Classifications

• • H—ELECTRICITY
  • H03—ELECTRONIC CIRCUITRY
  • H03K—PULSE TECHNIQUE
  • H03K17/00—Electronic switching or gating, i.e. not by contact-making and –breaking
  • H03K17/08—Modifications for protecting switching circuit against overcurrent or overvoltage
  • H03K17/082—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit
  • H03K17/0826—Modifications for protecting switching circuit against overcurrent or overvoltage by feedback from the output to the control circuit in bipolar transistor switches
• • H—ELECTRICITY
  • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
  • H02H—EMERGENCY PROTECTIVE CIRCUIT ARRANGEMENTS
  • H02H3/00—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection
  • H02H3/08—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current
  • H02H3/087—Emergency protective circuit arrangements for automatic disconnection directly responsive to an undesired change from normal electric working condition with or without subsequent reconnection ; integrated protection responsive to excess current for DC applications

Definitions

• the invention relates to an electronic control circuit, in particular for a printer, which comprises a safety circuit for components at risk from overcurrent or overvoltage, power elements being connected upstream of the effectors and power elements and effectors being designed for pulse operation and the consumers exceeding or falling below the prescribed Current or the prescribed voltage can be switched on or off.
• a number of power elements are used in device electronics, in particular in printer electronics, which are generally operated with a voltage between 30 V and 50 V.
• Such power elements drive the so-called effectors (consumers), such as e.g. Electromagnetic coils in printer assemblies and needle printheads, DC motors and stepper motors.
• Both the power elements and the effectors are usually designed for pulse operation and not for a higher relative duty cycle. Under no circumstances, however, is a 100% relative duty cycle required.
• the present invention is based on the object, while avoiding the disadvantages described, of proposing a fuse within an electronic control circuit, in particular for printers, which allows an effector to be used in the
• the object is achieved in that an effector can be actuated in the operating case and at the same time a reference voltage in the permissible tolerance range can be switched on, when the effector is exceeded, it can be switched off.
• the effector is therefore only activated if its function for the operation of a device, e.g. a printer. In such a case, however, the effector is only energized when the operating voltage is within a predetermined permissible tolerance range.
• the current supply is therefore initially linked to the control and the voltage tolerance range.
• the effector be a Amplifier and a comparator for comparing the reference voltage with the voltage generated by the effector current is connected upstream and that the reference voltage can be generated as a function of two series-connected transistors, of which the upstream transistor can only be switched through with an operating voltage within the permissible tolerance range and the downstream transistor only can be switched through when the transistor is switched on, in order to generate the reference voltage.
• the upstream transistor can only be switched through with an operating voltage within the permissible tolerance range and the downstream transistor only can be switched through when the transistor is switched on, in order to generate the reference voltage.
• CSMO surface-mounted devices
• Another improvement of the invention provides that the upstream transistor can only be switched through if an upstream, retriggerable monostable multivibrator is triggered within a set time by the connected effector control. As a result, the set time for activating the relevant effector is a further prerequisite for the connection of the transistors.
• a further security level is achieved in that the retriggerable monostable multivibrator is connected to the upstream transistor via an AND gate and in that the AND gate is connected to a separate voltage monitor. Accordingly, a voltage good message and the control of the relevant component are further prerequisites for the control of the upstream transistor.
• Another improvement of the invention is that the
• Comparator and the resistors generating the reference voltage form an integrated component.
• the area of application of the invention can be designed according to additional features such that a transistor which can be switched by the operating voltage within the permissible tolerance range and the transistor connected downstream of this are assigned to an effector or a group of effectors.
• the single figure of the drawing shows the control circuit according to the invention in a simplified representation.
• the effector CD can be a component of any electronic control circuit and consists of an inductor with a very low ohmic resistance within a printer control.
• the effector CD can therefore also consist of the winding of a direct current motor, a stepping motor or the electromagnetic coil of a wire print head for a matrix wire printer.
• a comparator CK) compares the voltage generated at resistor CR3) by the consumer current with the reference voltage set by reference resistors CR1 and R2). If the reference voltage is exceeded, the comparator CK) switches off the effector CD - consumer - via an amplifier CA).
• the circuit section described above means a first security level in order to protect the effector CD from damage or from complete destruction. In normal operation, the comparator CK) will therefore switch on the effector CD via the amplifier CA), ie its transistor CT3 ) .
• the reference voltage CR1 / R2) is only generated when a transistor CTD - of the PNP type - connected upstream of the resistor CRD is switched on. In the event that the transistor CTD blocks, the reference voltage CR1 / R2) is equal to zero, so that the effector CD is constantly switched off by the comparator CK).
• the transistor CTD is only opened if a transistor CT2) - of the NPN type - upstream of the transistor CTD - whose collector is via a protective resistor C2) is connected to the base of the transistor CTD, is turned on.
• the circuit section described above therefore means a second security level in order to protect the effector CD from damage.
• the transistor CT2) is only opened when the operating voltage is within the permissible dead band and a retriggerable, monostable multivibrator C3), which receives a corresponding signal ( 4 ) from an effector control C5), is triggered.
• the effector control C5) consists of the printer control for a printer.
• the transistor (T2) is blocked via an AND gate CGD which is connected between the multivibrator (3) and the transistor CT2). Since the transistor CT2) is blocked, the transistor CTD is also not activated, so that no reference voltage CR1 / R2) can arise.
• the circuit section described above therefore means a third security level in order to protect the effector CD from damage.
• a voltage monitor C6 which consists of an integrated module with a transistor circuit and which
• Chier input voltage e.g. 5 V
• the voltage monitoring gives a voltage good message or a voltage bad message via the AND gate CGD.
• a resistor C7) is connected between the base of the transistor CT2 ) and the gate CGD, since the gate CGD is a component with an open collector.
• the voltage monitoring C6) now means a fourth security level, around the effector CD protect from harm. It is assumed here that the present safety device is not only intended for the operation of the corresponding device, ie for the control of a printer, but also for its test phases in which special switching states can occur.

Landscapes

• Accessory Devices And Overall Control Thereof (AREA)
• Dot-Matrix Printers And Others (AREA)
• Emergency Protection Circuit Devices (AREA)
• Electronic Switches (AREA)
• Dc-Dc Converters (AREA)
• Protection Of Static Devices (AREA)

Priority Applications (2)

Applications Claiming Priority (2)

Publications (1)

Family

ID=6303254

Family Applications (1)

Country Status (6)

Families Citing this family (6)

Citations (3)

Family Cites Families (14)

• 1986
  • 1986-06-19 DE DE19863620535 patent/DE3620535A1/de active Granted
• 1987
  • 1987-06-12 WO PCT/DE1987/000274 patent/WO1987007987A1/de not_active Ceased
  • 1987-06-12 EP EP87903855A patent/EP0270622B1/de not_active Expired - Lifetime
  • 1987-06-12 AT AT87903855T patent/ATE85472T1/de active
  • 1987-06-12 JP JP62503584A patent/JPH01500637A/ja active Pending
  • 1987-06-12 DE DE8787903855T patent/DE3784032D1/de not_active Expired - Fee Related
  • 1987-06-12 US US07/163,764 patent/US4897557A/en not_active Expired - Fee Related

Patent Citations (3)

Non-Patent Citations (2)

Also Published As

Similar Documents

Legal Events