JP2000224518A - Display device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a display device that has a switching regulator where power consumption of a power supply circuit in a standby state is minimized by turning off a switching circuit when no horizontal synchronizing signal is in existence and using the horizontal synchronizing signal for a switching signal of the switching circuit when the horizontal synchronizing signal is in existence. SOLUTION: A horizontal synchronizing signal, if any, is given to a buffer circuit 7 via a signal transformer 20. The buffer circuit 7 generates a switching signal to drive a switching circuit 3. The switching circuit 3 converts a DC generated from a smoothing circuit 2 for DC level conversion into an AC and gives the AC power to a load transformer 4. On the other hand, when the horizontal synchronizing signal is lost in a standby mode, no horizontal synchronizing signal is given to the signal transformer 20, Then the buffer circuit 7 gives no switching signal to the switching circuit 3, which produces no AC waveform to give power to the load transformer 4 or the like.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display and, more particularly, to a control of a switching power supply for determining the presence or absence of an applied horizontal synchronizing signal and operating a switching power supply based on the horizontal synchronizing signal.

[0002]

2. Description of the Related Art Demand for personal computers has begun to increase year by year, and accordingly, demand for personal computer displays has also increased. In the personal computer display, power saving and improvement of the power factor have been demanded by the ecology mind which has been increasing in recent years, and switching power supplies satisfying these requirements have become mainstream. In addition, personal computers in offices and the like often remain powered on during working hours, and it is necessary to turn off the power of the personal computer display when the user is not using it. As a method for realizing this, a method of controlling the power on / off in accordance with the presence or absence of input vertical and horizontal synchronization signals has been used.

An example of this kind of prior art is disclosed in Japanese Unexamined Patent Publication No. 8-63.
No. 134 is known. In this patent, the input state of a horizontal synchronizing signal and a vertical synchronizing signal is checked, and the display is configured to be in a normal state, a standby state, a temporary stop state, or an off state depending on the presence or absence of these inputs.

Further, as an example of a switching power supply, Japanese Unexamined Patent Publication No. 9-9174 discloses that a horizontal synchronizing signal (horizontal deflection signal) is used as a driving pulse of the switching power supply, and the pulse width of the driving pulse is widened during standby to reduce the frequency at a lower frequency. Drive it. This is shown in FIG.

In this conventional example, a rectifier circuit 1 for rectifying an AC from a power supply, a smoothing circuit 2 for smoothing a rectified wave, a switching circuit 3 for switching the DC from the smoothing circuit 2 to generate an AC, and a switching circuit. 3, a load-side rectifier circuit 5 for rectifying the transformed AC waveform, a load-side smoothing circuit 6 for smoothing the rectified waveform, and a load-side smoothing circuit 6 for controlling the rectified waveform. A control transformer 13 for generating a power supply, a control rectifier circuit 14 for rectifying an output from the transformer 13, a control smoothing circuit 15 for smoothing a rectified waveform, and a synchronizing signal generation for providing a switching signal to the switching circuit 3. A circuit 9, a variable oscillation circuit 17 for controlling the oscillation frequency of the synchronization signal generation circuit 9,
The microcomputer 12 is driven by a power supply on the load side and controls the oscillation frequency of the variable transmission circuit 17, and the signal coupling circuit 10 transmits a variable frequency signal from the microcomputer 12 to the variable transmission circuit 17 while isolating the DC component of the voltage. .

The operation will be described below. In the standby state, the microcomputer 12 sends a signal for lowering the frequency to the signal coupling circuit 10. The signal coupling circuit 10 transmits a variable frequency signal to the variable transmission circuit 17 without electrically coupling with a photocoupler or the like. In the variable transmission circuit 17, the resistance value or the capacitance value of the oscillation circuit is increased by a semiconductor switch or the like. The synchronization signal generator 9 drives the switching circuit 3 at the oscillation frequency indicated by the variable oscillator 17. Thereby, the power consumption of the switching power supply can be reduced.

[0007]

SUMMARY OF THE INVENTION The above-mentioned patent application Hei 9-91.
In Japanese Patent No. 74, even in the standby mode, the control of the main power supply operates because only the switching frequency is lowered, and the power of the control circuit is consumed. That power was wasted during the waiting period. In addition, the efficiency of the switching power supply tends to deteriorate when the load is light such as in a standby state. Therefore, there is a problem that power loss is not reduced when the switching power supply is used in the standby state.

An object of the present invention is to provide a display having a switching power supply that minimizes power consumption of a power supply circuit during standby.

[0009]

In order to solve the above problems, in a display, a rectifier circuit for rectifying a voltage from an AC power supply, a smoothing circuit for smoothing a rectified waveform rectified by the rectifier circuit, A power supply for converting a rectified DC to an AC, a switching circuit connected to a load transformer, detecting an applied horizontal synchronizing signal, and isolating from a DC level of a signal line a signal transformer; and The output from the transformer for impedance conversion, a buffer circuit for converting the horizontal synchronization signal into a switching signal, and a buffer power supply for driving the buffer circuit, when there is no horizontal synchronization signal, the switching circuit is turned off, When there is a horizontal synchronizing signal, there is provided means for using this signal as a switching signal of a switching circuit.

[0010]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A first embodiment of the present invention will be described with reference to FIG. According to a first embodiment of the present invention, a power supply rectifier circuit 1 for rectifying an AC power supply, a smoothing circuit 2 for removing a high-frequency component of a rectified waveform from the rectifier circuit 1, a horizontal synchronization signal or a synchronization signal from a synchronization signal generation circuit 9. , A transformer 4 for transforming the output voltage of the switching circuit 3, a load-side rectifier 5 for rectifying an AC voltage from the transformer 4, and an output from the load-side rectifier 5. A load-side smoothing circuit 6, a signal transformer 20 that receives a horizontal synchronization signal and sends a signal to a primary power supply without electrical coupling, and a switching circuit 3 that receives a horizontal synchronization signal from the signal transformer 20 It comprises a driving buffer circuit 7, a buffer power supply for supplying power to the buffer circuit 7, and a load 16 for performing signal processing and display of a display.

Next, the operation will be described. If there is a horizontal synchronizing signal, it is transmitted to the buffer circuit 7 via the signal transformer 20. The buffer circuit 7 generates a switching signal for driving the switching circuit 3. The switching circuit 3 converts a direct current generated by the smoothing circuit 2 into an alternating current for the conversion of the DC level, and inputs the alternating current to the load transformer 4. The load transformer 4 transforms the voltage to a voltage used by the load. In the load rectifier circuit 5, for example, a flyback power supply performs rectification with one diode. After the rectification, the load-side smoothing circuit 6 removes high-frequency components from the waveform. The flyback power supply uses an electrolytic capacitor.

The load 16 is a circuit inside the display. In the case of a CRT, for example, an image signal processing circuit 22 for processing an image signal, a high voltage circuit 23 for generating a high voltage for accelerating an electron beam, a vertical and horizontal synchronizing signal , A DY 25 for oscillating an electron beam according to the output of the synchronization signal processing circuit 24, and a CRT 26 for displaying an image. Alternatively, the high voltage circuit 23,
The DY 25 and the CRT 26 are different in the case of a display element such as a liquid crystal panel, a plasma display, or the like.

In this case, since the load side circuit is electrically insulated from the primary side power supply, the ground is not common.
For example, if the personal computer is not used for a while and the horizontal synchronizing signal is cut off due to the standby mode, the signal transformer 20
No horizontal synchronization signal comes in. Then, the buffer circuit 7 does not send a switching signal to the switching circuit 3, and the switching circuit 3 does not create an AC waveform for sending power to the load transformer 4 and the like. Accordingly, the load transformer 4 stops supplying power to the load side.

As described above, by cutting the horizontal synchronizing signal, the entire switching circuit does not consume power, and further, the entire display does not consume power. When returning from the standby state, a buffer power supply 21 for supplying power to the buffer circuit 7 that sends a signal to the switching circuit 3 is required. This will be described with reference to FIGS. 2, 3, and 4, respectively.

FIG. 2 shows the power supply for the buffer taken from the rectifier circuit 1. A buffer transformer 17 for transforming the output from the rectifier circuit 1, a buffer rectifier circuit 18 for rectifying the output from the buffer transformer 17, and a buffer smoothing circuit 19 for smoothing the output from the buffer rectifier circuit 18. Thus, the buffer power supply 21 is formed. Next, the operation will be described. The waveform output from the rectifier circuit 1 is a full-wave rectified waveform and has a ripple of twice the power supply frequency. The amplitude of the fundamental wave of this ripple is about 40 times the original power supply amplitude.
% And can be transformed by the buffer transformer 17. Although not shown in the figure, a low-pass filter or the like for removing high frequencies needs to be provided immediately before the transformer 17. After the voltage transformation, the voltage is rectified by the buffer rectifier circuit 18.

In the case of flyback, it is composed of one diode. After the rectification, it is smoothed to DC by the buffer smoothing circuit 19. An electrolytic capacitor is used for smoothing. This supplies the buffer circuit 7 with driving power sufficient to drive the semiconductor switch of the switching circuit 3 to the buffer circuit. After the output from the rectifier circuit 1, the buffer power supply 21 may be configured by a buffer switching power supply through a buffer smoothing circuit, though not shown.

FIG. 3 shows a buffer power supply 21 similar to FIG.
Is a second example. The difference from the circuit shown in FIG. 2 is that the input of the buffer transformer 17 is taken directly from the AC power supply. The subsequent operation is the same as that of the buffer power supply 21 shown in FIG.

FIG. 4 shows a buffer power supply 21 similar to FIG.
Is a third example. The difference from the circuit shown in FIG. 2 is that the input of the buffer transformer 17 is a horizontal synchronizing signal. Since the horizontal synchronizing signal is alternating current, it can be used as power for driving the circuit. After the voltage is transformed by the buffer transformer 17, the voltage is rectified and smoothed, and power is supplied to the buffer circuit 7. By taking power from the signal in this way, the buffer circuit 7
There is no need to prepare a power supply for Furthermore, the voltage is converted from 2 to 3 times the voltage by a combination of a diode and a capacitor at the time of rectification by the buffer rectifier circuit 18 and is used as a power supply, so that the dynamic range of the buffer circuit 7 can be increased.

FIG. 5 shows a second embodiment of the present invention. FIG.
3 are different from the first embodiment in that a synchronization signal generation circuit 9, a switching circuit 8 for switching a switching signal from the buffer circuit 7 or the synchronization signal generation circuit 9, and a power supply for driving the synchronization signal generation circuit 9 , A control transformer 13 for supplying the control signal, a control rectifier circuit 14, and a control smoothing circuit 15.

Next, the operation will be described. The control transformer 13 converts the AC output from the switching circuit 3 into a voltage used in the control circuit. In the control rectifier circuit 14, rectification is performed by flyback or the like. The control smoothing circuit 15 smoothes the rectified waveform into direct current and supplies power to the synchronization signal generation circuit 9. The switching circuit 8 transmits a switching signal having the same phase as the horizontal synchronization signal to the switching circuit 3 when there is a horizontal synchronization signal and there is no switching signal from the synchronization signal generation circuit 9. The driving power supply of the switching circuit 8 at this time is the same as that of the buffer circuit 7.

When the switching circuit 3 starts to turn on and off in the same phase as the horizontal synchronizing signal, an alternating current is input to the control transformer 13 and a power supply voltage is supplied to the synchronizing signal generating circuit 9. At the same time, power is also supplied to the switching circuit 8, and the switching signal to the switching circuit 3 is switched by the comparator or the like to that from the synchronization signal generation circuit 9. The synchronization signal generating circuit 9 may be either self-excited or separately excited. Thus, the switching circuit 3 can be turned on and off at the switching frequency controlled by the load.

FIG. 6 shows a third embodiment of the present invention. The difference from the second embodiment shown in FIG. 2 is that a microcomputer 12 that uses a power supply from a load-side smoothing circuit 6 to generate a power-on / off signal to a synchronization signal generation circuit 9, and electrically connects the primary side and the load side Signal coupling circuit 10 for transmitting a power on / off signal from the microcomputer to the synchronization signal generating circuit 9 while the power supply of the power supply is disconnected.
And a horizontal synchronization signal detection circuit 11 for detecting the presence or absence of a horizontal synchronization signal.

The operation will be described below. If the horizontal synchronizing signal detection circuit 11 stops detecting the horizontal synchronizing signal,
2 transmits an off signal of the synchronization signal generation circuit 9 to the signal coupling circuit 10. The signal coupling circuit 10 transmits a signal in a state where the signal is electrically cut off by, for example, a photocoupler. The synchronization signal generation circuit 9 receives an off signal by a semiconductor switch or the like, and turns off the synchronization signal generation circuit 9.

Then, since the generation of the switching signal is stopped, the operation of the switching circuit 3 is stopped, and no AC is transmitted to the load transformer 4 and the control transformer 13, so that the entire power supply is turned off. At the time of restart, the horizontal synchronizing signal is applied to the switching circuit 3 as a switching signal via the signal transformer 20, the buffer circuit 7, and the switching circuit 8. Thereafter, the alternating current is transmitted to the load transformer 4 and the control transformer 13, and the entire circuit operates.

[0025]

By using the present invention, it is possible to realize a standby power supply that makes the power consumption of the display almost zero when there is no horizontal synchronizing signal. further,
The display can be restarted from the standby state by inputting the horizontal synchronization signal.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a display according to a first embodiment of the present invention.

FIG. 2 is a circuit diagram showing a first example of a buffer power supply.

FIG. 3 is a circuit diagram showing a second example of a buffer power supply.

FIG. 4 is a circuit diagram showing a third example of a buffer power supply.

FIG. 5 is a circuit diagram showing a display according to a second embodiment of the present invention.

FIG. 6 is a circuit diagram showing a display according to a third embodiment of the present invention.

FIG. 7 is a circuit diagram showing a conventional display.

[Explanation of symbols]

1 rectifier circuit, 2 smoothing circuit, 3 switching circuit,
4 transformer for load, 5 rectifier circuit for load, 6 smoothing circuit for load, 7 buffer circuit, 8 switching circuit, 9 synchronizing signal generation circuit, 10 signal coupling circuit, 11 horizontal sync signal detection Circuit, 12: microcomputer, 13: control transformer, 1
4 ... Rectifier circuit for control, 15 ... Smoothing circuit for control, 16 ... Load, 17 ... Transformer for buffer, 18 ... Rectifier circuit for buffer, 19 ... Smoothing circuit for buffer, 20 ... Transformer for signal,
21: buffer power supply, 22: image signal processing circuit, 23
... High voltage circuit, 24 ... Synchronous signal processing circuit, 25 ... DY, 2
6 ... CRT.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Koji Kito 292 Yoshida-cho, Totsuka-ku, Yokohama-shi, Kanagawa Prefecture F-term in the multimedia system development headquarters of Hitachi, Ltd. 5C026 EA02 5C082 AA01 BC03 CB01 DA76 DA81

Claims (5)

[Claims] 1. A display, comprising: a rectifier circuit for rectifying a voltage from an AC power supply; a smoothing circuit for smoothing a rectified waveform rectified by the rectifier circuit; A switching circuit connected to the signal transformer, a horizontal transformer for detecting the applied horizontal synchronization signal, a signal transformer for insulating the signal line from the DC level, and impedance conversion of the output from the signal transformer for horizontal synchronization. A buffer circuit that converts a signal into a switching signal, and a buffer power supply that drives the buffer circuit,
When there is no horizontal sync signal, turn off the switching circuit,
A display characterized in that when there is a horizontal synchronizing signal, this signal is used as a switching signal of a switching circuit. 2. The display according to claim 1, wherein the buffer power supply includes a buffer transformer having an AC component based on a ripple component from a rectified wave from the rectifier circuit, and an output from the buffer transformer. A display comprising: a rectifier circuit for buffering, and a buffering smoothing circuit for smoothing an output from the buffer rectifier circuit. 3. The display according to claim 1, wherein the buffer power supply includes a buffer transformer for inputting an AC voltage to be input to the rectifier circuit, and a buffer rectifier circuit for rectifying an output from the buffer transformer. And a buffer smoothing circuit for smoothing an output from the buffer rectifier circuit. 4. The display according to claim 1, wherein the buffer power supply comprises: a buffer transformer for transforming an AC component from the horizontal synchronizing signal; and a buffer rectifier circuit for rectifying an output from the buffer transformer. And a buffer smoothing circuit for smoothing an output from the buffer rectifier circuit. 5. The display according to claim 1, wherein the control circuit transformer connected to an output from the switching circuit, a control rectifier circuit for rectifying an alternating current from the control transformer, and the control circuit transformer. 2. A control smoothing circuit for smoothing an output from a rectifier circuit, a switching signal synchronization signal generation circuit using the control smoothing circuit as a power supply, and a switching signal output from the synchronization signal generation circuit when no switching signal is output. A switching circuit for supplying a switching signal from the buffer circuit to the switching circuit and, when a switching signal is output from the synchronization signal generating circuit, a switching circuit for outputting the switching signal preferentially. .