JPH08263151A - Control method for output voltage - Google Patents

Abstract

PURPOSE: To separate a power source part and a panel part and supply a voltage to the panel part by a power cable, and to prevent the voltage at the panel part from deviating from a permissible range by automatically switching the output voltage of the power source part according to the length of the power cable. CONSTITUTION: The primary voltage which is rectified and applied to the primary coil of a transformer 1 from the commercial power source is turned on and off by a switching circuit 3 which is connected to the primary coil in series by driving with pulses from an oscillation circuit 2, and the voltage induced across the secondary coil is rectified by a diode 4 and smoothed by a capacitor 5 to output a voltage Vs, which is applied to the panel part by the power cable. A switch S switches according to the length of the power cable to switch the voltage at the control terminal A of a control circuit 6, and controls control signal output. This control signal is applied to the oscillation circuit through a photocoupler 7 to vary an on-time ratio, the on-angle of the primary coil is controlled, and the voltage Vs is set to a value set by the length of the power cable.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply unit for supplying power to a panel unit for displaying on the basis of a video signal with a detachable cable. The output voltage is controlled in accordance with the length of the cable, and the panel unit is controlled. To those that supply a voltage within the allowable range.

[0002]

2. Description of the Related Art Plasma display panels (PDPs)
In the display device using, the panel portion is configured to be thin by taking advantage of the thinness of the depth of the display panel, and is separated from a bulky portion such as a power source portion, and as shown in FIG. There is a power supply cable 23 that is used to supply power from the power supply unit 21, and the panel unit 22 can be installed, for example, near a wall, or can be hung from the ceiling to widen the selection range of installation locations. . In this case, since the distance between the power supply unit 21 and the panel unit 22 varies depending on the installation conditions, a plurality of power supply cables 23 having different lengths are provided for convenience so as to meet the application. The power cable 23 includes a voltage Vs for discharging the PDP, a voltage Vdd for the logic circuit, and a panel section.
It is composed of a voltage Vr for controlling the discharge voltage Vs output from the power supply unit 21 from 22 and a ground wire. By the way, the PDP emits light by plasma discharge of the cell, and this discharge current reaches a maximum of several amperes in a few microseconds, for example, and since the current value is large, even a slight resistance of the electric wire of the power cable causes a voltage drop. Dropped, and the voltage that was normal at the output of the power supply was changed to PDP in the panel.
There is a case that it is out of the allowable voltage range of. To save the voltage drop, you can set the power supply voltage higher, but PD
Since the allowable voltage of P has an upper limit, in the case of a short power cable, the upper limit of the allowable voltage range may be exceeded. Eventually, the output voltage of the power supply unit must be adjusted according to the length of the power cable used. There is a problem of not becoming.

[0003]

In view of the above problems, the present invention has a function of detecting the length of the power cable used and a function of automatically switching the output voltage according to the length of the power cable. Is provided in the power supply unit so that the voltage supplied to the panel unit falls within an allowable range regardless of which power supply cable is used.

[0004]

In order to solve the above-mentioned problems, the present invention solves the above-mentioned problems by providing a power source section for outputting a DC voltage converted to a constant voltage by a constant voltage circuit and a voltage from the power source section detachably connected to the power source section. A power cable for supplying a load to the load and a panel section that operates at the voltage supplied by the power cable and displays based on a video signal, the length of the power cable at the connection section between the power section and the power cable. There is provided a power cable determination circuit for determining the output voltage, and the constant voltage circuit is controlled based on the signal from the power cable determination circuit to output a voltage set according to the length of the power cable. It is provided.

[0005]

With the above construction, in the output voltage control method according to the present invention, the difference between the lengths of the power supply cables connected to the power supply section is determined by the power supply section and the connection section of the power supply cable. The output voltage of the power supply is controlled to a preset voltage according to the length of the power cable, which is determined by the circuit.Therefore, the voltage supplied to the panel is acceptable regardless of which power cable is used. Allows normal operation of the panel without deviating from the voltage range.

[0006]

Embodiments of an output voltage control method according to the present invention will now be described in detail with reference to the drawings. FIG. 1 is a connection diagram of essential parts of an embodiment of a method of controlling an output voltage according to the present invention. In the figure, 1 is a switching transformer, 2 is an oscillation circuit, 3 is a switching circuit, 4 is a rectifying diode, 5
Is a smoothing capacitor, 6 is a control circuit that controls the oscillation circuit 2, R1 to R5 are voltage branch circuits that supply the control terminal voltage of the control circuit 6, and S is a switch that switches according to the type (length) of the power cable. , 7 are photocouplers for sending the output of the control circuit 6 to the oscillation circuit 2.

Next, the operation of the output voltage control method according to the present invention will be described. A switching circuit 3 is connected in series to the primary winding of the transformer 1, rectified by a commercial power source, and a primary voltage applied to the primary winding of the transformer 1 is driven by a signal from an oscillation circuit 2 to turn on / off, AC voltage is induced in the secondary winding of the transformer 1. The voltage of the secondary winding is rectified by the diode 4, smoothed by the capacitor 5, and the voltage Vs (voltage for discharging the PDP of the panel unit 22) is output. Oscillation circuit 2
The ON / OFF time ratio is controlled based on a signal applied from the control circuit 6 via the photocoupler 7, and the control circuit 6 outputs a control signal corresponding to the voltage of the control terminal A. That is, the control circuit 6 changes according to the fluctuation of the output voltage Vs.
The voltage of the control terminal A changes, the on-time ratio of the oscillation circuit 2 changes, the distribution angle of the primary winding of the switching circuit 3 and the transformer 1 changes, and the voltage Vs rectified by the diode 4 and smoothed by the capacitor 5 The operation of returning to the voltage before the fluctuation is performed, whereby the output voltage is always kept constant even if the voltage of the commercial power source fluctuates or the load fluctuates. In addition, R6 is a resistor for limiting the current of the photocoupler 6 so as not to exceed a specified value.

As described above, the voltage of the control terminal A of the control circuit 6 may be varied to vary the output voltage Vs. Therefore, one end of the resistor R1 is connected to the control terminal A of the control circuit 6, the other end of the resistor R1 is connected to the output voltage Vs, and one end of the resistor R2 is connected to the control terminal A and the resistor R2 is connected. Connect one end of each of resistor R3, resistor R4, and resistor R5 to the other end of R1, connect the other end of resistor R3 to ground, and connect the other end of resistor R4 and resistor R5 to the length of the power cable. It is connected to the ground via a switch S that switches depending on the difference. Due to these connections, when the switch S is switched to point a (no connection), the voltage applied to the control terminal A is the voltage Vs
When the switch S is at the point b, the resistor R4 is connected in parallel to the resistor R3, and the control terminal A is set to the switch S at the point a. When a switch S is at point c, a resistor R5 is connected in parallel to the resistor R3, and a voltage different from that when the switch S is switched to point a or point b at the control terminal A. Therefore, by appropriately setting the values of the resistors R1 to R5, the output voltage Vs can be controlled to a required voltage according to the switching of the switch S.

FIG. 2 is a conceptual view of the main part of the connecting portion of the power cable 23, in which (a) is a connector provided on the power source 21 side, (b)
(C) and (d) are connectors of the power cable 22 which are respectively inserted and connected to the connector (a), and have different lengths. In the figure, the connection terminals of the discharge voltage Vs, the logic circuit voltage Vdd, the Vs control voltage Vr, and the ground are omitted. This figure shows an example in which three connecting pieces and are provided. (B) is the power supply side connector (A)
1 is a non-connection piece, which corresponds to the case where the switch S in FIG. 1 is switched to the point a, and (c) is a short-circuit connection between the connection piece and the power supply side connector (a).
Is not connected and corresponds to the case where the switch S in FIG. 1 is switched to the point b (or the point c), and (d)
Is a connection piece of the power supply side connector (a) and is short-circuited, and is not connected. Switch S in FIG.
This is applicable when switching to the point (or point b). In addition,
In addition to the examples of (b) to (d), if the connecting pieces and are short-circuited, or if the connecting pieces and are short-circuited, by providing three connecting pieces, the above (b) to ( In addition to d), it is possible to discriminate five types of lengths.

FIG. 3 shows the connection portion (b) of the power cable 23,
This is an example in which a protrusion is provided on the outer circumference of (c) and (d), and a switch which is operated by being pushed by the protrusion of the power cable 23 is provided at the connection part (a) on the power source 21 side. That is, a slide switch 11 that slides in the insertion / removal direction of the connector is provided outside the connector on the side of the power supply unit 21, the knob 12 is biased by the spring 13 in the direction of arrow 14 (outward), and the power cable 23 Upon mounting, the knob 12 is pushed by the projection 15 provided on the outer peripheral portion of the power cable. The position of the protrusion 15 is set for each length of the power cable 23, and the length of the power cable is determined by whether the contact on the sliding side of the switch 11 is connected to the fixed contact a, b or c. . It should be noted that, instead of the protrusion 15, notches having different depths in the arrow direction depending on the length of the power cable may be formed on the outer peripheral portion of the power cable 23, and the knob 12 may be pushed by this notch to switch the switch 11. .

[0011]

As described above, according to the output voltage control method of the present invention, the power supply circuit is automatically controlled according to the length of the attached power supply cable, and the output voltage is switched to the panel. Since the voltage supplied to the power supply does not deviate from the allowable range, the power supply voltage need not be adjusted due to the difference in the length of the power supply cable.

[Brief description of drawings]

FIG. 1 is a connection diagram of essential parts of an embodiment of a method of controlling an output voltage according to the present invention.

FIG. 2 is a conceptual diagram of a power cable connecting portion of the output voltage control method according to the present invention.

FIG. 3 is a conceptual diagram of a power cable connecting portion of the output voltage control method according to the present invention.

FIG. 4 is a conceptual diagram illustrating a relationship between a power supply unit, a panel unit, and a power supply cable.

[Explanation of symbols]

 1 Switching transformer 2 Oscillation circuit 3 Switching circuit 4 Rectifying diode 5 Smoothing capacitor 6 Control circuit 7 Photocoupler S switch R1, R2, R3, R4, R5 Resistor, connector connection piece 11 Switch 15 Protrusion

Claims (7)

[Claims] 1. A power supply unit for outputting a DC voltage converted to a constant voltage by a constant voltage circuit, a power supply cable detachably connected to the power supply unit for supplying a voltage from the power supply unit to a load, and a power supply cable for supplying the voltage. A panel section that operates on voltage and displays based on a video signal, a power cable determination circuit that determines the length of the power cable is provided at the connection between the power source section and the power cable, and the power cable determination circuit A method of controlling an output voltage, wherein the constant voltage circuit is controlled on the basis of the signal to output a voltage set for each length of the power cable. 2. The power supply cable discrimination circuit is provided with a plurality of pairs of connection pieces, which are connected to each other when the power supply cable is attached, on both the power supply section side and the power supply cable side, and the power supply is provided between the connection pieces on the power supply cable side. A resistor that is short-circuited or disconnected depending on the length of the cable, and that each connection piece on the power supply side has a connection point that corresponds to the number of connection pieces and that the resistance value differs between each connection point. 2. The output voltage control method according to claim 1, wherein the length of the power supply cable is determined based on the resistance value of the resistor circuit when the power supply cable is attached. 3. At least three pairs of the connection pieces are provided on both the power supply section side and the power supply cable side, and five types of power supply cable lengths are obtained by a combination of short-circuit connection / non-connection between the connection pieces on the power supply cable side. 3. The method for controlling an output voltage according to claim 2, wherein the difference in height is determined. 4. The output voltage control method according to claim 2, wherein each of the connection pieces is provided separately from a connection for a voltage supplied from the power supply section to the panel section. 5. The power supply cable discrimination circuit is provided with protrusions or the like at different positions according to the length of the power supply cable in the mounting part of the power supply cable to the power supply part, and the power supply cable mounting part on the power supply part side is provided with each power supply. The output voltage according to claim 1, wherein a switch that is switched by mounting the power cable is provided at a position corresponding to the projection of the cable, and the length of the power cable is determined based on the switching of the switch. Control method. 6. The constant voltage circuit is composed of a distribution angle control type constant voltage circuit, the distribution angle is controlled based on a signal from the power cable determination circuit, and a voltage set for each length of the power cable is output. The method of controlling the output voltage according to claim 1, claim 2, claim 3, claim 4, or claim 5 configured to do so. 7. The constant voltage circuit drives a switching circuit on / off by a signal from an oscillating circuit, switches a rectified primary voltage from a commercial power source, applies the rectified primary voltage to an insulating transformer primary winding, and It is configured to rectify the voltage generated in the winding and output a DC voltage, and controls the oscillation circuit via a photo coupler based on the signal from the power cable determination circuit, and the on / off time of the switching circuit. The output voltage control method according to claim 1, claim 2, claim 3, claim 4, or claim 5, wherein a voltage set for each length of the power supply cable is output.