JPH01303807A - Power circuit - Google Patents

Abstract

PURPOSE:To realize a power circuit due to the logarithm-antilogarithm operation with a simple constitution and to facilitate the correction by combining a resistance and a diode to a current mirror circuit. CONSTITUTION:A transistor 3 connects a base collector, uses it as a diode, an emitter is connected through a diode 7 to a power source and the base collector is connected to the base of a transistor 4. The emitter of the transistor 4 is connected through a power source 8 of a potential difference Vgamma2 to a power source 100 and a collector is grounded through a resistance 5. A current Ii in proportion to an input signal level flows at the diode composed of a first transistor 3, a proportion coefficient gamma is multiplied to a generated base emitter voltage VBE2 change, coupled to a base emitter voltage VBE2 of a second transistor 4 and in accordance with the VBE2 change, an emitter current IE2 of the second transistor 4 flows. Thus, only by combining the current mirror circuit diode 7 and the resistance 5, the power circuit can be constituted, and the gammacorrection of the video signal can be executed inexpensively, compactly and easily.

Description

Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a circuit that generates a current (or voltage) proportional to the γ power of a certain signal current (or voltage). The present invention relates to a power circuit suitable for easily performing correction.

[Conventional technology]

The γ correction circuit is a type of nonlinear amplifier, and the input signal A
The output signal BOeA' is calculated by a row 5 power circuit.

It is difficult to implement a circuit that performs such operations1.For example,
"Image Electronic Circuits" (Image Electronics Course, edited by the Televising Society, edited by Utsunomiya et al., Corona Publishing), pages 82-83. It is common to do so.

In order to realize a more accurate power-law circuit, 1. For example, as described in "Analog IC Utilization Handbook" (Transistor Technology Special Edition Hardware Design Series CQ Publishing), pages 139 to 142, an operational amplifier (OP amplifier) is used. It is necessary to perform a power calculation by combining the logarithm calculation circuit used and the antilogarithm calculation circuit used.

[Problem to be solved by the invention]

In the above conventional technology, 1. For example, when approximating a power function using a broken line or an exponential function, it is very difficult to set constants for determining the target function.In broken line approximation, the number of broken lines and the slope of each broken line must be determined individually. As the degree of approximation increases, the circuit configuration becomes dramatically more complex. In addition, in exponential function approximation, the value of γ corresponding to the circuit constant is not determined accurately, and it often takes time to decide the design value.

On the other hand, performing γ correction by logarithm-antilogarithm calculation using an OP amplifier is superior in terms of accuracy and ease of constant design.

However, since it is necessary to use a plurality of OP amplifiers for the video signal band, there is a problem that the circuit size is large (and the cost is also high).

An object of the present invention is to provide a circuit that realizes a power circuit using logarithm-antilogarithm calculation with a simple configuration and easily performs γ correction.

[Means to solve the problem]

The above purpose is to reduce the VBE of a diode or transistor.
This is achieved by constructing a logarithm-antilogarithm circuit using the characteristics.

That is, a current Ii proportional to the input signal level is passed through the diode constituted by the first transistor, and the resulting change in the base-emitter voltage vngt is multiplied by a proportionality coefficient γ to obtain the second
It is coupled to the base-emitter voltage VBE2 of the transistor, and causes the emitter current IK2 of the second transistor to flow in response to changes in this VB)ti2.

Generally, as a type of such a configuration, there is a current mirror circuit corresponding to the case where γ=1. However, 1. The normal current mirror circuit is VBI! ! 1. The operation is based on VBE2.In contrast, in the present invention, VBEI←VBI
It has a circuit configuration that consciously creates state 2.

Actively utilize the circuit operation in that state. Therefore, the technical means of the present invention is different in function and purpose from the current mirror circuit.

[Effect]

A current proportional to the input signal level Ii+collector current of the first transistor &Ic1. IEI emitter current
+For simplicity, let's set the current transfer rate to 1 in α.

l1=IC! IEI Isl: Reverse saturation current D: Electron charge A: Boltzmann constant T: Absolute temperature. In normal operation, (1 (the exponent term in the parentheses of the equation is a large value compared to 1).

Too (can be done.

On the other hand, similarly for the second transistor, Io: Collector'm flow of the second transistor (Igz) I32: Reverse saturation 1! A flow is established.

The present invention VBE2”r VBEI Torto, (1
1. (2) Formula Kara) VI! E2 ■. Middle engineering 52LI-pAT AT γ = (ISl gq) IS2 ・l511
-'Medium Ii ・(Is24st) -1
It will be 31.

(3 (In formula, ISI and I82 are constants, and from formula (3) in parentheses, it can be seen that ■□ is proportional to Ii to the r power, and becomes the power of the input signal.

〔Example〕

EMBODIMENT OF THE INVENTION Below, one embodiment of the present invention will be described in detail using the drawings.

FIG. 1 shows the circuit configuration of γ>1, which is a first embodiment of the present invention. Specifically, this is a circuit corresponding to γ=2.

The circuit is input terminal 1.1 of Ig! Source 2. First transistor3. Second transistor4. Resistance 5. Voltage output terminal 6
．． It is composed of a diode 7, a power supply 8, and a power supply terminal Zoo.

Let the signal voltage input to input terminal 1 be i. Current source 2
It is assumed that a current I that can be varied by the input voltage Vi and is proportional to t flows. The transistor 3 is used as a diode by connecting its base and collector, and its emitter is connected to a power supply via a diode 7.

The base collector is connected to the base of transistor 4. The emitter of this transistor 4 has a potential difference ■1 power source 8
The collector is connected to the power supply 100 via the resistor 5, and the collector is grounded via the resistor 5. A voltage is generated in the resistor 5 due to the collector current of the transistor 4, and this is the output voltage V. Close terminal 6
Output from.

For the sake of simplicity in the circuit shown in FIG. 1, all transistors and diodes have the same current/voltage index characteristics, and therefore the reverse saturation currents in PN junctions of the same area are all expressed equally by Is. Since the base-emitter voltage of transistor 3 and the forward voltage of the diode are equal, this is VBK.
Let I be the base-emitter voltage of transistor 4, and let V be the base-emitter voltage of transistor 4.
Blli2 and the collector current is IO (.Assuming that the emitter sizes of transistors 3 and 4 are equal,
Since l31=IS2=Ij, (11, (2
) formula becomes, and from the configuration shown in Fig. 1, 2VBE1=Vτ2+VBE2...
・・・・・・・・・・・・(6) holds true. (4
1, (5), +61 to (7), is a constant, and the circuit shown in FIG. 1 is a power circuit with γ=2. Here, Is is a very small value (<1OA).

vr2=o(and in equation (7), 1 becomes 1 = Is-'> 10(A), which is a large value. This means that the function changes with respect to changes in Ii. The output Vo of the circuit is the product of this current factor and the resistance value of the resistor 5, and is expressed as Vo = RI o.Therefore, by providing an appropriately small shunt circuit for RY, It would be appropriate if you let a branch current flow.
The value of will be obtained. In the present invention, a power source 8 called vr2 is provided as another example.

That is, vr2 is a reference voltage for setting the proportionality coefficient to an appropriate value of 1, and is selected to be approximately VBEI so that the value of Kl is not too large. -For example, AT/pz2 at room temperature
When using a normal transistor of 6 mV, l5xlOA, Vr2-0 is required to obtain Kl ~l mA.
．． It is about 718V. Of course, the value of Vr2 is a design matter.

It is obvious that other values may be used in consideration of the emitter size ratio of the actual transistor.

FIG. 2 shows a circuit configuration for γ<1, which is a second embodiment of the present invention, and specifically corresponds to γ=0.5.

A power supply 9. connected to each emitter of a transistor 3.4 in the circuit shown in FIG. The arrangement of the diode 10 is opposite to that of the diode 7 and the power supply 8 connected to the respective emitters of the transistors 3 and 4 in FIG. These power supplies 8, 9. Except for the arrangement of diodes 7.10, the configuration shown in FIG. 2 is the same as in FIG. 1.

In FIG. 2, as in FIG. 1, it is assumed that all transistors have the same characteristics. The potential difference of the power supply 9 is Vτ
1. The forward voltage of the diode 10 is assumed to be equal to the base-emitter voltage VBI2 of the transistor 40. (41
, (Equation 51 holds true in Fig. 2 as well.

Also, from the configuration shown in FIG.

Vnxl+Vn=2VBK2==-
(Get 81.

In equation (9), 2 is a constant, and the circuit shown in FIG.
= 1/2 power circuit. Here, Vrt is a reference voltage for setting the proportionality constant to an appropriate value of 2. If <to A, then when Vrl = O.

K2=I<10' (A+), which is a very small value. Therefore, Vrl should be designed to be approximately vnzt so that the value of 2 is not too small. Of course, if 2 is not an extremely small value, it is necessary to increase the resistance value of the ξ output resistor 5 on the same side as explained in FIG. Increase the size to L
It is also possible to increase the Note that, as will be described later, Vrl (and therefore Vrz as well) is not just a power source (a configuration in which it has a temperature coefficient is practical).

FIG. 3 shows a third embodiment of the present invention.

In the circuit configuration shown in FIG. 3, the configurations indicated by reference symbols 1 to 6 are the same as those in FIGS. 1 and 2.

However, the emitter of the transistor 3 shown in FIG.
1□-1, and a power supply 9 are connected to a circuit power supply terminal 100 via series. Also, the emitter of transistor 4 is a diode 201 with one loop shown by the quotation mark 201.
1 to 201a-1- and the power supply 8 are connected to the circuit power supply terminal 100 via series.

Also in the circuit shown in FIG. 3, equations (41 and (51) hold true.

Also, mVng on the emitter side of transistors 3 and 4
t + Vrx = nVnz + Vrz
--°°-6o1 holds true. (41, (51, (t
Obtain from the o1 expression.

In equation (11), 3 is a constant! The circuit shown in FIG. 3 is a power-law circuit of y=m/ls. here,
Vrl*v1 is a reference voltage for setting the proportional constant of 3 to an appropriate value.

V, 1-Vr2 (ts-IF ri VBEI =
-... = Designed to satisfy C121. In addition,
In Figure 3, le = 1°m; 2. If we set vrl20, it is equal to the first factor, or ru2, 711=l, V,=0
, it becomes equal to Figure 2.

FIG. 4 shows a fourth embodiment of the present invention.

The configuration shown in FIG. 4 is similar to that of the first
The configuration is the same as that shown in the figure. That is, in FIG. 4, the base and collector of the transistor 30 are connected to the circuit power supply terminal 100 via the resistor 11.

The difference from FIG. 1 is that the potential difference between the base collector and the circuit power supply Vcc is divided by a resistor 11 and applied to the base of the transistor 4.

@ In Figure 4, the value Rv of resistor 11 is sufficiently thick compared to the resistance values of the emitter of transistor 3 and diode 7 (on the contrary, the resistance value is small enough that the voltage drop due to the base current of transistor 4 does not become a problem). (about IK~I
(approximately OKΩ), then in transistors 3 and 4 (
41, (Equation 51 holds true. Therefore, in the configuration of FIG. 4, the '1 voltage ratio ftt of the resistor 11 is set as (1-t). t, on the base and collector side of transistor 3 (1-
t) voltage division ratio. )At this time.

(2VBE1) 8t = VBE2 +Vrz
°゛°゛°°°゛° (obtains I31. (41,
(It comes from formulas 51 and 411.

In the formula G4), 4 is a constant, and it can be seen that FIG. 4 is a power circuit with r=2t. When O<t<1, γ changes continuously. However, since 4 changes depending on the value of t, by changing Vr2 together with t, it is possible to keep 1 (4) at the constant h value.

Note that it can be easily inferred that a diode should be added to the emitter side of the transistor 3 in order to make the width variable and thick.

Further, in the region of t where (1-2t)>O, the polarity of the power source 8 is reversed in order to keep 4 at an appropriate value.

It can be easily inferred that this is equivalent to a configuration in which, for example, the power supply 9 is inserted in common on the anode side of the diode 7 and on the power supply terminal 100 side of the resistor 11.

FIG. 5 shows a specific configuration example of an embodiment of the present invention. FIG. 5 is a circuit specifically showing the power supply 9 and current source 2 shown in FIG. It's exactly the same.

A diode 18 as shown by a one-dot line frame 9 in FIG.
．． A resistor 14 and a capacitor 15 constitute a 'llll source 9. Further, as shown by a dotted line frame 2, a current source 2 is configured by a transistor 12 and a resistor 13.

In Fig. 5, the resistor 14 is made relatively small and the diode,
The current flowing through the diode 18 is increased to reduce changes in the terminal voltage of the diode 18 due to changes in the current rA2. Capacitor 15 is for smoothing. Diode 18 connects other transistors 3, 4 . and diode 10 as well as approximately 12
rILv/da! Since it has a temperature coefficient of I, temperature changes in a portion of the current mirror made up of these transistors and diodes are reduced.

To offset the temperature coefficient of the transistor 12 that constitutes the current source 2, it is possible to compensate for the temperature of a part of the current mirror, but the previous stage circuit is designed to have a DC partial pressure temperature coefficient of the signal applied to the base. is normal. This method is a different technology from the circuit described in this embodiment and is omitted in this embodiment.

Using the same concept as in Fig. 5, the power supplies 9 and 8 shown in Fig. 3 are
can also be configured using diodes in series. That is, as shown in FIG. 86, transistor 3. transistor 4
The number of diodes connected to each emitter of is equal to N, and the remaining diodes 101r after subtracting m-1 diodes 1001~□-1 connected to the transistor 3 side from N diodes 101rIL~N are N-71t+1. The power supply 9 is configured as shown in FIG. Similarly, the power source 8 is composed of the remaining N-a+1 diodes after subtracting n-1 of the N diodes connected to the transistor 4. In this way, the potential difference vrl obtained by the diode 101F7L-N and the potential difference V? obtained by the diodes 201+s to N? ``2'' satisfies the set, and the temperature characteristics of a part of the current mirror are also compensated.

Above, one embodiment of the circuit configuration of the present invention has been described in detail. Although the above embodiment is a basic form, it is possible to consider a modified configuration.

FIG. 7 shows a seventh embodiment.

The circuit shown in FIG. 7 is almost the same as that in FIG.
Connect to 0.

Let the emitter current of the transistor 3 be II, and the current flowing through the resistor 19 be F2. Regarding transistor 4 (
5) Equation holds true, and holds true for transistor 3. Furthermore, if the resistance value of resistor 19 is &Rb, then Vrl+VB
E1 = RbI2 = 2Vng2...------
-6s) 11 + I2 = Ii ・
・・Scream・・Shout・・・・・・(Obtain 1 power.

(In the formula I, 5 is a constant, and therefore, Δ is proportional to the square root of the collector current 1i flowing through the transistor 3.

Here, 11 is not necessarily proportional to Ii. (41, (+
51.

(lee, (ry1 expression It is. It is impossible to solve equation (+9) algebraically.

In the range where the approximation holds true, I 1 "m I i, and the circuit shown in FIG. 7 becomes a power-law circuit.

- In the range of 2 and 1i.

Therefore, it becomes an exponential characteristic. Since the above characteristics change depending on the value of Rh, it can be seen that the characteristics of the circuit shown in FIG. 7 can be varied by the resistor 19.

Note that other methods of connecting the resistor 19 are possible, but all of them can be considered as applications of the present invention.

That is, the connection shown in FIG. 8 is almost the same as in FIG.
Shows power-of-1 characteristics.

Figure 8 has almost the same configuration as Figure 1, but the power supply 80 connected to the emitter of transistor 4 in Figure 1 is replaced with a parallel circuit of diode 10 and resistor 19 in Figure 8. . Similar to the explanation in FIG. 7, in the range where the value Rh of the resistor 19 is larger than the resistance value r of the diode 10, more current 1i flows toward the diode 10 and the resistor 19 can be ignored. The circuit is I 6 + I i
It is just a current mirror circuit. However, in the range where RA is equal to or less than r, there is no problem. Inside' I□r (γ〉
1) K゛: Indicates the characteristics of a constant. γ is a constant including R and 6.

As with the solution to equation (19), it cannot be expressed by a simple equation.

9 has almost the same configuration as FIG. 2, but the power supply 90 connected to the emitter of the transistor 3 in FIG.
In the figure, the configuration is replaced with a parallel circuit of a diode 7 and a resistor 19. Similarly to the explanation of FIG. 8, in the region where the resistance value Rh of the resistor 19 is equal to or less than the resistance value r of the diode 7, KIi'(r<1) in Ia exhibits the characteristic of K=constant. Although it is a constant containing.

It cannot be expressed by a simple formula.

Although the present embodiment has been described above using a current mirror circuit using a PNP transistor, an embodiment using an NPN transistor is also possible.

Figure 10 shows part of the current mirror (NPN) transistor 2
10th illustrating an embodiment of the present invention composed of 3 and 24.
The circuit shown in the figure has the same power-law characteristics as the circuit shown in FIG. The circuit configuration is the same as in Fig. 1, with large terminals 1. Current source 22. Transistors 23, 24, resistor 25, output terminal 6. Diode 27. It is composed of a power supply 28 and a circuit power supply terminal 100. It differs from the sg1 diagram in that NPN transistors are used for the transistors 23 and 24 in the current mirror section, and that the polarity of the signal applied to the input terminal 1 is opposite to that of the signal input in Figure 1. All other operations and characteristics are the same as the circuit shown in FIG. 1, and will therefore be omitted.

Regarding other figures 2 to 9, some of the current mirrors are NPN.
) A configuration using transistors is possible.

Its characteristics are hardly the same as those using a PNP transistor.

FIG. 11 shows an embodiment of a monochrome imaging device to which the circuit of the present invention is applied. The imaging device is an imaging unit 30. Preamplifier 3
1. Clamp circuit 32. γ correction circuit 33. Blanking/sync mix circuit 34. It consists of a video output terminal 35.

The signal from the imaging unit 30 is amplified by a preamplifier 31, a DC component is set by a clamp circuit 32, and then γ correction is performed by a γ circuit 33 of the present invention. Thereafter, a necessary blanking pulse is added and outputted from the terminal 35. Assuming that the signal will be reproduced with a γ medium 2.2 cathode ray tube, the r-
A reverse correction of 4=0.45 is performed.

Approximately, it is possible to use the embodiment of FIG. 2 where γ=0.5 as the γ correction circuit. More precisely, Figures 3 and 4
According to the present invention, the number of components of the γ circuit is smaller than in the past (and it is also easy to integrate into an IC).

FIG. 12 shows an embodiment of a color imaging device to which the circuit of the present invention is applied.

Complementary color signals cyan (Cy) and yellow (Ye) from the imaging unit 40
, edge (Gr), and white (G) are output, which are converted into primary color signals R, G, and BK by a matrix circuit 42, and then subjected to γ correction by six γ circuits 43a, h, and c of the present invention. After the correction, the image conversion processing circuit 44 converts the signal into a composite image signal, and outputs the signal from the terminal 45 as well. γ circuits 430-b in FIG. 12 are the same as γ circuit 33 in FIG. It is also possible to perform matrix conversion after applying the correction of the accent i and γ to the complementary color signals CY*Ye, Or and the white signal W.

813 shows the circuit of the present invention? For example, a composite video signal of the NTSC system is inputted to an input terminal 50, which shows a part of the video signal processing in the monochrome image display device used. A 3.58 MHz removal circuit 51 removes color components from the composite video signal, and then a γ circuit 52 performs γ correction.

Furthermore, the signal processing circuit 53 provides brightness and contrast.

The image quality etc. are adjusted and output from the terminal 54.

In the NTSC system, the γ of the video signal is approximately 0.45.

If the display section after the terminal 54 is a cathode ray tube, the characteristic of the γ circuit 52 in FIG. 13 is 1 in r. but.

If the display section after the terminal 54 is an EL or plasma display panel, it is necessary to change the characteristics of the γ circuit 52 accordingly.0 For normal EL and plasma panels, γ is 1, so the γ circuit 52 has a It is preferable to adjust the characteristics to r JF2.2.

FIG. 14 shows an example of applying the γ circuit of the present invention to a color image gI display device.

A composite video signal is input to the terminal 60, and the C, Y separation circuit 61
The luminance signal Y, which is separated into a chroma signal C and a luminance signal Y, is passed through a γ circuit 62 for γ correction, and is applied together with the chroma signal C to a color signal processing circuit 63. In this way, primary color signals R, G, and B are formed by the one-color decoding processing circuit 63,
It is output from terminals 64α to 64C.

The circuit configuration shown in FIG. 14 is simple.

The luminance signal Y deviation is γ-corrected, and as a result, the primary color signal R,
The configuration is such that γ correction is also performed on G and B. This is effective when the display characteristics of each color are the same in the display section after the terminal 64.

FIG. 15 shows an example of applying the γ circuit of the present invention to a color image display device.

A composite video signal is input to the terminal 70, and the C, Y separation circuit 71
The color signal processing circuit 72 forms primary color signals R, G, and B based on the luminance signal Y separated by 0 and the chroma signal C, which are separated into a chroma signal C and a luminance signal Y.

In FIG. 15, switches 73α to 73C are provided to switch between the external primary color signals applied to terminals 76α to C and the primary color signals from the color signal processing circuit 72 described above. Switched primary color signal P
K: γ correction through r circuits 740 to C.

Terminals 75α to C also output. In FIG. 15, correct correction is possible because γ correction can be performed in accordance with the characteristics of the display unit that displays each RGB color signal.

〔Effect of the invention〕

According to the present invention, it is possible to configure a power-law circuit by simply combining a diode and a resistor with a simple current mirror circuit without using an operational amplifier, etc., and it is possible to perform gamma correction of a video signal easily at low cost and compactly. It has the effect of being able to do the following.

Furthermore, this circuit not only can be constructed with a small number of discrete components (it can also be constructed only with diodes, transistors, and resistors), but it also has the advantage of being easy to integrate into an integrated circuit.

Furthermore, the r value can be easily set by changing the number of diodes and the way the resistors are connected.
The present invention has the advantage that it can be easily applied to a γ circuit of a solid image display device.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram in the case of r=2, which is the first embodiment of the present invention, and FIG. 2 is a circuit configuration diagram in the case of r = 0, which is the second embodiment of the present invention.
．． 5 is a circuit configuration diagram of the third embodiment of the present invention in which r is an arbitrary fraction. FIG. 4 is a circuit diagram of the fourth embodiment of the present invention in which γ is an arbitrary fraction. Circuit configuration diagram for the case,
Figure 5 is a more specific circuit configuration diagram that includes temperature compensation in Figure 2, Figure 6 is a circuit configuration diagram showing an example of the circuit configuration that includes temperature compensation in Figure 3, and Figures 7 to 9. is the first. A circuit diagram showing the second embodiment in a different configuration, FIG. 10 is a circuit diagram using NPN in the embodiment of FIG. 1, and FIG. 11 is a configuration of a monochrome imaging device to which the present invention is applied. A block diagram showing an example; FIG. 12 is a block diagram showing a configuration example of a color imaging device to which the present invention is applied; FIG. 13 is a block diagram showing an example of video signal processing in a monochrome image display device to which the present invention is applied; FIGS. 14 and 15 are block diagrams showing examples of video signal processing in a color image display device to which the present invention is applied. 2... Current source, 3, 4... Transistor. 7, lO...diode, 5...resistance. 8.9...Power supply.

Claims (1)

[Claims] 1. A current source whose current is controlled according to an input signal; a diode-connected first transistor connected in series with the current source and whose collector and base are commonly connected; a second transistor of the same conductivity type as the first transistor and whose base is connected to the base of the first transistor; and an emitter of at least either the first transistor or the second transistor. and at least one or more diodes or batteries provided between the transistor and a common potential, and an output signal that is a power value of the input signal is extracted from the collector of the second transistor. Power circuit. 2. In the power-law circuit according to claim 1, the connection between the base of the first transistor and the base of the second transistor is cut off, and a resistor is provided between the base of the first transistor and the common potential. , and a dividing point of the resistor is connected to the base of the second transistor.