JPS6135163A - Switching regulator - Google Patents

Abstract

PURPOSE:To prevent the output voltage from varying due to the alteration of the output current by rectifying and smoothing the current obtained at the secondary widing of the second transformer connected with the primary winding at the secondary winding of the first transformer to feed back to the primary winding of the first transformer. CONSTITUTION:The second transformer 7 connected with the primary winding n11 in series with the secondary winding n2 of a transformer 1 is provided, and a rectifying and smoothing circuit 31 for rectifying and smoothing the current obtained at the secondary winding n12 of the second transformer 7 to produce a DC voltage ef corresponding to the output currnt I0 is provided. A feedback voltage Ef from the winding n3 of the transformer 1 obtained through a rectifying and smoothing circuit is corrected by the voltage e1, and the corrected voltage Ef' is fed back to the primary winding of the transformer 1. Thus, even if the output current is varied, a DC voltage ef is obtained by insulating from the output voltage E0 to correct the feedback voltage to eliminate the variation in the voltage E0.

Description

DETAILED DESCRIPTION OF THE INVENTION (Technical Field of the Invention) The present invention relates to a switching regulator having a transformer.

(Prior Art) FIG. 3 is an electrical connection diagram showing an example of a conventional switching regulator.

In this switching regulator, an input voltage E1 is applied to a series circuit of a primary winding n1 of a transformer 1 and a transistor 2, which is a switching element.

When the transistor 2 is turned on, the primary current 11 flows, and when the transistor 2 is turned off, the energy stored in the core of the transformer 1 is transferred to the secondary winding n2. Secondary current 12 on n3 side
113. Secondary current 1 on secondary winding n2 side
is rectified by the rectifying and smoothing circuit 3, and becomes the output voltage E, which is generated at the output terminal OUTK. The switched secondary current i3 on the secondary winding side is rectified and smoothed by a rectifying and smoothing circuit 4, and is applied to the transistor 20 control circuit 5 as a feedback voltage E related to the output voltage EK.

The control circuit 5 controls the turn-on of the transistor 2 so that the feedback voltage E becomes equal to a preset reference voltage E, thereby stabilizing the output voltage E. In the switching regulator having such a configuration, a starting circuit 6 is provided in order to operate the control circuit 5 at the time of starting. The starting circuit 6 uses a series regulator consisting of a transistor 61, a resistor 62, and a Zener diode 63. At startup, the transistor 61 is turned on, and the control circuit 5 receives the Zener voltage V of the Zener diode 63 and the base voltage of the transistor 61. Emitter voltage V
A voltage determined by the difference E is added as the drive voltage V, and the control circuit 5 operates. When the transistor 2 is turned on and off by the operation of the control circuit 5 and enters a steady state, a feedback voltage E is generated.

becomes larger than the Zener voltage V, and the control circuit 5 is driven by the regulated voltage E-c from the transformer 1.

However, the switching regulator configured as described above exhibits a characteristic in which as the load current increases, the output voltage E decreases, and there is a problem in that satisfactory control characteristics cannot be obtained.

FIG. 4 shows the load current and output voltage E using the device shown in FIG.

FIG. Load current engineer. It is observed that the output voltage E decreases as .

(Problems to be Solved by the Invention) The present invention has been made in view of the problems in the prior art, and its purpose is to provide good control characteristics in which the output voltage does not change due to fluctuations in the output current. switching
This is an attempt to realize a regulator.

(Means for solving the problem) A first transformer having a primary winding to which an input voltage is applied, a secondary winding connected to an output terminal via a rectifying and smoothing circuit, and a winding for obtaining a feedback voltage; A switching regulator having a switching element connected in series with the primary winding, and a control circuit for controlling the switching element on and off so that the feedback voltage becomes equal to a reference voltage, the primary winding being connected in series with the secondary winding. A second transformer having a winding connected thereto, and a rectifying and smoothing means for rectifying and smoothing the current obtained in the secondary winding of the second transformer to obtain a DC voltage corresponding to the output current, are provided, and the feedback voltage is is corrected by the DC voltage obtained from the rectifying and smoothing means.

(Embodiment) FIG. 1 is an electrical connection diagram showing an example of a switching regulator according to the present invention. In this figure, the same parts as in FIG. 3 are given the same reference numerals.

1, the difference from the conventional example shown in FIG. 3 is that a second transformer 7, whose primary winding n□□ is connected in series with the secondary winding n2 for obtaining the output voltage of the transformer 1, is A rectifying and smoothing circuit 31 is also provided to rectify and smooth the current obtained in the secondary winding n of the second transformer 7 to obtain a DC voltage ef corresponding to the output current I.
The point is that the feedback voltage E from the winding n3 of the first transformer 1 obtained via the DC voltage E is corrected by the DC voltage 2/, t'/DC voltage e.

Here, the DC voltage ef obtained in the rectifying and smoothing circuit 31 (resistance 81) is passed through the rectifying and smoothing circuit 4 through the resistor 82.
The feedback voltages E obtained are applied to one end of the control circuit 5 via the resistors 83, respectively.

According to the device of the present invention configured in this way, the DC voltage e corresponding to the output current is output from the rectifying and smoothing circuit 31.
It is obtained insulated from the output voltage E0. This DC voltage corresponds to the output current I. As E increases, the voltage E1 applied to one end of the control circuit 5 changes in a downward direction because it increases accordingly. The control port 5 controls the switching element f s 2 so that E'=E, and when p'' decreases, the feedback voltage E.

In other words, the output voltage E increases as the output current increases.

Through this operation, the output voltage E, which had a tendency to decrease as the output current increases, is significantly reduced as the output current increases, and a constant output voltage E that is not affected by changes in the output current can be obtained. be able to.

Figure 2 shows the output current ■ and the output voltage E by the device in Figure 1.
FIG. As is clear from this characteristic diagram, the output voltage E can be maintained almost constant regardless of fluctuations in the output current, and a satisfactory result has been obtained.

In addition, although the above description has shown the one provided with the starting circuit 6, this circuit may be omitted.

In addition, in the above embodiment, the feedback voltage E, the DC voltage e,
and are applied to one end of the control circuit 5 via resistors 82 and 83, respectively, but the feedback voltage may be modified by other circuit means.

(Effects of the Present Invention) As described above, according to the present invention, it is possible to realize a switching regulator with good control characteristics in which the output voltage does not change due to fluctuations in the output current.

[Brief explanation of drawings]

FIG. 1 is an electrical connection diagram showing an example of a device according to the present invention;
FIG. 2 is a diagram showing its characteristics, FIG. 3 is an electrical connection diagram of the conventional device, and FIG. 4 is a diagram showing its characteristics. DESCRIPTION OF SYMBOLS 1... First transformer, 2... Switch element, 5,
51゜4... Rectification and smoothing circuit, 5... Control circuit, 6.
... Starting circuit, 7... Second transformer.

Claims (1)

[Claims] (1) A first transformer having a primary winding to which an input voltage is applied, a secondary winding connected to an output terminal via a rectifying and smoothing circuit, and a winding for obtaining a feedback voltage, connected in series to the primary winding. In the switching regulator, the switching regulator has a connected switching element and a control circuit that controls on/off the switching element so that the feedback voltage becomes equal to a reference voltage, the primary winding of which is connected in series with the secondary winding. A second transformer and a rectifying and smoothing means for rectifying and smoothing the current obtained in the secondary winding of the second transformer to obtain a DC voltage corresponding to the output current are provided, and the feedback voltage is obtained from the rectifying and smoothing means. A switching regulator characterized in that it is modified by the obtained DC voltage.