JPS6338713Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a multi-output DC-DC converter equipped with a blockage wire for removing common mode noise.

In general, a DC-DC converter intermittently supplies DC input voltage to the primary winding of a transformer through the switching operation of a semiconductor switching element, rectifies and smoothes the AC voltage obtained at the secondary winding, and A DC output voltage different from the DC input voltage is obtained between the output terminals. Therefore, switching noise inevitably occurs, and this switching noise causes common mode noise because the primary side circuit and the secondary side circuit are isolated by the transformer. To eliminate such common mode noise, a blocked wire ring is usually used, which has separate windings wound around the same core. It is said that the smaller the electrostatic coupling, the better. In other words, if the input and output ends of the winding are relatively close together and are electrostatically coupled, high-frequency noise will pass through the capacitive coupling and appear at the output end without passing through the blocking coil. be. Therefore, in the case of a DC-DC converter with two power supply outputs, the DC-DC converter has two outputs, as shown in Figure 1A.
Separate blocking wires 2, 2' may be provided for each output of the DC converter 1, or a single blocking wire formed by winding three windings around the same core as shown in FIG. Equipped with 2 streamline wheels. This flow line ring 2 is shown in Figure C.
As shown in the figure, it consists of three windings 2B, 2C, and 2D wound around a toroidal core 2A with a phase shift of 120 degrees, but three windings are wound around a small core 2A. Therefore, each winding is closer to each other than that of the secondary wire, and due to space constraints, when mounted on a printed circuit board, the input between one winding and another winding is The disadvantage is that the outputs have to be close together and therefore the intended purpose of having such a blockage ring cannot be achieved. Also, 3 in core 2A
Since each winding wire must be wound individually, there are problems such as requiring a lot of man-hours. On the other hand, in the case of a circuit configuration as shown in FIG. 1A, two obstructing wires are required, which increases the cost and requires a large space.

In order to eliminate the drawbacks of the conventional DC-DC converter, the present invention provides at least a block wire ring winding connected in series to a common output line on the output side of the DC-DC converter. It is characterized by a ring-wound wire and a bifilar-wound wire.

Embodiments of the present invention will be described below with reference to the drawings.

First, in FIG. 2A, 3 indicates the primary circuit connected to the primary winding N ₁ of the transformer 4 of the DC-DC converter 1, and this primary circuit is illustrated as is well known. It consists of a DC input power supply circuit that is not connected to the DC input voltage, and a semiconductor switching element that switches the DC input voltage on and off. Secondary windings of transformer 4 N ₂ , N ₃
are connected to positive and negative output lines 5 and 6, respectively,
A common output line 7 is connected to the midpoint between the secondary windings N ₂ and N ₃ . A full-wave rectifier 8 is connected to the positive and negative output lines 5 and 6, and the full-wave rectified DC output thereof is smoothed by a smoothing circuit 9. on the other hand,
The positive and negative DC output voltages of the output lines 5 and 6 are detected by the voltage detection circuit 11 via the blockage wire 10 for common mode noise removal, and the switching control circuit 12 detects the detection signal from the voltage detection circuit 11. The duty cycle of the high frequency pulse signal from the high frequency pulse generator 13 is modulated according to the value, and the thus modulated drive signal is applied to the semiconductor switching element in the primary side circuit 3 for switching.

The common mode noise generated by such switching is removed by the common mode noise removing blocking wire 2 disposed on the output side of the smoothing circuit 9. As shown in FIG. 2B, this blocked wire ring 2 is made by winding wires 2B and 2D in bifilar winding around a single toroidal core 2A, and separating these windings 2B and 2D as much as possible. Similarly, the windings 2C and 2D' are bifilar-wound and wound around the core 2A. The winding 2B is connected in series to the output line 5, and the winding 2C is connected in series to the output line 6. Further, the windings 2D and 2D' of the same polarity are connected to each other, and the connection point thereof is connected in series to the common output line 7. By configuring the blocking wire ring 2 in this way, it is possible to provide a sufficient distance between the input and output of the same winding and between the input and output of other windings, so that the input and output of the winding is kept quiet. Since there is no electrical coupling, high frequency common mode noise can be sufficiently removed. In addition, since the process of winding the winding wire around the core can be reduced from the conventional three times to two times, this embodiment is advantageous in terms of cost, and it is possible to reduce the winding process to the core using two winding wire rings. It is even more advantageous in terms of cost and space.

In this example, it goes without saying that the wire characteristics and the number of turns of each winding are the same, but as the current and voltage of each of the two power supply outputs are different,
If the number of turns of the windings 2C and 2D' is different from that of the windings 2B and 2D, diodes may be connected in series with the windings 2D and 2D' according to their polarities. Further, in this embodiment, since the windings 2D and 2D' of the blocking coil 2 are connected in parallel, thin wires can be used. Note that 14 and 14' are capacitors for noise removal.

Next, the blockage wire ring 2 of another configuration shown in FIG.
- Winding 2D, which is to be connected in series with the common output line of the DC converter, is replaced with winding 2C, which is either one of the windings to be connected in series with the positive or negative output line.
It is bifilar wound and wound around the core 2A. Even if a blockage wire having such a structure for removing common mode noise is used in place of the blockage wire disposed on the output side of the DC-DC converter of the above embodiment,
Exactly the same effect can be obtained.

As mentioned above, according to the present invention, multi-output DC-
Since the winding of the blocking wire ring connected in series to the common line on the output side of the DC converter is bifilar-wound with the blocking wire ring connected in series to the output line, the input and output of each winding of the blocking wire ring is bifilar-wound. It is possible to provide sufficient distance between the input and output of other windings, as well as between the windings.
Therefore, the electrostatic coupling between the input and output of the blocking wire can be reduced to a negligible value, and high frequency common mode noise appearing in the DC-DC converter can also be reliably removed. Further, since the number of man-hours required for winding the blocked wire ring can be reduced, it is economically advantageous.

[Brief description of the drawings]

FIG. 1 is a diagram showing a conventional embodiment, in which A and B are diagrams for explaining a blockage wire for common mode noise removal in a DC-DC converter, and C in the figure is a diagram showing such a blockage. A diagram showing a specific example of a wire ring,
FIG. 2A is a diagram showing an embodiment of the DC-DC converter according to the present invention, and FIG. 2B and FIG. It is. 1...DC-DC converter, 2, 2'... Blocking wire for common mode noise removal, 3... Primary side circuit, 5, 6... Output line, 7... Common output line, 8... ... Rectifier, 9... Smoothing circuit, 10...
Obstruction wire, 11... Voltage detection circuit, 12... Switching control circuit, 13... Pulse generator.

Claims (1)

[Scope of utility model registration request] A semiconductor switching element that is connected to the primary winding of the transformer and opens and closes the DC input according to a drive signal from a switching control circuit; a plurality of output lines and a common output line that are connected to the secondary winding of the transformer; A rectifier connected to the output line, and a blockage wire ring for common mode noise removal, which is formed by winding windings connected in series to the output line and the common output line, respectively, around the same core, to provide a plurality of direct currents. In a DC-DC converter that obtains an output, the blocking wire ring winding connected in series to the common output line is bifilar-wound with at least one of the blocking wire ring windings connected in series to the output line. A DC-DC converter characterized by: