JPS63299506A - Constant current drive circuit - Google Patents

Abstract

PURPOSE:To realize impression of the power supply voltage at the time of the maximum output and to improve the power supply avaiability as well as the power loss caused in an amplifier, by using the output of a differential amplifier for control of load current to vary the input reference potential up to the power supply voltage from 0V. CONSTITUTION:The joint between a load 1a and a current detecting resistance 2a is referred to as an (a) point 50a together with the other end of the load 1a as a (b) point 51a and the other end of the resistance 2a as a (c) point 52a respectively. Thus the point 51a is connected to the output 31a of a load current controlling differential amplifier (I amplifier) 3a. Then the point 52a is connected to the output 41a of an input reference voltage setting differential amplifier (V amplifier) 4a. The output of the amplifier 4a is decided by the output of the amplifier 3a and the maximum voltage supplied between points 51a and 52a is equal to E (power supply voltage). Then the output 31a of the amplifier 3a can vary up to + or -E to the input reference potential and therefore a large current can be supplied by the load 1a. Thus it is possible to improve the availability of a power supply as well as the power loss in the amplifier.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention relates to a constant current drive circuit that supplies a constant current in both positive and negative directions to an arbitrary load.

BACKGROUND OF THE INVENTION Conventional constant current drive circuits often have a structure in which the input reference potential is fixed, as shown in FIG. 3, for example.

That is, the voltage E of the constant voltage power supply 1 is divided by the voltage divider 2,
A voltage of E/2 is applied to the non-inverting input 31 of the input reference potential setting differential amplifier 3, and the impedance is converted to output 32.
A fixed potential of E/2 is obtained. Using this as the input reference potential, the current control signal V is input to the input terminal 4.5. In response to the input signal ■, the load current control differential amplifier 6 tries to obtain a certain constant potential Vo at the connection point 9 between the load 7 and the current detection resistor (Rcs) 8. Therefore, a current determined by Vo and Rcs will flow to the load.

Problems to be Solved by the Invention However, in the above circuit, the input reference potential is fixed, so the output of the load current control differential amplifier 6 is ±E/2 ( E is the power supply voltage).

Therefore, there have been problems in that the power supply efficiency is very poor and the power loss occurring in the load current control differential amplifier 6 is also large.

In view of the above-mentioned problems, the present invention provides a constant current drive circuit that aims to improve the efficiency of use of a power source and obtain high output.

Means for Solving the Problems In order to solve the above problems, the constant current drive circuit of the present invention applies the output of the load current control differential amplifier to the inverting input of the input reference potential setting differential amplifier. The device has a configuration in which negative feedback is applied to the input reference potential to change the input reference potential.

Effect of the Invention With the above-described configuration, the input reference potential can be changed from 0 (V) to the power supply voltage by the output of the differential amplifier for load current control. A power supply voltage can be applied to both ends at the time of maximum output, and it is possible to improve the usage efficiency of the power supply and the power loss occurring within the differential amplifier for controlling the load current.

Example Below, regarding a constant current drive circuit according to an example of the present invention,
This will be explained with reference to the drawings.

FIG. 1 shows a constant current drive circuit in a first embodiment of the present invention. In FIG. 1, la is an arbitrary load and 2a is a current detection resistor.

An arbitrary load 1a and a current detection resistor 2a are connected in series between the outputs 31a and 41a of the two differential amplifiers 3a and 4a. Connect the load 1a and current detection resistor 2a at 8 points 5
0a, the other end of load 1a is 5 points 51a, current detection resistor 2a
If the other end is the 0 point 52a, the 5 point 51a is the output 31 of the load current control differential amplifier (hereinafter referred to as ``amplifier'') 3a.
a, and the 0 point 52a is connected to the output 41a of an input reference voltage setting differential amplifier (hereinafter referred to as V amplifier) 4a. 60a and 61a are current control input terminals (hereinafter abbreviated as input terminals). Input terminal 60a is resistor 70
a, and the three points 50a are connected to the inverting input 32a of the amplifier 3a through the feedback resistor 71a, the input terminal 61a is connected through the resistor 72a, and the zero point 52a is connected through the feedback resistor 73a! It is connected to the non-inverting input 33a of the amplifier 3a. The 5 point 51a is connected to the inverting input 42a through the resistor 81a, and the 0 point 52a is connected through the feedback resistor 82a.

On the other hand, the midpoint potential of the voltage divider 10a that divides the voltage of the constant voltage power supply 9a is applied to the non-inverting input 43a. ■Amplifier 3
Power for the amplifiers 4a and 4a is supplied from a constant voltage power supply 9a.

Regarding the constant current drive device configured as above,
The operation will be explained below using FIG.

First, the resistance values of the resistors 70a and 72a are rl, and the resistance values of the resistor 71a are
, the resistance value of 73a is r2, the resistance value of current detection resistor 2a is R1, the current flowing through current detection resistor 2a is I, the potential of 5 points 51a is ebSa, the potential of point 50a is ea, the potential of 0 point 52a is ec, the resistance Assuming that the resistance value of 81a and 82a is r3, the voltage of the constant voltage power supply is E, and the current control input voltage input to the input terminals 60a and 61a is V, the following equation holds true for the amplifier.

ec-r 1/ (r 1+r2) = (ea-V) ・rl/ (rl+r2)+V
Organizing this (ea-ec) ・rl=-r2・VHere, ea-
From ec=I・R, 1=(r2/(rl−R))・V. Since the current flowing through the load can be considered to be equal to the current I flowing through the current detection resistor 2a, a constant current determined by the current control input voltage ■ flows through the load.

Next, regarding the V amplifier, from the voltage divider 10a ■amplifier 4
If the potential applied to the non-inverting input 43a of a is set to E/2, the following equation holds true.

e c=-e b -r 3/r 3 + ((r 3+r 3) /r 3) ・E/2 Organizing this, ec=E-eb Therefore, ■The output of the amplifier is determined by the output of the ■amplifier. , the maximum voltage applied between the five points 51a and 52a is E
becomes. As described above, according to this embodiment, by configuring the circuit as shown in FIG. 1, the output 31a of the load current control differential amplifier 3a is 10E (E
can be changed up to the power supply voltage).

A second embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 is a circuit diagram of a constant current drive circuit showing a second embodiment of the present invention. In FIG. 2, 1b and 2b are output current supply devices, respectively, between the output 31b of the load current control differential amplifier 3b and the load 4b, and between the output 51b of the input reference potential setting differential amplifier 5b and current detection. Resistor 6
b, and its power source is a constant voltage power source 7b.
Supplied by The other circuit configurations are the same as in the first embodiment of the present invention.

The operation of the constant current drive circuit configured as above is as follows.
This is the same as in the first embodiment of the present invention, but by providing the output current supply devices 1b and 2b, a larger current can be supplied to the load.

Effects of the Invention As described above, according to the constant current drive circuit of the present invention, by changing the input reference potential, the output of the load current control amplifier can be increased up to ±E (E is the power supply voltage), that is, with respect to the input reference potential. The voltage applied to the series circuit of the load and the current detection resistor can be varied up to ±E, and the efficiency of power supply usage and power loss within the amplifier can be improved.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a constant current drive circuit according to a first embodiment of the present invention, FIG. 2 is a circuit diagram of a constant current drive circuit according to a second embodiment of the present invention, and FIG. 3 is a circuit diagram of a constant current drive circuit according to a second embodiment of the present invention. FIG. 3 is a circuit diagram of a drive circuit. 2a, 6b, 8... Current detection resistor, 1a, 4b
, 7... Any load, 3a, 3b, 6...
・Differential amplifier for load current control, 4a, 5b, 3...
...Differential amplifier for input reference potential setting, tOa, 2...
...Voltage divider, 9a, 7b, 1... Constant voltage power source, 1b, 2b... Output current supply device.

Claims (2)

[Claims] (1) An arbitrary load and a current detection resistor are connected in series between the outputs of two differential amplifiers, and the connection point is the first connection point, the other connection point of the arbitrary load is the second connection point, and the If the other connection point of the current detection resistor is the third connection point, the terminal that serves as the reference potential of the set of current control input terminals is the first input terminal, and the other input terminal is the second input terminal, then the second connection The point is connected to the output of the differential amplifier for load current control, the second input terminal is connected to the inverting input of the differential amplifier for load current control through a first resistor, and the first connection point is connected to the inverting input of the differential amplifier for load current control through a first feedback resistor. connected, the first input terminal passing through a second resistor;
Further, the third connection point is connected to the non-inverting input of the load current control differential amplifier through a second feedback resistor, the third connection point is connected to the output of the input reference potential setting differential amplifier, and the third connection point is connected to the output of the input reference potential setting differential amplifier. The two connection points are connected through a third resistor, and the third connection point is connected to the inverting input of the input reference potential setting differential amplifier through a third feedback resistor, and the middle point of the voltage divider that divides the voltage of the constant voltage power supply. A potential is connected to a non-inverting input of the input reference potential setting differential amplifier, and power for the load current control and input reference potential setting differential amplifier is supplied from the constant voltage power supply. Current drive circuit. (2) The constant current drive circuit according to claim (1), wherein an output current supply device is attached to the output of the differential amplifier for load current control and input reference potential setting.