JPH04103214A - High breakdown voltage output circuit - Google Patents

Abstract

PURPOSE:To make an output of the high breakdown voltage output circuit stable by keeping a gate electrode and a point of a 2nd reference potential to a prescribed voltage higher than a 1st power supply. CONSTITUTION:When an input signal is at an L level, a transistor(TR) 3 is turned on, a TR 4 is turned off and a signal with an H level closer to a power supply VDD is fed to a gate of a TR M2. The TR M2 is turned on through the application, a TR Q1 is turned on and a constant current flows from an emitter of the TR Q1 to a constant voltage diode D2. Thus, a prescribed voltage Vz set higher than the voltage of the power supply VDD is fed to the gate of the TR M2 and a drive current of the TR M2 is much increased. Thus, the output of the high breakdown voltage output circuit is made stable.

Description

[Detailed Description of the Invention] [Object of the Invention] (Industrial Application Field) The present invention is applicable to high voltage output circuits used in integrated circuits for driving flat panel displays that require high driving voltages, for example. In particular, the present invention relates to increasing the drive output and stabilizing the output.

(Prior Art) Flat panel displays (FDPs) have come to be used as display devices in place of cathode ray tubes. Since this flat panel display requires a high drive voltage to drive, a high voltage output circuit capable of outputting a relatively high drive voltage is used as a driving integrated circuit.

Complementary MO3 (
CMO8) It is known that a load resistor is added to an oven-drain type high-voltage output circuit composed of a circuit element and a high-voltage circuit element.

FIG. 3 is a diagram showing an eight high-voltage circuit in which a load resistor is added to such an oven-drain type high-voltage output circuit.

In other words, the input section 1 is a low voltage P channel C.
MO8) Transistor Tri and N-channel CMOS
It is composed of a transistor Tr2. The respective gates of these transistors T rL T r2 are commonly connected to the input terminal IN, and the respective drains are commonly connected to the gate of the dabrasion MOS type transistor (DMO8) Ml of the output section 2.

The source of the transistor Tri is the low voltage power supply VD.
The source of the transistor Tr2 is connected to the reference potential G1 of the CMO8 circuit having the input section 1.

Furthermore, in the output section 2, the transistor M1
Its drain is connected to the high voltage power supply HVCC via a load resistor R1, and its source is connected to the reference potential G2 of the output section 2. Further, an output terminal OUT is connected to the drain of the transistor M1.

To explain the operation of the conventional high-voltage output circuit configured in this way, when the input signal input to the input terminal IN is low (
If it is at the L) level, the transistor Tri is turned on and the transistor Tr2 is turned off, so that a high (H) level signal with the same potential as the power supply VDD is applied to the gate of the transistor M1 at the gate-source voltage VG.
Applied as S. As a result, the transistor M1
is turned off, and an H level signal having a voltage equivalent to that of the power supply HVCC is output to the output terminal OUT.

On the contrary, the input signal input to the input terminal IN is high.
If the voltage is at the level, the transistor Tri is turned off and the transistor Tr2 is turned on, so that an L level signal having a potential equal to the reference potential Gl is applied to the gate of the transistor M1. As a result, the transistor M1 is turned on, and an L-level output having a potential equivalent to the reference potential G2 corresponding to the gate-source voltage VGS is outputted to the output terminal OUT.

(Problems to be Solved by the Invention) In the high voltage output circuit having the configuration shown in FIG.
The drive current of transistor M1 is equal to the gate-source voltage V
Proportional to GS. Therefore, in order to obtain a large drive current, the gate-source voltage must be increased. However, since the gate-source voltage uses the voltage of the power supply VDD (usually about 5V), it is difficult to increase it higher than this. Moreover, the on-operation of the transistor M1 is greatly influenced by its threshold voltage VTR.

Therefore, in order to increase the drive current of the high-voltage output circuit in order to stabilize the drive of a flat display, etc., there is a method of increasing the area of each element electrode constituting the circuit and increasing the electrode size of the transistor M1. There is no other choice. However, this method increases manufacturing costs and has the effect of increasing the propagation delay time in terms of transistor characteristics.

Furthermore, in the above-described high voltage output circuit, the reference potential G1 of the input section 1 and the A reference potential G2 for the output section 2 is provided separately.

For this reason, when a large current is output from the output section 2, the potential of the reference potential G2 increases due to the impedance of aluminum used in the wiring for the reference potential G2 (
(apparently the threshold voltage VTH increases),
The value of the gate-source voltage vGS of the transistor M1 decreases, and therefore the output current also decreases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a high voltage output circuit that can increase the drive current and reduce the influence of fluctuations in the threshold voltage of high voltage output circuit elements.

[Structure of the Invention] (Means for Solving the Problems) In order to solve the problems of the prior art, the present invention provides an input terminal connected between a first power source and a first reference potential, A low voltage circuit element is turned on and off according to the signal level, and one of the current paths is connected to an output terminal and a second power source having a higher potential than the first power source via a load resistor, and one of the current paths is a high voltage circuit element connected between the low voltage circuit element and the high voltage circuit element, the other being connected to a second reference potential and a gate electrode connected to the output end of the input means; a driving means for outputting a predetermined current when driving the circuit element; and a driving means connected between the gate electrode of the high-voltage circuit element and a second reference potential, and receiving the predetermined current from the driving means to output a predetermined current to the gate electrode. and a constant voltage means for maintaining a voltage between the second reference potential and the second reference potential at a predetermined voltage higher than the first power source.

(Function) According to the above configuration, the high voltage output circuit of the present invention improves the drive current capability of the output transistor that constitutes the output section of the conventional circuit, and also improves the drive current capability due to fluctuations in the threshold voltage VTR. The impact will be less. In addition, since the gate-source voltage VGS of the output transistor is set by a constant voltage diode, there is no voltage fluctuation, and a constant drive current can be supplied to the output transistor, which stabilizes the output of the high voltage output circuit. I can figure it out.

(Example) Hereinafter, an example of the present invention will be described in detail with reference to the drawings.

FIG. 1 shows a circuit configuration of a high voltage output port according to a first embodiment of the present invention.

That is, the input terminal IN is connected to the P-channel CMO8) transistor Tr3 and the N-channel CMO that constitute the input section 10.
MO8) Commonly connected to each gate of transistor Tr4. The input of the transistor Tr3 is connected to the anode of the diode D1, and the source is connected to the low voltage power supply VDD. Further, the drain of the transistor Tr4 is connected to the cathode of the diode D1 and the DMO8h of the output section 20.
Connected to the gate of transistor M2. Furthermore, the source of the transistor Tr4 is connected to the reference potential G1 of the input section 10.
It is connected to the. The transistors Tr3 and Tr4 are connected in a so-called inverter configuration.

Further, the drain of the transistor M2 of the output section 20 is connected to one side of the load resistor R2, and the source is connected to a separately set reference potential G2 of the output section 20 at the same potential as the reference potential G1.

The other of the load resistors R2 is connected to a high voltage power supply HVCC via a load resistor R3, and an output terminal OUT is provided between the transistor M2 and the load resistor R2.

Furthermore, a constant voltage diode D2 is provided, the cathode of which is connected to the gate of the transistor M2, and the anode of which is connected to the reference potential G2.

Further, the base is connected to the connection point between the load resistors R2 and R3, and the collector is connected to the power supply HVCC through the load resistor R4.
a PNP transistor Q1 whose emitter is connected to the gate of the transistor M2 and serves as a constant current source;
will be provided.

The operation of the high voltage output circuit having this configuration is such that when the input signal input to the input terminal IN is at a high (H) level, the transistor Tr3 is turned off, and the transistor Tr3 is turned off.
r4 is turned on, so that a low (L) level output having a potential equivalent to the reference potential G1 is applied to the gate of the transistor M2. This turns off the transistor M2, and outputs an H level signal that is supplied from the power supply HVCC to the output terminal OUT and becomes a predetermined voltage by the load resistors R2 and R3.

On the contrary, if the input signal is at L level,
The transistor Tr3 is turned on and the transistor Tr4 is turned off, so that an H level signal having a potential approximate to the power supply VDD is applied to the gate of the transistor M2.

Due to this application, the transistor M2 is turned on, and the transistor Q1 is also turned on, and this transistor Q
A constant current is supplied from the emitter of D1 to the constant voltage diode D2. As a result, a predetermined voltage Vz set higher than the voltage value of the power supply VDD is applied to the gate of the transistor M2, thereby further increasing the value of the drive current of the transistor M2. As a result, the output terminal O
An L level potential equivalent to the reference potential G2 is output to the UT.

The diode D1 has the predetermined voltage Vz connected to the power supply VD.
This is provided to prevent the drive current from flowing backwards from the drain of the P-channel transistor Tri to the CMO8 circuit when the voltage becomes higher than the voltage value of D.

Therefore, the predetermined voltage Vz applied to the gate of the transistor M2 is set higher than the voltage value of the power supply VDD, so that the current driving ability of the transistor M2 is improved and a larger current can be output than in the past. I can do it.

Furthermore, fluctuations in the signal input from the input section 10 no longer directly affect the drive current of the transistor M2.

Furthermore, by increasing the predetermined voltage Vz, the dependence of the driving of the transistor M1 on the threshold voltage VTH can be reduced.

FIG. 2 shows a circuit diagram as a second embodiment.

In this second embodiment, the transistor Q1 in the circuit configuration of the first embodiment described above is changed to a p-channel DMO8) transistor M3. Other than this change, the circuit configuration is the same as that of the first embodiment, operates in exactly the same way, and provides the same effects.

Also, when comparing the high voltage output circuit of the present invention with the conventional circuit,
When a higher level of output than the current level is required, in conventional circuits the electrode area of the output transistor occupies a large semiconductor substrate, which may increase the substrate size, but with the circuit configuration of the present invention, it can be used as a constant current circuit. Even if a voltage circuit element is added, the area occupied by the output transistor is reduced, the area of the semiconductor substrate is not increased, and the current substrate size may be maintained or reduced.

Therefore, in the high voltage output circuit of the present invention, the drive current capability of the output transistor constituting the output section of the conventional circuit is improved, and the influence of fluctuations in the threshold voltage VTH is reduced. Furthermore, since the gate-source voltage vGS of the output transistor is set by a constant voltage diode, voltage fluctuations are eliminated, a constant drive current can be supplied to the output transistor, and the output of the high voltage output circuit can be stabilized.

Furthermore, the present invention is not limited to such embodiments, and it goes without saying that various modifications and applications can be made without departing from the gist of the invention.

[Effects of the Invention] The high withstand voltage output circuit of the present invention as detailed above can improve the drive current capability of the high withstand voltage output circuit element that constitutes the output section of the conventional circuit, and can also suppress voltage fluctuations by the constant voltage means. Therefore, a constant drive current can be supplied to the high voltage output circuit element, and the output of the high voltage output circuit can be stabilized.

[Brief explanation of the drawing]

FIG. 1 is a circuit configuration diagram of a high voltage output circuit according to a first embodiment of the present invention, FIG. 2 is a circuit configuration diagram of a high voltage output circuit according to a second embodiment, and FIG. FIG. 3 is a circuit configuration diagram of a voltage-resistant output circuit. Try, Tr4. Ml, M2. M3. Ql"')' transistor, D2... constant voltage diode, R2, R3゜R
4...Resistance, VDD, HVCC...Power supply. Applicant's representative Patent attorney Takehiko Suzue HVCC (1A2 Den 7 Yoni) HVCC Figure 2

Claims (1)

[Claims] A low voltage circuit element connected between a first power supply and a first reference potential and turned on and off according to the level of an input signal from an input terminal; and one of the current paths is an output. A terminal and a second power source having a higher potential than the first power source are connected via a load resistor, the other current path is connected to a second reference potential, and a gate electrode is connected to the output terminal of the low voltage circuit element. a high-voltage circuit element connected to the high-voltage circuit element; a driving means connected between the low-voltage circuit element and the high-voltage circuit element and outputting a predetermined current when driving the high-voltage circuit element; is connected between the gate electrode and the second reference potential, receives the predetermined current from the driving means, and connects the first reference potential between the gate electrode and the second reference potential.
1. A high withstand voltage output circuit comprising: constant voltage means for maintaining a predetermined voltage at a higher potential than a power supply.