JPH01303049A - Variable voltage source - Google Patents

Abstract

PURPOSE:To reform the linearity of in- and output characteristics, by negatively feeding back the voltage equivalent to the output voltage of the 1st compound element to the input side through the 2nd compound element. CONSTITUTION:A variable voltage source is composed of a photocoupler PVC1, the 1st compound element, a photocoupler PVC2, the 2nd compound element, and an operational amplifier A. This coupler PVC1 generates the output voltage Vout for driving a load, where a load resistor RL is connected to both ends of a built-in photodiode array PDA1, and the voltage is fed back to the operational amplifier A negatively. In the operational amplifier A the input voltage Vin thereby becomes the same as the output voltage VOC of the photocoupler PVC2, so that the linearity of the in- and output characteristics can be reformed.

Description

[Detailed description of the invention] [Objective of the invention] (Industrial application field) This invention uses a composite element formed by optically coupling a light emitting diode and a photoelectric conversion element such as a photocell as an insulating means. This invention relates to improvements in control input isolated type variable voltage sources.

(Prior Art) In this type of variable voltage source, a composite element formed by optically coupling a light emitting diode and a photocell is used as an insulating means.

Figure 3 (A) is a chip wiring diagram showing the side lid 'ITPL590 (product name: Photopol coupler) as an example of such a composite element, and Figure 3 (B) is its forward current I[-open circuit voltage VOC characteristic. This is a graph showing.

As shown in the same figure (A), this composite element 1 is formed by optically coupling an infrared light emitting diode 2 and a diode array 3 to a photovoltaic cell (photocell). , infrared> to the photodiode 2, an output voltage Voc can be obtained from both ends of the switch 11 to the diode array 3. Note that "R8I" in the figure is a load resistance.

Then, as shown in the same figure (B), the output voltage VOC
The value of changes depending on the value of forward current I[.

Therefore, by using this composite element 1 as an insulating means, a control input isolated type variable voltage source can be manufactured.

Such a variable voltage source can be used, for example, as a power MO3 FET.
If used for driving the power system, it becomes possible to drive the power system completely separate from the signal system.

In other words, conventionally MO3-FFT was driven using 1 to transistor transistors, but in this case an external power supply for gate drive was required. According to the composite element used as the cell, an electromotive voltage sufficient for driving the gate can be obtained from the cell itself, so that it is possible to directly drive the gate without an external power source.

(Problem to be Solved by the Invention) However, in the conventional variable voltage source using this J:Una composite element 1, as shown in FIG. 3(B), the IF - VOC characteristic of the element 1 is nonlinear, so
The previous problem is that the output voltage cannot be changed linearly with respect to the control input.

An object of the present invention is to improve the linearity of the input/output characteristics in a control input isolated type variable voltage source using a composite element having such nonlinear input/output characteristics as an insulating means.

(Structure of the Invention) (Means for Solving the Problems) In order to achieve the above object, the present invention optically couples a light emitting diode and a cell, and increases the forward current of the light emitting diode. Adjust the output voltage according to the
- A first composite element obtained from a cell is optically coupled to a light emitting diode and a photocell, and an output voltage corresponding to the magnitude of the forward current of the light emitting diode is output from the photocell. and a second composite element in which the same or proportional forward current as that of the light-emitting diode of the first composite element flows through the light-emitting diode, and a light-emitting diode of the first composite element. an amplifier that supplies a forward current and is subjected to negative feedback by the cell output of the second composite element;
The present invention is characterized in that an input voltage is supplied to the amplifier, and an output voltage is taken out from the A cell of the first composite element.

[Effect]

According to such a configuration, since the voltage corresponding to the output voltage of the first composite element is negatively fed back to the input terminal via the second composite element, it is possible to improve the linearity of the input/output characteristics. I can do it.

〔Example〕

FIG. 1 is a circuit diagram showing an embodiment of a variable voltage source according to the present invention.

This variable voltage source is composed of a photopol coupler PVC1 which is a first composite element, a photopol coupler PVC2 which is a second composite element, and an operational amplifier A.

Photo Polkapurara PVC1 and Fu A1 ~ Polkapura P
The one having the same transfer function as VC2 is selected.

The photopol coupler PVC1 has an output voltage V for driving the load.
In this example, a load resistor RL is connected to both ends of the built-in photodiode array PDA 1.

Photopol coupler PVC2 is Photopol coupler PV,
This is for negative feedback of a voltage corresponding to the output voltage Vout of C1 to an operational amplifier A, which will be described later.

That is, on the output side to the operational amplifier, an infrared light emitting diode IED1 of the photopolymer PVC1 and an infrared light emitting diode LED2 of the photopolymer PVC2 are connected in series via a current limiting resistor Rc. Therefore, the same forward current I[ as infrared light emitting diode LED1 of the photopol coupler PVC1 flows through the infrared light emitting diode LFD2 of the hook 1 to photocoupler PVC2.

In addition, a short-circuit resistor R3 having the same resistance value as the load resistor R[ is connected to both ends of the photodiode array PDA2 of ), 7I Toborno J plastic PVC2. and PVC2
Since the transfer function is the same as that of photopol coupler PV
C2 output voltage VOC and) 41 ~ Porno J Plastic PVC1
The output voltage VOut is almost the same as J in the following equation.

Voc-Vout (1) And the output voltage Vo of this photopol coupler PVC2
The signal c is supplied to the inverting input terminal of the operational amplifier A, so that the operational amplifier A applies negative feedback to the circuit 741 with a voltage corresponding to the output voltage VOUT of the polar coupler PVC1.

As is well known, the operational amplifier A operates to keep the inverting input and the non-inverting input at the same potential based on the principle of imaginary short, and as a result, the input voltage Vin and the output voltage VOC of the voltage coupler PVC2 are as follows. They are almost the same as in the formula.

Vin=Voc---- (2) As a result, from the above equations (1) and (2>, the output voltage Vout of the photopol coupler PVC1 and the control input voltage Vin
are always equal as shown in the following equation, and the linearity of the input/output characteristics is improved.

Vln-VOut (3) FIG. 2 is a circuit diagram showing another embodiment of the variable voltage source according to the present invention.

The features of this embodiment are that a sufficient output voltage can be obtained even when the load resistance RL is small, and that DC input can be used as an input for voltage control.

Since the output current of the photopol coupler is as small as several μA, if the load resistance R[ is small, a sufficient output voltage Vout cannot be obtained as it is.

Therefore, in such a case, photopol coupler PCI
The output current of (1) is amplified by the buffer transistor Q1 connected to Mitsutaf 40 watts and applied to the load resistor RL, thereby making it possible to obtain a sufficient output voltage Vou↑.

In this case, it goes without saying that a buffer transistor Q2 with similar characteristics must be provided on the output side of the )yrl'' polar coupler PVC2 so that VOut=VOC.

In addition, a variable resistor VR is connected between the input power supplies V ccl, V EE, and 1, and this is divided appropriately to set the input voltage Vi.
Since n is obtained, the value of the DC output voltage Vout can be arbitrarily adjusted by operating the variable resistor VR.

In the above embodiment, the same current was passed through the light emitting diodes of both photopol couplers, but the current of the light emitting diode of the first photopol coupler was divided and a part of the current was applied to the light emitting diode of the second photopol coupler. It can also be passed through a diode.

18- [Effects of the Invention] As is clear from the above explanation, according to the present invention, in a control input isolated type variable voltage source using a composite element with nonlinear input/output characteristics, The linearity of output characteristics can be improved.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing an embodiment of a variable voltage source according to the present invention, Fig. 2 is a circuit diagram showing an embodiment of the same, and Fig. 3 (A
, ) is a depth connection diagram showing an example of a composite element, (B)
is a graph showing forward current-open circuit voltage characteristics of the composite element. 1... Composite element, 2... Infrared light emitting diode, 3...
・・Photodiode array, PVCl, PVC2・・
・F, t l-por coupler, A... operational amplifier, Vi
n...Input voltage, Vout...Output voltage. (A) Connector 1 (B) 0c-1F Ta =25'C ヰ° qql g Z Q 〉 ~ , 11 Ltl ” -42”) Treetop ridge

Claims (1)

[Scope of Claims] A first light emitting diode and a first photoelectric conversion element that converts light from the first light emitting diode into an electrical signal are optically coupled, and the forward current of the first light emitting diode is a first composite element configured to obtain an output voltage from the first photoelectric conversion element according to the magnitude of the second photoelectric conversion element; a second light emitting diode; Two photoelectric conversion elements are optically coupled, an output voltage corresponding to the magnitude of the forward current of the second light emitting diode is obtained from the second photoelectric conversion element, and the second light emitting diode has a a second composite element in which a forward current equal to or proportional to that of the first light emitting diode of the first composite element flows; an amplifier that supplies current and is subjected to negative feedback by the output from the second photoelectric conversion element of the second composite element; supplies an input voltage to the amplifier; A variable voltage source characterized in that an output voltage is extracted from a first photoelectric conversion element of the element.