JPH021607A - Insulating input/output device - Google Patents

Abstract

PURPOSE:To securely drive a control element having a large threshold voltage such as a power FET by converting a state signal from a computer and the like into a large voltage on the secondary side of an insulating transformer by means of a flyback principle. CONSTITUTION:When the pulse like state signal eP is added to a switch SW2, a primary coil L1 is switched to a voltage impression cycle and an open cycle. In the voltage impression cycle, the conduction on the secondary side is prohibited by the diode 20 of the secondary coil L2. In the open cycle, the large voltage is induced to the secondary coil L2 by the flyback principle. The voltage is added to the base of a transistor Q20 through voltage-dividing resistances R20 and R21, and it can control a collector voltage about 1A. Furthermore, a sufficient gate bias can be obtained by using power FET having the high threshold voltage.

Description

[Detailed Description of the Invention] <Industrial Application Field> The present invention relates to an isolated input/output device for insulating and transmitting status signals given from a microcomputer, etc., and driving control elements such as transistors and switches. .

<Prior art> When transmitting status signals from a microcomputer etc. in an insulated manner, for example, a transformer with a winding ratio of 1=1 is used to transmit the status signal given to the primary side to the secondary side. A method is adopted in which the signal is transmitted insulated to drive control elements such as transistors and switches provided on the secondary side. In such a method, since the voltage generated on the secondary side is regulated by the voltage value applied to the primary side, there are restrictions when driving a control element with a large threshold voltage, such as a power FET.

<Problem to be solved by the invention> The technical problem to be solved by the present invention is to
In an isolated input/output device that has a secondary winding, inputs a state g signal to the primary winding, and drives a control element by the voltage transmitted to the secondary side, the voltage applied to the primary side is applied to the secondary side. The purpose of the present invention is to generate a voltage that is not regulated by a voltage value, so that the control element can reliably drive even a control element with a large threshold voltage, such as a power FET.

<Means for Solving the Problems> The configuration of the present invention includes mutual interface means having a primary winding and a secondary winding, and a state signal applied from the outside to cause the primary winding to undergo a voltage application cycle. a first switch means that switches to an open cycle; a second switch means that is connected to the secondary winding and prohibits energization of the secondary side during the voltage application cycle; and a second switch means that is connected to the secondary winding;
a switch control element driven by a voltage induced in the secondary winding when the primary winding is in an open cycle; According to the present invention, the control element is driven based on the above-described structure.

Function> The above technical means works as follows. That is, energization of the secondary side is prohibited during the voltage application cycle of the primary side. During an open cycle, a large voltage is generated in the secondary winding that is not regulated by the voltage value applied to the primary side. By using this voltage, it becomes possible to drive the control element having a large threshold voltage, such as the power FE'r'.

<Embodiment> FIG. 1 is a circuit diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a portion of an apparatus according to another embodiment of the invention. 3 is a transformer as a mutual inductance means consisting of a primary winding L1 and a secondary winding L2; for example, a simple separation type with a 1:1 winding ratio between the primary and secondary windings is used. . 1.2 is a terminal provided on the secondary side, and the line W 1
, W2 are connected to both ends of the secondary winding [72. A series circuit of a load Rds and a DC power supply VS is connected between terminals 1 and 2. One end of the primary winding L is connected to the power supply V
The other end is connected to a switch SW2 configured as, for example, a 1'' L-O-L open collector.

A pulse-like status signal ep is applied to this switch from a microcomputer or the like to turn it on and off. A capacitor 30 and a resistor R30, which are also connected to the primary side, constitute a filter.

D20 is a diode connected to the secondary side of the primary winding L.
It acts as a switch means for prohibiting energization of the secondary side during a voltage application cycle to 1. A resistor R20 and a capacitor C20, which are also connected to the secondary side, constitute a filter circuit. Q20 is a 1-transistor whose collector and emitter are connected between input terminals 1 and 2, and whose base is connected to the connection point between resistors R20 and R21. A Zener diode D21 for absorbing surge voltage is connected between the collector of this transistor and the diode D20 side.

With this configuration, when a pulsed state signal ep is applied to the switch SW2, this causes the primary winding 1! Ll is switched between a voltage application cycle and an open cycle. 1
The secondary winding I, 1 is the secondary winding when the voltage application cycle, 2
energization of the secondary side is prohibited by the diode D20. When the primary winding L1 is in an open cycle, a large, almost unlimited voltage is induced in the secondary winding L2 due to the flyback principle. This voltage is applied to voltage dividing resistors R20 and R21
The current is applied to the base of the transistor Q20 through the transistor Q20, thereby making it possible to control a collector current of about IA, for example.

As shown in FIG. 2, even when using a much higher power FET Q21, such as a threshold voltage of 5 V, compared to a bipolar transistor, a sufficient gate bias can be obtained.

<Effects of the Invention> According to the present invention, a status signal given to the primary side from a computer etc. is transmitted to the secondary side insulated, and the voltage generated on the secondary side is equal to the voltage applied to the primary side. Because of the large voltage that is not regulated by a value, even control elements with large threshold voltages, such as power FETs, can be reliably driven.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of an apparatus according to an embodiment of the present invention, and FIG. 2 is a circuit diagram showing a portion of an apparatus according to an embodiment of the present invention. ■...Transformer, Ll...Primary winding, L2...Secondary winding, D20...Switch means, SW2...Switch, Q20...Transistor, Q21...Power F
ET, Rd...Load, ep...Status signal

Claims (1)

[Claims] mutual inductance means having a primary winding and a secondary winding; first switch means for switching the primary winding between a voltage application cycle and an open cycle according to a state signal applied from the outside; and the secondary winding. a second switch means connected to the secondary winding for inhibiting energization of the secondary side during the voltage application cycle; and a switch control element driven by a voltage induced in the secondary winding, and the control element is driven based on a voltage not regulated by the state signal level induced in the secondary winding. Input/output device.