JPH0254026B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a magnetic amplifier type switching regulator that makes it possible to significantly suppress noise voltage on the output side. For more details,
Magnetic amplifier type switching regulators have been increasingly used in recent years because they enhance the recovery characteristics of the output side diode and have a remarkable effect on suppressing the diode spike voltage and output side noise voltage that occur during recovery. It's on. The present invention has been made to further suppress this noise voltage on the output side.

``Prior Art'' As shown in FIG. 5, a typical conventional magnetic amplifier type switching regulator has a DC power supply 3 and a MOSFET 4 as a switching element in the primary winding 2 of a transformer 1. The output terminal 1 is connected to the secondary winding 5 via a saturable reactor 6, a half-wave rectifier diode 7, a commutation diode 8, a smoothing coil 9, and a capacitor 10.
1, 12, and this output terminal 11, 1
2 is connected to an error detection circuit 18 consisting of a transistor 13, a Zener diode 14, and resistors 15, 16, and 17. The collector of the transistor 13 of this circuit 18 is connected to the saturable reactor 6 through a resistor 19 and a diode 20. and a rectifying diode 7.

The operation of the conventional circuit as described above will be explained based on the output waveform diagram in FIG.
The error detection circuit 18 detects the output voltage (Vo) between the resistor 19 and the diode 20.
It is supplied between the saturable reactor 6 and the rectifying diode 7 via. Then, T ₃ to _{T 5} in Figure 6a
During the period, that is, while the output voltage of the transformer 1 is negative, the magnetic flux of the saturable reactor 6 is expressed by the shaded area x,
Or it is reset by the voltage time product in FIG. 6b. Next, when a positive voltage is applied, when a magnetic flux equal to the reset voltage-time product is set,
The saturable reactor 6 is saturated and outputs a current Im as shown in FIG. 6c. As described above, the output voltage Vo is kept constant and functions as a switching power supply. At this time, the noise voltage appearing on the output side has four stages as shown in FIG. 6d. 1st
The second is when the FET 4 is turned on at T ₁ and the secondary voltage (Vo) of the transformer 1 rises rapidly, and the second is when the saturable reactor 6 is saturated at T ₂ and current Im flows. At the same time, the commutating diode 8 is cut off, and the third is when the commutating diode 8 recovers.The third is when the FET 4 is turned off at T ₃ and the secondary voltage Vi is suddenly reversed, and the fourth is when the commutating diode 8 is cut off. This is the recovery time when the rectifier diode 7 is cut off at _T4 .

"Problems to be Solved by the Invention" The present invention attempts to suppress the noise voltage generated by the sudden voltage change at times T ₁ and T ₃ in FIG. 6. Note that it is well known that the so-called normal noise generated at times T ₂ and T ₄ is effectively suppressed by the saturable reactor 6, and is not an object of the present invention.

Analyzing the noise generation principle at T ₁ and T ₃ above,
In Fig. 5, assuming that both ends of the secondary winding 5 of the transformer 1 are M and Y, and output terminals 11 and 12 are P and N, noise generation between PN occurs due to sudden changes in potential at points M and Y. Most of them are caused by radiated radio waves. Let's examine the noise caused by this radiation in detail. Assuming that points P and N are grounded via capacitances Cp and Cn, respectively, Cp=Cn
It is. C ₁ and C ₂ are stray capacitances from point M to P and N, respectively, through the space and others. C ₃ and C ₄ are also P and N from the Y point, respectively.
Stray capacitance up to . Therefore, the noise voltage Ptp at point P is Ptp=d/dtPtm×1/jωCp/1/jωC ₁ +1/jωCp +d/dtPty×1/jωCp/1/jωC ₃ +1/jωCp where, Cp≫C ₁ , If C ₃ , d/dt=Δ, then Ptp=ΔPtm×C ₁ /Cp+ΔPty×C ₃ /Cp, and similarly, the noise voltage Ptn at point N is Ptn=ΔPtm×C ₂ /Cn+ΔPty×C ₄ /Cn. Become. Therefore, the noise voltage between P and N
Vno _-1 is Vno _-1 = Ptp-Ptn = ΔPtm (C ₁ /Cp-C ₂ /Cn) + ΔPty (C ₃ /Cp-C ₄ /Cn) (1). In an actual circuit, P and N are connected by capacitor C, so the above equation (1) can be called the internal pressure of noise generation, and although this does not directly become output noise, it is output noise. It is clear that is approximately proportional to equation (1). At this time, if Y and N are short-circuited in FIG. 7, ΔPty (C ₃ /Cp−C ₄ /Cn) in equation (1) becomes zero, and the noise voltage Vno _-2 at this time is Vno _{- 2} = ΔPtm (C ₁ /Cp−C ₂ /Cn) …(2) holds true.

If this equation (2) is the conventional one, it is clear that the noise generation pressure in the above equation (1) depends on the amount of change in ΔPtm and ΔPty and their phase.

"Means for Solving the Problems" The present invention has been made to solve the above-mentioned problems, and it includes a saturable reactor between the secondary winding of the transformer and the half-wave rectifier diode. In a magnetic amplifier type switching regulator configured by combining a commutating diode and a smoothing circuit after the half-wave rectifying diode, two windings are provided as the saturable reactor, one of which is inserted. A winding is inserted between the positive end of the transformer and the anode of the half-wave rectifying diode, and the other winding is inserted between the negative end of the transformer and the anode of the commutating diode, Each winding is wound in the direction in which the voltage-time product is added.

"Function" Even if the secondary output voltage of the transformer is the same as before, by dividing the winding of the saturable reactor into two as in the present invention, the The change in potential at the positive and negative terminals on the secondary side of the transformer over a certain period of time is 1/2 that of a conventional transformer, and has a phase difference of 180 degrees from each other. Therefore, noise between the output terminals caused by sudden changes in potential at the positive and negative terminals on the secondary side is greatly reduced.

“Embodiment” An embodiment of the present invention will be described below based on the drawings.

FIG. 1 shows a first embodiment of the present invention, which differs from the conventional circuit shown in FIG. 5 in that a saturable reactor winds two windings 6a and 6b around the same core, and one 6a is inserted between the positive side end M of the transformer 5 and the anode of the half-wave rectifying diode 7, and the other winding 6b is inserted between the negative side end Y of the transformer 1 and the anode of the commutating diode 8. Insert it into
Each of the windings 6a and 6b is wound in the direction in which the voltage-time product is added.

The operation of the above configuration will be explained based on the output waveform diagram of each part in FIG. 2.

2a shows an output waveform diagram of the conventional circuit in FIG. 5, FIGS. 2b and 2c show output waveform diagrams according to the present invention, and in particular, FIG. 2d shows the output noise voltage of the circuit according to the present invention. This shows a waveform diagram showing that the waveform has been greatly reduced compared to FIG. 6d. To explain this in more detail, when comparing equations (1) and (2) above with Figure 2 a, b, and c, the following relational expression holds true in Figure 2 a of the conventional circuit.

Vi=Vmy=Ptm−Pty=Ptm Therefore, at T ₁ and T ₁ ′, ΔPtm=Vi/T ₁ −T ₁ ′ (3).

As in the present invention, the windings of the saturable reactor 6 are
In the divided circuit, even if the output voltage Vi of the transformer 1 is the same as the conventional one, the potentials at the positive and negative terminals M and Y are divided as shown in FIG. 2b and c. Here, if the negative side output terminal N is taken as the reference point, then FIG. Similarly, c indicates the voltage Ptmo of the negative terminal Y.

From the above, the following two facts are clear.

ΔPtyo and ΔPtmo have a phase difference of 180 degrees from each other.

Although both ΔPtyo and ΔPtmo have the same arrival time from T ₁ to T ₁ ' as in the conventional Figure 2a, the voltage change value is 1/2.

This can be expressed as equations (4) and (5) below, respectively.

ΔPtyo=−ΔPtmo …(4) ΔPtmo=1/2ΔPtm…(5) Substituting equations (4) and (5) into equations (1) and (2) and comparing them, Vnoo _-1 = ΔPtmo (C ₁ /Cp −C ₂ /Cn) −ΔPtyo(C ₃ /Cp−C ₄ /Cn) …(6) Vnoo ₋₂ =ΔPtmo(C ₁ /Cp−C ₂ /Cn)…(7). Here, since ΔPtmo in equation (6) is 1/2 compared to ΔPtmo in equation (7), the value of the term ΔPtmo (C ₁ /Cp−C ₂ /Cn) is halved.

Furthermore, the term ΔPtyo (C ₃ /Cp−C ₄ /Cn) is in opposite phase to the term ΔPtmo (C ₁ /Cp−C ₂ /Cn), and is different from (C ₁ /Cp−C ₂ /Cn). (C ₃ /Cp−C ₄ /Cn) is a finite value with little difference, so the left term and right term are subtracted, and the overall noise voltage
Vnoo _-1 decreases significantly.

Next, FIG. 3 shows another embodiment of the present invention, in which two saturable reactors 6
A and 6b are separately provided and provided at the positive terminal M and the negative terminal Y of the transformer 1, respectively. It is clear that if the windings 6a and 6b are wound in the direction in which the voltage-time product is added, the same effect as in the embodiment described above can be obtained.

Next, FIG. 4 shows still another embodiment of the present invention, in which the third voltage of the transformer 1 is proportional to the input voltage.
The voltage between the windings 21 is detected by the power supply IC 22, the MOSFET 4 is activated, and the voltage-time product of the output terminals 11 and 12 of the transformer 1 is roughly controlled to be constant, and this output is sent to the final stage error detection circuit 18. As described above, the output voltage (Vo) is closely held constant by the action of the saturable reactor 6. Particularly in this example, by inserting the rectangular saturable reactor 23 in series with the commutating diode 20, it has the effect of suppressing the noise generated during recovery of the commutating diode 8 at T2 in FIG. ₂ . In addition, if the Chi York coil is also divided into two windings 9a and 9b wound on the same core and inserted in the direction where the voltage time product is added to the positive side and the negative side,
Having the noise voltage suppressing effect without impairing the smoothing effect is the same as the theory of the first embodiment, and therefore, the noise voltage is further suppressed due to the synergistic effect of these effects.

"Effects of the Invention" Since the present invention is configured as described above, the noise voltage on the output side can be reduced to 1/2 to 1/3 of the conventional one.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing a first embodiment of a magnetic amplifier type switching regulator according to the present invention;
Fig. 2 is an output waveform diagram of each part, Fig. 3 is an electric circuit diagram showing a second embodiment of the present invention, Fig. 4 is an electric circuit diagram showing a third embodiment of the invention, and Fig. 5 is a conventional circuit diagram. FIG. 6 is a conventional output waveform diagram, and FIG. 7 is an equivalent circuit diagram of a conventional circuit for analyzing noise generation. 1...Transformer, 2...Primary winding, 3...2
Next winding, 4... Switching element (MOSFET),
5...Secondary winding, 6, 6a, 6b...Saturable reactor, 7...Half-wave rectification diode, 8...Commuting diode, 9, 9a, 9b...Chiyoke coil, 10...Capacitor, 11 , 12... Output terminal, 13... Transistor, 14... Zener diode, 15, 16, 17... Resistor, 18...
...Error detection circuit, 19...Resistor, 20...Diode, 21...Third winding, 22...Power supply IC,
23... Square saturable reactor.

Claims (1)

[Claims] 1. A saturable reactor is inserted between the secondary winding of the transformer and a half-wave rectifying diode, and a commutating diode and a smoothing circuit are coupled after the half-wave rectifying diode. In the magnetic amplifier type switching regulator, two windings are provided as the saturable reactor, and one winding is connected between the positive end of the transformer and the anode of the half-wave rectifier diode. and the other winding is inserted between the negative end of the transformer and the anode of the commutating diode, and each winding is wound in a direction in which voltage time products are added. Magnetic amplifier type switching regulator. 2. The magnetic amplifier type switching regulator according to claim 1, wherein the two windings of the saturable reactor are formed by dividing a winding wound around the same core into two. 3. The magnetic amplifier type switching regulator according to claim 1, wherein the two windings of the saturable reactor are two independent saturable reactors.