JPH03212155A - Voltage control method for dc/dc converter - Google Patents

Abstract

PURPOSE:To settle momentary fluctuation of a DC/DC converter, regardless of abrupt variation of load, by setting the variation of the conduction rate of a semiconductor switch at a high level for the low output voltage region of a voltage regulator while setting it at a conventional. level for the high output voltage region. CONSTITUTION:A phase shifter reference signal generating circuit 20 comprises a counter 21, a memory 22 and a D/A converter 23. The memory 22 stores such data as output voltages from a voltage regulator (AVR) and conduction rate have specific nonlinear relation. The counter 21 receives a signal from a transmitter 16 and reads out data, which are then converted through the D/A converter 23 into analog amount and provided to a comparator. The conduction rate is varied considerably against a slight fluctuation of AVR output voltage for a region where the conduction rate of a semiconductor switching element is low, whereas variation of the conduction rate is suppressed for a region where the conduction rate is high. By such arrangement, momentary fluctuation of DC/DC converter can be suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage control method for a DC/DC converter that can suppress instantaneous fluctuations in output voltage in response to load fluctuations.

[Conventional technology]

FIG. 3 is a circuit diagram showing a general example of a control circuit that controls the output voltage of a DC/DC converter to be constant.

In FIG. 3, DC power from a DC power supply 2 is converted by a DC/DC converter 3 into DC power of a desired voltage that is isolated from the DC power supply 2. After the ripple is absorbed and removed by a smoothing circuit composed of a reactor 4 and a capacitor 5, it is supplied to a load 6.

Here, the DC/DC converter 3 includes a GTO inverter 31.32 as a semiconductor switching element, a freewheeling diode 33.34 connected in antiparallel to the GTO inverter 31.32, and a capacitor 35.36 connected in parallel to these. , a transformer 37, and rectifier diodes 38 and 39 connected to the secondary side of the transformer 37. Therefore, by turning on and off the GTO thyristors 31 and 32, the direct 2i from the DC power supply 2 is
After converting the t power into AC power, insulating and transforming it with a transformer 37, it is again converted into DC power with rectifier diodes 38 and 39.

The output voltage of the DC/DC converter 3 configured in this manner can be set to a desired value by changing the ratio of the on time occupied by the GTO thyristor 31, 32 during one cycle of on/off operation, that is, the conduction rate α. maintain.

A voltage setting device 11 in FIG. 3 sets a voltage target value. On the other hand, since the voltage detector 12 detects the actual voltage value applied to the load 6, the adder 13 calculates the deviation between the voltage target value and the actual voltage value.

A voltage regulator (hereinafter referred to as A) consisting of a proportional-integral calculator
(abbreviated as VR) 14 inputs this deviation value and outputs a control signal to make this input deviation zero.

On the other hand, since the oscillator 16 and the phase shifter reference signal generation circuit 17 create a triangular waveform phase shifter reference signal with a constant frequency and a constant peak value, the comparator 15
By guiding the output of the VR 14 and the phase shifter reference signal and comparing the magnitude relationship between the two, an on/off signal with a desired conductivity can be obtained. The pulse distributor 18 controls the DC/DC converter 3 so that the actual voltage value matches the target voltage value by applying this to the GTO thyristors 31 and 32 to turn them on and off.

FIG. 4 is a time chart showing the relationship between the input and output of the comparator 15 shown in FIG. is comparator 1
5 output signals, respectively.

In FIG. 4, the triangular waveform A is the phase shifter reference signal, and since the frequency and peak value are constant as described above, the slope of the oblique side of the triangular waveform is also constant. Further, the output signal of the AVR 14 is drawn as a straight line B, and the output signal value E of the AVR 14 changes in accordance with load fluctuations of the load 6 and voltage fluctuations of the DC power supply 2.

Therefore, by comparing the magnitude relationship between the phase shifter reference signal A and the output signal B of the AVR 14, the pulse train shown in FIG. 4 (b) can be obtained. The smaller value α is the conductivity. Note that f is the frequency of the phase shifter reference signal, and therefore 1/f is its period.

FIG. 5 is a graph showing the relationship between the AVR output and conduction rate obtained from the time chart of FIG. 4, where the horizontal axis represents the conduction rate α, and the vertical axis represents the AVR output.
The two have a linear relationship.

[Problem to be solved by the invention]

Output voltage ■ of the DC/DC converter 3 as shown in FIG. is when the DC/DC converter is in normal operation, except when there is no load or a light load close to no load.
It can be calculated using the following equation (1).

■. = □ α ・ v, −−−−−−−
−−−−−, −−1・−(1) However, α is the GTO thyristor 31.32 as mentioned above.
The conductivity, ■, is the input voltage of the DC/DC converter 3, and n is the turns ratio of the transformer 37.

The turns ratio n is selected so that the conductivity α becomes close to 1 when the ship is operated with the load 6 connected to the DC/DC converter 3. Therefore, the conductivity α under load generally changes within a range of 0.5 to 1 with respect to fluctuations in the input voltage V.

However, when the DC/DC converter 3 is operating with no load or with a light load close to no load, the capacitor 5 forming the smoothing circuit is almost in a peak charging state. Therefore, the output voltage ■. In order to control the conductivity at a constant value, the conductivity α must be set to a value much smaller than that under load. In other words, as shown in FIG. 5, the output voltage of the AVR 14 is a small value El, and its The conductivity at this time is also a small value α.

Here, when the load on the DC/DC converter 3 suddenly reaches full load, the output voltage of the AVR 14 is controlled from P<E, which makes the conductivity α mushroom, to E2.
R14 output voltage change ΔE (i.e. Ex El
) is large, the response of this AVR 14 cannot follow, and as a result, there is a drawback that instantaneous fluctuations in the output voltage of the DC/DC converter 3 become large. (Similarly large instantaneous voltage fluctuations occur when there is a sudden change from full load to no load.)
Therefore, an object of the present invention is to reduce the instantaneous fluctuations in the output voltage of the DC/DC converter by reducing the load's 2. The goal is to suppress any changes that may occur so that they do not become large.

[Means to solve the problem]

In order to achieve the above object, the voltage control method of the present invention compares the magnitude relationship between a triangular waveform phase shifter reference signal whose frequency and peak height are constant and the output signal of the voltage adjustment means. In the voltage control method for a DC/DC converter, the conductivity corresponding to the level of the output signal of the voltage adjusting means is determined, and the semiconductor switching elements constituting the DC/DC converter are operated according to the conductivity. In a region where the output signal is at a low level, the conductivity changes greatly in response to a change in the output signal of this voltage regulating means, and in a region where the output signal of the voltage regulating means is at a high level, the conductivity changes greatly in response to a change in the output signal of this voltage regulating means. The waveform of the phase shifter reference signal is determined so that the change in conductivity is small.

[Effect]

Conventionally, there was a linear relationship between changes in conductivity and changes in AVR output voltage, so the AVR output voltage could not follow load fluctuations sufficiently. However, in the present invention, the AVR output voltage
A is set so that the change in conductivity corresponding to the change in AVR output voltage is large in the region where the output voltage is at a low level, and the change in conductivity corresponding to the change in the AVR output voltage is small in the region where the AVR output voltage is at a high level.
By creating a phase shifter reference signal waveform in which the VR output voltage and conductivity have a nonlinear relationship, the AVR output voltage can quickly follow sudden changes in the load, and the DC/DC converter output voltage The aim is to suppress instantaneous fluctuations in

〔Example〕

FIG. 1 is a block diagram showing the configuration of a phase shifter reference signal generation circuit showing an embodiment of the present invention.

In the present invention, the 31st! In place of the phase shifter reference signal generation circuit 17 shown in the general example circuit shown in FIG.
Use what is shown in the figure. That is, the phase shifter reference signal generation circuit 20 includes a counter 21, a memory 22, and a digital/analog converter (hereinafter abbreviated as a D/A converter) 23, and the memory 22 stores the AVR output voltage and conductivity. It stores data of a phase shifter reference signal such that the phase shifter has a predetermined nonlinear relationship.

The counter 21 receives the signal from the oscillator 16 and reads out the above-mentioned data, and the D/A converter converts this into an analog quantity and outputs it to the comparator 15 shown in FIG.

Figure 2 shows the AVH when using the example circuit shown in Figure 1.
A graph showing the relationship between the output and conductivity of
The horizontal axis represents the conductivity α, and the vertical axis represents the AVR output.

In this FIG. 2, in the region where the conductivity α is smaller than 0.5, the conductivity α is
changes greatly, and in a region where the conductivity α is greater than 0.5, the change in the conductivity α is not so large.

Due to the nonlinear relationship shown in FIG. 2, the change in AVR output voltage when the conductivity changes from α1 to α is
In the conventional example shown in the figure, it is necessary to make a large change from E to E8, but in the present invention, it is a change from Et+ to Ell, and the range of change is smaller than in the conventional example.

The nonlinear characteristics illustrated in the present invention are broken line characteristics made up of two straight lines, but they may also be broken line characteristics made up of more straight lines, or smooth to curved lines. This can be easily executed by changing the data stored in the memo +7-22 shown.

〔Effect of the invention〕

According to this invention, the amount of change in the conductivity α of the semiconductor switching element constituting the DC/DC converter is large in the region where the output voltage of the AVH is low, and is kept at a value similar to the conventional value in the region where the output voltage of the AVH is high. By making the non-linear characteristics such as , the load of the DC/DC converter becomes Even when the change width of the AVR output voltage is made smaller than before, the predetermined amount of change in conductivity can be secured, so the delay in tracking the AVR output voltage can be reduced, and as a result, the instantaneous voltage of the DC/DC converter can be reduced. This has the effect of significantly improving fluctuations.

[Brief explanation of drawings]

Fig. 1 is a schematic diagram showing the configuration of a phase shifter reference signal generation circuit showing an embodiment of the present invention, and Fig. 2 shows the output and conduction of the AVR when the embodiment circuit shown in Fig. 1 is used. Figure 3 is a circuit diagram showing a general example of a control circuit that controls the output voltage of a DC/DC converter to a constant value. Figure 4 is a graph showing the relationship between the output voltage of a DC/DC converter and FIG. 5 is a graph showing the relationship between AVR output and conduction rate obtained from the time chart of FIG. 4. 2...DC power supply, 3...DC/DC converter, 6
...Load, 11...Voltage setting device, 12...Voltage detector, 14...AVR115...Comparator, 16...
- Oscillator, 17.20... Phase shifter reference signal generation circuit,
1st...Pulse distributor, 21...Counter, 22.
...Memory, 23...D/A converter, 31, 3
2...GTO thyristor as a semiconductor switch element, 33.34...Freewheeling diode, Figure 2.

Claims (1)

[Claims] 1) By comparing the magnitude relationship between the triangular waveform phase shifter reference signal with constant frequency and peak value and the output signal of the voltage adjustment means, the conductivity corresponding to the level of the output signal of the voltage adjustment means is determined. In a voltage control method for a DC/DC converter, in which the semiconductor switching elements constituting the DC/DC converter are operated according to the conductivity of the DC/DC converter, in a region where the output signal of the voltage regulator is at a low level, In a region where the change in conductivity with respect to a change in is large and the output signal of the voltage adjustment means is at a high level, the change in conductivity with respect to a change in the voltage adjustment means output signal is small, so that the phase shifter reference A voltage control method for a DC/DC converter, characterized by determining a signal waveform.