JPH11275856A - Ac-to-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To perform inexpensive power factor improvement control of an input power source, when AC power is rectified and DC power is supplied. SOLUTION: A converter is provided with a reference apparatus 12 which outputs an output voltage reference signal, a proportional/integrator 13 which proportions/integrates the deviation between the output signal of the reference apparatus 12 and an output voltage signal, and a current following-up circuit 9 which receives as an input of an output current reference signal an added signal of the output signal of the proportional/integrator to a signal obtained by multiplying the output signal of a rectifier 2 by a coefficient set beforehand, and controls the switching of a switching device 5 so as to follow up an output current reference signal, receiving an output current signal as an input.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC / DC converter for rectifying an AC power supply voltage and supplying DC power, and more particularly to control of an input current based on an input voltage waveform for improving an input power supply power factor. .

[0002]

2. Description of the Related Art FIG. 4 is a circuit diagram showing a configuration of a conventional AC / DC converter. In FIG. 1, reference numeral 1 denotes an AC power supply, and reference numerals 2 to 7 denote a main circuit, which includes a rectifier 2, a high-frequency removing filter 3, a DC reactor 4, a switching element 5, a diode 6, and a smoothing capacitor 7. 8 is a constant voltage control circuit, and 9 is a current tracking circuit.

Here, the output current Id of the rectifier 2 can be controlled by turning on and off the switching element 5, and this output current Id has a full-wave rectified waveform of the input voltage Vi from the AC power supply 1. If the control is performed so as to follow the reference value, the input current I becomes a sine wave with a power factor of about 1.
FIG. 5 shows the relationship among the input voltage Vi, the input current I, and the switching element drive waveform B at this time.

[0006] The current follow-up control is performed by a constant voltage control circuit 8 and a current follow-up circuit 9. Here, this current following operation will be described. First, the constant voltage control circuit 8 detects the waveform of the input voltage Vi, multiplies the signal VD obtained by full-wave rectification of the waveform by the rectifier 10, and multiplies the deviation signal Ve between the output voltage reference VLref and the output voltage VL. Output current reference Idr having a pulsating waveform similar to the full-wave rectified waveform of voltage Vi
Form ef.

The current follower circuit 9 inputs a deviation signal between the output current reference Idref and the output current Id to a hysteresis comparator 11, and turns on / off the switching element 5 by an output signal B of the hysteresis comparator 11. As a result, the output voltage VL is controlled to be constant, and the power factor of the input voltage / current is controlled to be approximately 1.

[0006]

However, in the conventional AC / DC converter, it is necessary to perform multiplication to form an output current reference Idref having a pulsating waveform similar to the full-wave rectified waveform of the input voltage Vi. To perform the multiplication, a method using an analog multiplication IC, a method using a multiplication type D / A converter, a method of performing digital calculation with a microcomputer, and the like can be considered, all of which are expensive. Unless a fairly expensive microcomputer is used, there are problems that the resolution is poor, the calculation time is long, the control is delayed, the control system becomes unstable, and the control cannot be performed well.

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and has as its object to obtain an AC / DC converter having a low power supply circuit and a good input power supply power factor. It is an object of the present invention to provide a control algorithm suitable for performing the control.

[0008]

According to a first aspect of the present invention, an AC / DC converter includes a rectifier for full-wave rectification of an AC power supply, a switching element for interrupting an output voltage of the rectifier, and a smoothing circuit for switching the voltage interrupted by the switching element. And a smoothing circuit that outputs a DC voltage to control the output voltage and the output current by controlling the driving of the switching element. The deviation is proportionally / integrally calculated, the signal obtained by the proportional / integral calculation is added to a signal obtained by multiplying the output signal of the rectifier by a preset coefficient, and the added signal is used as an output current reference signal, and the output current is It is provided with means for controlling the driving of the switching element so as to follow the output current reference signal.

An AC / DC converter according to a second aspect of the present invention provides a rectifier for full-wave rectification of an AC power supply, a switching element for interrupting an output voltage of the rectifier, and smoothing a voltage interrupted by the switching element to output a DC voltage. And an AC / DC converter that controls the output voltage and the output current by controlling the driving of the switching element.
A reference device for outputting an output voltage reference signal, and a proportional / integral calculation of a deviation between the output signal of the reference device and the output voltage signal.
A signal obtained by adding an integrator, an output signal of the proportional / integrator, and a signal obtained by multiplying the output signal of the rectifier by a preset coefficient is input as an output current reference signal, and an output current reference signal to which an output current is input. And a current tracking circuit that controls the driving of the switching element so as to follow the current.

According to a third aspect of the present invention, in the AC / DC converter according to the first or second aspect, a coefficient value obtained by multiplying an output signal of the rectifier by a coefficient is used for each of an input voltage, an output voltage, and a load connected to the output side. It is provided with means for switching step by step based on the information.

An AC / DC converter according to a fourth aspect of the present invention is a rectifier for full-wave rectifying an AC power supply, a switching element for interrupting an output voltage of the rectifier, and smoothing a voltage interrupted by the switching element to output a DC voltage. And an AC / DC converter that controls the output voltage and the output current by controlling the driving of the switching element.
A preset output voltage reference signal, output voltage signal, rectifier output signal, and output current signal are input as digital data, and a deviation between the output voltage reference signal and the output voltage signal based on the input digital data. Is proportionally / integrated, and the signal obtained by performing the proportional / integral operation is multiplied by a signal obtained by multiplying the output signal of the rectifier by a preset coefficient, and the added signal is used as an output current reference signal, and the output current signal is The microcomputer includes a microcomputer that executes a control algorithm that outputs a signal for controlling the driving of the switching element so as to follow the output current reference signal.

According to a fifth aspect of the present invention, in the AC / DC converter according to the fourth aspect, the microcomputer further comprises: an input voltage signal to the rectifier and information on a load connected to the output side are input as digital data, and The algorithm further calculates a coefficient value that multiplies the output signal of the rectifier by a factor:
The switching is set in a stepwise manner based on each information of the input voltage signal, the output voltage, and the load connected to the output side.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1 FIG. 1 is a circuit diagram showing a configuration of an AC / DC converter according to Embodiment 1 of the present invention. In the figure, 1 is an AC power supply, 2 is a rectifier, 4 is a DC reactor, 5 is a switching element, 6 is a diode,
Reference numeral 7 denotes a smoothing capacitor, and a rectifier 2, a DC reactor 4, a switching element 5, a diode 6, and a smoothing capacitor 7 constitute a main circuit. 9 is a current tracking circuit, 1
1 is a hysteresis comparator, 12 is an output voltage reference V
A reference device for outputting Lref, 13 is a proportional / integrator, 14 is an attenuator, and 15 is a current detector.

In this embodiment, the input voltage Vi
The rectifier 2 of the main circuit is used to obtain a signal VD obtained by full-wave rectification of the signal. However, the function is the same as that of the rectifier 10 of the conventional example, and the switching element 5 is turned on and off. Is the same as the conventional example in that the waveform control of the output current Id is performed.

In this embodiment, a deviation e between the output voltage reference VLref and the output voltage VL generated by the reference device 12 is applied to an offset current reference Ioref obtained through a proportional / integrator 13, and the input voltage Vi is The output current reference Idref is formed by adding a pulsating current reference Irref obtained by multiplying the full-wave rectified signal VD by a predetermined coefficient (K). Then, the current tracking circuit 9 inputs a deviation signal between the output current reference Idref and the output current Id detected by the current detector 15 to the hysteresis comparator 11, and turns on the switching element 5 by the output signal B of the hysteresis comparator 11.・ Turn off. As a result, the output voltage VL is controlled to be constant, and the power factor of the input voltage / current is controlled to be approximately 1.

Next, details of the operation of this embodiment will be described in comparison with the operation of the conventional example. First, FIG.
In the case of the conventional example shown in FIG. 2, when the amplitude and frequency of the input voltage Vi, the output voltage VL and the load impedance are constant, the deviation signal Ve between the output reference VLref and the output voltage VL is obtained.
Is constant. Therefore, the product Idref of the constant deviation signal Ve and the full-wave rectified waveform VD of the constant input voltage Vi is a similar waveform whose amplitude is Ve times the full-wave rectified waveform VD.

Therefore, by setting the gain K of the attenuator 14 shown in FIG. 1 to K = Ve, the Idref of the conventional example and the Irref which is the output of the attenuator 14 of this embodiment match. If the offset current reference Ioref, which is the output of the proportional / integrator 13, is set to Ioref = 0, then Idref
= Irref, and the current follow-up circuit 9 is the same as in the prior art, so that the output voltage VL is controlled to be constant and the power factor of the input voltage / current is controlled to approximately 1.

However, in practice, there may be variations in the input voltage Vi and individual differences and variations in the load impedance. Therefore, in this embodiment, the deviation e between the output voltage reference VLref and the output voltage VL is compensated for these disturbance factors. As an offset current reference Ioref through the proportional-integrator 13,
The compensation is made by adding the result to Irref which is the output of the attenuator 14.

By this compensation, for example, if the load impedance is different from the expected one, the input current I
Is a waveform in which a DC component whose polarity is inverted every half cycle and a sine wave are added, but the power factor is controlled to 1 with little change with a slight deviation of the load impedance.

In this embodiment, the deviation between the output voltage VL and the output voltage reference VLref is passed through a proportional / integrator to multiply the offset current reference Ioref and the input voltage Vi by a predetermined coefficient multiple of VD obtained by full-wave rectification. Since the output current reference Idref is obtained by adding the waveform, that is, the pulsating current reference Irref, a multiplier is not required, and the apparatus can be inexpensive.

Embodiment 2 FIG. In this embodiment, the constant voltage control of the output voltage VL and the power factor control of the input voltage / current in the first embodiment are digitally controlled by a microcomputer or the like. Therefore, in this embodiment, a microcomputer is provided instead of the current tracking circuit 9, the hysteresis comparator 11, the proportional / integrator 13, the attenuator 14, and each adder / subtractor in the first embodiment. Thus, a control algorithm similar to that of the first embodiment is realized.

Next, a control operation by the microcomputer of this embodiment will be described. FIG. 2 is a flowchart showing a control operation by the microcomputer of this embodiment. First, set the value of e (n-1) to 0, Ior
The value of efI (n-1) is set to 0, and the value of B is set to OFF (S10
0). Here, (n-) of e (n-1) and IorefI (n-1)
1) indicates the value immediately before each value, and e is
A variable to which a deviation between the output voltage reference VLref and the output voltage VL is input, IorefI is a variable used for proportional / integral calculation, and B is a variable indicating a control state of the switching element.

The output reference VLref, the output voltage VL,
The full-wave rectified waveform VD and the output current Id
Through a digital converter or the like, each variable VLref,
VL, VD and Id are input (S101). The output reference VLref may be set in advance as output reference data. Then, e is VLref-VL.
Is substituted (S102), and the value of KP × e is substituted for IorefP (S103). Here, IorefP is a variable used for proportional / integral calculation, and KP is a predetermined coefficient used for proportional / integral calculation.

Then, IorefI is given by KI × ((e + e (n−
1)) / 2) Substituting the value of + IorefI (n-1) (S104),
The current value of e and the value of IorefI are substituted for e (n-1) and IorefI (n-1), respectively (S105), and Ioref is substituted for Ioref.
The value of efP + IorefI is substituted (S106). Here, Ioref is a variable to which the same value as the offset current reference Ioref, which is the output signal of the proportional / integrator 13 of the first embodiment, is input, that is, the proportional / integral of the first embodiment. The arithmetic processing in the unit 13 is performed by the operations of S103 to S106.

Then, the value of K × VD is substituted for Irref (S107). Here, Irref is a variable to which the same value as Irref which is the output signal of the attenuator 14 of the first embodiment is input, and K is a gain as a gain used in the attenuator 14 of the first embodiment. The same coefficient as the predetermined coefficient K,
The arithmetic processing in the attenuator 14 according to the first embodiment is performed by the operation of S107.

Then, the value of Ioref + Irref is substituted for Idref (S108). Here, Idref is the output current reference I input to the current follower circuit 9 of the first embodiment.
The same value as the value of dref is the input variable.

Then, the value of Idref-Id is substituted for a (S109). Here, a is a variable used for controlling the switching element. And the value of B is
It is determined whether the value is OFF (S110). If the value of B is determined to be OFF in S110, it is determined whether a> d is satisfied (S111), and the value of B is determined to be OFF in S110.
If not, it is determined whether or not a <−d (S112). Here, d is a coefficient having a value of the hysteresis width used in the hysteresis comparator 11 of the first embodiment.

If it is determined in S111 that a> d, or if it is not a <-d in S112, the value of ON is substituted for B (S113), and a> d is determined in S111. Is not determined, or a <−d in S112.
Is determined, the value of OFF is substituted for B (S
114), outputting the value of B, and based on the value of B,
The switching element is controlled (S115), and the process returns to S101. The operations in S109 to S114 are the same as those in the first embodiment.
This corresponds to the control algorithm in the current follow-up circuit 9.

By repeating the above operation, a control algorithm similar to that of the first embodiment is realized. As in the first embodiment, the output voltage VL is controlled to be constant and the power factor of the input voltage / current is reduced. It will be controlled to almost 1.

In the control algorithm as shown in FIG. 2, there are multiplication terms in the processing in S103, S104 and S107, but since KP, KI and K are all predetermined coefficients, the variable ( e, e + e (n-1), VD)
Can be calculated in a short period of time by shifting and adding, so that the calculation time does not become long and control is not delayed.

In this embodiment, since the control algorithm in the first embodiment is digitally controlled by using a microcomputer, high-precision and stable control can be performed at low cost.

Embodiment 3 FIG. This embodiment is different from the first embodiment in that the gain K used in the attenuator 14 is
The switching is performed stepwise using a resistor. FIG. 3 is a circuit diagram showing a configuration of an AC / DC converter according to Embodiment 3 of the present invention. In the figure, 1 is an AC power supply,
Reference numeral 2 denotes a rectifier, 4 denotes a DC reactor, 5 denotes a switching element, 6 denotes a diode, and 7 denotes a smoothing capacitor. The rectifier 2, DC reactor 4, switching element 5, diode 6, and smoothing capacitor 7 constitute a main circuit. .
9 is a current tracking circuit, 11 is a hysteresis comparator,
Reference numeral 12 denotes a reference unit for outputting an output voltage reference VLref, reference numeral 13 denotes a proportional / integrator, reference numeral 15 denotes a current detector, and reference numerals 16 to 18 denote resistors having resistance values of R1, R2, and R3, respectively. 19 is a switch for switching the gain K.

First, when the input voltage, the output voltage, or the load is switched stepwise, the gain K of the attenuator 14 in the first embodiment is switched stepwise so that the input power factor is infinite under each condition. 1 can be approached. Therefore, in this embodiment, the attenuator 14 in the first embodiment is configured by using the resistors 16 to 18 and the switch 19, and the gain K is determined by the voltage dividing ratio of the resistance values R1 to R3 of the resistors 16 to 18. That is, K = (R1 + R2)
/ (R1 + R2 + R3). By opening and closing the switch 19, the resistance value R2 of the resistor 17 becomes 0 or R2, and the gain K can be switched.

The operation after the gain K of the attenuator 14 is determined by switching with the resistors 16 to 18 and the switch 19 is the same as that of the first embodiment.

In this embodiment, three resistors and
Although the attenuator 14 is constituted by one switch, the present invention is not limited to this, and a plurality of levels of gain may be set using a plurality of resistors and a plurality of switches. The configuration of the attenuator 14 is not limited to a resistor and a switch, but may be another configuration as long as the signal VD obtained by full-wave rectifying the input voltage Vi can be multiplied by a predetermined coefficient (K).

In this embodiment, the gain K used in the attenuator 14 is switched stepwise by using a resistor. Therefore, even when the input voltage, the output voltage, and the load are switched stepwise, And the gain K, it is possible to make the input power factor almost equal to 1 at low cost.

Embodiment 4 FIG. In this embodiment, in the second embodiment, the value of the predetermined coefficient K in the process of substituting the value of K × VD for Irref in S107 is determined by the resistors 16 to 18 and the switch 19 of the third embodiment. Similar to the switching, the switching is performed stepwise. This switching of the gain K is performed digitally by a microcomputer or the like as in the second embodiment, so that the switching can be performed without adding a component.
7 can be easily performed by changing the number or order of shifting or adding VD.

In this embodiment, the value corresponding to the gain K of the attenuator 14 can be freely changed by setting the predetermined coefficient K, so that a plurality of resistors and a plurality of switches are used. Instead, the value of the gain K based on the combination of the input voltage, the output voltage and the load value is determined in advance, and if that value is stored, the input voltage, the output voltage and the load Can be easily handled.

Further, the values of the input voltage, the output voltage and the load are detected, the values are inputted, and the optimum gain K is selected based on the inputted input voltage, the output voltage and the load.
The gain K may be set. in this case,
When the input voltage, the output voltage, or the load is switched stepwise, the optimum gain K can be automatically set.

In this embodiment, the switching of the gain K is digitally controlled using a microcomputer. Therefore, even when the input voltage, the output voltage, and the load are switched stepwise, the gain K can be switched. Accordingly, the input power factor can be made approximately 1, and furthermore, highly accurate and stable control can be performed at low cost.

[0041]

As described above, according to the first aspect, the deviation between the preset output voltage reference signal and the output voltage signal is proportionally / integrally calculated, and the proportionally / integrally calculated signal and the rectifier are calculated. And a signal obtained by multiplying the output signal of the switching element by a preset coefficient, and using the added signal as an output current reference signal to control the driving of the switching element so that the output current follows the output current reference signal. Therefore, when obtaining the output current reference signal, a multiplier is not required, and the apparatus can be inexpensively manufactured.

According to the second invention, the output voltage reference signal is output by the reference device, and the deviation between the output signal of the reference device and the output voltage signal is calculated by the proportional / integrator in a proportional / integral manner.
A signal obtained by adding the output signal of the proportional / integrator and the signal obtained by multiplying the output signal of the rectifier by a preset coefficient is output by the current follower circuit input as the output current reference signal. Since the driving of the switching element is controlled so as to follow the signal, a multiplier is not required when the output current reference signal is obtained, so that the device can be made inexpensive.

According to a third aspect, in the first or second aspect, the coefficient value for multiplying the output signal of the rectifier by a coefficient is determined based on each information of the input voltage, the output voltage, and the load connected to the output side. Thus, since the switching is performed stepwise, even when the input voltage, the output voltage, and the load are switched stepwise, it is possible to reduce the input power factor to approximately 1 by changing the coefficient, thereby reducing the cost. Have.

According to the fourth aspect of the present invention, a microcomputer to which a preset output voltage reference signal, output voltage signal, rectifier output signal and output current signal are input as digital data is used to input each digital data. , A proportional / integral operation is performed on a deviation between the output voltage reference signal and the output voltage signal, and a signal obtained by multiplying the proportional / integral operation signal and a rectifier output signal by a preset coefficient is added. The added signal is used as an output current reference signal, and a control algorithm for outputting a signal for controlling the driving of the switching element so that the output current signal follows the output current reference signal is executed. This has the effect that control can be inexpensive.

According to a fifth aspect, in the fourth aspect, the microcomputer further receives, as digital data, an input voltage signal to the rectifier and information on a load connected to the output side, and the control algorithm includes: further,
Since the coefficient value for multiplying the output signal of the rectifier by a factor is set in a stepwise manner based on the input voltage signal, the output voltage, and each information of the load connected to the output side,
Even when the input voltage, the output voltage, and the load are switched step by step, the input power factor can be made approximately 1 by switching the coefficients, and furthermore, high-precision and stable control can be performed at low cost. It has the effect of.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an AC / DC converter according to Embodiment 1 of the present invention.

FIG. 2 is a flowchart showing a control operation by a microcomputer according to the second embodiment.

FIG. 3 is a circuit diagram showing a configuration of an AC / DC converter according to Embodiment 3 of the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional AC / DC converter.

FIG. 5 is a waveform diagram showing a relationship among an input voltage Vi, an input current I, and a switching element drive waveform B.

[Explanation of symbols]

1 AC power supply, 2 rectifier, 4 DC reactor, 5
Switching element, 6 diode, 7 smoothing capacitor, 9 current follower circuit, 13 proportional / integrator, 14 attenuator, 15 current detector, 16-18 resistor, 19 switch.

Claims (5)

[Claims] A rectifier for full-wave rectifying an AC power supply, a switching element for interrupting an output voltage of the rectifier, and a smoothing circuit for smoothing a voltage interrupted by the switching element and outputting a DC voltage. An AC / DC converter for controlling the output voltage and the output current by controlling the driving of the switching element, wherein a deviation between a preset output voltage reference signal and the output voltage signal is proportionally / integrated, and the proportional / integral operation is performed. An integrated signal and a signal obtained by multiplying the output signal of the rectifier by a preset coefficient are added, and the added signal is used as an output current reference signal, so that the output current follows the output current reference signal. An AC / DC converter further comprising means for controlling the driving of the switching element. 2. A rectifier for full-wave rectification of an AC power supply, a switching element for interrupting an output voltage of the rectifier, and a smoothing circuit for smoothing a voltage interrupted by the switching element and outputting a DC voltage. An AC / DC converter that controls an output voltage and an output current by controlling driving of the switching element; and a reference device that outputs an output voltage reference signal; and a deviation between the output signal of the reference device and the output voltage signal. A proportional / integrator for performing a proportional / integral operation; and a signal obtained by adding an output signal of the proportional / integrator and a signal obtained by multiplying an output signal of the rectifier by a preset coefficient, are input as an output current reference signal, and And a current tracking circuit for controlling the driving of the switching element so that the output current follows the input output current reference signal. apparatus. 3. A device for switching a coefficient value for multiplying an output signal of the rectifier by a factor based on information of an input voltage, an output voltage, and a load connected to an output side. An AC-DC converter according to claim 1. 4. A rectifier for full-wave rectification of an AC power supply, a switching element for interrupting an output voltage of the rectifier, and a smoothing circuit for smoothing a voltage interrupted by the switching element and outputting a DC voltage. An AC / DC converter that controls an output voltage and an output current by controlling the driving of the switching element, wherein a preset output voltage reference signal, an output voltage signal, and an output signal and an output current signal of the rectifier are digital data. Based on each of the inputted digital data, a deviation between the output voltage reference signal and the output voltage signal is proportionally / integrally calculated, and the proportionally / integrally calculated signal and the output signal of the rectifier are previously calculated. The output current signal is added to the signal multiplied by the set coefficient, and the added signal is used as an output current reference signal. AC-DC conversion device characterized by comprising a microcomputer that executes a control algorithm for outputting a signal for controlling the driving of the switching element so as to follow the serial output current reference signal. 5. The microcomputer further comprises:
An input voltage signal to the rectifier and information on a load connected to an output side are input as digital data.The control algorithm further includes a coefficient value for multiplying an output signal of the rectifier by an input voltage signal, an output voltage. 5. The AC / DC converter according to claim 4, wherein the setting is performed by switching stepwise based on each information of the load connected to the output side.