JPH04255495A - Bridge type power-driven integrated circuit - Google Patents

Abstract

PURPOSE:To provide a bridge type power-driven integrated circuit in which the base current of a transistor for driving load is not affected by a power supply voltage for driving load. CONSTITUTION:This bridge type power-driven integrated circuit is constituted by connecting a constant-current circuit constituted of a current mirror circuit composed of NPN type transistors Q2 and Q20 (Q7 and Q70) between the base of a PNP bipolar transistor Q3 (Q5) for driving load and the base of an NPN bipolar transistor Q4 (Q6) for driving load. The base current of the transistors Q3 and Q4 (Q5 and Q6) hardly receive influences from a power supply voltage for driving load, since the constant current IS of the constant-current circuit is mirrored. Therefore, the tolerance of the power supply voltage for driving load can be expanded to the lower side.

Description

[Detailed description of the invention]

0001

[Field of Industrial Application] The present invention relates to a bridge-type power drive integrated circuit used for forward, reverse, and step drive of small motors for battery-operated devices such as optical cameras and video cameras. .

0002

2. Description of the Related Art The conventional bridge-type power drive integrated circuit described above will be explained with reference to the circuit diagram of FIG.

The bridge type power drive integrated circuit shown in FIG. 2 has a power supply terminal V connected to a load drive power supply (power supply voltage VCC) when the control input terminal IN1 is set to low (L) level.
When current is passed through CC, the load driving PNP transistor Q3, the motor winding L1, the load driving NPN transistor Q4, and the ground terminal GND to rotate the motor in the forward direction, and the control input terminal IN2 is set to low (L) level. to power supply terminal VC
C, the load driving PNP transistor Q5, the motor winding L1, the load driving NPN transistor Q6, and the ground terminal GND are configured to cause current to flow through them to reverse the motor.

Now, when the control input terminal IN1 is set to low (L) level in order to rotate the motor in the forward direction, the NPN transistor Q1 is turned off, the NPN transistor Q2 is turned on, and the base current of the PNP transistor Q3 is connected to the resistor R3. It passes through the NPN transistor Q2 and flows to the NPN transistor Q4. At this time, the base current flowing through the PNP transistor Q3 and the NPN transistor Q4 is determined by the value of the resistor R3. Also, the control input terminal IN1
When Q is set to high (H) level, the NPN transistor Q
1 is turned on, NPN type transistor Q2 is turned off, and PNP type transistor Q3 and NPN type transistor Q4 are turned off.

Furthermore, when the control input terminal IN2 is set to low (L) level in order to reverse the motor, the NPN transistor Q8 is turned off, the NPN transistor Q7 is turned on, and the base current of the PNP transistor Q5 is connected to the resistor R4 and the NPN transistor Q8. It passes through the NPN transistor Q7 and flows to the NPN transistor Q6. At this time, the base current flowing through the PNP transistor Q5 and the NPN transistor Q6 is determined by the value of the resistor R4. Also, control input terminal IN2
When set to high (H) level, the NPN transistor Q
8 is turned on, NPN type transistor Q7 is turned off, and PNP type transistor Q5 and NPN type transistor Q6 are turned off.

[0006]

However, in the conventional circuit described above, the base current flowing through the PNP transistor Q3 and the NPN transistor Q4 is determined by the value of the resistor R3. (The base current flowing through the transistor Q6 is determined by the value of the resistor R4.) Therefore, there was a problem in that the base current was affected by voltage fluctuations of the load driving power supply, and the base current was extremely reduced in the region where the power supply voltage VCC was low. .

The base current IB flowing through the PNP transistor Q3 and the NPN transistor Q4 is expressed as follows (1
) can be found using the formula. IB = (VCC-VBE*2-VCE)/R3...
(1) VBE is the base-emitter voltage of transistors Q3 and Q4, and VCE is the collector-emitter voltage of transistor Q2. For example, when the power supply voltage VCC becomes 3 volts or less, the base current IB drops extremely.

[0008] The present invention solves the above problems, and
It is an object of the present invention to provide a bridge type power drive integrated circuit in which the base current of a drive transistor for driving a load is not affected by the power supply voltage.

[0009]

[Means for Solving the Problems] In order to solve the above problems, a bridge type power drive integrated circuit of the present invention provides a load driving P
A bridge-type power drive integrated circuit composed of an NP-type bipolar transistor and a load-driving NPN-type bipolar transistor, wherein a constant current is configured by a current mirror circuit between the base of the PNP-type bipolar transistor and the base of the NPN-type bipolar transistor. It is characterized by connecting circuits.

0010

[Operation] With the above structure, the base current of the load driving bipolar transistor is hardly affected by the load driving power supply voltage because the constant current of the constant current circuit is mirrored. Therefore, the allowable range of the load driving power supply voltage can be expanded to a lower value.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to the drawings. Note that the same components as those in the conventional example shown in FIG.

FIG. 1 shows a bridge type power drive integrated circuit according to an embodiment of the present invention. On the motor forward rotation side, the conventional resistor R3 is removed, an NPN transistor Q20 is added, and the transistors Q2 and Q20 are used to mirror the current. The circuit is constructed such that a current IS flows through the current mirror circuit from a stabilized power supply input terminal VS connected to a stabilized power supply (power supply voltage VS) generated from a load driving power supply through a resistor R2. In addition, on the motor reverse side, the conventional resistor R4 is removed, an NPN transistor Q70 is added, a current mirror circuit is formed by the transistors Q7 and Q70, and a current IS is caused to flow from the stabilized power supply (power supply voltage VS) through the resistor R5. It is configured like this.

The operation of the above configuration will be explained below. To rotate the motor forward, control input terminal IN1 is set to low (
When the level is set to L), the NPN transistor Q1 is turned off, and a current IS flows from the stabilized power supply (power supply voltage VS) through the resistor R2 from the base-collector to the emitter of the NPN transistor Q20. At this time, since the transistors Q2 and Q20 constitute a current mirror circuit, a current IB proportional to the current IS flows through the collector of the transistor Q2. The ratio is transistor Q2, Q
It is determined by the area ratio of 20 emitters. In this embodiment, the emitter area of the transistor Q2 is 5 compared to the emitter area of 1 of the transistor Q20. The current IB becomes the base current of the load driving PNP transistor Q3, and the current IB joins the current IS to become the base current of the load driving NPN transistor Q4. Further, when the control input terminal IN1 is set to high (H) level, the NPN transistor Q1 is turned on, and the NPN transistor Q20 is turned on.
, Q2 are turned off, and the PNP transistors Q3, NP
N-type transistor Q4 is turned off.

Similarly, when the motor is reversed, when the control input terminal IN2 is set to a low (L) level, the NPN transistor Q8 is turned off, and the current IS flows from the stabilized power supply through the resistor R5 to the base of the NPN transistor Q70.
flows from the collector to the emitter, and at this time the transistor Q
7 and Q70 constitute a current mirror circuit, so a current IB proportional to the current IS flows through the collector of the transistor Q7. The ratio is determined by the area ratio of the emitters of transistors Q7 and Q70. In this embodiment, the emitter area of transistor Q70 is 1, while transistor Q70 is
The emitter area was set to 5. Current IB is load driving PN
This becomes the base current of the P-type transistor Q5, and the current I
B joins with the current IS to become the base current of the load driving NPN transistor Q6. Also, the control input terminal IN
2 is set to high (H) level, NPN transistor Q8 turns on, and NPN transistors Q70, Q7
is turned off, and the PNP type transistor Q5 and NPN type transistor Q6 are turned off.

In this way, the load driving PNP transistors Q3 and Q5 and the load driving NPN transistor Q4
, Q6 base currents IB, (IB+IS) can be set by the values of resistors R2 and R5, regardless of the power supply voltage VCC. Therefore, it is possible to respond to a drop in the power supply voltage VCC over a wide range, and the allowable range of the power supply voltage VCC can be set. Can be expanded lower.

[0016]

[Effects of the Invention] As described above, according to the present invention, the base current of the load driving bipolar transistor is almost unaffected by the load driving power supply voltage because the constant current of the constant current circuit is mirrored. Therefore, it is possible to cope with a drop in the power supply voltage for driving the load over a wide range, and the allowable range of the power supply voltage can be expanded to the lower side.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of a bridge type power drive integrated circuit in one embodiment of the present invention.

FIG. 2 is a circuit diagram of a conventional bridge-type power drive integrated circuit.

[Explanation of symbols]

L1 Motor winding VCC Power input terminal VS Stabilized power input terminal R2, R5 Current IS Setting resistor Q2, Q2
0, Q7, Q70 Transistors Q3, Q5 forming a current mirror PNP type bipolar transistors for load driving Q4, Q6 NPN type bipolar transistors for load driving IN1, IN2 Control input terminal GND Ground terminal

Claims (1)

[Claims] 1. A bridge type power drive integrated circuit comprising a PNP type bipolar transistor for driving a load and an NPN type bipolar transistor for driving the load, wherein the PNP type bipolar transistor
A bridge type power drive integrated circuit, characterized in that a constant current circuit constituted by a current mirror circuit is connected between the base of an NP type bipolar transistor and the base of the NPN type bipolar transistor.