JPS585592B2 - power supply - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a DC power supply device for supplying power to an electronic circuit, and more particularly to a power supply device that obtains a plurality of stable DC power supplies from a single AC power supply with a compact configuration.

Conventionally, there are several configurations of DC power supply devices having positive and negative polarities.

One of them is, as shown in FIG. 1, two windings 1b and lc with the same number of turns provided on the secondary side of the transformer 1 are connected to bridge rectifier circuits 2a and 2b and a smoothing capacitor 3a, respectively.
, 3b are connected.

Further, voltage control units 4a and 4b for stably controlling voltage fluctuations are connected to these DC conversion circuits, and the zero potential of one control unit 4a and the output terminal of the other control unit 4b are commonly connected. A positive power source -v8 is connected to the output terminal of the voltage control section 4a, and a negative power source -v is connected to the common return line of the voltage control section 4b.
s is generated.

Next, FIG. 2 shows another configuration example, in which the center tap of one winding 2b provided on the secondary side of the transformer 1 is set to zero potential, and a rectifier circuit is installed at both ends of the winding 2b. 2 are connected, and smoothing capacitors 3a, 3b and voltage control sections 4a, 4b are provided between both output ends of the rectifier circuit 2 and zero potential.

A positive power supply +V8 and a negative power supply -Vs are generated from the output terminals of both voltage control units 4a and 4b, respectively.The power supply device shown in FIG. However, a separately isolated AC voltage source is required.

Furthermore, since the power supply device shown in FIG. 2 has only one secondary winding 2, there is no need to insulate the AC voltage source, but voltage control units 4a and 4b with separate positive and negative configurations are required. This requires a large amount of man-hours for design and assembly.

Furthermore, a common drawback of both devices is that when converting the output voltage of the devices, it is necessary to change the circuit constants of the respective voltage control sections 4at4b.

The present invention has been made in order to eliminate the above-mentioned drawbacks, and provides a power supply device that obtains accurate and highly stable DC power by simplifying the overall configuration of the device.

Embodiments of the present invention will be described below with reference to the drawings.

Figure 3 shows the overall configuration of the power supply device, and 10 is a transformer 1.
This is a rectifier circuit that converts the AC voltage output from the secondary winding 1lb of No. 1 into DC.

A smoothing capacitor 12 for smoothing the DC voltage is connected between both output terminals of the rectifier circuit 100, and also detects fluctuations in the output voltage and adjusts it to a predetermined voltage value e.

A voltage control unit 13 is connected thereto.

Only one voltage control section 13 is required for positive voltage control, and for example, a so-called three-terminal regulator made of an IC or the like is used.

Therefore, a voltage dividing resistor R1 is connected to the output side of this voltage control section 13.
, R2 are connected, and an impedance buffer amplifier 14 for determining a zero potential is further connected to a common portion of both resistors R1 and R2.

Specifically, this buffer amplifier 14 has positive and negative input terminals, and connects the positive input terminal to a common connection between both resistors R1 and R2.
Further, the output terminal and the negative input terminal are connected to form a midpoint potential.

Then, with the output end of the buffer amplifier 14 set to the midpoint potential (zero volts), a positive power supply +v8 is applied from the common part of the output part of the voltage control section 13 and the resistor R1, and a negative power supply +v8 is supplied from the common part of the common return line and the resistor R2. The power supply -Vs is generated.

RL1 and RL2 are load resistances connected between the positive and negative power supplies V8 and -VS and zero potential.

Note that there are various configurations of the impedance buffer amplifier 14, but for example, the load current is several 10.
If the current is within mA, an inexpensive general-purpose operational amplifier may be used, and when handling a relatively large current load, an operational amplifier 14a and a pair of transistors 14b, 14b as shown in FIG.
It is preferable to use a circuit in which a good emitter-follower circuit is connected.

If highly stable positive and negative power supplies +v8 and -vs are not required, it is sufficient to simply use a pair of transistors 14b and 14b as an emitter-follower circuit, as shown in FIG.

Next, the operation of the power supply device configured as described above will be explained.

First, the resistors R1 and R2 are set to R1=R2, and the output voltage e of the voltage control section 13 is set.

is set to a voltage of eQ - (+Vs) (-Vs).

On the other hand, by using an impedance buffer amplifier 14n operational amplifier, etc., the input impedance is ideally infinite, and the output impedance is almost zero.

Therefore, the input voltage eq of the impedance buffer amplifier 14 is: eq''eo・R1/R1+R2 (1), and the output voltage eq′ of the buffer amplifier 14 is: eq′=eq=e0・R1/ R1+R2...(2).

Therefore, the output voltage eq of the buffer amplifier 14 is the voltage e0
If it can be treated as the midpoint of +V3=e0・R1/R1+R2...(3)-VS=
e0・R1/R1+R2...<4) positive and negative power supplies are obtained, and if R1=R2, the positive and negative power supplies are -R/
An equal voltage of 2e0 will be obtained.

By the way, in the device shown in Figure 3, the impedance
If the buffer amplifier 14 were not present, the circuit configuration would be as shown in FIG.

In this case, load resistors RL1, RL are added to voltage dividing resistors R1, R2.
2 are connected in parallel, so the load resistance RL1
, RL2 changes, equivalently the voltage dividing resistors R1, R2
changes, and the ratio of the positive and negative power supplies +v8 and -v8 changes.

In other words, the voltage dividing resistors R1 and R2 make accurate voltage division impossible.

On the other hand, when the impedance buffer amplifier 14 is connected to the common part of the voltage dividing resistors R1 and R2, the configuration is equivalently shown in FIG. 7, and the buffer amplifier 14 has a high input impedance and a low output impedance. If the voltage gain is 1.0, the voltage dividing resistors R1 and R2 are the load resistors R
Since it is completely unrelated to changes in L1 and RL2, arbitrary positive and negative power supplies can be obtained depending on the resistance values of the voltage dividing resistors R1 and R2.

In the above embodiment, a case has been described in which two positive and negative power supplies +VS and -vS are obtained, but with this configuration, two or more power supplies can be easily created.

For example, when obtaining three power supplies of +VS1, +VS2, and -VS, three voltage dividing resistors R1, R2, and R3 are connected to the output side of the voltage control section 13, and the resistor R2 and The first impedance buffer amplifier 14 is connected to the common part with R3 to set the output part to zero potential, and the resistor R1
A second impedance buffer is installed in the common part between R2 and R2.
The configuration is such that an amplifier 14 is connected and the output side is connected to zero potential via a load resistor RL1.

In the apparatus shown in FIG. 8, if the output voltage of the voltage control section 13 is e0, then the respective power supplies +VS1, +VS2
, -■8 is +vs1=e0/R2/R1+R2+R3...(5)
+VS2-e0・R2+R1/R1+R2+R3...
(6)-VS=e0・R3/R1+R2+R3...(
7).

As described in detail above, according to the present invention, a plurality of voltage dividing resistors are connected to the output part of one DC voltage source, and the voltage divided by the resistors is applied to an impedance buffer amplifier with high input impedance and low output impedance. Since the amplifier output is set to the midpoint potential or zero potential by connecting the You can get it.

Moreover, since the configuration of the entire device is very simple, the number of man-hours for design and assembly can be reduced, contributing to cost reduction.

In addition, by connecting the load equipment with the output of the high-input, low-output-impedance amplifier set to the midpoint potential, the DC output voltage applied to the voltage dividing resistor is not affected by the load equipment at all. Multiple highly stable DC power sources can be obtained.

[Brief explanation of drawings]

1 and 2 are configuration diagrams of a conventional power supply device, FIG. 3 is a configuration diagram showing an embodiment of the power supply device according to the present invention, and FIG.
Figure 5 and Figure 5 are specific configuration diagrams of the impedance buffer amplifier shown in Figure 3, Figure 6 is the case without the impedance buffer amplifier, Figure 7 is the case with the impedance buffer amplifier. The equivalent circuit diagram of
FIG. 8 is a configuration diagram showing an example of obtaining three DC power supplies. 13... Voltage control unit, 14.14... Impedance buffer amplifier, R1, R2, R3... Voltage dividing resistor, RL1, RL2, RL3... Load resistor.

Claims (1)

[Claims] 1. A DC voltage regulator that converts AC voltage into DC, a voltage divider circuit consisting of a plurality of resistors connected in series to the output end of this DC voltage source, and a resistor of this voltage divider circuit. An impedance buffer amplifier with a high input impedance and an output impedance connected to a mutual common part and whose output side has a midpoint potential or zero potential, and the output side of this impedance buffer amplifier has a midpoint potential or zero potential. A power supply device characterized in that a plurality of positive and negative blood flow power supplies are obtained from both ends of the DC voltage source with reference to potential. 2. The voltage divider circuit is multi-divided by a plurality of resistors, and a plurality of impedance buffer amplifiers are connected to a common part between the resistors to obtain three or more DC power supplies, as set forth in claim 1. power supply.