JP2815434B2 - Output circuit device - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an output circuit device for driving a capacitive load.

2. Description of the Related Art As an output circuit device of this type, a circuit configuration as shown in FIG. 3 has been conventionally known.

Hereinafter, a conventional example will be described with reference to FIG. In FIG. 3, reference numeral 1 denotes an NPN transistor serving as a current supply means;
Is an NPN transistor which forms a current outflow means, 3 is a power supply terminal, 4 is an output terminal, 5 is a ground terminal, 6 and 7 are power supply flows, 8 and 9 are NPN transistors which form a switching means, and 10 is opposite to a normal phase output. A logic gate forming a distribution means for outputting a phase output, 11
Is an upper limit voltage regulating means connected to the output terminal 4.

The transistor 1 and the transistor 2 are directly connected between the power supply terminal 3 and the ground terminal 5 to form a totem-pole type output circuit. The transistor 1 supplies a current to a load connected to the output terminal 4, and 2 draws a load current and causes a current to flow to the ground terminal 5. Furthermore,
The transistor 1 has a base connected to the collector of the transistor 8 having the current source 6 at the collector, and operates in response to the switching operation of the transistor 8. The transistor 2 has a base connected to the collector of the transistor 9 having the current source 7 at the collector, and operates in response to the switching operation of the transistor 9. The transistors 8 and 9 are switching-controlled in opposite directions by the positive-phase output and the negative-phase output of the logic gate 10, and perform a transistor operation of alternately turning on the transistors 1 and 2.

The upper limit power supply restricting means 11 is connected between the output terminal 4 and the ground terminal 5 and limits a rise in the voltage of the output terminal 4 by a predetermined potential, and is used when the withstand voltage of the load is limited.
Therefore, without the upper limit voltage regulating means, the upper limit voltage of the output terminal 4 fluctuates depending on the power supply voltage applied to the power supply terminal 3, and when the power supply voltage is unstable and jumps to a higher voltage, the upper limit of the output terminal 4 There is a possibility that the voltage exceeds the withstand voltage of the load, and the upper limit power supply regulating means 11 is provided to limit such fluctuations.

Next, FIG. 4 is a circuit example that embodies the conventional example of FIG. 3, and will be described based on the circuit configuration of FIG.

In FIG. 4, 101 to 104 are current sources, and 105 to 113 are NPN.
Transistors, 114 to 116 are diodes, 117 is a Zener diode connected externally, 118 to 121 are resistors, 122, 123
Is a voltage source for power supply, 124 and 125 are external resistors, and 126 is a MOS transistor as a load.

The transistors 105 and 106 form a totem-pole type output circuit connected in series between the power supply terminal 3 and the ground terminal 5. Then, the transistor 105 and the transistor 1 having the emitter connected to the base of the transistor 105
07 constitutes a Darlington circuit and constitutes current supply means capable of sufficiently supplying current to the load, while the transistor 106 drives the load current sufficiently by the supply of the base current by the current source 103. It forms the current outflow means. When a high level is input to the input terminal, the transistor 113 is turned on, the transistors 110 and 111 connected to the subsequent stage are turned off, and the transistor 106 is turned on. On the other hand, the transistor 112 connected to the collector output of the transistor 113 is turned off, the transistor 108 is turned on, and the transistor 109 is also turned on, so that the base potentials of the transistors 105 and 107 become low level. A low level is output to the output terminal 4.

Next, when a low level is input to the input terminal, the transistor 113 is turned off, the transistors 110 to 112 connected to the output are turned on, and the transistors 108 and 109 are turned off. Since the potential is at a high level and the base of the transistor 106 is at a low level, a high level is output to the output terminal 4.

The resistors 118 to 110 are provided to drive the transistors 110 to 112 in parallel, and the diodes 114 to 116 are provided to limit the reverse bias between the base and the emitter when switching the transistors 105 and 107. The power terminal 3 is a power terminal for the output stage, and the power terminal 12
Is used as a power supply terminal for pre-driving, so that when driving a large load, even if the regulation of the external voltage source 123 is not good, the power supply fluctuation of the external voltage source 123 does not affect the power supply terminal 12 side.

Problems to be Solved by the Invention In the conventional output circuit device as described above, when the gate of the MOS transistor 126 is directly connected to the output terminal 4 to drive the gate, the high level of the output voltage depends on the power supply voltage. If there is a change and the regulation of the external voltage source 122 or 123 is poor, there is a risk that the output terminal 4 will output an output voltage higher than the gate withstand voltage. Therefore, as shown in FIG. 4, a power limiting resistor 124 is provided between the output terminal 4 and the ground point.
And a series circuit of a Zener diode 117 to drive the gate while limiting the input voltage of the gate. However, if the resistor 124 is connected to the gate input, which is a capacitive load of the output terminal 4, the waveform of the gate input becomes dull.
Choose only a small value of about Ω. Then, when the voltage of the output terminal 4 is high, a large current flows through the resistor 124 and the Zener diode 117, and accordingly, the current flowing through the power supply terminal 3 also increases, and the power consumption in the output circuit device increases. there were.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and to provide an output circuit device with high power supply efficiency.

Means for Solving the Problems To achieve this object, the present invention is an output circuit device for driving a capacitive load connected to an output terminal (4), wherein a power supply terminal (3) is connected to a collector. A first transistor having the output terminal connected to an emitter;
A second emitter-grounded transistor (2) having the output terminal connected to the collector, and a current source (6) connected to the collector.
A grounded third transistor having a collector output to drive the base of the first transistor (8)
A Zener diode connected between the collector of the third transistor and a ground point to regulate a high-level upper limit voltage by a breakdown voltage; and the second transistor (2).
And a circuit means (10) for driving the bases of the third and fourth transistors (8, 9) with signals having phases opposite to each other. It is.

According to the above configuration, the base potential of the first transistor which is activated when a high level is output from the output terminal is regulated by the breakdown voltage of the Zener diode. Regardless, it can be stabilized. Further, since the voltage is limited on the base input side of the first transistor, the Zener diode can be operated with a small current, and the power consumption when the voltage is limited can be reduced.

Embodiment Hereinafter, an output circuit device of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram of an output circuit device according to an embodiment of the present invention. In FIG. 1, 1, 2, 8, and 9 are bipolar transistors, 3 is a power supply terminal, 4 is an output terminal, and 5 is an output terminal. Is a ground terminal, 6 and 7 are power supply flows, 10 is a logic circuit for outputting a normal output and an inverted output, and 13 is an upper limit voltage regulating means composed of a Zener diode.

A transistor 1 having a collector connected to the power supply terminal 3 and an emitter connected to the output terminal 4 and a transistor 2 having a collector connected to the output terminal 4 and having a grounded emitter 2 constitute a totem-pole type output circuit. The base of the transistor 2 is controlled by a common-emitter transistor 8 having a current source 6 at the collector, and the base of the transistor 2 is controlled by a common-emitter transistor 9 having a current source 7 at the collector. Apply the forward output of circuit 10,
An inverted output of the opposite phase is applied to the base of the transistor 8. Further, the collector of the transistor 8 is connected to upper limit voltage regulating means 13 composed of a Zener diode, and the high level of the collector potential of the transistor 8 is restricted by the upper limit voltage regulating means.

Now, the current value of the current source 6 is set to a value of a base current sufficient for the transistor 1 to drive the load when the voltage of the output terminal 4 is at a high level. Power loss in the upper limit voltage regulating means 13 is also reduced.

Next, FIG. 2 shows another example of a circuit that further embodies the circuit configuration of FIG. In FIG. 2, reference numerals 3 and 12 denote power terminals and 4
Is an output terminal, 5 is a ground terminal, 101 to 104 are current sources, 105 to 1
13 is an NPN transistor, 114 to 116 are diodes, 217
Is a Zener diode, 118 to 121 are resistors, 122 and 123 are external voltage sources, 124 and 125 are external resistors, and 126 is a MOS as a load.
It is a transistor.

In FIG. 2, the transistor 105 and the transistor 107 whose collectors are connected to the power supply terminal 3 form a Darlington circuit, and the current capability when outputting a high level to the output terminal 4 is increased. The transistor 106 having a common emitter and a collector connected to the emitter of the transistor 105 and a transistor 105 constitute a totem-pole type output circuit to increase the switching speed of the load current. The transistor 108 connected between the base of the transistor 105 and the ground terminal discharges the electrification stored in the base of the transistor 105 and hastens the cutoff of the transistor 105. The transistor 110 connected between the base and the emitter of the transistor 106 has the same function.

Transistor 109 that drives the base of transistor 107
Has a current source 104 at the collector and is turned off when the transistors 105 and 107 are turned on to supply the current of the current source 104 to the base of the transistor 107. However, since the Zener diode 217 is connected between the collector of the transistor 109 and the ground terminal 5, the collector potential is regulated by the breakdown voltage of the Zener diode 217.

Then, when a high-level signal is input to the input terminal, the common emitter transistor 113 is turned on, and the transistors 110 to 112 connected to the collector output are turned off. At this time, the transistor 108 is turned on by the current supplied from the current source 102, and pulls the base potential of the transistor 105 to a low level. At the same time, transistors
The transistor 109 is also turned on, driving the base of the transistor 106 with the emitter current of the transistor 109, while pulling the base potential of the transistor 107 to a low level. As a result, the transistor 106 is turned on, and the transistors 105 and 107 are turned on.
Is turned off, and the output voltage of the output terminal 4 is set to the low level.

Next, when a low-level signal is input to the input terminal,
Transistor 113 is turned off, turning on transistors 110-112 connected to the collector output. Then, since the transistors 108 and 109 are turned off, the transistor 107
And 105 are turned on by the current from the current source 104, while the transistor 106 is turned off by turning on the transistor 110, and the output voltage of the output terminal 4 is set to a high level.

As described above, the switching control of the voltage of the output terminal 4 is performed, and the output of the MOS transistor 126 connected to the output terminal 4 is stably output by the Zener diode 217 irrespective of the fluctuation of the power supply voltage of the high level voltage of the output terminal 4. The gate electrode is driven at a stable voltage equal to or lower than the gate withstand voltage, and the reliability of the circuit operation can be ensured.

In addition, since the transistor 107 and the transistor 105 form a Darlington circuit, the base current of the transistor 107 can be driven by a current value obtained by dividing the base current of the transistor 105 by the current amplification factor (h _FE ). The current value of the source 104 can be set smaller than that of the current source 6 in FIG. 1, and the power loss can be extremely reduced.

Effects of the Invention As described in detail above, the output circuit device of the present invention has a function of limiting the output voltage inside the circuit, so that a stable output voltage can be obtained without the need for an external Zener diode. Power consumption can be drastically reduced. Further, a device such as a MOS transistor having a low withstand voltage can be driven without impairing reliability.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of one embodiment of the output circuit device of the present invention, FIG. 2 is a circuit diagram of another embodiment of the present invention, FIG. 3 is a circuit diagram of a conventional example, and FIG. FIG. 4 is a specific circuit configuration diagram of FIG. 3 Power supply terminal 4 Output terminal 5 Ground terminal 10
1 to 104: current source, 105 to 113: transistor, 114 to 1
16: Diode, 217: Zener diode, 118 ~
121 ... resistor, 122, 123 ... external voltage source, 124, 125 ... external resistor, 126 ... MOS transistor.

Claims (2)

(57) [Claims] An output circuit device for driving a capacitive load connected to an output terminal, comprising: a first transistor having a collector connected to a power supply terminal and an emitter connected to the output terminal; and a collector having the output terminal. Connected to the grounded second emitter
A third transistor having a current source at the collector, and having a collector output and driving the base of the first transistor with a collector output; and a high-level transistor connected between the collector of the third transistor and a ground point. A Zener diode that regulates an upper limit voltage of a level by a breakdown voltage; a fourth transistor that controls switching of a base of the second transistor; and a base that drives the bases of the third and fourth transistors with signals having phases opposite to each other. An output circuit device comprising: circuit means. 2. An output circuit device for driving a gate electrode of a MOS transistor connected to an output terminal, comprising: a first transistor having a power supply terminal connected to a collector and the output terminal connected to an emitter; A second transistor having a power terminal connected thereto and having the emitter connected to the base of the first transistor, and a third emitter grounded having the collector connected to the output terminal.
And a current source at the collector, the collector output driving the base of the second transistor, and the emitter output the third transistor.
An output circuit device comprising: a fourth transistor that drives a base of the transistor; and a Zener diode having a cathode connected to the collector of the fourth transistor and an anode grounded.