JPH11127592A - Output control device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To achieve an output control device that has a conduction circuit to a load in a bipolar transistor is connected in bridge form has a low power consumption, and has improved response by controlling a power supply line for supplying power to the conduction circuit to a minimum potential level where a power transistor is not saturated, regardless of the size of current of the conduction circuit. SOLUTION: An output control device is provided with a drive device 2 for driving each of bipolar Q11-Q14 of a conduction circuit 1, a voltage detection means 6 for detecting a voltage which is applied to the base of each of bipolar transistors Q11 and Q12, and a power supply voltage control means for changing a power supply voltage Vcc supplied to the conduction circuit 1, based on the detection output of the voltage detection means 6.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an output control device in which an energizing circuit for energizing a load such as a motor is composed of a bipolar transistor, and more particularly to a power supply voltage of a power supply line for supplying power to the energizing circuit. The improvement of the circuit part for controlling

[0002]

2. Description of the Related Art Conventionally, as an output control device for controlling driving of a load such as a motor, for example, a device having a configuration shown in FIG. 3 has been provided.

An output control device shown in FIG. 3 is an energizing circuit for energizing a load (here, a motor) 10 and includes four NPs.
It is configured by connecting N-type power transistors Q11 to Q14 in a bridge type.

A driving device 2 drives the energizing circuit 1 based on an input signal 3 for servo control of the motor 10, and each of the power transistors Q11 to Q11 according to the input signal 3.
By changing the base current of Q14, the power supplied to the motor 10 is controlled.

Reference numerals 4a and 4b denote output terminals from which signals having phases opposite to each other are output from the output unit 1 for forward and reverse rotation.
The motor 10 is connected to a and 4b.

Reference numeral 6 denotes a voltage detecting device for detecting the output voltage on the high voltage side of the two output terminals 4a and 4b.

Reference numeral 7 denotes a power supply voltage control device for controlling the power supply voltage Vcc applied to the power supply line 8 based on the detection output of the voltage detection device 6, and 9 denotes a power supply for supplying power to the energizing circuit 1.

Next, the operation of the above configuration will be described.

First, when an input signal 3 for servo control of the motor 10 is applied to the driving device 2, the driving device 2 responds to the input signal 3 by driving the power transistors Q 11 to Q 11 of the energizing circuit 1.
Q14, for example, the lower right power transistor Q14
To supply a base current to turn it on. At the same time, the input signal 3 is also supplied to the upper left power transistor Q11.
The power transistor Q11 is also turned on to supply a base current proportional to the magnitude of the power transistor Q1. At that time, since the base current is not supplied to the remaining two power transistors Q12 and Q13 of the energizing circuit 1, both power transistors Q12 and Q13 remain off.

As a result, one output terminal 4a is at a high level and the other output terminal 4b is at a low level. Therefore, a current flows from one output terminal 4a to the other output terminal 4b via the motor 10, and, for example, the motor 10 is rotated forward.

The power transistors Q13 and Q12 are turned on, and the remaining two power transistors Q11 and Q12 are turned on.
When Q14 is turned off, the other output terminal 4b is at a high level and one output terminal 4a is at a low level, so that the motor 10 is reversed.

The voltage at each of the output terminals 4a and 4b at that time is taken into the voltage detection device 6, and one of the two output voltages having a higher potential is guided to the power supply voltage control device 7. For example, as described above, when the motor 10 is rotating forward, the voltage V _4a of the output terminal 4a on the high level side is taken in.

At this time, in the prior art, the power supply voltage control device 7 controls the power supply voltage Vcc applied to the power supply line 8 to be always higher than the voltage V _4a detected by the voltage detection device 6 by a constant value α. Is controlled. That is, the power supply voltage Vcc is set so that Vcc = _V4a + α '.

The reason why the power supply voltage Vcc is always increased by a constant value α from the detection voltage Va as in the equation (1) is as follows.

[0015] For example, if you want to change the rotational speed of the motor 10, the drive unit 2 is to change the base current I _B to the upper power transistor Q11 of the energizing circuit 1 based on the input signal 3, along with this collector current I _C is also detected voltage Va increases and decreases varies. However, if the power supply voltage Vcc is set to be always higher than the detection voltage Va by a constant value α (that is, if the formula is satisfied), the collector-emitter voltage V _CE is V _CE = V _EE −V _4a = α (constant). If the potential difference α is set small in advance, heat generation of the upper transistor Q11 to which the power supply voltage Vcc is applied can be suppressed as much as possible, and power consumption can be reduced.

Although the upper left power transistor Q11 has been described above, the same applies to the upper right power transistor Q13.

[0017]

In the above-mentioned conventional configuration, the potential difference α between the voltage Va input to the power supply voltage control device 7 and the power supply voltage V _DD of the power supply line 8 controlled by the voltage Va is determined. Since it is always constant, the following problems arise depending on how the potential difference α is set.

That is, as described above, in order to reduce power consumption, the smaller the potential difference α is, the better. However, if the potential difference α is too small, the power transistors Q11 and Q13 on the upper side of the energizing circuit 1 will have a large potential difference. Saturation is likely to occur when current flows. In other words, if you want to forward the motor 10, for example at high speed, the base current I _B to the upper power transistor Q11 is increased. As a result, the collector current I _C also tends to increase, but substantially the power transistor Q1
Since the voltage α applied to 1 is small, the power transistor Q11 immediately saturates, and the collector current I _C as originally required does not flow.

As a result, only a voltage V _4a smaller than the originally required output voltage is output to the motor 10, which causes a problem that the power supply to the motor 10 is insufficient and the response is deteriorated.

Conversely, if the potential difference α is set to be large beforehand so that the upper power transistors Q11 and Q13 do not saturate, the upper power transistor Q1
1, Q13 is less likely to be saturated,
For example, when it is desired to rotate forward at low speed, the potential difference α
Is greater, the loss of each power transistor Q11, Q13 increases.

As described above, in the conventional apparatus, problems occur depending on the setting of α, and it is difficult to achieve both low power consumption and high responsiveness.

The present invention solves the above-mentioned conventional problems, and it is possible to reduce the power consumption of the upper power transistor as much as possible to reduce the power consumption, and to secure the responsiveness by preventing the saturation. It is an object to provide an output control device.

[0023]

SUMMARY OF THE INVENTION In order to solve this problem, the present invention relates to an output control device provided with an energizing circuit for a load in which bipolar transistors are connected in a bridge type, and is configured as follows. ing.

That is, according to the present invention, a driving device for driving each bipolar transistor of the energizing circuit, voltage detecting means for detecting a voltage applied to the base of the bipolar transistor, and a detection output of the voltage detecting means are provided. Power supply voltage control means for changing a power supply voltage supplied to the energizing circuit.

According to this configuration, the magnitude of the power supply voltage is changed according to the magnitude of the base current. That is, when the supply of power to the load is small (when the base current is small), the power supply voltage is reduced accordingly, so that wasteful power consumption of the power transistor can be suppressed. Further, when the power supply to the load is large (when the base current is large), the power supply voltage increases accordingly, so that the saturation of the power transistor is suppressed, and the responsiveness of the load can be improved. .

[0026]

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

FIG. 1 is a block diagram showing a configuration of a main part of an output control device according to an embodiment of the present invention, and portions corresponding to those of the conventional example shown in FIG. 3 are denoted by the same reference numerals.

The feature of this embodiment is that the base resistors 5a and 5b are connected to the bases of the upper two power transistors Q11 and Q13 which constitute the power supply circuit 1, respectively.

Further, the driving device 2a and each base resistor 5a,
The voltage detection device 6 is connected to each connection point 16a, 16b with 5b.

Further, the power supply voltage control device 7 is configured to control the power supply voltage V _DD supplied to the power supply line 8 of the energizing circuit 1 based on the voltage detected by the voltage detection device 6.

As shown in FIG. 2, the voltage detecting device 6 includes a voltage detecting circuit 6a for detecting the voltage on the high voltage side between the two connection points 16a and 16b, and a voltage level detected by the voltage detecting circuit 6a. Voltage shift circuit 6 that shifts by a predetermined amount
b, and a voltage comparison circuit 6c for comparing the output of the voltage shift circuit 6b with the output of the power supply voltage control device 7.

The other configuration is the same as that of the conventional example shown in FIG. 3, so that the detailed description is omitted here.

Next, the operation of the output control device having the above configuration will be described.

First, when an input signal 3 for servo control of the motor 10 is applied to the driving device 2, the driving device 2 responds to the input signal 3 by turning on the power transistors Q 11 to Q 11 of the energizing circuit 1.
Q14, for example, the lower right power transistor Q14
To supply a base current to turn it on. At the same time, the input signal 3 is also supplied to the upper left power transistor Q11.
The power transistor Q11 is also turned on to supply a base current proportional to the magnitude of the power transistor Q1. At that time, since the base current is not supplied to the remaining two power transistors Q12 and Q13 of the energizing circuit 1, both power transistors Q12 and Q13 remain off.

As a result, one output terminal 4a is at a high level and the other output terminal 4b is at a low level. Therefore, a current flows from one output terminal 4a to the other output terminal 4b via the motor 10, and, for example, the motor 10 is rotated forward.

The voltage V at each connection point 16a, 16b at that time
_The voltage _16a and _V16b are taken into the voltage detection circuit 6a of the voltage detection device 6, and the higher voltage of the two voltages _V16a and _V16b is supplied to the voltage shift circuit 6b. For example, as described above, when the motor 10 is rotating forward, the voltage (V _16a −V _D ), which is reduced by V _D from the voltage V _{16a at} the connection point 16a on the high level side, is changed to the voltage shift circuit. 6b PN
It is supplied as the base voltage of P transistor Q61.
Accordingly, the base voltage V _Q63 of NPN transistor Q63 of the voltage comparator circuit 6c which is connected to the resistor R ₀ of the voltage shift circuit 6b also changes.

On the other hand, the power supply voltage V _DD output from the power supply voltage control device 7 to the power supply line 8 is also supplied as the base voltage of the PNP transistor Q62 of the voltage comparison circuit 6c of the voltage detection device 6. Accordingly, NP of the voltage comparison circuit 6c
The base voltage V _Q64 of the N-transistor Q64 also changes.

The voltage comparison circuit 6c comprises base voltages V _Q63 , V _Q64 of both transistors Q63, Q64 of the voltage comparison circuit 6c.
The power supply voltage control device 7 changes the power supply voltage V _DD applied to the power supply line 8 according to the voltage difference ΔV in order to supply a detection output according to the voltage difference ΔV to the power supply voltage control device 7. Thus, the power supply voltage V _DD will be changed according to the base current I _B which is output from the drive unit 2.

This will be further described using mathematical expressions.

Now, assuming that the voltages of the left and right transistors Q63 and Q64 of the voltage comparison circuit 6c of the voltage detector 6 shown in FIG. 2 are V _Q63 and V _Q64 respectively as described above, the following relational expression is established.

[0041] _{V Q64 = Vcc + V BE (} Q62) V Q63 = V 4a + V BE (Q11) + I B · R 5a -V D + V BE (Q61) + I 0 · R 0 _{However, V BE (Q61), V} BE ( _Q62) … transistor Q61,
The base-emitter voltage of Q62, V _4a ... voltage of one output terminal 4a, V _{BE (Q11)} ... base-emitter voltage of the upper-left side of the power transistor, the base current of I _B ... upper left side of the power transistors Q11, the value of the base resistance 5a for R _5a ... left upper side of the power transistors Q11, the resistance value of the diode constituting the V _D ... voltage detection circuit 6a, the current value of the constant current source I ₀ ... voltage shift circuit 6b, R ₀ ... voltage This is the value of the emitter resistance of the transistor Q61 of the shift circuit 6b.

Here, when the power supply voltage Vcc is appropriately changed to be in an equilibrium state, V _Q63 = V _Q64 , and both PNP transistors Q61 and Q62 are preset so as to have the same characteristics. V _{BE (Q62)} = V
_{BE (Q61)} . Therefore, the formula is
It can be organized as follows.

[0043] _{Vcc = V 4a + V BE (} Q11) + I B · R 5a - to _{(V D -I 0 · R 0} ) where the formula _{(V 4a + V BE (Q11} ) + I B · R 5a) is upper right Of the base resistor 5a of the power transistor Q11 on the side of the driving device 2 at the connection point 16a, and (V
_D− I ₀ · R ₀ ) is a value determined inside the voltage detector 6 and can be regarded as a constant value.

[0044] _{Therefore, α = V BE (Q11)} + I B · R 5a - if put and _{(V D -I 0 · R 0} ), the formula becomes Vcc = V _4a + α.

That is, the above-mentioned '
The α in Formula, is a constant value, the α expression in this embodiment, a function that changes according to the base current I _B.

[0046] Thus as can be seen from the relationship between ,,, for example, when increasing the base current I _B to high-speed rotation of the motor 10, alpha also increased, since Vcc also increases accordingly, both power transistor Even if a large collector current Ic flows through Q11 and Q13, no saturation occurs, and no power shortage occurs. Therefore, high responsiveness can be secured.

Meanwhile, for example, when the small base current I _B to low speed rotation of the motor 10 also becomes small α In response, both the power transistors Q11,
The loss of Q13 is reduced. Therefore, power consumption can be reduced.

In the above description, for ease of understanding, the case where both power transistors Q11 and Q14 of the energizing circuit 1 are turned on in order to rotate the motor 10 forward has been described. The situation is exactly the same when the other power transistors Q12 and Q13 of the energizing circuit 1 are turned on to turn on the power transistors.

[0049]

According to the present invention, the increase α of the power supply voltage of the power supply line for supplying power to the power supply circuit is changed in proportion to the base current of the power transistor. Irrespective of this, it is possible to control the potential to a minimum level that does not cause saturation of the power transistor, and as a result, it is possible to realize an output control device with low power consumption and excellent responsiveness.

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration of a main part of an output control device according to an embodiment of the present invention.

FIG. 2 is a circuit diagram showing details of a voltage detection device 6 of the output control device of FIG.

FIG. 3 is a block diagram showing a configuration of a main part of a conventional output control device.

[Explanation of symbols]

REFERENCE SIGNS LIST 1 energizing circuit 2 driving device 3 input signal 4a, 4b
... output terminals, 5a, 5b ... base resistance, 6 ... voltage detection device, 6a ... voltage detection circuit, 6b ... voltage shift circuit, 6c ...
Voltage comparison circuit, 7: power supply voltage control device, 8: power supply line, 9: power supply, 10: motor (load), Q11 to Q14 ...
Transistor, Vcc: Power supply voltage.

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Hiroshi Yasuda 1006 Kazuma Kadoma, Kadoma City, Osaka Matsushita Electric Industrial Co., Ltd.

Claims (2)

[Claims] 1. An output control device comprising an energizing circuit for a load formed by connecting bipolar transistors in a bridge type, comprising: a driving device for driving each bipolar transistor of the energizing circuit; and a base for the bipolar transistor. An output control device comprising: voltage detection means for detecting an applied voltage; and power supply voltage control means for changing a power supply voltage supplied to the energizing circuit based on a detection output of the voltage detection means. 2. The semiconductor device according to claim 1, further comprising first, second, and third terminals.
A plurality of voltage-current converting means for forming a first current corresponding to the potential difference between the second terminals from the third terminal to the first terminal and for allowing the second current corresponding to the potential difference to flow into the first terminal. A third terminal of the first and second voltage-current converters is connected to the power supply terminal, a second terminal of the third and fourth current converters is connected to the ground terminal, The second terminal of the conversion means is connected to the third terminal of the third voltage-current conversion means, and the second terminal of the second voltage-current conversion means is connected to the fourth terminal.
And a load is connected between the second terminals of the first and second voltage-current conversion means, and a third terminal of the first to fourth voltage-current conversion means is connected. A drive signal is supplied to one terminal, and the first voltage-current conversion means and the fourth
An output device in which a current path is formed between the second voltage-current converting means and the second voltage-current converting means and the third voltage-current converting means via the load. One end is connected to the first terminal of the voltage-current conversion means, the other end is connected to a first resistor to which a first drive signal is supplied, and the other end is connected to the first terminal of the second voltage-current conversion means. A second resistor to which a second drive signal is applied to the other end, an input terminal pair and an output terminal, wherein the first and second
The other end of the resistor is individually connected to the input terminal pair, and a voltage detector that outputs the higher value of the voltage value applied to the input terminal pair to the output terminal; and an input / output terminal; A voltage shift circuit that connects an output terminal of the detector to the input terminal, adds a predetermined voltage value, and outputs the output terminal, and an output terminal of the voltage shift circuit and the power supply terminal are connected to an input terminal pair, respectively. A voltage comparator that detects a potential difference between the input terminals and outputs an error signal to an output terminal; and an input / output terminal. The output terminal of the voltage comparator is connected to the input terminal, and the power supply terminal is connected to the input terminal. A power supply voltage control device connected to the output terminal to vary a voltage value of the power supply terminal according to the error signal; and the first and fourth voltage-current conversion means and the first resistor, or The second and third voltage-currents A negative feedback circuit is formed by the conversion means, the second resistor, the voltage detector, the voltage shift circuit, the voltage comparator, the power supply voltage control device, and the power supply terminal, and an input terminal pair of the voltage comparator. Wherein the voltage difference between the terminals is converged to zero.