KR19980040712A - Power control circuit using sense transistor - Google Patents

Abstract

The present invention is to provide a power control circuit using a sense transistor. The circuit includes n diodes and first resistors connected in series between a reference voltage and a ground voltage, a transistor for mirroring the current flowing to the n diodes, a second resistor connected in series with the transistor, A comparator having a negative input terminal to which a voltage across the second resistor is applied and a positive input terminal to which a sense voltage is applied; An inductor having one side connected to a voltage, a gate electrode to which an output signal of the pulse width modulation controller is applied, a drain electrode connected to the other side of the inductor, and a ground voltage A sense electrode having a Kelvin electrode and a sense electrode connected in common to a connected source electrode Connected between the registers, and the sense electrode and the ground electrode of the sense transistor is composed of a sense resistor to generate a sense voltage at all times.

Description

Power control circuit using sense transistor

The present invention relates to a power control circuit using a sense transistor, and more particularly to a temperature-compensated current source of a power control circuit using a sense transistor.

When the current sensing terminal of the sense transistor is embedded in the integrated circuit in the two-chip one-package product of the sense transistor and the control integrated circuit, the current ratio temperature characteristic of the sense transistor differs greatly according to the circuit characteristic of the current sensing terminal . In MOS transistors, this characteristic does not appear. In this case, the current control characteristic is related only within the integrated circuit. That is, there is a problem that the temperature change rate of the current of the current sensing stage of the power control circuit using the conventional sense transistor and the temperature change rate of the sensing current of the sense transistor are different.

An object of the present invention is to provide a power control circuit using a sense transistor capable of minimizing a temperature change rate of a maximum current with respect to a temperature change during current control of a two-chip one package using a sense transistor.

In order to achieve the above object, a power control circuit using a sense transistor of the present invention includes n diodes and first resistors connected in series between a reference voltage and a ground voltage, a transistor for mirroring the current flowing through the n diodes, A second resistor connected in series with the transistor, a feedback voltage means connected to a common point of the transistor and the second resistor for controlling a voltage across the second resistor, a negative input terminal to which a voltage across the second resistor is applied, A comparator having a positive input terminal to which a sense voltage is applied, a pulse width modulation controller for inputting the output signal of the comparator to modulate the pulse width, an inductor having one side connected to the voltage, A gate electrode, a drain electrode connected to the other side of the inductor, Is connected between the source electrode connected to the common electrode and the associated Kelvin sense electrode and ground electrode of the sense transistor and the sense transistor having a sense electrode is characterized in that it includes a sense resistor to generate a sense voltage at all times.

1 is a circuit diagram of a power control circuit using a sense transistor of the present invention.

Fig. 2 is a waveform diagram of each output of the circuit shown in Fig. 1. Fig.

3 is a graph showing a change in current (is) with respect to temperature.

Hereinafter, a power control circuit using the sense transistor of the present invention will be described with reference to the accompanying drawings.

1 is a circuit diagram of a power control circuit using a sense transistor according to the present invention. The power control circuit includes n diodes D1, D2, ..., Dn and resistors Ri, Ra connected in series between a power supply voltage and a ground voltage, A negative input terminal to which the voltage V1 of the resistor R1 is applied and a negative input terminal to which the sense voltage V1 is applied are connected to the collector of the PNP transistor and the ground voltage, A pulse width modulation controller 20 for inputting the output signal of the comparator 10 to modulate the pulse width, a inductor having one side connected to the voltage V _DC , (L), a gate electrode to which the output signal of the pulse width modulation controller 20 is applied, a drain electrode connected to the other side of the inductor L and a source electrode connected to the ground voltage, and a sense transistor 30), and sense transistor A resistor Rs connected between the sense electrode of the stamper 30 and the ground electrode, a resistor Rb and a diode D connected in series between the feedback voltage Vfb and the ground voltage and a resistor Rb and a diode D, And a transistor Q2 having a collector connected to the common point of the resistor R1 and a collector of the PNP transistor Q1 and an emitter connected to the ground voltage.

Fig. 2 is a waveform diagram of each output of the circuit shown in Fig. 1. The operation of the circuit shown in Fig. 1 will be described with reference to Fig.

The pulse width modulation controller 20 responds to the internal frequency clock signal CK so that the sense transistor 30 is charged and discharged to the voltage V1 as indicated by the voltage Vs in Fig. The comparator 10 generates the pulse signal A when the voltage V1 across the resistors Ri and Rb becomes equal to the voltage Vs across the resistor Rs. The pulse width modulation controller 20 generates a pulse signal that rises at the time of generation of the clock signal CK and falls at the time of generation of the signal A. [

The current i1 is a current controlled by the feedback voltage Vfb and the peak current of the current (ids) flowing through the source electrode of the sense transistor 30 is determined as follows. When the maximum value of the current i1 is multiplied by the resistor R1 and the voltage V1 is generated, the time when the voltage V1 becomes equal to the voltage Vs becomes the maximum value of the current ids. The current (ids) is denoted by n x is, where n is the current ratio of the sense transistor. V1 = Vs, i1 x R1 = is x Rs.

When the current ids is controlled to be constant by the characteristics of the sense transistor 30, the current ratio n varies depending on a certain value of the resistor Rs. When the resistance Rs has a temperature function, the current ratio of the sense transistor 30 also exhibits a constant temperature function of any value.

FIG. 3 is a graph showing the rate of change of the current (is) when the current (ids) is kept constant with respect to the temperature change according to the resultant waveform. The current (i1) ) Is made equal to the temperature change of the current (is). Therefore, if the temperature change rate of the current (is) is 20%, the temperature change rate of the current (ids) becomes almost 0 when the temperature change rate of the current (i1) is taken as 20%.

The circuit shown in Fig. 1 detects the temperature change rate of the current i1 ) Can be simply designed and compensated.

The temperature coefficient of the diodes D1, D2, ..., Dn and the resistors Ri, Ra is combined to be adjustable to a positive or negative value. The temperature coefficients of the resistors Ri and Ra are different from each other.

The values of the current i1 and the current i2 are the same when the diode D1 and the PNP transistor Q1 have the same size. Thus, the rate of temperature change with respect to the current i2 ).

......(One)

......(2)

In Equation (1), n represents the number of the diodes and the voltage V2 represents the voltage across the resistors Ri and Ra.

The above equation (1) is differentiated as follows.

(3)

In equation (3) .

That is, it is assumed that the reference voltage Vref has no variation with respect to the temperature change.

Therefore, it is expressed by the following equation (4).

......(4)

The differential equation (2) is expressed by the following equation (5).

(5)

In equation (5) (6) below.

(6)

Therefore, the temperature change rate of the current i1 is represented by the following equation (7).

(7)

In equation (7) , , Is a set of values, and these values are represented by the constants a, b, and c, respectively, and are simply expressed by the following equation (8).

......(8)

As can be seen from the equation (8), the temperature change rate of the current i2 can be adjusted by adjusting the number of the diodes and the values of the resistors Ri and Rb, and the current i1 ) Is changed. That is, it becomes possible by adjusting the current i2 so that the rate of temperature change of the current i1 becomes equal to the rate of temperature change of the current is.

The voltage V1 is controllable by the current ifb which varies with the feedback voltage Vfb. Assuming that the diode D and the NPN transistor Q2 are composed of the same transistor, the current (ifb) , And the voltage V1 is represented by Lt; / RTI > Therefore, the value of the voltage V1 is controllable by the feedback voltage Vfb.

As a result, it is possible to make the rate of temperature change of current i1 equal to the rate of temperature change of current is by adjusting the number of diodes and the values of resistors Ri and Ra, and the voltage V1 and the sense voltage Vs can be made equal to each other by adjusting the feedback voltage Vfb.

Therefore, the maximum current of the current (ids) can be prevented from varying with temperature by designing the same as the rate of temperature change of the current (is) of the current (i1) .

The power control circuit using the sense transistor of the present invention can minimize the temperature change rate of the maximum current with respect to the temperature change in the current control of the two-chip one package using the sense transistor.

Claims (4)

A first resistor connected in series between the reference voltage and the ground voltage and first resistors, a transistor for mirroring a current flowing through the n diodes, a second resistor connected in series with the transistor, a voltage across the second resistor, A feedback voltage means connected to a common point of the transistor and the second resistor for controlling the output of the comparator, a comparator having a negative input terminal to which a voltage across the second resistor is applied and a positive input terminal to which a sense voltage is applied, A gate electrode to which an output signal of the pulse width modulation controller is applied, a drain electrode connected to the other side of the inductor, and a source electrode connected to a ground voltage. The pulse width modulation controller includes: A sense transistor having a Kelvin electrode and a sense electrode connected in common, And a sense resistor connected between the sense electrode of the sense transistor and the ground electrode to generate a constant sense voltage. 2. The method of claim 1, wherein the value of n and the value of the first resistors are varied to equalize a rate of temperature change between a current flowing through the sense resistor and a current flowing through the transistor. Control circuit. The power control circuit according to claim 1, wherein a temperature coefficient of the first resistors is different from that of the first resistors. 2. The semiconductor device of claim 1 wherein the feedback voltage means comprises a third resistor and a second diode connected in series between a feedback voltage and a ground voltage and an emitter coupled to a base and a ground voltage coupled to a common point of the third resistor and the second diode, And an NPN transistor having a collector connected to a common point of the transistor and the second resistor.