JPH0545108Y2 - - Google Patents

Description

[Detailed description of the invention] <Industrial application field> The present invention relates to a self-excited switching regulator used in a power supply section of an electronic device equipped with a remote control function, such as a color television receiver with a remote control. It is.

<Prior Art> The basic configuration of a conventional self-oscillation type switching regulator is shown in FIG. When the switching transistor Q1 is on, a current I1 intermittently flows from the DC power supply B to the primary winding N1 of the regulator transformer T, and when the switching transistor Q1 is off, the regulator transformer T flows intermittently.
The magnetic energy stored in the secondary winding N2 is released, and the current I2 flowing to the secondary side is rectified by the diode D, smoothed by the capacitor C, and supplied to the load VR.

By the way, in conventional color television receivers with a remote control, a transformer for the remote control is used separately from the main power circuit to supply power during standby operation when the main switch is on and the remote control switch is off. However, as the equipment became larger, the cost also increased. Therefore, in recent years, many power supply circuits have been used that use the same regulator transformer to supply power to a load both during normal operation when the remote control switch is turned on and during standby operation when the remote control switch is turned off.
For example, in a color television receiver with a remote control, power loss occurs during standby mode, and the CRT
Because the horizontal oscillation circuit is not driven for safety at high voltages, the presence or absence of drive of this horizontal oscillation circuit is used to perform free run operation during standby operation, and to enable separate excitation during normal operation. A well-known RCC (ringing choke converter) type power supply circuit has been devised which allows a single transformer to be used for both standby and normal operation.

<Problems to be Solved by the Invention> However, a power supply circuit in which a single transformer is shared during standby operation and normal operation has the following problems. That is, the primary inductance of the transformer and the turns ratio between the primary winding and the secondary winding are set to match the normal operation when the remote control switch is turned on. This is because if it matches, for example, free run operation during standby operation, regulation will not be achieved during normal operation. Therefore, the secondary side load during standby operation is lighter than during normal operation, and is several watts, whereas the secondary side load during normal operation is several tens of watts. At this time, assuming that the input voltage from the DC power supply B is constant, the relationship between the current I1 flowing through the primary winding N1 of the regulator transformer T and the current I2 flowing through the secondary winding N2 is as follows: When the load on the secondary side is light, that is, in standby operation, the condition is as shown in FIG. 3, and when the secondary side load is heavy, that is, in normal operation, the condition is as shown in FIG. In both figures, T _ON
and T _OFF are the on and off periods of switching transistor Q1, respectively, and T is the period. In either case, the duty ratio, which is the ratio of the on-period T _ON of the switching transistor Q1 to the period T, is the same, but as the secondary load becomes heavier, the peak value of the current I1 flowing through the primary winding N1 increases. As the period T increases, the period T becomes larger. That is, the switching frequency of switching transistor Q1 becomes lower. Here, since the inductance of the primary winding N1 of the regulator transformer T is set to match during normal operation, the secondary side load is light during standby operation, so the above-mentioned RCC
As is well known in this type of power supply circuit, the load on the secondary side becomes lighter and the switching frequency of the switching transistor Q1 becomes higher. Therefore, a power loss occurs in the windings N1 and N2 of the transformer T due to skin action, and a power loss due to a capacitance component in the primary circuit of the transformer T increases.

<Purpose of the invention> The present invention was devised in view of these technical issues, and it is possible to increase the inductance of the switching transistor by increasing the inductance on the primary side of the transformer when the load on the secondary side of the transformer becomes lighter. It is an object of the present invention to provide a self-excited switching regulator that can reduce power loss on the primary side of a transformer by lowering the switching frequency.

<Means for solving the problem> The self-excited switching regulator of the present invention has the following features:
In order to achieve the above object, a self-excited switching leg in an electronic device having a remote control function is constructed in which a single regulator transformer is used both during normal operation when the remote control switch is turned on and during standby operation when the remote control switch is turned off. In Yureta,
A series circuit consisting of a switch element and an auxiliary winding wound in such a manner as to reduce the magnetic flux caused by the primary winding when energized is connected in parallel to the primary winding of the regulator transformer, and the switch The device is characterized in that it includes a switching means for turning off the element when the remote control switch is turned off.

<Function> With the above configuration, during normal operation by turning on the remote control switch, the auxiliary winding is electrically connected in parallel to the primary winding of the transformer via the switch element turned on by the switching means. When the auxiliary winding is energized, a magnetic flux is generated in the winding in a direction that reduces the magnetic flux generated by the primary winding. Therefore, the apparent inductance on the primary side of the transformer is
This is the value obtained by subtracting the inductance of the auxiliary winding from the inductance of the primary winding. On the other hand, during standby operation when the remote control switch is turned off, the switch element is turned off by the switching means, so the auxiliary winding is not electrically connected to the primary winding, and the inductance on the primary side of the transformer is This is the inductance of the winding. In other words, during standby operation when the secondary side load is light, the inductance on the primary side of the transformer becomes larger than during normal operation, the switching frequency of the switching transistor does not increase, and the power loss on the primary side of the transformer is reduced. decreases.

<Embodiments> Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings.

In FIG. 1 showing an embodiment of the present invention, the same or substantially equivalent parts as in FIG. 2 are given the same reference numerals. A series circuit of an auxiliary winding N3 and a switch element TR consisting of a triac is connected in parallel to the primary winding N1 of the regulator transformer T. The auxiliary winding N3 and the primary winding N1 are concentrically wound around the same core in different winding directions, as is clear from the winding directions marked with ● marks. Therefore, when the switch element TR is turned on and current flows through the auxiliary winding N3, the auxiliary winding N3 has a direction that cancels and reduces the magnetic flux generated by the primary winding N1 in the same core. magnetic flux is generated. The remote control control section 2 includes a light receiving section that receives a signal transmitted from the remote control switch 3, and when the light receiving signal is input from the light receiving section, it drives a horizontal oscillation circuit and instructs the flyback transformer to operate in oscillation. A photocoupler FC light emitting diode LD is connected to the microcomputer. The microcomputer is designed to output to the light emitting diode LD during standby operation when no light reception signal is input. Photo coupler FC photo transistor
FT has its collector connected to a DC power source B via a resistor R1, and its emitter connected to the base of a switching transistor Q2 of a switch element TR via a base resistor R2. The collector of this transistor Q2 is connected to a DC power supply B via a resistor R3, and is connected to a switch element TR.
connected to the gate.

Next, the operation of the above embodiment will be explained.

When the remote control switch 3 is turned on, a signal transmitted from the remote control switch 3 is received by the light receiving section of the remote control control section 2, and the received light signal is input to the microcomputer, and the horizontal oscillation circuit of the television receiver is activated by the command from the microcomputer. is driven, the flyback transformer oscillates, and normal operation is performed. At this time, since there is no output from the microcomputer to the light emitting diode LD, both the photocoupler FC and the switching transistor Q2 are in the off state. Therefore, a current flows from the DC power supply B to the gate of the switch element TR via the resistor R3, and the switch element TR is turned on, so that the auxiliary winding N3 becomes the primary winding N1 of the transformer T.
are connected in parallel. Here, if the inductance of the primary winding N1 is L1 and the inductance of the auxiliary winding N3 is L3, then the inductance on the primary side of the regulator transformer T during normal operation is the auxiliary winding as described above. The magnetic flux generated by wire N3 is 1
In order to cancel out and reduce the magnetic flux generated by the next winding N1, the appearance becomes L1-L3. However, L1
>There is a relationship of L3.

On the other hand, during standby operation when the remote control switch 3 is turned off, the photocoupler FC is turned on by the output of the microcomputer of the remote control control section 2, and the switching transistor Q2 is turned on. Therefore, the bias applied to the gate of the switch element TR becomes zero and becomes off, and the auxiliary winding N3 is not connected to the primary winding N1. At this time, the inductance on the primary side of the transformer T becomes L1, which is larger than during normal operation.
That is, during standby operation in which the secondary side load of the regulator transformer T is light due to the operation of the remote control switch 3, the inductance on the primary side of the regulator transformer T becomes larger than that during normal operation, and the switching of the switching transistor Q1 increases. The frequency does not become higher than during normal operation. Power loss on the primary side of the regulator transformer T can be reduced. Here, by setting the inductance (L1-L3) of the primary winding N1 and auxiliary winding N3 of the regulator transformer T to match normal operation, a single regulator transformer T can be used. No inconvenience will occur even if it is shared for normal operation and standby operation.

It should be noted that the present invention is not limited to the description of the embodiments described above, and it goes without saying that various embodiments can be considered as long as they do not depart from the scope of the claims. For example, in the embodiment described above, a triax was used as the switch element TR, but a thyristor or a transistor may also be used.

<Effects of the Invention> As detailed above, according to the self-excited switching regulator of the present invention, during normal operation when the remote control switch is turned on, the auxiliary winding is switched on via the switching element that is turned on by the switching means. It is electrically connected in parallel to the primary winding of the Yurator transformer, and the magnetic flux generated in this auxiliary winding reduces the magnetic flux generated in the primary winding, and the inductance on the primary side is changed from the inductance of the primary winding. The value is obtained by subtracting the inductance of the auxiliary winding, and during standby operation when the remote control switch is turned off, the switch element is turned off by the switching means, and the inductance on the primary side becomes the inductance of the primary winding. During operation, the inductance on the primary side can be switched to be larger than during normal operation. Therefore, even though a single regulator transformer is shared during normal operation, it is possible to prevent the switching frequency from increasing during standby operation when the secondary side load is light, and the power loss on the primary side is significantly reduced. It is possible to suppress thermal deterioration of circuit components of peripheral circuits. In addition, the inductance on the primary side can be varied by connecting and disconnecting the auxiliary winding to the primary winding of the transformer, allowing the use of smaller diameter transformer windings, making the entire device smaller and lighter. It has the advantage of being able to

[Brief explanation of the drawing]

Figure 1 is an electrical circuit diagram of an embodiment of the self-excited switching regulator of the present invention, Figure 2 is an electrical circuit diagram of a conventional self-excited switching regulator, and Figures 3 and 4 are respectively FIG. 3 is a diagram showing the relationship between time and the primary current and secondary current of the transformer during standby operation and normal operation in FIG. 2; 3...Remote control switch, T...Regulator transformer, N1...Primary winding, N3...Auxiliary winding, TR...Switch element, FC...Photocoupler (switching means).

Claims (1)

[Scope of utility model registration request] In a self-excited switching regulator for an electronic device having a remote control function, in which a single regulator transformer is commonly used for normal operation when a remote control switch is turned on and during standby operation when it is turned off, the regulator A series circuit consisting of a switch element and an auxiliary winding wound in such a manner as to reduce the magnetic flux caused by the primary winding when energized is connected to the primary winding of the transformer, and this switch element is connected in parallel to a remote control switch. A self-excited switching regulator equipped with a switching means that turns off when the switch is turned off.