JP3822480B2 - Power supply device and display device having the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a power supply device provided in a display device, for example, and the display device.
[0002]
[Prior art]
For example, in a CRT display device, an AC power supply voltage (for example, AC 100 V), which is a commercial power supply voltage, is supplied to display on the display screen. In this CRT display device, an operation unit of a power switch for turning on and off the CRT display device is usually arranged on the surface of the front panel on which the display screen is arranged.
[0003]
FIG. 3 is a circuit diagram showing an example of a conventional power supply device in a CRT display device. According to this circuit diagram, after the noise component is removed by the noise filter circuit 2, the input voltage is full-wave rectified and smoothed by the diode bridge circuit B and the smoothing capacitor C1. A power switch SW arranged on the front panel is interposed in series in the power line L for the input voltage. When the power switch SW is turned on, the power control IC 6 is activated. By this activation, the field effect transistor FET is controlled to be turned on and off to perform a switching operation, and the output of the diode bridge circuit B is supplied to the primary side of the power transformer T. As a result, a predetermined voltage is applied to each of the terminals V1 to V5.
[0004]
FIG. 4 is a circuit diagram showing another example of a conventional power supply device in a CRT display device. According to this circuit diagram, the power switch SW has a two-pole contact, one contact is connected in series to the power line L after the resistor R1, and the other contact is the tertiary of the power transformer T. Connected to the side output. In this circuit diagram, when the power switch SW is turned on, the input voltage is applied directly and at once to the electrolytic capacitor C2, the power control IC 6 or the tertiary output circuit of the power transformer T. .
[0005]
[Problems to be solved by the invention]
According to the circuits shown in FIGS. 3 and 4, for example, an AC power supply voltage is directly applied to the power switch SW, so that it is necessary to use a power switch having a high breakdown voltage and a high breakdown voltage. Actually, for example, in a 17-inch CRT display device, a power switch with a rating of AC125V, 5A is used. For this reason, the power switch SW inevitably has a large size and volume, and such a power switch SW is generally expensive, which increases the component cost. Further, when the operation unit of the power switch SW is arranged so as to be exposed from the front panel of the CRT display device, a certain amount of arrangement space is required for the power switch on the front panel and in the vicinity of the back surface of the front panel. Therefore, it has been a factor that hinders downsizing of the surface panel.
[0006]
This invention makes it the subject to provide the power supply device which can achieve size reduction of a front panel and cost reduction of components.
[0007]
DISCLOSURE OF THE INVENTION
In order to solve the above problems, the present invention takes the following technical means.
[0008]
A power supply device provided by the first aspect of the present invention includes a power transformer circuit, a rectifying and smoothing circuit that rectifies and smoothes a commercial power supply voltage to convert it into a DC power supply voltage, and supplies the DC power supply voltage to the primary winding of the power transformer circuit. A circuit, a switching element that interrupts the DC power supply voltage supplied to the primary winding of the power transformer circuit, a control circuit that controls the intermittent operation of the switching element, and supply of drive voltage to the control circuit or A power supply device comprising a power switch for stopping, comprising: a constant voltage circuit that generates a constant voltage having a predetermined voltage value lower than the voltage value from the commercial power supply voltage as the drive voltage, The power switch is a switch that can be turned on and off manually, and is provided between the constant voltage circuit and the power input terminal of the control circuit. It is characterized in that.
[0009]
According to a preferred embodiment, the constant voltage circuit includes a Zener diode which the commercial power supply voltage is input via a resistor, and a Zener diode and capacitor connected in parallel.
[0011]
According to the present invention, when the commercial power source voltage is input, the constant voltage circuit including a zener diode, a constant voltage having a predetermined voltage value lower than the Re their is generated. Then, the constant voltage, by the power switch that is provided between the power input end of the output terminal and control circuit of the constant voltage circuit is turned on by a manual operation, is input to the power input terminal of the control circuit. Therefore, it is not necessary to use a large and expensive power switch having a high withstand voltage and high withstand current as in the prior art, and use a small and relatively inexpensive one with withstand voltage and withstand current according to a constant voltage. be able to. Therefore, it is possible to reduce the size of the component and reduce the cost of the component.
[0012]
The display device provided by the second aspect of the present invention includes the power supply device provided by the first aspect, and the power switch is disposed on the front panel so as to be manually operable. Yes.
[0013]
According to the present invention, when the power supply device is applied to, for example, a CRT display device, a relatively small power switch is used to reduce the space for arranging the power switch on the front panel and in the vicinity of the back surface of the front panel. Can do. Therefore, the surface area of the front panel can be made as small as possible, and the display device can be downsized.
[0014]
Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.
[0015]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, preferred embodiments of the present invention will be specifically described with reference to the accompanying drawings.
[0016]
FIG. 1 is a perspective view of a CRT display device provided with a power supply device according to the present invention, and FIG. 2 is a circuit diagram of the power supply device. The CRT display device A is used by being connected to a personal computer or the like. A display screen is disposed on almost the entire surface of the front panel A1, and a power switch SW is disposed below the front panel A1.
[0017]
As shown in FIG. 2, the power supply device 1 includes a noise filter circuit 2, a fuse F, a rectifying / smoothing circuit 4, a constant voltage circuit 5, a power switch SW, a power control IC 6 as a control circuit, a switching circuit 7, and a power transformer T. A snubber circuit 8, a secondary winding output circuit 9, and a tertiary winding output circuit 10.
[0018]
The noise filter circuit 2 is a circuit that removes a noise component included in an AC power supply voltage (for example, AC100V) as a commercial power supply voltage that is input to the power supply device 1, and a plurality of coils L and a plurality of capacitors C are combined. Being done.
[0019]
The fuse F is blown when an overcurrent flows to prevent subsequent influence on the circuit.
[0020]
The rectifying / smoothing circuit 4 is for full-wave rectification and smoothing of the AC power supply voltage from which noise components have been removed by the noise filter circuit 2, and includes four diodes D1 constituting the bridge circuit B, and a bridge circuit. And a smoothing capacitor C1 connected between the output terminal of B and the ground.
[0021]
The constant voltage circuit 5 is for holding the AC power supply voltage at a predetermined voltage value. The resistor R1 has one end connected to the power supply line L of the AC power supply voltage, and the cathode is connected to the other end of the resistor R1. The Zener diode ZD whose anode side is connected to the ground, and the electrolytic capacitor C2 whose positive electrode is connected to the cathode side of the Zener diode ZD and whose negative electrode is connected to the ground. The resistor R1 is set to 15 kΩ, for example, and the electrolytic capacitor C2 is set to 220 μF, for example.
[0022]
The power switch SW turns on and off the power supply voltage supplied to the power supply terminal Vcc of the power supply control IC 6, one end of which is connected to the cathode side of the Zener diode ZD of the constant voltage circuit 5 and the other end is connected. The power supply control IC 6 is connected to the power supply terminal Vcc.
[0023]
The power supply control IC 6 operates by the power supply voltage supplied from the power supply terminal Vcc, and controls the switching circuit 7 by outputting a pulse signal having a predetermined duty ratio from the output terminal Out.
[0024]
The switching circuit 7 supplies a pulse signal to the primary winding of the power transformer T. The switching circuit 7 is connected in parallel to the resistor R2 having one end connected to the output terminal Out of the power control IC 6 and the resistor R2. A field effect transistor FET as a switching element having a gate terminal connected to the other end of the resistor R2, and a resistor R3 having one end connected to the source terminal of the field effect transistor FET and the other end connected to the ground. Become. The field effect transistor FET is a so-called n-channel depletion type (normally on type), and is turned on and off by a pulse signal from the power supply control IC 6.
[0025]
The power transformer T converts the DC voltage that has been full-wave rectified and smoothed by the rectifying and smoothing circuit 4 into a predetermined output voltage for the secondary winding output circuit 9 and the tertiary winding output circuit 10. is there. For example, five different voltages are output from the secondary winding side of the power transformer T.
[0026]
The snubber circuit 8 is for consuming magnetic energy generated in the power supply transformer T when the field effect transistor FET in the switching circuit 7 is turned on and off. The snubber circuit 8 has an anode connected to the drain terminal of the field effect transistor FET in the switching circuit 7. A switching diode D3 connected to one side, a capacitor C3 having one end connected to the cathode side of the switching diode D3, and a resistor R4 connected in parallel to the capacitor C3. The other end of the capacitor C3 is connected to the output terminal of the bridge circuit B and is also connected to the primary side input terminal I1 of the power transformer T. The primary side input terminal I2 of the power transformer T is connected to the snubber circuit 8. The anode side of the switching diode D3 is connected.
[0027]
The secondary winding output circuit 9 stably outputs the above five different voltages. From the terminal V1, for example, 9V for heater operation and microcomputer operation, and for the vertical deflection circuit from the terminal V2. 15V is -13V on the opposite side of the 9V output and 15V output from the terminal V3, 170V for the horizontal deflection circuit from the terminal V4, and 80V for the high voltage 25kV output and the video circuit from the terminal V5. Each voltage is output.
[0028]
Specifically, the secondary side output terminal O1 of the secondary winding output circuit 9 is connected to the anode side of the rectifier diode D4, and the cathode side of the rectifier diode D4 is connected to the positive side of the smoothing capacitor C4 and the terminal V1. Is connected. Similarly, the anode side of the rectifier diode D5 is connected to the secondary output terminal O2, and the cathode side of the smoothing capacitor C5 and the terminal V2 are connected to the cathode side of the rectifier diode D5. The secondary output terminal O3 is connected to the cathode side of the rectifier diode D6, and the anode side of the rectifier diode D6 is connected to the negative side of the smoothing capacitor C6 and the terminal V3. The secondary output terminal O4 is connected to the anode side of the rectifier diode D7, and the cathode side of the rectifier diode D7 is connected to the positive side of the smoothing capacitor C7 and the terminal V4. Further, the anode side of the rectifier diode D8 is connected to the secondary side output terminal O5, and the positive electrode side of the smoothing capacitor C8 and the terminal V5 are connected to the cathode side of the rectifier diode D8. The secondary output terminals O6 to O8 are connected to the frame ground.
[0029]
The tertiary winding output circuit 10 is for continuously supplying a stable power supply voltage to the power supply terminal Vcc of the power supply control IC 6, and the anode side is connected to the tertiary output terminal O9 of the power supply transformer T. The rectifier diode D9, one end connected to the cathode side of the rectifier diode D9, the other end connected to the cathode side of the Zener diode ZD in the constant voltage circuit 5, the positive side is the cathode side of the rectifier diode D9, and the negative side is the power source And a smoothing capacitor C9 connected to the tertiary output terminal O10 of the transformer T.
[0030]
Next, the operation in the above circuit configuration will be described. First, the case where the power switch SW is off will be described. When an input voltage of AC voltage is input to the power supply device 1, noise components are removed from the input voltage by the noise filter circuit 2, and the rectifying and smoothing circuit 4 Full wave rectification and smoothing.
[0031]
The input voltage from which the noise component has been removed by the noise filter circuit 2 is supplied to the constant voltage circuit 5 through the power supply line L. In the constant voltage circuit 5, since the power switch SW is turned off, the input voltage gradually increases due to the action of the electrolytic capacitor C2, but the upper limit is held by the Zener diode ZD so as to be a predetermined constant voltage, for example, 24V. The
[0032]
Further, since the power supply control IC 6 is not operating due to the power switch SW being turned off, the field effect transistor FET is in the off state, that is, the output of the bridge circuit B is the primary power transformer T. Not input to the winding side.
[0033]
Next, the operation when the power switch SW is turned on will be described. When the power switch SW is turned on, the voltage held in the constant voltage circuit 5 is supplied to the power terminal Vcc of the power control IC 6 and the power control IC 6 operates. As a result, a pulse signal is output from the output terminal Out of the power supply control IC 6 with a predetermined duty ratio. Accordingly, the field effect transistor FET is turned on and off to perform a switching operation, whereby the power transformer T is supplied with the output of the bridge circuit B on the primary winding side.
[0034]
Specifically, during a period in which the field effect transistor FET is on, the magnetic flux of the power transformer T increases and magnetic energy is stored in the power transformer T. In this case, the current from the rectifying / smoothing circuit 4 passes through the primary side of the power supply transformer T and flows through the field effect transistor FET. Further, when the field effect transistor FET is off, the magnetic energy is released, and the magnetic flux is returned to the residual magnetic flux. In this case, current flows through the primary winding of the power transformer T, the switching diode D3, and the resistor R4, and the magnetic energy is consumed as heat by the resistor R4.
[0035]
In each secondary winding output circuit 9, the output is smoothed by the smoothing capacitors C4 to C8, and a predetermined voltage is supplied to each circuit (not shown) via the terminals V1 to V5. That is, the power switch SW turns on the voltage supplied to the power control IC 6 so that the power control IC 6 controls the primary winding side voltage of the power transformer T. Functions as a switch to set
[0036]
Thus, according to the above configuration and operation, when an input voltage of AC voltage is input, the input voltage is held at a predetermined voltage value lower than that by the constant voltage circuit 5 including the Zener diode ZD. The held predetermined voltage value is supplied to the power supply terminal Vcc of the power supply control IC 6 when the power switch SW interposed between the constant voltage circuit 5 and the power supply terminal Vcc of the power supply control IC 6 is turned on. Is done.
[0037]
Therefore, since an input voltage such as AC100V is converted into 24V and applied to the power switch SW, for example, it is not necessary to use a large and expensive switch having a high withstand voltage and a high withstand current as in the prior art. A small and inexpensive one having a withstand voltage and a current resistance according to the voltage value can be used. For this reason, it is possible to reduce the cost of components and to reduce the size of the components.
[0038]
Further, in the CRT display device A to which the power supply device 1 is applied, the relatively small power switch SW is used, thereby reducing the arrangement space of the power switch SW on the front panel A1 and in the vicinity of the back side of the front panel A1. be able to. Therefore, the surface area of the front panel A1 can be reduced as much as possible, and the CRT display device A can be downsized.
[0039]
Of course, the scope of the present invention is not limited to the embodiment described above. For example, the power supply device 1 described above is not limited to being applied to the CRT display device A, and can be applied to any kind of electronic device as long as it is a device to which a power supply voltage is supplied.
[0040]
【The invention's effect】
As described above, according to the present invention, the power supply can be turned on / off manually by a manual operation between the constant voltage circuit that generates a predetermined constant voltage lower than the commercial power supply voltage and the power input terminal of the control circuit. Since the power switch to be switched is provided , it is not necessary to use a large and expensive power switch having a high withstand voltage and a high withstand current as in the prior art, but with a withstand voltage and withstand current according to a predetermined constant voltage. A relatively small and inexpensive one can be used, so that the size of the component can be reduced and the cost of the component can be reduced. Therefore, when this power supply device is applied to, for example, a CRT display device, the space for disposing the power switch on the front panel can be reduced by using a small power switch, so that the front panel of the display device can be reduced, and consequently The display device can be downsized.
[Brief description of the drawings]
FIG. 1 is a perspective view of a CRT display device including a power supply device according to the present invention.
FIG. 2 is a circuit diagram of a power supply device.
FIG. 3 is a circuit diagram of a conventional power supply device.
FIG. 4 is a circuit diagram of another conventional power supply device.
[Explanation of symbols]
1 Power supply device 5 Constant voltage circuit 6 Power supply control IC
7 Switching circuit A CRT display device SW Power switch ZD Zener diode

Claims (3)

A power transformer circuit;
A rectifying / smoothing circuit for rectifying and smoothing a commercial power supply voltage to convert it into a DC power supply voltage and supplying it to the primary winding of the power transformer circuit;
A switching element for intermittently connecting the DC power supply voltage supplied to the primary winding of the power transformer circuit;
A control circuit for controlling the intermittent operation of the switching element;
A power switch for supplying or stopping driving voltage to the control circuit;
A power supply device comprising:
A constant voltage circuit for generating a constant voltage having a predetermined voltage value lower than the voltage value from the commercial power supply voltage as the drive voltage;
The power supply device comprises a switch for switching on / off of the power supply by manual operation, and is provided between the constant voltage circuit and a power supply input terminal of the control circuit . The constant voltage circuit includes a Zener diode which the commercial power supply voltage is input via a resistor, and a Zener diode connected in parallel with a capacitor, the power supply device according to claim 1. A power supply device according to claim 1 or 2, characterized in that the power switch is manually operably disposed on the front panel, display the display device.

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