JP2753898B2 - Test method for thermal shutdown operation of thermal shutdown circuit - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a heat shutoff operation of a heat shutoff circuit.
The present invention relates to an operation test method , in particular, when abnormal heat generation of a semiconductor integrated circuit device or an abnormal rise in external temperature, the function of the semiconductor integrated circuit device is stopped to protect the circuit device and devices connected thereto. Test method for thermal shutdown operation of shutoff circuit
Related.

[0002]

2. Description of the Related Art FIG. 4 shows an example of a conventional thermal cutoff circuit.
The reference voltage 8 by the band gap circuit 16 is normally
Since the voltage is set lower than the forward voltage 9 of the diode 18, the output 10 of the comparator 5 is in a low level state. The forward voltage 9 of the diode 18 has a negative temperature characteristic. That is, as the temperature increases, the forward voltage 9 of the diode 18 decreases. At a certain temperature, the forward voltage 9 becomes lower than the reference voltage 8, and the output 10 of the comparator 5 goes high. Therefore, transistor 1
2 conducts, the output 13 is grounded, and enters a thermal cutoff state.

In this thermal cutoff circuit, the reference voltage 8 is stabilized by the band gap circuit 16 in order to stably operate even if the power supply voltage 7 fluctuates.

Japanese Patent Application Laid-Open Nos. 61-70805 and 70809, and 1-20 Japanese Unexamined Patent Publication No.
No. 2118.

[0005]

The conventional circuit has a drawback that the number of elements in the circuit portion for generating the reference voltage 8 is large, and therefore the power consumption is increased. Further, there is a disadvantage that the chip occupation area increases. Furthermore, to check the circuit operation, put the heat shut-off circuit in a thermostat and heat it,
It was necessary to confirm the heat shutoff operation.

In particular, in the case of a thermal cutoff circuit with a thermal history, it has been necessary to cool down after a thermal cutoff operation has occurred and to confirm whether or not the operation is restored .

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for testing a thermal cutoff operation of a thermal cutoff circuit that can inspect a thermal cutoff operation without changing the temperature.

[0008]

The present invention achieves the above object.
To generate the reference voltage by dividing the power supply voltage.
Reference voltage circuit, temperature sensor circuit,
And a comparison circuit for comparing the reference voltage and the output of the comparison circuit.
And a circuit for shutting off a signal in response to a force.
In the shutoff operation test method, the power supply voltage is supplied from the outside, the power supply voltage is changed, and the temperature is not changed.
A method for testing a thermal shutdown operation of a thermal shutdown circuit for confirming at least one of thermal shutdown and operation recovery of the thermal shutdown circuit is proposed.

[0009]

The thermal cutoff temperature and the operation recovery temperature are determined by the resistance ratio between the power supply voltage dividing resistor and the output voltage feedback resistor and the power supply voltage. If the power supply voltage is sufficiently stabilized, this power supply voltage can be divided and used as the reference power supply for the thermal cutoff circuit. Done.

In the present invention, the heat cutoff and the heat cutoff of the heat cutoff circuit are performed.
For testing circuit operation of at least one of
If, instead of changing the temperature, changing the power supply voltage supplied from the outside, rows and equivalent circuit operation when the temperature changes
Let me know. As a result, without using a thermostat ,
Quick and accurate thermal shutdown operation and operation recovery without
Of can be inspected at least one.

The test can be performed without changing the temperature.
In the case of a thermal shutdown circuit with thermal history,
Cooling must be performed to confirm that operation is always restored.
It is no longer necessary.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Referring to FIGS. 1 to 3, an embodiment of a method for testing the thermal cutoff operation of a thermal cutoff circuit according to the present invention will be described.

FIG. 1 shows a method for testing a thermal cutoff operation according to the present invention .
FIG. 4 is a circuit diagram showing an embodiment of a heat cutoff circuit having a heat hysteresis characteristic as a target to which is applied . The positive input terminal of the comparator 5 is connected to the power supply 7 via the resistor 2 and
It is connected to the ground 11 via the resistor 1. The positive input terminal of the comparator 5 is also connected to the output terminal of the comparator 5 via the resistor 4. On the other hand, the negative input terminal of the comparator 5 is connected to the power supply 7 via the resistor 3 and to the ground 11 via one or more series diodes 6.

The positive input terminal voltage 8 of the comparator 5 is normally set lower than the negative input terminal voltage 9. Therefore, the comparator output voltage 10 becomes approximately the ground potential 11, and the positive input terminal voltage 8 Vin +
It is represented by R ₁ , R ₂ , R ₄ are resistors ₁ , ₂ , 4,
, VB is the power supply voltage.

[0015]

(Equation 1)

At the temperature T, the negative input terminal voltage 9 Vin-
Is represented by Expression 2. n is the number of series diodes, V
F is the forward voltage per diode at the reference temperature T ₀ , α
Is the temperature coefficient of the forward voltage of the diode.

[0017]

(Equation 2)

[0018] The semiconductor device and the like incorporating the thermal shutdown circuit, abnormal operation or by heating from ambient, at a shutdown temperature above T _1, alpha <0. Therefore, the negative input terminal voltage 9 positive input terminal voltage 8 and the comparator output voltage 10
V ₀ is approximately the power supply voltage VB. Using the comparator output voltage 10 V ₀ , a cutoff state is realized.
The simplest shutoff circuit has a comparator output voltage of 10 V
_{In this method} , the transistor 12 is turned on by ₀ , the output 13 is grounded, and the subsequent device is stopped.

[0019] The comparator output voltage 10 V ₀ and the other input signal and logical operation method for stopping the subsequent device is also conceivable. The operation of the device is stopped by these methods, and the circuit device and equipment connected thereto are protected.

Positive input terminal voltage 8 Vin in cut-off state
+ Is represented by Expression 3.

[0021]

(Equation 3)

The voltage of Equation 3 is higher than the voltage of Equation 1, cold circuit, until the lower recovery temperature T ₂ than the cut-off temperature T _1, the comparator output voltage 10 V ₀ maintains the high voltage. Therefore, a thermal oscillation operation can be prevented.

[0023] The temperature of the circuit is reduced, and falls below the recovery temperature T _2, the comparator output voltage 10V ₀ is returned to the normal ground voltage.

From equations (1), (2) and (3), the resistance 1,
The ratio between the resistance values of 2 and 4 is represented by Expression 4.

[0025]

(Equation 4)

The feature of this circuit is that by changing the power supply voltage 7 VB supplied from the outside, a circuit operation equivalent to a case where the temperature is changed can be realized. Temperature T
Equation 5 shows a power supply voltage VBT that performs a circuit operation equivalent to the following. VB ₀ is the normal environment for example, the power supply voltage at room temperature.

[0027]

(Equation 5)

When the power supply voltage 7 is changed using this,
Without changing the temperature, the thermal shutdown circuit heat blocking and operation times
At least one of the reinstatements can be tested. Therefore, the number of inspection steps can be reduced, and the manufacturing cost can be reduced.

Consider the feasibility of a specific circuit. In order to keep the input terminal voltage of the comparator 5 out of the insensitive input voltage range of the comparator 5 and to minimize the number of elements, the number of diodes is set to n = 3. Power supply voltage VB = 5V, VF
= 0.735V, α = -1.63 × 10 minus the third power V
/ ° C, T ₁ = 160 ° C., T ₂ = 130 ° C., and T ₀ = 25 ° C., the resistance ratio of the resistances 1, 2, and 4 is as shown in Expression 6.

[0030]

(Equation 6)

Since the resistors 1, 2 and 4 having such a ratio can be formed by the same process, the resistance temperature coefficients can be made uniform. At this time, the power supply voltage supply voltage corresponding to T ₁ is equivalent VB ₁ = 7.138V, the T ₂ are VB ₂ =
It becomes 6.528V. Since these are larger than the normal power supply voltage range and smaller than the voltage that causes element destruction,
Can be put to practical use.

FIG. 2 shows a method for testing a thermal cutoff operation according to the present invention .
FIG. 9 is a circuit diagram showing an embodiment of a heat cutoff circuit having no heat history characteristic as a target to which is applied . This embodiment is a circuit in which the output feedback resistor 4 is removed from the embodiment of FIG. If the comparator output 10 is latched and used outside this circuit, a thermal cutoff circuit that does not automatically recover can be realized.

Also in this circuit configuration, the heat cutoff temperature is
It is determined by the resistance ratio between the resistors 1 and 2. If the power supply voltage is changed, the thermal cutoff operation characteristics can be confirmed at room temperature without changing the temperature.

FIG. 3 shows a method for testing a thermal cutoff operation according to the present invention .
FIG. 3 is a block diagram of a three-phase motor drive circuit using a thermal cutoff circuit as an object to which the present invention is applied . The dotted frame in the drawing indicates the range of the semiconductor device. Normally, three-phase motor 21
Are driven according to the drive signal 22. When the temperature of the semiconductor device itself or the temperature of the three-phase motor 21 rises abnormally, the output of the three-phase motor 21
In addition, burning of the three-phase motor drive circuit is prevented.

[0035]

According to the present invention, by changing the power supply voltage supplied from the outside , at least one of the thermal shutdown and the operation recovery of the thermal shutdown circuit can be performed without changing the temperature of the element.
The inspection process can be reduced, and the manufacturing cost can be reduced.

[Brief description of the drawings]

FIG. 1 is a diagram showing a method for testing a thermal shutdown operation according to the present invention;
FIG. 4 is a circuit diagram showing an embodiment of a heat cutoff circuit having a heat hysteresis characteristic as an object .

FIG. 2 is a diagram showing the application of the thermal cutoff operation test method according to the present invention;
FIG. 4 is a circuit diagram showing an embodiment of a heat cutoff circuit having no heat history characteristic as an object .

FIG. 3 is a diagram illustrating a method for testing a thermal shutdown operation according to the present invention;
FIG. 4 is a block diagram of a three-phase motor drive circuit using a heat cutoff circuit as an object .

FIG. 4 is a circuit diagram showing an example of a conventional heat cutoff circuit.

[Explanation of symbols]

 1, 2, 3, 4, 17 Resistance 5 Comparator 6, 18 Temperature detection diode 7 Power supply 8 Positive input terminal voltage 9 Negative input terminal voltage 10 Comparator output voltage 11 Ground 12 Transistor 13 Output 16 Band gap circuit 19 Semiconductor circuit drive power supply Reference Signs List 20 motor power supply 21 three-phase motor 22 motor drive signal

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Tatsuo Shimura 3-1-1 Sachimachi, Hitachi, Ibaraki Pref. Hitachi, Ltd. Hitachi Plant (72) Inventor Hitoshi Matsuzaki 3-1-1 Sachimachi, Hitachi, Ibaraki No. 1 Hitachi, Ltd. Hitachi Plant (72) Inventor Toshihiko Yamakawa 3-10-2 Bentencho, Hitachi City, Ibaraki Prefecture Inside Tachihara-cho Electronic Industry Co., Ltd. (56) References Japanese Utility Model Application Sho 63-149147 (JP, U)

Claims (1)

(57) [Claims] 1. A reference voltage circuit for dividing a power supply voltage to generate a reference voltage, a temperature sensor circuit, a comparison circuit for comparing the output of the temperature sensor and the reference voltage, and a circuit for interrupting a signal according to the output of the comparison circuit In the method for testing the thermal cutoff operation of the thermal cutoff circuit, the method further comprising: supplying the power supply voltage from the outside, changing the power supply voltage, and changing the temperature without changing at least one of the thermal cutoff and the operation recovery of the heat cutoff circuit. Check that
Test method of thermal shutdown operation of thermal shutdown circuit .