JPH0578272B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a voltage control device that can efficiently control and output a wide range of output voltages with low ripple and stability.

[Conventional technology]

For example, standard voltage generators require highly stable and wide-range voltage control. A series regulator or a DC/DC converter system is known as such a voltage control device.

However, with the series regulator method, it is not possible to obtain an output higher than the input voltage. On the other hand, a DC/DC converter switches the DC input, boosts the voltage in a transformer, and then rectifies and smooths it. This has the advantage of easily extracting a high DC voltage that is higher than the input voltage.・Because the smoothed output is taken out directly, ripples remain in principle, and the response is inferior to the direct control method using a series regulator. Furthermore,
In order to control output, DC/DC converters cannot provide sufficient feedback as compared to series regulator systems, and in terms of output stability, they are inadequate to the level required for standard voltage generators.

[Problem that the invention seeks to solve]

The present invention provides a series regulator and a DC/
The above-mentioned problems of DC converters are solved, and a voltage control device suitable for use in standard voltage generators and the like is obtained with a simple configuration.

[Means for solving problems]

In order to achieve the above object, the present invention includes a voltage control circuit that includes an error amplifier that amplifies the difference between a variable reference voltage and a feedback voltage obtained from an output circuit, and that controls the output voltage in proportion to the reference voltage; and a high-voltage DC voltage obtained by rectifying the secondary side output of a step-up transformer whose primary side is connected to a transistor switch that uses the output of the error amplifier as an input of a comparator and opens and closes when this input exceeds a set voltage. and a DC-DC converter which adds this high-voltage DC voltage to the output of the voltage control circuit and extracts it from the output circuit. Examples will be described in detail below.

[Embodiment] FIG. 1 is a connection diagram of an embodiment of the device of the present invention. In the figure, fo is a rectangular wave pulse, G is a gate, COP is a comparator, and Ec is a set voltage of this comparator. comparator
COP is the voltage V1 input to this and the set voltage Ec
When V1>Ec, the output becomes "H" level, and the rectangular wave pulse fo passes through the gate G at this time. Q is the square wave pulse that passed through gate G
A transistor that is turned on and off at the repetition period of fo, PT is a transformer that boosts the on/off signal,
D1 and C1 are diodes and capacitors that constitute the rectifier circuit RE. The primary winding N1 of the step-up transformer PT is connected in series with the transistor Q, and the secondary winding N2 has a diode D1 and a capacitor C.
1 is connected. O1 and O2 are output terminals,
The output terminal O2 is connected to the reference potential point COM. RL is a load, Rv is a voltage dividing resistor that divides the output voltage Eo obtained from the output terminals O1 and O2 at a voltage dividing ratio β, A1 is an error amplifier, and Er is a reference voltage whose value is variable. Error amplifier A1 is the reference voltage
Er and the divided voltage βEo of the output voltage Eo are compared and the difference is amplified. If the output voltage of the error amplifier A1 is V1, the voltage V1 is
It is added to COP and compared with its set voltage Ec, and is added to the DC high voltage V2 obtained by the capacitor C1 in the rectifier circuit RE. In such a configuration, the operation will be explained using the waveform diagram of FIG. 2 as follows.

The comparator COP has a set voltage shown in Figure 2 A.
Compare Ec with the output voltage V1 of the error amplifier A1 shown in Fig. 2B, and when V1>Ec, the output of COP becomes "H" level, and the rectangular wave pulse fo shown in Fig. 2C passes through the gate G. and turns transistor Q on and off. As a result, a high voltage is generated in the secondary winding N2 of the step-up transformer PT, and this high voltage is rectified by the diode D1 and then transferred to the capacitor C1.
It is filtered and becomes a DC high voltage V2 as shown in FIG. 2D. An error amplifier A1 is connected to such a DC high voltage V2.
The generated voltage V1 is added and taken out from terminals O1 and O2 as an output voltage Eo as shown in FIG. At the same time, the output voltage Eo is divided by a voltage dividing resistor Rv connected between terminals O1 and O2. The difference voltage (error voltage) between this divided voltage βEo and the reference voltage Er shown in FIG. Ru. At this time, if the gain of the error amplifier A1 is sufficiently large, the difference (error voltage) approaches zero, and the output voltage Eo is controlled so that the divided voltage βEo becomes equal to the reference voltage Er. There are two operating modes depending on the desired output voltage Eo:

That is, (a) When trying to control the output voltage Eo to a low value, the value of voltage V1 is low and V1<Ec-eh
(eh is the hysteresis width of the comparator COP), the switching circuit consisting of the comparator COP and the gate G does not operate, and this voltage V1 is passed through the diode D2 to the output voltage Eo.
As shown in FIG. 3, the output voltage Eo is controlled only by the error amplifier A1. Note that in FIG. 3, V is a battery power source.

(b) When trying to control the output voltage Eo to a large value, the value of the output V1 of the error amplifier A1 becomes large,
When V1>Ec, a switching circuit is activated by the comparator COP and the transistor Q, and the output voltage Eo is controlled by V1+V2. The switching operation is repeatedly activated and stopped within the range of the hysteresis width eh of the comparator COP. As a result, the voltage V1 is at the second level in the steady state.
As shown in Figure B, it remains at the level of Ec to Ec-eh.
Outputs exceeding this level will be supplied by the switching circuit. That is, the voltage V1 is V
2, and the added output voltage Eo is controlled in proportion to the reference voltage Er, as shown in FIG.

Figure 1 shows a voltage control type circuit, while Figure 4 is a circuit diagram of an embodiment of the present invention in which the current control type is used. Therefore, their re-explanation will be omitted. In FIG. 4, Rs is a resistor connected between the output terminal O2 and the common potential point COM. The connection point between the output terminal O2 and the resistor Rs is connected to the error amplifier A1.

In the circuit of FIG. 4 having such a configuration, as in FIG. 1, when V1>Ec, the switching circuit,
That is, a direct current (DC)-direct current (DC) converter operates to obtain a high DC voltage V2, and this voltage V2 and V
An additional voltage of 1 is supplied to the load RL. The current flowing through the load RL due to this added voltage causes a voltage drop Vs across the resistor Rs, and this Vs is applied to the error amplifier A1 and is controlled so that the voltage difference from the reference voltage Er approaches zero. Ru. When V1<Ec, the switching circuit stops operating and the output voltage Eo is controlled by the error amplifier A1.

FIG. 5 is a circuit diagram of yet another embodiment of the present invention. In FIGS. 1 and 4, the voltage control circuit controlled by the error amplifier is shown as "A1", but in both the constant voltage and constant current systems shown in FIGS. 1 and 4, the error amplifier is controlled by the error amplifier as shown in FIG. Transistors Q1 and Q2 may be connected in a subordinate manner to the output terminal of A1, the collector electrode of Q2 may be connected to the comparator COP and the capacitor C1, and a +V power source may be applied to the emitter electrode. In the circuit of FIG. 5 constructed in this way, the voltage V1 is as shown in FIGS. 1 and 4.
There is no saturation on the negative side of , and the output response characteristics are improved when the output setting value is lowered.

[Effects of the present invention]

As explained above, when configuring a battery-powered calibrator (standard voltage generator), for example, according to the present invention, the configuration is relatively simple, and when the set voltage, that is, the output voltage Eo is low, the battery power supply Output can be directly and stably controlled. This is equivalent to a series regulator. Furthermore, when the output voltage Eo is set high, a DC/DC converter consisting of a switching circuit automatically operates. This makes it possible to obtain a continuous output voltage from low DC voltage to high voltage. This DC/
The output voltage V2, which is rectified and smoothed during operation of the DC converter, includes ripples like a general DC/DC converter. However, in the device of the present invention, the rectified and smoothed output V2 is converted into the output voltage V2
Since the configuration is such that the ripple is taken out and fed back to the error amplifier A1, the ripple is canceled in this error amplifier portion, and no ripple appears in the output voltage Eo.

Moreover, by setting the gain of the error amplifier A1 sufficiently large, unstable elements can be removed and a stable output can be obtained. Furthermore, the present invention, which has a composite configuration of the switching/boosting/rectifier circuit and the error amplifier A1, requires highly stable and wide-range voltage control, such as the response being immediate within the range covered by the error amplifier A1. An extremely suitable voltage control device for use in standard voltage generators can be obtained with a simple configuration.

[Brief explanation of the drawing]

Fig. 1 is a connection diagram of an embodiment of the device according to the present invention, Fig. 2 is a waveform diagram for explaining the operation of the device shown in Fig. 1, and Fig. 3 is a waveform diagram for explaining the operation of the device shown in Fig. 1. 4 and 5 are connection diagrams of other embodiments of the device of the present invention, respectively. A1...Error amplifier, Er...Reference voltage, Rv...
...Voltage dividing resistor, COP... Comparator, Ec...
Set voltage, Q...transistor, PT...transformer,
C1...capacitor, D1, D2...diode.

Claims (1)

[Scope of Claims] 1. A voltage control circuit that includes an error amplifier that amplifies the difference between a variable reference voltage and a feedback voltage obtained from an output circuit, and that controls the output voltage in proportion to the reference voltage. The output is the input of a comparator, and it has a transistor switch that opens and closes when the input exceeds the set voltage of the comparator, and is obtained by rectifying the secondary output of a step-up transformer whose primary side is connected to this transistor switch. A voltage control device comprising: a DC-DC converter that controls a high-voltage DC voltage, adds an output of the voltage control circuit to the high-voltage DC voltage, and extracts the result from the output circuit.