JP2002244746A - Power supply device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a power supply device capable of controlling current restriction of an output current supplied to a load in cases of a load discharge current and a load absorption current separately. SOLUTION: This power supply device is provided with a resistor 3C for detecting current IQ supplied to the load 7, a differential amplifier amplifying a potential difference between the resistors 3C, and a PNP transistor 5 to monitor a direction of a current flowing into the load 7 from an operational amplifier 4A, control a current restriction adjusting terminal A that the operational amplifier 4A has, and perform individual restriction in the discharge current and the absorption current.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a power supply device used in an integrated circuit measuring device and the like.

[0002]

2. Description of the Related Art FIG.
Shown in In FIG. 2, 1 is a CPU (central processing unit) and 2 is D /
A converter 3 is a resistor, 4 is an operational amplifier, and 7 is a load (such as an input / output terminal of a semiconductor device). CPU1 is D
The D / A converter 2 is connected to the negative input terminal of the operational amplifier 4A via the resistor 3A. The positive input terminal of the operational amplifier 4A is connected to GND (ground potential), and the output terminal of the operational amplifier 4A is connected to a load 7
Is connected to

The load 7 is connected to a negative input terminal of an operational amplifier 4A via a feedback resistor 3B. This allows
In the operational amplifier 4A, a negative feedback closed loop is formed between the output terminal and the negative input terminal via the feedback resistor 3B. The operational amplifier 4A has a current limit adjustment terminal A
, And one end of the resistor 3D is connected to the terminal A thereof. Further, the other end of the resistor 3D is connected to a negative power supply terminal of a predetermined voltage.

Next, the operation of the conventional power supply device will be described with reference to FIG. The function of this power supply device is to apply an input voltage VIN specified by the CPU 1 to the load 7, supply an electric current required by the load 7 in accordance with the input voltage from the operational amplifier 4A, and output the output of the operational amplifier 4A. And a current limiting operation for limiting the current IO. First, an operation of supplying a current to the load 7 with respect to the setting of the input voltage VIN will be described.

The CPU 1 receives an external circuit (not shown)
A digital signal corresponding to the input voltage VIN is set. As a result, the CPU 1 outputs the input digital signal to the D / A converter 2A. And D / A
The converter 2A converts this digital signal into an input voltage VIN having an analog value.

Next, the operational amplifier 4A applies the input voltage V
When IN is input, the signal is amplified to the output voltage VO applied to the electric charge 7. Then, the output voltage VO is set to the load 7,
The operational amplifier 4A outputs the output voltage required by the load 7 (in other words, the input voltage V
The current IO required to maintain the value of IN is supplied.

The voltage value of the input voltage VIN from the CPU 1 is Vin, the resistance value of the resistor 3A is R1, and the feedback resistor 3B is R
When the value is set to 2, the voltage value Vo of the output voltage VO given to the load has a relationship of Vo = − (R2 / R1) · Vin by the negative feedback closed loop, and the voltage value Vo of the output voltage VO is the input voltage It is determined by the voltage value Vin of VIN.

Next, the operation of limiting the output current IO will be described. The operational amplifier 4A is provided with a current limit adjustment terminal A. Based on the voltage value VB of the negative power supply B that supplies a negative voltage and the resistance value RD of the resistor 3D, the current limit IA of the operational amplifier 4A is adjusted. Decided. Here, assuming that the voltage value VA of the current limit adjustment terminal A is the current limit adjustment terminal A
Is the current value of the limiting current IA flowing through the following equation: Ia = (VA−VB) / RD

The current value Io of the output current IO of the operational amplifier 4A and the current value Ia of the limit current IA flowing to the current limit adjustment terminal A have a relationship of Io = G · Ia. Here, G is a current amplification factor determined for each operational amplifier 4A. And the operational amplifier 4A
Restricts the output current IO to the load 7 based on the above-mentioned limiting current IA. This limitation of the output current IO depends only on the resistance value RD of the resistor 3D.

In the conventional power supply device, the current value Io of the output current IO flowing from the operational amplifier 4A to the load 7 is determined by the state of the load 7. The current value Io of the output current IO is limited by the discharge current (Io>
0) and the sink current (Io <0), the operation is performed based on exactly the same conditions as described above.

[0011]

SUMMARY OF THE INVENTION In a conventional power supply,
The limiting current IA is set from the CPU 1 to the operational amplifier 4A by using the resistor 3D as a variable resistor and setting the value of the resistance value RD, thereby limiting the current value of the output current IO of the operational amplifier 4A. However, the current limit of the output current IO is the same in both the discharge current and the sink current.

For this reason, in the conventional power supply device, when the numerical values of the discharge current and the sink current are different depending on the type of the load 7, it is necessary to supply an excessively limited current to the negative power supply B in one of the cases. Therefore, there may be a case where it is desired that the limiting current of the discharging current and the limiting current of the sink current be individually limited. However, in this case, if two operational amplifiers 4A are provided and each of them is used separately for a source current and a sink current, the operation of the two operational amplifiers 4A is avoided in order to avoid an overcurrent interruption due to an electrical short circuit. Since it is necessary to prepare only one operational amplifier 4A as the same power supply for the positive power supply and the negative power supply supplied to the amplifier 4A, it is difficult to individually limit the discharge current and the sink current. .

The present invention has been made in view of such a background, and provides a power supply device capable of separately controlling a current limit when an output current supplied to a load is a source current and a sink current of the load. To do.

[0014]

A power supply device according to the present invention converts a digital value indicating a voltage supplied to a load into a voltage value of an analog value (D / A converter 2).
An amplification circuit (operational amplifier 4A) for amplifying the voltage value and supplying the amplified current value to a load; and switching a magnitude of a limit current provided at a current limit adjustment terminal of the amplifier circuit for controlling an output current of the amplifier circuit. It is characterized by comprising a limiting current switching circuit, and a switching control circuit (differential amplifier H) for outputting a switching signal for switching the limiting current.

The power supply device according to the present invention is characterized in that the switching control circuit outputs the switching signal according to the polarity of the output current supplied from the amplifier circuit to the load. The power supply device according to the present invention determines whether or not the limited current switching circuit allows a current to flow through a predetermined adjustment resistor (resistance 3E) in a parallel resistor inserted between the amplifier circuit and a predetermined voltage. The magnitude of the limiting current is switched by controlling based on a switching signal.

In the power supply device according to the present invention, in the limiting current switching circuit, a diode (diode 6) having an anode connected to the current limiting adjusting terminal is provided in series with the adjusting resistor, and a PNP transistor (P
The collector of the NP transistor is connected between the cathode of the diode and the adjusting resistor, and when the PNP transistor is ON, a current flows through the adjusting resistor, and
When the P-transistor is OFF, no current flows into the adjustment resistor.

In the power supply device according to the present invention, the switching control circuit is constituted by a differential amplifier circuit, and based on the polarity of the output current, a switching signal which is either positive or negative for turning on / off the PNP transistor. Is output.

In order to solve the above-mentioned problem, in the power supply of the present invention, the current supplied to the load 7 can be set separately for the discharge current and the sink current. In the power supply device of the present invention, the current mainly flowing from the operational amplifier 4A to the load 7 is focused on only when the current is a sink current. Only when the current flowing from the operational amplifier 4A to the load 7 is the discharge current is the same performance as the conventional device, and the output current IO is limited by the current value of the limited current IA + IB.

In the case of the sink current, the output current is more strictly limited than the discharge current, and the current flowing to the negative power supply is further limited. That is, by reducing the current flowing from the operational amplifier 4A to the negative power supply B and using only the limiting current IA, an unnecessary limiting current is reduced, and the power consumption of the negative power supply B itself is reduced.
In order to realize this, a differential amplifier is composed of a resistor 3C for detecting the current IO supplied to the load 7, an operational amplifier 4B for amplifying the potential difference, and other resistors in the conventional device. By providing a device for driving the PNP transistor 5, a device for newly limiting the sink current is realized.

[0020]

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 power supply circuit according to one embodiment of the present invention. In this figure, 3C is a detection resistor, 3E, 3F, 3G, 3H,
3I is a resistor, 4B is an operational amplifier, 5 is a PNP transistor, and 6 is a diode. The same components as those in the conventional example of FIG. 3 are denoted by the same reference numerals, and description thereof is omitted.

One end of the detection resistor 3C is connected to an operational amplifier 4A.
Is connected to one end of a resistor 3H and the other end is connected to one end of a load 7 and one end of a resistor 3I. here,
The operational amplifier 4A has a positive input terminal grounded. The other end of the resistor 3H is connected to the positive input terminal of the operational amplifier 4B and one end of the resistor 3G. The other end of the resistor 3G is
Grounded to GND.

The other end of the resistor 3I is connected to the negative input terminal of the operational amplifier 4B and one end of the resistor 3F. The other end of the resistor 3F is connected to the output terminal of the operational amplifier 4B and the PNP
Connected to the base terminal of transistor 5.

The PNP transistor 5 has an emitter terminal connected to GND, and a collector terminal connected to the cathode of the diode 6 and one end of the resistor 3E. here,
The diode 6 and the resistor 3E are connected in series, and provided between the negative power supply B and the current limit adjustment terminal A in parallel with the resistor 3D. The anode of the diode 6 is connected to the current limit adjustment terminal A of the operational amplifier 4A, and is further connected to one end of the resistor 3D. The other end of the resistor 3E
Connected to negative power supply B.

Hereinafter, an operation example of the power supply device according to the present invention will be described with reference to FIG. When the output current IO flows from the operational amplifier 4A to the load 7, a potential difference "V1-V2" is generated between both ends of the detection resistor 3C. The operational amplifier 4B monitors the polarity of the current value Io of the output current IO based on the potential difference “V1-V2”. This potential difference is determined by the operational amplifier 4B,
The signal is amplified by a differential amplifier H including resistors 3F, 3G, 3H, and 3I.

The output voltage value of the operational amplifier 4B is Vc,
Assuming that the resistance values of the resistors 3F, 3G, 3H, 3H, and 3I are RF, RG, RH, and RI, respectively, the operational amplifier 4B
Is the output voltage value Vc = ((RI + RF) / (RH + RG)). (RG /
RI) .V1- (RF / RI) .V2.

In the above equation, the resistance value 3F and the resistance value 3G,
Assuming that the relationship between the resistance 3H and the resistance 3I is RF = RG, RH = RI, the output voltage Vc is Vc = (RF / RI) · (V1−V2). As in the above equation, the potential difference between the detection resistors 3C “V1
−V2 ”determines the polarity of the detected output voltage Vc.

When the output current IO flowing from the operational amplifier 4A to the load 7 is a discharge current (Io> 0), the potential difference between the detection resistors 3C becomes V1-V2> 0, and the operational amplifier 4A
Since the output voltage of B becomes a positive voltage, the PNP transistor 5
Is off (OFF). At this time, the current IB having the current value Ib flows through the diode 6 in the forward bias direction, and flows into the negative power supply B via the resistor 3E.

That is, the limiting current flowing to the current limiting adjusting terminal A is the current IA of the current value Ia flowing through the resistor 3D
And the current “IA” obtained by adding the respective current values of the above current IB.
+ IB ". The current value of the limiting current IA + IB at that time is as follows, where VA is the voltage of the current limiting adjustment terminal A of the operational amplifier 4A, and VD is the forward voltage of the diode 6. Ia + Ib = (VA-VB) / RD + (VA-VD-V
B) / RE.

For this reason, the output current IO is limited by the limiting current IA and the current IB, and the current value Io of the output current IO is
G · (Ia + Ib). As a result, the output current IO
Is positive, the limit current flowing to the current limit adjustment terminal A for controlling the output current of the operational amplifier 4A can be set larger than when the polarity of the output current IO is negative. The output current of the amplifier 4A can have a large IO value.

When the output current IO flowing from the operational amplifier 4A to the load 7 is a sink current (Io <0), the detection resistor 3
The potential difference between C becomes V1−V2 <0, and the operational amplifier 4B
Is a negative voltage, the PNP transistor 5 is turned on. At this time, conduction between the negative power supply B and GND is conducted through the resistor 3E and the collector-emitter of the PNP transistor 5, and a current IC flows from the GND to the negative power supply B due to the potential difference.

At this time, when the current IC flows through the resistor 3E, the voltage on the cathode side of the diode 6 increases due to the voltage drop due to the current IC, and the diode 6 becomes reverse biased and the current I
B stops flowing, and the current value Ib becomes “0”. Therefore, the current flowing through the negative power supply B is the current “IA + IC”. However, the limiting current flowing through the current limiting adjusting terminal A of the operational amplifier 4A is the current IB via the diode 6.
Does not flow, and the current IC does not affect the operational amplifier 4A, so that only the current IA is provided.

For this reason, the output current IO is limited only by the limiting current IA, and the current value Io of the output current IO is G · Ia
Becomes Thereby, when the polarity of the output current IO is negative, the limit current flowing to the current limit adjustment terminal A for controlling the output current of the operational amplifier 4A is set smaller than when the polarity of the output current IO is positive. Therefore, the output current of the operational amplifier 4A can be limited to a small value of IO.

In the power supply device of the present invention, the output current IO flowing from the operational amplifier 4A to the load 7 is
Is determined by the state of the load 7. However, the limitation of the current value Io of the output current IO is, for example,
The ON / OFF of the PNP transistor 5 in each case of the source current for which the current value Io needs to be set large and the sink current for which the current value Io needs to be set small.
The operation controls (switches) whether or not the current IB flows through the resistor 3E using the current IC that flows from the PNP transistor 5 into the resistor 3E (adjustment resistor) as a switching signal, thereby switching the source current and the sink current. Can be separately controlled to a predetermined magnitude.

As described above, one embodiment of the present invention has been described in detail with reference to the drawings. However, the specific configuration is not limited to this embodiment, and a design change or the like may be made without departing from the gist of the present invention. The present invention is also included in the present invention.

[0035]

As described above, in the power supply device according to the present invention, the output current IO supplied from the operational amplifier 4A to the load 7 is different from the source current and the sink current. Since the control is enabled and the limiting current corresponding to each case is caused to flow, unnecessary current is not flown to the negative power supply B, and the power consumption in the power supply device is reduced.

[0036]

[Brief description of the drawings]

FIG. 1 is a block diagram illustrating a configuration example of a power supply device according to an embodiment of the present invention.

FIG. 2 is a block diagram illustrating a configuration of a power supply device according to a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 CPU 2 D / A converter 3A, 3B resistor 3C Detection resistor 3E, 3F, 3G, 3H, 3I Resistor 4A-4B Operational amplifier 5 PNP transistor 6 Diode 7 Load

Continuation of the front page F term (reference) 5H410 BB04 BB05 CC02 DD02 EA12 EB14 EB25 EB37 FF03 FF05 FF25 GG07 JJ03 LL05 LL19 5H420 BB12 BB13 CC02 DD02 EA19 EA23 EB15 EB26 EB37 FF03 FF04 NB25 NC22 NC22

Claims (5)

[Claims] 1. A D / A converter for converting a digital value indicating a voltage supplied to a load to a voltage value of an analog value, an amplifier circuit for amplifying the voltage value and supplying the voltage value to a load, A limiting current switching circuit that is provided at a current limiting adjusting terminal and switches a magnitude of a limiting current that controls an output current of the amplifier circuit; and a switching control circuit that outputs a switching signal that causes the limiting current switching circuit to switch the limiting current. A power supply device comprising: 2. The power supply device according to claim 1, wherein said switching control circuit outputs said switching signal in accordance with the polarity of an output current supplied from an amplifier circuit to a load. 3. The control circuit according to claim 2, wherein the limiting current switching circuit controls whether or not to supply a current to a predetermined adjusting resistor of a parallel resistor inserted between the amplifier circuit and a predetermined voltage based on the switching signal. The power supply device according to claim 1, wherein the magnitude of the limiting current is switched. 4. A limiting current switching circuit, wherein a diode having an anode connected to the current limiting adjusting terminal is provided in series with the adjusting resistor, and a collector of the PNP transistor is connected to a cathode of the diode and the adjusting resistor. And this PNP transistor is ON
4. The power supply circuit according to claim 1, wherein a current is supplied to the adjustment resistor when the PNP transistor is OFF, and no current is supplied to the adjustment resistor when the PNP transistor is OFF. 5. The switching control circuit according to claim 1, wherein the switching control circuit comprises a differential amplifier circuit, and the switching control circuit includes a PNP based on a polarity of the output current.
The power supply circuit according to any one of claims 1 to 4, wherein the power supply circuit outputs a switching signal that is either positive or negative voltage for turning on / off the transistor.