JPS58107921A - Current supply device - Google Patents

Abstract

PURPOSE:To attain excellent limit characteristics against ambient temperature change and to prevent the deterioration in the rate of utilization of a power supply voltage, by limiting a bias of an input of a transistor (TR) connected in series with a load to the power supply by means of a comparison means. CONSTITUTION:TRs 2 and 8 are formed on an IC chip and the emitter area of the TR2 is 100 times that of the TR8. When IM>100I0 is established where IM is a current flowing to a DC motor 3 which is load and I0 is an output current of a constant current source 9, the potential of an inverting input 10a of a comparator 10 is higher than the potential of a non-inverting input 10b and a current supplied from a bias supply means 7 is absorbed in an output 10c, then the emitter current of the TR2 rapidly decreases. Since balancing is kept when the IM is equal to 100I0, the IM is made dependent on the I0.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a current supply device having an output current limiting function, and provides a current supply device having an extremely simple configuration and excellent limiting characteristics.

Conventionally well known devices of this type include, for example, T
,n,s,Hainilton: Handbook
oflinaar integrated elec
tronics forresearch” McG
RAW-HILL Book Company (UK
) Lim1ted, London (1977
) (7) As shown on page 318, a method often used is to insert a current detection resistor in series with the load and apply the voltage generated across this detection resistor between the base and emitter of the detection transistor. Ta.

However, as is well known, the knee voltage between the base and emitter of a bipolar transistor has a negative temperature coefficient of around 2 m170, and if the current detection resistor is also configured on the step of a monolithic IC, the I (The resistance value of the diffused resistor in 3 is generally 20
001) Since it has a positive temperature coefficient of about pm, the overall limit current value is 60o.

It has a negative temperature coefficient of about ppm, for example, the limiting current value 'i
Even if it is set for one person at 20℃, the temperature will rise to 120℃.
In this case, the value was 0.6A, which caused many problems.

Furthermore, when a current detection resistor is inserted in series with the load, there is a problem in that the power loss increases by that amount, and the utilization rate of the power supply voltage also deteriorates.

The current supply device of the present invention solves the above problems.

FIG. 1 shows a circuit connection diagram of a current supply device according to an embodiment of the present invention. In the figure, a DC motor 3, which is a load, is connected to both ends of a power supply 1 in series with the collector-emitter of a transistor 2.
A resistor 4 is connected between the base and emitter of the transistor 6, and the emitter of a transistor 6 is connected to the base of the resistor 4.

The collector of the transistor 6 is connected to the positive power supply line 1a via a resistor 6, and the transistor 6 is connected between the base of the transistor 5 and the positive power supply line 1a.

For example, a bias supply means element such as a variable resistor is connected.

On the other hand, the emitter of a transistor 8 is connected to the negative feed line 1b to which the emitter of the transistor 2 is connected, the base 1ri of the transistor 8 is connected to the collector, and there is a connection between the collector and the positive feed line 1a. A constant current source 9 is connected. Further, an inverting input terminal 10a of an oven collector output type comparator 1° is connected to the base of the transistor 2, and a non-inverting input terminal 10b of the comparator 1o is connected to the collector (base) of the transistor 8, and the same output terminal is connected to the base of the transistor 2. terminal 10
C is connected to the base of the transistor 5.

Now, in the circuit of FIG. 1, it is assumed that at least transistor 2 and transistor 8 are formed on the same IC chip, transistor 2 has an emitter area 100 times that of transistor 8, and constant current source 9 Let the output current of
Then, when 1,)100IO is established, the inverting input terminal 1 of the comparator 1o
The potential of the transistor 0a becomes higher than the potential of the non-inverting input terminal 10b, and the current supplied from the bias supply means 7 is absorbed by the output terminal 10C of the comparator 1o, so the emitter current of the transistor 2 decreases rapidly. do. In the end, balance is maintained with IM -100I□ established, so the load current 1
M depends on the output current Io of the constant current source 9.

In other words, by appropriately setting the output current Iok, it is possible to freely set the limit value of the load current. In the circuit shown in Figure 1, there is no current detection resistor connected in series with the load. There is no increase in power loss due to the current detection resistor, there is no deterioration in the utilization rate of the power supply voltage, and the temperature coefficient of the limiting current value can be made almost zero.

FIG. 2 shows another embodiment of the present invention. In FIG. 2, a constant voltage diode 11 and a transistor 120 forming a voltage stabilizing circuit are connected between the base of the transistor 5 and the negative feed line 1b. The base and emitter of the transistor 120 are connected in series, and a resistor 13 is connected between the base and emitter of the transistor 120.

Further, the constant voltage diode 11 and the transistor 6
The base of the transistor 14 is connected to the connection point of the base of the transistor 14, and the emitter of the transistor 14 is connected to the negative power supply line 1b via the resistor 16. .18 base.

The transistors 16, 17, and 18 constitute a current mirror circuit that uses the collector current of the transistor 14 as an input current, and the transistor 17 is used as a constant current source that supplies a constant current to the transistor 8. The transistor 18 is used as a constant current source that supplies a constant current to the voltage stabilizing circuit.

Further, the collector of the transistor 12 is connected to the positive power supply line 1a via a resistor 19, the base of the transistor 2o is connected to the collector, and the emitter of the transistor 2o is connected to the negative power supply line 1b. The collector is the transistor 16,1
It is connected to the common base of a current mirror circuit according to 7.18.

In the circuit shown in FIG. 2, a constant voltage determined by the terminal voltage of the constant voltage diode 11 is supplied to the DC motor 3, and a bias current value to the transistor 8 supplied by the constant current source 17 and the voltage between the transistor 8 and the transistor are supplied to the DC motor 3. The emitter area ratio of 2 has a function of preventing a current exceeding the limit current value from flowing to the load side.

In FIG. 2, the base-emitter junction of the transistor 12 is used for the purpose of canceling out the base-emitter junction of the transistor 14 so that the terminal voltage of the voltage regulator diode 11 appears as it is across the resistor 16. However, at the same time, the transistor 12 is connected to the resistor 19. Together with the transistor 2o, it constitutes a starting circuit for the current mirror circuit.

In other words, when the power supply voltage gradually increases from zero,
First, a base current flows through the transistor 20 via the resistor 19 to activate the current mirror circuit, and thereafter the transistor 14 becomes conductive.

When the power supply voltage further increases and current begins to flow through the constant voltage diode 11, the base current also begins to flow through the transistor 12, and from then on, the transistor 12 is turned on and the transistor 2o is turned off. .

By the way, in the embodiments of the present invention shown in FIGS. 1 and 2, a DC motor is connected as a load and a bipolar transistor is used for each transistor, but it is possible to connect a load other than the motor. Alternatively, the transistor may be a unipolar transistor such as an MO8 type FET. In that case, the base of the bipolar transistor as the input electrode corresponds to the gate of the unipolar transistor, and the collector of the bipolar transistor as the output electrode corresponds to the unipolar transistor. The drain of the unipolar transistor corresponds to the common electrode, and the emitter of the bipolar transistor corresponds to the source of the unipolar transistor.

FIG. 3 is a circuit wiring diagram showing another embodiment of the present invention constructed using enhancement type MOS transistors. In the same figure, N channel enhancement fi
MO8) A DC motor 3 as a load is connected between the drain of the transistor 101 and the positive feed line 1a, and a frequency generator (FG) is connected to the DC motor 3.
The output of 103 is applied to a rotational speed control circuit 107, and the output of the rotational speed control circuit 107 is applied to the gate of the N-channel enhancement transistor 101.

On the other hand, a drain current is supplied by a constant current source 109 to an N-channel enhancement type MOS transistor 108 whose source is connected to the negative side power supply line and whose gate is connected to the drain. shall be in oven collector or oven drain output format.

) is connected to the non-inverting input terminal 110b of the comparator 110, and the inverting input terminal 1101L of the comparator 110 and the output terminal 110b of the comparator 110 are connected to the gate of the Nf channel enhancement type MO8) transistor 101.

Note that the N-channel non-performance type MOS
) A resistor 10 is connected between the gate and source of the transistor 101.
4 is connected.

In FIG. 3, the rotational speed control circuit 107 controls the rotational speed [k
This circuit is for constant speed control to a predetermined value, and is for adjusting the amount of current flowing through the N-channel enhancement type MOS transistor 1 according to the magnitude of the load connected to the rotating shaft of the DC motor 3. It has the function of generating gate bias voltage.

The output current limiting operation in the circuit of FIG. 3 is the same as that of the circuit of FIG. 1, so a description thereof will be omitted here.

As described above, the current supply device of the present invention includes a first transistor (corresponding to 2, 101 in the above embodiment) connected in series with a load to a power supply, and an input electrode ( A bias supply means for supplying a bias current or a bias voltage for controlling the output current of the first transistor (corresponding to the seven-span rotational speed control circuit 107 of the above-mentioned embodiment), and a common electrode connected to the first transistor. a second transistor (8, 108 of the previous embodiment) connected to the common electrode of the transistor and whose input electrode is connected to the output electrode;
(equivalent to the constant current source 9 or the constant current source 109 or the transistor 17 in the above-described embodiment), a current supply means (equivalent to the constant current source 9 or the constant current source 109 or the transistor 17 in the above-described embodiment), which supplies a predetermined current to the output electrode of the second transistor; Comparison means for comparing the potential of the input electrode of the first transistor and the potential of the input electrode of the second transistor and limiting the bias amount of the input electrode of the first transistor so that the difference becomes zero (the above-mentioned Comparator 10 or 1 in the embodiment
10), which not only provides a current supply device with a simple configuration that has excellent limiting characteristics especially against changes in ambient temperature, but also makes it possible to utilize the power supply voltage. It has excellent effects such as no deterioration in rate.

[Brief explanation of the drawing]

1, 2, and 3 are circuit connection diagrams of the current supply device according to each embodiment of the present invention. ...Transistor, 3...DC motor (load), 7...
. . . Bias supply means, 9, 109 . . . Constant current source, 10, 110 . . . Comparator, 101.
108...H channel enhancement MO
8 type transistor, 1o7...Rotation speed control circuit. Name of agent: Patent attorney Toshio Nakao and 1 other person No. 1
Figure a Figure 2

Claims (1)

[Claims] (1) A first transistor connected in series with a load to a power supply, and supplying a bias current or bias voltage to an input electrode of the first transistor for controlling the output current of the first transistor. bias supply means, a second transistor whose common electrode is connected to the common electrode of the first transistor and whose input electrode is connected to the output electrode; current supplying means; and biasing the input electrode of the first transistor so that the potential of the input electrode of the first transistor and the potential of the input electrode of the second transistor are compared and the difference becomes zero. A current supply device comprising: comparison means for limiting the amount of current, and configured to supply current to a load from an output electrode or a common electrode of the first transistor. (2. In the description of claim (1), the first and second transistors are bipolar transistors, and a voltage is connected between the base of the first transistor and the emitter side power supply line. A current supply device characterized in that the bias supply means is constituted by a stabilizing circuit and a constant current transistor that supplies a constant current to the voltage stabilizing circuit.