JPH1165506A - Power source device for crt - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power source device for CRT, which is capable of obtaining constant power source voltages as to a high-voltage power source and a low voltage power source and also in which the number of converter circuits is reduced. SOLUTION: This device is provided with a changeover means 14 for connecting either an output voltage V1 of a low-voltage power source circuit 11 or the output voltage Vh of a high-voltage power source 12 to a feed back voltage comparing means 13 and a changeover control means 15 controlling the changeover means 14, so as to connect the output voltage V1 of the low- voltage power source 11 to the feed back voltage comparing circuit 13 only for the starting period and to connect the output voltage Vh of the high-voltage power source circuit 12 to the circuit 13 in a steady-state period.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device for a CRT, and more particularly to a power supply device for a CRT, which requires a plurality of power supply voltages for driving and signal processing, and in which a plurality of power supply voltages are applied to a multi-scan type video device having a large load variation. The present invention relates to a CRT power supply to be provided.

[0002]

2. Description of the Related Art In a video display device using a CRT, stability at a high voltage output of 50 to 200 V DC is required. For example, a supply voltage to a flyback transformer that forms an anode voltage of a CRT is normally supplied stably in response to a change in a video signal by a high-voltage push-pull circuit. For this purpose, it is essential to stabilize the power supply voltage at such a high voltage, and for such stabilization, feedback control for performing voltage feedback of the power supply circuit to the high voltage system is performed.

Further, in a multi-scan display device, which is a display device corresponding to a plurality of scanning methods, the horizontal frequency changes from 15 kHz to 100 kHz. Will occur. In such a display device, a plurality of power supply voltages are required for driving and signal processing, and it is necessary to obtain a stable power supply voltage for each of the plurality of power supply voltages. It is necessary in the safe operation area (ASO) of the circuit that the start-up is performed sequentially. Therefore, there is a need for a converter in which feedback for control is applied to the number of high-voltage outputs among the plurality of power supply voltages. For example, three converters are required for three high-voltage outputs of DC 130 V for a high-voltage circuit, DC 110 V for a horizontal deflection circuit, and DC 80 V for a video circuit.

Further, in the vertical deflection driving circuit, in the case of multi-scan, driving within a range of 30 Hz to about 150 Hz is performed, and the power output load of DC ± 12 V is changed. In addition, the load of NTSC, which is a standard TV system, varies greatly depending on whether it is interlaced drive or double-speed drive. In addition to having to deal with these fluctuation factors, multi-scan compatible devices
A power supply of DC ± 12V and DC ± 8V used for a control circuit and a logic circuit is required. These also require converters, so that a total of five converters are required.

A conventional CRT used in such a display device requiring a plurality of stable power supply voltages and having a converter corresponding to each power supply voltage.
The power supply device for use is described below. FIG. 4 is a diagram showing a main configuration of a conventional CRT power supply device. The CRT power supply device has a standby power supply, has a rectifier circuit on the input side of the converter, and is connected to the CRT as a load on the output side. Not shown.

The illustrated main power supply is composed of first to fifth power supply circuits A41 to E45, which are five power supply circuits connected to an input voltage Vin which is full-wave rectified in this example. In this example, the first power supply circuit A41 forms a high-voltage power supply voltage VOH1 to be supplied to a CRT, for example, DC + 130V, and includes a DC converter 411 and a feedback circuit 412. The second power supply circuit B42 includes a horizontal deflection power supply voltage VOH2 supplied to the CRT,
For example, it forms DC + 110V, and includes a DC converter 421 and a feedback circuit 422. The third power supply circuit C43 forms a video-out power supply voltage VOH3 to be supplied to the CRT, for example, DC + 80V, and includes a DC converter 431 and a feedback circuit 432. The above first
To the third circuits A to C are high-voltage power supply circuits.

The fourth power supply circuit D44 forms a vertical deflection power supply voltage to be supplied to the CRT and a power supply voltage ± VOL1 for driving the video signal and audio signal processing circuits, for example, DC ± 15V. , And a feedback circuit 442. Fourth power supply circuit D
With respect to DC ± 15V formed at 44, control for stabilization to DC ± 12V by a load side circuit is usually performed via a three-terminal regulator. The fifth power supply circuit E45 has a power supply voltage ± VOL2 for a logic circuit such as a signal processing circuit such as a microcomputer, TTL, ROM, etc., for example, DC + 8.
V, and includes a DC converter 451 and a feedback circuit 452. As in the case of the fourth power supply circuit D44, control for stabilization by a load-side circuit to DC ± 5V is normally applied to DC ± 8V formed in the fifth power supply circuit E45 via a three-terminal regulator. Done.

FIG. 5 is a diagram showing a sequence of starting in a power supply device according to the prior art. Regarding the operation at the time of starting the power supply device according to the related art formed as described above,
This will be described below with reference to FIG. In the figure, the horizontal axis represents time, and the vertical axis represents output voltage. 511, 512,
513, 514, 515 are power supply voltages for logic circuits ± VOL
2, drive power supply voltage ± VOL1, horizontal deflection power supply voltage VOH2
, High voltage power supply voltage VOH1, video out power supply voltage VOH3
3 shows a schematic diagram of a voltage waveform at the time of startup.

As described above, the order of starting is determined for a plurality of power supply circuits. That is, in driving the CRT, 1. The power supply voltage for logic circuit ± VOL2 supplied from the fifth power supply circuit E, for example, the power supply voltage for microcomputer ± 8V, Driving / control power supply voltage ± VOL1 supplied from the fourth power supply circuit D, for example, vertical deflection / control power supply ± 15
V, 3. Horizontal deflection power supply voltage V supplied from second power supply circuit B
3. OH2, for example, horizontal deflection power supply voltage +110 V; High voltage power supply voltage VOH supplied from first power supply circuit A
1, for example, a high voltage power supply +130 V; The video-out power supply voltage VOH3 supplied from the third power supply circuit C, for example, the video-out output power supply voltage +80 V, is activated in the order shown in FIG.

As described above, the power supply device for CRT according to the prior art has a power supply circuit having a converter and a feedback circuit for each required power supply voltage. By starting them, a stable starting operation can be ensured.

[0011]

However, in the example of the power supply device according to the prior art as described above, a converter is required for each power supply output. That is, the power supply circuit is constituted by five converters, and the converter also requires the standby power supply which is omitted in the above description. Therefore, when this is added, six converters are actually required. In other words, the power supply components and the area required for the printed circuit board are required to be larger, which is disadvantageous in reducing the size, weight, and cost of the display device. There is also a problem that it is difficult to reduce the power consumption of the display device from the viewpoint that the power loss for control lowers the conversion efficiency of the power supply.

In order to reduce the size of the circuit, a high-voltage power supply and a low-voltage power supply used as a driving power supply are simply replaced by one.
It is not easy to configure as sharing a converter.

First, in this case, it is necessary to provide a voltage feedback system on the high voltage power supply side.
The sharing of converters impairs the downsizing of the circuit and the effectiveness of cost reduction. In addition, when the converter is started, the load on the high voltage power supply side is not started, so that sufficient electric energy is not accumulated in the converter transformer.
Therefore, in a converter transformer having a normal high-voltage output and a low-voltage output, as described above, it is necessary to start up the low-voltage power supply first. Since the electric energy is not stored, the low-voltage power supply cannot reach a predetermined voltage at the time of the start, and there is a problem that the driving circuit cannot operate in a normal sequence.

The present invention has been made in view of the above circumstances, and realizes a high-voltage power supply and a low-voltage power supply to share a converter without causing the above-described problems. It is an object of the present invention to provide a CRT power supply device capable of realizing a small-scale circuit and a low cost in the above.

[0015]

A CRT according to claim 1
The power supply device for CRT is a power supply device for a CRT provided with a converter transformer having a low-voltage power supply circuit and a high-voltage power supply circuit on the secondary side, wherein the output voltage of the low-voltage power supply circuit or the high-voltage power supply circuit is reduced. Voltage feedback means for stabilizing the output voltage by voltage feedback to the primary side of the converter transformer;
And switching means for switching which of the high voltage power supply circuits performs the voltage feedback.

According to a second aspect of the present invention, there is provided a CRT power supply device according to the first aspect, wherein the voltage feedback is performed on an output voltage of the low-voltage power supply circuit during a start-up period, and a steady-state period is provided. And a switching control means for controlling the switching means so as to perform the voltage feedback on the output voltage of the high voltage power supply circuit.

According to a third aspect of the present invention, there is provided a CRT power supply device according to the first or second aspect, wherein the voltage feedback means includes one of the high voltage output voltage and the low voltage output voltage. Comparing means for comparing the output voltage with a preset value and outputting the result of the comparison as a comparison signal; insulating transmission means for transmitting the comparison signal to the primary side of the converter transformer; A converter control means for outputting an on-off duty signal in response to the signal; and an on-off duty signal applied to turn on / off charging and discharging of electric energy to and from the primary side of the converter transformer. And switching means for turning on and off the transmission of energy to the secondary side.

According to a fourth aspect of the present invention, in the CRT power supply device according to the third aspect, the switching means includes an N-type transistor which is a power supply switch for an output voltage from the high voltage power supply circuit. A high-voltage power supply circuit provided between a collector of the n-type transistor and an output voltage of the high-voltage power supply circuit; One or more zener diodes having a zener voltage equal to the voltage difference from the low-voltage power supply circuit.

According to a fifth aspect of the present invention, there is provided the CRT power supply device according to the fourth aspect, wherein the base voltage Vb of the N-type transistor and the P-type transistor is set to:
Vb ≧ Vlo with respect to the low-voltage power supply voltage Vlo in the steady state
And a voltage which is a resistance divided voltage by the divided resistors Rh and Rl provided between the high-voltage power supply voltage Vho in the steady state and the ground, and the switching control means includes a ground-side resistance of the divided resistors. An electric field capacitor provided in parallel with Rl is provided. After turning on the P-type transistor for a predetermined time, the P-type transistor is turned off, and the N-type transistor is turned on at the same time as the P-type transistor is turned off. Things.

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION

Embodiment 1 FIG. The power supply device for CRT according to the first embodiment of the present invention realizes a stable start-up operation by sequentially performing switching between a low-voltage power supply and a high-voltage power supply for feedback control after startup. It is.

FIG. 1 is a diagram showing a main configuration of a CRT power supply device according to the first embodiment. In the figure, reference numeral 19 denotes a converter transformer, which converts a primary voltage of a primary winding 19a into a secondary voltage on secondary windings 19b and 19c, which become a low power supply voltage and a high power supply voltage, respectively. To communicate. Reference numeral 11 denotes a low-voltage power supply circuit, and reference numeral 12 denotes a high-voltage power supply circuit. The low-voltage power supply circuit 11 includes a primary winding 19a of the converter transformer 19,
1 and a smoothing capacitor 112. The high-voltage power supply circuit 12 includes a secondary winding 19 b of the converter transformer 19, a rectifier diode 121, and a smoothing capacitor 122. Reference numeral 13 denotes a feedback voltage comparison unit that compares the input voltage with a predetermined reference voltage and outputs a comparison signal SFB based on the result of the comparison. Reference numeral 14 denotes switching means for changing the voltage to be input to the feedback voltage comparing means 13 into the low-voltage power supply circuit 11,
Alternatively, switching from which of the high voltage power supply circuits 12 is performed. Reference numeral 15 denotes switching control means for controlling switching of the switching means 14. In the power supply device according to the first embodiment, the switching control unit 15 controls the output voltage Vl of the low-voltage power supply circuit 11 only during the startup period immediately after startup.
Is connected to the feedback voltage comparing means 13, and in the subsequent steady period, the output voltage V
h is connected to the feedback voltage comparison means 13.

Reference numeral 16 denotes an insulation transmitting means, which is an LED 16a.
A comparison signal SFB output from the feedback voltage comparison means 13 located on the secondary side of the converter transformer 19 is transmitted to the primary side as an insulated signal. 1
Reference numeral 7 denotes a converter control unit, which includes a power control IC and generates an on-off duty signal Sd. Reference numeral 18 denotes a switching means, which is an N-type transistor. The on-off duty signal Sd is applied to turn on / off charging and discharging of electric energy to and from the primary side of the converter transformer 19. Reference numeral 19 denotes a converter transformer, which converts the primary voltage of the primary winding 19a into a secondary voltage on the secondary windings 19b and 19c that becomes a low power supply voltage and a high power supply voltage, respectively, and transmits the converted voltage. .

When the on-off duty signal Sd generated by the converter control means 17 is applied to the switching means 18 comprising an N-type transistor, a rectifier circuit (not shown) provided on the input side of the converter transformer 19 causes The rectified input voltage Vin is the converter transformer 1
9, the electrical energy charged and discharged to and from the primary winding 19a of the converter transformer 19 is turned on and off by the switching means 18, and the energy input to the primary side is used to turn on and off the switching. Only the power input during the period is transmitted to the secondary side.

Reference numeral 141 denotes a Zener diode.
A voltage difference between a predetermined output voltage Vho of the high-voltage power supply circuit 12 and a predetermined output voltage Vlo of the low-voltage power supply circuit 11, which is provided between the voltage output section of the high-voltage power supply circuit 12 and the switching means 14, Vho- It has a Zener potential equal to Vlo. The zener diode 141 is shown as a single zener diode in the figure, but a plurality of zener diodes may be provided to obtain an appropriate potential. With this configuration, the input voltage to the feedback voltage comparison means 13 is made equal, and comparison with the single predetermined reference voltage Vls is enabled. Here, converter control means 17 and switching means 18
Primary-side hot ground (H
OT GND).

The operation of the thus configured CRT power supply device according to the first embodiment when starting up will be described below. The primary side voltage Vin is converted by the transformer converter 19, and the high voltage power supply circuit 12 outputs the voltage Vh
However, the low voltage power supply circuit 11 outputs the voltage Vl.

As described above, in the startup period immediately after startup, the switching means 14 controlled by the switching control means 15 connects the output voltage Vl of the low-voltage power supply circuit 11 to the feedback voltage comparison means 13. Therefore, during the start-up period, the output voltage Vl of the low-voltage power supply circuit 11 is supplied to the feedback voltage comparing means 13 through the switching means 14.
In the means 13, the output voltage Vl is compared with a predetermined reference voltage Vls, and a comparison signal SFB is output. This comparison signal SFB is composed of a photocoupler,
The signal is input to the converter control means 17 via the insulation transmission means 16 for transmitting the signal insulated between the primary side and the secondary side, and the converter control means 17 outputs an on-off duty signal in accordance with the comparison signal SFB. S is generated and the on-
When the off-duty signal S is applied to the base of the switching means 18, the switching operation of the converter transformer 19 is performed.

As described above, during the start-up period, the output of the low-voltage power supply circuit 11 is input to the feedback voltage comparison means 13 so that the voltage feedback control for the low-voltage power supply circuit is performed. After the startup of the load is completed and the startup period has elapsed, the inrush current to the low voltage circuit will not flow thereafter. Here, during the inrush current period to the low-voltage circuit during the start-up period, since a low-voltage voltage feedback is applied, a stable output voltage is obtained. On the other hand, since the load circuit of the high-voltage circuit has not been started, only a fraction of the steady-state current flows through the high-voltage circuit.

Subsequently, after a predetermined time, for example, 500 ms, the switching control means 15 controls the switching means 14 to switch the input to the feedback voltage comparing means 13. As a result, the output voltage Vh of the high voltage power supply circuit 12 is input to the feedback voltage comparison means 13 via the switching means 14 after the voltage is reduced by Vho-Vlo by passing through the Zener diode 141. Then, the feedback voltage comparison means 13 compares the voltage with the same reference voltage Vls as when the voltage feedback control was performed on the low-voltage circuit,
As a result of the comparison, a comparison signal SFB is output. The comparison signal SFB is transmitted through the insulating transmission means 16 in the same manner as described above.
The ON / OFF duty signal Sd is input to the converter control means 17 and is generated by the converter control means 17 and applied to the base of the switching means 18 to perform the switching operation of the converter circuit 10. At a certain time after the switching, for example, 30 ms later, the high-voltage load starts, an inrush current flows, and the load becomes a steady load. During this time, the voltage is fed back by the output voltage Vh, so that the voltage is stably output even during the inrush current period, and the high-voltage load can be started normally. On the other hand, the output voltage of the low-voltage power supply circuit increases during an inrush current period due to a high-voltage load, but is usually made constant by, for example, a three-terminal regulator provided on the load side.

As described above, the CRT according to the first embodiment
According to the power supply device for feedback, the feedback voltage comparing means 13
Is switched by the switching means 14 and the switching control means 15 so as to be one of the outputs of the low-voltage power supply circuit 11 and the high-voltage power supply circuit 12. Performs feedback control on the power supply circuit to stabilize the output voltage of the low-voltage power supply circuit, and after switching, performs feedback control on the high-voltage power supply circuit to enable stable voltage supply from the high-voltage power supply circuit And the output voltage of the low-voltage power supply circuit is, for example, A
It can be stabilized by VR (Automatic Voltage Regulator) means, and the effect that two converters required for a low-voltage power supply and a high-voltage power supply can be rationalized to one is obtained.

Embodiment 2 FIG. The power supply device for a CRT according to the second embodiment of the present invention has the same function as the power supply device according to the first embodiment, and shows a specific circuit configuration of a functional portion of the device according to the first embodiment. is there. FIG. 2 is a diagram showing a main configuration of a CRT power supply device according to the second embodiment. In the figure, an N-type transistor 212 and a P-type transistor 211 correspond to the switching means 14 in the first embodiment shown in FIG. 1, and a time-constant capacitor 215 corresponds to the switching control means 15. It is. The equivalent of the feedback control means 13 is a Zener diode 221, an N-type transistor 222, resistors 214 and 223. The resistor 161 is provided as a current limiting resistor for the comparison signal SFB. The resistors 213 and 224 are for adjusting the output of the high-voltage power supply circuit. Other Embodiment 1
Is the same as

As for the operation of the CRT power supply device according to the second embodiment at the time of starting, similarly to the first embodiment, a stable output voltage can be obtained by switching the target of feedback control. Only the differences from the first embodiment will be described below.

In the second embodiment, the switching operation by the switching means 14 of the first embodiment is performed as follows. As shown in the figure, the power supply switch from the low-voltage power supply circuit 11 of +15 V to the feedback voltage comparison means 13 is a P-type transistor 211, for example, +130 V
The power supply switch from the high voltage power supply circuit 12 to the feedback voltage comparison means 13 is an N-type transistor 212. Then, the base voltage Vb of the transistors 211 and 212 was formed from the resistance divided voltage of the high voltage output voltage in the steady period formed by the resistors Rh213 and Rl214. Since the divided voltages have a relationship of Vb ≧ V1, for example, Rl = 68 kΩ and Rh = 1
In the case of 00 kΩ, Vb = 16.7 V, and since the emitter voltage of the P-type transistor 211 is Ve = 15 V, its base voltage is 16.7 V (Vb).
Is turned off. on the other hand,
The emitter voltage of the N-type transistor 212 is Ve = 15V
, The base voltage is 16.7 V (V
The N-type transistor 212 shown in b) is turned on, and as a result, the high-voltage power supply voltage is fed back.

In the second embodiment, the switching control operation by the switching control means 15 of the first embodiment is as follows. For example, if the time constant capacitor 215 has a capacitance of about 47 μF, the P-type transistor 211 is in an on state due to the relationship of emitter voltage ≧ base voltage during a period of about 500 ms from the start, and the low-voltage power supply voltage is Feedback will be given. On the other hand, the N-type transistor 212 is off because its base voltage ≦ emitter voltage.

Further, in the second embodiment, the operation of outputting the comparison signal by the feedback voltage comparing means 13 of the first embodiment is as follows. For example, a Zener diode 2 having a Zener voltage of 14.5 V as the reference voltage Vls
21 shall be used. For generating a zener voltage, a zener current of 3.5 mA is passed from the high-voltage power supply output Vh via a resistor Rz224, for example, 33 kΩ, to obtain a zener voltage of 14.5 V as a reference voltage.

The output lines of the P-type transistor 211 and the N-type transistor 212 are connected to, for example, the collector of an N-type transistor 222, and the emitter is connected to the cathode of the Zener diode 221.
The comparison signal SFB is formed by turning on and off the transistor 222 of the type. The base of the transistor 222 is
For example, it is connected to its collector via a base resistor R223 of 22 kΩ.

The transistor 222 has a base-emitter voltage VBE = 0.5 V, a collector-emitter voltage VCE = 0.
Assuming that the voltage is 5 V, the transistor 222 is turned on when Vl ≧ Vls + VBE = 15 V. On the other hand, Vl ≦ Vls + V
When BE = 15V, the transistor 222 is turned off. Therefore, when the transistor 222 is turned on and off, the amount of current supplied to the LED 16a side of the photocoupler 16 changes, and this forms the comparison signal SFB. Resistance Rr16
Reference numeral 1 denotes, for example, 3 kΩ inserted as a current limiting resistance of the current flowing through the LED 16 a of the photocoupler 16.

The comparison signal SFB is transmitted to a converter control means 17 comprising, for example, a power supply control IC via a photocoupler 16 comprising an LED 16a and a phototransistor 16b as an insulation transmission means for insulating and transmitting the signal. Here, an on-off duty signal Sd for driving the switching transistor 18 is generated and input to the switching transistor 18 as a base voltage.
Therefore, the switching transistor 18 is turned on / off by the on / off duty signal to turn on / off the charging / discharging of the electric energy input to the primary side of the converter transformer 19, so that the secondary side of the converter transformer 19 is turned on / off. Transfer of energy to the body can be controlled.

As described above, the CRT according to the second embodiment
In the power supply device for use, the circuit configuration shown in FIG. 2 is employed. For example, during the period of 500 ms from the start-up, the output voltage Vl from the low-voltage power supply 11 is used. Since the voltage feedback to the primary side of the converter transformer is performed by the output voltage Vh, the startup operation similar to the power supply device according to the first embodiment, in which the low-voltage load circuit and the high-voltage load circuit are normally started up sequentially. Is possible.

FIG. 3 is a diagram for explaining the effect of reducing the circuit scale in the power supply device for CRT according to the first and second embodiments. FIG. 1A is a schematic diagram schematically showing the configuration of the power supply device according to the conventional technique shown in FIG. As shown in the figure, a first converter having one converter is provided for each of three types of high-voltage power supplies and two types of low-voltage power supplies.
To 5th power supply circuits A to E. Same figure
(b) is a schematic diagram showing an application example of the CRT power supply device according to the first or second embodiment. As shown in the configuration of X corresponding to A + D in FIG. 10A and the configuration of Y corresponding to B + E in FIG. 10A, the same converter uses a high voltage power supply (VOH1, VOH).
2) By sharing the low-voltage power supply (VOL1, VOL2) with the low-voltage power supply (VOL1, VOL2), the overall circuit size can be reduced by combining Z corresponding to C in FIG. Things. Accordingly, this has the effect of reducing costs and reducing the required area of the printed wiring board.

In the first and second embodiments,
Although an N-type transistor is used as the switching means 18, the configuration of the CRT power supply device according to the present invention is not limited to this.
Alternatively, a configuration using a MOSFET transistor is also possible, and the same effect can be obtained.

[0041]

As described above, according to the CRT power supply device of the first aspect, the CRT power supply device includes the converter transformer having the low-voltage power supply circuit and the high-voltage power supply circuit on the secondary side. Voltage feedback means for stabilizing the output voltage by voltage feedback of the output voltage, and switching means for switching which of the low-voltage power supply circuit and the high-voltage power supply circuit performs the voltage feedback. Although two converters were conventionally required to provide a low-voltage power supply and a high-voltage power supply, this can be configured with a single converter, thereby reducing costs and reducing equipment costs. It is possible to reduce the size.

According to the CRT power supply device of the second aspect, in the CRT power supply device of the first aspect, during the start-up period, the voltage feedback is performed on the output voltage of the low-voltage power supply circuit, and In the period, the apparatus further includes switching control means for controlling the switching means so as to perform the voltage feedback on the output voltage of the high-voltage power supply circuit. The output voltage of the low-voltage power supply circuit is output stably, and the output voltage of the high-voltage power supply circuit is output stably after a predetermined time has elapsed by switching the voltage feedback. As a result, a stable voltage supply in a steady state is enabled, and the circuit scale can be reduced.

According to a third aspect of the present invention, in the CRT power supply according to the first or second aspect, the voltage feedback means compares the output voltage with a preset value, and compares the output voltage with the predetermined value. Comparing means for outputting the result of the above as a comparison signal, insulation transmission means for transmitting the comparison signal to the primary side of the converter transformer, and converter control for outputting an on-off duty signal corresponding to the transmitted comparison signal And switching means to which the on-off duty signal is applied to turn on and off charging and discharging of electric energy to the primary side of the converter transformer and to turn on and off transmission of energy to the secondary side. Therefore, the CRT power supply device can be realized with a simple and small device.

According to the CRT power supply device of the fourth aspect, in the CRT power supply device of the third aspect, the switching means includes an N-type transistor serving as a power supply switch for an output voltage from the high-voltage power supply circuit. A high-voltage power supply circuit provided between a collector of the n-type transistor and a voltage output of a high-voltage power supply circuit, the P-type transistor being a power supply switch for the output voltage from the low-voltage power supply circuit; Since one or more Zener diodes having a Zener voltage equal to the voltage difference from the voltage power supply circuit are provided, the CRT power supply device can be realized with a simple and small device. .

According to the power supply device for a CRT according to claim 5, in the power supply device for a CRT according to claim 4, the base voltage Vb of the N-type transistor and the P-type transistor is
Vb ≧ Vlo with respect to the low-voltage power supply voltage Vlo in the steady state
And a voltage which is a resistance divided voltage by the divided resistors Rh and Rl provided between the high-voltage power supply voltage Vho in the steady state and the ground, and the switching control means includes a ground-side resistance of the divided resistors. An electric field capacitor provided in parallel with Rl is provided. After turning on the P-type transistor for a predetermined time, the P-type transistor is turned off, and at the same time as the P-type transistor is turned off, the N-type transistor is turned on. Therefore, the CRT power supply device can be realized with a simple and small device.

[Brief description of the drawings]

FIG. 1 is a diagram showing a main configuration of a CRT power supply device according to a first embodiment of the present invention.

FIG. 2 is a diagram showing a main configuration of a CRT power supply device according to a second embodiment of the present invention.

FIG. 3 is a diagram for explaining an effect of the CRT power supply device according to the second embodiment.

FIG. 4 is a diagram showing a configuration of a main part of a conventional CRT power supply device.

FIG. 5 is a diagram for explaining a start timing of a load circuit by a CRT power supply device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 11 Low voltage power supply circuit 111 Rectifier diode 112 Smoothing capacitor 12 High voltage power supply circuit 121 Rectifier diode 122 Smoothing capacitor 13 Feedback voltage comparison means 14 Switching means 141 Zener diode 15 Switching control means 16 Insulation transmission means 17 Converter control means 18 Switching means 19 Converter Transformer 211 P-type transistor 212 N-type transistor 213 Resistance Rh 214 Resistance Rl 215 Time constant capacitor 221 Zener diode 222 N-type transistor 223 Resistance Rb 161 Resistance Rr 41 High-voltage power supply circuit A 411 DC converter 412 Feedback circuit 42 High-voltage Power supply circuit B 421 DC converter 412 Feedback circuit 43 High-voltage power supply circuit C 431 DC converter 432 Feedback circuit 44 Low voltage power circuit D 441 DC converter 442 Feedback circuit 45 Low voltage power circuit E 451 DC converter 452 Feedback circuit

──────────────────────────────────────────────────の Continued on the front page (51) Int.Cl. ⁶ Identification code FI H04N 3/27 H04N 3/27 5/63 5/63 Z

Claims (5)

[Claims] 1. A CRT power supply device comprising a converter transformer having a low-voltage power supply circuit and a high-voltage power supply circuit on a secondary side, wherein the voltage feedback stabilizes the output voltage by the voltage feedback of the output voltage. And a switching means for switching which of the low voltage power supply circuit and the high voltage power supply circuit performs the voltage feedback. 2. The CRT power supply device according to claim 1, wherein the voltage feedback is performed on an output voltage of the low-voltage power supply circuit during a start-up period, and the high-voltage power supply circuit is controlled during a steady period. A power supply device for a CRT, further comprising switching control means for controlling the switching means so as to perform the voltage feedback on an output voltage. 3. The power supply device for a CRT according to claim 1, wherein the voltage feedback means compares the output voltage with a preset value, and outputs a result of the comparison as a comparison signal. Insulation transmission means for transmitting the comparison signal to the primary side of the converter transformer, converter control means for outputting an on-off duty signal in response to the transmitted comparison signal, and application of the on-off duty signal And a switching means for turning on and off the charging and discharging of electric energy to the primary side of the converter transformer and turning on and off the transmission of energy to the secondary side. Power supply. 4. The CRT power supply device according to claim 3, wherein said switching means includes an N-type transistor serving as a power supply switch for an output voltage from said high voltage power supply circuit, and an output voltage from said low voltage power supply circuit. A P-type transistor that is a power supply switch for the N-type transistor and an output voltage difference between the high-voltage power supply circuit and the low-voltage power supply circuit provided between the collector of the N-type transistor and the output voltage of the high-voltage power supply circuit. A power supply device for a CRT comprising at least one Zener diode having an equal Zener voltage. 5. The CRT power supply device according to claim 4, wherein the base voltage Vb of the N-type transistor and the P-type transistor is set to V with respect to a low-voltage power supply voltage Vlo in a normal state.
b ≧ Vlo, and the high-voltage power supply voltage Vh in the steady state
the switching control means includes an electric field capacitor provided in parallel with a ground-side resistor Rl of the divided resistors, A CR for turning on the P-type transistor for a predetermined time and then turning off the N-type transistor while turning off the P-type transistor at the same time as turning off the P-type transistor.
Power supply for T.