JPH0150925B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a power supply device for semiconductors that are easily destroyed by overvoltage, such as laser diodes and InSb Hall elements, and has an extremely simple configuration.
Moreover, it provides a circuit configuration suitable for monolithic IC implementation.

Conventionally, for example, in brushless motor drive circuits that use InSb Hall elements as rotor rotational position detection elements, it has been found that applying a constant voltage to the Hall elements provides more favorable output characteristics against changes in ambient temperature. Therefore, a simple power supply circuit as shown by the broken line in FIG. 1 was constructed inside the monolithic IC constituting the drive circuit.

In FIG. 1, 1 is a Hall element, 2 is a bias power supply for the entire circuit, and 3 is a stabilized power supply for determining the voltage applied to the Hall element 1. Originally, the power supply 2 was If the power source 2 and the power source 3 are stabilized, the power source 2 and the power source 3 are operated, but if the power source 2 is not stabilized, a dedicated external power source is used or is generated inside the IC 100A.

The output voltage of the power supply 3 is divided by the resistors 4 and 5, and on the other hand, the voltage between the base and emitter of the transistor 6 inside the IC 100A and the forward voltage of the diode 7 cancel each other out, so that the input voltage is not input to the output terminal b. The same voltage appears at terminal c.

There are two reasons why a feedback type constant voltage circuit equipped with an error amplifier is not used in this type of power supply circuit.

Firstly, feedback-type constant voltage circuits have a large number of elements, which increases the chip size of the IC, which is an inconvenience.Secondly, feedback-type constant voltage circuits tend to cause high-frequency oscillations. This is because a capacitor is required to prevent this.

By the way, in the circuit shown in Figure 1, if resistors 4 or 5 with different resistance values are installed at the factory, or if the resistor 5 is not inserted properly, an unexpected voltage will be applied to the Hall element 1. As a result, there was a problem in that an excessive voltage was applied and the Hall element was destroyed.

The present invention solves the above-mentioned problems by providing an emitter follower type power supply circuit with a protection function for protecting the load from application of overvoltage. FIG. 2 is a circuit diagram showing one embodiment of the present invention. In FIG. 2, inside the IC 100B, there is an NPN transistor 60 that receives power from the collector side via a current limiting resistor 9 and supplies power to the Hall element 1 from the emitter side, and supplies a bias current to the base of the NPN transistor 60. a current supply circuit 80 for and a line from the current supply circuit 80 to the base of the NPN transistor 60;
Specifically, a PNP transistor 7 has an emitter connected to a connection point between a diode 10 for adjusting the maximum output voltage and the base of the NPN transistor 60, and a collector connected to a negative power supply line d.
0 (darlington connected like the NPN transistor 60) and the line from the current supply circuit 80 to the base of the NPN transistor, specifically the anode side of the diode 10 and the negative side feed line d. The structure includes a constant voltage diode 11 connected between them.

Further, the output voltage of the constant voltage power supply 3 is divided by a voltage dividing circuit 90 constituted by a resistor 4 and a resistor 5, and further connected to the PNP via an input terminal c.
It is applied to the base of transistor 70.

In the configuration shown in Figure 2, 2.5V is applied to output terminal b.
The resistance ratio of resistor 4 and resistor 5 is determined so that an output voltage of approximately
A material with a breakdown voltage of around 6V is used.

In this state, when the resistors 4 and 5 are of the normal resistance value, the output voltage is of course 2.5V, and the base-emitter voltage of the transistor and the forward voltage of the diode are both approximately Since the voltage is 0.7V, the potential on the anode side of the diode 10 is 4.6V, and no current flows through the voltage regulator diode 11, so no power loss occurs due to the addition of the voltage regulator diode.

On the other hand, if the resistor 5 is connected, a current flows through the voltage regulator diode 11, and the diode 10
The potential on the anode side of is clamped to around 6V by the voltage regulator diode.

At this time, the voltage appearing at the output terminal b is around 4V, which is less than twice the normal value.

InSb Hall elements will not be destroyed unless used for a very long period of time at a voltage less than twice the rated value.

Therefore, the circuit shown in FIG. 2 has a protection function against the application of overvoltage to the load, and there is no increase in current consumption due to the provision of the protection function.

Note that the semiconductor element connected as a load is
It is not limited to InSb Hall elements, but may also be laser diodes or other semiconductor elements that require similar protection.

Further, in FIG. 2, the current supply circuit 80 may be other current supply means such as a resistor,
NPN transistor 60, PNP transistor 70
does not necessarily need to be connected in a Darlington manner, and if a higher maximum output voltage is acceptable, the diode 10 can be omitted.

As described above, the power supply device of the present invention is an NPN that receives power from the collector side and supplies power to the load from the emitter side.
A transistor 60, a current supply means (corresponding to the current supply circuit 80) for supplying a bias current to the base of the NPN transistor, an emitter connected to a line from the current supply means to the base of the NPN transistor, and a collector connected to the base of the NPN transistor. A PNP transistor 70 connected to the negative feed line,
Voltage dividing means (corresponding to the voltage dividing circuit 90) that divides the voltage at a constant potential point (stabilized voltage) and applies it to the base of the PNP transistor, and a line from the current supply means to the base of the NPN transistor. and a voltage regulator diode 11 connected between the voltage dividing means and the negative power supply line, and when the division ratio of the voltage dividing means is incorrectly set, the output voltage is clamped by the voltage regulator diode, and no overvoltage is supplied to the load. In addition to configuring the
The device is characterized in that the division ratio is set so that no current flows through the constant voltage diode during normal operation.As a result, the circuit configuration is extremely simple, and the protection function against overvoltage can be achieved without increasing current consumption. For example, it is possible to have
It has a great effect.

[Brief explanation of drawings]

FIG. 1 is a circuit connection diagram showing a conventional example, and FIG. 2 is a circuit connection diagram showing an embodiment of the present invention. 1... Hall element (load), 2, 3... Power supply,
11... Constant voltage diode, 60... NPN transistor, 70... PNP transistor, 80...
...Current supply circuit, 90...Voltage division circuit, 100
B...IC.

Claims (1)

[Claims] 1. An NPN transistor that receives power from the collector side and supplies power to the load from the emitter side, a current supply means for supplying a bias current to the base of the NPN transistor, and an emitter on a line from the current supply means to the base of the NPN transistor. A connected PNP transistor, voltage dividing means for dividing a voltage at a constant potential point and applying it to the base of the PNP transistor,
A constant voltage diode is connected between the line leading to the base of the NPN transistor and the negative power supply line, and when the division ratio of the voltage dividing means is set incorrectly, the output voltage is clamped by the constant voltage diode. A power supply device characterized in that the power supply device is configured so that no overvoltage is supplied to the load, and the division ratio of the voltage dividing means is set so that no current flows through the constant voltage diode during normal operation.