JP2002010632A - Ac/dc converter and dc-dc converter - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an AC/DC converter having a voltage step-up chopper circuit which avoids loss during the recovery period of the voltage step-up chopper and maintains its AC input waveform in sinusoidal wave. SOLUTION: A full wave rectified current is obtained by connecting an AC power source 9 to an input rectifier 2 through a high frequency filter 1. This wave is connected to a first voltage step-up chopper circuit which consists of a voltage step-up choke reactor 3, a voltage step-up diode 4 and a switching element 5 and a second voltage step-up chopper circuit which consists of a voltage step-up choke reactor 13, a voltage step-up diode 14 and a switching element 15. The switching elements 5 and 15 are switching-driven by a high frequency wave by shifting each phase to the other by 180 degrees. Two groups of outputs of the voltage step-up chopper are jointed and connected to a capacitor 7 for smoothing and in parallel transmitted to output terminals 10, 11. The current i3 of the voltage step-up choke reactor 3 and the current i13 of the voltage step-up choke reactor 13 are selected respectively to a value which makes it zero at every switching period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to an AC / DC converter and a DC-DC converter,
Particularly, an AC / DC converter that operates efficiently and a DC-DC converter that operates efficiently while keeping the input current waveform in a sine wave shape.
It relates to a DC converter.

[0002]

2. Description of the Related Art In an AC / DC converter, as a circuit that operates efficiently while maintaining an input current waveform in a sine wave shape, a system including a boost chopper circuit that switches at a frequency sufficiently higher than the frequency of input AC is known. ing. For example, in 1989 ARPRASAD and PDZIOGAS
IEEE POWERELECTRONICS SPEC by three members of S.MANIAS
The theme "AN ACTIV" presented at the IALISTS CONFERENCE
EPOWER FACTOR CORRECTION TECHNIQUE FOR THREE-PHASE
DIODE RECTIFIERS ”(active power factor correction technology for three-phase diode rectifiers).
8-65. Regarding the configuration of the three-phase boost chopper circuit, a configuration is provided in which an independent boost chopper circuit is provided for each phase and the output side is connected to charge one smoothing capacitor. And a circuit for arranging a boost choke for each AC phase. In each case, in order to keep the power factor good, one or both of the instantaneous value of the input current and the instantaneous value of the input voltage are detected and operated by the feedback circuit. In addition, the above conference papers include
In addition, four papers are cited as references. That is, the first reference: S. Manlas, ARPrasad, and PD
Zlogas, "Three-phase inductor fed SMRconverer with
high frequencty isolaion high power density and im
provedpower factor ", IEEE proceedings, Vol.134, p
tB, No.4, July 1987, pp.183-191 "Three-phase, inductor-supplied SMR converter with high-frequency isolation, high power density, and improved power factor" Reference 2: MJKocher RLSteigerwald "An AC to
DC converter with high qualityinput waveforms ", I
EEE Trans. Ind. Appl., Vol. IA-19 No.4, July / Aug.1
983 pp.586-599 "High-quality converter of input waveform" 3rd reference: WP Marple, "Low distortion three-ph
ase power regulator ", IBM technicaldisclosure bull
etin, Vol.22, No.3, Aug.1979, pp.970-971 "Low Distortion Three-Phase Power Ballast" 4th reference: Dan Gauger et al, "A three-phase off
line switching power supply withunity power factor
and low TIF ", in Conf. Rec. 1986 IEEE INTELEC, p
p.115-121 “Three-Phase Off-Line Switching Power Supply, High Power Factor, Low TIF” As described above, various proposals have been made for power factor correction circuits since a long time ago.

[0003] A relatively recent one is disclosed in, for example, Japanese Patent Application Laid-Open No. 11-356039. That is, a method for suppressing an undesired response of a current waveform when supplying a current from a main power supply to a load via a rectifier, wherein power factor correction for pulse width modulation of a switch signal affecting a main current input of a boost converter. In an active filter for filtering using a circuit, a current path between a rectifier and a load is divided into a plurality of parallel current paths, and each of these current paths is provided with an active filter of the same type, and their switch signals are provided. Are different from each other, and these signals are the same pulse width modulation signals. By superimposing the currents of the individual current paths additively, the ripple current is reduced at the main current input. Active filters are shown.

[0004] The text described in Japanese Patent Application Laid-Open No. 11-356039 is a translation of the original application from German, and its translation and interpretation are often considered to be inappropriate or incorrect. is there. For example, paragraph 00 of the publication
11, 0013, 0022, the unrealistic speech method of the connection method / expression in German grammar is not properly interpreted. For example, paragraph 0011 of the publication, more correctly,
<< At first glance, it seems that increasing the number of current paths of the boost converter increases the construction cost. For example, if the number of current paths is two, the cost appears to be doubled. But it is not. This will be described in detail in the following description of an embodiment with reference to the drawings. >> It should be interpreted as. It is considered to be a way of talking that highlights the process of thinking of the inventor until the invention is completed or the truth of the problem. In FIG. 3, which is a brief description of the drawings at the end of the publication, there is a dropout such as comprehension of the syntax, and more correctly, FIG. 3 is a principle circuit diagram for reconstructing the falling edge, The falling edge of the corresponding measured proportional value of the current flowing through the boost choke coil of the circuit of FIG. 1 is processed. >> It should be interpreted as. The sentence at the end of paragraph 0024 of the publication has an error or the like, and more correctly, << ... the reason is that only the average value of the current is involved in the attached current regulating circuit on the one hand, and Because the voltage control circuit of the associated connecting circuit completely controls the possible deviations. The forced synchronization of the voltage across capacitor C1 to the shunt voltage occurs at the next re-switch-on. >> It should be interpreted as. Inappropriate examples of the translation include claim 7, paragraph 0012, and paragraph 002 of the same gazette.
The “intermediate circuit” described in 4 is to be interpreted as a “connection circuit” in light of the original meaning. zwischen is "middle"
According to the German-German dictionary, it indicates not only spatial and temporal intermediateness but also the relationship between two things, for example, Zwischenglied as a "link". A description can be found. The dictionaries that were referred to are Sagara Moramine, the German-Japanese Dictionary and L. DeVries
, TMHerrmann ed.German-English Technical andEng
It is an ineering dictionary (German-English dictionary for science and technology).
The Applicant has carefully interpreted the original German statement in its entirety, and the above is only one example.

In a boost chopper circuit to which a commercial AC power source is input, the breakdown voltage of the boost diode needs to be several hundred volts or more. As a diode with this withstand voltage, no matter how fast recovery,
It requires a current for recovering the accumulated charge during the period when the forward current is flowing. The major problems are the power loss of the diode itself required for the recovery and the power loss caused by flowing the current through the switching element. In conventional circuits, this problem has not been discussed, and no improved example has been found.

[0006]

SUMMARY OF THE INVENTION The present invention avoids the loss of the recovery period of a boost diode in an AC / DC converter using a boost chopper circuit.
It is an object of the present invention to obtain a circuit capable of maintaining a good input current waveform and power factor.

[0007]

Means for Solving the Problems In order to solve this problem, the present invention proposes the following means.
That is, A which receives AC power and outputs DC power
A C / DC converter, a rectifier, a plurality of boost chopper circuits connected in parallel to the rectifier, each of which includes a boost choke, a boost diode, and a switching element; and outputs of the plurality of boost chopper circuits. A smoothing capacitor connected to the smoothing capacitor, an output terminal and a voltage detector connected in parallel to the smoothing capacitor,
A control circuit for driving control terminals of respective switching elements of the plurality of step-up chopper circuits, wherein the respective switching elements are phase-shifted from each other by an equal angle, pulse width modulation controlled at the same fixed frequency, and the step-up is performed. With respect to the inductance value of the choke or the switching frequency, the inductance of the boost choke is such that the current once becomes zero for each switching cycle of the switching element with respect to the entire variation range of the input AC voltage and the entire variation range of the load power. An AC / DC converter characterized by being set to a value or a frequency is proposed. In this AC / DC converter, since the current of the boost diode starts from zero in each cycle of the switching frequency, it is possible to prevent a loss related to recovery.

Further, as a second means, it is proposed that the period during which the current of the boosting choke is zero is equal to or longer than the reverse recovery time of the boosting diode.

As a third means, it is proposed to set the response speed of the pulse width modulation control to a time sufficiently longer than the period of the input AC frequency. By this means, the pulse width is modulated to a substantially constant pulse width within one cycle of the input AC frequency, and the power factor can be maintained at a desired value.

In the above-mentioned first means, the rectifier can be omitted and configured as a DC input to operate as a DC-DC converter. In such a case, the loss of the recovery period can be avoided by setting the period during which the current of the boost choke is zero value to be equal to or longer than the reverse recovery time of the boost diode.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows an AC / D according to the present invention.
It is an example of an embodiment of a C converter, and is a principle circuit diagram thereof. A commercial AC power supply 9 is connected to the input rectifier 2 via the high frequency filter 1 to perform full-wave rectification. This full-wave rectified waveform is connected to two sets of boost chopper circuits.
That is, a first boost chopper circuit including the boost choke 3, the boost diode 4 and the switching element 5, and a second boost chopper circuit including the boost choke 13, the boost diode 14 and the switching element 15, Is connected in parallel to the output of The outputs of the boost diode 4 and the boost diode 14 are connected to each other and connected to the capacitor 7. Both ends of this capacitor 7 are connected to a voltage detector 16 and output terminals 10, 1
1 and connected to the load 20. The switching element 5 and the switching element 15 are driven by the control circuit 8 to perform high-frequency switching at a frequency sufficiently higher than the frequency of the commercial AC power supply 9.

The control circuit 8 is well known,
An integrated circuit for driving a switching power supply can be used. The control circuit 8 includes a reference voltage circuit, an error amplifier,
A reference high-frequency oscillator, a circuit that performs pulse width modulation by a comparator based on the output signal level of the error amplifier and the reference high-frequency oscillator, and a drive circuit that processes the pulse output into a predetermined signal form. A resistor terminal RT of an external component that determines the oscillation cycle of
Capacitor terminal CT, drive signal output terminal OUT1, second output terminal OUT2 whose phase is different by 180 ° from this terminal, reference voltage circuit terminal ref., Error amplifier non-inverting input terminal
There are terminals such as AMP +, inverting input terminal AMP- and its output terminal AMPOUT, and a common ground terminal GND. A resistor 81 is connected between the resistance terminal RT and the terminal GND of the reference high-frequency oscillator, and a capacitor 82 is connected between the capacitor terminal CT and the terminal GND. The reference voltage generated at the terminal ref. Of the reference voltage circuit is connected via a resistor 84 to the non-inverting input terminal AMP + of the error amplifier. The detection signal from the voltage detector 16 is connected to the inverting input terminal AMP- via the resistor 89. At the same time, the inverting input terminal AMP- and its output terminal AMPOUT
And a series circuit of a capacitor 85, a resistor 86, a resistor 88, and a capacitor 87, which are circuit constants for negative feedback.

Assuming that the resistance value of the resistor 81 is RT and the capacitance value of the capacitor 82 is CT, the oscillation frequency f is given by, for example, the following equation.

F = 1.1 / RT · CT...

As an example, when substituting RT = 7.9 kOhms and CT = 1000 picofarads into the equation, the calculation results in f = 140 kHz.

Assuming that the resistance value of the resistor 89 is Z1 and the impedance value of a network formed by the resistors 86 and 88 and the capacitors 85 and 87 is Z2, the gain G of the error amplifier in the control circuit 8 is Is represented by the following equation.

G = Z2 / Z1 ...

As an example, Z1 = 2.2 kOhm,
As a component of Z2, the resistor 86 is 100 kΩ, the resistor 88 is 100 ohm, the capacitor 85 is 1 microfarad, the capacitor 87 is 0.1 microfarad, and the frequency at which the total gain is zero decibel is about 50 Hz. Was. The reactance of the capacitor is calculated by the formula of 1 / 2π · (frequency) · (capacitance).
Calculate the gain G.

A detection signal from the voltage detector 16 is received and compared with an internal reference power supply, and a pulse width modulated drive signal is generated so that the voltage value of the output terminals 10 and 11 becomes a predetermined value.

In the AC / DC converter having this configuration, as the operation mode, each switching element is operated with a phase shifted from each other by 180 °, and only the pulse width modulation control for keeping the output voltage constant at the same fixed frequency is performed. The switching drive is performed, and the response speed of the pulse width modulation control is set to a time sufficiently longer than the cycle of the input AC frequency (for example, 5 Hz or less for 50 Hz). In addition, as for the inductance values of the boost chokes 3 and 13, the current of the boost choke becomes zero once every switching cycle of the switching element in the entire fluctuation range of the input AC voltage and the whole fluctuation range of the load power. Design for inductance.

In the waveform diagram of FIG. 2, the abscissa indicates the passage of time, and the ordinate indicates the current waveform of each part of the circuit shown in FIG. That is, in order from the top of the vertical axis,
i3 indicates the current waveform of the boost choke 3, i13 indicates the current waveform of the boost choke 13, i2 indicates the output current waveform of the input rectifier 2, i5 indicates the current waveform of the switching element 5, and i15 indicates the current waveform of the switching element 15. Shows the current waveform of i4
Represents the current waveform of the boost diode 4, and i14 represents the current waveform of the boost diode 14.

At time t0, the switching element 5 is turned on, and the current i5 of the switching element 5 increases linearly from the zero value. At the same time, the current i3 of the boost choke 3 also increases linearly from the zero value.

At time t1, when the switching element 5 is driven off, the current i5 of the switching element 5 quickly becomes zero. At this time, the energy stored in the boost choke 3 supplies power to the load 20 through the boost diode 4. The current i3 of the boost choke 3 also decreases from the peak value at a slope corresponding to the value of the difference between the input voltage and the output voltage.

At time t2, the current i13 of the boost choke 13 and the current of the
i14 decreases to zero. Time after this time t2
The section up to t3 is a so-called dead time for keeping the current i13 of the boost choke 13 at zero.

At time t3, the switching element 15
Is turned on, the current i15 of the switching element 5 increases linearly from the zero value. Boost choke 1 at the same time
The current i13 of No. 3 also increases linearly from the zero value.

At time t4, switching element 15
Is turned off, the current i15 of the switching element 15 quickly becomes zero. At this time, the energy stored in the boost choke 13 supplies power to the load 20 through the boost diode 14. The current i13 of the boost choke 13 also decreases from the peak value at a slope corresponding to the value of the difference between the input voltage and the output voltage.

At time t5, the current of the boost choke 3
i3 and the current i4 of the boost diode 4 become zero while decreasing. The section from time t5 to time t6 is a dead time for keeping the current i3 of the boost choke 3 at zero.

At time t6, the switching element 5 is turned on, and the current i5 of the switching element 5 increases linearly from the zero value. At the same time, the current i3 of the boost choke 3 also increases linearly from the zero value.

At time t7, when the switching element 5 is driven off, the current i5 of the switching element 5 quickly becomes zero. At this time, the energy stored in the boost choke 3 supplies power to the load 20 through the boost diode 4. The current i3 of the boost choke 3 also decreases from the peak value at a slope corresponding to the value of the difference between the input voltage and the output voltage.

At time t8, the current i13 of the boost choke 13 and the current i14 of the boost diode 14 decrease to zero. The section from time t8 to time t9 is a dead time for keeping the current i13 of the boost choke 13 at zero.

At time t9, the switching element 1
5 is turned on, and the current i15 of the switching element 5 increases linearly from the zero value. At the same time, the current i13 of the boost choke 13 also increases linearly from the zero value.

At time t10, the switching element 1
5 is turned off, the current i15 of the switching element 15
Quickly becomes zero. At this time, the energy stored in the boost choke 13 supplies power to the load 20 through the boost diode 14. The current i13 of the boost choke 13 also decreases from the peak value at a slope corresponding to the value of the difference between the input voltage and the output voltage.

At time t11, the current i3 of the boost choke 3 and the current i4 of the boost diode 4 decrease to zero. A section from the time t11 to the start time t0 of the next cycle is a dead time for keeping the current i3 of the boost choke 3 at zero.

Here, the zero value period of the current i3, the section from time t5 to t6, or the section from time t11 to t0 has a length equal to or longer than the reverse recovery time of the boost diode 4, and During the period in which i13 is zero, the section from time t2 to t3 or the section from time t8 to t9 is the boost diode 1
The length is equal to or longer than the reverse recovery time of No. 4. As a result, after the current flowing through the boost diode 4 or 14 becomes zero, the switching elements 5 and 15 are turned on in a state where their reverse characteristics have been recovered, so that the loss at the time of reverse recovery of the boost diodes 4 and 14 is reduced. Can be zero.

With respect to the inductance value of the step-up choke or the switching frequency, the current of the step-up choke becomes zero once every switching cycle of the switching element for the entire fluctuation range of the input AC voltage and the whole fluctuation range of the load power. In order to satisfy the main condition of the means of the present invention of setting the inductance value or the frequency to be a value, for example, in the waveform diagram of the current i3 in FIG. 2, the rise of the waveform of the current i3 from time t0 to time t1 The main condition of the means of the present invention can be satisfied by determining the slope by selecting the inductance value and determining the switching period by the equation.

In order to satisfy the condition that the response speed of the pulse width modulation control is set to a time sufficiently longer than the cycle of the input AC frequency, the values of the resistors 86, 88, 89 in the circuit diagram shown in FIG. The gain can be calculated from the values of the capacitors 85 and 87 and the frequency dependency to satisfy the predetermined condition.

FIG. 3 shows a waveform diagram of the current i 2 in FIG. 2 over a half cycle of the input AC frequency on the time axis. Note that the time axis on the horizontal axis is a conceptual illustration considerably exaggerated as compared with the actual high frequency. As shown in this diagram, the input current is full-wave rectified current i2
Is substantially equal to the sine waveform of the AC input current in the AC input half cycle. As shown in the lower part of the horizontal axis of FIG. 3, the ON period of the current i5 of the switching element 5 and the current i15 of the switching element 15 has a constant width, and the current i4 of the boosting diode 4 and the current i14 of the boosting diode 14 The ON interval of is a variable width corresponding to the magnitude of the instantaneous value of the input AC voltage.

When the AC / DC converter of the present invention is operated in an actual circuit, the measured values are AC input 100 V,
50 Hz, switching frequency 140 kHz, output voltage 375.9 V, output 485 W, power factor 0.99
3. The efficiency was 93%. When the AC input voltage is increased to 200 V AC in this state, the switching frequency is the same at 140 kHz, the output voltage is 383.4 V, the output is 486 W, the power factor is 0.963, and the efficiency is 96%. Although this characteristic is inferior to the characteristics of an active filter using a power factor correction circuit, for example, IEC1000-3-
This is a range of good characteristics that meet the standards of No. 2 and are practical.

Although the AC / DC converter according to the present invention described above is a circuit including two sets of boost chopper circuits, a circuit including three or more sets of boost chopper circuits may be used as necessary. You can also. Further, by partially providing a plurality of internal circuits of the control circuit, an operation mode in which the duty ratio of the switching element exceeds 50% can be achieved.

[0040]

As described above, according to the present invention, in an AC / DC converter using a plurality of boost chopper circuits, each boost chopper circuit avoids the loss of the recovery period of the boost diode in the intermittent current mode. In addition, the circuit as a whole has a function of keeping the AC input waveform sinusoidal in the continuous current mode, and has an effect of increasing the power factor. The means of the present invention does not require the configuration of a conventional active filter, that is, a complicated device that detects an instantaneous voltage or an instantaneous current and forms a closed loop, and is a program in a range corresponding to a predetermined input / output condition. It is enough to have a set value and it is extremely economical and stable. Further, even in a DC-DC converter having a DC input, loss of the recovery period of the boost diode can be avoided. Further, since a plurality of step-up chopper circuits are provided, there is a possibility that design conditions for improving the utilization rate of main circuit components such as switching elements can be achieved.

[Brief description of the drawings]

FIG. 1 shows an embodiment of an AC / DC converter according to the present invention.

FIG. 2 shows a waveform of a current of each part of the circuit shown in FIG.

FIG. 3 is a waveform diagram of a current i2 in FIG. 2 displayed on a time axis over a half cycle of an input AC frequency.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... High frequency filter 2 ... Input rectifier 3 ... Boost choke 4 ... Boost diode 5 ...
Switching element 7 ... Capacitor 8 ... Control circuit 9 ... Commercial AC power supply 10, 11 ... Output terminal 13 ... Boost choke 14 ... Boost diode 15
... Switching element 16 ... Voltage detector 20 ... Load

Claims (5)

[Claims] 1. An AC / DC converter that receives AC power and outputs DC power, comprising: a rectifier; and a plurality of boost chopper circuits connected in parallel to the rectifier. A step-up chopper circuit comprising an element, a smoothing capacitor connected and connected to the outputs of the plurality of step-up chopper circuits, an output terminal and a voltage detector connected in parallel to the smoothing capacitor, and a respective one of the plurality of step-up chopper circuits. A control circuit for driving a control terminal of a switching element, wherein each of the switching elements is phase-shifted from each other by an equal angle, and pulse width modulation is controlled at the same fixed frequency, and the inductance value of the boost choke or the switching frequency Is for the entire range of fluctuations of the input AC voltage and the load power. AC / DC converter and a current of the boost choke is set to an inductance value or the frequency zero value once current for each switching cycle of the switching element. 2. The AC / DC converter according to claim 1, wherein a period during which the current of the boost choke is zero is equal to or longer than a reverse recovery time of the boost diode. AC / DC converter. 3. The AC / D according to claim 1 or claim 2.
In the C / C converter, the response speed of the pulse width modulation control is set to a time sufficiently longer than the cycle of the input AC frequency. 4. A DC-DC converter for receiving a DC voltage at an input terminal and outputting a DC power of an arbitrary value, comprising a plurality of boost chopper circuits connected in parallel to the input terminal. A boost chopper circuit including a boost choke, a boost diode, and a switching element;
A smoothing capacitor connected to the outputs of the plurality of boost chopper circuits, an output terminal and a voltage detector connected in parallel to the smoothing capacitors, and a control for driving control terminals of respective switching elements of the plurality of boost chopper circuits. The switching elements are controlled by pulse width modulation at the same fixed frequency with their phases shifted from each other by the same angle, and for the inductance value of the boost choke or the switching frequency, the entire fluctuation range of the input DC voltage A DC-DC converter characterized in that the current of the step-up choke is set to an inductance value or a frequency at which the current once becomes a zero value for each switching cycle of the switching element over the entire fluctuation range of the load power. 5. The DC-DC converter according to claim 4, wherein a period during which the current of the boost choke is zero is equal to or longer than a reverse recovery time of the boost diode. DC-DC converter.