JPH07162699A - Fly-back transformer - Google Patents

Abstract

PURPOSE:To stabilize a high-voltage output voltage even when a driving frequency is changed and to accelerate the reaction speed of the stabilization of the high-voltage output voltage at a low cost. CONSTITUTION:The ratio (duty factor) of the ON time and OFF time of PWM rectangular wave pulses P12 is changed by a voltage for which the high-voltage output voltage is detected by a resistor 6 for detection and a differential amplifier 9 and a switching element 13 is intermittently controlled by the PWM rectangular wave pulses P12. Basic signals for driving a PWM control circuit 10, that is driving frequency signal pulses Pf, are supplied from an outside and the fundamental frequency of the PWM rectangular wave pulses P12 is changed corresponding to the conditions of the outside.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a flyback transformer device used in a television receiver display monitor device or the like.

[0002]

2. Description of the Related Art Recently, an increasing number of flyback transformer devices have a control circuit for stabilizing a high voltage output voltage.

The structure of a conventional flyback transformer device will be described below with reference to FIG. FIG. 4 is a circuit diagram of a conventional flyback transformer device. 28 is a transformer section. 27 is a primary coil, 35 is a secondary coil, 4 is a rectifying diode for rectifying the pulsed voltage generated in the secondary coil 35, 6 is a detection resistor for detecting a high-voltage output voltage, and 5 is a speed-up capacitor. Yes, the transformer unit 28 is configured by these.

Reference numeral 13 is a switching element, 20 is a damper diode, 26 is a resonance capacitor, 9 is a differential amplifier, and 32 is a + B voltage control circuit. Reference numeral 11 represents a rectangular wave basic signal for operating the switching element 13.

The operation of the flyback transformer device configured as described above will be described below.

For example, high voltage output voltage (high voltage output terminal 29
Voltage) decreases, the voltage at the terminal 30 of the detection resistor also decreases. The change in voltage of the terminal 30 is amplified by the differential amplifier 9 and applied to the input terminal 31 as an input signal of the + B voltage control circuit 32. Then, the output voltage appearing at the output terminal 33 of the + B voltage control circuit 32 increases, and the voltage applied to the terminal 34 of the primary coil increases, so that the voltage of the high voltage output terminal 29 of the secondary coil 35 increases. In this way, the voltage of the high voltage output terminal 29 is stabilized.

When the voltage of the high-voltage output terminal 29 becomes high, the voltage of the terminal 34 of the primary coil becomes low and the voltage of the high-voltage output terminal 29 becomes stable by performing the operation reverse to the above operation. Be converted.

[0008]

However, in the above conventional configuration, when used in a multi-scan type display monitor or the like, for example, the drive frequency of the basic input signal of the flyback transformer device is 30 KHz to 64 K.
When it is necessary to operate in the range of Hz, the voltage of the output terminal 33 of the + B voltage control circuit 32 is set from about 50V to 150V.
Since it is necessary to change the voltage to about V, the circuit configuration of the + B voltage control circuit becomes complicated, the cost becomes high, and the shape becomes large.

Regarding the performance of stabilizing the voltage of the high-voltage output terminal 29, the reaction speed of stabilization is somewhat slower in the conventional configuration, which causes the screen distortion of the display monitor.

Further, depending on the performance of the transformer section, + B
Since the voltage range that must be controlled by the voltage control circuit 32 changes, there is a problem that the inductance of the primary coil 27 of the transformer unit 28 is also greatly restricted.

The present invention has been made in view of the above problems of the prior art. It stabilizes the high voltage output voltage even when the driving frequency changes, is inexpensive, and has a fast reaction speed for stabilizing the high voltage output voltage. It is an object of the present invention to provide a flyback transformer device that does not greatly limit the inductance value of the secondary coil.

[0012]

In order to achieve this object, the present invention changes the ratio (duty ratio) of the ON time and the OFF time of the rectangular wave pulse by the voltage detected by the detecting means for the high voltage output voltage. In the flyback transformer device of the PWM control method in which the switching element is intermittently controlled by the PWM rectangular wave pulse, a basic signal for driving the PWM control circuit is given from the outside.

[0013]

With the above configuration, even if the basic frequency of the PWM rectangular wave pulse is changed according to external conditions, the duty ratio of the PWM rectangular wave pulse changes according to the change of the basic frequency. Even if the drive frequency is changed, it is not necessary to change the value of + B voltage. Therefore, the + B voltage control circuit which is complicated in circuit and high in cost is not required, and the high voltage output voltage can be stabilized only by the PWM control circuit which is simple and inexpensive. Further, in this method, since the drive element of the primary coil is controlled, the reaction speed of high voltage stabilization is superior to the conventional method, and the screen bending of the display monitor does not occur.

Further, the limit of the inductance value of the primary coil of the transformer section can be made smaller than that of the + B voltage control method.

[0015]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. FIG. 1 is a circuit diagram of a flyback transformer device according to an embodiment of the present invention. In FIG. 1, 1 is a transformer part. 20 is a damper diode, 13 is a switching element, 9 is a differential amplifier,
Reference numeral 19 is a + B voltage power supply. Reference numeral 10 is a PWM control circuit.

In the transformer section 1, 2 is a primary coil,
3 is a secondary coil. One end of the primary coil 2 is connected to the + B voltage power supply 19, and the other end is connected to the damper diode 20 and the switching element 13. Reference numeral 4 is a rectifying diode for rectifying the pulsed voltage generated in the secondary coil 3, 6 is a detection resistor for detecting a high voltage output voltage, and 5 is a speed-up capacitor. One end of the detection resistor 6 and the speed-up capacitor 5 is connected to the high voltage output terminal 7, and the other end is connected to the differential amplifier 9 via the resistor.

The PWM control circuit 10 receives the output of the differential amplifier 9 and the drive frequency signal pulse Pf as input,
The basic oscillation frequency of the control circuit 10 is constructed so as to be synchronized with the driving frequency signal pulse Pf. This PW
The output of the M control circuit 10 is connected so as to be a drive input signal of the switching element 13.

FIG. 2 shows the detection voltage terminal 8 to P shown in FIG.
It is an example of a circuit up to an output voltage terminal 12 of the WM control circuit 10. Reference numerals 14 and 15 are comparator ICs, 16 is a volume, and 17 is a zener diode.

The operation will be described below. In FIG.
For example, when the voltage of the high voltage output terminal 7 decreases, the voltage across the detection resistor 6 also decreases, and the voltage of the detection voltage terminal 8 decreases. This signal is transmitted as an input voltage for PWM control via the differential amplifier 9.

Further, since the PWM control circuit 10 operates in synchronization with the driving frequency signal pulse Pf, the pulse signal having the duty ratio corresponding to both the fluctuation of the driving frequency and the fluctuation of the high voltage output voltage of the transformer section 1. Primary coil 2
And is supplied as an input signal of the switching element 13 for driving. When the voltage of the detection voltage terminal 8 decreases, the ON time of the PWM rectangular wave pulse P ₁₂ of the output voltage terminal 12 becomes long and the energy supplied from the primary coil 2 increases, so that the voltage of the high voltage output terminal 7 becomes Get higher When the voltage of the high voltage output terminal 7 rises, the operation is reversed. In this way, the high voltage output voltage is stabilized.

FIG. 2 is a circuit diagram showing an example of the PWM control circuit 10 of the flyback transformer device in one embodiment of the present invention, and FIG. 3 is a waveform diagram showing the signal waveform of each part of the PWM control circuit 10. It will be described in detail with reference to FIGS. 2 and 3.

As shown in FIG. 2, two transistors are installed.
That is, NPN transistor 23 and PNP transistor
Detection time by the star 24 and Zener diode 17
The road is made up. For example, if the high voltage output voltage drops
The voltage at the detection voltage terminal 8 drops and the voltage at the terminal 36
When it drops, the voltage E at the terminal 25 is _{twenty five}
Decreases (voltage E in FIG. 3A)_{twenty five}Points from the solid line
Change to a line).

The drive frequency signal applied to the terminal 21 is also
The signal pulse Pf (pulse whose frequency can be changed) is compared
Input to the IC 14 and the triangular wave signal synchronized with this signal
Issue V ₁₈(The triangular wave signal V shown in FIG.₁₈) Is output from terminal 18.
I will be forced.

Further, the triangular wave signal V ₁₈ at the terminal ₁₈ and the voltage E _{25 at the} terminal 25 are input to another comparator IC 15, and the PWM voltage square pulse P ₁₂ (see FIG. 3) is applied to the output voltage terminal 12 on the output side thereof. Shown PWM square wave pulse P ₁₂ )
Occurs. This PWM rectangular wave pulse P ₁₂ is synchronized with the drive frequency signal pulse Pf input to the terminal 21, and when the voltage of the detection voltage terminal 8 (terminal 36) further decreases, the ratio of its ON time and OFF time ( The duty ratio) is controlled so that the ON time becomes longer.

Since the PWM rectangular wave pulse P ₁₂ serves as the input signal of the switching element 13 shown in FIG. 1, the maximum collector pulse voltage V ₂₂ of the terminal 22 of the primary coil 2 of the transformer section 1 is maximized. The crest value is controlled to be constant, and the voltage of the detection voltage terminal 8 also rises and is stabilized. Further, when the voltage of the detection voltage terminal 8 rises, the above operation is reversed, and the voltage of the detection voltage terminal 8 is stabilized.

Next, a case where the frequency of the drive frequency signal pulse Pf changes will be described. For example, if the cycle of the drive frequency signal pulse Pf becomes longer as shown in FIG. 3B, the cycle of the triangular wave signal V ₁₈ also becomes longer, and the maximum value V ₁₈ max of the triangular wave signal V ₁₈ also becomes higher. Therefore, the period in which the triangular wave signal V ₁₈ exceeds the voltage E _{25 of the} terminal 25 becomes long, and the ON time of the PWM rectangular wave pulse P ₁₂ output to the output voltage terminal 12 of the comparator IC 15 also becomes long. In this case, the OFF time of the PWM rectangular wave pulse P ₁₂ also becomes somewhat longer, but since the ON time becomes longer than that ratio, the ratio of the ON time to the OFF time (duty ratio).
Will change.

Further, in this way, the drive frequency signal pulse Pf
When the voltage E _{25 at the} terminal 25 is lowered by the detection circuit even when the cycle of the pulse is increased (the voltage E ₂₅ changes from the solid line to the dotted line in FIG. 3B), the ON time of the PWM rectangular wave pulse P ₁₂ Becomes longer.

Even if a switching power supply control IC or the like is used as the PWM control circuit 10, the same performance can be obtained.

[0029]

As described above, according to the present invention, since the basic signal for driving the PWM control circuit is given from the outside, even if the basic frequency of the PWM rectangular wave pulse is changed according to the external conditions, the PWM is changed. The duty ratio of the rectangular wave pulse changes according to the change of the fundamental frequency. Therefore, even if the driving frequency is changed, the high voltage output voltage can be stabilized without changing the + B voltage of the flyback transformer device. Moreover, it is an excellent flyback transformer device which has a fast stabilization reaction speed and can solve the problems such as screen bending of the display monitor, and can be provided as a device which is cheaper in cost than the + B voltage control system.

[Brief description of drawings]

FIG. 1 is a circuit diagram of a flyback transformer device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram of a PWM control circuit of a flyback transformer device according to an embodiment of the present invention.

FIG. 3 is a waveform diagram showing signal waveforms of respective parts of the PWM control circuit according to the embodiment of the present invention.

FIG. 4 is a circuit diagram of a conventional high voltage stabilized flyback transformer device.

[Explanation of symbols]

1 Transformer Part 2 Primary Coil 3 Secondary Coil 4 Rectifier Diode 5 Speed-up Capacitor 6 Detection Resistor 7 High Voltage Output Terminal 8 Detection Voltage Terminal 9 Differential Amplifier 10 PWM Control Circuit 12 Output Voltage Terminal 13 Switching Element 14, 15 Comparator Lator IC 16 volume 17 Zener diode 19 + B voltage power supply 20 damper diode Pf drive frequency signal pulse V ₁₈ triangular wave signal E ₂₅ voltage P ₁₂ PWM rectangular wave pulse

Claims (1)

[Claims] 1. A transformer unit comprising a primary coil and a secondary coil for generating high voltage, wherein one end of the primary coil of the transformer unit is connected to a DC power source, and the other end of the primary coil is connected. It has a plurality of rectifying diodes connected to the switching element to obtain a DC high voltage from the pulse voltage generated in the secondary coil of the transformer section, a detection means for detecting the DC high voltage, and a PWM control circuit. However, the PWM control circuit is configured to change the ratio of ON time and OFF time of a rectangular wave pulse having a frequency determined by an externally applied basic signal according to the voltage detected by the detection means and the frequency of the basic signal. However, the flyback transistor is configured to intermittently control the switching element by a rectangular wave pulse controlled by the PWM control circuit. Nsu apparatus.