JPS6149660A - Multiple output switching power supplies - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a switching power supply device, and more particularly to power smoothing in a power supply capable of obtaining multiple DC outputs.

[Conventional technology] Switching in general? In the Ii source device, predetermined DC power is switched and converted into AC power, the converted AC power is supplied to DC power output circuits, and the DC power output circuit converts the AC power into DC power. Does the DC output circuit receive rectified DC power? In order to be ostracized,
A smoothing circuit consisting of an electric coil and a capacitor is provided.

By the way, many devices require multiple types of voltages as a power source. For example, 5 is stable for normal logic circuits.
A power supply of V is required, an operational amplifier requires a power supply of ±12V, and a power supply of 24V is required to drive a motor or solenoid. Therefore, many power supply devices that supply power to this type of device can generally provide multiple systems of DC output.

Conventionally, in order to smooth the DC power of each system, an electric coil is inserted into each system to perform smoothing. However, in order to achieve sufficient smoothness, this type of electric coil needs to be large in shape and have a large inductance, so inserting it into each system circuit will increase the size of the entire device. . Additionally, when using multiple electric coils, if they are placed close to each other, they will be electromagnetically coupled and interfere with each other, causing the inductance of each electric coil to drop below the expected value. Sufficient smoothing function may not be obtained. Increasing the distance between each electrical coil makes the device increasingly large.

[Object of the Invention] The present invention provides a multi-output switching power supply device i! which can obtain sufficiently smoothed DC power to each of a plurality of outputs. % miniaturization.

[Structure of the Invention] In order to achieve the above object, in the present invention, in order to prevent the electric coils for smoothing each DC output circuit from interfering with each other, even if there is only one electric coil, there is a plurality of electric coils. However, they are wound around one core to form a single unit, and connected so that the magnetic fluxes generated by the currents flowing in each DC output circuit mutually strengthen their magnetic fields.

For example, even when two electric coils are used, the winding directions of the coils must be relatively fixed (integrated) in advance.
For example, by determining the connection according to the direction of magnetic flux generation and the direction of the current in each direct θ;δ power output circuit, the two electric coils do not reduce their -r conductance. The configuration looks like this.

In this type of power supply circuit, the direction of the output current is constant, so once the electric coils are connected in a predetermined state, it is unlikely that the electric coils will influence each other after that.

Even in devices requiring multiple voltages, one of each power supply line is usually connected to a common potential line such as ground. In this case, the current of each of the plurality of power supplies flows in the common potential line in the amount of ff1. Therefore, in a preferred embodiment of the present invention, one electric coil is connected to a plurality of power supply outputs<connected common potential line t; substantially one electric coil is formed. The size of the electric coil.

The number of turns etc. can be kept to a minimum. Also, if smoothing is not performed, each DC power output time! The current flowing through each DC power output circuit is discontinuous. Assuming that the discontinuous periods do not overlap, the discontinuous currents of multiple systems can be combined into one
By superimposing the current on two electric coils, the current flows substantially continuously through the two electric coils, and the abnormal rise or fall in voltage that occurs in the conventional case does not occur.

Tomodarago Hereinafter, the present invention will be described in detail with reference to the drawings.

FIG. 1 shows an embodiment of a multiple output switching power supply device. Please refer to FIG. Power transformer T 1. (7
) - A commercial type iJX (AC100V) is connected to the next side. A switching control circuit 100 is connected to the secondary side of the 1-lance T1 via a bridge diode. L Vcc is the power:FX line of the switching control circuit 100 (in this example, it also serves as the power supply line for the transformer T2).

A predetermined DC voltage that is passed through a bridge diode is applied to one end of the primary side of the transformer T2. ,1
- The other end of the primary side of lance T2 is 1- for switching.
It is grounded via transistor Tr3. Therefore, 1
- When transistor Tr3 turns on/off, AC power is supplied to the primary winding of transformer T2 accordingly. The transistor Tr3 is constantly turned on and off by the switching control circuit 100.

Most of the switching control circuit 100 is an integrated circuit IC.
I (Tt4'J4), and functionally speaking, it drives the 1-transistor Tr3 so that the voltage feedback signal and current feedback signal obtained from the output of the power supply reach a predetermined value set in advance. Pulse No. 48 is generated for this purpose. By controlling the duty of this pulse signal, 1-
The power supplied to the primary side of the lance T2 is automatically adjusted.

1 - Paying attention to the secondary winding of lance T2, this secondary side is equipped with two windings, and a rectifier circuit consisting of two diodes connected in a half bridge is connected to each @ wire. ing. The positive output terminals of each rectifier circuit are set as output terminals ○UTI and 0UT2 of the power supply, respectively.

The negative output terminals of each rectifier circuit are commonly connected to each other.

One end of one electric coil L1 is connected to this commonly connected line. Smoothing cone capacitors are connected between the other end of the electric coil L1 and the output terminals ○UTI and 0UT2, respectively.

The other end of the f11 coil L1 is grounded via a current detection resistor.

That is, the current flowing through the first output circuit (the circuit that supplies power to ○UTI) and the current that flows through the second output circuit (the circuit that supplies power to OUT2) both pass through one electric coil L1. Focusing on the direction of the current, the directions of the current flowing from the two output circuits are the same in the electric coil Ll. In other words, the current flowing through the electric coil L1 is.

The value is the sum of the absolute value of the current flowing through the first output circuit and the absolute value of the current flowing through the second output circuit.

As a result, the current flowing through the electric coil L1 is averaged.6 In other words, even if the current flowing through the first output circuit is negative, the current flowing through the second output circuit is not negative. Current is not an atmosphere, and the same is true even if the relationship is reversed.

If the current flowing through this electric coil becomes discontinuous,
As has been known in the past, there is a possibility that differences in output voltage may occur, such as an increase in output voltage.
Having the currents of the two output circuits flowing in common reduces such risks. In addition, the fact that the direction of the current flowing through the electric coil L1 by the two output circuits is the same means that the fluctuation width of the current is small, and the resulting magnetic flux change is small and the influence on the outside is small. become.

FIG. 2 shows the configuration of the electric coil L1. Referring to FIG. 2, an electric coil Ll is formed by winding electric wire around a central core in multiple stages in the thickness direction (circumferential direction). The lead (terminal) at the beginning of winding is located on the inside of the electric coil, and the lead at the end of winding is located on the outside. Returning to Figure 1, in this example, the end of the winding of the electric coil L1, that is, the outer terminal, is connected to the ground line side, and the other terminal is connected to the common line between the first output circuit and the second output circuit. It is connected to. This essentially grounds the outer portion of the electric coil L1, and electrostatically shields the entire electric coil L1.

FIG. 3 shows another preferred embodiment of the present invention.

See Figure 3. In this embodiment, there is only one smoothing electric coil as in the previous embodiment, but a tap is provided in the middle of the smoothing electric coil. One end of the electric coil is connected to the low potential side of the output circuit on the ground line side V, and the low potential side of the +5V output circuit is connected to the tap of the electric coil.

In this example, the load is 5A from a +5V circuit.

The previous design was to connect something that would draw a current of 2A from the +24■ circuit.

The electric coil used in this example has an overall inductance of 1.0 [mll], and is set so that the inductance from the tap to the ground terminal is 0.3 [mll]. The location of this tap is determined depending on the load. As a result of this setting, it was found that the +5V power supply output was not affected by the +24V power supply. Especially in the case of pulse loads such as hammering, transient output stability is affected.

This was better than the case of the embodiment shown in FIG.

1, 5, 6 and 7 show modified embodiments of the present invention, respectively. FIGS. 4, 5, and 6 show changes due to changes in the connection between the transformer T2 and the output circuit and the loss characteristics. In the embodiments shown in FIGS. 5 and 6.

Two electric coils are used for each smoothing purpose, but both are electric coils wound around one core.
As can be seen from the drawings, the connections are made so that the direction of the magnetic flux generated in each electric coil by the current of each output circuit is the same. In the embodiment shown in FIG. 7, the smoothing electric coil itself is used as an element for generating a current feedback signal.

One end of the electric coil is grounded, and the other end is connected to the current feedback signal input terminal of the integrated circuit IC1 via a predetermined resistor.

[Effects] As described above, according to the present invention, the number of smoothing electric coils can be reduced and the size thereof can be reduced, and smoothing characteristics similar to those of the conventional method can be obtained.

[Brief explanation of drawings]

FIG. 1 is an electrical circuit diagram showing one embodiment of the present invention. FIG. 2 is a longitudinal cross-sectional view showing the construction of the electric coil L1 used in the device shown in FIG. FIG. 3, FIG. 4, FIG. 5, FIG. 6, and FIG. 7 are electrical circuit diagrams showing other embodiments of the present invention, respectively. Ll: Electric coil C○: Core 100 Niswitching control circuit TI, T2: l-lance ICI: Integrated circuit

Claims (5)

[Claims] (1) Switching predetermined DC power to convert it into AC power, supplying the converted AC power to at least two DC power output circuits, and converting the AC power into DC power in each DC power output circuit. In a multi-output switching power supply: An electric coil that smoothes the current in each DC power output circuit is wound around one core, and the magnetic flux generated by the current in each DC power output circuit strengthens the overall magnetic field. 1. A multi-output switching power supply device, characterized in that the electric coil is connected to the state. (2) Multiple output switching according to claim (1), wherein one line of each DC output circuit is connected in common, and one electric coil is connected between the common line and ground. power supply. (3) The electric coil includes one coil formed between two terminals and a tap formed between those terminals, one terminal of the electric coil is connected to a DC output circuit with a relatively high output voltage, DC output circuit 1 with relatively low output voltage
A multiple output switching power supply according to claim 1, wherein one line is connected to a tap of the electric coil and another terminal of the electric coil is connected to a common line. (4) The multiple output switching power supply device according to claim (3), wherein the taps of the electric coils are set at positions corresponding to the current flowing through each DC output circuit. (5) The electric coil is wound multiple times in the thickness direction of its core, and terminals are pulled out from the inside and outside of the coil, and the terminal pulled out from the outside is connected to the common ground potential of multiple DC output circuits more than the other terminal. A multiple output switching power supply device according to claim 1, (2), (3) or (4), which is connected to a nearby line.