JPH0870387A - High voltage generating circuit - Google Patents

Abstract

PURPOSE: To obtain a high voltage generating circuit which is capable of coping with the input scanning frequency of a wide range by a simple circuitry and narrowing the voltage variable range of a variable power source circuit so as to suppress maximum voltage within the rating of each element. CONSTITUTION: The horizontal synchronizing pulse inputted from an input terminal 1 is frequency-divided by a frequency divider circuit 4. The frequency division ratio of the frequency divider circuit 4 is switched by a frequency division ratio switching means 14. The frequency-divided horizontal synchronizing pulse is inputted as the drive pulse of a high voltage output circuit 5, a flyback pulse is generated by the primary primary coil (a) and the high voltage output circuit 5 of a flyback transformer 6 and the flyback pulse is boosted by the flyback transformer 6 and high voltage is supplied.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a high-voltage generating circuit used in various display devices such as television broadcasting, high-definition television, workstations, etc., which use a cathode ray tube for displaying a plurality of input scanning frequencies. is there.

[0002]

2. Description of the Related Art FIG. 5 is a block diagram showing a conventional high voltage generating circuit, and shows a high voltage generating circuit of a display device using a cathode ray tube corresponding to a plurality of horizontal scanning frequencies. The high voltage generating circuit includes a high voltage output transistor 50,
A high voltage output circuit 5 including a damper diode 51, a resonance capacitor 52, a flyback transformer 6, a variable power supply circuit 7, and a control circuit 8 are provided.

Next, the operation will be described. The high-voltage output transistor 50 in the high-voltage output circuit 5 receives the voltage pulse of the horizontal synchronizing frequency input from the input terminal 1 to perform switching, and causes resonance of the resonance capacitor 52 and the primary winding a of the flyback transformer 6 and A flyback pulse is generated by the damper diode 51.

The flyback transformer 6 is connected to the collector side of the high voltage output transistor 50, and the other end of the coil is connected to the variable power supply circuit 7. The flyback transformer 6 boosts the flyback pulse applied from the high voltage output circuit 5, rectifies the high voltage output from the secondary winding b, and applies it to the anode of the cathode ray tube 9.

Generally, the relationship among the horizontal scanning frequency fh, the deflection cycle Th, the retrace line period Tr, the power supply voltage Eb, and the value Vp of the flyback pulse is: Th = 1 / fh (1) Vp = (π -(Th-Tr) / 2 * Tr + 1) * Eb (2) Therefore, if the blanking period Tr and the power supply voltage Eb are fixed and the horizontal scanning frequency fh changes, the flyback pulse value Vp is changed. Also changes. Therefore, the high voltage output voltage obtained by boosting the flyback pulse Vp by the flyback transformer 6 also changes. Since the high-voltage output voltage of the high-voltage generating circuit must be kept constant at all times, in a display device using a cathode ray tube corresponding to a plurality of horizontal scanning frequencies, if the flyback transformer 6 is fixed, the flyback transformer 6 has a large voltage. The detection winding c is provided separately from the next winding b,
The voltage induced in the detection winding c is rectified by the diode Dc, smoothed by the capacitor Cc, and further, the control circuit 8 which receives the smoothed output operates the variable power supply circuit 7
Is controlled to keep the high voltage output voltage constant. FIG. 7 is a graph showing the power supply voltage Eb with respect to the horizontal scanning frequency fh when the high voltage output voltage is constant.

[0006]

Since the high voltage generating circuit in the conventional display device using the cathode ray tube corresponding to a plurality of horizontal scanning frequencies is constructed as described above, the formula (2) and the one shown in FIG. From the relationship between the power supply voltage Eb and the horizontal scanning frequency fh, it is necessary to make the output voltage range of the variable power supply circuit 7 wider and higher in order to support a wide range of input horizontal scanning frequencies. However, in order to widen the variable range of the variable power supply circuit and output a high voltage, the circuit scale increases and there is a limit to the high voltage output.
The conventional high-voltage generating circuit has a problem that it cannot support a wide range of horizontal scanning frequencies.

The present invention has been made in order to solve the above-mentioned problems, and can cope with a wide range of input scanning frequencies with a simple circuit configuration, and can change the maximum voltage within the rating of each element. An object of the present invention is to provide a high voltage generation circuit in which the voltage variable range of the power supply circuit is narrowed.

A high voltage generating circuit according to claim 1 of the present invention is provided in a display device using a cathode ray tube for performing display corresponding to a plurality of input scanning frequencies,
High voltage output circuit, flyback transformer, variable power supply circuit,
In a high voltage generating circuit including a control circuit, a frequency dividing switching unit that switches a frequency dividing ratio according to a frequency and a frequency dividing circuit that divides a horizontal synchronizing pulse are provided. It is input as a drive pulse and supplies high voltage to the anode of the cathode ray tube.

Further, the high voltage generating circuit according to claim 2 of the present invention detects the frequency of the input horizontal synchronizing pulse as frequency dividing switching means for switching the frequency dividing ratio according to the frequency in the high voltage generating circuit, and performs frequency division. A frequency division ratio determination circuit for determining the ratio and a frequency division switching circuit are provided, and the frequency division switching circuit switches the frequency division ratio based on the output of the frequency division ratio determination circuit.

A high voltage generating circuit according to a third aspect of the present invention is the high voltage generating circuit, further comprising a power supply voltage switching means for switching the power supply voltage of the variable power supply circuit at the same time as switching the frequency division ratio.

Further, according to a fourth aspect of the present invention, in the high voltage generating circuit, the power source voltage of the variable power source circuit in the high voltage generating circuit is switched at the same time as the switching of the frequency dividing ratio as a power source voltage switching means. And a power supply voltage switching circuit that switches the power supply voltage of the variable power supply circuit based on the output signal thereof.

[0011]

In the high voltage generating circuit according to the first aspect of the present invention, the horizontal synchronizing pulse is divided by the dividing switching circuit according to the frequency to change the dividing ratio of the dividing circuit, and the output voltage of the variable power supply circuit is changed. The frequency should be high enough to generate a high voltage within the range.

Further, in the high voltage generating circuit according to the second aspect of the present invention, the frequency of the horizontal synchronizing pulse is detected in the high voltage generating circuit, and the division ratio is automatically switched.

Further, in the high voltage generating circuit according to claim 3 of the present invention, the variable power supply circuit is switched by the power supply voltage switching circuit at the same time when the frequency is switched, and the power supply voltage corresponding to the frequency is output to output the high voltage output voltage. Stabilize quickly.

Further, in the high voltage generating circuit according to the fourth aspect of the present invention, the frequency of the horizontal synchronizing pulse is detected in the high voltage generating circuit, and the power source voltage of the variable power source circuit is automatically switched.

[0015]

【Example】

Example 1. 1 is a block diagram showing a high voltage generating circuit according to a first embodiment of the present invention. 5, those parts that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

This embodiment is different from the prior art in that the horizontal synchronizing pulse is frequency-divided by a frequency dividing circuit 4 and a frequency division switching signal for inputting a frequency division switching signal for switching to a frequency division ratio according to the frequency. 2 and the frequency division switching circuit 10 for switching the frequency division ratio.

Next, the operation will be described as an example.
The case of the horizontal scanning frequency range of KHz will be described with reference to FIG. FIG. 9 is a graph of horizontal scanning frequency fh vs. power supply voltage Eb in the case of dividing the frequency after 30 KHz by two.

A horizontal synchronizing pulse is input from the input terminal 1, and the frequency dividing circuit 4 divides the horizontal synchronizing pulse according to the frequency. The frequency division ratio is switched by the frequency division switching means 14. The input terminal 2 and the frequency division switching circuit 10 are provided as the frequency division switching means 14, and the frequency division switching signal from the input terminal 2 is input to the frequency division switching circuit 10 to switch the frequency division ratio of the frequency division circuit 4.

The frequency range for switching the frequency division can be divided as shown in FIG. 9, for example. When a wide range of frequencies are input by the conventional high voltage generation circuit, a considerably high power supply voltage is required for high frequency inputs as indicated by the broken line. When the frequency is divided by 2 as shown in FIG. 9, the power supply voltage Eb becomes 3
A power supply voltage corresponding to 0 KHz can support horizontal scanning frequencies up to 60 KHz. The frequency range and the frequency division ratio are determined based on the variable range of the output voltage of the variable power supply circuit 7, the FBT standard, the blanking period Tr, and other constraints.

The divided horizontal synchronizing pulse is input to the high-voltage output circuit 5 to generate a flyback pulse. next,
The flyback transformer 6 boosts the flyback pulse and supplies a high voltage output to the anode of the cathode ray tube 9.

In order to maintain the high voltage output at a constant voltage, the output voltage from the detection winding c of the flyback transformer 6 is detected, and the detected voltage is input to the control circuit 8 to control the output voltage of the variable power supply circuit 7, The high voltage output is kept at a constant voltage.

Second Embodiment FIG. 2 is a block diagram showing a high voltage generating circuit according to a second embodiment of the present invention. 5, those parts that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

The feature of this embodiment different from the conventional example is that the frequency dividing circuit 4 for dividing the horizontal synchronizing pulse and the frequency of the horizontal synchronizing pulse are detected by the dividing switching means 14 to determine the dividing ratio. Frequency division ratio determination circuit 11 and frequency division ratio determination circuit 1
Frequency division switching circuit 1 for switching frequency division circuit 4 according to the output of 1
0 is provided.

Next, the operation will be described with reference to FIGS. 6 and 9. FIG. 6 is a diagram showing an example of the frequency division ratio determination circuit, and FIG. 9 is a horizontal scanning frequency fh when the frequency range is divided into two.
It is a graph of the power supply voltage Eb.

A horizontal synchronizing pulse is input from the input terminal 1, and the frequency dividing circuit 4 divides the horizontal synchronizing pulse in accordance with the frequency. The division ratio is switched according to the frequency. As the frequency division switching means 14, the frequency of the horizontal synchronizing pulse is input to the frequency division ratio determination circuit 11, the frequency division ratio determination circuit 11 determines the frequency division ratio, and based on the output, the frequency division switching circuit. The frequency dividing ratio of the frequency dividing circuit 4 is switched by 10. As an example of the frequency division ratio determination circuit 11, an F / V conversion circuit 21 that changes a frequency into a voltage value as shown in FIG. 6 and voltage comparison circuits 22 to 24 that compare a reference voltage value and an input voltage value are provided, and horizontal synchronization is performed. The voltage comparison circuit compares the output voltage of the F / V conversion circuit 21 with respect to the frequency to determine the frequency division ratio. For example, when the frequency range is divided as shown in FIG. 9, the reference voltage range of the comparison circuit 1 is set within the output voltage range of 15 KHz to 30 KHz by the F / V conversion circuit,
The reference voltage range of the comparison circuit 2 is 30 KHz to 60 KHz.
Set within the output voltage range of. If the NTSC signal (1
When 5.75 KHz) is input, the signal from the comparison circuit 1 is output to the frequency division switching circuit, and the HDTV signal (33.
(75 KHz), the signal from the comparison circuit 2 is output to the frequency division switching circuit. When the input range of the horizontal scanning frequency becomes wide and it is divided into n types of frequency division ratios, n
Individual voltage comparison circuits are provided.

The divided horizontal synchronizing pulse is input to the high voltage output circuit 5 to generate a flyback pulse. next,
The flyback transformer 6 boosts the flyback pulse and supplies a high voltage output to the anode of the cathode ray tube 9.

In order to maintain the high voltage output at a constant voltage, the output voltage from the detection winding c of the flyback transformer 6 is detected, and the detected voltage is input to the control circuit 8 to control the output voltage of the variable power supply circuit 7, The high voltage output is kept at a constant voltage.

Third Embodiment FIG. 3 is a block diagram showing a high voltage generating circuit according to a third embodiment of the present invention. 5, those parts that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

This embodiment is different from the conventional example in that the frequency dividing circuit 4 for dividing the horizontal synchronizing pulse, the division switching means 14, and the output voltage of the variable power supply according to the frequency when the frequency is switched. The input terminal 3 and the power supply voltage switching circuit 12 are provided as the power supply voltage switching means 15 for switching to the voltage.

Next, the operation will be described. FIG. 8 is a timing chart at the time of frequency switching.

A horizontal synchronizing pulse is input from the input terminal 1, and the frequency dividing circuit 4 divides the horizontal synchronizing pulse according to the frequency. The frequency division ratio is switched by the frequency division switching means 14 according to the frequency. At the same time, a voltage control signal for switching to the power supply voltage corresponding to the frequency is input from the input terminal 3 to the power supply voltage switching circuit 12. Further, the frequency division switching signal from the frequency division switching means 14 is also input to the power source voltage switching circuit 12, and the variable power source circuit 7 is controlled so that the power source voltage corresponding to the frequency is output from both signals.

The divided horizontal synchronizing pulse is input to the high voltage output circuit 5 to generate a flyback pulse, and the flyback transformer 6 boosts the flyback pulse to supply the high voltage output to the anode of the cathode ray tube 9.

In order to maintain the high voltage output voltage at a constant voltage, the output voltage from the detection winding c of the flyback transformer 6 is detected, and the detected voltage is input to the control circuit 8 to control the output voltage of the variable power supply circuit 7. , The high voltage output is kept at a constant voltage.

As shown in FIG. 8, since the output voltage of the variable power supply circuit 7 is controlled by the power supply voltage switching circuit 12 when the frequency is switched, the high voltage output voltage is stabilized quickly.

Fourth Embodiment FIG. 4 is a block diagram showing a high voltage generating circuit according to a fourth embodiment of the present invention. 5, those parts that are the same as those corresponding parts in FIG. 5 are designated by the same reference numerals, and a description thereof will be omitted.

This embodiment is different from the conventional example in that it has a frequency dividing means 4 for dividing a horizontal synchronizing pulse, a frequency dividing switching means 14 for switching a frequency dividing ratio according to a frequency range, and a variable power source. The frequency detection circuit 13 and the power supply voltage switching circuit 12 are provided as the power supply voltage switching means 15 that switches the output voltage to a voltage according to the frequency.

Next, the operation will be described. A horizontal synchronizing pulse is input from the input terminal 1, and the frequency dividing operation divides the horizontal synchronizing pulse according to the frequency. The frequency division ratio is switched by the frequency division switching means 14 according to the frequency. At the same time, the frequency after the horizontal synchronizing pulse frequency division is detected by the frequency detection circuit 13 and input to the power supply voltage switching circuit 12. Further, the frequency division switching signal from the frequency division switching means 14 is also input to the power source voltage switching circuit 12, and the variable power source circuit 7 is controlled so that the power source voltage corresponding to the frequency is output from both signals.
Next, the divided horizontal synchronizing pulse is input to the high voltage output circuit 5 to generate a flyback pulse. The flyback transformer 6 boosts the flyback pulse and supplies a high voltage output to the anode of the cathode ray tube 9.

In order to maintain the high voltage output at a constant voltage, the output voltage from the detection winding c of the flyback transformer 6 is detected, and the detected voltage is input to the control circuit 8 to control the output voltage of the variable power supply circuit 7, The high voltage output is kept at a constant voltage.

[0039]

As described above, according to the present invention, the maximum output voltage of the variable power supply circuit can be lowered by dividing the horizontal synchronizing pulse by the frequency dividing circuit and inputting it to the high voltage output circuit. There is an effect that a high voltage output voltage corresponding to various input frequencies can be obtained.

As a means for switching the frequency division ratio, it is automated by determining the frequency division range based on the frequency of the horizontal synchronizing pulse in the high voltage generation circuit and switching the frequency division circuit.

Further, since the power supply voltage of the variable power supply circuit is set to a voltage suitable for the frequency when the horizontal deflection frequency is switched, the reaction to the output is fast and the high voltage output voltage can be quickly stabilized to the specified voltage.

As means for switching the power supply voltage,
It is automated by switching the output of the variable power supply circuit based on the frequency of the horizontal synchronizing pulse.

[Brief description of drawings]

FIG. 1 is a block diagram showing a high voltage generating circuit according to a first embodiment of the present invention.

FIG. 2 is a block diagram showing a high voltage generating circuit according to a second embodiment of the present invention.

FIG. 3 is a block diagram showing a high voltage generating circuit according to a third embodiment of the present invention.

FIG. 4 is a block diagram showing a high voltage generating circuit according to a fourth embodiment of the present invention.

FIG. 5 is a block diagram showing a conventional high voltage generation circuit.

FIG. 6 is an example of a frequency division ratio determination circuit.

FIG. 7 is a graph of power supply voltage Eb vs. horizontal scanning frequency fh in a conventional high voltage generating circuit.

FIG. 8 is a timing chart at the time of frequency switching.

FIG. 9 is a power supply voltage Eb when the frequency range is divided into two.
9 is a graph of horizontal scanning frequency fh.

[Explanation of symbols]

2, 3 input terminals, 4 frequency division circuit, 10 frequency division switching circuit, 11 frequency division ratio determination circuit, 12 power supply voltage switching circuit,
13 frequency detection circuit, 14 frequency division switching means, 15 power supply voltage switching means, 21 F / V conversion circuit, 22 comparison circuit 1, 23 comparison circuit 2, 24 comparison circuit n.

 ─────────────────────────────────────────────────── ─── Continuation of front page (72) Inventor Akihiro Murata No. 1 Baba Institute, Nagaokakyo City Mitsubishi Electric Engineering Co., Ltd. Kyoto office (72) Inventor Yoshiteru Suzuki No. 1 Nagaokakyo Baba Institute, Mitsubishi Electric Co., Ltd. System Development Laboratory

Claims (4)

[Claims] 1. A high-voltage generating circuit comprising a high-voltage output circuit, a flyback transformer, a variable power supply circuit, and a control circuit, which is provided in a display device using a cathode ray tube for performing display corresponding to a plurality of input scanning frequencies, A frequency division switching unit that switches the frequency division ratio according to the above, and a frequency dividing circuit that divides the horizontal synchronizing pulse are provided, and the divided horizontal synchronizing pulse is input as a drive pulse for the high-voltage output circuit, and the anode of the cathode ray tube A high-voltage generating circuit characterized by supplying high voltage. 2. A frequency division switching circuit for switching the frequency division ratio according to the frequency in the high voltage generation circuit, the frequency division ratio discriminating circuit for detecting the frequency of the input horizontal synchronizing pulse and discriminating the frequency division ratio, and the frequency division. 2. The high voltage generation circuit according to claim 1, further comprising a switching circuit, wherein the frequency division switching circuit switches the frequency division ratio based on an output of the frequency division ratio determination circuit. 3. The high voltage generating circuit according to claim 1, further comprising power supply voltage switching means for switching the power supply voltage of the variable power supply circuit at the same time as switching the frequency division ratio. 4. A frequency detection circuit for detecting a frequency after frequency division of a horizontal synchronization pulse as a power supply voltage switching means for switching the power supply voltage of a variable power supply circuit in the high-voltage generation circuit at the same time as switching the frequency division ratio, and an output signal thereof. 2. The high voltage generating circuit according to claim 1, further comprising a power supply voltage switching circuit that switches the power supply voltage of the variable power supply circuit based on the above.