JP2000249727A - Current detection device and power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a current detection device capable of sensitively detecting a current flowing through a load without changing the current, and to provide a power supply device having no large loss without changing the current flowing through the load. SOLUTION: In this current detection device, detection windings wd1, wd2 of a transformer T are induction-coupled with a primary winding w1, and are connected in cascade such that electromotive forces mutually induced in the respective windings wd1, wd2 counteract each other. When a current transiently flows through the secondary winding w2, respective ends of the series circuit of the detection windings wd1, wd2 generate a voltage to turn on one of field effect transistors Q1, Q2 and to turn off the other according to a direction of the transient current, such that a voltage having prescribed polarity is generated between respective electrodes of output terminals of a rectification circuit. In the absence of a successive current in a load, both of the field effect transistors Q1, Q2 are turned off.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a current detection device and a power supply device.

[0002]

2. Description of the Related Art Techniques for detecting a current (a power supply current, a signal current, etc.) flowing through a load are widely used, and the detection result of the current is used for controlling a power supply device and a signal source. As a method of detecting the current flowing to the load, a method of providing a current transformer in a current supply path from the power supply to the load,
A general method is to insert a resistor having a sufficiently low resistance value into the current supply path.

In a method using a current transformer, a primary winding of a current transformer is inserted into a current supply path, and a signal having a magnitude proportional to a load current is extracted from a secondary winding of the current transformer. In the technique using a resistor, a load current is detected by inserting a resistor into a current supply path and measuring a voltage between both ends of the resistor.

[0004]

In any of the above-mentioned methods, the current transformer and the resistor themselves consume power, so that the magnitude of the current flowing to the load is different from the magnitude of the current that should originally flow. Value. For this reason,
In order for the effect of the current transformer or resistor on the current flowing to the load to remain within a negligible range, it is necessary to reduce the power consumption of the current transformer sufficiently and the resistance value of the resistor sufficiently .

However, in order to increase the sensitivity of the current transformer, it is necessary to increase the number of turns of the secondary winding of the current transformer. When the number of turns of the secondary winding of the current transformer increases, the power of the secondary transformer itself is reduced. The consumption increases, and thus the change in the current flowing to the load increases.

[0006] The voltage between both ends of a resistor inserted in a current supply path to a load increases in proportion to the resistance value of the resistor. However, the power consumed by the resistor also increases as the resistance value increases, so that the change in the current flowing to the load increases.

[0007] Further, the current transformer acts as an inductive load from the viewpoint of the current supply source.
Power is supplied to a series circuit of the inductive load formed by the current transformer and the load to be driven. Therefore,
The higher the frequency component of the current to be passed through the load, the more difficult it is to supply the load to the load, resulting in deterioration of the frequency characteristics of the current flowing through the load.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and has as its object to provide a current detection device capable of detecting a current with high sensitivity without changing a current flowing through a load. . It is another object of the present invention to provide a current detection device that can detect a current without deteriorating the frequency characteristics of the current flowing through a load. Another object of the present invention is to provide a power supply device which does not change the current flowing through the load and has a small loss.

[0009]

In order to achieve the above object, a current detecting device according to a first aspect of the present invention includes a primary winding and a secondary winding inductively coupled to the primary winding. A transformer and a pair of detection windings inductively coupled to the primary winding, wherein each of the detection windings cancels out an electromotive force mutually induced by a current flowing through the primary winding. They are connected in cascade in a suitable direction to form a series circuit, and each end of the series circuit forms a current detection end for detecting a current flowing through the secondary winding.

According to such a current detection device, the electromotive force induced in the detection winding is induced by the current flowing through the primary winding, and thus flows through the load connected between both ends of the secondary winding. The current does not substantially change, and the current flowing to the load is detected with a desired sensitivity. Further, according to such a current detection device, since a common current does not flow through the detection winding and the secondary winding, the frequency characteristics of the current flowing through the load do not deteriorate.

Further, a current detecting device according to a second aspect of the present invention is a current detecting device, comprising: a primary winding; and a secondary winding inductively coupled to the primary winding. And a pair of detection windings inductively coupled to the primary winding, wherein each of the detection windings is mutually induced by a current flowing through the primary winding. The generated electromotive forces are connected in cascade in a direction to cancel each other to form a series circuit, and each end of the series circuit forms a current detection end for detecting a current flowing through the secondary winding. , Characterized in that.

Also in such a current detecting device, since the electromotive force induced in the detecting winding is induced by the current flowing in the primary winding of the transformer, the electromotive force is connected between both ends of the secondary winding of the transformer. The current flowing through the load does not substantially change, and the current flowing through the load is detected with a desired sensitivity. Further, even with such a current detection device, since a common current does not flow through the detection winding and the secondary winding, the frequency characteristics of the current flowing through the load do not deteriorate.

A power supply unit according to a third aspect of the present invention is a power supply device in which a primary winding and a tap which is inductively coupled to the primary winding and forms one pole of an output terminal substantially at its midpoint. A secondary winding provided with:
A pair of detection windings that are inductively coupled to the primary winding and are connected in cascade in a direction that cancels out electromotive forces mutually induced by currents flowing through the primary winding to form a series circuit; A current path and a control end connected between one end of the secondary winding and the other pole of the output end, wherein each current path is substantially responsive to a signal supplied to its own control end. A first switching means for turning on and off the power supply, a current path and a control end connected between the other end of the secondary winding and the other end of the output end, and supplied to respective control ends. Second switching means for substantially turning on and off the respective current paths in response to the applied signals, and a predetermined polarity among the current paths of the respective switching means based on the voltage at each end of the series circuit. To the end of the secondary winding which is generating Determine whether there is what is,
Control means for supplying a signal to a control terminal of each of the switching means so that the current path determined to be connected is turned on and the other current paths are turned off.

According to such a power supply device, the interruption of the current path of the first and second switching means is determined based on the electromotive force induced in each detection winding. Since the electromotive force induced in the detection winding is induced by the current flowing in the primary winding of the transformer, the current flowing in the load connected between both ends of the secondary winding of the transformer is substantially It does not change. When a load is not substantially connected to the secondary winding of the transformer and a voltage of a predetermined polarity is not generated at any end of the series circuit, each of the first and second switching means Since all the current paths are turned off, the occurrence of power loss due to a leak current or the like is prevented.

The first switching means includes, for example,
It may be constituted by a first field-effect transistor having a drain, a source and a gate. In this case, for example,
A drain and a source of the first field-effect transistor form both ends of a current path of the first switching means;
The gate of the first field effect transistor may form a control terminal of the first switching means. Further, the second switching means may be composed of, for example, a second field effect transistor having a drain, a source, and a gate. The drain and the source of the second field effect transistor form both ends of a current path of the second switching means, and the gate of the second field effect transistor forms a control end of the first switching means. And it is sufficient.

The first and second switching means include:
When a signal for turning on its own current path is not supplied to its own control terminal and an electromotive force in a direction in which current flows in the secondary winding in a predetermined direction is induced in the secondary winding. ,
If it is provided with initial current passing means for temporarily passing a current to the secondary winding by bypassing its own current path, the primary winding is connected with a load connected between both ends of the secondary winding. By applying a single-phase AC voltage across the load, a rectified voltage is supplied to the load without requiring any other initialization procedure.

The initial current passing means may be, for example, a first switching means connected in parallel to a current path of the first switching means.
In parallel with the current path of the second switching means, and connected in such a direction that the forward current flowing through itself flows as the forward current of the first rectifier into the secondary winding. What is necessary is just to provide the 2nd rectifier, and the capacitor connected between both poles of the said output terminal.

[0018]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described.
A transformer and a rectifier circuit for detecting load current will be described as an example with reference to the drawings. (First Embodiment) FIG. 1 is a cross-sectional view schematically showing a cross section of a transformer T for detecting a load current according to a first embodiment of the present invention.

The transformer T has an iron core F as shown in FIG.
, A primary winding w1, a secondary winding w2, and a detection winding wd.
1 and wd2.

The iron core F is composed of, for example, an EI core as shown in the figure. The EI core, as shown,
The “E” -shaped core and the “I” -shaped core are combined so as to form a “day” shape.

The "E" -shaped core has a straight yoke 5
A pair of upper and lower outer peripheral legs 7 and 8 erected at both ends of the yoke portion 5 at right angles to the longitudinal direction of the yoke portion 5 so as to be parallel to each other and vertically opposed to each other; And a central leg 9 projecting in parallel with the outer peripheral legs 7 and 8 at the center. The “I” -shaped core is constituted by a linear yoke portion 6.

The primary winding w1, the secondary winding w2, and the detection windings wd1 and wd2 are, as shown in FIG.
It is wound around the central leg 9 of the letter-shaped core. Specifically, as shown in the drawing, the primary winding w1, the secondary winding w2, and the detection windings wd1 and wd2 have, as shown in the figure, the detection winding wd1, the primary winding w1,. Secondary winding w
2 and the detection winding wd2, and are wound around the central leg 9 so as to cover almost the entire surface of the central leg 9, respectively.

As shown in FIG. 1, both ends of the primary winding w1 form input terminals for supplying a power supply such as a commercial AC power supply. Both ends of the secondary winding w2 form, for example, an output end for supplying power to a load. One of two ends of each of the two ends of the detection windings wd1 and wd2, which generate voltages of the same polarity when an AC voltage is applied to the primary winding w1, is connected to each other. Is done. Another set forms a current detection terminal.

Next, the operation of the transformer T shown in FIG. 1 will be described.
When the detection load Zd is connected to both ends of the current detection terminal and a single-phase AC power supply voltage is supplied between the input ends of the transformer T (that is, between both ends of the primary winding w1), the primary winding w
1 generates a magnetic flux having the distribution shown in FIG.

As shown in the drawing, the magnetic flux generated by the primary winding w1 flows from one opening of the solenoid formed by the primary winding w1 to the other opening of the solenoid via the outside of the solenoid. After passing through the interior of the solenoid, it returns to one opening of the solenoid. Therefore, the magnetic flux generated by the primary winding w1 also passes through the inside of each of the solenoid formed by the secondary winding w2, the solenoid formed by the detection winding wd1, and the solenoid formed by the detection winding wd2.

Therefore, a voltage induced in the secondary winding w2 by the magnetic flux generated by the primary winding w1 is generated between the output terminals of the transformer T (that is, between both ends of the secondary winding w2). . This voltage becomes a single-phase AC voltage having an effective value proportional to the effective value of the single-phase AC voltage applied between the input terminals of the transformer T.

Further, a voltage induced in the detection winding wd1 by the magnetic flux generated by the primary winding w1 and a voltage induced in the detection winding wd2 by the magnetic flux generated by the primary winding w1 are provided between both ends of the current detection terminal. A voltage is generated that is substantially equal to the difference from the induced voltage.

Then, a current having a magnitude substantially proportional to the voltage between both ends of the current detection terminal flows through a closed circuit formed by the detection windings wd1 and wd2 and the detection resistor Rd. If a load including a pure resistance component is connected between the output terminals of the transformer T, a load current flows through the load and the secondary winding w2, and the load consumes power.

Then, the secondary winding w2 and the detection winding wd1
And wd2 are both determined by the current flowing through them.
Generates magnetic flux that cancels the magnetic flux generated by the next winding w1
Let it. That is, the secondary winding w2, the detection winding wd1, and the
And wd2 generate magnetic flux inside the central leg 9 of the iron core F.
The magnetic flux generated by the primary winding w1 is
Substantially opposite to the direction in which the heart F passes through the inside of the central leg 9
It is a direction. Then, primary winding w1, secondary winding w2, detection
The magnitude of the magnetic flux generated by the windings wd1 and wd2 for
And Φ₁, Φ₂, Φ_d1And Φ_d2Then Φ₁, Φ
₂, Φ_d1And Φ _d2Have the relationship shown in Equation 1.
You.

[0030]

Φ ₁ = Φ ₂ + Φ _d1 + Φ _d2

On the other hand, when the inside of a solenoid having the number of turns n, the radius r, and the length d is filled with a substance having a magnetic permeability μ, when a current having a size of I flows through the solenoid, a magnetic flux generated by the solenoid is generated. Is represented by Expression 2.

[0032]

Φ = (μ · n ² · π · r ² · I) / d

Accordingly, the number of turns of the primary winding w1, the secondary winding w2, and the detection windings wd1 and wd2 is sequentially set to n ₁ ,
and n _{2, n d1} and _{n d2,} primary winding w1, secondary winding w2, the radius of the detecting winding wd1 and wd2, in turn, r
_{1, r 2,} and _{r d1} and _{r d2,} primary winding w1, secondary winding w2, the magnitude of the current flowing in the detection winding wd1 and wd2, in _{turn, I 1, I 2, I} d1 and I _{Assuming d2} , the relationship shown in Expression 3 is substantially established. However,
Primary winding w1, secondary winding w2, detection windings wd1 and w
The length of each solenoid formed by d2 is assumed to be substantially equal to each other.

[0034]

Equation 3] ^{_{n 1 · r 1 2 · I}} 1 = {d / (μ · π)} · (L 1 · I 1 / n 1) = (n 2 · r 2 2 · I 2) + (n d1 ^{_{· r d1 2 · I d1)}} + (n d2 · r d 2 2 · I d2) = {d / (μ · π)} × {(L 2 · I 2 / n 2) + (L d1 · I d1 _{/ n d1) + (L d2} · I d 2 / n d2)} ( _{however, L 1, L 2, L} d1 and _{L d2,} the primary winding w1, the secondary winding w2, the detection winding wd1 and wd2 self-inductance)

A common current flows through the detection windings wd1 and wd2, and the common current is detected by the detection windings wd1 and wd2.
At d2, a magnetic flux is generated in such a direction as to cancel the magnetic flux generated by each other. Therefore, the relationship substantially expressed by Expression 4 is established.

[0036]

## EQU4 ## I _d1 = ｛(L ₂ · I ₂ / n ₂ )-(L ₁ · I
₁ / n ₁ )｝ ÷ ｛(L _{d 2} / n _{d 2} ) − (L _{d 1} / n
_d1 )｝

As shown in Equation 4, the current flowing through the detection windings wd1 and wd2 increases substantially in proportion to the amount of change in the load current flowing through the secondary winding w2.

The detection windings wd1 and wd of the transformer T shown in FIG.
Since the electromotive force induced in d2 is induced by the current flowing in the primary winding w1, the current flowing in the load connected between both ends of the secondary winding wd2 is equal to the detection windings wd1 and wd.
2 is not substantially changed by the current flowing through the switch. Therefore, by making the number of turns of the detection windings wd1 and wd2 sufficiently large, the secondary winding w2 can be formed with desired sensitivity.
Current flowing through a load connected between both ends of the load can be detected. Further, since the current flowing through the detection windings wd1 and wd2 does not flow through the secondary winding w2, the current flowing through the detection windings wd1 and wd2 deteriorates the frequency characteristics of the current flowing through the load. Things do not occur substantially.

(Second Embodiment) FIG. 3 schematically shows a configuration of a rectifier circuit according to a second embodiment of the present invention. This rectifier circuit includes a transformer T as shown.
, Field effect transistors Q1 and Q2, and resistor R1
And R2, and a capacitor C.

The transformer T has a midpoint tap ct connected to the midpoint of the secondary winding w2 in addition to the transformer in the first embodiment. Both ends of the primary winding w1 of the transformer T form an AC input terminal. One end of the secondary winding w2 of the transformer T is connected to the drain of the field effect transistor Q1, and the other end of the secondary winding w2 is connected to the drain of the field effect transistor Q2. The midpoint tap ct of the transformer T forms the positive terminal of the output terminal of the rectifier circuit.

The field effect transistors Q1 and Q2 are both n-channel enhancement type MOSFETs.
(Metal-Oxide-Silicon Field Effect Transistor) and has a gate, a source, and a drain.

The drain of the field effect transistor Q1 is
The secondary winding w2 of the transformer T is connected to one end of the secondary winding w2, and the drain of the field effect transistor Q2 is connected to the other end of the secondary winding w2 of the transformer T. The source of the field-effect transistor Q1 and the source of the field-effect transistor Q2 are connected to each other and form a negative electrode at the output terminal of the rectifier circuit.

The gate of the field effect transistor Q1 has one end of a secondary winding of the transformer T connected to the drain of the field effect transistor Q1 among the respective poles of the current detection terminal of the transformer T having a negative polarity. Is connected to the pole on which a positive voltage is generated. Field effect transistor Q2
Of the current detection terminal of the transformer T has a positive voltage when one end of the secondary winding of the transformer T connected to the drain of the field effect transistor Q2 has a negative polarity. Is connected to the pole where the occurrence occurs.

The capacitor C is for smoothing the voltage (rectified voltage) at the output terminal of the rectifier circuit, and is connected between the positive electrode and the negative electrode at the output terminal of the rectifier circuit.

The resistor R1 is connected to a field effect transistor Q1.
To supply a bias voltage to the gate of
It is connected between the gate and the source of the field effect transistor Q1. The resistor R2 is connected to the field effect transistor Q
2 for supplying a bias voltage to the gate of the FET 2, and is connected between the gate and the source of the field effect transistor Q1.

The resistance value of the resistor R1 is determined by a bias voltage that turns on the field effect transistor Q1 when a current flows through the capacitor C and / or the load connected between the two electrodes at the output terminal of the rectifier circuit. The value is selected to be sufficiently high so as to be applied between the gate and the source of the transistor Q1. The resistance value of the resistor R2 is determined by a bias voltage that turns on the field effect transistor Q2 when a current flows through the capacitor C and / or the load connected between the two electrodes at the output terminal of the rectifier circuit. The value is selected to be sufficiently high so as to be applied between the gate and the source.

When a single-phase AC voltage to be rectified is applied between both poles of the AC input terminal of the rectifier circuit, a voltage is induced between both ends of the secondary winding w2 of the transformer T by mutual induction. One end of the next winding w2 has a positive polarity with respect to the potential of the center tap ct of the transformer T, and the other has a negative polarity.

In order to facilitate understanding, the voltage at one end of the two ends of the secondary winding w2 which is connected to the drain of the field effect transistor Q1 is set at the midpoint tap c.
It is assumed that the potential becomes negative with respect to the potential t. In this case, from the source of the field effect transistor Q1, the secondary winding passes through the parasitic diode between the source and the drain of the field effect transistor Q1, the secondary winding w2 of the transformer T, the center tap ct and the capacitor C in this order. A current flows through the line w2.

Then, the voltage between both poles of the current detection terminal changes. As a result, the resistor R1 and the resistor R2 are connected from the pole of the current detection terminal which is connected to the gate of the field effect transistor Q1. In this order, the current that reaches the pole of the current detection terminal that is connected to the gate of the field-effect transistor Q2 increases. As a result, the field effect transistor Q1 in which the voltage between both ends of the resistor R1 is applied between its own gate and source is turned on, and the voltage between both ends of the resistor R2 is applied between its own gate and source. The field effect transistor Q2 is turned off.

Then, from the center tap ct of the transformer T,
A current flows through the secondary winding w2 so as to pass through the capacitor C, the source and drain of the field effect transistor Q1, and the end of the secondary winding w2 which is connected to the drain of the field effect transistor Q1 in order. .

At this time, when the load is not connected between both ends of the rectifier circuit, when the charging of the capacitor C is substantially completed, the current flowing through the secondary winding w2 substantially does not flow. Then, the detection windings wd1 and wd2
And the magnitude of the voltage drop across resistor R1 also decreases. As a result, the field effect transistor Q1 turns off. On the other hand, if a load is connected between both ends of the rectifier circuit, a current flows through the secondary winding w2 between the center tap ct of the transformer T and the drain of the field effect transistor Q1 even after the charging of the capacitor C is completed. Keeps flowing.

When the voltage of the end of the secondary winding w2 that is connected to the drain of the field effect transistor Q2 becomes negative with respect to the potential of the center tap ct, the electric field effect A current flows from the source of the transistor Q2 to the secondary winding w2 such that the current passes through the parasitic diode between the source and the drain of the field-effect transistor Q2, the center tap ct of the transformer T, and the capacitor C in this order.

Then, the voltage between both poles of the current detection terminal changes, and the pole of the current detection terminal, which is connected to the gate of the field effect transistor Q2, passes through the resistor R2 and the resistor R1 in that order. The current that reaches one of the two poles of the current detection terminal connected to the gate of the field effect transistor Q1 increases. As a result, the field effect transistor Q1
Turns off, and the field effect transistor Q2 turns on. Accordingly, from the source of the field effect transistor Q2 to the drain of the field effect transistor Q2, the midpoint tap c of the transformer T
A current flows through the secondary winding w2 so as to pass through the capacitor t and the capacitor C in this order.

At this time, when the load is not connected between both ends of the rectifier circuit, when the charging of the capacitor C is substantially completed, the current substantially does not flow through the secondary winding w2, and the electric field effect The transistor Q2 turns off. on the other hand,
If a load is connected between both ends of the rectifier circuit, the middle point tap ct−
Secondary winding w2 between the drains of field effect transistor Q2
Current continues to flow through.

In the rectifier circuit shown in FIG. 3, the electromotive force induced in the detecting windings wd1 and wd2 of the transformer T for generating a voltage for determining whether the field effect transistors Q1 and Q2 are on or off is equal to the primary winding w1. Induced by the current flowing through Therefore, the current flowing through the load connected between both ends of the secondary winding wd2 is not substantially changed by the current flowing through the detection windings wd1 and wd2.

Further, a load is not substantially connected to the secondary winding w2 of the transformer T, and a voltage is generated at any end of the current detection terminal so as to turn on the field effect transistor Q1 or Q2. If not, both the field effect transistors Q1 and Q2 are turned off. For this reason, the danger of consuming power due to leakage current between the drain and source of the field effect transistors Q1 and Q2 is prevented.

The configuration of the rectifier circuit is not limited to the above. For example, the field-effect transistors Q1 and Q2 are both p-channel MOS as shown in FIG.
It may be composed of an FET.

In the case of the configuration shown in FIG. 4, the source of the field effect transistor Q1 and the source of the field effect transistor Q2 connected to each other form the positive terminal of the output terminal of the rectifier circuit, as shown in the figure. In the gate of the field effect transistor Q1, one end of the secondary winding of the transformer T connected to the drain of the field effect transistor Q1 has a positive polarity among the respective poles of the current detection terminal of the transformer T. Sometimes it is connected to the pole where a negative voltage is generated. In the gate of the field effect transistor Q2, one end of the secondary winding of the transformer T connected to the drain of the field effect transistor Q2 has a positive polarity among the respective poles of the current detection terminal of the transformer T. Sometimes it is connected to the pole where a negative voltage is generated.

Between both poles of the AC input terminal of the rectifier circuit of FIG.
A single-phase AC voltage to be rectified is applied, and the voltage at one end of the two ends of the secondary winding w2 connected to the drain of the field-effect transistor Q1 has a positive polarity with respect to the potential of the center tap ct. Let's say In this case, from the secondary winding w2 of the transformer T to the drain of the field-effect transistor Q1, the parasitic diode between the drain and source of the field-effect transistor Q1, the capacitor C, and the midpoint tap ct of the transformer T
, An electric current flows through the secondary winding w2.

Then, the voltage between the two electrodes of the current detection terminal changes, and the resistor R2,
Through the resistor R1, the current that reaches the pole of the current detection terminal that is connected to the gate of the field-effect transistor Q1 increases. As a result, the field effect transistor Q
1 turns on, and the field effect transistor Q2 turns off. As a result, a current flows from the secondary winding w2 of the transformer T to the secondary winding w2 via the drain and source of the field effect transistor Q1, the capacitor C, and the center tap ct of the transformer T in order.

When a load is not connected between both ends of the rectifier circuit, no current substantially flows through the secondary winding w2 due to termination of charging of the capacitor C, and the field effect transistor Q1 is turned off. When a load is connected, current continues to flow through the secondary winding w2 between the midpoint tap ct of the transformer T and the drain of the field effect transistor Q1.

It is also assumed that the voltage at the end of the secondary winding w2 which is connected to the drain of the field effect transistor Q2 has a positive polarity with respect to the potential of the center tap ct. In this case, the secondary winding w2 of the transformer T passes through the drain of the field-effect transistor Q2, the parasitic diode between the drain and the source of the field-effect transistor Q2, the capacitor C, and the center tap ct of the transformer T in order. A current flows through the winding w2.

Then, of the two poles of the current detection terminal, the pole connected to the gate of the field effect transistor Q1 starts from
The current flowing through the resistor R1 and the resistor R2 in this order to the pole connected to the gate of the field effect transistor Q2 of the two poles of the current detection terminal increases, and the field effect transistor Q2
Turns on, and the field effect transistor Q1 turns off. As a result, a current flows from the secondary winding w2 of the transformer T to the secondary winding w2 through the drain and source of the field effect transistor Q2, the capacitor C, and the middle tap ct of the transformer T in order.

If the load is not connected between both ends of the rectifier circuit, the field effect transistor Q2 is turned off when the charging of the capacitor C is completed. Current continues to flow through the secondary winding w2 between the point tap ct and the drain of the field effect transistor Q2.

This rectifier circuit may have, for example, the configuration shown in FIG. The configuration of the rectifier circuit of FIG. 5 is substantially the same as the configuration of the rectifier circuit of FIG. 3 except as described below.

However, as shown in FIG. 5, the rectifier circuit includes a transformer T and field effect transistors Q1 and Q2.
, Resistors R1 and R2, and capacitor C,
It has bipolar transistors Q3 and Q4 and resistors R3 and R4. Each of the bipolar transistors Q3 and Q4 is formed of a PNP-type bipolar transistor, and has a base, an emitter, and a collector. Each of the field effect transistors Q1 and Q2 is composed of a p-channel enhancement type MOSFET.

In the rectifier circuit shown in FIG. 5, one end of the secondary winding of the transformer T connected to the drain of the field effect transistor Q1 has a negative polarity among the current detection terminals of the transformer T. The pole on which a positive polarity voltage is generated is connected to the base of the bipolar transistor Q4 instead of the gate of the field effect transistor Q1. Among the respective poles of the current detection terminal of the transformer T, one in which a positive voltage is generated when one end of the secondary winding of the transformer T connected to the drain of the field effect transistor Q2 becomes negative. Is connected to the base of bipolar transistor Q3 instead of the gate of field effect transistor Q2.

The collector of bipolar transistor Q3 is connected to the gate of field effect transistor Q1. The emitter of the bipolar transistor Q3 is a transformer T
Is connected to the center tap ct. The collector of the bipolar transistor Q4 is connected to the gate of the field effect transistor Q2. Bipolar transistor Q4
Are connected to the center tap ct of the transformer T.

The resistor R3 is connected to the bipolar transistor Q
3 is connected between the base and the emitter. The resistor R4 is connected between the base and the emitter of the bipolar transistor Q4.

The resistance value of the resistors R3 and R4 is determined by the value of the capacitor C and / or the capacitor C connected between both electrodes at the output terminal of the rectifier circuit.
Or, when a current flows through the load, the field effect transistor Q
Of the transistors 1 and Q2, the one that flows a current in the same direction as the current flowing to the capacitor C and / or the load is selected so that the bipolar transistors Q3 and Q4 are turned on by the operation described later.

Between the two poles of the AC input terminal of the rectifier circuit of FIG.
The single-phase AC voltage to be rectified is applied, and the secondary winding w2
It is assumed that the voltage of the end connected to the drain of the field effect transistor Q1 has a negative polarity with respect to the potential of the center tap ct. In this case, a current flows from the center tap ct of the transformer T to the secondary winding w2 through the capacitor C, the parasitic diode between the source and the drain of the field-effect transistor Q1, and the drain of the field-effect transistor Q1 in that order.

Then, the voltage between both poles of the current detection terminal changes. As a result, the resistor R4 and the resistor R3 are sequentially connected from the pole connected to the base of the bipolar transistor Q4 among the two poles of the current detection terminal. As a result, the current reaching the pole connected to the base of the bipolar transistor Q3 among the two poles of the current detection terminal increases. As a result, the resistor R3
Is applied between its base and emitter, the bipolar transistor Q3 is turned on, and the resistor R
The bipolar transistor Q4, which is applied with the voltage between both ends of the transistor 4 between its own base and emitter, is turned off.

Then, from the center tap ct of the transformer T, the emitter and the collector of the bipolar transistor Q3, the resistor R1, the parasitic diode between the source and the drain of the field effect transistor Q1, and the drain of the field effect transistor Q1 in this order. A current flows through the next winding w2. As a result, the field-effect transistor Q1 in which the voltage between both ends of the resistor R1 is applied between its own gate and source is turned on.

On the other hand, since the bipolar transistor Q4 is off, the current path for supplying current to the resistor R2 is substantially cut off, and substantially no voltage drop occurs across the resistor R2. Therefore, the field effect transistor Q2 which is applying the voltage between both ends of the resistor R2 between its own gate and source is turned off.

Then, from the center tap ct of the transformer T,
A current flows through the secondary winding w2 via the capacitor C and the source and drain of the field effect transistor Q1 in order. At this time, when the load is not connected between both ends of the rectifier circuit, when the charging of the capacitor C is substantially finished,
As a result, substantially no current flows through the secondary winding w2, and the current flowing through the detection windings wd1 and wd2 decreases. As a result, the field effect transistor Q1 is turned off. On the other hand, if a load is connected between both ends of the rectifier circuit, a current flows through the secondary winding w2 between the center tap ct of the transformer T and the drain of the field effect transistor Q1 even after the charging of the capacitor C is completed. Keeps flowing.

Further, a single-phase AC voltage to be rectified is applied between the two poles of the AC input terminal of the rectifier circuit of FIG. 5, and connected to the drain of the field effect transistor Q2 at both ends of the secondary winding w2. It is assumed that the voltage at one end becomes negative with respect to the potential of the center tap ct. In this case, a current flows from the center tap ct of the transformer T to the secondary winding w2 through the capacitor C, the parasitic diode between the source and the drain of the field effect transistor Q2, and the drain of the field effect transistor Q2 in order.

Then, of the two poles of the current detection terminal, the pole connected to the base of the bipolar transistor Q3 passes through the resistor R3 and the resistor R4 in that order to the base of the bipolar transistor Q4 of the two poles of the current detection terminal. The current reaching the connected pole increases. As a result, the bipolar transistor Q3 turns off and the bipolar transistor Q4 turns on.

Then, from the center tap ct of the transformer T to the emitter and collector of the bipolar transistor Q4, the resistor R2, the parasitic diode between the source and the drain of the field effect transistor Q2, and the drain of the field effect transistor Q2, A current flows through the next winding w2. As a result, the field effect transistor Q2 turns on. on the other hand,
Since the bipolar transistor Q3 is off, the field effect transistor Q1 turns off.

Then, from the center tap ct of the transformer T,
A current flows through the secondary winding w2 through the capacitor C and the source and drain of the field effect transistor Q2 in order. At this time, when the load is not connected between both ends of the rectifier circuit, when the charging of the capacitor C is substantially finished,
As a result, substantially no current flows through the secondary winding w2, and the current flowing through the detection windings wd1 and wd2 decreases. As a result, the field effect transistor Q2 is turned off. On the other hand, if a load is connected between both ends of the rectifier circuit, the secondary winding w2 between the midpoint tap ct of the transformer T and the drain of the field-effect transistor Q2 keeps current even after charging of the capacitor C is completed. Keeps flowing.

The present invention is not limited to the above-described embodiment, and various modifications and applications are possible. For example, the shape and material of the iron core F of the transformer T are arbitrary. In addition, the position of the winding and the like can be appropriately changed. Further, FIGS.
However, the present invention is not limited to the rectifier circuit shown in FIG.

[0081]

As described above, according to the present invention, a current detecting device capable of detecting a current with high sensitivity without changing a current flowing through a load is realized. Further, according to the present invention, a current detection device capable of detecting a current without deteriorating the frequency characteristics of the current flowing through the load is realized. Further, according to the present invention, a power supply device that does not change the current flowing through the load and has low loss is realized.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view schematically showing a cross section of a transformer according to a first embodiment of the present invention.

FIG. 2 is a diagram showing directions of magnetic lines of force generated by a primary winding of the transformer of FIG. 1;

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

FIG. 4 is a circuit diagram showing a configuration of a modification of the rectifier circuit of FIG. 3;

FIG. 5 is a circuit diagram showing a configuration of a modification of the rectifier circuit of FIG. 3;

[Explanation of symbols]

 T transformer F iron core w1 primary winding w2 secondary winding wd1, wd2 detection winding Q1, Q2 field effect transistor Q3, Q4 bipolar transistor C capacitor R1 to R4 resistor

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[Procedure amendment]

[Submission date] December 24, 1999 (1999.12.
24)

[Procedure amendment 1]

[Document name to be amended] Statement

[Correction target item name] Claims

[Correction method] Change

[Correction contents]

[Claims]

[Procedure amendment 2]

[Document name to be amended] Statement

[Correction target item name] 0009

[Correction method] Change

[Correction contents]

[0009]

In order to achieve the above object, a current detecting device according to a first aspect of the present invention includes a primary winding and a secondary winding inductively coupled to the primary winding. A transformer, and a pair of detection windings inductively coupled to the primary winding, wherein the pair of detection windings is
At least one of the magnetic fluxes generated by the current flowing through the windings
Part without linking to one of the pair of detection windings
And the detection windings are connected in a cascade in such a direction as to mutually cancel out electromotive forces mutually induced by a current flowing through the primary winding to form a series circuit. Each end of the series circuit forms a detection end for detecting a current flowing through the secondary winding.

[Procedure amendment 3]

[Document name to be amended] Statement

[Correction target item name] 0011

[Correction method] Change

[Correction contents]

Further, a current detecting device according to a second aspect of the present invention is a current detecting device, comprising: a primary winding; and a secondary winding inductively coupled to the primary winding. A current detecting device for detecting a pair of detecting windings inductively coupled to the primary winding ,
The detection winding is generated by the current flowing through the secondary winding.
At least a part of the magnetic flux that flows is one of the pair of detection windings.
It is arranged so that it does not
Ri, each said detecting winding is connected to said cascade to form a series circuit electromotive force mutually induced in each by a current flowing through the primary winding in a direction cancel each other, the respective ends of the series circuit And a detection end for detecting a current flowing through the secondary winding.

[Procedure amendment 4]

[Document name to be amended] Statement

[Correction target item name] 0013

[Correction method] Change

[Correction contents]

A power supply unit according to a third aspect of the present invention is a power supply device in which a primary winding and a tap which is inductively coupled to the primary winding and forms one pole of an output terminal substantially at its midpoint. A secondary winding provided with:
A pair of detection windings that are inductively coupled to the primary winding and are connected in cascade in a direction that cancels out electromotive forces mutually induced by currents flowing through the primary winding to form a series circuit; A current path and a control end connected between one end of the secondary winding and the other pole of the output end, wherein each current path is substantially responsive to a signal supplied to its own control end. A first switching means for turning on and off the power supply, a current path and a control end connected between the other end of the secondary winding and the other end of the output end, and supplied to respective control ends. Second switching means for substantially turning on and off the respective current paths in response to the applied signals, and a predetermined polarity among the current paths of the respective switching means based on the voltage at each end of the series circuit. To the end of the secondary winding which is generating Determine whether there is what is,
The current path is determined to be connected is turned on so that other of said current path is turned off, and a control means for supplying a signal to the control terminal of each of said switching means, the one
The pair of detection windings is driven by the current flowing through the secondary winding.
At least a part of the generated magnetic flux is generated by the pair of detection windings.
Are arranged so that they do not link to one another but to the other.
It is characterized by having.

[Procedure amendment 5]

[Document name to be amended] Statement

[Correction target item name] 0015

[Correction method] Change

[Correction contents]

The first switching means includes, for example,
It may be constituted by a first field-effect transistor having a drain, a source and a gate. In this case, for example,
A drain and a source of the first field-effect transistor form both ends of a current path of the first switching means;
The gate of the first field effect transistor may form a control terminal of the first switching means. Further, the second switching means may be composed of, for example, a second field effect transistor having a drain, a source, and a gate. The drain and the source of the second field-effect transistor form both ends of a current path of the second switching means, and the gate of the second field-effect transistor forms a control end of the second switching means. And it is sufficient.

[Procedure amendment 6]

[Document name to be amended] Statement

[Correction target item name] 0017

[Correction method] Change

[Correction contents]

[0017] The power supply device may further comprise a pair of electrodes at the output terminal.
A capacitor connected between the first switch and the first switch
Means for flowing a forward current bypassing its own current path
The first switching means for the second switching
Means for controlling the forward current flowing through the first rectifying means
A current bypassing the current path of the second switching means itself;
A second rectifying means for flowing through the secondary winding as
May be.

[Procedure amendment 7]

[Document name to be amended] Statement

[Correction target item name] 0032

[Correction method] Change

[Correction contents]

[0032]

Φ = (μ · n · π · r ² · I) / d

 ──────────────────────────────────────────────────続 き Continued on the front page F term (reference) 2G025 AA12 AB14 AC04 2G035 AA20 AB07 AB08 AC01 AC02 AC03 AC13 AD02 AD03 AD10 AD14 AD19 AD54 AD58 5H006 AA04 CA02 CA12 CA13 CB05 CB07 CC02 CC08 DB03 DC02 HA09

Claims (6)

[Claims] A transformer having a primary winding, a secondary winding inductively coupled to the primary winding, and a pair of detection windings inductively coupled to the primary winding; The detection windings are connected in a cascade in such a direction as to cancel out electromotive forces mutually induced by the current flowing through the primary winding to form a series circuit, and each end of the series circuit is A current detection device for forming a current detection end for detecting a current flowing in a next winding. 2. A current detecting device for detecting a current flowing through said secondary winding of a transformer having a primary winding and a secondary winding inductively coupled to said primary winding, A primary winding is provided with a pair of detecting windings inductively coupled to each other, and each of the detecting windings is connected in a cascade in such a direction as to mutually cancel electromotive forces mutually induced by a current flowing through the primary winding. A current detection device for detecting a current flowing through the secondary winding, wherein each of the terminals of the series circuit forms a current detection terminal. 3. A primary winding and a secondary winding inductively coupled to said primary winding and provided with a tap substantially at its midpoint to form one pole of an output terminal. A pair of transformers that are inductively coupled to the primary winding and are connected in cascade in a direction that cancels out mutually induced electromotive forces by a current flowing through the primary winding to form a series circuit. A detection winding, comprising a current path and a control end connected between one end of the secondary winding and the other pole of the output end, each of which has its own control terminal in response to a signal supplied to its own control end. A first switching means for substantially turning on and off a current path; and a current path and a control end connected between the other end of the secondary winding and the other pole of an output end. Substantially turn their current paths on and off in response to signals applied to the control end A second switching means connected to an end of the secondary winding generating a voltage of a predetermined polarity in a current path of each switching means based on a voltage at each end of the series circuit. Control means for supplying a signal to the control terminal of each switching means so that the current path determined to be connected is turned on and the other current paths are turned off. A power supply device comprising: 4. The first switching means comprises a first field effect transistor having a drain, a source and a gate, wherein the drain and source of the first field effect transistor are currents of the first switching means. Make both ends of the road,
A gate of the first field-effect transistor forms a control terminal of the first switching unit; the second switching unit includes a second field-effect transistor having a drain, a source, and a gate; The drain and source of the field-effect transistor form both ends of a current path of the second switching means,
The power supply device according to claim 3, wherein a gate of the second field effect transistor forms a control terminal of the first switching means. 5. The first and second switching means comprises:
When a signal for turning on its own current path is not supplied to its own control terminal and an electromotive force in a direction in which current flows in the secondary winding in a predetermined direction is induced in the secondary winding. ,
5. The power supply device according to claim 4, further comprising an initial current passing unit that transiently passes a current to the secondary winding by bypassing its own current path. 6. 6. The initial current passing means, a first rectifying element connected in parallel to a current path of the first switching means, and a self-current flowing in parallel with a current path of the second switching means. A second connected in a direction such that a forward current flows through the secondary winding as a forward current of the first rectifying element.
The power supply device according to claim 5, further comprising: a rectifying element, and a capacitor connected between both poles of the output terminal.