JPH08139588A - Gate control circuit - Google Patents

Abstract

PURPOSE: To widen the range of the applicable power supply voltage of a gate control circuit by setting the breakdown voltage of a Zener diode higher than the gate threshold value of a gate control element and lower than the gate withstand voltage value. CONSTITUTION: A current circuit 30 is opened and closed accompanying the ON/OFF of a control transistor 10 and transmits the specification of ON/OFF operations by low voltage signals Sd to the gate control element 1. The transistor 10 is turned ON/OFF corresponding to the logical state of the high/low of the signals Sd and a current made to flow to the current circuit 30 is started and stopped corresponding to it. Also, since a gate control voltage to the gate control element 1 which is the breakdown voltage of the Zener diode 20 is stopped corresponding to it, the gate element 1 is ON/OFF operated as specified by the signals Sd. As a result, since the gate control voltage for ON operating the element 1 is prepared by the breakdown voltage of the diode 20, it is fixedly maintained at all times regardless of the power supply voltage and use in common to the voltage of a wide range is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a display driving circuit for operating a plasma display panel, an electroluminescence display panel, a fluorescent display panel or the like according to video data under a power supply voltage of tens to hundreds of volts. In 5
MOS connected to the high voltage side by a low voltage signal of about V
The present invention relates to a gate control circuit suitable for controlling on / off of a gate control element such as a transistor.

[0002]

2. Description of the Related Art In a drive circuit for a display panel as described above, a power supply voltage for a load of, for example, 20 to 200 V is usually applied to its output circuit of an inverter type, so that a transistor connected to the power supply voltage side is used as a video data source. In order to perform on / off operation with a low voltage signal of 5V, a so-called level shift circuit must be interposed between the low voltage signal and the high voltage side transistor. FIG. 5 shows a conventional example of an output circuit incorporating such a level shift circuit.

The right side of FIG. 5 is an output CMOS inverter, which has a p-channel transistor 1 and an n-channel transistor 2 between a power supply voltage point V and a ground point E.
The output voltage Vo for driving the load is taken out from the interconnection point between the two transistors 1 and 2 by alternately turning them on and off as usual. For example, a control transistor 3 is provided on the ground point E side in order to turn on / off the transistor 1 on the high voltage side by a low voltage signal Sd which is video data, and this is connected to the power source voltage point V via two resistors 3a and 3b. Connecting. A complementary signal of the low voltage signal Sd is given to the output transistor 2 on the side of the ground point E, and the low voltage signal Sd obtained by inverting the signal is given to the control transistor 3 by the inverter 4 composed of the complementary transistors 4a and 4b.

Control transistor 3 and its series resistors 3a and 3b
Is a level shift circuit for transmitting the low voltage signal Sd to the transistor 1 on the high voltage side. Since the transistor 1 is turned on by operating the gate by the voltage drop generated in the resistor 3a only when the control transistor 3 is turned on, Voltage signal
The same on / off operation as that of the control transistor 3 according to the high / low of Sd is performed. Of course, the transistor 2 on the ground side which receives the complementary signal of the low voltage signal Sd performs the on / off operation opposite to this.

[0005]

As described above, in the conventional level shift circuit, the power supply voltage V is divided by the resistors 3a and 3b to generate the control voltage for the gate of the transistor 1 on the high voltage side. Must be transistor 1
Since there is a restriction that it must be set higher than the gate operation threshold value of and lower than the gate breakdown voltage, an output circuit incorporating this level shift circuit as a gate control circuit operates at a power supply voltage V suitable for various applications. There is a problem that cannot be made.

For example, in the output circuit for driving the display panel, the power supply voltage V within the range of 20 to 200 V is selected according to the type of the display panel.
Is used, and the gate of the transistor 1 on the high voltage side usually has an operating threshold value of about 2V and a withstand voltage of about 20V. Now, if the control voltage for the gate of the transistor 1 is made by dividing the power supply voltage V into 1/10 by the resistors 3a and 3b, the value becomes 2V when the power supply voltage V is 20V and 20V when the power supply voltage V is 200V. Therefore, the above-mentioned operating threshold and withstand voltage restrictions are met for the time being, but in practice, in order to ensure the operation of the transistor 1, this gate control voltage is 4 V or more, which is twice the operating threshold. Therefore, in order to guarantee the safety of the gate, it is necessary to set it to 10 V or less, which is half the withstand voltage.

Therefore, the range of the power supply voltage V to which such an output circuit can be applied is actually 40 to 100V. Of course, the applicable voltage range can be shifted to the high voltage side or the low voltage side by changing the setting of the voltage division ratio of the power supply voltage V by the resistors 3a and 3b described above. As long as there is a restriction of 4 V or more to 10 V or less, the ratio of the lower limit value to the upper limit value of the voltage range can be easily understood, no matter how the division ratio by the resistors 3a and 3b is set, The ratio does not exceed 2.5 times. Although the restriction can be relaxed by lowering the operation threshold value of the gate of the transistor 1 for the output circuit and increasing the withstand voltage value, since both characteristics are in a contradictory relationship with each other as is well known, this solution is generally adopted. Have difficulty.

An object of the present invention is to solve the above problems of the prior art and to provide a gate control circuit applicable even when the power supply voltage varies over a wide range.

[0009]

According to the present invention, the above object is to control the gate control element connected to the high voltage side by the low voltage signal so that the gate control element is connected to the low voltage side to receive the low voltage signal. ON / OFF operation of the control transistor by connecting the gate of the gate control element and the control transistor to each other, and the Zener diode connected in the reverse direction between the gate of the gate control element and the high-voltage power supply point It is achieved by forming a gate control circuit from a current path that opens and closes according to the above, and setting the breakdown voltage of the Zener diode higher than the gate operation threshold value of the gate control element and lower than its gate breakdown voltage value.

The gate control element is, for example, a MOS type or DMOS type transistor. The simplest way is to insert a current setting resistor into the current path of the above configuration, but the current consumption tends to vary considerably depending on the power supply voltage. For this reason, it is desirable to insert a constant current element or constant current circuit in the current path. In particular, it is necessary to use a depletion type field effect transistor as the constant current element to operate in the saturation current region because the consumption current is the power supply voltage. It is advantageous to make the value almost constant regardless of the above. In order to make this current consumption more accurate, it is better to use a driven transistor of a current mirror circuit whose operation is stopped in response to a low voltage signal as the control transistor. In this case, the control transistor is the gate of the gate control element. To form a current path.

The breakdown voltage of the Zener diode is set in accordance with the operation threshold value and breakdown voltage value of the gate of the gate control element as described above, but it is usually set within the range of 4 to 10 V, particularly 7 to It is preferable to set it within the range of 10V. When incorporating such a Zener diode into an integrated circuit device, a diode layer having a high impurity concentration for it is formed by simultaneous diffusion with a source layer of the same conductivity type of a MOS type or DMOS type transistor as a gate control element. This is advantageous in simplifying the wafer process as much as possible.

[0012]

According to the present invention, the gate control voltage for the gate control element on the power supply voltage side is generated by resistance division as in the conventional case.
Paying attention to the point that the applicable voltage range of the gate control circuit cannot be escaped from the restriction due to the operation threshold value and withstand voltage value of the gate of the controlled element as described above, no matter how the division ratio is set. As described in the configuration, a Zener diode whose Zener breakdown voltage is set higher than the operating threshold value of the gate of the controlled element and lower than the withstand voltage value is connected in the reverse direction between this gate and the high-voltage power supply point, and the constant voltage is maintained. The breakdown voltage of is generated as the ON control voltage for the controlled element,
Moreover, by connecting the gate of the controlled element to the control transistor that operates on / off by receiving a low voltage signal through the current path, the gate control voltage for turning on the controlled element is always constant regardless of the power supply voltage, and The gate control circuit can be easily applied to a wide range of power supply voltages.

[0013]

Embodiments of the present invention will be described with reference to the drawings. An example in which a current setting resistor is inserted in the current path is shown in FIG.
FIG. 2 shows an embodiment in which a constant current element is inserted in the current path, and FIG. 3 shows an embodiment in which the driven side transistor of the current mirror circuit is used as the control transistor. Since the parts corresponding to those in FIG. 5 described before these figures are denoted by the same reference numerals, the description of the overlapping parts will be appropriately omitted. FIG. 4 shows a structural example in which the gate control circuit according to the present invention is incorporated in an integrated circuit device.

The inverter type output circuit shown on the right side of FIG. 1 is, for example, for driving each pixel of the display panel, and is a p-channel type M which is the gate control element 1 on the high voltage power source V side.
The OS transistor and the DMOS transistor, for example, receive the low voltage signal Sd of 5V which is the video data, and the n-channel type MOS or DMOS transistor which is the gate control element 2 on the ground potential point E side alternately by the complementary signal of the low voltage signal Sd It is controlled on and off. In order to control the gate control element 1 on the high voltage side, an n-channel type control transistor 10 is connected to the ground point E on the low voltage side as in the conventional case, and the high / low logic of the low voltage signal Sd received by the gate is applied. It turns on and off depending on the state.

In the present invention, the Zener diode 20 is connected between the gate of the high-voltage side gate control transistor 1 and the high-voltage power supply point V in the direction in which the reverse bias is applied, and the current path is
The breakdown voltage of the Zener diode 20 is set higher than the operation threshold value of the gate of the gate control element 1 and lower than the withstand voltage value while being coupled to the control transistor 10 via 30. When the operation threshold value is 2V and the withstand voltage value is 20V, the breakdown voltage is preferably set to 4 to 10V, more preferably 7 to 10V. The current path 30 is opened / closed when the control transistor 10 is turned on / off to transmit the designation of the on / off operation by the low voltage signal Sd to the gate control element 1. In this embodiment, the current flowing when the control transistor 10 is turned on is set to this. To do this, a current setting resistor 31 of several hundred kΩ is inserted.

In the gate control circuit 40 of the present invention constructed as shown in FIG. 1, the control transistor 10 is turned on / off according to the high / low logic state of the low voltage signal Sd, and accordingly the current path is changed.
Since the current flowing in 30 is stopped and the gate control voltage for the gate control device 10 which is the breakdown voltage of the Zener diode 20 is stopped accordingly, the gate control device 1 is designated by the low voltage signal Sd as in the conventional case. Operates as it is turned on and off.

However, in the circuit of the present invention, the gate control element 1
Gate control voltage to turn on the zener diode
Since it is made by the breakdown voltage of 20, it can be kept constant regardless of the power supply voltage V. Therefore, the output circuit incorporating the gate control circuit 40 of the present invention can be commonly applied to a very wide range of the power supply voltage V, for example, a voltage range of 20 to 200 V suitable for driving almost all kinds of display panels including liquid crystal type. .

As shown in FIG. 1, a resistor 21 of several tens of kΩ is connected in parallel to the Zener diode 20, and the gate of the gate control element 1 is pulled up to the power supply potential V during the non-breakdown state to ensure the off operation. Is desirable. Further, as in the conventional case, the power supply voltage V is applied to the control transistor 10 when it is off, so that the control transistor 10 has a withstand voltage structure suitable for it. Further, in the embodiment of FIG. 1, when the control transistor 10 is turned on, the power supply voltage V and the Zener diode are applied to the current setting resistor 31.
Since a voltage equal to the breakdown voltage difference of 20 is applied, the consumption current flowing therethrough changes according to the power supply voltage V.

In the next embodiment shown in FIG. 2, a constant current element 31 is inserted in the current path 30 so that the above-mentioned consumed current does not change with the power supply voltage V. In the illustrated example, a depletion type p-channel MOS transistor is used as the constant current element 31, and its gate is connected to the drain to be used in the saturation current region. As is well known, the depletion type transistor has temperature dependence, but has considerably high constant current performance when used in the saturation current region. The part of the embodiment shown in FIG. 2 excluding the constant current element 31 is the same as that shown in FIG.

In the embodiment shown in FIG. 3, the control transistor
By using a driven transistor of the current mirror circuit which starts and stops the operation according to the low voltage signal as 10, the current consumption is kept constant regardless of the gate voltage V. A reference current is applied to the reference transistor 11 of the current mirror circuit via a resistor 12 that receives a stabilized constant power supply voltage Vd of 5 V, for example, and a transistor 13 connected in parallel to the reference transistor 11 responds to the low voltage signal Sd. The current mirror circuit is turned on and off to start and stop the current mirror circuit, and the same constant current as the reference current is caused to flow in the current path 30 by the control transistor 10 which is a driven transistor. It is preferable to use a resistor of several tens of kΩ for the resistor 12 and set the reference current, that is, the current flowing through the current path 30 to about 100 μA. In the embodiment of FIG. 3 as well, the other parts are the same as those of FIG.

Finally, with reference to FIG. 4, a structural example of main circuit elements suitable for incorporating the gate control circuit 40 of the present invention into an integrated circuit device will be described. Zener diode at the top of Fig. 4
20 and a p-channel DMOS transistor as the gate control element 1, an n-channel DMOS transistor as the gate control element 2 in the middle stage, a low breakdown voltage n-channel transistor 11 and a p-channel depletion type as the constant current element 32 in the lower stage. The cross-sectional structure of a transistor is shown respectively. In addition, the terminals derived from these circuit elements are shown in FIG.
The reference numerals corresponding to FIG. 3 are attached.

On the wafer of the illustrated integrated circuit device 50, as is customary, an n-type buried layer 52 is diffused on the surface of a p-type semiconductor substrate 51 and then an n-type epitaxial layer 53 is grown. Using a diffused p-type junction separation layer 54 in the range,
The important part of the surface is covered with a thick oxide film 55 for the element isolation film or the field oxide film by the L0COS method or the like. The Zener diode 20 shown on the left side of the upper part of the figure has a structure in which the n-type wall layer 56 is deeply diffused from the surface of the epitaxial layer 53 to reach the buried layer 52, and then the p-type diode layers 64 and n are formed.
Type diode layer 67 is diffused as shown in the figure with a high impurity concentration of 10 ²⁰ atoms / cm ³ or more on the surface portion, and the current at the time of Zener breakdown is from the n type diode layer 67 and the epitaxial layer 53 to the p type. Of the diode layer 64.

The p-channel DMOS gate control element 1 on the right side is provided with a gate oxide film 58 and a gate 59 on the surface of an epitaxial layer 53, and then has a p-type drain layer 61 and an n-type drain layer 61 sandwiching it from both sides. Of the channel diffusion layer 62, and the p-type source layer 63 is diffused on the surface of the latter at a high impurity concentration. It is advantageous to make the p-type diode layer 64 of the Zener diode 20 by simultaneous diffusion with the source layer 63 in order to simplify the wafer process as much as possible.

The n-channel DMOS shown in the middle part of FIG.
In the gate control element 2 of FIG. 1, first, the n-type drain connection layer 56 is deeply diffused from the surface of the epitaxial layer 53 to reach the buried layer 52, and the gate 59 is provided, and then the p-type channel diffusion layer 60 is formed. The n-type source layer inside
66 is diffused with a high impurity concentration. This n-channel type D
Also for the MOS, it is advantageous to simplify the wafer process that the n-type diode layer 67 of the Zener diode 20 is formed by simultaneous diffusion with the n-type source layer 66.

The n-channel transistor 11 shown on the left side of the lower part of FIG.
After the p-type well 57 is diffused from the surface of the gate and the gate 59 is provided, the n-type source layer 68 is diffused on both sides thereof with a high impurity concentration. In the p-channel depletion type transistor for the constant current element 31 on the right side, the p-type channel conduction layer 53a is first diffused in a predetermined range on the surface of the epitaxial layer 53 with a low impurity concentration and then shallowly. , Gate
59 is provided and a p-type source layer 65 is diffused on both sides thereof with a high impurity concentration.

An output circuit in which the gate control circuit 40 of the present invention is incorporated by deriving terminals from the above-mentioned circuit elements by a usual aluminum wiring film 69 arranged at the essential points and providing wiring as shown in the drawing. To do. Since the resistors such as the current setting resistor 31 are all high in resistance, it is preferable to leave the polycrystalline silicon for the gate 59 on the thick oxide film 55 and form it from the polycrystalline silicon. Further, the surface of the integrated circuit device 50 is covered with a usual protective film, but it is omitted in FIG. 4 for the sake of simplicity.

[0027]

As described above, in the gate control circuit of the present invention, the gate control circuit is connected in the opposite direction between the control transistor which receives the low voltage signal and is turned on and off, and the gate of the gate control element and the power supply voltage point. Zener diode,
The breakdown voltage of the Zener diode is higher than the operating threshold value of the gate of the gate control element and the breakdown voltage value By setting it lower, the gate control voltage for turning on the gate control element on the high voltage side can be held constant regardless of the power supply voltage, and the range of the power supply voltage applicable to the gate control circuit can be expanded.

The embodiment of the present invention in which a constant current element is inserted in the current path has the effect of keeping the current consumption of the gate control circuit substantially constant regardless of the power supply voltage, and operates as a control transistor in response to a low voltage signal. The embodiment using the driven side transistor of the current mirror circuit in which is stopped has the advantage of further enhancing this effect. The embodiment in which the high impurity concentration diode layer of the Zener diode and the source layer of the MOS transistor are simultaneously diffused when the circuit of the present invention is incorporated into an integrated circuit has the effect of simplifying the wafer process and reducing the manufacturing cost.

[Brief description of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention in which a current setting resistor is inserted in a current path.

FIG. 2 is a circuit diagram showing an embodiment of the present invention in which a constant current element is inserted in a current path.

FIG. 3 is a circuit diagram showing an embodiment of the present invention in which a driven transistor of a current mirror circuit is used as a control transistor.

FIG. 4 is a cross-sectional view of a wafer showing a structural example of main circuit elements constituting a gate control circuit according to the present invention incorporated in an integrated circuit device.

FIG. 5 is a circuit diagram of a conventional level shift type gate control circuit.

[Explanation of symbols]

1 High voltage side gate control element or MOS transistor 2 Low voltage side gate control element or MOS transistor 10 Control transistor 11 Current mirror circuit reference side transistor 20 Zener diode 21 Zener diode parallel resistance 30 Current path 31 Current setting resistance 32 Constant current element or depletion type MOS
Transistor 40 Gate control circuit 50 Integrated circuit device 63 MOS transistor p-type source layer 64 Zener diode p-type diode layer 66 MOS transistor n-type source layer 67 Zener diode n-type diode layer E Ground potential or Ground potential Sd Low-voltage signal V High-voltage power supply point or power supply voltage Vd Low-voltage power supply voltage

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Internal reference number FI Technical indication location H01L 29/78 H03K 17/687 H01L 29/78 301 K 9184-5K H03K 17/687 G

Claims (5)

[Claims] 1. A circuit for controlling on / off of a gate control element connected to a high voltage side by a low voltage signal, comprising:
A control transistor that is connected to the low voltage side and that turns on and off by receiving a low voltage signal, a Zener diode that is connected in the reverse direction between the gate of the gate control element and the high-voltage power supply point, and the gate and control of the gate control element And a current path that is opened and closed by the on / off operation of the control transistor by mutually connecting the transistors, so that the breakdown voltage of the Zener diode is set to be higher than the gate operation threshold value of the gate control element and lower than its gate breakdown voltage value. A gate control circuit characterized by the above. 2. A gate control circuit according to claim 1, wherein a current setting resistor is inserted in a current path. 3. A gate control circuit according to claim 1, wherein a constant current element is inserted in the current path. 4. A gate control circuit according to claim 1, wherein a driven transistor of a current mirror circuit for starting and stopping an operation in response to a low voltage signal is used for the control transistor. 5. The circuit according to claim 1, wherein the Zener diode is incorporated into an integrated circuit together with a MOS transistor as a gate control element, and the high impurity concentration diode layer of the Zener diode is co-diffused with the source layer for the MOS transistor. And a gate control circuit.