JPH0411406Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a power supply device for a television receiver, and in particular, it is designed to supply voltage from a DC stabilized power supply to a horizontal deflection circuit using a ringing-choke converter method. This is what I did.

[Prior Art] As recent electronic devices become lighter and more compact, the configuration of their power supply sections is also required to be smaller, lighter, and more efficient, and television receivers are no exception.

FIG. 1 shows an example in which a conventional ringing current converter type DC stabilized power supply circuit is used in a television receiver.

In FIG. 1, AC voltage from a power outlet 1 is converted to DC by a diode rectifier 2,
After being smoothed by the capacitor 3, it is applied to the primary winding 4 of the converter transformer 5. This primary winding 4
is connected to the collector of the switching transistor 6, forming an oscillator together with the transistor 6, and the emitter of the transistor 6 is grounded. The energy of the primary winding 4 is transmitted via the secondary winding 7 to a rectifier circuit consisting of a diode 8 and a capacitor 9.

The DC voltage generated in this rectifier circuit is applied to the primary winding 11 of the flyback transformer 10,
It is supplied as the power supply voltage of the horizontal output transistor 12. A horizontal drive signal is applied to the base of this horizontal output transistor 12 from a terminal 13,
The resonant capacitor 15 and the deflection yoke LH resonate due to the switching action with the damper diode 14 and the phase dust, so that a horizontal deflection current flows through the deflection yoke LH.

Also, by switching the horizontal output transistor 12, the secondary winding 16 of the flyback transformer 10
It is configured to generate a retrace pulse, which is rectified to obtain the high voltage EH for the cathode ray tube.

On the other hand, the converter transformer 5 is provided with a detection winding 17, and a voltage similar to the waveform generated in the secondary winding 7 is obtained at the detection winding 17, and the output terminal of a rectifier circuit consisting of a diode 18 and a capacitor 19 is The control signal is derived from the This control signal has a waveform similar to the voltage waveform across the capacitor 9 on the side of the secondary winding 7, and has a waveform similar to that of the voltage across the capacitor 9 on the side of the secondary winding 7.
Base drive circuit 2 that controls the switching time of
0.

The base drive circuit 20 compares the reference voltage with the control signal and acts to stabilize the rectified output voltage on the secondary winding 7 side of the converter transformer 5.

A circuit with such a configuration is a system in which the energy stored in the primary winding 4 during the on period of the transistor 6 is released to the secondary winding 7 during the off period to supply DC voltage to the horizontal output transistor 12. Yes, the off period of the transistor 12 corresponds to the retrace period,
The on period corresponds to the scanning period.

FIG. 2 is a signal waveform diagram of each part to explain the operation of FIG. 1, and VCP is the transistor 12.
retrace pulse voltage at the collector of , VP is the primary winding voltage of transformer 5, IP is the collector current of transistor 6, IB is the base current of transistor 6, IS is the secondary winding current of transformer 5, VS is the secondary The winding voltage is shown respectively.

When the transistor 6 is turned on at time t1 in FIG. 2, the collector current IP flows through the primary winding 4 and increases.At a certain time, it decreases due to the properties of the primary winding 4, but at the previous time t2, it becomes horizontal. Since the output transistor 12 is turned off, it decreases under the influence of the retrace pulse voltage VCP at that time. Then, at time t3, the base current IB decreases and tries to turn off the transistor 6, but the transistor 6 remains on due to the storage charge, so
The current IP rises again. Thereafter, at time t4, transistor 6 is turned off and current IP no longer flows.

1 of converter transformer 5 at times t1 to t4.
The energy stored in the secondary winding 4 is generated in the secondary winding 7 during the off period of the transistor 6, and the secondary winding voltage VS at this time turns on the diode 8 and charges the capacitor 9. . In addition, transformer 5
The magnitude of the secondary winding current IS depends on the level of the current IP just before the transistor 6 turns off.

The voltage across the capacitor 9 is applied to the primary winding 11 of the flyback transformer 10, and the energy is applied to the secondary winding 16. The pulses generated in the secondary winding 16 are rectified to produce a high voltage EH for the cathode ray tube.

For example, when the high voltage EH fluctuates, the primary winding 11
The voltage across the capacitor 9 will also fluctuate. This fluctuation is detected through the secondary winding 7 and the detection winding 17 of the converter transformer 5, and the output voltage of the rectifier circuit consisting of the diode 18 and the capacitor 19 changes. This output voltage is supplied to the base drive circuit 20 as a control signal to control the on/off period of the transistor 6, the voltage generated in the secondary winding 7 of the converter transformer 5, and the voltage across the capacitor 9 is stabilized. do.

[Problems to be Solved by the Invention] The configuration shown in FIG. 1 requires transformers 5 and 10, and since two transformers are provided, it is not suitable for reducing the size and weight of television receivers.

For this reason, a plan to integrate the converter transformer and the flyback transformer has also been proposed. However, since the converter transformer and the flyback transformer are coupled, if the coupling coefficient and turns ratio of both transformers are not set appropriately, the primary winding current of the flyback transformer will increase or decrease due to load fluctuations in the high voltage circuit, for example. The secondary winding current of the converter transformer fluctuates greatly, the ripple in the voltage across the capacitor 9 increases, and unnecessary energy conversion from the flyback transformer to the converter transformer occurs.

Therefore, the present invention integrates the converter transformer and flyback transformer, reduces the effect on the secondary winding current of the converter transformer even when load fluctuations occur, and makes it possible to always obtain a stable output DC voltage. It is an object of the present invention to provide a power supply device for a television receiver in which the coupling coefficient and turns ratio of both transformers are set to optimal values.

[Means for Solving the Problems] In order to achieve the above object, the present invention applies a DC voltage obtained by rectifying and smoothing an AC power supply voltage to the output electrode of a switching transistor through the primary winding of a converter transformer, and A power supply device for a television receiver, which induces a voltage in the secondary winding of the converter transformer by switching the transistor, and applies this induced voltage to the horizontal output transistor via the primary winding of the flyback transformer. The converter transformer and the flyback transformer are wound around one core, the coupling coefficient K of each transformer is set to 0.8 or less, and the secondary winding of the converter transformer and the primary winding of the flyback transformer are This power supply device for a television receiver is characterized in that the turn ratio with the winding wire is set at 1:K.

[Function] In the power supply device of the present invention, a converter transformer and a flyback transformer are wound around one core, and a voltage is induced in the secondary winding of the converter transformer by switching the switching transistor. The induced voltage is applied to the horizontal output transistor via the primary winding of a flyback transformer on the same core. By setting the coupling coefficient K of each transformer to 0.8 or less, and setting the turns ratio of the secondary winding of the converter transformer and the primary winding of the flyback transformer to 1:K, the secondary winding of the converter transformer is The induced voltage in the winding is stabilized against load fluctuations, and the power supply device has high energy conversion efficiency.

[Example] Hereinafter, an example of the present invention will be described with reference to FIGS. 3 and 4.

FIG. 3 shows the circuit configuration of the present invention, and FIG. 4 shows a sectional view of an integrated structure of a converter transformer and a flyback transformer.

In FIG. 3, the same components as in FIG. 1 are denoted by the same reference numerals and detailed explanations are omitted, but the feature is that the converter transformer 5 and the flyback transformer 10 are integrated into one core. Note that winding 2
1 is for synchronizing the switching operation of the switching transistor 6 with the flyback pulse, and supplies the voltage induced in this winding 21 to the base drive circuit 20. This makes the switching frequency of the transistor 6 approximately equal to the horizontal frequency.

On the other hand, the integrated structure of the converter transformer and flyback transformer shown in FIG.
1 as a converter transformer to one leg of the butted part.
The primary winding 4, the secondary winding 7, and the detection winding 17 are wound around the other leg, and the primary winding 11, the secondary winding 16, and the winding 21 as a flyback transformer are wound around the other leg.
is being wound around. Note that 24 and 24 are cores 22 and 2.
By adjusting the size of this gap 24, the coupling coefficient K between the converter transformer and the flyback transformer can be set to a predetermined value.

Further, the turns ratio between the secondary winding 7 of the converter transformer and the primary winding 11 of the flyback transformer is such that when the secondary winding 7 is 1, the primary winding 11 is K or less. (In the following description, the secondary winding 7 of the converter transformer will be referred to as the converter secondary winding 7, and the primary winding 11 of the flyback transformer will be referred to as the flyback primary winding 11.)

The operation of the power supply device using the integrated transformer as described above will be explained with reference to FIGS. 5 and 6.

In FIG. 5, a to c indicate the case where the turns ratio is not set to an appropriate value in the circuit of FIG. 3, Ip is the collector current of transistor 6, IS is the current of converter secondary winding 7, and VS is converter 2
The voltage of the next winding 7 is shown respectively. Also the fifth
FIG. d shows the current IS in the converter secondary winding 7 when the turns ratio is set to an appropriate value.

6 shows an equivalent circuit when the horizontal output transistor 12 or the damper diode 14 is on, and the coil L in FIG. 6 is the mutual inductance between the converter secondary winding 7 and the flyback primary winding 11. It is.

The period during which the current IS flows through the converter secondary winding 7 corresponds to the scanning period, so the horizontal output transistor 12 or the damper diode 14 is on, and the equivalent circuit at that time is the flyback 1 as shown in FIG. Converter secondary winding 7 to next winding 11
The voltage across the capacitor 9 on the side is applied. Therefore, the number of turns of the flyback primary winding 11 is NL, and the number of turns of the converter secondary winding 7 is NS.
If the coupling coefficient of both windings 7 and 11 is K, then
The effective turns ratio n between NL and NS is n=K・NS/NL (1). Also, the current flowing through the converter secondary winding 7
Assuming that the initial value of IS is IS1, IS=n·EB−EB/Lt+IS1 =(n−1)EB/Lt+IS1 (2). In the above equation (2), (n-1)EB/Lt represents the slope of the current; when n<1, the current IS gradually attenuates from the initial value IS1, and when n>1, the current IS
gradually increases from the initial value IS1. When n=1, the slope remains zero, that is, the initial value IS1.

To explain this with reference to FIG. 5, if the effective turns ratio n is smaller than 1 (n<1), for example, when the high voltage EH fluctuates, the current in the flyback primary winding 11 also fluctuates and the The waveform will be as shown in Figure 5 a or b. That is, when the load current is large as shown in FIG.
5 becomes zero.

The magnitude of the initial value IS1 depends on the level of the collector current Ipe immediately before the transistor 6 is turned off, and if the number of turns of the converter primary winding 4 is NP, then IS1=Ipe·NP/NS.

Furthermore, when n<1, when the load current is small, the collector current IP becomes small as shown in Figure 5b, and the current IS in the converter secondary winding 7 decreases from the low initial value IS1, so the off-period It becomes zero in the middle. At this time, converter secondary winding 7
The voltage VS fluctuates drastically, and the voltage across the capacitor 9 becomes a DC voltage with a high ripple rate.

Conversely, when the effective turns ratio n is made larger than 1 (n>1), the current IS in the converter secondary winding 7 gradually increases from the initial value IS1, as shown in FIG. 5c. This phenomenon means that energy is returned from the flyback section to the converter section, resulting in a circuit with very low power efficiency.

On the other hand, in the present invention, the coupling coefficient K is set to 0.8 or less,
Further, the effective turns ratio n is set to 1. In other words, by applying n=1 to the above equation (1) and setting NS=NL/K...(3), if the number of flyback primary windings is set to 0.8 for converter secondary winding 1, then The current IS in the converter secondary winding is calculated from equation (2) above as IS=
IS1, which is a constant value with no slope, as shown in Fig. 5d.

In other words, the current IS only fluctuates up and down in response to fluctuations in the load current, and does not become zero or increase during the off period of the transistor 6, resulting in an extremely stable circuit.

Since this current IS depends on the initial value IS1 and is extremely small, the wire diameter of the converter secondary winding 7 can be small and the capacity of the rectifier diode 8 can also be small. Furthermore, the fact that the current IS is small has the secondary effect of expanding the safe operating area of the switching transistor 6.

Also, consider the aspect of energy conversion efficiency.
When the energy flowing into the primary winding 4 in the converter section is Pp due to the integration of the transformer, Pp=VP・IP(AV)...(4). Note that IP (AV) is the average current.

On the other hand, the energy released by the converter secondary winding 7
Ps is as follows: Ps=EB・IS(AV)...(5) Note that IS (AV) is the average current.

As mentioned above, since the current IS is small, Pp>Ps, and the difference between Pp and Ps is the energy consumed in the flyback section, so
It becomes a device with high energy conversion efficiency.

[Effects of the invention] As explained above, according to the invention, the converter transformer and the flyback transformer are integrated to realize a smaller and lighter power supply, and the coupling coefficient of both transformers and the converter secondary winding are reduced. By setting the turn ratio with respect to the flyback primary winding to a predetermined value, it is possible to provide a power supply device for a television receiver that is stable against load fluctuations and has high energy conversion efficiency.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing a power supply device of a conventional television receiver, FIG. 2 is a waveform diagram for explaining the operation of FIG. 1, and FIG. 3 is a circuit diagram showing a power supply device according to an embodiment of the present invention. Fig. 4 is a sectional view showing the structure of the transformer used in the power supply device of the present invention, Fig. 5 is a waveform diagram for explaining the operation of the present invention, and Fig. 6 is a circuit diagram showing the equivalent circuit of the scanning period of the present invention. be. 4...Primary winding of converter transformer, 6...
Switching transistor, 7... Secondary winding of converter transformer, 11... Primary winding of flyback transformer, 12... Horizontal output transistor,
16...Secondary winding of flyback transformer, 2
2, 23...Core.

Claims (1)

[Claims for Utility Model Registration] A DC voltage obtained by rectifying and smoothing an AC power supply voltage is applied to the output electrode of a switching transistor via the primary winding of a converter transformer, and this transistor is switched to transform the secondary winding of the converter transformer. A power supply device for a television receiver that induces a voltage in a line and applies this induced voltage to a horizontal output transistor via a primary winding of a flyback transformer, wherein the converter transformer and the flyback transformer are connected to each other. Wound around one core, the coupling coefficient K of each transformer is set to 0.8 or less, and the turns ratio of the secondary winding of the converter transformer and the primary winding of the flyback transformer is set to 1:K. A power supply device for a television receiver characterized by: