JPH10164385A - Vertical output circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce power consumption by D-class operating a push-pull amplifier. SOLUTION: In order to lower the power consumption, the push-pull amplifier for driving a vertical deflection coil is D-class operated. Vertical sawtooth- shaped waves are converted into pulse signals by a PWM modulator 10 and impressed to the push-pull amplifier. The vertical sawtooth-shaped waves formed based on vertical synchronizing signals are impressed to a terminal 12, PWM- modulated, turned to the pulse signals and impressed to a window comparator 13. First and second comparators 14 and 15 for constituting the window comparator 13 respectively perform the comparison of two input signal levels and impress the compared results to a first transistor 18 and a second transistor 19 as 'H' and 'L.' In this case, so as to prevent the two transistors from being simultaneously turned ON, when the ON/OFF of the transistors are inverted, the two transistors are temporarily turned OFF altogether and then, turned ON.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a vertical output circuit of a TV receiver or a monitor using a cathode ray tube, and more particularly to a vertical output circuit which consumes low power and can prevent destruction of an output transistor.

[0002]

2. Description of the Related Art A vertical output circuit is used to cause a cathode ray tube of a TV receiver or a monitor to deflect vertically. FIG. 2 shows a principle diagram of such a vertical output circuit. A sawtooth wave generated based on the vertical synchronization signal is applied to the terminal (1) in FIG. The sawtooth wave is applied to the transistors (3) and (4) via the transistor (2).
Drive. The transistor (5) turns on and off according to the output signal of the transistor (3), and the transistor (6) turns on and off according to the output signal of the transistor (4).

The sawtooth wave amplified by the transistors (5) and (6) flows as a vertical deflection current to a vertical deflection coil (7), a capacitor (8), and a resistor (9). The vertical deflection coil (7) is attached to a cathode ray tube (not shown) and performs vertical deflection of the electron beam. The idling circuit (10) ensures that the voltage difference between the bases of the transistors (5) and (6) is about 2 VBE (VBE is the rising voltage of the transistor). Due to the presence of the idling circuit (10), an idling current flows through the collector-emitter paths of the transistors (5) and (6) to reduce crossover distortion during switching.

FIG. 2 (10) shows an IC. Therefore, according to the circuit shown in FIG. 2, the vertical deflection in the cathode ray tube can be performed with good linearity.

[0005]

However, in the device shown in FIG. 2, the transistors (5) and (6) perform the class B operation of linearly amplifying the sawtooth wave, so that the power consumption increases. was there.

[0006]

SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and has been described in detail with reference to the drawings showing the preferred embodiments of the present invention.
A PWM modulator that generates a WM wave, a window comparator to which an output signal of the PWM modulator is applied, a push-pull amplifier that operates according to the output signal of the window comparator, and a carrier from the output signal of the push-pull amplifier An integration circuit for removing the component; and a vertical deflection coil driven by an output signal of the integration circuit, wherein a through current is prevented from flowing through the push-pull amplifier according to an output signal of the window comparator. And

[0007]

FIG. 1 shows a vertical output circuit of the present invention. (10) is a vertical sawtooth wave from a terminal (12) using a signal of a horizontal synchronizing signal frequency from a terminal (11) as a carrier. A PWM modulator that PWM-modulates (1) and generates a PWM wave corresponding to the level of the vertical sawtooth wave.
3) is a window comparator including first and second comparators (14) and (15) to which an output signal of the PWM modulator (10) is applied, and (16) is a first comparator (1).
4) a reference voltage source for applying the reference voltage V1 to the second comparator (15), and (17) a first transistor (18) driven in accordance with an output signal of the first comparator (14). And a second transistor (19) driven according to an output signal of the second comparator (15).
And (20) is an integrating circuit for removing a carrier component from the output signal of the push-pull amplifier (17).

In FIG. 1, the same components as those in FIG. 2 are denoted by the same reference numerals, and the description will be omitted. In the present invention, a push-pull amplifier that drives a vertical deflection coil is operated in class D in order to reduce power consumption. According to the present invention, a vertical sawtooth wave is converted to a PWM modulator (1) for class D operation.
0) is converted to a pulse signal and applied to the push-pull amplifier. However, if the class D operation is performed with the class B amplifier circuit configuration as shown in FIG. 2, a large power loss occurs when the two transistors constituting the push-pull amplifier are turned on simultaneously (through current is generated). And sometimes even the breakdown of the transistor.

Therefore, in the present invention, when the on / off of the transistors is reversed, the two transistors are once turned off and then turned on so that the two transistors are not turned on at the same time. Thus, a through current does not flow through the two transistors. A vertical sawtooth wave generated based on the vertical synchronization signal is applied to the terminal (12). The sawtooth wave is PWM-modulated and becomes a pulse signal, which is applied to the window comparator (13). The first and second comparators (14) and (15) constituting the window comparator (13) compare the levels of two input signals, and determine the comparison result as "H" and "L", and set the first transistor (18 ) And the second transistor (19).

FIG. 3 shows this state. Now, it is assumed that a vertical sawtooth wave indicated by a solid line in FIG. 3A is generated, and the reference voltage V1 of the first comparator (14) and the reference voltage V2 of the second comparator (15) are at the levels indicated by the dotted lines. I do. Assume that the time is before time t1 and the level of the vertical sawtooth wave is lower than V1 and V2. Then, the first comparator (14) generates an “L” level and the second comparator (15) generates an “H” level, turning off the first transistor (18) and turning on the second transistor (19). When the second transistor (19) is turned on, current flows from the vertical deflection coil (7) to the collector of the second transistor (19).

Next, between time t1 and time t2,
Assuming that the level of the vertical sawtooth wave is between V1 and V2, the first comparator (14) sets the “L” level,
The comparator (15) generates an "L" level, the first transistor (18) turns off, and the second transistor (19) turns off. For this reason, the state where both transistors are turned off is set in the middle of the switching timing when the second transistor (19) turns off and the first transistor (18) starts to turn on. Thereby, generation of a through current can be prevented, and power loss and destruction can be prevented.

Next, between time t2 and time t3,
If the level of the vertical sawtooth wave is V1 or higher,
The first comparator (14) generates an "H" level and the second comparator (15) generates an "L" level, turning on the first transistor (18) and turning off the second transistor (19). Therefore, current flows from the emitter of the first transistor (18) to the vertical deflection coil (7).

Further, when the time period is between time t3 and time t4, in this case, the window comparator (13) is in the same state as between time t2 and time t3. The shaded portion in FIG. 3B indicates a period in which the first transistor (18) is on, and the shaded portion in FIG. 3C indicates a period in which the second transistor (19) is on. Is shown.

The integration circuit (20) is arranged to remove a carrier component contained in the PWM signal from the push-pull amplifier (17). The integrating circuit (20) is composed of a coil and a capacitor, but may be of any type that exhibits an integrating action. The diodes (21) and (22) are connected to the first transistor (18) and the second transistor (18).
When the transistor (19) is off, it is a flywheel diode for allowing a continuous current to flow through the integration circuit (20).

[0015]

As described above, according to the present invention, since the push-pull amplifier is operated in class D, the power consumption can be reduced. In particular, according to the present invention, when the push-pull amplifier is operated in class D, the transistor is turned off so that a through current does not flow through the push-pull amplifier, so that power loss and destruction can be prevented.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a vertical output circuit of the present invention.

FIG. 2 is a circuit diagram showing a conventional vertical output circuit.

FIG. 3 is a waveform diagram for explaining FIG. 1;

[Explanation of symbols]

 (10) PWM modulator (13) Window comparator (17) Push-pull amplifier (20) Integration circuit

Claims (3)

[Claims] 1. A PWM according to a level of a vertical sawtooth wave.
A PWM modulator that generates a wave, a window comparator to which an output signal of the PWM modulator is applied, a push-pull amplifier that operates in class D according to an output signal of the window comparator, and an output signal of the push-pull amplifier An integration circuit for removing a carrier component; and a vertical deflection coil driven by an output signal of the integration circuit, wherein a through current is prevented from flowing through the push-pull amplifier in accordance with an output signal of the window comparator. Characteristic vertical output circuit. 2. PWM according to the level of a vertical sawtooth wave
A PWM modulator for generating a wave; a window comparator including first and second comparators to which an output signal of the PWM modulator is applied; a first transistor driven according to an output signal of the first comparator; A push-pull amplifier including a second transistor driven in accordance with an output signal of the second comparator; an integration circuit for removing a carrier component from the output signal of the push-pull amplifier; and a vertical driver driven by the output signal of the integration circuit. A vertical output circuit, comprising: a deflection coil, wherein a through current is prevented from flowing through the first and second transistors according to output signals of the first and second comparators. 3. The vertical output circuit according to claim 1, wherein said integration circuit includes a choke coil and a capacitor.