JP2002262565A - Switching power supply - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a switching power supply wherein a correct timing of a operation is provided even if any delay is present in a signal part for controlling a switch element in a switching circuit. SOLUTION: The switching power supply is provided with the switching circuit 2 for converting a direct-current input into an alternating currents through a switching operation; an output rectifying circuit 5 and an output smoothing circuit 6 that include at least an inductor and convert an alternating current into a direct-current output; and a control circuit 7 that controls the switching operation of the switching circuit 2. The control circuit 7 includes a first means for detecting the value of an inductor current flowing to the inductor, and a second means for correcting the detected value of the inductor current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a switching power supply, and more particularly, to a switching power supply capable of obtaining correct operation timing.

[0002]

2. Description of the Related Art Heretofore, a so-called DC / DC converter has been known as a switching power supply device. In a typical DC / DC converter, a DC input is once converted into an AC using a switching circuit, then transformed (step-up or step-down) using a transformer, and further converted into a DC using an output circuit. This makes it possible to obtain a DC output having a voltage different from the input voltage.

Here, a choke input type smoothing circuit is sometimes used as an output circuit used in a DC / DC converter. When a choke input type smoothing circuit is used as the output circuit of the DC / DC converter, the operation of the switching circuit is controlled so that the output voltage becomes a constant value by monitoring the output voltage, the inductor current, and the like.

As an example of performing such operation control, there is a switching power supply device described in Japanese Patent Application Laid-Open No. H11-206119.

In the switching power supply device described in the publication, an output voltage, an inductor current and the like are sampled at a predetermined timing, and an operation timing is determined by performing an operation according to a predetermined algorithm based on the output voltage and the inductor current. .

[0006]

Generally, a switching element (such as a transistor) having a large driving capability is used in a switching circuit of a switching power supply. Therefore, a drive circuit is required to control the on / off of the switching element. Is often used. On the other hand, it is necessary to use a value at a predetermined timing, for example, a timing at which the switch element is turned off, as data such as an inductor current used for the calculation.

However, since the drive circuit has a predetermined delay, a predetermined deviation occurs between the timing when switching is instructed and the timing when the switch element is actually turned off. Therefore, if the inductor current or the like is sampled in response to the timing of instructing the switching, the sampling timing is shifted from a desired timing, and data including an error is sampled. Due to such an error, the operation timing obtained as a result of the calculation is also inconsistent.
It has not always been possible to obtain the correct operation timing of the switching circuit.

Therefore, an object of the present invention is to provide a switching power supply device capable of obtaining correct operation timing even when a signal path for controlling a switching element of a switching circuit has a delay. is there.

[0009]

SUMMARY OF THE INVENTION The object of the present invention is as follows.
DC-AC conversion means for converting DC input into AC by switching operation, AC-DC conversion means having at least an inductor and converting the AC into DC output, and controlling the switching operation of the DC-AC conversion means. A control circuit, wherein the control circuit includes first means for detecting a value of an inductor current flowing through the inductor, and second means for correcting the detected value of the inductor current. This is achieved by a switching power supply.

According to the present invention, the detected inductor current value is corrected even if there is a delay in the signal path for controlling the switching operation by the DC-AC conversion means. A correct value of the inductor current in consideration of the delay can be obtained. Therefore, it is possible to obtain correct operation timing.

In a preferred embodiment of the present invention, the detection by the first means is performed in response to an instruction of the switching operation from the control circuit to the DC-AC conversion means.

In a further preferred aspect of the present invention, the second means corrects the detected value of the inductor current to substantially the peak value of the inductor current.

In a further preferred aspect of the present invention, the second means substantially calculates an error between the detected value of the inductor current and the peak value of the inductor current, Fourth means for adding the detected value of the inductor current and the error.

In a further preferred aspect of the present invention, the calculation by the third means and the addition by the fourth means are executed by software.

In another preferred embodiment of the present invention, at least one of the calculation by the third means and the addition by the fourth means is executed by hardware.

In a further preferred aspect of the present invention, the calculation by the third means is performed after the control circuit instructs the DC-AC conversion means to perform the switching operation. The switching is performed based on at least a delay time before the means performs the switching operation.

In a further preferred aspect of the present invention, the AC-DC converter includes a transformer for transforming the AC, an output rectifier circuit for rectifying an output of the transformer, and an output rectifier circuit including the inductor. An output smoothing circuit for smoothing the output.

The object of the present invention is also a DC-AC converter for converting a DC input into an AC by a switching operation, an AC-DC converter having at least an inductor for converting the AC into a DC output, A control circuit for controlling the switching operation of the AC conversion means, wherein the control circuit periodically detects a value of an inductor current flowing through the inductor; and at least detection by the first means. The DC-
And second means for instructing the AC conversion means to perform the switching operation, wherein the detection by the first means comprises:
This is achieved by a switching power supply device, which is performed after a lapse of a predetermined time after the instruction is performed by the second means.

According to the present invention, even when there is a delay in the signal path for controlling the switching operation by the DC-AC converter, the detection of the inductor current can be performed by the detection of the switching operation for the DC-AC converter. Since the processing is performed after a lapse of a predetermined time from the instruction, a correct value of the inductor current in consideration of the delay can be obtained. Therefore, it is possible to obtain correct operation timing.

In a preferred embodiment of the present invention, after the second unit instructs the DC-AC conversion unit to perform the switching operation for the predetermined time, the DC-AC conversion unit starts the switching operation. It is substantially equal to the delay time before the operation is performed.

[0021]

BRIEF DESCRIPTION OF THE DRAWINGS FIG.
A preferred embodiment of the present invention will be described in detail.

FIG. 1 is a circuit diagram showing a switching power supply according to a preferred embodiment of the present invention.

As shown in FIG. 1, the switching power supply according to this embodiment includes a switching circuit 2 connected to a DC input power supply 1, an inductor 3 connected to one output of the switching circuit 2, and a switching circuit. Circuit 2
A main transformer 4 having a primary winding connected between the other output of the main transformer 4 and the inductor 3;
An output rectifier circuit 5 connected to the next winding;
, A control circuit 7 and a drive circuit 8. The output of the output smoothing circuit 6 is connected to a load 9.

The switching circuit 2 includes switch elements 11 and 12 connected in series between the DC input power supplies 1, and switch elements 1 and 12 similarly connected in series between the DC input power supplies 1.
3 and 14, the nodes of the switch elements 11 and 12 are connected to one end of the primary winding of the main transformer 4 via the inductor 3, and the switch elements 13 and 14
Is directly connected to the other end of the primary winding of the main transformer 4. As shown in FIG. 1, in this embodiment, n-channel MOSFETs are used as the switch elements 11 to 14.

The inductor 3 includes switching elements 11 to 14
Together with the parasitic capacitance of the resonance circuit. As a result, the switching elements 11 to 14 are turned on by ZVS.
(Zero Voltage Switching) is possible, so that switching loss is reduced and noise is suppressed.

The main transformer 4 is a transformer having a turn ratio between the primary winding and the secondary winding of 1: m, and has two secondary windings as shown in FIG. The midpoint between these two secondary windings is connected to the negative terminal of the load 9. Hereinafter, the voltage generated in the primary winding of the main transformer 4 is referred to as V1
Is defined.

The output rectifier circuit 5 is connected to the main transformer 4
At the end of the secondary winding, there are provided two diodes 15 and 16 each having an anode connected, and the cathodes of these two diodes are connected in common. Hereinafter, the common cathode connection point of these two diodes 15 and 16 is called a “rectification point”, and the voltage appearing here is defined as V2.

The output smoothing circuit 6 includes an inductor 17 connected between the rectification point and the positive terminal of the load 9 and a load 9.
, And a capacitor 18 connected between both ends of the capacitor. Hereinafter, the voltage appearing across the load 9 is referred to as “output voltage (V
o), and the current flowing through the load 9 is referred to as the “output current (I
o) ". Further, the current flowing through the inductor 17 is referred to as “inductor current IL”. As shown in FIG. 1, between the negative terminal of the load 9 and the main transformer 4,
A current detection circuit 19 for detecting the inductor current IL is provided.

The control circuit 7 samples the output voltage Vo /
A sample / hold circuit 21 for holding, a sample / hold circuit 22 for sampling / holding the inductor current IL detected by the current detection circuit 19, a sample / hold circuit 23 for sampling / holding the voltage V2 at the rectification point, Sample / hold circuits 21
A / D converters 24 to 26 for converting the analog values held in 23 into digital values, an arithmetic unit 27 for performing a predetermined arithmetic operation based on digital outputs from these A / D converters 24 to 26, and an arithmetic unit And a phase control signal generator 28 that generates a phase control signal (gs11 to gs14) to be given to the switch elements 11 to 14 based on the calculation result by the switch 27. Sampling by the sample / hold circuits 21 and 22 is performed in response to a sampling signal S generated by the arithmetic unit 27.

FIG. 2 is a circuit diagram schematically showing an internal configuration of drive circuit 8.

As shown in FIG. 2, the drive circuit 8 includes four drivers 31 to 34. Drivers 31 to 3
4 are the corresponding phase control signals (gs11 to gs
14) to generate a phase control signal (GS11 to GS14) amplified to a voltage and current level capable of driving the switch elements 11 to 14 of the switching circuit 2, and to generate the phase control signals (GS11 to GS14) corresponding to the gates of the corresponding switch elements 11 to 14. Respectively. Since the drivers 31 to 34 each have a predetermined delay, the output phase control signal (GS1) is output.
1 to GS14) correspond to the input phase control signal (g
The waveform is delayed by the delay from the waveforms of s11 to gs14).

FIG. 3 is an operation waveform diagram showing a basic operation of the switching power supply according to the present embodiment.

The basic operation of the switching power supply according to this embodiment is as follows. That is, GS11
And GS14 are at a high level, that is, while the switch elements 11 and 14 are both on, the DC input power supply 1 is connected to the primary winding of the main transformer 4.
Is applied in one direction, and a DC input power supply is applied to the primary winding of the main transformer 4 during a period when both GS12 and GS13 are at a high level, that is, a period when both the switching elements 12 and 13 are on. By applying the input voltage Vin from No. 1 in the reverse direction, the voltage V1 generated in the primary winding of the main transformer 4 has an AC waveform. The peak value of the AC waveform is multiplied by m in the secondary winding of the main transformer 4 and further rectified by the output rectifier circuit 5.

Here, GS11 and GS1 in FIG.
4 is high level, and GS12
The reason why the voltages V1 and V2 are not generated and the inductor current IL continues to decrease in the initial period of the period when both the GS13 and the GS13 are at the high level is that the energy regeneration of the inductor 17 is not completed.

As shown in FIG. 3, the voltage V2 at the rectification point
Is a pulse waveform having a predetermined width whose peak value is Vin × m, and its time average value is the output voltage Vo. Therefore, in order to control the value of the output voltage Vo, the phases of GS11 and GS14 and GS12 and G
What is necessary is just to control the phase of S13. Further, the waveform of the inductor current IL is a waveform obtained by superimposing the ripple current determined by the voltage waveform V2 at the rectification point and the inductance of the inductor 17 on the output current Io.

Now, in order to maintain the output voltage Vo at a desired constant value, it is necessary to control the phase difference between the phase control signals (gs11 and gs14) and the phase difference between the phase control signals (gs12 and gs13). Such control is performed by performing a predetermined calculation based on the result of sampling performed for each integral multiple of one cycle of the phase control signal generated by the phase control signal generation unit 28. In order to correctly perform such an operation, for example, it is necessary to execute sampling at the peak of the inductor current IL.

Here, in order to execute sampling at the peak of the inductor current IL, the phase control signal G
The sampling signal S may be generated in response to the fall of S11 or GS12. However, as described above, the phase control signal (output to the drive circuit 8 due to the delay of the drivers 31 to 34 constituting the drive circuit 8) GS1
1 to GS14) and the input phase control signal (gs)
11 to gs14) do not match. On the other hand, various internal signals in the arithmetic unit 27 are phase control signals (gs11 to gs11).
Since the waveform substantially coincides with the waveform of s14), when the sampling signal S is generated using such an internal signal, the sampling timing is shifted from the peak of the inductor current IL.

FIG. 4 shows the phase control signals (gs11 to gs1).
FIG. 4 is an enlarged timing chart showing a relationship between 4) and a waveform of an inductor current IL and a phase control signal (GS11 to GS14).

As shown in FIG. 4, if the value of the inductor current IL is sampled in response to the falling edge of the phase control signal gs11, the obtained value is smaller than the peak of the inductor current IL by the error Δi. Only a small value. This is the same when the value of the inductor current IL is sampled in response to the falling edge of the phase control signal gs12.

For this reason, in the switching power supply according to the present embodiment, the inductor current IL is corrected in consideration of the error Δi. Hereinafter, the inductor current I
L and the phase control signal (gs11) based on the corrected inductor current IL (corrected inductor current IL ′).
And gs14) and the phase control signal (gs12 and gs)
The method of determining the phase of 13) will be described in detail.

FIG. 5 is a flowchart showing an algorithm for determining the operation timing of the switching circuit 2. The calculation according to the algorithm is executed in software in the calculation unit 27.

First, the operation unit 27 outputs the phase control signal gs11.
Generates the sampling signal S in response to the generation timing of the sampling / hold circuit 2 in response to this.
1 to 23 are performed (step S
1). As described above, the sample / hold circuit 21 samples the output voltage Vo, the sample / hold circuit 22 samples the inductor current IL detected by the current detection circuit 19, and the sample / hold circuit 23
Samples the voltage V2 at the rectification point. The output voltage Vo, the inductor current IL, and the voltage V2, which are analog values held in the sample / hold circuits 21 to 23, are converted into digital signals by A / D converters 24 to 26, respectively, and supplied to the arithmetic unit 27. You.

In the arithmetic section 27 having received the digital signal, first, an error 式 i is calculated based on equation (1) (step S2).

[0044]

(Equation 1) Here, Tdelay is a phase control signal (gs11 to gs).
phase control signal (GS11 to GS14) for s14)
And substantially coincides with the delay times of the drivers 31 to 34 constituting the drive circuit 8. However, in addition to the drivers 31 to 34, the phase control signals (GS11 to GS
If there is a factor causing a substantial delay in 14), it is preferable to determine Tdelay in consideration of the factor. Lf is the inductance of the inductor 17.

When the error Δi is obtained in this way,
Next, a corrected inductor current IL ′ is calculated based on the equation (2) (step S3).

[0046]

(Equation 2) The value of the corrected inductor current IL ′ thus obtained becomes substantially equal to the peak value of the inductor current IL.

Thus, the correction inductor current IL '
Is obtained, a control signal for generating the phase control signals (gs11 to gs14) is actually generated using the correction inductor current IL ′ and the like (step S4).

Next, generation of the control signal (step S4) will be described in detail.

FIG. 6 shows the generation of a control signal (step S4).
6 is a flowchart showing in more detail.

In the generation of the control signal (step S4), first, the current command value ir (n +
1) is calculated (step S11). Here, the current command value ir (n + 1) is a control target value of the inductor current IL at the sampling point (n + 1).

[0051]

(Equation 3) Here, n is an arbitrary positive integer indicating a sampling point. ΔVo (n-1) is the sampling point (n-1)
Indicates the value of △ Vo calculated based on the detection value obtained in. Note that Vref is a required output voltage value (reference voltage value), and K1 and K2 are circuit constants.

Thus, the current command value ir (n + 1)
Is calculated, the input voltage estimated value tpv (n) is calculated based on the equation (4) (step S12). Here, the input voltage estimated value tpv (n) is a value calculated based on the value detected at the sampling point n-1, and can be expressed as Tsw / Vs (n). Here, Tsw is の of the switching period, Vs (n)
Is the input voltage Vin (n) multiplied by the number m of secondary windings of the transformer, and is m × Vin (n).

[0053]

(Equation 4) Here, K is a circuit constant, and ie (n-1) is an estimated current value. The estimated current value ie (n) is a value of the inductor current IL expected at the sampling point (n). In the equation (4), the estimated current value ie (n−n) calculated based on the detection value obtained at the sampling point (n−2).
1) and the input voltage estimated value tpv (n-1) calculated based on the detected value obtained at the sampling point (n-2), so that the estimated current value ie is obtained as in the initial state. (N
-1) or when the input voltage estimated value tpv (n-1) does not exist, the estimated current value ie (n-1) is 0 (zero), and the input voltage estimated value tpv (n-1) is a predetermined value. Is calculated as

Thus, the estimated input voltage tpv
When (n) is obtained, next, a threshold value Vd (n) is calculated based on Expression (5) (Step S13).

[0055]

(Equation 5) In calculating the threshold value Vd (n), the table 30 in the arithmetic unit 27 is referred to. That is, the memory is read using the input voltage estimated value tpv (n) obtained in step S2 as an address, and table (tpv (n)), which is data stored therein, is used. The address of this table 30 (input voltage estimated value tpv
(N)) and the corresponding data (table (tpv
(N))) is represented by a general formula (6).

[0056]

(Equation 6) Here, Lf is the inductance of the inductor 17.

After the threshold value Vd is obtained in this manner, the threshold value Vd (n) is compared with the reference voltage value Vref (step S14).

This comparison is performed to determine whether the inductor current IL is in a continuous state or a discontinuous state. If the threshold value Vd (n) is larger than the reference voltage value Vref, the state is a continuous state. And the threshold value Vd
If (n) is smaller than the reference voltage value Vref, it is determined that the state is a discontinuous state. Here, the continuous state refers to a state in which the inductor current IL is constantly flowing, and this state occurs when the driven load 9 is large (when the output current Io is large). On the other hand, the discontinuous state refers to a state in which the current IL is intermittently flowing through the inductor, and this state occurs when the driven load 9 is small (the output current Io is small).

Specifically, as shown in FIG. 3, a state where the lower end of the waveform of the inductor current IL is 0 A (ampere) or more is a continuous state.

FIG. 7 is a waveform diagram showing a state in which the lower end of the waveform of inductor current IL is 0A. As shown in FIG. 7, the value of the output current Io when the lower end of the waveform of the inductor current IL is 0 A is defined as Icp.

When the value of the output current Io falls further below Icp, the inductor current IL flows intermittently through the inductor 17. That is, a discontinuous state occurs.

FIG. 8 is a waveform diagram showing a case where inductor current IL is in a discontinuous state.

That is, when the value of the output current Io is Icp (FIG. 7) and when the output current Io is larger than this, the inductor current IL is in a continuous state (FIG. 3).
And if smaller than this, the inductor current IL
Becomes a discontinuous state (FIG. 8). Output current amount Ic defining the boundary between continuous state and discontinuous state of inductor current IL
p is called a discontinuity point (critical point).

If it is determined in step S14 that the threshold value Vd (n) is larger than the reference voltage value Vref (in a continuous state), then the estimated current value is calculated based on equation (7). ie (n) is calculated (step S
15).

[0065]

(Equation 7) Here, vir (n) is a command voltage value, that is, a control target value of the output voltage Vo at the sampling point (n). In equation (7), the command voltage value vir (n−n) calculated based on the detection value obtained at the sampling point (n−2)
Since 1) is used, the command voltage v
If ir (n-1) does not exist, it is calculated as 0 (zero).

When the estimated current value ie (n) is obtained in this way, the command voltage value vi (n) is then calculated based on equation (8).
r (n) is calculated (step S16).

[0067]

(Equation 8) When the command voltage value vir (n) is obtained, the phase phase (n) is calculated based on the equation (9) (step S17).

[0068]

(Equation 9) The phase phase (n) is the phase of the phase control signals (gs11 and gs14) to be generated by the phase control signal generator 28 at the sampling point (n) and the phase control signal (g
s12 and gs13), and the phase control signal generator 28 receives the information and determines the phase control signal (gs).
11 and gs14) and the phase of the phase control signals (gs12 and gs13).

On the other hand, if it is determined in step S14 that threshold value Vd (n) is smaller than reference voltage value Vref (discontinuous state), threshold value Vd (n) obtained in step S13 is obtained. ) Is directly used as the command voltage value vir (n) (step S18), and then the estimated current value ie (n) is calculated based on equation (10) (step S19).

[0070]

(Equation 10) Thereafter, in the same manner as described above, the phase p
phase (n) is calculated (step S17), and the phase control signal (gs1) is calculated based on the phase (n).
1 to gs14) are generated.

FIG. 9A is a graph showing the relationship (output voltage drooping characteristic) between the output current Io and the output voltage Vo at the time of overcurrent in the conventional switching power supply device for each input voltage Vin. (B) is a graph showing the relationship (output voltage drooping characteristic) between the output current Io and the output voltage Vo at the time of an overcurrent for each input voltage Vin in the switching power supply device according to the present embodiment. In each case, the output current Io is controlled to be limited to 85A.

As shown in FIG. 9A, the output current I
It can be seen that in the conventional switching power supply device, the output current Io fluctuates greatly depending on the input voltage Vin and the output voltage Vo even if control is performed so that o is limited to 85 A. This is because the generation timing of the sampling signal S is shifted from the peak of the inductor current IL, so that an appropriate phase phase (n) cannot be obtained. On the other hand, as shown in FIG.
In the switching power supply according to the present embodiment,
Over a wide range of the input voltage Vin and the output voltage Vo,
It can be seen that the output current Io is limited to 85A.

As described above, in the present embodiment, the value of the actually detected inductor current IL is corrected, and the phase phase is corrected based on the corrected inductor current IL ′.
Since (n) is generated, an appropriate phase phase
(N) can be obtained.

In the present embodiment, the input voltage estimation value tpv (n) calculated based on the detected output voltage Vo and the corrected inductor current IL 'is used, and based on this, the threshold value Vd (n) is used. Is calculated and the threshold voltage Vd (n) is compared with the reference voltage value Vref to determine whether the inductor current IL is in a continuous state or in a discontinuous state. The input voltage estimated value tpv (n) is different from the predetermined value, particularly, even when the input voltage is fluctuating.
This makes it possible to make the above determination accurately.

Further, in the present embodiment, when it is determined that the inductor current IL is in a discontinuous state, the threshold value Vd (n) obtained by using the output voltage Vo and the corrected inductor current IL 'is determined. Command voltage value vir (n)
Therefore, even if the input voltage is different from the predetermined value, in particular, even if the input voltage fluctuates, the appropriate phase phas is determined in step S17.
e (n) can be obtained.

As a result, in the switching power supply according to the present embodiment, even when the input voltage fluctuates, the correct operation timing of the switching circuit 2 can be obtained. The output voltage Vo can be stabilized at a desired value (Vref) both in a certain case and in a discontinuous state.

Generation of a control signal (step S4)
Is not limited to the algorithm shown in FIG. 6, but may be performed according to a different algorithm.

FIG. 10 is a flowchart showing in detail the generation of a control signal by another algorithm (step S4).

In the generation of the control signal by the present algorithm, first, the current command value ir (n
+1) is calculated (step S21), and then the estimated input voltage value tpv (n) is calculated based on equation (4) (step S22). That is, these steps S
21 and S22 correspond to steps S11 and S22 shown in FIG.
Same as 12.

Thus, the current command value ir (n + 1)
When the estimated input voltage value tpv (n) is obtained, the current command value ir (n + 1) is compared with the specified value id (step S23).

This comparison is performed to determine whether the inductor current IL is continuous or discontinuous. If the current command value ir (n + 1) is larger than the specified value id, it is determined that the current is continuous. Is determined and the current command value ir (n
If +1) is smaller than the specified value id, it is determined that the state is discontinuous. Here, the specified value id is a discontinuous point (critical point) calculated from an arbitrary point within a rated input voltage range defined by the specifications of the switching power supply device. It is calculated using a predetermined standard input voltage value.

As a result of this determination, the current command value ir (n +
If 1) is determined to be larger than the specified value id (continuous state), then the estimated current value ie (n) is calculated based on equation (7).
Is calculated (step S24), and then the command voltage value vir (n) is calculated based on equation (8) (step S24).
25) Further, based on the equation (9), the phase
(N) is calculated (step S26). That is, steps S24 to S26 are the same as steps S15 to S17 shown in FIG.

On the other hand, if the result of determination in step S23 is that the current command value ir (n + 1) is smaller than the specified value id (discontinuous state), then the command voltage value is determined based on equation (11). vir (n) is calculated (step S27).

[0084]

[Equation 11] When the command voltage value vir (n) is obtained in this manner, next, the estimated current value ie (n) is calculated based on Expression (10).
Is calculated (step S28). That is, step S28 is the same as step S19 shown in FIG.

When the command voltage value vir (n) is obtained, the phase phase is then calculated based on equation (9).
(N) is calculated (step S26), and the phase ph is calculated.
phase (n) based on the phase control signals (gs11-gs)
14) is generated.

If the control signal is generated by the present algorithm (step S4), it is not necessary to provide the table 30 in the arithmetic unit 27. For this reason, it is possible to reduce the circuit scale required for the arithmetic unit 27.

FIG. 11 is a flowchart showing in detail the generation of a control signal by another algorithm (step S4).

In this algorithm, steps S27 and S28 in the above algorithm are replaced with step S37, and the other steps S31 to S36 are steps S21 to S36 in the above algorithm, respectively.
The content is the same as 26.

In step S37, the estimated current value i
e (n) and the command voltage value vir (n) are forcibly set to 0 (zero), whereby the phase phase (n) and Ts
w is equal. As described above, since Tsw is the period of the phase control signal generated by the phase control signal generation unit 28, the fact that the phase phase (n) is equal to Tsw means that the overlap between the phase control signals gs11 and gs14 is eliminated and , Phase control signals gs12 and gs13
Means that there is no overlap. This allows
In the switching circuit 2, the output of electric power disappears.

When the control signal is generated by the present algorithm (step S4), the table 3
Since there is no need to provide 0, it is possible to reduce the circuit scale required for the operation unit 27.

Next, a switching power supply according to another preferred embodiment of the present invention will be described.

In the switching power supply according to the above embodiment, the calculation of the error Δi (step S2) and the calculation of the correction inductor current IL ′ (step S3) are performed by software. The switching power supply device differs in that these are performed by hardware. The other parts are the same as those of the switching power supply according to the above-described embodiment, and the duplicated description will be omitted.

FIG. 12 shows the calculation of the error △ i (step S
2) and calculation of the corrected inductor current IL '(step S
It is a block diagram which shows the hardware constitutions for performing 3).

As shown in FIG. 12, in the present embodiment, the analog output (output voltage Vo) from the sample / hold circuit 21 and the analog output (voltage V2) from the sample / hold circuit 23 are subtracted. Subtractor 35 and an amplifier 36 receiving an output from the subtractor 35
And an adder 37 that receives the analog output (inductor current IL) from the sample / hold circuit 22 and the output of the amplifier 36 and performs addition.

The subtractor 35 is connected to the sample / hold circuit 2
The analog value held in the sample / hold circuit 21 is subtracted from the analog value held in 3. Thus, the analog output of the subtractor 35 indicates the value of V2−Vo.

The amplifier 36 has a gain (amplification factor) of Tdelay / Lf. Thereby, the analog output of the amplifier 36 indicates the value of (V2−Vo) Tdelay / Lf.

The adder 37 is connected to the sample / hold circuit 2
The analog value held at 3 and the analog value output from the amplifier 36 are added. Thus, the analog output of the adder 37 indicates the value of IL + (V2-Vo) Tdelay / Lf, and the generation of the analog value indicating the correction inductor current IL 'is completed.

The analog value indicating the corrected inductor current IL ′ generated in this manner is output from the A / D converter 25.
And converted into a digital signal. Hereinafter, the value of the corrected inductor current IL ′ converted into a digital signal by the A / D converter 25 is calculated together with the values of the output voltage Vo and the voltage V2 converted into digital signals by the A / D converters 24 and 26, respectively.
7 and is calculated according to the same algorithm as in the above embodiment.

As described above, in the present embodiment, the calculation of the error Δi (step S2) and the correction inductor current I
Since the calculation of L '(step S3) is performed by hardware, these calculations are performed at extremely high speed. For this reason, it is possible to effectively prevent performance degradation caused by performing these calculations.

In the above embodiment, both the calculation of the error Δi (step S2) and the calculation of the correction inductor current IL ′ (step S3) are performed by hardware, but only one of them is performed by hardware. You may go for the wear.

Next, a description will be given of a switching power supply according to still another preferred embodiment of the present invention.

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

As shown in FIG. 13, in the switching power supply according to the present embodiment, the control circuit 7 included in the switching power supply shown in FIG.
8 has been replaced. The control circuit 38 is provided with a delay circuit 39 for delaying the sampling signal S, and the sample / hold circuits 21 and 22 are supplied with the delayed sampling signal S 'delayed by the delay circuit 39.

Here, the delay time of the delay circuit 39 is Tde
lay. As described above, Tdelay
Is a delay time of the phase control signals (GS11 to GS14) with respect to the phase control signals (gs11 to gs14), and substantially coincides with the delay times of the drivers 31 to 34 configuring the drive circuit 8. However, if there is a factor that causes a substantial delay in the phase control signals (GS11 to GS14) other than the drivers 31 to 34, Td is also taken into consideration.
Preferably, elay is determined.

As described above, in this embodiment, since the delay circuit 39 for delaying the sampling signal S is provided, the sample / hold circuits 21 and 22 can perform sampling using the delayed sampling signal S '. it can. As described above, the delay time of the delay circuit 39 is Td
Since it is set to elay, sampling can be performed at the timing when the inductor current IL shows a peak.

In the present embodiment, in the algorithm for determining the operation timing of the switching circuit 2, steps S2 and S3 shown in FIG. 5 are omitted, and the inductor current il detected by the current detection circuit 19 is corrected. The following calculation (step S
Used in 4).

The present invention is not limited to the above embodiments, and various changes can be made within the scope of the invention described in the claims, and these are also included in the scope of the present invention. It goes without saying that it is a thing.

In other words, the switching power supply device to which the present invention can be applied is not limited to the switching power supply device having the circuit configuration shown in FIG. 1, but can be applied to a switching power supply device having another circuit configuration. FIG. 14 shows an example of a switching power supply device having another circuit configuration.
Shown in When the present invention is applied to the switching power supply having the circuit configuration shown in FIG. 14, the ON period of the switch element 10 may be determined based on ton. Of course, the present invention can be applied to a switching power supply device having a circuit configuration other than the above. According to the circuit configuration, control of the switching circuit is performed not only by the phase and the on period ton, but also by the duty, the off period, the frequency, May be performed using the above signal.

In each of the above embodiments, the voltage V2 at the rectification point is actually measured. Instead, the value of Vs is estimated from the detected inductor current IL and the output voltage Vo. It may be V2. in this case,
As shown in FIG. 12, the calculation of the error △ i (step S
2) and calculation of the corrected inductor current IL '(step S
In the case where step 3) is performed by hardware, the value V2 set as a digital value may be converted into an analog value by a D / A converter and supplied to the subtractor 35.

Further, the secondary side voltage of the main transformer 4 and the voltage between both ends of the diode 15 or 16 are measured.
This may be used instead of the voltage V2 at the rectification point.
Alternatively, the voltage V2−Vo between both ends of the inductor 17 may be measured and used.

[0111]

As described above, according to the present invention,
It is possible to provide a switching power supply device that can obtain correct operation timing even when a delay exists in a signal path for controlling a switching element of a switching circuit.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a switching power supply device according to a preferred embodiment of the present invention.

FIG. 2 is a circuit diagram schematically showing an internal configuration of a drive circuit 8.

FIG. 3 is an operation waveform diagram showing a basic operation of the switching power supply device according to a preferred embodiment of the present invention.

FIG. 4 is a timing diagram showing, in an enlarged manner, a relationship between PWM waves (gs11 to GS14) and PWM waves (GS11 to GS14) and a waveform of an inductor current IL.

FIG. 5 is a flowchart showing an algorithm for determining the operation timing of the switching circuit 2.

FIG. 6 is a flowchart showing the generation of a control signal (step S4) in more detail.

FIG. 7 is a waveform diagram showing a state in which the lower end of the waveform of the inductor current IL is 0A.

FIG. 8 is a waveform diagram showing a case where the inductor current IL is in a discontinuous state.

FIG. 9A is a graph showing the relationship (output voltage drooping characteristic) between the output current Io and the output voltage Vo at the time of an overcurrent for each input voltage Vin in the conventional switching power supply device, and FIG. Is the output current Io at the time of overcurrent in the switching power supply according to the present embodiment.
6 is a graph showing the relationship between the output voltage Vo and the output voltage Vo (output voltage drooping characteristic) for each input voltage Vin.

FIG. 10 is a flowchart showing in detail the generation of a control signal by another algorithm (step S4).

FIG. 11 is a flowchart showing in detail the generation of a control signal by another algorithm (step S4).

FIG. 12 is a block diagram showing a hardware configuration for calculating an error Δi (step S2) and calculating a correction inductor current IL ′ (step S3).

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

FIG. 14 is a circuit diagram showing an example of a switching power supply device having another circuit configuration.

[Explanation of symbols]

 REFERENCE SIGNS LIST 1 DC input power supply 2 switching circuit 3 inductor 4 main transformer 5 output rectifier circuit 6 output smoothing circuit 7 control circuit 8 drive circuit 9 load 10 to 14 switch element 15, 16 diode 17 inductor 18 capacitor 19 current detection circuit 21 to 23 samples / Hold circuit 24 to 26 A / D converter 27 Operation unit 28 PWM waveform generation unit 31 to 34 Driver 35 Subtractor 36 Amplifier 37 Adder 38 Control circuit 39 Delay circuit

Claims (10)

[Claims] A DC-AC converter for converting a DC input into an AC by a switching operation; an AC-DC converter having at least an inductor for converting the AC into a DC output; A control circuit for controlling a switching operation, wherein the control circuit detects a value of an inductor current flowing through the inductor.
And a second unit for correcting the value of the detected inductor current. 2. The switching power supply according to claim 1, wherein said detection by said first means is performed in response to an instruction of said switching operation to said DC-AC conversion means by said control circuit. apparatus. 3. The switching device according to claim 1, wherein said second means corrects the value of the detected inductor current to substantially a peak value of the inductor current. Power supply. 4. The third means for substantially calculating an error between the detected value of the inductor current and the peak value of the inductor current, and the value of the detected inductor current. 4. The switching power supply device according to claim 3, further comprising a fourth means for adding the error and the error. 5. The switching power supply according to claim 4, wherein said calculation by said third means and said addition by said fourth means are executed by software. 6. The switching power supply according to claim 4, wherein at least one of said calculation by said third means and said addition by said fourth means is executed by hardware. 7. The calculation by the third means is performed from when the control circuit instructs the DC-AC conversion means to perform the switching operation to when the DC-AC conversion means performs the switching operation. The switching power supply according to any one of claims 4 to 6, wherein the switching power supply is performed based on at least the delay time. 8. An AC-DC converter comprising: a transformer for transforming the AC; an output rectifier circuit for rectifying an output of the transformer; an output smoothing circuit including the inductor for smoothing an output of the output rectifier circuit. The switching power supply device according to claim 1, further comprising: 9. A DC-AC converter for converting a DC input to an AC by a switching operation, an AC-DC converter having at least an inductor and converting the AC to a DC output, and a DC-AC converter for the DC-AC converter. A control circuit for controlling a switching operation, wherein the control circuit periodically detects a value of an inductor current flowing through the inductor, and the DC circuit based on at least a detection result by the first means. A second means for instructing the AC conversion means to perform the switching operation, wherein the detection by the first means is performed after a lapse of a predetermined time after the instruction is performed by the second means. A switching power supply device characterized by the above-mentioned. 10. The delay time from when the second means instructs the DC-AC conversion means to perform the switching operation until when the DC-AC conversion means performs the switching operation. 10. The switching power supply according to claim 9, wherein