JP3332117B2 - DC current detector - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a direct current detector for monitoring a direct current output from, for example, a communication device power supply device.

[0002]

2. Description of the Related Art Generally, a DC current detector used for monitoring an output current of a power supply device for a communication device has a configuration as shown in FIG. In FIG. 4, reference numeral 1 denotes a high-voltage detected current line, and a primary winding n1 of a saturable transformer 2 is interposed in the line 1. This supersaturated transformer 2 is B
The first and second secondary windings n21 and n22 are connected in series using a saturable core T having a square characteristic of -H (magnetic flux-magnetic force) curve. Both secondary windings n21, n
The connection point between 22 is grounded via the resistor 3.

The current generated in the first secondary winding n21 is given a time constant by the inductor 4 and the capacitor 5 and supplied to the monitor (current / voltage conversion) resistor 6. Also,
The second secondary winding n22 is turned on / off by a pulse voltage supplied from a pulse power supply 7 via a diode 8.

That is, the primary winding n of the saturable transformer 2
When a current (current to be detected) flows in the direction of the arrow in FIG.
An AT product equal to the AT product (ampere turn) of the primary winding n1 is generated in the first secondary winding n21.

Therefore, this DC current detector applies a pulse voltage to the second secondary winding n22 and drives it on / off, thereby repeatedly resetting the saturation of the core T,
A current having a rectangular waveform is continuously generated in the first secondary winding n21. Then, this current is converted into a DC current by the inductor 4 and a DC voltage is generated in the monitor resistor 6 while being smoothed by the capacitor 5.

Here, when the current flowing through the line 1 increases or decreases, the non-saturation time of the core T changes. As a result, a current is generated in the first secondary winding n21 in accordance with the turn ratio with respect to the primary winding n1, so that the voltage generated in the monitor resistor 6 is proportional to the change in the DC current flowing through the line 1. Therefore, the DC current flowing through the line 1 can be measured by looking at this voltage.

However, in the conventional DC current detector using a saturable transformer as described above, when the ambient temperature changes, the BH curve square characteristic of the saturable core changes,
Since the saturation time changes, it has been difficult to detect the current with high accuracy.

[0008]

As described above, the conventional DC current detector uses a saturable transformer which is unstable with respect to a temperature change, so that it is difficult to detect the current with high accuracy. The present invention has been made to solve the above-described problem, and has as its object to provide a DC current detector capable of detecting a current with high accuracy without being affected by a temperature change.

[0009]

In order to achieve the above object, a DC current detector according to the present invention comprises: an AC transformer having a primary winding and a secondary winding having a predetermined winding ratio; , And both ends of the primary winding of the AC transformer are connected to one end of the current path to be detected via first and second switch elements, respectively, and the above-mentioned is connected via third and fourth switch elements. The primary winding is connected to the other end of the current path to be detected, and the set of the first and fourth switch elements and the set of the second and third switch elements are alternately turned on / off at a constant cycle. Path switching means for selectively interposing the current in the current line to be detected in a fixed cycle so that the direction of the current is reversed, and DC regeneration means for converting an AC current generated in a secondary winding of the AC transformer into a DC current. And is provided.

[0010]

In the DC current detector having the above configuration, the direction of the current to be detected flowing through the primary winding of the AC transformer is reversed at a constant cycle to generate an AC current in the secondary winding, and this AC current is converted into DC regeneration means. Then, a DC current having a ratio corresponding to a winding ratio between the primary winding and the secondary winding is generated from the detected current by converting the DC current into a DC current.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below in detail with reference to FIGS. FIG. 1 shows a configuration of a DC current detector according to the present invention, in which an AC transformer 11 using a ferrite ring core T is used. The AC transformers 11 are separated from each other, and each has a secondary winding n.
And the first and second primary windings n1 having a winding ratio of N: n to 2
1, n12.

On the other hand, the detected current line 12 is branched into two paths at the current detecting portion. A first primary winding n11 and a first switch element 13 are interposed in one path, and a second primary winding n12 and a second switch element 14 are interposed in the other system. They are interlaced.

The first and second switch elements 13, 1
Reference numeral 4 denotes, for example, a field-effect transistor whose on / off control is performed by a control signal from the logic circuit 15. The logic circuit 15 includes the switch element 1 described above.
Pulse signals P1 and P2 having a period T and a duty of 50% and having phases opposite to each other are supplied as control signals to 3 and 14, respectively.

The AC current generated in the secondary winding n2 of the AC transformer 11 is DC-regenerated by a DC regeneration circuit 16 using a diode bridge.
The voltage is converted into a voltage by a filter 7, smoothed by a smoothing circuit 18, and guided to a detection voltage output terminal 19 as a monitor voltage.

The operation of the above configuration will be described below with reference to FIG. Now, as shown in FIGS. 2 (a) and 2 (b), the logic circuit 15 generates pulse signals P1 and P2 having a phase opposite to each other and a duty of 50%, and the switching elements 13 and
14 is turned on / off, the first and second primary windings n1
A current I0 to be detected flows alternately between the first and n12. At this time, since the directions of the currents flowing through the windings n11 and n12 are opposite, an alternating current having an amplitude (N / n) I0 is generated in the secondary winding n2 as shown in FIG. 2 (c).

This AC current is full-wave rectified by a DC regeneration circuit 16 using a diode bridge, and is converted into a DC current Is (= (N / n) I0) as shown in FIG. This current is passed through a resistor 17 to be converted into a voltage, and then passed through a smoothing circuit 18 to be smoothed and output.
0 can be detected as the voltage Is.Rs as shown in FIG.

Accordingly, the DC current detector having the above-described configuration does not use the BH curve square characteristic of the saturable transformer, but takes out the DC current as an AC using a normal AC transformer and performs rectification and smoothing output. Since the output voltage is not affected by the temperature change, highly accurate current detection is possible.

FIG. 3 shows another embodiment according to the present invention. In FIG. 3, the same parts as those in FIG. 1 are denoted by the same reference numerals. In FIG. 3, reference numeral 21 denotes an AC transformer using a ferrite ring core T, which has a primary winding n1 and a secondary winding n2 with a turns ratio N: n. Primary winding n1
Are connected to the high potential side of the detected current line 12 via the switching elements 22 and 23, respectively, and are simultaneously connected to the low potential side of the detected current line 12 via the switching elements 24 and 25, respectively. Both ends of the secondary winding n2 are respectively connected to a pair of input terminals of the DC regeneration circuit 16 by the diode bridge.

Each of the switch elements 22 to 25 is constituted by, for example, a field effect transistor, and its on / off control is performed by a control signal from a logic circuit 26. The logic circuit 26 supplies pulse signals P11 and P12 having a duty of 50% and phases opposite to each other as a control signal to the set of the switch elements 22 and 25 and the set of the switch elements 23 and 24.

That is, since the set of the switch elements 22 and 25 and the set of the switch elements 23 and 24 are alternately turned on / off at the same cycle, the direction of the detected current flowing through the primary winding n1 of the AC transformer 21 is controlled. Switches at that cycle. Therefore, the secondary winding n2 of the AC transformer 21 has N:
n alternating currents are generated.

Therefore, as in the case of FIG. 1, the secondary winding n
2 is subjected to full-wave rectification by a DC regeneration circuit 16 using a diode bridge, passed through a resistor 17 and converted into a voltage, and then passed through a smoothing circuit 18 to be smoothed and output.
The detected current can be detected as a voltage.

In each of the above embodiments, FIGS.
As shown by the middle dotted line, if a bypass circuit composed of diodes D1 to Dn is connected to the detected current line 12, a set of switch elements 13, 14 or 22, 25 and 23, 24
Even if the set is turned off or damaged at the same time, it is possible to prevent the current supply to other circuits from being interrupted.

In each of the above embodiments, a DC current having a ratio corresponding to the winding ratio N: n of the AC transformer 21 can be generated from the detected DC current. For example, it can function as a DC current transformer. In addition, it goes without saying that various modifications can be made without departing from the spirit of the present invention.

[0024]

As described above, according to the present invention, it is possible to provide a DC current detector capable of detecting a current with high accuracy without being affected by a temperature change.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of an embodiment of a DC current detector according to the present invention.

FIG. 2 is a waveform chart for explaining the operation of the embodiment.

FIG. 3 is a circuit diagram showing a configuration of another embodiment according to the present invention.

FIG. 4 is a circuit diagram showing a configuration of a conventional DC current detector.

[Explanation of symbols]

1, 12 ... current line to be detected, 2 ... supersaturated transformer, 3 ...
Resistor, 4 inductor, 5 capacitor, 6 monitor resistor, 7 pulse power supply, 8 diode, 11, 21 AC transformer, 13, 14, 22 to 25 switch element,
15, 26: Logic circuit, 16: DC regeneration circuit, 17
... A resistor for current / voltage conversion, 18 a smoothing circuit, 19 a detection voltage output terminal, P1, P2, P11, P12 a pulse signal, I0 a detected current, Is a detected DC current.

──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tomoaki Asaoka 1 Komukai Toshiba-cho, Saiwai-ku, Kawasaki-shi, Kanagawa Prefecture Inside of Toshiba Komukai Plant (72) Inventor Kei Nakajima Komukai Toshiba-cho, Sai-ku, Kawasaki-shi, Kanagawa No. 1 Examiner, Tadashi Shinozaki, Komukai Plant, Toshiba Corporation (56) References JP-A-62-250704 (JP, A) JP-A-1-141368 (JP, A) JP-A-59-89269 (JP, U) ) Actually open sho 59-109293 (JP, U) Actually open hei 5-20245 (JP, U) (58) Fields investigated (Int. Cl. ⁷ , DB name) G01R 19/00-19/32 G01R 15 / 18

Claims (3)

(57) [Claims] An AC transformer having a primary winding and a secondary winding having a predetermined winding ratio, a current line to be detected is divided, and both ends of the primary winding of the AC transformer are first and second ends, respectively. Connected to one end of the current path to be detected via a switch element;
Of connected to the other end of the object to be detected current path through the switching device, to alternately turn on / off control at a constant period a set of pairs and the second and third switching elements of the first and fourth switching elements Path switching means for selectively interposing the primary winding in the detected current line so that the current direction is reversed at a constant period; and A DC current detector comprising: DC regeneration means for converting the current into a current. 2. An AC transformer having a primary winding and a secondary winding having a predetermined winding ratio, and a current line to be detected is divided to form a primary winding of the AC transformer.
At both ends via the first and second switch elements, respectively.
The third and fourth terminals are connected to one end of the detected current path.
To the other end of the detected current path via the switch element
Connected, and a pair of first and fourth switch elements and second and
3 sets of switch elements are turned on / off alternately at regular intervals
By Gosuru it, a path switching means for the direction of the current is selectively interposed as reversed at a constant period the primary winding during the detected current lines, alternating current generated in the secondary winding of the AC transformer A DC current detector comprising: a DC regeneration unit that converts a current to a DC current; and a bypass path that bypasses an intervening position of the primary winding in the detected current line. 3. The direct current detector according to claim 2, wherein a diode is interposed in the bypass path so as to be forward with respect to the current to be detected.