JPS60190162A - Chopper controller - Google Patents

Abstract

PURPOSE:To reduce the output ripple by setting the period of a chopper to 1/2 or lower of the period of a single-phase full-wave rectified power source. CONSTITUTION:An AC single-phase power source 1 is single-phase full-wave rectified by a single-phase full-wave rectifier 10, and applied to a transistor 13. The transistor 13 is operated by a chopping period of 1/2 or lower of the period of the power source by a control unit 20 for forming ON/OFF command 3 in accordance with a control input 4. A flywheel diode 12 operates to prevent an overcurrent from generating due to a loop current from an inductance 90 when the transistor 13 is turned OFF.

Description

[Detailed description of the invention] [Field of application of the invention] The present invention is applicable to intanal windings, such as field windings.

The present invention relates to a chopper control device suitable for controlling current in a circuit with a large current, and particularly to a chopper control device suitable for controlling current in a DC machine.

[Background of the invention]

Prior art chopper collaterals are of the smoothing capacitor type. As shown in FIG. 1, this device combines a single-phase full-wave rectifier circuit and a smoothing capacitor, and chops the output using a transistor.

FIG. 1 will be explained. FIG. 2 is a time chart of FIG. 1.

The AC single-phase power supply 1 is full-wave rectified by a single-phase full-wave rectifier 10,
Further, it is smoothed by a smoothing condenser l1 to obtain a DC output. This state is shown in the upper and middle portions of the time chart in FIG. The chopper period of the transistor 13 (see the lower part of FIG. 2) can be arbitrarily selected, but is generally selected to be about twice the power supply frequency (ie, the frequency of full-wave rectification).

The chopper control device 20 selected to have such a chopper frequency adjusts the on/off ratio of the transistor 130 to control the DC current flowing through the inductance 90 (the shaded area in the middle of FIG. 2).

Note that the diode 12 is a flywheel diode, and when the transistor 13 is off, the inductance 9
It works to prevent excessive voltage from occurring due to loop current flowing from zero.

The disadvantages of this circuit are as follows.

(1) Smoothing capacitor 11 is required. Smoothing capacitors are not expensive and have a long lifespan (
5 to 10 years depending on how it is used), and the exchange methods and procedures are not easy.

(2) The smoothing capacitor 11 causes a large rush current to flow from the AC power supply 1 to the power supply layer. Inrush current may damage the rectifier diode, so the diode of the full-wave rectifier 10 and the smoothing capacitor 11
It is necessary to insert a limiting resistor between the This insertion resistance not only results in power loss, but also increases wiring man-hours and increases the voltage of the device. Note that if an inductance is used in place of the limiting resistor, loss will be eliminated, but the cost will be higher than in the case of a resistor.

[Purpose of the invention]

An object of the present invention is to provide a chopper control system that can eliminate the various drawbacks associated with the smoothing capacitor mentioned above and can perform good control of field S current.

[Summary of the invention]

In order to achieve the above object, the present invention provides a switching period of a switching element connected in series with a full-wave rectified output in series with an intuffance and/or a resistance as a load, such that the switching period of the switching element is The feature is that it is set to 1/2 or less of the period.

[Embodiments of the invention]

The present invention will be described in detail below with reference to the drawings.

FIG. 3 is a block diagram of one embodiment of the present invention.

The AC single-phase power supply 1 is single-phase full-wave rectified by a single-phase full-wave rectifier IO. As shown in the time chart of FIG. 6, the 13 transistors operate at a chopping period TCH that is 1/4 of the power supply period and 1/2 of the single-phase full-wave rectification period. The rate of on and off of the transistor 13 within the chopping period depends on the limiting input 4 applied externally.

The specific configuration of the control unit 20 that generates the on/off command 3 for the transistor 3 according to the control input 4 will be explained with reference to FIGS. 4 and 5.

FIG. 4 is a detailed block diagram when the control unit 20 is implemented using an analog circuit. The sawtooth wave oscillator 21 generates nine sawtooth waves 6, as shown in the middle part of FIG. The oscillation period Tc)l of this sawtooth wave can be controlled by various methods, and for example, it can be easily changed using the resistor 19.

If the oscillation period of the sawtooth 9-wave oscillator 21 is Tx, then . ='['x, Ns...(1). Therefore, even if Tx is constant, TCH can be changed by changing Ns. On the other hand, although it is possible to vary Tx, it is not economical.

The time chart in FIG. 6 is a diagram when the Tcn is set to 1/2 the cycle of the full-wave rectified waveform (1/4 of the cycle of the AC AC voltage).

The control input 4 is a DC voltage signal applied from the outside, and the larger the current to be passed through the inductance 90, the smaller the value of the control input. (Of course, this is a characteristic limited to this specific example, and generally any on/off characteristic.

It can be done. ) Comparator 22 connects control input 4 and sawtooth wave oscillator 2
Compare output 6 of 1. As a result of the comparison, if the sawtooth wave output 6 is larger than the control input 4, an ON command is given to the transistor driver 24.

Transistor driver 24 provides base current 3 to transistor 13.

A time chart of the above results is shown in FIG.

As mentioned above, the operating layer of the chopper M 'I' c,
Although n can be selected arbitrarily, the present invention can provide an optimal period TCHll.

FIG. 7 is a wave diagram of FIG. 3.4 when the operating period TCH is approximately equal to the period of the single-phase full-wave rectified output waveform. In the figure, the same reference numerals as in FIG. 6 indicate equivalent parts. Average output voltage VDc in this case, where: Voc: Average output voltage (ν) VAC: Effective value of single-phase AC power supply (V) Angle (0) α+lb'1 Both delayed firing angle (0) When formula (2) is calculated, formula (3) is obtained.

However, when x, 10 α, ku π, when X, 10 α1) Vnc by X1
It can be seen that there is a large difference in For example, α, = 90°
1π/2), X, = 45° (π/4) and X, = 13
When calculating the number of differences +jN between 5° (3yr/4) and
AC・−(5)Voc fXl ”45°, α, =90
°l =0.27VAC-(6)V D+: (Xl
90° to 2135ζα) 20.63 V AC-(7)
becomes. That is, as can be seen from equations (6) and (7), even if the control delay firing angle is the same, a difference in the deviation angle causes a difference of 23 times in the average output.

The maximum deviation is that the braking 1 delay firing angle α1 is 180
occurs at values slightly less than °. In other words, X is 90
When X1 is 0° or 180°, a peak value of 11VAC is output, but when X1 is 0° or 180°, the peak value is approximately 11VAC.

FIG. 5 is a block diagram of the case where the 匍misaki unit 20 is realized by a digital circuit. In this case as well, there is no major difference in the basic operation from the analog method.

The oscillation device 25 oscillates at a constant oscillation frequency. This oscillation frequency is calculated by the counter 26 in the next stage.
Add to J and K. The counter 26 starts counting from zero in a direction where all outputs become "1".

If the counter 26 has 0 outputs, for example a 16-bit counter, it has 16 outputs.

Lines with a large number of bits are shown in large groups in FIG.

The first comparator 27 has a copper control j input 4 (first comparator 270B
input) and the output of the counter 26 (A input of the first comparator 27), and when the B input is greater than the A input, the output IA
≧B output). As a result, a base current is supplied to the transistor 13 from the transistor driver L24.

The second comparator 28 operates when the reference value S given via the switch 29 and the count output of the counter 26 match.
Give the counter 26 pulses. As a result, the counter 26 returns to its initial value of zero, and one cycle ends.

This period, that is, the time until the output of the counter 26 reaches the reference value N8 given through the switch 29 from zero is the operating period 'I' of the chopper transistor 13.
'cn.

Next, a case will be shown in which the aforementioned operating cycle l1lcH is set to 1/2 of the single-phase full-wave output cycle.

The following equation is obtained from the output waveform shown in FIG.

If we organize this,...(9) If equation (9) is shown in a diagram, it will look like the fitting part in Figure 10. As you can see from this figure, any X.

It is clear that it is easy to obtain an output proportional to α.

In other words, in FIG. 10, the curves sin θ and −cos θ
.

Since the distance or area between cos θ is approximately constant regardless of the value of X2, ■DC depends only on α2.

When formula (9) is actually calculated numerically, the influence of x2 is of course not zero. Its maximum value is α2-90°,
The difference between when 2=θ° and when X2=45° is,
Even under those conditions, it will only increase by 4 times.

Figure 8 is an example where the cycle TCH of the chopper is set to 1/3 times the cycle of the single-phase full-wave rectified output waveform,
The same reference numerals as in FIG. 6 indicate the same or equivalent parts. In this case, the maximum and minimum ripples are x, == ao
' and X occur at 〇°, and the ratio is 2/)/3=1.1
It is 5 times smaller than 121.414 times.

Figure 9 shows the chopper period +1. 8 is a diagram similar to FIG. 8 for the case where +C is six times the single-phase full-wave rectified output waveform. In this case, the ripple ratio becomes even smaller,
A numerical calculation yields 1.035.

As mentioned above, the shorter the chopper period TC)l becomes compared to the source period l, the smaller its output ripple becomes.

On the other hand, if the collector current is constant, the loss of the switching transistor is determined by the switching frequency fcu I
With increasing fcu = 1/TCHl, tcI
(increases from n to (jintong n = 1.5 to 3).

The above state is shown in FIG. Increasing the chopper frequency increases the ripple rate (ripple) of the output voltage applied to the load.
Curve C1) in FIG. 11 decreases by 1, but on the other hand, the loss of the switching transistor C2 in FIG.
) increases rapidly.

Therefore, in practice, there is also an upper limit to the switching frequency mentioned above. With the switching ability of current transistors,
Usually, the upper limit is about 2K HIf, so it is a value that is sufficiently larger than twice the commercial frequency f8 (that is, the frequency of full-wave rectification), for example, the commercial frequency f11 of 60 Hz.
, the color becomes about 17 times blacker, and if a value within this range is adopted, the pulsation rate can be reduced to a factor of 1.0 or less.

However, as is clear, if the chopper frequency is as low as possible, the loss will be smaller for the same transistor, and therefore a larger output current will be obtained.

From the above explanation, if the cycle of the chopper is set to 1/2 or less of the single-phase full-wave rectified power supply cycle, the output ripple ratio will be 1/1/
It will be appreciated that it can be less than or equal to 2.

The inductance that is the load in FIG. 3 may of course be a resistive load, or even if it is a load that includes both resistance and inductance, the above-mentioned condition @h is fully satisfied. Further, although full-wave rectification using four diodes is used in FIG. 3, the same function can be expected even when two diodes and a center tap transformer are used.

〔Effect of the invention〕

According to the present invention, the power supply smoothing capacitor inserted on the DC output side of the rectifier circuit can be reduced in capacity or omitted, and the transistor is turned on/off in a power supply asynchronous format that is suitable for microcontrollers and is resistant to noise. Since it is possible to carry out controlled unloading, it is possible to realize a chopper controlled unloading device that is excellent in terms of reliability and economical efficiency.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an example of a conventional chopper-controlled rectifier circuit, FIG. 2 is a time chart of the conventional example, FIG. 3 is a block diagram of a basic embodiment of the present invention, and FIG. FIG. 5 is a block diagram showing an example of the digital control unit in FIG. 3. FIG. 6 is a time chart (double cycle) of an embodiment of the present invention. , FIG. 7 is a time chart for explaining the drawbacks in the case of 1 times the period, FIG. 8 is a time chart in another operation example of the invention (3 times the period), and FIG. A time chart in an operation example (six times period t, Fig. 11 is a time chart for explaining the effect of the present invention, and Fig. 11 is a graph showing the relationship between chopper frequency, switching loss, and DC output voltage ripple) Yes. 1...AC single-phase acid source, 3...On/off command, 4
... control] input, 10... single-phase full-wave rectifier, 20.
...Regulation! Itll unit, 21... sawtooth wave oscillator, 22... comparator, 24... transistor driver ~. Agent Patent Attorney Akio Takahashi No. 1 No. 2 Ku Kaya 3 K v7b Fig. 7 Fig. 8 Fig. $ 9 Fig. ゛ Fig. 10 $lt Prisoner

Claims (1)

[Scope of Claims] 1. A rectifier that is supplied with a single-phase AC voltage and generates a single-phase full-wave rectified output, and a linked power factor load that is connected in series with a switching element to the full-wave rectified output; and a control unit that applies an on/off suppressing signal to the switching element, and the switching period of the switching element is set to 1/2 or less of the period of the full-wave rectified output. Chopper collateral equipment. 2. The chopper control device according to claim 1 of the 14th amendment, characterized in that the switching timing of the switching element # is an asynchronous type. 3. The chopper control ω11 device according to the patent or item 2, characterized in that the switching period of the switching element is set to be 1/10 or more of the period of the full wave@flow output.