device.

As described above, according to the power supply device 1, 1
By using the converter circuit method, the size, price and efficiency of the device can be reduced, and the control response speed for the output voltage VO in normal conditions is set to a low speed, so that the input current can be reduced. As a result of maintaining the current waveform of IIN as a sine wave, a sufficient power factor improving effect can be obtained. Further, according to the power supply device 1, when the output voltage VO is going to be out of the voltage range from the lower limit control voltage VLC to the upper limit control voltage VUC, the upper limit voltage detection circuit 26 or the lower limit voltage detection circuit 28 By instantaneously outputting the signal SFS2 or the feedback signal SFS3, the output voltage VO can be stabilized within the voltage range from the upper limit control voltage VUC to the lower limit control voltage VLC.

Next, a power supply device 31 according to another embodiment will be described with reference to FIG. Since the basic operation is almost the same as that of the power supply device 1, different configurations and operations will be mainly described.

As shown in the figure, the power supply device 31 is different from the power supply device 1 in that a primary switching circuit 14b, which is a step-down converter, is provided in place of the primary switching circuit 14a. The switching control circuit 15 is configured to control the switching operation of the boost converter 13 by inputting the feedback signal SFP. The switching control circuit 1
5, the insulating circuit 17, the resistors 22 to 25, and the voltage detecting circuits 26 to 28 form a feedback control unit 29b.

In this power supply device 31, when the voltage of the input AC VIN is going to rise or fall suddenly, the upper limit voltage detecting circuit 26 (or the lower limit voltage detecting circuit 28)
Converts the feedback signal SFS2 (or SFS3) generated based on the divided voltage V2 (or V3) into an isolated circuit 1.
7 instantaneously. Next, the insulating circuit 17 outputs the feedback signal SFP to the switching control circuit 15. At this time, the switching control circuit 15 immediately controls the frequency or the duty ratio of the switching signal SS1 in real time based on the feedback signal SFP. As a result, the switching operation of boost converter 13 is controlled, and as a result, output voltage VO rises to upper limit control voltage VUC.
(Or lower limit control voltage VLC). Also in this case, the upper limit voltage detection circuit 26 (or the lower limit voltage detection circuit 2)
Since the detection response speed of 8) is specified to be fast,
The output voltage VO can be adjusted from the upper limit control voltage VUC to the lower limit control voltage VLC without causing an overshoot that greatly exceeds the upper limit voltage VU of the device or an undershoot that significantly lowers the lower limit voltage VL of the device. It is stabilized within the voltage range.

It should be noted that the present invention is not limited to the configuration shown in the above embodiment, but can be appropriately changed. For example, in the embodiment of the present invention, the power supply devices 1 and 31 in which the output voltage VO is fixed in advance to a predetermined voltage width with respect to the rated voltage of the device have been described as an example. The present invention can also be applied to a power supply device of a variable output voltage type so as to be able to execute a constant current operation and an output constant current operation. In this case, when the ratio of the upper limit control voltage VUC and the lower limit control voltage VLC to the rated voltage is maintained the same as that of the power supply device 1, the resistors 22 to 25 can be configured with the same resistance value without changing the resistance value. .
Conversely, when changing the ratio of the upper limit control voltage VUC and the lower limit control voltage VLC to the rated voltage, the resistances 22 to 25
May be appropriately changed. Further, in the embodiment of the present invention, the upper limit control voltage VUC and the lower limit control voltage VLC
Is configured to have a voltage value of a predetermined ratio with respect to the rated voltage. However, it is also possible to add and subtract a predetermined voltage value to and from the rated voltage to define the upper limit control voltage VUC and the lower limit control voltage VLC, respectively. . Also, four or more voltage detection circuits can be provided, and the detection response speed can be specified for each voltage detection circuit.

Further, the control response speed in the present invention is not limited to the speed shown in the embodiment of the present invention, and can be appropriately changed. Furthermore, the control response speed depends on the power supply device 1,
The example in which the control is performed in two steps at 31 has been described. However, the present invention is not limited to this. The control may be performed in multiple steps or in a linear and stepless manner in accordance with the voltage value of the output voltage VO. In this case, it is preferable to control the switching of the primary switching circuit 14a (or the boost converter 13) at a higher control response speed as the voltage difference between the output voltage VO and the rated voltage of the device is larger. In the case of such a configuration, the output voltage VO is set as the fastest control response speed when the voltage difference is maximum.
If the speed is specified to be able to sufficiently follow the steep change of the ripple voltage and the frequency of the ripple voltage, and the slowest control response speed when it is almost stabilized at the rated voltage, the speed that does not follow the frequency of the ripple voltage is specified. Good.

Further, in the embodiment of the present invention, the detailed description of the specific configuration in each circuit is omitted, but it is needless to say that various circuit configurations that can be normally designed by those skilled in the art can be adopted. It is. Further, in the above-described embodiment, the configuration of the forward type switching power supply has been described. However, the present invention is not limited to this, and the present invention can be applied to a flyback type switching power supply, and the switching in the boost converter 13 and the primary switching circuits 14a and 14b. FET as element
Various switching elements such as transistors and transistors can also be employed.

[0035]

As described above, according to the switching power supply device of the first aspect, the output voltage falls below the upper limit control voltage.
When trying to deviate from the voltage range up to the
Unit detects the output voltage at a high detection speed and feeds it.
The back control unit boosts the power factor based on the detected voltage.
By controlling the switching of the converter, the output
Sufficiently follows sharp voltage changes and ripple voltage frequencies
Control the output voltage from the upper control voltage to the lower control voltage.
It can be limited to a voltage range up to the voltage. Also,
When the output voltage is within the specified voltage range with respect to the rated voltage
Means that the feedback control unit
Boost converter for power factor improvement based on detected voltage
By controlling the switching of the
Thus, a sufficient power factor improving effect can be obtained. Accordingly
In general, conflicting power factor improvement effects and reliable stability
Switching power supply that has the advantages of both
Can be offered. In addition, the switching unit
Two converter times, a boost converter and a buck converter
With the circuit configuration, when the input voltage drops,
Output voltage can be reliably stabilized at the rated voltage.
You.

Further, the switching power supply apparatus according to claim 2, by defining relatively variably with respect to the rated voltage of the device the upper control voltage and a lower limit control voltage, optionally a rated voltage changes In this case, a reliable stabilizing operation can be ensured.

According to the switching power supply device of the third aspect , the detection response speed of each voltage detection circuit can be varied.
With this configuration , the switching power supply device can be configured to meet the purpose of improving the power factor and ensuring stable operation.

[Brief description of the drawings]

FIG. 1 is a block diagram of a power supply device 1 according to an embodiment of the present invention.

FIG. 2 is a block diagram of a power supply device 31 according to another embodiment of the present invention.

3A and 3B are signal waveform diagrams for explaining the operation of the power supply device 1 according to the embodiment of the present invention, wherein FIG. 3A is a voltage waveform diagram of an input AC VIN, and FIG. 3B is a voltage waveform of a pulsating current VR. Waveform diagram,
(C) is a current waveform diagram of the input current IIN, (d) is a voltage waveform diagram of the effective voltage VINrms of the input AC VIN, (e) is a current waveform diagram of the load current IO, and (f) is a voltage waveform of the output voltage VO. FIG.

FIG. 4 is a block diagram of a conventional power supply device 41.

FIG. 5 is a block diagram of a conventional power supply device 51.

FIG. 6 is a block diagram of a conventional power supply device 61.

7A and 7B are signal waveform diagrams for explaining the operation of the conventional power supply devices 51 and 61, wherein FIG. 7A is a voltage waveform diagram of an input AC VIN, and FIG. 7B is a voltage waveform of an effective voltage VINrms of the input AC VIN. Waveform diagram, (c) is a current waveform diagram of the load current IO, (d)
Is a voltage waveform diagram of the output voltage VO, (e) is a voltage waveform diagram of the output voltage VO, (f) is a current waveform diagram of the input current IIN,
(G) is another current waveform diagram of the input current IIN.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Power supply device 13 Boost converter 14a Primary switching circuit 14b Primary switching circuit 15 Switching control circuit 16 Switching control circuit 17 Insulation circuit 22-25 Resistance 26 Upper limit voltage detection circuit 27 Output voltage detection circuit 28 Lower limit voltage detection circuit 29a Feedback control unit 29b Feedback Control unit 31 Power supply unit

Claims (3)

(57) [Claims] A switching unit for generating an output voltage by switching an input voltage; detecting a voltage of the output voltage ; and controlling switching of the switching unit based on the detected voltage. In a switching power supply device comprising a feedback control unit, the switching unit includes a power factor improving boost converter,
Set the output voltage of the power factor improving boost converter to a predetermined voltage.
Two-converter circuit including a step-down converter for stepping down
It consists of an expression, the feedback control unit, rated voltage the output voltage
Slow detection response of the output voltage to stabilize
Output voltage detection circuit that detects by speed, more than the rated voltage
Upper limit control voltage that is higher than the upper limit voltage of the device
When the output voltage reaches the output voltage detection circuit.
Detects the output voltage with a faster detection response speed
The upper limit voltage detection circuit and the lower limit
Output to a lower control voltage higher than the lower limit voltage of the device.
Faster than the output voltage detection circuit when the output voltage reaches
Lower limit voltage for detecting the output voltage at the detection response speed
A detection unit including at least a detection circuit;
The power factor improving boost based on the detected voltage
By controlling the switching of the converter,
The output voltage is stabilized at the rated voltage and the upper limit
Within the voltage range from the control voltage to the lower limit control voltage.
And a switching control circuit . Wherein said upper control voltage and the lower limit control electrostatic <br/> pressure, switching power supply of claim 1 wherein said is relatively variably defined with respect to the rated voltage apparatus. 3. The voltage detection circuit according to claim 2, wherein
3. The switching power supply according to claim 1, wherein the response speed is variable .