JPS584351Y2 - Suiheihenkoshiyutsuriyokutransistornorayshinkairo - Google Patents

Description

[Detailed description of the invention] A horizontal deflection circuit in a transistor horizontal deflection circuit configured to flow a sawtooth current for horizontal deflection into a horizontal deflection coil using a horizontal deflection output transistor and a damper diode that perform a switching operation in a horizontal scanning period. The deflection output transistor operates in a saturation region and a cutoff region during switching operations.

By the way, in order to operate the horizontal deflection output transistor in the saturation region and the cut-off region, the input base current required in each operating state is, if it is in the saturation region, the input base current ib+ as described above. An input base current ib□ is required as shown in equation (1), and if it is in the cutoff region, the input base current ib□ needs to be as shown in equation (2) above.

(However, in the above equations (1) and (2), hf
e is the parameter of the horizontal deflection output transistor h, Icp
is the peak collector current of the horizontal deflection output transistor.

) Normal television receivers use large picture tubes, which require a considerable amount of horizontal deflection power to project the image, and horizontal deflection output transistors are required. The peak collector current of the horizontal deflection output transistor is also large, and therefore the input base current to the horizontal deflection output transistor, which is required to drive the horizontal deflection output transistor, is also of a considerably large value.

Therefore, conventionally, the output of the transistor in the excitation stage is normally provided to the base of the horizontal deflection output transistor via an excitation transformer.

However, in general, when a transformer is used as a component of a circuit, a large space is required for the presence of the transformer in the circuit configuration, and the transformer has an ideal conversion efficiency. Because of this, the use of transformers causes power loss, and since transformers are expensive compared to other parts, they are also a problem from a cost perspective.

On the other hand, in a television receiver using a small picture tube, the horizontal deflection power required to project an image is small, so the peak collector current value of the horizontal deflection output transistor is small. In that case, it is also possible to use a transistor with a large value of hre, and the input base current to be given to the horizontal deflection output transistor that operates to flow the necessary horizontal deflection current to the horizontal deflection coil. Since the value may be small, it is considered possible in such a case to configure the circuit in such a way as to avoid the use of an excitation transformer which has various drawbacks as described above.

In the present invention, between the base of the output transistor and ground,
A diode is connected so that the connection polarity is opposite to that of the equivalent diode formed between the base and emitter of the output transistor, and between the base of the output transistor and the collector of the excitation stage transistor, The capacitance value C is (where R is the collector load resistance of the excitation stage transistor, R+ is the input resistance of the output transistor,
■.

2 is the peak collector current of the output transistor, hfe is the h parameter of the output transistor, ■ co is the voltage of the power supply to which the collector load resistor R is connected, and T is the cut-off operation period of the transistor in the excitation stage) Equation (a) above By connecting a coupling capacitor with a capacitance value greater than or equal to the value indicated by The constant is
The charging time constant circuit is sufficiently long compared to the cut-off operation period of the transistor in the excitation stage, and the required forward base current is supplied to the output transistor through the charging time constant circuit during the cut-off operation period of the transistor in the excitation stage. The present invention provides an excitation circuit for horizontal deflection output transistors to solve the above-mentioned problems, and the details thereof will be described in detail below with reference to the accompanying drawings.

FIG. 1 is a circuit diagram of an embodiment of the excitation circuit for the horizontal deflection output transistor of the present invention, in which Ql is the excitation stage transistor (hereinafter referred to as transistor Q1), and Q2 is the horizontal deflection output transistor (hereinafter referred to as transistor Q2). ).

A diode D is connected between the base of the transistor Q2 and the ground so that the connection polarity is opposite to that of the equivalent diode formed between the base and emitter of the transistor Q2, and Load resistance R
■ Power supply through.

Transistor Q connected to 0. A coupling capacitor C is connected between the collector of the transistor Q2 and the base of the transistor Q2.

When an excitation pulse is applied to transistor Q1,
Transistor Q1 is made conductive or cut off by the excitation pulse.

FIG. 2(a) shows an example of how the base potential of the transistor Q1 changes.

Now, transistor Q1 is at time t.

When the conduction state is changed to the cutoff state at , the power supply V.

C → Load resistance R → Coupling capacitor C → Transistor Q2
The charging current 11 of the coupling capacitor C is passed through the equivalent diode->ground circuit formed between the base and emitter of
flows.

The charging current 11 of the coupling capacitor C mentioned above is the load resistance R
When the resistance value of is R1, the capacitance value of coupling capacitor C is C, and the input resistance of transistor Q2 is R1, the above equation (3) is obtained.

The transistor Q1 is in a cut-off state from time to to time t1 shown in FIG. The operating state changes accordingly, but the value of the time constant (R + R, )C of the charging time constant circuit, which is composed of the load resistor R, the coupling capacitor C, the input resistor R1 of the transistor Q2, etc. is the cutoff operation period T of the transistor Q1 (noted t in FIG. 2(a)).

−+t1 period, t2 → t3 period, etc.), and even at the time when transistor Q1 changes from a cut-off state to a conductive state (for example, time t1, t3, etc.), the charging current of coupling capacitor C The value of 11 is the base current ib□ of the transistor Q2 shown in equation (1) above.
If the value is greater than or equal to the value of , the required forward base current is supplied to the base of the transistor Q2 during the cutoff operation period of the transistor Q1, and the transistor Q2 is made conductive.

FIG. 2(b) shows an example of how the base potential of the transistor Q2 changes.

A coupling capacitor C for supplying a base current i5 as shown in equation (1) to the base of the transistor Q2 by its charging current 11 during the cutoff operation period T of the transistor Q1 is as follows. (4)
A capacitance value greater than the capacitance value shown by the formula is required.

Next, considering the case where the transistor Q1 changes from the cutoff state to the conduction state, the potential of the collector of the transistor Q1 is brought to approximately the ground position due to the conduction of the transistor Q1. is discharged in the circuit of coupling capacitor C→collector of transistor Q1→emitter of transistor Q1→ground→diode D→coupling capacitor C.

12 in the figure is a discharge current flowing through the circuit described above.

Then, due to the voltage drop caused by the above-mentioned discharge current 12 flowing through the internal resistance between the anode and cathode of the diode D, the base of the transistor Q2 is biased to a sufficiently negative potential with respect to the ground potential, and the transistor Q2 is ensured to be cut off during the conduction period of transistor Q1.

As is clear from the above explanation, the excitation circuit for the horizontal deflection output transistor of the present invention has an extremely simple configuration that uses only one diode, a coupling capacitor, and a resistor, and can drive the horizontal deflection output transistor well. The circuit of the present invention eliminates the need for an excitation transformer, which was required in the conventional circuit, so the problems of the conventional circuit described above can be solved by adopting the circuit of the present invention. It is resolved well.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an embodiment of an excitation circuit for a horizontal deflection output transistor according to the present invention, and FIGS. 2(a) and 2(b) are explanatory waveform diagrams. Ql...Excitation stage transistor, Q2...
...Horizontal deflection output transistor, D...Diode, R...Collector load resistance, C...
- Combined capacitor.

Claims (1)

[Claim for Utility Model Registration] A diode is connected between the base of the output transistor and ground so that the connection polarity is opposite to that of the equivalent diode formed between the base and emitter of the output transistor. , and the capacitance value C between the base of the output transistor and the collector of the transistor in the excitation stage is (where R is the collector load resistance of the transistor in the excitation stage, R+ is the input resistance of the output transistor, and Icp is The peak collector current of the output transistor, hfe is the h parameter of the output transistor, ■cc is the collector load resistance R
(T is the cutoff operation period of the transistor in the excitation stage) By connecting a coupling capacitor having a capacitance value greater than or equal to the value shown in equation (a) above, the coupling capacitor described above can be The charging time constant of the time constant circuit consisting of the input resistance of the output transistor, the collector load resistance of the excitation stage transistor, etc. is sufficiently long compared to the cutoff operation period of the excitation stage transistor, and the excitation stage transistor An excitation circuit for a horizontal deflection output transistor, wherein a required forward base current is supplied to the output transistor through the charging time constant circuit over a cut-off operation period.