JPS60156268A - Magnetic control type switching regulator - Google Patents

Abstract

PURPOSE:To allow a switching regulator to be adapted for a high frequency and an increased output range by connecting in parallel snubber circuits at both ends of a saturable reactor and a rectifying diode connected in series, thereby constructing to eliminate the flow of the currents of the snubber circuit to the reactor. CONSTITUTION:A snubber circuit S3 which is constructed with capacitor C21 and a resistor R21 connected in series is connected with both ends of saturable reactor ML and a rectifying diode D21 connected in series. When a main switch is turned ON so that the reactor ML is magnetized to the saturated range, power is supplied from the secondary winding n2 to a capacitor CF and a load through the reactor ML, the diode D21 and a choke coil LF. The reactor ML is reset by the current controlled by the controller C2 while the main switch element is turned OFF.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention relates to a magnetically controlled switching regulator V-tactor.
This invention relates in particular to its output circuit.

[Background of the invention]

FIG. 1 shows an example of a conventional magnetically controlled switching regulator circuit.

E is an unstable DC power supply, T is a transformer, QM is a main switch element □, and C1 is a self-excited oscillation circuit that operates QM at a predetermined frequency.

Also, Dl is a rectifier diode, and Dl is a choke coil LP.
This is a commutating diode for regenerating the stored energy of Cr into the capacitor Cr.

The saturable reactor ML has T during the turn-on period of QM.
The voltage induced in the secondary winding MA n x is blocked for a certain period of time to control the output voltage VO to be constant. In this control, a detection signal V of the output voltage is input to a control circuit C2 composed of an error amplifier, a reference voltage generation circuit, etc., and a reset current Sr is caused to flow from the capacitor Cv via the control switch element Q. E is an auxiliary power supply that supplies power to C, when it is established exclusively, and ■.

It may be supplied from the side.

This conventional technique has the following drawbacks. That is, in addition to the current i controlled according to the output, the saturable reactor Mt is supplied with a current iS that charges the capacitor 021 at the flyback voltage when the QM is turned off. 1'
The path through which r flows is through a resistor 22, a capacitor Cx2 charged with a voltage of 12 with the polarity shown, and a resistor 21.
, and flows into the saturable reactor ML via the capacitor 021.

In a region where this current 1'r is much smaller than the reset current 1r, it does not cause a major problem, but when i is 0, that is, when the power is output to the maximum, i/ Since the saturable reactor ML is reset by r, a problem occurs in which the output decreases by an amount of 7. As a result, in addition to the deadangle determined by the magnetic characteristic H-H curve of the iron core, control is no longer possible due to the amount reset by the current iG, and the maximum output range becomes smaller.

Especially in recent years, iron core loss has been reduced, and coercive force (denoted as Hc)
Smaller materials have been developed. Since the smaller Hc has the advantage of being able to magnetize with a small amount of current, attempts have been made to apply it to higher frequencies in magnetic control.On the other hand, as the frequency increases, protection circuits of diodes D1゜Dg (C2t, 几21 and C22,几22) is 1 shame, the above-mentioned dead a
The output control range becomes extremely narrow due to the expansion of ngle, and cannot be used.

This configuration in which a protection circuit is connected between the poles of the diode inhibits high-frequency driving of the saturable reactor.

[Purpose of the invention]

An object of the present invention is to provide a magnetically controlled switching regulator having a configuration in which the current flowing through the protection circuit of the rectifier diode does not affect the reset of the saturable reactor.

[Summary of the invention]

The saturable reactor of a magnetically controlled switching regulator has a dead period that occupies the turn-on period of the main switch element.
a (The smaller the Igle ratio is, the more optimal it is for increasing the frequency and securing the output control range. Therefore, the structure is designed so that the charging and discharging current of the membrane protective circuit does not flow into the saturable reactor without impairing the protection function of the diode. This is an effective means of increasing the frequency.

Therefore, in the present invention, this object is achieved by connecting a protection circuit in parallel to both ends of the saturable reactor and rectifier diode connected in series.

[Embodiments of the invention]

FIG. 2 shows an embodiment of the present invention. In the figure, the primary side of the main transformer T is omitted, and the secondary side will be explained in detail. In the figure, a protection circuit (hereinafter referred to as a sunon circuit) S consisting of a series connection of a capacitor C2t and a resistor R121 includes a saturable reactor ML and a rectifier diode D21 connected in series.
connected to both ends.

Next, to explain the operation, when the main switch element Q shown in FIG.
Power is supplied to the capacitor Cr and the load via the L% diode D2 and the choke coil LF. At this time, the capacitor C22 in the parallel circuit of the commutating diode D2g is charged with the voltage of the secondary winding n2 to the polarity shown, thereby protecting the diode D22.

When the switch element QM is turned off, a reset current 1r corresponding to the output is applied to start resetting the saturable reactor MX, but at the same time, the secondary winding n has a flywheel whose polarity is opposite to the black circle shown in the figure. Since a back voltage is induced, a current 1'r flows along the path shown by the broken line while discharging the charge of cZZ.

This current stops after charging the capacitor CZI of the diode DSL (circuit capacitor CZI), and the saturable reactor M
It does not contribute to the L reset current. Therefore, during the turn-off period of QM, lr controlled by control circuit C2 becomes M
Reset L.

The function of the snubber circuit S to absorb the surge voltage generated when the diode D21 overflows is no different from the conventional method.

In this embodiment, the current of the snubber circuit is connected to the saturable reactor M
1. The maximum output range can be designed within the uncontrolled period determined by the B-H curve of the iron core.

FIG. 3 shows another embodiment of the present invention, in which the present invention is applied to a circuit configuration in which a saturable reactor ML is provided on the negative polarity side of the secondary winding n2. be. As in the first embodiment, the snubber circuit S is connected in parallel with the series circuit of the diode D21 and the saturable reactor ML.

In this case as well, when the switch element Q is turned on, the current that absorbs the voltage surge generated during recovery of the diode D21 flows through the path of the snubber circuit S1 resistor 22 and the capacitor C22 to the secondary winding n2, It does not flow into the saturation reactor ML.

Therefore, in addition to obtaining the same effects as the previous embodiment,
Since it does not flow to the secondary winding of the main transformer, it does not cause the main transformer to become unbalanced. This has the advantage of reducing the size of the main transformer and improving output accuracy since there is no need to prevent saturation of the main transformer, which has conventionally been taken.

FIG. 4 shows yet another embodiment. In this embodiment, a separate reset winding nR is provided, and a snubber circuit S is connected in parallel to a series circuit of a saturable reactor ML and a rectifier diode D2i. The reset current of the saturable reactor ML flows through a separate winding nR as indicated by the broken line in the figure. Since the charging/discharging current of the snubber circuit S flows to the secondary winding n3 via the resistor fizz and the capacitor C22, the same effect as in the other embodiments described above can be obtained.

Next, in the conventional example and the above embodiment, when the terminal voltage of the saturable reactor ML is observed, it is known that a voltage waveform shown by a broken line appears during the turn-off period Tuts of the main switch element QM as shown in FIG. ing. Although the amount of magnetization caused by this voltage is undesirable because of extra iron loss, it is unavoidable in terms of magnetic control of the current.

The cause of this voltage generation will be explained using Figure 1, QM
F),,fA@w,(r)17f:/fCol,Fi(After the turn-off of the element QM, the value E as shown in Fig. 5
, will be overcharged. The value E is determined by the turns ratio between nl and nl, and is fixed at this voltage Bo when the excitation energy of the main transformer is regenerated to the power supply E via the diode D1.

During this process of changing from value E to value E0, the charge in capacitor C1 is discharged via the excitation inductance of main transformer T, so a voltage with the black circles shown as positive appears in each winding of T, and this For example, in FIG. 1, the voltage magnetized by is observed as a voltage with the polarity attached to the saturable reactor ML, and in FIG.

In this embodiment, since there is a separate winding nR as shown in FIG. 4, the voltage caused by the switching circuit of the switching element QM is transferred to the diode D22 and the choke coil LF.
, ) flows through the transistor QR, so the voltage D
22 and the forward voltage drop of transistor QB.

Therefore, iron loss during steady operation can be significantly reduced.
It becomes possible to downsize the iron core.

FIG. 6 shows a modification of the previous embodiment. Although the operational effects are exactly the same, in this embodiment, a common anode diode can be used, so there is an advantage that the number of components is reduced by one in terms of mounting.

〔Effect of the invention〕

As described above, according to the present invention, the current of the snubber circuit does not flow to the saturable reactor, so that the reset can be performed using only the current controlled by the control circuit. This makes it possible to provide a magnetically controlled switching regulator that is ideal for increasing frequencies and expanding the output range.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a conventional magnetically controlled switching regulator, FIGS. 2 to 4 are circuit diagrams showing an embodiment of the present invention, FIG. 5 is a voltage waveform diagram explaining the operation of a saturable reactor, FIG. 6 is a circuit diagram showing another embodiment. QM...Main switch element, T...Main transformer, ML...
...Continuation of Figure 2, Figure 3, Addendum 4, Figure T - Figure 5, page 1 0 Inventor Susumu Nakajima 520G Mikajiri, Kumagaya City

Claims (1)

[Claims] 1. The @ current power supply, the primary winding of the main transformer, and the main switch element are connected in series, and the secondary side of the main transformer is equipped with a reactor for magnetic control, a rectifier diode, a choke coil, and a reactor connected in series with the reactor. A smoothing circuit composed of a capacitor and a commutation diode are provided for regenerating the excitation energy of the choke coil into the capacitor, and the excitation energy of the choke coil is outputted to the secondary winding of the main transformer by turning on and off the main switch element. A magnetically controlled switching regulator in which power is controlled to a constant output by the control reactor, characterized in that a snubber circuit is provided in parallel with a series circuit of the magnetically controlled reactor and a rectifier diode.