JPH0336224Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] This invention relates to a switching power supply circuit in which converter transformers for remote control power supply and main power supply can be controlled by a common control voltage.

[Conventional technology]

Switching power supply circuits can efficiently adjust power by controlling the on/off time ratio of the switch, and by taking advantage of their small size, light weight, and high efficiency, they can be used in everything from high-precision electronic devices to familiar home appliances. It is even applied to products. The switching power supply circuit 1 shown in FIG. 3 is applied to a television receiver, and is provided with two converter transformers 2 and 3 for a 115 volt main power source and a 12 volt remote control power source. Primary windings 2a and 3a of these converter transformers 2 and 3 receive primary current from a rectifier circuit 6 connected to a commercial power source 5 via a power switch 4.

Control circuits 7 and 8 for controlling on/off of the primary current are connected to the rectifier circuit 6, and these control circuits 7 and 8 are connected to detection windings provided in each converter transformer 2 and 3. The detection voltages detected by windings 2c and 3c are supplied via rectifier/smoothing circuits 7a and 8a, connected to the ground terminals of the respective primary windings 2a and 3a, and turn on/off switching transistors Q ₁ and Q ₂ .
Turn off. Switching transistor for main power supply
Q ₁ is connected to the control circuit 7 via the drive transformer 9, normally open contact 10a of the relay 10, resistor R ₁ and capacitor C ₁ , and the switching transistor Q ₂ for remote control power supply is connected to the resistor R ₂ and It is connected to the control circuit 8 via a capacitor _C2 .

The relay 10 is energized by the transistor _Q3 which is made conductive by the output of the remote control control circuit 11, and the main power source is turned on by closing the normally open contact 10a.

Note that as long as the power switch 4 is closed, the remote control power source is always on, and therefore the main power source can be turned on and off by the output of the remote control control circuit 11. The main power source is obtained by rectifying and smoothing the current induced in the secondary winding 2b of the converter transformer 2 using a diode 12a and a capacitor 12b, and the remote control power source is obtained by rectifying and smoothing the current induced in the secondary winding 3b of the converter transformer 3. The current is rectified and smoothed by a diode 13a and a capacitor 13b.

[Problem that the invention attempts to solve]

In the conventional switching power supply circuit 1 described above, since there is a difference in the output level of the detection windings 2c, 3c of the converter transformers 2, 3, it is necessary to provide separate control circuits 7, 8 for each, resulting in a complicated circuit configuration. In addition, the converter transformer 2 for the main power supply and the converter transformer 3 for the remote control power supply have control circuits 7 and 8 for load fluctuations.
Since the response operations of the converter transformers 2 and 3 are somewhat different, there have been almost no attempts to control both converter transformers 2 and 3 with a common control circuit.

[Means for solving problems]

This idea solves the above problems, and the primary and secondary windings have different winding ratios, and the primary current is supplied from a common rectifier circuit for high-power and low-power applications. A pair of converter transformers, a detection winding for output detection having approximately the same winding ratio with respect to the primary winding provided in each converter transformer, and each detection winding are commonly connected, and a common control output is used to control the pair of converter transformers. Turns on the primary winding of the converter transformer.
The gist of this is that it is constructed from a control circuit that performs OFF control.

[Effect]

This idea supplies the detection voltage induced in each detection winding of two types of converter transformers with different output voltages to a common control circuit, and the output of this control circuit causes a voltage to flow through the primary windings of both converter transformers. The next current is commonly controlled on and off.

〔Example〕

Examples of this invention will be described below. FIG. 1 is a circuit configuration diagram showing one embodiment of the switching regulator of this invention, and FIG. 2 is a control output characteristic diagram of the control circuit shown in FIG. 1.

In FIG. 1, the switching power supply circuit 21 is configured by a single control circuit 22 instead of the conventionally required two control circuits 7 and 8.
The detection output of c is supplied to the control circuit 22 through a common signal line 23. In this embodiment, since the primary windings 2a and 3a of both converter transformers 2 and 3 have the same number of turns, the detection windings 2c and 3c also have the same number of turns. As for the number of windings, the ratio of the primary windings to the converter transformer is 2 or 3.
It is sufficient if the values are the same between the two.

Incidentally, the detected voltages regarding the converter transformers 2 and 3 are supplied as they are to the control circuit 22 via the common signal line 23, but the control circuit 22
Of the two types of control voltages, the one with the larger voltage value is accepted as the detection voltage.

Here, as shown by the solid line in FIG. 2, the control output characteristic of the control circuit 22 is such that the ratio of the optimum control voltage V _c to the detection voltage V _d is determined by the converter transformers 2 and 3 to the detection voltage V _dp It shows a characteristic that changes in a binary manner with . That is, in the range of V _d ≧V _dp , in order to give priority to regulation for heavy loads, the control characteristics shown by the dashed line in FIG. 2 are selected in accordance with the converter transformer 2 for the main power supply. On the other hand, in the range of V _d <V _dp , in order to give priority to regulation for light loads, the control characteristics shown by the two-dot chain line in FIG. 2 are selected in accordance with the converter transformer 3 for the remote control power supply.

In addition, the detection voltage that is the boundary of the above control output characteristics
V _dp is determined theoretically or empirically in accordance with expected load fluctuations in the main power supply or remote control power supply.

In this way, the switching power supply circuit 21
supplies the detection voltage induced in each detection winding 2c, 3c of two types of converter transformers 2, 3 with different output voltages to a common control circuit 22, and the output of this control circuit 22 causes both converter transformers 2, 3 to have different output voltages.
Since the primary current flowing through the primary windings 2a and 3a of 3 is commonly controlled on/off, it is different from the conventional 2.
The only thing required is the control circuit 22, and the detection windings 2c and 2c for the primary windings 2a and 3a,
By setting the turns ratio of 3c to the same value for both converter transformers 2 and 3, good control is possible with the control output of the same duty, and the number of turns is the same between the primary windings 2a and 3a. By doing so, the design can be further simplified.

[Effect of idea]

As explained above, according to this invention, the detection voltage induced in each detection winding of two types of converter transformers with different output voltages is supplied to a common control circuit, and the output of this control circuit is used to control both converter transformers. Since the primary current flowing through the primary winding of the primary winding is commonly controlled on/off, only one control circuit is required compared to the conventional two, and the detection winding is connected to the primary winding. By setting the ratio to almost the same value for both converter transformers, good control is possible with the same duty control output, and by making the primary winding the same number of turns, the design is further simplified. It has excellent effects such as being able to achieve the following.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the switching regulator of this invention, and FIG.
The control output characteristic diagram of the control circuit shown in FIG. 3 is a circuit configuration diagram showing an example of a conventional switching regulator. 2, 3...Converter transformer, 2a, 3b...
...Primary winding, 2b, 3b...Secondary winding, 2c, 3
c...Detection winding, 21...Switching power supply circuit, 22...Control circuit, 23...Signal line.

Claims (1)

[Scope of utility model registration request] A pair of converter transformers, one for high power and one for low power, whose primary and secondary windings have different winding ratios and receive primary current from a common rectifier circuit, and a primary transformer installed in each converter transformer. Each detection winding is commonly connected to a detection winding for output detection having substantially the same winding ratio to the winding, and the primary windings of the pair of converter transformers are controlled on/off by a common control output. A switching power supply circuit consisting of a control circuit.