JP2591901Y2 - Voltage monitoring circuit of power supply circuit - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a voltage monitoring circuit for detecting a voltage abnormality in a power supply circuit for supplying power to a device under test (hereinafter, referred to as a DUT) such as an IC.

[0002]

2. Description of the Related Art Next, the configuration of a conventional voltage monitoring circuit will be described with reference to FIG. 2 is a D / A converter, 2
Is an amplifier, 3 is a current amplifier circuit, 4 is a DUT, 9 and 10 are power supplies, 13 and 14 are adders, 15 is an attenuator, 16 and 17
Is a comparator, and 18 and 19 are AND gates. Signal 11
Is a power on signal of the external control signal, and signal 12 is a power off signal of the external control signal. Signals 11 and 12 are D /
The output Va of the D / A converter 1 is input to the A converter 1 and the output Va of the D / A converter 1 is multiplied by A.
It is applied to UT4 as voltage Vo. The attenuator 15 reduces the output voltage Vo of the current amplification circuit 3 to 1 / A. The power supply 9 outputs a voltage ΔV, and the power supply 10 outputs a voltage −ΔV.

The adder 13 receives the output Va of the D / A converter 1 and the voltage ΔV of the power supply 9 and outputs Va + ΔV.
The adder 14 receives the output Va of the D / A converter 1 and the voltage −ΔV of the power supply 10 and outputs Va−ΔV. Comparator 1
6 uses the output (Va + １３V) of the adder 13 as a reference input,
The output Vo / A of the attenuator 15 is used as a comparison input. (Vo /
A)> (Va + △ V), the comparator 16 sets the + input
Compared with-input is larger, so output "L".
You. Here, Vo is multiplied by A by amplifier 2 to obtain a voltage Vo.
Is the voltage that has passed through the current amplifier 3, and Vo / A is usually Va
And almost the same voltage. The comparator 17 is
The output (Va−ΔV) is used as a reference input, and the output of the attenuator 15 is used.
Vo / A is set as a comparison input. (Vo / A) <(Va- △)
V), the comparator 17 has a negative input compared to a positive input.
The output becomes "L" because the size becomes large.

The outputs of the comparators 16 and 17 are respectively AND
Input to the gates 18 and 19, AND gates 18 and 19
Is activated when the signal 11 is at "H" level, and the comparator
A signal is output when the outputs 16 and 17 are at "H" level . Therefore, if the output voltage Vo becomes Vo> A (Va + ΔV) or Vo <A (Va−ΔV) while the power supply circuit of FIG. To inform.

[0005]

[Problems to be solved by the invention] According to FIG.
Compare the output of the converter 1 with the output of the power supply circuit and set
Value of the power supply circuit compared to the voltage of the D / A converter 1
Detects abnormality when the output is separated. This power supply circuit
When the power is turned on, the set value is set to the D / A converter 1
And the D / A converter 1 is turned off by sending the signal 11.
The analog value is sent to the amplifier 2 and amplified.
The set voltage is supplied to T4. But signal 11 is sent
Time from when the D / A converter 1 reaches the set value
And the time until the output of the power supply circuit reaches the set value.
There is a difference, and the voltage difference between the two due to this time difference is
6.17 may be detected and detected as abnormal.
Is effective only when the output voltage reaches the set value
It is. This power supply circuit is mounted on an IC tester.
When the power is turned on, the signal 11 becomes a logical "1".
Signal 12 is more logical than the power-on state
The power-off state of "1" is longer in time
It is better to monitor the voltage in this state
It is.

This invention divides the voltage between the output voltage of the power supply circuit and the power supply voltage to form an upper limit voltage and a lower limit voltage, and uses the upper limit voltage and the lower limit voltage as inputs of a comparator, and a threshold value is provided to the input of the comparator. Determine the level, connect a constant voltage diode to protect against excessive input, and enable signal 12
Input to the AND gate as the signal
It is an object of the present invention to provide a voltage monitoring circuit for detecting an abnormality of the power supply circuit when the power supply circuit is at the "H" level, that is, when the power supply circuit is off .

[0007]

In order to achieve this object, the present invention provides a D / A converter 1 having a power-on first signal 11 and a power-off second signal 12 as inputs.
A power supply circuit that includes an amplifier 2 that amplifies the output of the A / A converter 1 and a current amplifier circuit 3 that receives the output of the amplifier 2 as an input, and supplies an output voltage Vo of the current amplifier circuit 3 to the sample 4 to be measured. In contrast, the first resistor 5A and the second resistor 5B divide the voltage between the output voltage Vo and the first power supply voltage Vc, connect the voltage dividing point to the + input terminal of the comparator 7, and Second
Between the third resistor 5C and the fourth resistor 5C.
D, the voltage dividing point is connected to the negative input terminal of the comparator 7, and the anode of the first constant voltage diode 6A is connected to the comparator 7
And the cathode of the second constant voltage diode 6B is connected to the-input of the comparator 7 and the anode is grounded. The AND gate 8 is connected to the output of the comparator 7 and the second When the signal 12 is input and the second signal 12 is at the “H” level, the operation state is set and the power supply
The output voltage Vo of the path is reduced by the first resistor 5A, the second resistor 5B and
And a voltage divided by the first power supply voltage Vc.
+ Input voltage of the unit 7 is a constant voltage diode as the lower limit voltage.
-Input clamp voltage of comparator 7 determined by 6B
Or lower than the output voltage of the power supply circuit
Vo is supplied to a third resistor 5C, a fourth resistor 5D, and a second power source.
The negative input voltage of the comparator 7 divided by the voltage −Vd is
The limit voltage is determined by the constant voltage diode 6A.
When it becomes higher than the clamp voltage of the + input of the comparator 7
Then, the output of the comparator 7 becomes "L", and the output voltage abnormality is detected via the AND gate 8 in the power-off state where the output voltage is not set in the power supply circuit.

[0008]

Next, the configuration of the voltage monitoring circuit according to the present invention will be described with reference to FIG. 5A to 5D are resistors, 6A and 6
B is a constant voltage diode, 7 is a comparator, 8 is an AND gate, and 1-4 are the same as those in FIG. Resistors 5A and 5B connect between the output voltage Vo of the current amplification circuit 3 and the power supply voltage Vc.
Partial pressure. Further, the voltage between the output voltage Vo of the current amplification circuit 3 and the power supply voltage Vd is divided by the resistors 5C and 5D. Resistance 5A
Assuming that the resistance values of .about.5D are Ra, Rb, Rc, and Rd, respectively, the input voltage Ve at the + terminal and the input voltage Vf at the-terminal of the comparator 7 are given by the following equations. The power supply voltages Vc and Vd are supplied as the power supply voltage of the comparator 7. Ve = {Ra × Vc / (Ra + Rb)} + {Rb × Vo / (Ra + Rb)} (1) Vf = {Rc × Vd / (Rc + Rd)} + {Rd × Vo / (Rc + Rd)} ............ (2)

The constant voltage diode 6 is connected to the + input of the comparator 7.
The anode of A is connected, and the cathode of constant voltage diode 6A is connected to ground. The negative input of the comparator 7 is connected to the cathode of the constant voltage diode 6B, and the anode of the constant voltage diode 6B is connected to the ground. The zener voltage of the constant voltage diode 6A is Vg, and the forward voltage is Vg.
Assuming that j is the zener voltage of the constant voltage diode 6B and Vk is the forward voltage, the + and-inputs of the comparator 7 are clamped by the constant voltage diodes 6A and 6B as follows. -Vg <+ input voltage <Vj ... (3) -Vk <-input voltage <Vh ... (4)

From this, the excessive input of the comparator 7 due to the output voltage Vo is protected by the voltages Vg · Vh,
The threshold level of the comparator 7 is determined by Vk. The Vg, Vj, Vh, Vk and each input clamp voltage
FIG. 3 shows the relationship between the ranges. In FIG. 3, -Vg, -V
The voltage increases in the order of k, Vj, and Vh. From comparator 7
The output of the “L” level is caused by the + input voltage of the comparator 7.
Is lower than the input clamp voltage, or
Comparator 7 is higher than the + input clamp voltage.
This is the area indicated by the hatched portion in FIG. Toes
When the input voltage is less than -Vk and when the input voltage is less than Vj,
It is time. Substituting this condition into equations (1) and (2) gives
An equation for determining the upper limit voltage and the lower limit voltage in FIG. 1 is derived. Upper limit voltage = {(Rc + Rd) / Rd} * {Vj-Rc * Vd / (Rc + Rd)} (5) Lower limit voltage =-(Ra + Rb) / Rb * @ Vk + (Ra * Vc) / ( Ra + Rb)｝ (6) The output voltage Vo is output to the AND gate 8 with respect to the upper limit voltage and the lower limit voltage determined by the resistors 5A to 5D and the voltages Vc and Vd.
Monitor while the signal 12 is output.

Next, a numerical example of FIG. 1 will be described. Power supply voltage Vc = + 15V, power supply voltage Vd = -15V, Zener voltage V
Assuming that g = Vh = 12 V and forward voltage Vj = Vk = 1 V, from Equations (3) and (4), the + input and the − input of the comparator 7 are −12 V <+ input voltage <1 V−1 V <− The input voltage is clamped in the range of <12 V and is protected from exceeding the power supply voltage of the comparator 7.

For example, a condition for monitoring the output voltage Vo when the signal 12 is on in a range of ± 2 V is obtained. When the resistances Rb and Rc are obtained by substituting the numerical values into the equations (5) and (5) and setting the resistances Rb = Rd = 1 kΩ, Ra = Rc = 62.5Ω. From this, when the signal 12 is on, the output voltage Vo
An output is output from the AND gate 8 when <−2 V or the output voltage Vo> +2.

[0013]

According to the present invention, an upper limit voltage and a lower limit voltage are created by dividing the output voltage of the power supply circuit and the power supply voltage, and the upper limit voltage and the lower limit voltage are input to the comparator. determining the threshold level on the input, connect a constant voltage diode to protect excessive input, a signal 12 rice
Input to the AND gate as a cable signal ,
When the signal 12 is at "H" level, that is, when the power supply circuit is off.
The abnormality of the power supply circuit at the time of the power failure can be detected.

[Brief description of the drawings]

FIG. 1 is a configuration diagram of a voltage monitoring circuit according to the present invention.

FIG. 2 is a configuration diagram of a conventional voltage monitoring circuit.

FIG. 3 is a diagram showing a monitoring range of the voltage monitoring circuit according to the present invention.

[Explanation of symbols]

 Reference Signs List 1 D / A converter 2 Amplifier 3 Current amplifier circuit 4 DUT (sample to be measured) 5A to 5D Resistor 6A / 6B Constant voltage diode 7 Comparator 8 AND gate

Claims (1)

(57) [Scope of request for utility model registration] 1. A D / A converter (1) having a power-on first signal (11) and a power-off second signal (12) as inputs,
An amplifier (2) for amplifying the output of the A converter (1), and an amplifier
And a current amplifier circuit (3) that receives the output of (2) as an input, and outputs the output voltage Vo of the current amplifier circuit (3) to the sample under test (4).
The first resistor (5) is connected between the output voltage Vo and the first power supply voltage Vc.
A) and the second resistor (5B) to divide the voltage, and determine the voltage dividing point by the + of the comparator (7).
Connected to the input terminal, the output voltage Vo and the second power supply voltage -V
d is divided by a third resistor (5C) and a fourth resistor (5D), and the voltage dividing point is connected to the negative input terminal of the comparator (7), and the first constant voltage diode (6A) Is connected to the + input of the comparator (7) and the cathode is grounded. The cathode of the second constant voltage diode (6B) is connected to the-input of the comparator (7) and the anode is grounded. Gate (8) is a comparator
The output of (7) and the second signal (12) are input and the second signal (1
2) is at the “H” level, it is in the operating state and the power supply circuit
The output voltage Vo is divided into a first resistor (5A), a second resistor (5B) and
And a comparator divided by the first power supply voltage Vc.
The (+) input voltage of (7) is a constant voltage diode as the lower limit voltage.
-Input clamp voltage of comparator (7) determined by (6B)
Voltage or the output power of the power supply circuit.
The voltage Vo is supplied to the third resistor (5C), the fourth resistor (5D) and the second voltage.
-Input voltage of comparator (7) divided by source voltage -Vd
Is determined by the constant voltage diode (6A) as the upper limit voltage.
Higher than the clamp voltage of the + input of the comparator (7)
The output of the comparator (7) becomes "L" when the power supply circuit is not powered and no output voltage is set in the power supply circuit via the AND gate (8). A voltage monitoring circuit for a power supply circuit.