JPH0588430B2 - - Google Patents

Description

[Detailed description of the invention]

[Technical Field] The present invention relates to a driving element testing method for preventing secondary failures that occur when the driving element fails in a circuit using a driving element using a transistor. [Prior Art] FIG. 1 is a circuit diagram showing a first conventional example of a conventional drive element testing method, in which 1 is a power supply terminal, 2 is
3 is a drive element made of a transistor that opens and closes to determine whether or not to supply power to the load 2; 4 is a temperature sensor provided in the load 2; 5 is a temperature sensor of the temperature sensor 4; Abnormal temperature detection terminal. In this circuit configuration, when the drive element 3 is in a conductive state, power is supplied from the power supply terminal 1 to the load 2, and when the drive element 3 is in a cut-off state, power to the load 2 is stopped. This detection of the presence or absence of abnormality in the drive element 3 is performed by detecting the abnormal temperature of the load 2 with the temperature detector 4. FIG. 2 is a circuit diagram showing a second conventional example, in which 1 is a power supply terminal, 2 is a load, 3 is a drive element,
These are similar to the first conventional example. 6 is a current detection resistor provided between the power supply terminal 1 and the load 2; 7 is an overcurrent detection circuit provided in the current detection resistor 6; and 8 is an overcurrent detection terminal of the overcurrent detection circuit 7. Here again, as in the first conventional example, the drive element 3
The power supply terminal 1 is connected to the load 2 by conducting/cutting off the
The presence or absence of abnormality in the drive element 3 is detected by detecting an overcurrent in the current detection resistor 6 by an overcurrent detection circuit 7. It should be noted that an abnormality in the drive element 3 refers to a state in which power is not supplied to the load 2, that is, a failure in which the drive element 3 continues to be in a cut-off state, and a state in which power continues to be supplied to the load 2, that is, a state in which the drive element 3 is in a conductive state. This is a case of continuous failure. In this way, in the first and second conventional examples, since abnormality detection of the drive element 3 is mainly performed on the load 2 side, it is necessary to rely on whether or not the current is supplied to the load 2, or on the supply state. Therefore, the following drawbacks arise. This is because if the drive element 3 continues to be in a cut-off state, no power will be supplied to the load 2, so no failure will occur in the load 2, but if the drive element 3 continues to be in a conductive state, overpower will be applied to the load 2. , secondary failures such as heat generation and disconnection of the load 2, or performance deterioration occur. [Object of the Invention] An object of the present invention is to solve the conventional drawbacks by employing a drive element testing method that directly detects abnormalities in the drive element. [Summary of the Invention] In order to achieve this object, the present invention connects a power supply terminal, a load, and a drive element made of a transistor in series, and supplies power to the load by conducting or cutting off the drive element. In the circuit for determining whether or not the drive element is supplied, a detection circuit for detecting the collector voltage of the driving element is provided, and a conduction/cutoff mechanism for determining whether or not to supply power to the load is arranged for the series connection, Testing the conduction/cutoff of the drive element in a state where the conduction/cutoff mechanism is cut off and no power is supplied to the load, and the drive element becomes conductive or cut off depending on the collector voltage of the drive element at that time. It is characterized by detecting continuous failures. [Example] An example will be described below with reference to the drawings. Note that the same reference numerals are used for parts that are the same as those in the first and second conventional examples. FIG. 3 is a circuit diagram illustrating a first method according to the invention. In the figure, 1 is a power supply terminal, 2 is a load, and 3 is a drive element made of a transistor that performs an opening/closing operation and determines whether or not to supply power to the load 2.
These are connected in series. The following are circuit components added according to the present invention. 9 is a power supply instruction terminal connected to the drive element 3;
10 is a failure detection terminal of the driving element 3, 11 is a comparator connected to the failure detection terminal 10, and 12 is a comparator 11.
13 is the bias voltage, 14 is the reference voltage connected to
is a resistance, and the bias voltage 13 is applied to the resistance 1
4 to the comparator 11. 15 is a diode, and the comparator 11 is connected to the drive element 3 via the diode 15. The above is the detection circuit for testing the drive element 3 according to the present invention. Reference numeral 16 denotes a switch disposed between the power supply terminal 1 and the load 2 as a conduction/cutoff mechanism for conducting and cutting off power. By turning the switch 16 on and off, power is supplied to the load 2 when the drive element 3 is normal, and power is cut off when the drive element 3 is abnormal. Detection of whether the drive element 3 is normal or abnormal is performed by the detection circuit. The first method implemented with such a configuration is as follows. First, the switch 16 is turned off to cut off the supply of current to the load 2, thereby preventing power from being supplied to the load 2 no matter what state the drive element 3 is in. In this state, the voltage of the bias voltage 13 is applied to the resistor 14.
and is applied to the collector portion of the drive element 3 through the diode 15. At the same time, the voltage of the reference voltage 12 is calculated as follows: collector-emitter saturation voltage of the driving element 3 + forward voltage of the diode 15 < reference voltage 12 < bias voltage 13
maintain it. In this state, a negative signal or a positive signal is supplied to the drive element 3 from the power supply instruction terminal 9, a voltage comparison between the collector voltage of the drive element 3 and the reference voltage 12 is performed by the comparator 11, and the signal is sent to the failure detection terminal 10. The normality or abnormality of the driving element 3 is detected by outputting the signal. By supplying a negative signal or a positive signal to the drive element 3 from the power supply instruction terminal 9 in this manner, the normal or abnormal state of the drive element 3 can be detected from the output of the failure detection terminal 10. The output state of the failure detection terminal 10 in this case is tabulated as follows.

〔Effect of the invention〕

As explained above, the present invention provides a detection circuit that detects the collector voltage of the drive element, and also arranges a conduction/cutting mechanism for the series connection to determine whether or not power is supplied to the load. The conduction/cutoff mechanism of the drive element is tested in a state where the conduction/cutoff mechanism is cut off and no power is supplied to the load, and the collector voltage of the drive element at that time determines that:
Since a failure in which the driving element continues to be in a conductive state or a disconnected state is detected, the following effects can be achieved. In the case of a drive element failure where the drive element continues to be in a conductive state due to overpowering of the load, which causes a secondary failure called load failure, conventionally the detection configuration was mainly on the load side. Since the failure of the element cannot be detected, the above 2.
However, in the present invention, since the drive element can be tested independently without supplying power to the load, it is possible to prevent the secondary failure of the load from occurring. Because this effect can be obtained, it is useful for motor drive circuits that have loads that are at risk of generating heat, characteristic deterioration, wire breakage, etc., head drive circuits in printers, hammer driver circuits, solenoid driver circuits, etc. can be used.

[Brief explanation of the drawing]

Fig. 1 is a circuit diagram showing the first conventional example, Fig. 2 is a circuit diagram showing the second conventional example, Fig. 3 is a circuit diagram showing the first method according to the present invention, and Fig. 4 is the first method. FIG. 5 is a flowchart of each state of the driving element according to the second method, and FIG. 6 is a circuit diagram of a plurality of driving element testing methods showing the third method. DESCRIPTION OF SYMBOLS 1...Power supply instruction terminal, 2...Load, 3...Drive element, 9...Power supply instruction terminal, 10...Failure detection terminal, 11...Comparator, 12...Reference voltage,
13...Bias voltage, 14...Resistance, 15...
Diode, 16... switch mechanism.

Claims (1)

[Claims] 1. A power supply terminal, a load, and a drive element made of a transistor are connected in series, and the conduction and
In the circuit that determines whether or not to supply power to the load by interrupting the circuit, a detection circuit that detects the collector voltage of the drive element is provided, and a conduction/cutoff mechanism that determines whether or not to supply power to the load is provided. The drive element is placed in relation to the series connection, and the conduction/cutoff mechanism is cut off to conduct a test for continuity/cutoff of the drive element in a state where no power is supplied to the load, and the collector voltage of the drive element at that time is determined to be A drive element testing method characterized by detecting a failure in which the drive element continues to be in a conductive state or a cut-off state.