JPS64913B2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a synchronous circuit for multiple switching regulators, and in particular, in order to equalize each switching frequency of multiple DC outputs that require insulation, an optical semiconductor device or the like is used. This invention relates to a synchronization circuit of multiple switching regulators connected by a photocoupler.

Generally, when multiple pulse width control switching regulators are operated in parallel, if the switching regulators are operated with oscillation circuits of different frequencies, they will interfere with each other, causing high frequency noise in the output. Problems such as an increase in the amount of noise and disturbances in the stabilization control system occur.

Therefore, when operating a plurality of switching regulators, it is essential that the frequency of each oscillator be made the same.

Conventionally, the following method has been used for this synchronization. That is, as shown in Figure 1,
In this method, each switching regulator is supplied with one oscillator, and 1, 2, . . . , n are switching regulators, and 4 is an oscillator.

In addition, as shown in FIG.
2 and 43, but in this example, synchronization circuits 51, 52, and 53 are provided, respectively, in order to synchronize the oscillation frequencies when they are not the same.

However, the above two examples can be used when the oscillator and the synchronous circuit are connected in a direct current manner, but in the case of a multiple switching regulator that requires mutual isolation as shown in Figure 3. had the disadvantage that it could not be applied.

In view of the above-mentioned drawbacks, this invention provides an oscillator, a triangular wave generator, and an amplifier specially installed in only one switching regulator unit, and the other switching regulator units are provided with an oscillator, a triangular wave generator, and an amplifier. An optical semiconductor device that can apply a triangular wave signal amplified to the level necessary for operation to a light emitting diode and transmit the same triangular wave signal as a fundamental triangular wave without distortion through a photodetector such as a transistor that is sensitive to light, that is, an optical coupling. A plurality of switching regulators can be operated at the same frequency by using the triangular wave signal as an input signal of the comparator of each unit via a photocoupler. The purpose of the present invention is to provide a synchronous circuit for a generator, and the present invention will be described in detail below with reference to the drawings.

FIG. 4 is a block diagram showing an embodiment of the present invention, and shows a method for synchronizing multiple switching regulators that require mutual insulation as shown in FIG. , 11 and 21 are switching regulator units 10 and 21, respectively.
20 error amplifiers, 12 and 22 are respectively the switching regulator units 10 and 20, and comparators 13 and 23 are switching circuits of the switching regulator units 10 and 20, respectively;
50 and 60 are the oscillator, triangular wave generator, and amplifier of the switching regulator unit 10, respectively, and 70 is the amplifier 6 of the switching regulator 10.
0 and the comparator 22 of the switching regulator unit 20
As an example, a circuit diagram thereof is shown in FIG. In the figure, 71 is a light emitting element such as a light emitting diode, and 72 is a light receiving element such as a transistor that is sensitive to light.

Next, the operation of the present invention will be explained using FIGS. 4 and 5, which are one embodiment thereof.

Now, if the output voltage of the switching regulator unit 10 rises (or falls) higher than the set voltage, the error amplifier 11 operates and the output voltage of the switching regulator unit 1
The rising error (or falling error) with respect to the set voltage of 1 is amplified and this amplified error signal is sent to the comparator 12, which compares it with the basic triangular wave signal from the triangular wave generator 50 and performs switching. The circuit 13 is operated to lower (or increase) the output voltage and return it to the set voltage.

Also, switching regulator, unit 2
When the output voltage of 0 rises (or falls), the triangular wave signal amplified by the amplifier 60 is applied to the light emitting diode of the photocoupler 70,
A current flows along with the triangular wave signal, and the light emitting diode 71 emits light in response to the current and sends out an optical signal.

Therefore, a current flows in the light receiving element 72 disposed opposite to the light emitting diode 71 in accordance with the optical signal, and the optical coupler 70 transfers the triangular wave signal from the amplifier 60 to the switching regulator. Since the signal is transmitted to the comparator 22 of the unit 20, the switching regulator . It operates exactly the same as unit 10.

It goes without saying that for other switching regulators that do not require insulation, the connection point C between the triangular wave generator 50 and the comparator 12 of the unit 10 and its own comparator may be connected.

Additionally, it is possible to achieve synchronization by transmitting the oscillator output (rectangular wave) using an optical coupler, but since the switching speed of general optical couplers is slow, an expensive high-speed optical coupler is required. On the other hand, since the present invention uses triangular wave transmission, it does not need to be high speed.

Furthermore, since pulse width control switching regulators generally require a triangular wave, a circuit for shaping each unit into a rectangular wave is also required.
Furthermore, although it is possible to achieve the same objective as the present invention by using a pulse transformer instead of the optical coupler, there are drawbacks such as increased cost.

As explained above, according to the present invention, a main switching regulator having an oscillation circuit, etc.
units and other switching regulators. By connecting optical couplers (photocouplers) between the units, it is possible to prevent frequency interference between each unit, and with only one oscillator, other switching devices can be connected. The number of parts can be reduced by being able to drive the regulator unit, and the triangular wave can be transmitted to an isolated synchronous circuit using an optical coupler (photocoupler) that can use relatively low-speed optical semiconductors. This has many advantages, such as eliminating the need for a shaping circuit for converting a rectangular wave into a triangular wave and eliminating the need for an expensive pulse transformer.

[Brief explanation of the drawing]

Figures 1 and 2 are block diagrams of conventional circuits, and Figure 3 is a block diagram of the conventional circuit.
The figure is a block diagram showing an example of a mutually insulated switching regulator, FIG. 4 is a block diagram showing an embodiment of the present invention, and FIG. 5 is a block diagram showing an embodiment of an optical coupler (photocoupler). It is a circuit diagram. 1, 2, 10, 20... Switching regulator, 11, 21... Error amplifier, 12, 22...
... Comparator, 4, 40, 42, 43 ... Oscillator, 5
0... Triangular wave generator, 51, 52, 53... Synchronous circuit, 60... Amplifier, 70... Optical coupler (photocoupler), 71... Light emitting element, 72... Light receiving element.

Claims (1)

[Claims] 1. In a switching regulator with multiple DC outputs that requires mutual isolation, each switching regulator is equipped with an error amplifier, a comparator, and a switching circuit, and only a predetermined switching regulator is equipped with an error amplifier, a comparator, and a switching circuit. , an oscillator with a predetermined frequency, a triangular wave generator based on this output signal, and an amplifier for amplifying this basic triangular wave signal, and this switching regulator is connected to other signals via an optical coupler operated by the amplifier. 1. A synchronization circuit for multiple switching regulators, characterized in that the switching regulators are connected to a comparator of the switching regulators to synchronize each switching regulator.