JP2001166014A - Current supply circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent an overcurrent output in a current supply circuit having both a big current range and a small current range at the time of a transient response without using a relay. SOLUTION: This current supply circuit has a feature that it is equipped with plural current range detecting resistors connected in series, and plural current output amplifiers connected to the connecting points of these current detecting resistors to output a designated current in accordance with a range selection, and supplies a current in a designated range from a small current range to a big current range to a load.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a current supply circuit, and more particularly, to an improvement in a transient response in a small current range in a circuit having a plurality of current output ranges.

[0002]

2. Description of the Related Art A semiconductor integrated circuit test apparatus must supply a predetermined power required for driving a DUT in accordance with a test item of a semiconductor device under test (hereinafter referred to as DUT: Device Under Test). By the way, with the recent increase in the degree of integration of semiconductor devices, a wide range of current supply performance is required such that a drive current of about several amperes is required at the time of operation of the DUT, but only a few microamperes is required during non-operation standby. It has become.

FIG. 10 is a basic configuration diagram of a conventional current supply circuit that meets such a demand. In the figure, an output signal of an output control circuit 1 is input to a current detection resistor group 3 via an amplifier 2. The output control circuit 1 receives the voltage setting signal and the current setting signal, receives the current detection signal from the current detection circuit 4, and feeds back a part of the output signal via the amplifier 5. Current detection circuit 4
Measures the voltage at both ends of the current detection resistor group 3 as a current detection signal.

FIG. 11 is a detailed circuit example of the amplifier 2 and the current detection resistor group 3 shown in FIG. The amplifier 2 includes transistors Q1 to Q9, constant current sources I1 and I2, and resistors R8 to R1.
5 and the like. The current detection resistor group 3 includes a first series circuit of a switch SW1 and a resistor R1, a switch SW1.
2 and a third series circuit of a switch SW3 and a resistor R3 are connected in parallel, and a voltage between both ends of each of the resistors R1 to R3 is detected by a voltage detector (not shown). The current value is obtained by measuring by means.

FIG. 12 is a diagram for explaining the operation of the current detection resistor group 3 in FIG. In FIG. 12, a first series circuit including a switch SW1 and a resistor R1 has a range of 10A,
The second series circuit including the resistor R2 and the resistor R2 has a 1A range, and the third series circuit including the switch SW3 and the resistor R3 has a 1A range. Here, FETs are used as switches SW1 to SW3.
Is used, the large current F used as SW1 and SW2 is used.
The capacitances C1 and C2 when the ET is off range from several hundred pF to several thousand pF. In general, the resistance R1 is several hundreds mΩ, the resistance R2 is several Ω, and the resistance R3 is several hundred kΩ.

[0006]

As shown in FIG. 12, in the current detecting resistor group 3 using a large current FET having relatively large off-state capacitances C1 and C2, a circuit when a small current range is selected is as follows. , The capacitances C1 and C2 as shown in FIG.
Can be rewritten as a parallel circuit of the combined capacitance C (= C1 + C2) and the resistor R3. As a result, a discharge current flows from the combined capacitance C during a transient response when switching from the large current range to the small current range, and an overcurrent is output when used as a constant current source.

As a countermeasure to eliminate such an overcurrent output during the transient response, it is conceivable to use a mechanical relay or a mercury relay having almost no capacitance when the switch is off. However, mechanical relays have problems in chattering and contact life during switching operation, and in the case of mercury relays, mounting conditions such as the relay mounting position are limited to the upside, and environmental problems during disposal. And the cost of parts is high.

The present invention focuses on these problems, and an object of the present invention is to provide an overcurrent output during a transient response in a current supply circuit in which a large current range and a small current range coexist.
It is to prevent without using a relay.

[0009]

According to a first aspect of the present invention, there is provided a power supply system comprising: a plurality of current range detecting resistors connected in series; And a plurality of current output amplifiers for outputting a predetermined current in accordance with the above-mentioned condition, and supplying a current in a predetermined range from a small current range to a large current range to a load.

As a result, there is no capacitance when the switch is turned off as in the prior art, and it is possible to prevent an overcurrent output during a transient response.

According to a second aspect of the present invention, in the current supply circuit of the first aspect, the output impedance of the current output amplifier is in a high impedance state when not selected.

As a result, the current output amplifier at the time of non-selection is substantially disconnected from the circuit, and has no electrical influence on the circuit.

According to a third aspect of the present invention, in the current supply circuit of the first aspect, a part of the current range detecting resistor is connected in parallel.

Thus, even if an FET is used as a switch, the off-state capacitance of the FET does not affect the switch.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a block diagram showing a main part of an example of an embodiment of the present invention. In the figure, three current range detection resistors R1 to R3 are connected in series, and a connection point of these current range detection resistors R1 to R3 includes a plurality of current output amplifiers AMP that output a predetermined current according to range selection.
Output terminals of 1 to AMP3 are connected respectively.

The switches SW8 to SW10 for controlling ON / OFF of the operation are connected to the output amplifiers AMP1 to AMP3. Then, the output amplifier AMP1 operates with only the switch SW8 turned on, and the output amplifier AMP2 operates with only the switch SW9 turned on.
The output amplifier AMP3 operates with only W10 turned on. When the switches SW8 to SW10 are off, the output impedances of the output amplifiers AMP1 to AMP3 become high impedance and do not operate.

FIG. 2 is a specific circuit diagram of the whole of FIG. 1, and FIG. 3 is a small current range (1 μm) in a state where only the switch SW8 is on.
FIG. 4 is an operation explanatory diagram of a large current range (10A range) in a state where only the switch SW10 is on.

In FIG. 3, output amplifiers AMP2 and AM
Since the output impedance of P3 is high, the output current of these output amplifiers AMP2 and AMP3 can be ignored. A that constitutes the output amplifier AMP1
The output current Iout of the MP output stage 1 flows through the current range detection resistors R1 to R3 connected in series. In this case, the detection of the current is performed by detecting any voltage between a and b, between bc and between cd.

In FIG. 4, output amplifiers AMP1, AM
Since the output impedance of P2 is high, the output currents of these output amplifiers AMP1 and AMP2 can be ignored. A that constitutes the output amplifier AMP3
The output current Iout of the MP output stage 3 flows through the current range detection resistor R1 connected in series. In this case, the current is detected by detecting the voltage between cd and d.

As described above, according to the present invention, since the relay of the output system is not required, the transient response characteristic at the time of constant current output in a small current range can be improved.

FIG. 5 is a diagram showing another specific circuit example, in which the effect of off-capacitance is eliminated when the current detection resistors R1 and R2 in the large current range are switched by the switches SW1 and SW2 using FETs. FIG. FIG. 6 is a diagram for explaining the operation in the small current range (1 μA range) in a state where the switch SW8 in FIG. 5 is turned on and the switch SW9 is turned off. FIG. 7 is a diagram illustrating the operation when the switch SW9 in FIG.
Large current range (1A range or 1
FIG. 4 is an operation explanatory diagram of (0A range).

In FIG. 6, since the output impedance of the output amplifier AMP2 is high, the output current of the output amplifier AMP2 can be ignored. Output current I of AMP output stage 1 constituting output amplifier AMP1
out is a first series circuit of a switch SW1 and a resistor R1 connected in series with a current range detection resistor R3, or a second series circuit of a switch SW2 and a resistor R2 connected in parallel with the first series circuit. Flows through. When the switch SW1 is turned on and the switch SW2 is turned off as shown in FIG. 6, the output current Iout of the AMP output stage 1 becomes the resistance R3, R1
Flows through. The detection of the current is performed by detecting the voltage between a and b.

In FIG. 7, since the output impedance of the output amplifier AMP1 is high, the output current of the output amplifier AMP1 can be ignored. Output current I of AMP output stage 2 constituting output amplifier AMP2
out flows through a first series circuit of the switch SW1 and the resistor R1 or a second series circuit of the switch SW2 and the resistor R2 connected in parallel with the first series circuit. In the case of the 10A range where the switch SW1 is turned on and the switch SW2 is turned off as shown in FIG. 7, the output current Iout of the AMP output stage 2 flows through the resistor R1. The current is detected by the resistor R1
This is performed by detecting the voltage between both ends. In the case of the 1A range, the switch SW1 is turned off and the switch SW2 is turned off.
Is turned on, and the current is detected by detecting the voltage across the resistor R2.

FIG. 8 is an equivalent circuit diagram when the small current range of FIG. 6 is selected, and FIG. 9 is an equivalent circuit diagram when the large current range of FIG. 7 is selected. In FIG. 8, the OFF capacitance C of the switch SW2
2 is several hundred pF to several thousand pF, the resistance R1 is several hundred mΩ to several Ω, and does not affect the output current Iout. Also in FIG. 9, the switch SW2 with respect to the resistor R1 is used.
Since the off-capacitance C2 is small, the overcurrent at the time of the transient response is sufficiently small with respect to 10 A, and can be practically ignored. That is, by connecting the current output amplifiers in multiple stages as shown in FIG. 5, the influence of the overcurrent at the time of the transient response due to the off capacitance of the switch can be sufficiently reduced.

[0025]

As described above, according to the present invention,
Overcurrent output during transient response in a current supply circuit in which a large current range and a small current range coexist can be prevented without using a relay.
It is suitable as a drive current supply circuit for T.

[Brief description of the drawings]

FIG. 1 is a block diagram showing a main part of an example of an embodiment of the present invention.

FIG. 2 is a specific circuit example diagram of the whole of FIG. 1;

FIG. 3 is an operation explanatory diagram of a small current range (1 μA range) in a state where only a switch SW8 is turned on.

FIG. 4 is an operation explanatory diagram of a large current range (10A range) in a state where only a switch SW10 is turned on.

FIG. 5 is another specific circuit example diagram.

6 is an operation explanatory diagram of a small current range (1 μA range) of FIG. 5;

FIG. 7 shows a large current range (1A range or 10A) of FIG.
FIG.

8 is an equivalent circuit diagram when the small current range in FIG. 6 is selected.

9 is an equivalent circuit diagram when the large current range in FIG. 7 is selected.

FIG. 10 is a basic configuration diagram of a conventional current supply circuit.

FIG. 11 is a detailed circuit example diagram of a broken line part in FIG. 10;

12 is an explanatory diagram of the operation of the current detection resistor group 3 in FIG.

FIG. 13 is an equivalent circuit diagram of FIG.

[Explanation of symbols]

 R1 to R3 Current range detection resistors AMP1 to AMP3 Current output amplifier SW8 to SW10 Switch

Claims (3)

[Claims] A plurality of current range detection resistors connected in series; and a plurality of current output amplifiers respectively connected to connection points of the current range detection resistors and outputting a predetermined current according to range selection. A current supply circuit for supplying a load with a predetermined range of current from a small current range to a large current range. 2. The current supply circuit according to claim 1, wherein the output impedance of said current output amplifier is in a high impedance state when not selected. 3. The current supply circuit according to claim 1, wherein a part of said current range detection resistor is connected in parallel.