JPS58179161A - Operating method for switching regulator and circuit thereof - Google Patents

Abstract

PURPOSE:To reduce the size and weight of a switching regulator and to enhance the reliability by operating switching elements in parallel with drive signals of different timing and equal frequency in a time division manner. CONSTITUTION:The cathode sides of rectifying diodes D1-D4 in the output circuit of the first and second converters 1, 2 are commonly connected, and an output is produced through a sole choke coil L. Switching transistors Q1-Q4 are operated completely with drive signals of different timing and equal frequency. In other words, when the transistor Q1 is ON, the current is rectified by the diode D1, when the transistor Q2 is ON, the current is rectified by the diode D2, when the transistor Q2 is ON, the current is rectified by the diode D3, and when the transistor Q4 is ON, the current is rectified by the diode D4, smoothed by a choke coil L and a capacitor C, thereby obtaining a direct current.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in multi-channel switching regulators, and more particularly, to a method for time-division parallel operation of the main switching section and an output rectification/smoothing circuit suitable for implementing the method. The present invention relates to a switching regulator equipped with a switching regulator.

One known method for configuring a high-output switching regulator is to arrange a plurality of converter circuits in parallel and operate them in parallel to obtain a large output current.

Taking as an example a two-channel configuration having a half-bridge type switching section, a conventional switching regulator of this type was configured as shown in FIG. The first converter circuit 1 includes two capacitors 01°C2 and two switching transistors Ql.
.

It consists of C2, a transformer T1, rectifier diodes ()1, [)2 connected to the secondary side thereof, and a choke coil L1. Similarly, the second converter circuit 2 also includes two capacitors C3 and C4, two switching transistors Q3 and C4, a transformer T2, and rectifier diodes [)3 and [)4 connected to the secondary side thereof. , and a choke coil L2. Each converter circuit converts DC input into AC, transforms it, and rectifies it, and is commonly connected to input and output.

As is clear from the second operation timing chart, such a switching regulator turns on and off corresponding switching transistors in the first converter circuit 1 and the second converter circuit 2 at the same timing.
I am controlling it to turn it off. Therefore, if the frequency of the on/off operation of each switching transistor is f, it will be driven with a system clock of 2[.

However, with this conventional operation method, due to variations in the impedance of the output circuit (for example, differences in the forward voltage drop of the CJ1 rectifier diode), the current becomes unbalanced and one switching section is overloaded. It tends to become a state. Therefore, we had no choice but to insert choke coils with high impedance into the final output section of each converter circuit to make the impedances appear to be the same, and by balancing the circuit, we were able to suppress the current imbalance. A choke coil was essential.

In addition, in conventional switching regulators as described above, when each transistor is operating at its maximum width due to the low input voltage, if there is a clock delay or delay time of the switching transistor, multiple transistors in the same converter circuit One disadvantage is that it is difficult to set the constant voltage starting point low because there is a risk that the clock pulses may turn on at the same time, so it is necessary to provide a fairly large dead time for the clock pulse.

An object of the present invention is to eliminate the drawbacks of the prior art as described above, and to provide a method of operating a high-output switching regulator that is small, lightweight, and highly reliable, and a circuit thereof.

The present invention will be explained in detail below. The switching regulator circuit required to carry out the method of the invention may be similar to the conventional one shown in FIG. 1, but a circuit as shown in FIG. 3 is preferred. The major difference between this circuit and the conventional circuit is the output circuit. Third
In the figure, the cathodes of each rectifier diode D1 to D4 are connected in common and taken out through a single choke coil, so that even if the number of channels increases, only one choke coil is required. It has been simplified to . Since the other circuit parts are the same as those shown in FIG. 1, corresponding parts are given the same reference numerals and their description will be omitted.

In the present invention, as shown in FIG. 4, each switching transistor 01 uses a clock pulse with a frequency of 4f.
-Q4 are operated with drive signals 51-S4 of the same frequency (") with completely different timings.When the transistor Q1 is on, the rectifier diode D1 is operated, and in the same way, C
When C3 is on, it is rectified by D2, when C3 is on, it is rectified by D4, and when C4 is on, it is rectified by D4, smoothed by choke coil L and capacitor C, and DC is obtained. At this time, the choke coil operates at a frequency of 4f.

Although the above embodiment is an example of a case having a half-bridge type switching section, the method of the present invention can be similarly applied to a device having a push-pull type or full-bridge type switching section, and an output circuit similar to the above can be incorporated. be able to. 113, if each switching element is driven by a drive signal of the same frequency with different timing, 6
Needless to say, in the case of a full-bridge type, a pair of transistors located on opposite sides of the bridge must be turned on at the same timing so that the transformer can be energized.

Next, regarding the points in which the present invention is significantly different from the prior art,
The features of the present invention will be explained by comparing the two. The first feature of the present invention is that even if the number of channels increases, only one output choke coil is required. In the case of conventional parallel operation, one choke coil is required for each circuit to balance the converter circuit, so in the case of n-channel parallel operation, n choke coils are always required. there were.

On the other hand, in the case of time-division parallel operation according to the present invention, the collector current of each transistor is determined only by the load current, the inductance of the choke coil, the pulse width, and the turns ratio of the transformer. There is no imbalance between the circuits.

The second feature is that the output choke coil can be made smaller. In conventional parallel operation, the choke coil operates at twice the frequency of the main circuit, but according to the present invention, it operates at four times the frequency. Therefore, the critical inductance can be reduced by half, allowing for miniaturization. The third feature is that the transformer is also smaller.

In both the conventional normal parallel operation and the time-sharing parallel operation of the present invention, in the case of two channels, the power handled by each transformer is half of the energy supplied to the load, and the current is also half. In the case of the time-sharing parallel operation of the present invention, since the pulse width is half that of the conventional technology, the operating magnetic flux density is half, and if the core has the same cross-sectional area, half the number of turns is sufficient, or if the number of turns is the same. The core cross-sectional area can be halved. The fourth feature is that the dead time of the clocks is minimal and the clocks are not turned on simultaneously. In conventional converter circuits, a dead time is always provided to prevent the two switching transistors from turning on at the same time even when the input is low and the pulse width is maximum. This dead time has been set with a certain degree of margin in consideration of variations in characteristics of the elements, changes over time, and the like. However, in the time division method of the present invention, as is clear from FIG. 4, the time lag between turning on the two switching transistors in the converter circuit is always equal to or more than the pulse width, so there is no need for dead time in the clock. Therefore, the constant voltage starting point can be set low.

This means that constant voltage characteristics are guaranteed even if the line voltage drops momentarily for some reason, and that a long hold time can be taken when the input is cut off, which means that equipment using such a power supply reliability can be improved.

Since the present invention is configured as described above, it is possible to reduce the size and weight, suppress the loss of transformers and choke coils, and lower the constant voltage starting point, making it possible to obtain a highly reliable switching regulator. This is because it has an excellent effect.

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[Brief explanation of the drawing]

FIG. 1 is a circuit diagram showing an example of the prior art, FIG. 2 is an operating waveform diagram thereof, FIG. 3 is a circuit diagram showing an embodiment of the present invention, and FIG. 4 is an operating waveform diagram thereof. DESCRIPTION OF SYMBOLS 1... First converter circuit, 2... Second converter circuit, 01-Q4... Switching transistor, TI, T2... Transformer, D1-D4... Rectifier diode, L, Ll, L2...Choke coil. Patent Applicant: Fuji Electrochemical Co., Ltd. Agent: Yudo Omata
Shigemi Tanama Araki Tomonosuke 10-

Claims (1)

[Claims] 1. A converter circuit comprising a switching element, a transformer, and a rectifier connected to the secondary side of the transformer, and a plurality of converter circuits arranged in parallel to convert DC input into AC, transform it, and rectify it. . A method for operating a switching regulator, characterized in that each of the switching elements is operated in time-division parallel fashion using drive signals of the same frequency with different timings. 2.Equipped with a switching element, a transformer, and a rectifier connected to the secondary side of the transformer, multiple converter circuits are installed in parallel to convert DC input into AC, transform and rectify, and share input and output. In the switching regulator, the rectifying section of each of the converter circuits is composed of a rectifying diode, and the output from each rectifying diode is connected in common and taken out via a single choke coil,
A switching regulator circuit characterized in that each of the switching elements is time-divisionally operated in parallel.