JPH03226270A - Switching power supply - Google Patents

Abstract

PURPOSE:To reduce capacity of a common DC power supply, to suppress noise or voltage ripple and to simplify the circuitry by sharing a pulse generating circuit and an integrating circuit with two power supply circuits and performing switching operation with 180 deg. phase shift. CONSTITUTION:A pulse generating circuit PG and an integrating circuit IT are provided commonly for switching transistors Tr1, Tr2. A phase inverting circuit INV is provided for any one of the switching transistors Tr1, Tr2. A pulse S1 having 50% duty ratio provided from the pulse generating circuit PG is converted through the integrating circuit IT into a triangular wave S2 which is then provided to level comparing circuits CM1, CM2. On the other hand, the pulse S1 is provided as it is to an AND gate AND1 and further provided through the phase inverting circuit INV to an AND gate AND2.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a switching power supply circuit including two power supply circuits as a whole, and in particular to efficient use of a common DC power supply and suppression of ripple voltage included in the output. , relates to a switching power supply circuit that takes into consideration the simplification of the circuit configuration.

[Conventional technology]

Up until now, there have been many articles related to this type of power supply circuit, such as the following:

Publisher: July 10, 1988, pages 153-158)
However, in this case, when configuring a multi-circuit power supply using multiple switching power supply circuits, the switching power supply circuits that are configured independently are simply connected in parallel to a common DC power supply. .

FIG. 3 shows the configuration of an example of a multi-circuit power supply according to the prior art. This example shows a case where the multi-circuit power supply is composed of two switching power supply circuits. As shown in the figure, the primary sides of each of the switching transformers T1 and T2 are connected to the common DC power supply V, and the switching transistors Tri and Tr2 inserted in the primary side are independently connected to the P
The configuration is WM (pulse width modulation) controlled.

That is, the switching transistor Tri is periodically turned on, and its period is controlled by the period of the pulse obtained from the pulse generating circuit PGI, and its on time is controlled by the error L1 between the output voltage and the reference voltage. It has become a thing. The pulse from the pulse generation circuit PCI is converted into a triangular wave by the integrator circuit IT1, and then compared with the above error L1 by the level comparison circuit CMI as a comparator. A pulse is output only during this period, and this is the pulse from the pulse generation circuit PGI and the AND circuit AN.
It is ANDed in DI Koi, and the switching transistor Tr is connected via the switching circuit SW1 based on the AND result.
i is controlled on and off as a variable pulse width. By the way, the pulse width modulation circuit is the level comparison circuit C.
M.I.

It is composed of an AND circuit AND1 and a switching circuit SW1.

In this way, the on-time of the switching transistor Tri is controlled according to the magnitude of the error, so that the output voltage of the switching power supply circuit always matches the reference voltage. The same situation holds true for the pulse generation circuit PG2, integration circuit IT2, level comparison circuit CM2, AND circuit AND2, and switching circuit SW2 provided for the switching transistor Tr2. In addition, in the figure, RLI
, RL2 each indicate a load on the switching power supply circuit.

[Problem to be solved by the invention]

As described above, in the multi-circuit power supply according to the conventional technology,
Since a plurality of independent switch power supply circuits are simply connected in parallel to a common DC power supply and operate asynchronously with each other, the number of component parts will inevitably increase. Furthermore, considering the possibility that the switching transistors in each of the switching power supply circuits may be turned on at the same time, the current capacity of the common DC power supply must also be increased. Furthermore, there are other problems, such as not taking into consideration the prevention of noise caused by simultaneous operation of switching transistors and ripple voltage caused by different switching frequencies.

An object of the present invention is to provide a switching power supply circuit as a multi-circuit power supply in which the capacity of a common DC power supply is kept small, the generation of noise and ripple voltage is suppressed, and the overall circuit configuration is simplified.

[Means to solve the problem]

For the above purpose, the two power supply circuits are the pulse generation circuit and (
This is achieved by using an integrating circuit (for triangular wave generation) as a common component and performing switching operations with their phases shifted by 180''.

[Effect]

A pulse with a duty ratio of 50% is obtained from the pulse generation circuit, but by inverting this pulse, a pulse with a phase difference of 180° can be easily obtained. Therefore, if each of the two power supply circuits is caused to perform a switching operation based on the original pulse and the phase-inverted pulse, the two power supply circuits will perform the switching operation at the same switching frequency but with their phases shifted by 180 degrees. It is what it is. As a result, switching operations are not performed simultaneously, and not only the current capacity of the common DC power supply can be reduced, but also noise caused by large current flowing out from the common DC power supply can be suppressed. Furthermore, since the switching frequencies are the same, ripple voltage in the output voltage can also be suppressed.

〔Example〕

The present invention will be explained below with reference to FIGS. 1 and 2.

First, the configuration of a switching power supply circuit according to the present invention will be described. FIG. 1 shows an example of the configuration. As shown in the figure, the one in this example assumes two different flyback type switching regulators, and the substantial difference from the one shown in FIG. 3 is that the switching transistors Tri and Tr2 commonly generate pulses. This is because the circuit PG and the integrating circuit IT are provided.

Moreover, the switching transistor Tr1. A phase inversion circuit (inverter) INV is newly provided for either one of Tr2. A pulse Sl with a duty ratio of 50% from the pulse generation circuit PG is converted into a triangular wave S2 by an integrator circuit IT and then sent to level comparison circuits CMI and CM.
On the other hand, the pulse S1 is directly applied to the AND circuit AND1, and the pulse S1 is applied to the AND circuit AND2 via the phase inversion circuit INV. The situation is almost the same.

FIG. 2 shows input/output signal waveforms in an example of the main part. This is clear from the above explanation, so a detailed explanation is not necessary. By the way, the switching transistor Tri.

Inflow current I when each Tr2 performs switching operation
(In+Ib) is explained as follows.

That is, switching transistor Tr1. Switching pulse S5 to each Tr2. Since S6 is generated as shown in FIG. 2 and therefore not generated at the same time, the simultaneous inflow of currents Iα and Ib into switching transistors Tri and Tr2, respectively, is also suppressed. As a result.

As a common DC power source, its current capacity is small.

〔Effect of the invention〕

As described above, according to the present invention, the capacity of the common DC power supply can be kept small, noise and ripple voltage can also be suppressed, and the overall circuit configuration can be simplified.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of an example of a switching power supply circuit according to the present invention, Fig. 2 is a diagram showing input/output signal waveforms of an example of its main part, and Fig. 3 is a diagram showing the configuration of an example of a switching power supply circuit according to the prior art. FIG. 3 is a diagram showing an example configuration. PG...Pulse generation circuit, IT...Integrator circuit, CM
l, CM2...Level comparison circuit, INV...Phase inversion circuit, (inverter), Trl, T, r2...Switching transistor, Tl, T2...Switching transformer, ■...Common DC power supply.

Claims (1)

[Claims] With the primary sides of each of the first, second, and second switching transformers connected to a common DC power supply, the switching operations of the first and second switching transistors inserted in series on the primary side are performed as follows. A switching power supply circuit configured to be controlled by first and second pulse width modulation circuits provided corresponding to first and second switching transistors, the duty ratio of which is 5 from a common pulse generation circuit.
The 0% pulse is converted into a triangular wave by a common integration circuit, and then given to the first and second pulse width modulation circuits.
At the same time, the switching power supply circuit is configured such that the pulse is directly applied to the first pulse width modulation circuit and the pulse is applied to the second pulse width modulation circuit via an inverting circuit.