JPS6239871B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a horizontal deflection circuit used in a television receiver, and relates to a horizontal deflection circuit that effectively absorbs unnecessary ringing vibrations generated in a flyback transformer to reduce brightness and darkness caused by ringing vibrations on the screen of a cathode ray tube. An object of the present invention is to provide a circuit that does not cause vertical stripes.

First, FIG. 1 shows a conventionally used general horizontal deflection circuit. Here, 1 is a flyback transformer, 2 is its primary coil (output coil), 3 is its secondary coil (high voltage coil), 4 is its tertiary coil (pulse generating coil), and 5 is the anode voltage and focus for the cathode ray tube. A diode that rectifies voltage. 6 is a horizontal output circuit connected to the primary coil 2 of this flyback transformer 1, including a horizontal output transistor 7, a damper diode 8, a resonant capacitor 9, a horizontal deflection coil 10,
It has an S-shaped correction coil 11 and the like. A power supply circuit 12 is connected to the primary coil 2 and supplies power to the horizontal output circuit 6.

However, in such a horizontal deflection circuit, a ringing vibration having a high-order resonance frequency of the flyback pulse is generated in the secondary coil 3 of the flyback transformer 1 due to the distributed capacitance and leakage inductance, and its energy is spreads to various circuits through capacitive or electromagnetic coupling,
As a result, there was a problem in that vertical stripes of brightness and darkness were generated on the screen of the cathode ray tube, resulting in a reduction in image quality.

In order to eliminate the brightness and darkness that appears on the screen, a great deal of design time and expense is required, including measures to route printed circuits and lead wires, add circuit components, and adjust the high-order resonance frequency of the flyback transformer. It was necessary.

Therefore, the present invention provides a simple circuit that can eliminate the vertical stripes of brightness and darkness that appear on the screen of a cathode ray tube due to unnecessary ringing that occurs in the flyback transformer. , 3 will be explained.

Note that in FIGS. 2 and 3, parts similar to the conventional ones are given the same reference numerals as in FIG. 1, and explanations thereof will be omitted.

Unnecessary high-frequency ringing vibrations generated in the secondary coil 3 of the flyback transformer 1 flow into the primary coil 2 as a ringing current due to the transformer coupling, but in the present invention, this ringing current is The energy is absorbed by a parallel circuit 15 consisting of a resistor 13 and an inductance 14 connected in series to the primary coil 2 of the transformer 1. That is, when this ringing current passes through the parallel circuit 15, its energy is consumed by the resistor 13.

On the other hand, since the direct current and horizontal frequency sawtooth wave current flowing into the flyback transformer 1 mainly pass through the inductance 14, the horizontal deflection circuit operates with almost no loss.

In this way, only the harmful ringing vibrations are absorbed and quickly attenuated, and the vertical stripes of light and darkness that appeared on the screen of the cathode ray tube are also eliminated.

Note that the parallel circuit 15 of the inductance 14 and the resistor 13 can be effectively connected in series at the part A in the figure, but in that case, a flyback pulse of nearly 1000 _Vpp is applied to the components, so consideration must be given to the insulation design. It takes. Therefore, the voltage is lower when the circuit is connected to the low voltage side as shown in the figure, and component arrangement and insulation design are easier.

Furthermore, if the value L of the inductance 14 is made too large, the step-up efficiency of the flyback transformer 1 will decrease, so it is necessary to make it as small as possible.
In the case of this circuit example, when the inductance L _FBT of the primary coil 2 of the flyback transformer 1 is 3 to 4 mH, the value L of the inserted inductance 14 is 50 to 60 μH, and the value of the resistor 13 is 100 to 200 Ω, the secondary coil The high-order resonance frequency that occurs in 3 is 500-600KHz.
Good results have been obtained in these cases.

Next, the primary coil 2 of the flyback transformer 1
The equivalent circuit when looking at the horizontal output circuit 6 from the side of In return, the impedance Z _cr =1/ _ω〓cr of the resonant capacitor 9 can be regarded as a short state because the angular frequency ω〓 of the ringing current is large, and furthermore, if the inductance of the deflection coil 10 is L _DY , then
Since this impedance Z _LDY =ω〓L _DY has a large ω〓, it can be regarded as an open state, and the inductance L ₁ of the primary coil 2 and the inductance 1
Since the value L of 4 satisfies L ₁ >>L, the only elements that effectively act on the ringing current are the inductance 14 and the resistor 15, which can be written as shown in FIG. Here, I(ω〓): Ringing current ω〓: Angular frequency of ringing current L, R: Value of inductance and resistance connected in series to the primary coil of flyback transformer I _R : Ringing current flowing through resistor R P _R : If the power consumed by the resistor R is I _R = jω〓L/R+jω〓L・I(ω〓)=jω〓L・I(ω〓)/R ² +ω〓 ² L ²・(R−jω 〓L) =(ω〓 ² L ² /R ² +ω〓 ² L ² −jω〓LR/R ² ω〓 ² L ² )・I(ω〓) |I _R |=ω〓 ² L ² /R ² +ω〓 ² L ²・I(ω
〓) Therefore, P _R = | I _R | ²・R=ω〓 ⁴ L ⁴ R/(R ² +ω〓 ² L ² ) ²・I(ω〓) ² ∂P _R /∂R=ω〓 ² L ² −3R ² /(R ² +ω〓 ² L
² ) ³・I(ω〓) ² The value of R at which P _R becomes maximum is when ∂P _R /∂R=0, and ω〓 ² L ² −3R ² = 0, that is, When P _R becomes maximum, the ringing energy attenuates quickly and the effect becomes maximum.

As described above, according to the present invention, unnecessary ringing vibrations occurring in the flyback transformer can be effectively absorbed by the parallel circuit of the resistor and inductance connected in series with the primary coil without adversely affecting the horizontal deflection operation. Therefore, it is possible to obtain a useful horizontal deflection circuit that can reproduce a good screen without deterioration of image quality such as the occurrence of vertical stripes on the screen of a cathode tube.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a conventional horizontal deflection circuit, FIG. 2 is a circuit diagram of a horizontal deflection circuit according to an embodiment of the present invention, and FIG. 3 is a partial equivalent circuit diagram thereof. 1...Flyback transformer, 2...Primary coil, 3...Secondary coil, 6...Horizontal output circuit, 1
2...Power supply circuit, 13...Resistance, 14...Inductance, 15...Parallel circuit.

Claims (1)

[Claims] 1. A parallel circuit of resistance and inductance is connected in series to the low potential side of the primary coil of a dry flyback transformer, and the relationship between resistance and inductance is expressed as √3R=w〓L, L≪L _FBT , w 〓≫w〓 Where, R: Value of connected resistance L: Value of connected inductance w〓: Angular frequency of higher-order resonance generated in flyback transformer L _FBT : Value of inductance of primary coil of flyback transformer w 〓: A horizontal deflection circuit characterized by using the angular frequency of the fundamental resonance of a flyback transformer.