JPH0259431B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a check circuit for a solenoid drive circuit that checks for a failure in a drive element of a solenoid drive circuit, and for a short circuit or disconnection of a solenoid.

[Conventional technology and problems]

1 and 2 are diagrams showing a conventional example of a solenoid drive circuit, and FIG. 3 is a diagram showing an outline of a drive section of a dot impact printer. In the figure, 1 is a drive control circuit, 2 is a flyback voltage control circuit, 3 is an inverter, S ₁ to S _o are solenoids, Tr1 to Trn, Q ₁ and Q ₂ are transistors,
D ₁ to D _o are diodes, R ₁ to R ₅ are resistors,
S indicates a spring, M indicates a magnet (permanent magnet), A indicates an armature, and P indicates a printing pin.

In FIG. 1, solenoids S ₁ to Sn are
For example, the head of a dot impact printer
It is a magnet, and the transistor Tr1 or
Driven by Trn. When used in a dot impact printer, the drive control circuit 1 selectively controls the transistors Tr1 to Trn to conduct on the basis of a print command, thereby driving the solenoids _S1 to _S0 . dot impact
As shown schematically in FIG. 3, in the printer drive section, normally, an armature A to which a printing pin is fixed is attracted to a magnet M by magnetic attraction force. At this time, the spring S is placed in a state of storing force. For such magnet M, solenoid
S ₁ to S _o are used to remove the magnetic attraction force caused by the magnet M. Solenoid S ₁ to S _o
When is excited, the magnetic attraction is removed, so
The armature A is moved toward the printing surface by the force of the spring S, and printing is performed using the printing pin. Therefore, the duty ratio at which the solenoids S ₁ to S _o are driven is small, and heat generation of the solenoids is guaranteed only when used at that duty. In many cases, if a solenoid is continuously energized, there is a risk of smoke or fire. This often occurs when the transistors Tr1 to Trn, which are solenoid drive elements, are damaged, and the circuit within the dash-dotted line is a check circuit that detects damage to the transistors Tr1 to Trn. In the check circuit, resistors R 1 _and R ₂ are connected in parallel to solenoids S ₁ to S _o via diodes D ₁ to D _o , respectively, and the voltage across resistor R ₁ is applied between the base and emitter of transistor Q ₁ . applied. transistor
Resistors R ₃ and R ₄ are connected to the collector of Q ₁ , and the resistors
The voltage across _R4 is applied between the base and emitter of transistor _Q2 . and transistor Q ₂
A power supply V _L is supplied to the collector of the inverter 3 via a resistor R ₅ and the inverter 3 is connected to the collector of the inverter 3 . Therefore, in the check circuit, when power is flowing to at least one of the solenoids _S1 to _S0 , transistor _Q1 becomes conductive, and as transistor _Q1 becomes conductive, transistor _Q2 also becomes conductive, and the inverter 3
Since the input terminal of the inverter 3 becomes a logic "0" level, the check signal FIR output from the inverter 3 becomes a logic "1". If this check signal FIR is sampled when the drive control circuit 1 is not operating, it becomes logic "1" when the transistors Tr1 to Trn are abnormally energized. The flyback voltage control circuit 2 controls the flyback voltage generated in the solenoids _S1 to _S0 to improve response speed.

Transistor that drives solenoid S ₁ or S _o
Figure 1 shows an example in which NPN type transistors are used as Tr1 to Trn, while Figure 2 shows an example in which PNP type transistors are used as transistors Tr1 to Trn and are connected to the drive power supply side. It is something. According to the structure of the drive circuit shown in FIG. 2, the check circuit does not require the transistor Q ₂ and the resistors R ₃ and R ₄ shown in FIG. 1, and the circuit structure is simplified. The check signal FIR of the check circuit is
Similar to the circuit shown in the figure, when at least one of the transistors Tr1 to Trn is in a conductive state, the logic becomes "1", so when the drive control circuit 1 is not operating, this check signal FIR is By sampling, transistor Tr1
It is also possible to check whether there is abnormal energization of TRN.

However, in the conventional check circuit shown in FIGS. 1 and 2, although it is possible to check for abnormal energization of the transistors _Tr1 to _Trn , which are the drive elements of the solenoids S1 _{to S0} ,
The disadvantage is that it is not possible to check for disconnections in the _SO .

[Purpose of the invention]

SUMMARY OF THE INVENTION It is an object of the present invention to eliminate the above-mentioned drawbacks and to provide a check circuit for a solenoid drive circuit which is capable of checking the solenoid as well as checking the drive element of the solenoid.

[Structure of the invention]

To this end, the check circuit of the solenoid drive circuit of the present invention includes a series circuit of a plurality of sets of solenoids and a solenoid drive element, a drive power source that supplies power to the series circuit, and a drive control circuit that switches and controls the solenoid drive element. In the solenoid drive circuit, one end of a resistor and one end of a diode are connected to each series connection point of the plurality of series circuits, the other end of the resistor is commonly connected to one end of a switching element, and the other end of the resistor is connected to one end of a switching element. is connected to the terminal on the connection side of the solenoid drive element among the terminals of the drive power supply, the other end of the diode is connected to one end of the check resistance circuit, and the other end of the check resistance circuit is connected to the terminal of the drive power supply. A check circuit is provided, which is connected to a terminal on the connection side of the solenoid among the terminals, and in which the check resistance circuit is connected to a level determination circuit, and the level determination circuit is connected to at least one set of the plurality of series circuits. When the solenoid driving element of the series circuit is conductive and the solenoid of the series circuit is not short-circuited, and/or the switching element is conductive and the solenoid of at least one series circuit of the plurality of series circuits is conductive. The determination level is such that it is determined that the switching element is at a predetermined level when the wire is disconnected, and is determined to be not at the predetermined level when the switching element is conductive and all solenoids in the plurality of series circuits are not disconnected. It is characterized by the following:

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 4 is a circuit diagram showing one embodiment of the present invention, and FIG.
The figure shows a check algorithm by the check circuit of the present invention. In Figure 4, the second
The same symbols as in the figure indicate the same as in Figure 2, 4 is the check control circuit, 5 is the comparison circuit, Q ₃
is a transistor, Vr is a comparison reference voltage, and Ra1 to Ran are resistances.

As shown in FIG. 4, the check circuit applied to the present invention includes diodes _D1 to D at each series connection point of a series circuit group of solenoids S1 to _S0 and transistors _Tr1 to Trn that drive them. _o
Connect one end and one end of resistor Ra1 or Ran,
The other ends of the diode D ₁ or D _o are connected in common and connected through the resistors R ₁ and R ₂ to the solenoid S ₁ or S _o.
In addition to connecting the resistors Ra1 to Ran to the side power supply terminal, the other ends of the resistors Ra1 to Ran are connected in common and the transistor
Connect to the power supply terminal of transistor Tr1 or Trn through _Q3 . Then, the voltage across the resistor R ₂ is compared with the comparison reference voltage Vr in the comparator circuit 5. The output of the comparison circuit 5 is sent to the inverter 3, and the output of the inverter 3 is used as the check signal FIR. The comparison circuit 5 includes transistors Tr1 to
When at least one of the transistors Trn is conductive and a current close to the normal drive current flows through the corresponding solenoid _S1 to _S0 , the output becomes logic "0" and all of the transistors Tr1 to Trn The slice level is determined so that the output becomes logic "1" when in a non-conducting state.

The present invention detects defects in drive elements by performing Tests 1 to 3 as shown in FIG.
This detects defects in the drive system of the drive element, short circuits in the solenoid, and disconnections in the solenoid. The check system according to the present invention will be explained below with reference to FIGS. 4 and 5.

In test 1, drive control circuit 1 is a transistor
The check signal FIR is sampled while Tr1 to Trn are not being driven. At this time, transistor _Q3 is also rendered non-conductive. In test 1 at power-on, if the check signal is logic "1", it means that at least one of the transistors Tr1 to Trn is conductive. In this case, the conducting transistor Tr1 or
Trn is determined to be defective. If this is left unattended, the corresponding solenoid S ₁ to S _o will be continuously energized, and as mentioned earlier, there is a risk of smoking or fire from the solenoid S ₁ or S _o , so it is necessary to take measures to disconnect the power supply (V+). Be taken. In test 1 at power-on, if the check signal is logic "0",
Test 2 is then performed.

In test 2, the drive control circuit 1 sequentially drives the transistors Tr1 to Trn one by one.
Sample the check signal FIR during driving.
In this test 2, if the check signal FIR does not become logic "1", the transistors Tr1 to Trn corresponding to the drive signal are not conducting, that is, the drive system is defective, or the corresponding transistor is defective.
Even if Tr1 to Trn are conductive, no voltage is generated across the resistor _R2 , that is, it is determined that the solenoid is short-circuited. In this case, a drive failure alarm is output. In test 2, check signal FIR is logic "0" for all transistors Tr1 to Trn.
If so, then test 3 is performed.

In test 3, transistor _Q3 is made conductive by check control circuit 3 while all transistors Tr1 to Trn are not driven.
Sample the check signal FIR. In this test 3, if the check signal FIR is logic "0", it is determined that the drive circuit is normal. Once it is confirmed that the drive circuit is normal, test 3 is then repeated, or test 2 is performed to monitor the occurrence of subsequent failures. In test 3,
If the check signal FIR is logic "1", test 1 is performed again. Test 1 conducted here
In this case, when the check signal FIR is logic "1", the transistor Tr1
If the check signal FIR is logic "0", it is determined that the solenoid S ₁ or S _o is disconnected, and a drive failure alarm is output. Actions will be taken to That is, if solenoid S ₁ or S _o is disconnected, in test 2, the transistor
The current flowing through the transistors S 1 to S _o through Q ₁ and the resistors Ra ₁ to Ran stops flowing only to the disconnected solenoid S ₁ to S _o , and as a result, the anode potential of the corresponding diode D ₁ to D _o rises. , the output of the comparison circuit 5 is logic "0",
Set the check signal FIR to logic "1". but,
In test 1, unless transistors Tr1 to Trn are defective, solenoids _S1 to S _o are normal;
The check signal FIR becomes logic "0" regardless of the abnormality. Therefore, disconnection of the solenoid is determined based on the results of Test 1 and Test 3.

〔Effect of the invention〕

As is clear from the above description, according to the present invention, by simply adding a simple circuit using a transistor and a resistor to the conventional check circuit, it is possible to prevent not only the failure of the drive element of the solenoid drive circuit but also the failure of the drive system and solenoid. Short circuits and disconnections can also be detected, and since the details of the failure can be analyzed, countermeasures can be taken for each type of failure.

[Brief explanation of the drawing]

1 and 2 are diagrams showing a conventional example of a solenoid drive circuit, FIG. 3 is a diagram showing an outline of a drive section of a dot impact printer, and FIG. 4 is a circuit diagram showing an embodiment of the present invention. , and FIG. 5 are diagrams showing a check algorithm by the check circuit of the present invention. 1...Drive control circuit, 2...Flyback voltage control circuit, 3...Inverter, 4...Check control circuit, 5...Comparison circuit, _S1 to S _o ...Solenoid, Tr1 to Trn, _Q1 , Q ₂ and Q ₃ ... transistor, D ₁ or D _o ... diode, R ₁ or
_R5 and Ra1 or Ran...Resistance, Vr...Comparison reference voltage.

Claims (1)

[Claims] 1. In a solenoid drive circuit comprising a series circuit of a plurality of sets of solenoids and a solenoid drive element, a drive power supply for supplying power to the series circuit, and a drive control circuit for switching control of the solenoid drive element, the plurality of sets of series circuits One end of a resistor and one end of a diode are connected to each series connection point, the other end of the resistor is commonly connected to one end of a switching element, and the other end of the switching element is connected to one of the terminals of the drive power source for the solenoid drive element. The other end of the diode is connected to one end of the check resistance circuit, and the other end of the check resistance circuit is connected to the connection side terminal of the solenoid among the terminals of the drive power source. and a check circuit in which the check resistor circuit is connected to a level determination circuit, and the level determination circuit is configured such that the solenoid driving element of at least one series circuit among the plurality of series circuits is conductive and the check resistor circuit is connected to a level determination circuit. When the solenoid in the series circuit is not shorted,
and/or it is determined that the switching element is at a predetermined level when the switching element is conductive and the solenoid of at least one series circuit of the plurality of series circuits is disconnected; A check circuit for a solenoid drive circuit, characterized in that a determination level is determined such that it is determined that the level is not at a predetermined level when all solenoids in a set of series circuits are not disconnected.