JP2000166233A - Power supply and method for improving power supply efficiency - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve power supply efficiency in any operating condition to meet requirements for energy saving. SOLUTION: The power supply includes the driving frequency of a switching element 8 in control parameters in PWM control and control pulse width in control parameters in PFM control so that input power is reduced. The driving frequency of the element 8 is slightly varied in PWM control and the control pulse width is slightly varied in PFM control so that the power supply efficiency is improved.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a power supply device and a power supply efficiency improving method.

[0002]

2. Description of the Related Art A circuit configuration of a conventional power supply device, for example, a switching power supply will be described with reference to FIG.
A converter unit 6 for converting an input voltage from the input rectifying / smoothing unit 4 to a predetermined voltage, a switching element 8 which performs a switching operation at a fixed drive frequency f ₀ or a fixed control pulse width Toff ₀ , and rectifies and smoothes the output of the converter unit 6. It comprises an output rectifying / smoothing unit 10, an output voltage detecting unit 12 for detecting an output voltage, and a control block 14. The control block 14 includes the control unit 14a and the comparison feedback unit 1
4b, the comparison feedback section 14b compares the output voltage detection output of the output voltage detection section 12 with a reference value and feeds back the comparison result to the control section 14a, and the control section 14a performs switching in response to the comparison result. The element 8 is ON-OFF controlled to stabilize the output voltage to a constant value. Since the operation of such a switching power supply is well known, a detailed description of the operation is omitted.

There are a PWM control method and a PFM control method as a driving method of the switching element 8 in the control block 14. In the PWM control method, the drive frequency of the switching element 8 is fixed, and the control pulse width (ON pulse width or ON duty or ON period) is used as a control parameter.
FM control method is the control pulse width (OFF pulse width or OFF period, or ON pulse width or ON period)
Is fixed, and the output voltage is stabilized at a constant value using the drive frequency of the switching element 8 as a control parameter.

[0004]

The following problems are pointed out in the conventional switching power supply having the above configuration.

In the case of the PWM control method, the output voltage can be stably controlled to a constant value because the drive frequency is fixed and only the control pulse width is changed, but the power supply efficiency (= output power / input power) ) Cannot be controlled to achieve higher efficiency, so that there is a problem that the internal loss is large and thus the ineffective power is increased.

[0006] In the case of the PFM control method, since the control pulse width is fixed and only the drive frequency is changed, the PWM is controlled.
Similar to the control method, there is a problem that the internal loss is large and thus the ineffective power increases.

In the recent PFM control method, in order to prevent the oscillation frequency from becoming high and the switching loss from increasing in proportion to the frequency when the input voltage is high and the load is light (output power is small), the OFF period is set. In order to improve the power supply efficiency at the time of light load, it has been proposed that the control is performed so that the oscillation frequency does not become shorter than a predetermined period of time so that the oscillation frequency does not increase at the time of light load. However, even with such improvement in power efficiency at light load,
In that state, the power supply efficiency could not be improved higher.

As described above, the conventional power supply device does not satisfy the demand for energy saving.

In the present invention, in order to satisfy the demand for energy saving, it is a common feature that the power supply efficiency can be further improved irrespective of the operation state regardless of the control method. Is a problem to be solved.

[0010]

According to the power supply device of the present invention, there is provided a converting means for converting an input voltage into a predetermined voltage, a switching means for controlling a converting operation of the converting means,
Control means for driving and controlling the switching means by a PWM control method, wherein not only a control pulse width but also a driving frequency is added as a control parameter of the switching means, and the driving frequency is minutely changed with respect to power supply efficiency. ing.

In the power supply device according to the present invention, a converting means for converting an input voltage to a predetermined voltage, a switching means for controlling a converting operation of the converting means, and a control means for controlling the driving of the switching means by a PFM control method In addition to the drive frequency as a control parameter of the switching means, a control pulse width is added, and the control pulse width is minutely changed with respect to power supply efficiency.

[0012]

Embodiments of the present invention will be described below in detail with reference to the drawings. The power supply device of the present invention is not limited to the switching power supply of the type described in the embodiment, but can be applied to all other types of switching power supplies. Further, the present invention is not limited to the switching power supply, and can be applied to other types of power supply devices. In short, the power supply device of the present invention includes all power supply devices having conversion means for converting and controlling an input into a predetermined output, and control means for performing the conversion control in response to a signal related to the output.

In the following, the PWM control method and the PFM
The description will be made separately for the control method.

(PWM Control System) In the present invention, in order to improve the power supply efficiency of the switching power supply of the PWM control system, not only a conventional control pulse width but also a control parameter is used as a control parameter.
In addition, it also has a drive frequency as a control parameter. Hereinafter, the PWM of the present invention will be described with reference to FIGS.
The power efficiency improvement in the control method will be described.

FIG. 1 shows a power efficiency characteristic in which the horizontal axis represents the load factor (percentage of the output current with respect to the rated current) and the vertical axis represents the power efficiency. In FIG. 1, the case where the input AC power is 100 V and the case where the input AC power is 200 V are shown. In each case, the change of the power efficiency with respect to the load factor is different. That is, FIG. 1 shows that the smaller the input voltage, the higher the power supply efficiency.

FIG. 2 shows a power efficiency characteristic in which the horizontal axis represents the driving frequency of the switching element and the vertical axis represents the power efficiency. In addition, as shown in FIG.
At 0% and 100%, the driving frequency at which the maximum power supply efficiency can be achieved changes with the load factor. That is, FIG.
In this case, as the load factor increases, the power efficiency increases at a lower driving frequency.

Normally, the driving frequency is fixed at a frequency that provides optimum power supply efficiency when the load factor is 100%. Therefore, when the switching power supply is used for a load having a load factor of 100%, optimum power supply efficiency can be obtained.
However, since the switching power supply is generally selected based on the peak output capacity that can be considered for the user's application, the switching power supply has a load factor of 50% in actual use.
It is often working at about. Then, load factor 5
In the case of 0%, the driving frequency of the switching element 8 deviates from the driving frequency at which the optimum power supply efficiency can be realized, resulting in a loss of power energy.

This will be described with reference to FIG. 3 (driving frequency on the horizontal axis and power supply efficiency on the vertical axis). Figure 3 shows a load factor of 70%
Is an example. First, consider the case where the input current of the switching power supply changes greatly under the same load condition. At this time, since the output voltage and the output current are both constant because the load is the same condition, the output power is not changed and the power supply efficiency (output power /
The input power) parameter is the input current. Therefore, when the input current increases, the input power increases and the power efficiency with respect to the output power decreases. On the contrary, when the input current decreases, the power efficiency increases. here,
In order to calculate the power supply efficiency, the input current is subjected to an averaging process or an integration process (hereinafter simply referred to as a process) for an arbitrary fixed time, and the processing result is processed (to correspond to the input power as described above). Say

Then, it is assumed that the initial drive frequency f ₀ for the switching element is lower than the drive frequency fopt at which the optimum power supply efficiency is obtained. At this time, the processing value (first processing value) at the initial drive frequency is stored. Then, the driving frequency is f ₁ in which the oscillation light minute frequency to the higher of the initial drive frequency to obtain the process value of the time (the second process value). Then, the first and second processing values are compared. As a result of this comparison, the second processing value
When the processing value is smaller, the second processing value requires less input power than the first processing value to obtain the same output power. Therefore, it is better to shift the frequency by a small value than the initial driving frequency. The power supply efficiency is high. Similarly, the f ₂ which was further shifted higher minute value the drive frequency to obtain the process value of this time (third process value). Then, the two second and third processing values are compared. As a result of this comparison, when the third processing value is smaller than the second processing value, the power efficiency is higher when the frequency is further shifted by a small value. In addition, as a result of shifting the frequency, a decrease in the power supply efficiency means that the frequency is shifted too much, so that the frequency is slightly shifted to a lower one. By performing a control routine that repeats the above, a drive frequency fopt that ultimately maximizes the power supply efficiency can be obtained.

In this case, the control routine is not performed in a relatively long time unit, for example, by fixing the load factor to 70%. For example, the load factor is shown in FIG. 70) in a short time unit as shown in
% To, for example, 30%. In such a case, a sudden change in the load factor is detected, and the same control routine as described above is performed.

That is, a process in which the input current process is performed in a long time unit (for convenience of explanation, referred to as a macro process)
And processing performed in short time units (called micro processing for the sake of explanation), and while the power efficiency in a long time unit is increased by macro processing on average, the power efficiency is increased in that long time unit. Although the power supply efficiency is high on average, the power supply efficiency is prevented from lowering in a short time unit due to a sudden change in load, and the high power efficiency is obtained in a short time unit by micro processing.

Next, the PWM by the above-described power supply efficiency improvement
FIG. 5 shows an embodiment of a control type switching power supply.
This will be described with reference to FIG.

FIG. 5 shows a PWM according to an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram of a control switching power supply. Referring to FIG. 5, the switching power supply according to the embodiment includes an input rectifying / smoothing unit 4, a converter unit 6, a switching element 8, an output rectifying / smoothing unit 10, an output voltage detecting unit 12, and a control block 1.
4, an input current detection unit 16 and an output current detection unit 18.

In the embodiment, the control block 14 includes an input current processing section 14c, a drive frequency variable section 14d, and a control section 14a and a comparison feedback section 14b.
It has a load fluctuation detecting unit 14e and a processing value memory 14f.

The control block 14 will be described.

The input current processing unit 14c processes the output of the input current detection unit 18 for a predetermined time unit (ΔT). Here, the predetermined time unit is replaced by a long time unit (ΔT).
= A macro processor 14c ₁ serves for processing the input current (macro process) as [Delta] T _L), also processes the input current (micro processing) the predetermined time unit as a short time units ([Delta] T = [Delta] T _S) Micro-processing unit 1 that performs functions
4c ₂ .

The input current processing unit 14c also processes the input current processing value (macro processing value) macro-processed by the macro processing unit 14c ₁ and the input current processing value (micro processing value) micro-processed by the micro processing unit 14c _2. Output.

The input current unit 14c further also when the load change detection unit 14e without trigger signal input and outputs the macro process value of the macro unit 14c _1, the micro processor unit 14c when there is an input of the trigger signal Output the micro-processed value of ₂ .

The drive frequency variable section 14d performs a predetermined operation when a macro processing value is input from the input current processing section 14c, and outputs a drive frequency variable signal corresponding to the calculation result when a micro processing value is input. Performs a predetermined operation and outputs a drive frequency variable signal corresponding to the operation result.

The processing value memory 14f can store and read macro processing values and micro processing values.

The load fluctuation detecting section 14e detects a load fluctuation based on the detection output of the output current detecting section 16, and does not output a trigger signal when there is no load fluctuation or when the load fluctuation is below a predetermined level. When the load fluctuates, a trigger signal is output.

The load fluctuation detecting section 14e will be described with reference to FIGS.

The change in the output current Io detected by the output current detector 16 corresponds to the change in the voltage across the resistor 16a as shown in FIG. The voltage between both ends of the resistor 16a is equal to the resistor R1 and the capacitor C via the diode D1, respectively.
1 and an integrating circuit including a resistor R2 and a capacitor C2 via a diode D2. Since the relationship of the time constant consisting of the capacitance of the capacitor C1 and the resistor R1 <the time constant consisting of the capacitor C2 and the resistor R2 is set, the potential at the point A, which is the integrated output, is shown in FIG. The point potential changes as shown in FIG. The comparing section CP compares the potential at the point A with the potential at the point B and outputs a comparison result shown in FIG. The output of the comparison unit CP is differentiated by a differentiation circuit including a capacitor C3 and a resistor R3. As a result, the differential output shown in FIG. 7E is obtained at point C which is the output unit of the comparison unit CP. Both differential outputs are rectified by the full-wave rectifier circuit RD, and as a result, a rectified output shown in FIG. Both rectified outputs are input to the input current processing unit 14b as a trigger signal of the load fluctuation detection unit 14e. The reason why there are two trigger signals is that the load fluctuation corresponds to the timing T1 at which the load changes from a heavy load to a light load and the timing T2 at which the load changes from a light load to a heavy load in FIG.

Returning to FIG. 5, the control section 14a varies the drive frequency in response to the drive frequency variable signal from the drive frequency variable section 14d.

Hereinafter, the control operation of the control block 14 will be described with reference to the control flow of FIG.

At the fixed driving frequency f ₀ during operation, the signal of the input current detection unit 18 is processed by the input current processing unit 14c for a fixed time ΔT, and the processing value Iin (ave) ₀ is stored in the processing value memory 14f. (N1).

The driving frequency variable unit 14d changes the driving frequency by a small Δf from the fixed driving frequency f ₀ to f ₀ + Δf (≡f ₁ ) (n2), and the control unit 14a
Controls and drives the switching element 8.

In the above driving state, the signal of the input current detector 18 is processed again by the input current processor 14c for a predetermined time ΔT. This processing value is defined as Iin (ave) ₁ .

Here, Iin (ave) ₀ and Iin
(Ave) Compare the size with ₁ (n3).

When Iin (ave) ₁ > Iin (ave) ₀ , it means that the drive frequency f ₀ has higher power supply efficiency. In this case, since it is considered that the direction in which the drive frequency was changed was opposite, the drive frequency was changed to f ₂ = f ₀ −Δ
f (n4).

Also, Iin (ave) ₀ > Iin (av
e) In the case of ₁ , it means that the drive frequency f ₁ is more efficient in power supply, so that the current drive frequency is maintained and f ₂ ≡
f ₁ (= f ₀ + Δf) (n5). Then, a process for a predetermined time ΔT is performed (n6), and the process returns to n1.

After one cycle has been completed as described above and the finally determined f2 is replaced with f0, the above-mentioned cycle is repeated again to maximize the power supply efficiency.

Assuming that the fixed time ΔT for performing the processing is a fixed time ΔT _L for the macro processing and a fixed time ΔT _S for the micro processing, if there is no trigger signal input from the load fluctuation detecting unit 14e, the fixed time ΔT during the [Delta] T _L, the input current unit 14b and macro processing in the macro processor 14c _1, to improve the power efficiency in the case where the state is gradually displaced slowly as the ambient temperature changes, load change detector If there is a trigger signal input from 14e, a certain time ΔT _S
During, improving the power efficiency in the case where the state can change in a short time as a micro-processor in the micro processor unit 14c ₂ load change.

In the above description, once the switching power supply is installed, the input voltage is substantially constant and does not fluctuate, and the input power is simply detected by the average value or the integral value of the input current. are doing. The processing of the input current, the control of the variable drive frequency, and the like may be performed by software using a microcomputer, or may be performed using analog circuit components.

(PFM Control Method) The improvement of the power efficiency in the switching power supply of the PFM control method of the present invention will be described. The control parameter in the switching power supply of the present invention has a control pulse width (ON pulse width, ON period, or ON duty, or OFF pulse width, OFF period, or OFF duty) in addition to the driving frequency of the switching element.

In a self-excited RCC (ringing choke converter) system, which is a typical example of the PFM control system, focusing on an oscillation frequency (drive frequency) for driving a switching element, a high input is lighter than a low input, and a lighter load than a heavy load. Each of the loads has a higher drive frequency. When the driving frequency is increased, there is a problem that the power loss during the drive control of the switching element is proportionally increased and the power supply efficiency is deteriorated. In order to solve such a problem, recently, the minimum value of the control pulse width is determined so that the driving frequency does not become higher than a certain level, and switching is performed such that the control pulse width is not reduced below the minimum value. Power supplies have also been proposed. According to this proposal, the control pulse width is clamped to the minimum value at the time of light load, and a discontinuous mode exists in which there is a period during which no current flows in the primary winding and the secondary winding of the switching transformer. The frequency does not rise excessively, and the power supply efficiency at light load is improved. It is known that the switching transformer operates discontinuously at a light load, thereby improving power supply efficiency at a light load.

In the present invention, the control pulse width is basically determined in advance, and the basic operation is to use the drive frequency as a control parameter to operate the switching element discontinuously at light load, and to fine-tune the switching element by controlling the control pulse width to the control parameter. In addition to this, the power supply efficiency is to be further improved.

Hereinafter, an improvement in power supply efficiency in the PFM control system of the present invention will be described with reference to FIGS.

FIG. 9 shows the power efficiency characteristics expressed by the horizontal axis representing the load factor and the vertical axis representing the power efficiency. In FIG. 9, the case where the input voltage by the input AC power is 100 V and the case where the input voltage is 200 V are shown.
In each case of V, the change of the power efficiency with respect to the load factor is different, and the lower the input voltage, the higher the power efficiency.

FIG. 10 shows a power efficiency characteristic in which the horizontal axis represents the control pulse width of the switching element (OFF period: Toff in this example) and the vertical axis represents the power efficiency. Further, as shown in FIG. 10, the change of the power efficiency at the load ratio of 50% and 100% at the input voltages of 100 V and 200 V, respectively, is shown. According to this, Toff which can realize the highest power supply efficiency differs depending on the load factor and the input voltage, and Toff which realizes the peak of the power supply efficiency changes depending on the load factor even when the input voltage is fixed. Normally, the switching power supply determines Toff such that the input voltage is minimum and the design is optimal at a load factor of 100%. According to this, the power supply efficiency is good at a low input voltage and a load factor of 100%, but the power supply efficiency deteriorates as the input voltage increases and the load decreases. In addition, when selecting a switching power supply, the switching power supply is selected based on a peak output capacity that can be considered by a user's application. Therefore, in a normal operation state, the switching power supply often operates at a load factor of about 50%. Considering such a state, it is impossible to operate at the highest power supply efficiency.

Therefore, in the present invention, the basic operation is to control the drive frequency as a control parameter and determine the minimum value of the control pulse width of the switching element so that the switching transformer is in the discontinuous mode at light load. Fine-tuning the control pulse width (Tof
f) as a control parameter.

That is, FIG. 11 (the horizontal axis indicates the control pulse width To
ff, the vertical axis indicates power supply efficiency), and it is assumed that the initial control pulse width for the switching element is shorter than the control pulse width Toffopt at which the optimum power supply efficiency is obtained. At this time, the processing value (first processing value) at the initial control pulse width is determined. Next, the control pulse width is shifted by a small value ΔT toward the longer side than the initial control pulse width, and the processing value (second processing value) at this time is obtained. Then, the first and second processing values are compared. As a result of the comparison, when the second processing value is smaller than the first processing value, the control is performed because the second processing value requires less input power than the first processing value to obtain the same output power. The smaller the pulse width, the higher the power efficiency. Similarly, the control pulse width is further shifted slightly to obtain a processing value (third processing value) at this time. Then, the two second and third processing values are compared. As a result of this comparison, when the third processing value is smaller than the second processing value,
Further, the power supply efficiency is higher when the control pulse width is slightly shifted. By repeating this control routine, the control pulse width Toffo that ultimately maximizes the power supply efficiency
pt will be obtained.

In this case, the control routine is not performed in a relatively long time unit, for example, by fixing the load factor to 50%. As shown by (power supply efficiency), there may be a sudden change from 50% to, for example, 100% in short time units. In such a case, a sudden change in the load factor is detected, and the same control routine as described above is performed. In other words, the processing time unit is divided into a long time unit (macro processing) and a short time unit (micro processing), and the power efficiency when viewed in a long time unit by the macro processing is averaged. While increasing the power efficiency in the long time unit, the power efficiency is high on average, but the power efficiency is prevented from decreasing in the short time unit due to sudden changes in load, etc., and high power efficiency is obtained in the short time unit by micro processing. I am trying to be.

Next, the PF using the power efficiency improvement described above
An embodiment of an M control type switching power supply will be described.

FIG. 13 shows a PF according to an embodiment of the present invention.
FIG. 2 is a circuit configuration diagram of an M-control switching power supply. Referring to FIG. 13, the switching power supply according to the embodiment includes input rectifying / smoothing unit 4, converter unit 6, switching element 8, output rectifying / smoothing unit 10, output voltage detecting unit 12, control block 14, input current detecting unit 16. , And an output current detection unit 18.

In the embodiment, the control block 14 includes an input current processing unit 14c and a control pulse width varying unit 14 in addition to the control unit 14a and the comparison feedback unit 14b.
d ', a load fluctuation detecting unit 14e, and a processing value memory 14f.

The control block 14 will be described.

The input current processing section 14c has a predetermined time ΔT
Processing the output of the input current detecting section 18 in the unit, but the macro processor 14c ₁ which functions to handle currents (macro processing) a predetermined time unit as long time unit [Delta] T _L
When, also has a micro-processing unit 14c ₂ which fulfills the function of processing (micro processing) an input current a predetermined time unit as a short time unit [Delta] T _S.

[0059] The input current processor 14c also macro treated processed value by the macro unit 14c ₁ (macro process value)
Micro-treated processed value at the micro processing unit 14c ₂ (micro processing value) and outputs respectively.

[0060] The input current unit 14c Moreover, when the trigger signal without input from the load variation detecting section 14e outputs a macro processed value of the macro unit 14c _1, the micro processor unit when the there is an input of the trigger signal outputting a micro-processed value of 14c _2.

[0061] Control variable pulse width portion 14d 'is the driving variable frequency signal corresponding to the calculation result performs a predetermined operation when the macro processed value from the macro unit 14c ₁ of the input current unit 14c is input, and outputs the drive frequency variable signal corresponding to the calculation result performs predetermined calculation when micro process value is inputted from the micro processor unit 14c ₂ of the input current processing unit 14c.

The processing value memory 14f can store and read out processing values.

The load fluctuation detecting section 14e detects a load fluctuation based on the detection output of the output current detecting section 16, and does not output a trigger signal when there is no load fluctuation or when the load fluctuation is below a predetermined level. When there is a load change, a trigger signal is output. Since the details of the load fluctuation detecting unit 14e have been described above, the description thereof is omitted.

The control section 14a includes a control pulse width varying section 14
The control pulse width is varied in response to the control pulse width variable signal from d '.

Hereinafter, the control operation of the control block 14 will be described with reference to the control flow of FIG.

When the power is turned on, the control pulse width Toff is determined by the RCC operation (S1) and detected (S2).

It is detected whether or not the detected Toff is larger than a predetermined minimum control pulse width Toff (min) (S3).

If Toff> Toff (min), T
Set off ₀ = Toff (S4).

If Toff <Toff (min), T
off (min), so that Toff ₀ = T
off (min) is set (S5).

At Toff ₀ set above, the average value Iin (a) of the input current for a predetermined period is set.
ve) ₀ is detected and stored (S6).

Here, Toff is deliberately shifted by a small value ΔT to set Toff ₁ = Toff ₀ + ΔT (S 7).

Then, the average value Iin (ave) ₁ of the input current during the period determined by Toff ₁ determined above is detected (S8).

The two values Iin (av
e) Compare ₀ and Iin (ave) ₁ (S9).

In the case of Iin (ave) ₀ > Iin (ave) ₁ , the shifted Toff ₁ has higher power efficiency, and the control pulse width Toff _{2 at} which the power efficiency becomes optimum.
= Toff ₁ is set (S10).

In the case of Iin (ave) ₀ <Iin (ave) ₁ , the shifted Toff ₁ has lower power efficiency, and the direction of the ΔT shift is wrong, which means that the power efficiency is higher. The control pulse width is shifted in the reverse direction, which is considered to be optimal, but the value Tof to be shifted is changed.
f ₀ −ΔT, and Toff whose value is set in advance
(Min) (S11).

If Toff ₀ −ΔT> Toff (min), Toff ₂ = Toff ₀ −ΔT is set (S1).
2).

If Toff ₀ -ΔT <Toff (min), Toff ₂ = Toff (min) is set (S13).

The obtained Toff ₂ is substituted for Toff ₀ which is a parameter of the basic control pulse width Toff (S14).

Here, whether or not a load change has occurred is checked by the load change detecting unit 14e for the presence or absence of a trigger signal (S
15) If there is a trigger signal, the process proceeds to S6, and if there is no trigger signal, the process proceeds to S2.

By repeating such a cycle, the power supply efficiency is maximized.

Also in the case of this PFM control method, the macro processing and the micro processing have the effect of further improving the power supply efficiency.

In the above description, once the switching power supply is installed, the input voltage is almost constant and does not fluctuate, and the input power is simply detected by the average value or integral value of the input current. are doing. The processing of the input current, the control pulse width variable control, and the like may be performed by software using a microcomputer, or may be performed by using analog circuit components.

[0083]

As described above, in the power supply device of the present invention, in any of the PWM control method and the PFM control method, the PWM control method is a PWM control method that has not been available before.
Since the drive frequency is used in the control method and the control pulse width is used in the PFM control method, the power supply efficiency can be further improved by slightly changing these control parameters.

[Brief description of the drawings]

FIG. 1 is a diagram showing a load factor vs. power supply efficiency for explaining power supply efficiency improvement of the present invention.

FIG. 2 is a driving frequency vs. power supply efficiency diagram for explaining the power supply efficiency improvement of the present invention.

FIG. 3 is a driving frequency vs. power supply efficiency diagram for explaining the improvement of the power supply efficiency of the present invention.

FIG. 4 is a driving frequency vs. power supply efficiency diagram for explaining the power supply efficiency improvement of the present invention.

FIG. 5 is a circuit diagram of a switching power supply according to an embodiment of the present invention.

FIG. 6 is a circuit diagram of a load fluctuation detecting unit in FIG. 5;

FIG. 7 is a timing chart for explaining the operation of the load fluctuation detecting unit in FIG. 6;

8 is a control flow chart for explaining the operation of the switching power supply in FIG. 5;

FIG. 9 is a diagram showing a load factor vs. power supply efficiency for explaining power supply efficiency improvement according to the present invention.

FIG. 10 is a diagram showing a control pulse width vs. power supply efficiency for explaining power supply efficiency improvement of the present invention.

FIG. 11 is a control pulse width vs. power supply efficiency chart for explaining the power supply efficiency improvement of the present invention.

FIG. 12 is a control pulse width vs. power supply efficiency chart for explaining the power supply efficiency improvement of the present invention.

FIG. 13 is a circuit diagram of a switching power supply according to another embodiment of the present invention.

FIG. 14 is a control flowchart for explaining the operation of the switching power supply in FIG. 13;

FIG. 15 is a circuit diagram of a conventional switching power supply.

[Explanation of symbols]

2 AC power supply 4 Input rectifying / smoothing unit 6 Converter unit 8 Switching element 10 Output rectifying / smoothing unit 14 Control block 14a Control unit 14b Comparison feedback unit 14c Input current processing unit 14c ₁ Macro processing unit 14c ₂ Microprocessing unit 14c ₂ 14d Driving frequency variable Unit 14f Process value memory 16 Output current detection unit

Claims (10)

[Claims] 1. A power supply device comprising: conversion means for converting an input voltage into a predetermined voltage; switching means for controlling a conversion operation of the conversion means; and control means for driving and controlling the switching means by a PWM control method. The power supply device according to claim 1, wherein a drive frequency is added to the control parameter of the switching means in addition to the control pulse width. 2. The power supply device according to claim 1, wherein said control means is capable of slightly changing said drive frequency with respect to power supply efficiency. 3. A power supply apparatus comprising: conversion means for converting an input voltage to a predetermined voltage; switching means for controlling a conversion operation of the conversion means; and control means for driving and controlling the switching means by a PFM control method. 2. The power supply device according to claim 1, wherein a control pulse width is added to the control parameter of the switching means in addition to the drive frequency. 4. The power supply device according to claim 3, wherein said control means is capable of minutely changing said control pulse width with respect to power supply efficiency. 5. The power supply device according to claim 1, wherein the control unit performs a predetermined process on the input power signal in a predetermined time unit, and uses a result of the process. The power supply device, wherein the control parameter is controlled so that the input power is reduced. 6. The power supply device according to claim 5, wherein the control means performs the processing in a predetermined long time unit and a predetermined short time unit in accordance with a load state. And a power supply device. 7. A power supply device for converting and controlling an input voltage to a predetermined voltage, wherein a predetermined process is performed on a signal of the input power in a predetermined time unit, and the input power The power supply device is configured to control the power supply in a smaller direction. 8. The power supply device according to claim 7, wherein an input current detection signal is used as the input power signal. 9. A power supply efficiency improving method in a power supply device for converting and controlling an input voltage to a predetermined voltage, wherein a predetermined process is performed on a signal of the input power in a predetermined time unit, and a result of the process is used. Controlling the input power in a smaller direction to improve power efficiency. 10. The power efficiency improving method according to claim 9, wherein said predetermined time unit is divided into a predetermined long time unit and a predetermined short time unit according to a load state. To improve power efficiency.