JPH04125065A - Switching circuit device - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost by dividing a current closed loop of a DC power source, a primary winding of an output transformer and a switching element into a plurality of concentrical current loops, and so forming a wiring pattern that reverse current flows in the adjacent loops. CONSTITUTION:A closed loop of a current I flowing from a power source through a resistor R, a primary winding of an output transformer Tr and a driving transistor Q is so divided into current loops i1, i2 as to become concentrical, and a wiring pattern is so formed that reverse currents flows in the adjacent loops i1 and i2. Reverse magnetic fields PHI1, PHI2 are formed by the loops i1, i2, but formed on the same line to be canceled each other to be greatly weakened. Thus, an unnecessary radiation noise can be suppressed without altering a circuit configuration of switching, without using a sealing plate, a conductor ring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a switching circuit device in a switching power supply, a high voltage power supply, and the like.

[Conventional technology]

A switching power supply or the like has a switching circuit formed of a DC power supply, a primary winding of an output transformer connected to the DC power supply, and a switching element such as a transistor connected to the primary winding. And PWM
The switching element is turned on and off by a circuit or the like, thereby generating an alternating current voltage in the secondary winding of the output transformer, and this alternating current is supplied directly or after being rectified to the load. At this time, unnecessary radiation noise may be generated from the switching circuit due to the above-described switching operation.

Conventionally, as a countermeasure against the generation of unnecessary radiated noise, a shield plate has been attached around the source of the radiated noise, or a conductor ring has been attached around the element that generates the radiated noise. By converting the magnetic force into current and absorbing it using the shield plate and conductor ring, unnecessary radiated noise is suppressed.

[Invention or problem to be solved]

However, in the conventional switching circuits described above, it is necessary to use a shield plate or a conductor ring as a countermeasure against radiated noise. Therefore, when a shield plate is used, production costs increase and space is required accordingly. However, if a conductor ring is used, the installation work is complicated and the number of assembly steps increases, which also increases the production cost.

The present invention was made with attention to such problems, and the number of parts and assembly man-hours are small, the device is compact, and
Another object of the present invention is to obtain a switching circuit device with low manufacturing cost.

(Means for Solving the Problems) The switching circuit device of the present invention includes a DC power supply, a secondary winding of an output transformer connected to the DC power supply, and a switching element that switches the current flowing through the primary winding. A closed loop of current is formed, and this closed loop is divided into a plurality of current loops so as to be concentric with each other,
In addition, the wiring pattern is formed so that current flows in opposite directions in adjacent Tf loops. Further, in the switching circuit device of the present invention, the wiring pattern described above is formed on a printed wiring board, and current loops are formed by bringing conductive wires through which current flows in opposite directions close to each other.

[Effect]

In the switching circuit device of the present invention, the closed current loop formed by the DC power source, the primary winding of the output transformer, and the switching element is divided into a plurality of concentric current loops that intersect with each other, and adjacent loops conduct current in opposite directions. As the current flows, the lines of magnetic force in adjacent current loops cancel each other out, reducing the external magnetic field.

〔Example〕

FIG. 1 is a diagram showing the configuration of a switching circuit device according to a first embodiment of the present invention, and shows a wiring pattern of a switching circuit formed on a printed wiring board.

In Fig. 1, the primary winding of Tr is +2
The output transformer Q connected to a 4V DC power supply is a driving transistor that is a switching element that switches the current flowing through the primary winding of the output transformer T, and a closed current loop is thus formed. C1 is a smoothing capacitor, C2 is a resonance capacitor, and D is a diode.

FIG. 2 is a diagram showing a switching circuit constructed on the printed wiring board of FIG. 1. From the DC power supply to the output transformer T1. Current I flowing through drive transistor Q
As shown in the hatched wiring pattern in FIG. 1, the closed loop is divided into two concentric current loops in which current flows in opposite directions as shown by the arrows. Figure 3 shows the magnetic field Φ1 generated by these two current loops 11+12.
．． Φ2 is schematically shown.

From the above power supply, resistor R1 output transformer T, - primary winding,
The closed loop of the current ■ flowing through the driving transistor Q is divided into a plurality (two in this case) of current loops 11+12 so as to be concentric with each other as described above, and the adjacent current loops 11+12 are connected to each other as shown by the arrows. The wiring pattern is formed so that current flows in the opposite direction. Therefore, each current loop il+12 causes a magnetic field Φ1. Φ2 is formed, but these magnetic fields Φ1. Since Φ2 are formed on the same line, they cancel each other out and are significantly weakened. That is, the magnetic fields generated by the switching operation of the circuit shown in FIG. 2 cancel each other out internally, reducing unnecessary radiation noise to the outside.

In this way, unnecessary radiated noise can be suppressed without changing the switching circuit configuration and without using conventional seal plates or conductor rings. Therefore, the number of parts and assembly man-hours are small, and the unit size is small, so the device is also compact, saving space and lowering manufacturing costs.

FIG. 4 is a diagram showing a second embodiment of the present invention.

In this embodiment, each current loop iI+12 is formed by placing conductive wires in which current flows in opposite directions close to each other. With such a configuration, the magnetic field Φ6. Φ
In addition to the effect of the above embodiment obtained by canceling each other, the magnetic fields formed around adjacent and opposite currents can be canceled.

Further, FIG. 5 is a diagram showing a third embodiment of the present invention. In this embodiment, the closed loop of the switching circuit is divided into a large number (four in this case) of small area current loops il+12r.
In this case, the magnetic field fluxes Φ1, Φ2, Φ3, and Φ4 of each current loop cancel each other out, and as in the above embodiment, unnecessary radiation noise to the outside is suppressed. Ru.

〔Effect of the invention〕

As described above, according to the present invention, unnecessary radiated noise can be suppressed without using a shield plate or a conductor ring, the number of parts and assembly man-hours are reduced, the device can be made smaller, and This also has the effect of reducing manufacturing costs.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of a switching circuit device according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a switching circuit configured on the substrate of FIG. 1, and FIG. FIG. 4 is an explanatory diagram showing a magnetic field, FIG. 4 is an explanatory diagram showing a second embodiment of the present invention, and FIG. 5 is an explanatory diagram showing a third embodiment of the present invention. T, ------- Output transformer Q -------・Drive transistor (switching element) i, ~i 4+++...Current loop

Claims (3)

[Claims] (1) It has a closed current loop formed by a DC power supply, a primary winding of an output transformer connected to this DC power supply, and a switching element that switches the current flowing through this primary winding, and this closed loop is connected to each other. A switching circuit device characterized in that a wiring pattern is formed so that the current loops are divided into a plurality of concentric current loops and current flows in opposite directions in adjacent current loops. (2) The switching circuit device according to claim 1, wherein the wiring pattern is formed on a printed wiring board. (3) The switching circuit device according to claim 1 or 2, wherein the current loop is formed by bringing conductive wires through which current flows in opposite directions close to each other.