JPS61156911A - Output voltage control circuit - Google Patents

Abstract

PURPOSE:To improve the accuracy by using a collector current of a transistor (TR) as base current control information of the TR via a current mirror circuit comprising TRs so as to decrease the output current dependancy. CONSTITUTION:Since TRs Q16, Q14 have a common base, they are turned on and off identically, and a collector of the TRQ14 is connected to an input node of TRs Q12, Q13 forming the current mirror circuit. The collector of the TRQ12 is connected to a base of a TRQ11 driving the TRs Q14, Q16 to form a feedback loop. A TRQ15 is used to be coupled directly with a microcomputer or the like and its base input logic is TTL. The output voltage is controlled by adjusting a current inputted to the base of the TRQ11 via the feedback loop. Thus, the output current dependancy is reduced and the improvement of accuracy and its maintenance are attained.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an output circuit of a bipolar 2 integrated circuit, etc.
In particular, the present invention relates to an output voltage control circuit that is effective for controlling output voltage.

[Technical background of the invention]

A circuit as shown in FIG. 2 is used as an output circuit of a bipolar integrated circuit. In FIG. 2, 11 is a power supply voltage supply node, which is connected to the collector of transistor Q1 and the emitter of transistor QQ2. The collector node of transistor Q2 is connected to transistor Q1.
The emitter node of the transistor Q1 is set as the voltage output node 13.

Further, a bias current source 12 is connected to the base node of the transistor RO2.

This forms an output circuit with an inverted Gourington connection. In the above output circuit, an input signal is given to the base of transistor Q2, and transistor Q
1 emitter.

[Problems with background technology]

In the conventional output circuit described above, the output voltage value is controlled by changing the value of the power supply chamber 1EEvCC for coupling with other circuits.

However, according to this method, the power source is shared by the input circuit for the output and the additional circuit (within the same IC). As a result, the output voltage Vout of the output circuit
When the power supply voltage VCC is swept in order to vary the power supply voltage, other circuits are affected by the power supply voltage, so countermeasures are required.

In addition, in the conventional output circuit, a large current flows and the output chamber 8
When changing EVout, naturally this system IC
Although an external control circuit (element) is required, a power element (power transistor, power diode, etc.) for driving a large current must be used. In other words, it is difficult to interface this system IC alone with a microcomputer, and it becomes necessary to use a power element.

Furthermore, the theoretical formula for the control voltage is: Vout, = VCC-(VBz +VOB (sa
t) ). 'i'BP is a ground voltage between the base and emitter of the transistor Q1, and VcE (sat) is a saturation voltage between the converter and emitter of the transistor Q2. Therefore, V
aE(sat) (D term is VBRK ratio power output'#t
, the R dependence is large and the accuracy is not good - [Objective of the Invention] This invention was made in view of the above circumstances, and it is possible to vary the output voltage without controlling the power supply voltage, and also to reduce the current dependence of the output voltage. There is no control circuit (micro combiator) without any output and four variable output control terminals.
It is an object of the present invention to provide an output voltage control circuit that can be easily coupled to the output voltage control circuit.

[Summary of the invention]

For example, as shown in FIG. 1, in an inverted Darlington connection circuit between a drive transistor qzz and an output transistor Q16, a feedback transistor Q14 which shares a base with an output transistor Q1G is connected to a feedback transistor Q14.
In addition, the current of this transistor Q14 can be controlled by a current control circuit formed by a transistor Q15. Then, the collector current of the transistor Q14 is used as base current control information of the transistor Qll via a current mirror circuit including transistors Q I 2 and Q10.

This achieves the above objective.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 shows an embodiment of the present invention, which is configured as a bipolar integrated circuit. 21 is a power supply voltage supply node, and transistors Q Z Z; Q12 . It is connected to the emitter of Q13 and the collector node of transistor Q16. A bias current source 22 is connected to the base of the transistor Qll, and the collector of the transistor Q12 is connected to this base. Transistor Q12. The bases of Q3 are commonly connected to transistors Q13. Q
14 collector nodes. Further, the collector node of transistor Qll is connected to transistor Q14.
Connected to the base of Q16. And transistor Q
The emitter of Q14 is connected to the emitter of transistor Q15, and the collector of transistor Q15 is connected to the reference ground wire. At the base of transistor Q15,
A control signal input node 23 is provided for varying the output voltage.

Further, the output voltage Vout is taken out from the emitter of transistor QI6.

One embodiment of the present invention is constructed as described above, and has a bias current source 2 driving the transistor Q16 at the final end.
Feedback is applied to the second side, and the logical expression of the output voltage is constructed so that only the VBEe term, which is less dependent on the output 'α current, is used.The operation of the above circuit will be explained as follows. Transistor Q14. Since Q16 shares the base,
Get the same on-off behavior.

The collector of the transistor Q14 is a transistor Q forming a current mirror circuit.12. Connected to the input node of QIB. The collector of transistor QZ2, which becomes the output node of the current mirror circuit, and the transistor Q1
4. It is connected to the base of the transistor Qll that drives Q16, forming a feedback loop. Further, the current source 22 applies a bias to the base of the transistor Qll. Transistor Q15 enables direct connection to a microcomputer, etc., and its base input is
It is at TTL level.

According to the above circuit, in order to control the output voltage, the amount of current of the transistor Q15 can be changed, and the amount of current of the transistor Qll, which sets the base bias of the transistor Q16, can be changed.

In other words, the objective can be achieved by adjusting the amount of current input to the base of the transistor Qll via the feedback loop.

〔Effect of the invention〕

According to the circuit of the present invention described above, the following effects can be obtained.

(1) Even if the power supply voltage VCC is constant, the output voltage Vout O varies depending on the voltage applied to the control signal input node 23.
Value can be changed. Therefore, it is no longer necessary to take conventional measures to suppress power supply voltage dependence on other circuits (input circuits, additional circuits, etc.) configured in the same IC chip and sharing the power supply.

(2) Since the input current of the control signal hexagonal node 23 is the base current of the transistor Q15, the transistor Q1
2. Even if the current mirror ratio of Q13 is 1:1, this current is approximately (bias current/hfe of transistor Q15).

Specifically, if the bias current is 6mA, 6mA/
20=300 μA, which is the TTL level. This means that direct connection to a microcomputer is possible as a control signal.

(3) The logical formula for the output voltage Vout is Vout =
Control voltage +VBE (Q75) +VBE (Q74
)-VBg(Q26). Therefore, the output voltage Vout can be set to VBE with less dependence on the output current, and it is possible to improve and maintain the output voltage VOUT.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a conventional output circuit. Qll~Q16...transistor, 21...power supply'
411E supply node, 22...bias current source, 23
... Controlled PII signalman Kanode. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2

Claims (1)

[Claims] The collector of a drive transistor whose base is connected to a bias current source is connected to the base of an output transistor, and the emitter of the drive transistor and the collector of the output transistor are connected to a power supply voltage supply node. In the Darlington-connected output circuit, a feedback transistor shares a base with the output transistor and has a current control circuit connected to its emitter, a collector output of this feedback transistor is supplied to an input node, and an output node is connected to the drive transistor. and a current mirror circuit connected to the base of the output voltage control circuit.