JPH01202003A - Current detecting circuit - Google Patents

Abstract

PURPOSE:To detect the existence of current flowing into a primary side of a pair of current mirrors by using two complementary current mirrors connected in series, two constant current circuits for driving the output sides of the current mirrors and a detecting circuit for detecting the existence of outputs from the constant current circuits. CONSTITUTION:The title circuit is provided with the two current mirror circuits 2 consisting of complementary transistors allowed to flow current to be measured to the input side and connected in series, two current output type and current attracting type constant current circuits 3, 4 for driving the output sides of the circuits and detectors 5, 6 for detecting the existence of the outputs of the circuits 3, 4. The primary and secondary sides are separated from each other by the high impedance outputs of the current mirrors in AC and are equivalent to the separation of both the sides in DC because the inflow current form the secondary side to the current mirror pair 2 is equal to outflow current. Thus, the existence of current flowing into the primary side can be detected by potential detecting circuits 5, 6 for detecting the potential on both the ends of resistors 9, 10 inserted into the emitters of the current mirrors 3, 4.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a current detection circuit, and particularly to a current detection circuit between circuits that do not have a close potential relationship with each other.

[Conventional technology]

Conventionally, when detecting current between circuits that have a certain potential relationship with each other, I is shown in Fig. 46, and for Naisho No. 1, a photocoupler, etc. for 1. For current signals, it is common to use transformers, etc.However, each of these methods mediates a physicist's association of light, magnetic flux, etc., and transfers energy signals. , It was difficult to make the circuit into a dumb one. An example of fully integrated circuits is the use of a heater using wave number resistance and a differential capacitor that detects the entire temperature gradient on the chip. The drawback was that the response speed was slow.

[Problems that the invention attempts to solve] As mentioned above, the conventional current detection circuits all mediate all physical phenomena other than electricity, so it is difficult to realize the results as described above. At the same time, it has drawbacks such as slow response speed.

In contrast to the above-mentioned conventional detection means, the present invention utilizes separation using a high output impedance of a constant current source, and uses a circuit configuration independent of the primary and secondary potential relationship. The difference is that the detection circuit can be implemented by IA.

[Means to solve the problem]

The current detection circuit of the present invention has one to be measured on the hexagonal side! 211 by complementary transistors connected in series with each other carrying current.
! 10 power-re/tomirror circuit and this output ul! A current detection circuit comprising two constant current circuits of a current field type and a current absorption type driven by I, and a detector for detecting the presence or absence of the constant HL current circuit. It is composed of

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a circuit diagram showing the configuration of a first embodiment of the invention. Here, the dashed line 11111 on the left (one circuit is operated by the voltage 12fftE1, and the secondary side circuit on the right is operated by the vL source E2.The power supply voltage of each n is in the relationship Vl<V2 Assume that the voltage source E1 causes I to flow into the load l, and the voltage source E1 flows into the load l, so that the voltage source E1 flows into the load l,
The impedance on the secondary side decreases. At this time, the emitter potential Ec of the current mirror pair 2 is the potential E of the secondary circuit. If the relationship Eo<Eo×EY holds for Ev and Ev, the current mirrors 3p and 4 will operate. Here, 1 current value I of this current mirror 3 and 4
By setting st''It>I, all of these current mirrors can operate in a high impedance state with a constant TL flow source.

As a result, the primary side and the secondary side are separated from each other by the high impedance state of this current mirror in terms of current transformation, and the current flowing into and out of current mirror pair 2 from the secondary side in terms of DC. Since they are equal, it is equivalent to being separated. At this time, the presence or absence of a current flowing to the 91st primary side can be detected by potential detection circuits 5 and 6 that detect the potentials across the resistors 9 and 10 inserted into the emitters of the current mirrors 3 and 4.

Note that when no current flows through the primary side, the current mirrors 3 and 4 are saturated and the impedance decreases, but at this time the primary side circuit is in an OFF state, so this decrease in impedance does not pose a problem. Further, 8, 11, and 12 are current setting resistors, and 13 and 14 are backflow prevention diodes.

Next, consider the case where the EC potential is higher than Ev.

At this time, assuming that this potential difference is constantly provided by the power source E3, the current mirror 3 is cut off due to the potential relationship, and the overflow on the secondary side is caused by the current mirror bear 2.
current me)-4. flows through a loop to source E3 and current mirror pair 2. At this time, current detection on the primary side is performed only by the voltage detector 6, lOther than this, the primary and secondary separation characteristics are E. This is the same as the case of <Ec<Ev (7). Furthermore, Eo is E. From the same consideration, even when the voltage is low, it is possible to detect the primary side current by the voltage detector 5 while realizing the primary and secondary components. If an OR circuit is provided at the output of the voltage detectors 5 and 6 at 1:00 as in the first section, detection independent of the potential of Eo becomes possible.

Now, let's move on to the 70s without electrical connection between the primary and secondary sides.
-Ting-shaped mt-Think. At this time, the potential of EC is E,
The voltage obtained by proportionally distributing EoO9 with the output impedances t3 and R14 of current mirrors 3 and 4, that is, Ec = (13 ”'G”'14 ・EV) / ('13
”'t4). This is the above E.<Eo<EYoH
falls under the association.

From the above explanation, it can be seen that the present circuit configuration allows the primary side and the secondary side to be separated, and it is possible to output the primary side current regardless of the mutual potential relationship between the secondary circuits.

FIG. 2 shows a second embodiment of the invention. In this embodiment, transistors 23 and 24'5 are added to the current mirrors 21 and 22, which operate as foot current sources, to detect the presence or absence of an output current value.

When a current is flowing through the output of the current mirror, a current having the same magnitude as the current mirror output flows through the collectors of the transistors 23 and 24, but when the current becomes O, this value decreases significantly. By detecting this decrease with the detectors 25 and 26, the presence or absence of the primary side current of the ↓9 current mirror pair 2o can be detected.

Fig. 3 shows a 43rd embodiment of the present invention. Here, the current mirror pair 2 is substituted for the current mirror pair 2 or 20 in the embodiment of I ear 1:&-L 42.
By connecting the current mirror pairs 30 and 31 in antiparallel, it is possible to detect a situation where a variable current flows on the primary side. *J4 diagram shows current mirror pair 2 or 20 to Lte M08 FET 40~4
This is an example of 7'jJ4 using 3t''. Also, FIG.
This is an example in which 0 is adopted. Although all of these embodiments can be integrated through normal LSI manufacturing processes, great effects can be obtained especially by using a dielectric isolation process that does not generate parasitic elements between elements.

〔Effect of the invention〕

As explained above, there are two complementary current mirrors connected in series as shown in FIG. By using the 2m side circuit, which is operated by a voltage source independent of the primary side, the presence or absence of current flowing in the primary side of the current mirror pair allows the primary side to be in a high I/P/S state. You can see the effect of being able to make beautiful rows while maintaining fc.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing the configuration of a gl embodiment of the present invention, and FIG.
Fig. 7J < circuit diagram,
FIG. 6 and FIG. 7 are circuit diagrams showing an example of a current output circuit according to the prior art. l...Negative us 2...Current mirror pair, 3...Current output type current mirror,
4...Current absorption type current mirror, 5.6.
...Voltage detector, 7...OR circuit. Agent Patent Attorney Shinka Uchihara Figure 3

Claims (1)

[Claims] Two current mirror circuits are connected in series with each other to pass the current to be measured on the input side, two constant current circuits of a current output type and a current absorption type are driven by the output side, and A current detection circuit comprising: a detector for detecting the presence or absence of an output from a current circuit.