JPS63135879A - Power source circuit - Google Patents

Abstract

PURPOSE:To protect a load from overcurrent, by providing a current booster with a circuit for selecting a limit current value. CONSTITUTION:When a specified voltage is applied to a load 13, switches SW1-SWm and SWa-SWd are selectively operated according to a range of current and voltage set with a range switching circuit 20 to connect resistances R2-Rn in series to a resistance R1, provided that only the resistance R1 is inserted into a current circuit in the max. current range, excluding all others R2-Rn. As a result, a voltage develops corresponding to a supply current be tween a current booster 17 side terminal of the resistance R1 and a probe 12 side terminal regardless of any switched range of the set current value. The voltage is applied to a current value detection circuit 8 and when an output voltage thereof exceeds a given value Vc, a bidirectional clamp diode 9 conducts to limit an input voltage to an operational amplifier 10 to the voltage deter mined by the diode 9. This allows the flowing of no greater current to the load 13 than a value governed by an input voltage thus clamped irrelevant to the set current thereby assuring the protection of the load 13.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a power supply circuit, and particularly to a power supply circuit that supplies power at a predetermined voltage to a power supply terminal or the like of an IC to be tested by an IC tester.

[Prior Art] For example, in an IC tester, a predetermined measurement is performed by supplying power to a power pin or chip of an IC under test.
The test is executed. In this case, the current supplied from the power supply circuit to the power supply end Y etc. of the IC varies depending on the type of IC to be tested, but if you try to test more types of ICs, the current supplied from the power supply circuit to the power supply terminal Y etc. of the IC will vary from several hundred nA to IA. A range up to is required. - On the other hand, the voltage is also 5 in the IC.
It is a constant voltage of about V, 12V, or 40V, and can be set by a control signal.

Note that in cases where the IC to be tested is not packaged, or depending on the shape of the IC package, current may be supplied by directly contacting the terminal with a probe instead of supplying power through the socket terminal. be exposed.

FIG. 4 is a block diagram showing an example thereof, in which a current booster circuit (hereinafter referred to as a current booster) 111 having an operational amplifier 10 and a limit circuit, a probe 12, an ICl 3 as a sample with which the probe 12 comes into contact, and the probe 12
A negative feedback circuit group 14 a * 14 that is connected to and forms a constant voltage loop to apply a constant voltage to ICl3.
b −... and voltage limiting resistors 15af t5b* @... inserted in these negative feedback circuits 14, respectively.
and a voltage range setting switch circuit 16a that selectively connects these negative feedback circuits to the input side of the operational amplifier 10.
It consists of 1eb, -...

[Problems to be Solved] In such a circuit, a limit circuit is provided in the current booster or the like to protect the current from flowing even if a large current flows through the power supply circuit itself. However, the drawback is that the load side is not protected if an overcurrent flows due to a malfunction during range switching or an error in the control signal.

This is particularly likely to occur when the set voltage is high and a large current is flowing.For example, when an overcurrent of several A is flowing at 40V, the load on an IC or electronic circuit such as a transistor may be affected. There is a risk of destroying it. Also, in cases such as when a large voltage or overcurrent flows,
Probe wear is high and its lifespan is shortened.

Furthermore, when a circuit such as an IC on the load side is short-circuited, the conventional limit circuit does not necessarily provide sufficient protection, and this problem becomes more problematic as the set voltage and current are larger.

[Object of the Invention] Therefore, an object of the present invention is to provide a power supply circuit that can solve these problems and protect the load by preventing an overcurrent exceeding a predetermined value from flowing through the load. .

[Measures to solve the problem] By the way, in order to protect the load, it is possible to reduce the limit current value (reduce the current value to be limited to a low value), but in a small current range, the current limit Because the value of the load resistor is large, its current is limited, causing the operational amplifier and current booster (buffer T) in the constant current loop circuit to saturate, and it takes a long time for the load current to stabilize to a steady value. , there are disadvantages such as increased measurement time.

Therefore, in order to achieve the above L1 objective and eliminate such drawbacks, the present invention provides that the buffer circuit is equipped with a limit circuit whose limit current value can be switched,
In order to apply a constant voltage to the load, the voltage on the load side is negatively fed back to the input side of the amplifier to form a constant voltage loop, and the current path in series with the load included in this constant voltage loop is connected to a current range switching circuit. By inserting a resistor, the current supplied to the load is limited to the first current value range by the voltage drop across this resistor, and the second current value is increased by shorting the resistor or inserting a resistor in parallel. The selection of either the first current value range or the second current value range and the switching of the IJ current value are controlled in conjunction with each other.

[Function] In this way, the current booster is equipped with a circuit that can select the limit current value, and a resistor for switching the current range is inserted in the current path in series with the load included in the constant voltage loop to interlock them. If selected, when a high current value is set at a high voltage, the limit current value on the current booster side can be set to lower, so that transient current can be prevented and the load can be protected.

In addition, if you detect the voltage across the current range switching resistor and clamp the input side of the amplifier to a predetermined value when this voltage exceeds a certain value, you can prevent overload within that range. Current can be detected and load protection can be achieved with a simple circuit.

[Example] Hereinafter, an example of the present invention will be described with reference to the drawings.

FIG. 1 is a block diagram showing an embodiment of a program power supply circuit to which the power supply circuit according to the present invention is applied, FIG. 2 is an explanatory diagram of a specific example of the current booster, and FIG. FIG. 2 is a block diagram showing an example of a power supply circuit. Components that are the same as those in FIG. 4 are indicated by the same symbols.

In the figure, 1 is a program power supply circuit that supplies power to a load 13, and is regulated by a constant voltage loop circuit 2.
A cardiac pressure vl is applied, and a predetermined current is supplied to the load 13.

This constant voltage loop circuit 2 has a general configuration.

That is, the DC voltage V2 specified by the digital signal 4 from the digital/analog converter 3 is applied to the inverting input of the operational amplifier 10 via the resistor 5, and the load voltage Vl is applied to the voltage follower of the operational amplifier 10 and the resistor 6.
Feedback is provided via. Note that the non-inverting input of this operational amplifier 10 is grounded.

The output of the operational amplifier 10 is a current booster (buffer) 17
The output thereof is connected to the probe 12 via the range switching circuit 7 and is supplied to the load 13.

Here, the gain of the constant voltage loop circuit 2 is determined by the values of the resistors 5 and 6, and the load voltage vl is maintained at a constant value proportional to the DC voltage V2. Details of the current booster 17 will be described later, but as shown in FIG. 2, the current booster 17 is configured such that its limit circuit can switch ranges depending on the output voltage and the selected set current range.

Now, the current path in series with the load 13 in the constant voltage loop circuit 2, that is, the current range switching circuit 7 inserted between the output of the current booster 17 and the probe 12 is a series circuit of a plurality of current limiting resistors. It consists of a switch circuit for switching current ranges that connects these resistors in stages.

Both ends of the current range switching circuit 7 are connected to a current value detection circuit 8 consisting of an operational amplifier.
The output of is connected to the input side of an operational amplifier 10 via a bidirectional clamp diode 9 with a clamp voltage Vc.

R7''Rn is the current limiting resistor. Among the current limiting resistors, one of the resistors R2 to Rn other than the resistor R/ is selectively inserted depending on the set current range. The switch circuit SW7-8W+s (m=n-
1) is provided in association with the resistors R2 to Rn as shown.

That is, in this example, the current limiting resistors R2 to R
In order to short-circuit or connect n, a switch circuit 5Wi(i
=1 to n-1) are connected between the terminals of the current limiting resistors R2 to Rn-7 and the terminals of the probe 12, respectively. Then, the switch circuit corresponding to these resistors is turned “ON”
As a result, each resistor is successively connected in series, and the total resistance increases step by step.

20 is a range switching circuit, which receives a digital control signal 21
Accordingly, the opening/closing of the switch circuit SW/-3W- and the range of the limit circuit of the current booster 17 are controlled. When applying a predetermined voltage to the load 13, the range switching circuit 20 selects the switch circuit SW/''SWw and the switch circuit SWa of the limit circuit described later, 5Wbt according to the current range and voltage range to be set.
SWc.

The necessary ones of SWd are opened or closed, and the resistance R
1, resistors R2 to Rn are connected in series in stages to select a limit circuit. Therefore, a series circuit of resistor R/ and resistors R2 to Rn is connected in series and inserted into the current path. However, in the maximum current range, the resistance R
, are inserted, and the other resistors R2 to Rn are not inserted.

As a result, no matter which range the set current value is switched to, the output side terminal of the current booster 17 of the resistor R and the resistor R
A voltage corresponding to the supplied current value appears between the probe 12 side terminal of n and the terminal on the probe 12 side. This voltage is manually input to and detected by the current value detection circuit 8, and when the output voltage of the current value detection circuit 8 exceeds a certain value Vc, the bidirectional clamp diode 9 becomes conductive, and the voltage is determined by this clamp diode 9. The input voltage of the operational amplifier 10 is limited to the voltage that is applied. Therefore, regardless of the set current range, no current of the amount determined by the clamped input voltage flows through the load 13, and the load 13 is protected.

This also applies when the load 13 is an IC or the like and the circuit is shut down and an overcurrent flows.

In addition, in such a circuit, the load current is fixed! −
Since it is unobtrusive, saturation of the operational amplifier 10 and current booster 17 in the constant voltage loop circuit 2 does not occur.

Next, the current booster 17 that can switch the limit current value will be explained according to FIG.

The current booster 17 has bipolar transistors Ql and Qq, and Q/ and Qtt are NPN type and PN type.
They are interconnected to form a P-type complementary push-pull circuit. The emitter of the bipolar transistor Q/ is connected to the output terminal (resistance R
The emitter of the bipolar transistor QQ is coupled to the output terminal (terminal of the resistor R/) through a series circuit of resistors Re and Rd, and the collector of the bipolar transistors QI and Q// is coupled to the terminal F) of the bipolar transistor QI and QQ. are connected to power supplies +V and -V, respectively.

On the other hand, bipolar transistor Q1. The base of Q// is a level shifting diode D2. It is coupled to the output terminal of the operational amplifier 10 via the DJ. I)/, D4
is a diode I)2. This is a constant current diode for passing a forward bias current through D3 and the bipolar transistor Q/*Qtt.

Furthermore, in a bias circuit for bipolar transistors Qt and Qq, bipolar transistor Qt.

As a current limiter element r for limiting the current flowing through Qtt, NPN type and PNP type bipolar transistors Q 29 Q a are connected as shown. That is, the base of bipolar transistor Q2 is connected to switch circuits SWa and SWb, respectively, and the other of these switch circuits SWa and SWb is connected to the emitter of bipolar transistor Qt and the connection point of resistors Ra and Rh, respectively. The base of bipolar transistor Q3 is connected to switch circuits SWc and SWd, respectively, and similarly, the other of these switch circuits SWc and SWd is connected to the connection point between the emitter of bipolar transistor Q3 and resistors Re and Rd, respectively. Here, switch circuits SWa and SWc operate simultaneously, and switch circuits SWb and SWd operate simultaneously.

In such a configuration, the test signal is applied to the operational amplifier 10.
(signal amplification section), and the inverted amplified signal is inverted and amplified by the diode l)2.1), ? The forward voltage of the bipolar transistor Q/, Q
4, the current is amplified and output to the output terminal (terminal of resistor R/).

Then, the switch circuits SWa and SWc are turned ON at the same time.
” (However, the switch circuit swb.

When SWd is "OFF", the limit current value becomes small, and the current output from the current booster 17 is limited to a low current value. Also, when the switch circuits swb and swd are turned ON at the same time (however, the switch circuit S Wa 9
When S Wc is "OFF", the limit current value becomes large, and the current output from the current booster 17 is limited to a high current value. And the “ON” of these switch circuits
10FF'' is controlled by the range switching circuit 20 in conjunction with the switching of the switch circuits swt-sw.
, when the current range is set, the switch circuit SW
l and switch circuits SWb and SWd are interlocked and turned on.
” state. Conversely, when the voltage and current ranges are set to supply power of ±40 V at 0.5 A or more, one selected from the switch circuits SWz” and SW+s is turned “ON”. , the switch circuits SWa and SWc are turned on at the same time, reducing the limit current value to prevent the operational amplifier and current booster (buffer) in the constant current loop circuit from saturating, and the load current to a steady value. Improve responsiveness by shortening the time it takes to stabilize.

FIG. 3 is a circuit diagram showing another embodiment of the current measuring circuit according to the present invention. In this figure, the same reference numerals as in FIG. 1 indicate equivalent elements.

In the current measuring circuit of this embodiment, the current limiting resistors R11-Rn are connected in parallel, and the resistors R12-Rn and the switch circuit SWl1-SWm are connected in series, and the switch circuit SW/t is connected in series. " By selectively shorting S Wm, the current range is switched.The series circuit of the resistors R12 to Rn and the shorting switch circuit 5WII-8W- changes the current as shown in the figure. The output of the booster 17 and the probe 12 are connected in parallel to the resistor R11.

The configuration other than this is the same as the previous embodiment.

Although two embodiments have been described above, the present invention is not limited thereto, and can be implemented with appropriate modifications within the scope of the invention. For example, as the short-circuiting switch element, an electronic switch circuit such as an analog switch or the like, for example, a relay circuit, etc. can be used.

In the embodiment, multiple resistors are provided for switching the current range, and one of them is designed to prevent short-circuiting.
In the present invention, it is sufficient to provide at least one resistor and simply short-circuit or connect the resistors.

In addition, the voltage across the resistor for switching the current range is detected, and when this voltage exceeds a certain level, the input side of the amplifier is clamped to a predetermined value, but it is not always necessary to use a clamp circuit. There is no need to provide it.

In addition, although a probe is used to contact the sample, the connection with the sample terminal is not limited to the probe, and although the explanation focuses on the program power supply circuit of the tester, it can also be used with general power supply circuits. Of course, it may be.

[Effects of the Invention] As described in detail in connection with the embodiments, the present invention provides a current booster with a circuit that can select a limit current value, and furthermore, a circuit that can select a current limit value in a constant voltage loop. If a resistor for switching the current range is inserted in the circuit and these are selected in conjunction with each other, when a high current value is set with a crystalline voltage, the limit current value on the current booster side will be lowered. Since it can be set to , it is possible to prevent transient currents and protect the load.

In addition, if you detect the voltage across the current range switching resistor and clamp the input side of the amplifier to a predetermined value when this voltage reaches a certain level, you can prevent overload within that range. Current can be detected and load protection can be achieved with a simple circuit.

[Brief explanation of the drawing]

FIG. 1 is a process diagram showing one embodiment of a program power supply circuit to which the power supply circuit according to the present invention is applied;
The figure is an explanatory diagram of a specific example of the current booster, and FIG.
A block diagram showing an example of another program power supply circuit,
FIG. 4 is a block diagram of a conventional power supply circuit. DESCRIPTION OF SYMBOLS 1... Program power supply circuit, 2... Constant voltage loop circuit, 3... Digital/analog converter, 7... Range switching circuit, 8... Current value detection circuit, 9... Clamp diode , 10... operational amplifier, 17... current booster (buffer), 11.12... probe, 1
3...Load, R/"Rn, R/t-Rn・
・・Resistance for current range setting, SW7 "SWm, SW
I1~SWm... Switch circuit for switching current range, SWa, SWb, SWe, 5WrJ --- Switch circuit for setting limit current, 20... Range switching circuit.

Claims (4)

[Claims] (1) In a power supply circuit comprising an amplifier that receives a control signal and a buffer circuit that receives an output from the amplifier and supplies power at a predetermined voltage corresponding to the control signal to a load, the buffer circuit has a limit current value of is provided with a switchable limit circuit, and in order to apply a constant voltage to the load, the voltage on the load side is negatively fed back to the input side of the amplifier to form a constant voltage loop. A resistor for current range switching is inserted in a current path in series with the load, and the voltage drop across this resistor limits the current supplied to the load to a first current value range, and the resistor is short-circuited or The current value is limited to a second current value range by inserting a resistor in parallel with the limit current value, and the selection of either the first current value range or the second current value range and the limit current value are performed. A power supply circuit characterized in that switching is controlled in conjunction with switching. (2) The input side of the amplifier is clamped to a predetermined value when the voltage across the current range switching resistor is detected and the voltage exceeds a certain level. The power supply circuit described in item 1. (3) The current range switching resistor is composed of a series circuit consisting of multiple resistors, and the supplied current value is limited within each range by selectively or stepwise shorting or connecting multiple resistors. The power supply circuit according to claim 2, characterized in that: (4) The amplifier is an operational amplifier, the buffer circuit is a current booster circuit, and the load is an IC to be tested, and when the range of the set voltage and selected current value is large, a limit is applied in the current booster circuit. 4. The power supply circuit according to claim 2, wherein the current value is switched to a low value.