JPS5980024A - Interface circuit - Google Patents

Abstract

PURPOSE:To transmit simply an output with high efficiency, by providing switch elements which can be switched alternately at the coil end of the input side and obtaining an impedance matched output signal. CONSTITUTION:When an L-level signal is supplied from a logical circuit 2, a transistor TRTr2 and a TRTr3 are turned on and off respectively. In this case, a current i1 flows and the impedance Z1 of a signal source is also set equal to the impedance Z0 of an input circuit of a transformer T when viwed from the load side. Thus the impedance matching is secured. While, the TRTr2 and TRTr3 are turned off and on respectively when an H-level signal is supplied from the side of the circuit 2. Under such conditions, a current i2 flows and the impedance Z2 of the signal source is set equal to Z0 when viwed from the load side. Thus the impedance matching is ensured.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an interface circuit in a signal output circuit.

The Interfuni 2 circuit, which outputs and outputs signals from the logic circuit through normal switching operations, has a configuration as shown in FIG.

That is, in the Kuko circuit when no base voltage is applied to the transistor Trt (when a 1 rubel signal is applied to the inverter IV1), the output impedance is 7o and the current io is given as an output signal.
When the base voltage is applied to the transistor Trt (in this circuit, when an L level signal is applied to the inverter IV1), the output impedance becomes approximately 0Ω, and there is no impedance difference between it and the next stage control system. Alignment occurs.

On the other hand, when connecting the output signal of a logic circuit to a transmission line, or when connecting a filter to extract only a specific frequency component from the output signal, it is inconvenient for impedance mismatch to occur in the interface circuit. , which requires a particularly complex circuit configuration.

The present invention was made based on the above circumstances, and when the output of a switching circuit is connected to a circuit having a predetermined impedance characteristic, the impedance circuit is
It is intended to be provided with a relatively simple configuration.

For this purpose, the present invention provides an intermediate tap on the input coil of the transformer to connect an input circuit having a predetermined impedance characteristic, and also provides switch elements that are alternately switched at the ends of the input coil. Then, the output (Jζ giving No. 5) is made while matching the impedance.

An embodiment of the present invention will now be described in detail with reference to FIGS. 2 to 4. Here, an intermediate tap t is provided on the input side coil C1 of the transformer 1, to which the input circuit 1 having a predetermined impedance ZO is connected. , respectively switched alternately, e.g. 1 helangister Tr.
The signals from the logic circuit 2 are inverted by the inverters IV2, IVs, and IV4, so that a 1 level signal is alternately given to the transistors 1 and 3. It has become.

Further, a load is connected to the output side coil C2 of the transformer.

In this embodiment, the transformer T has a 1:1 ratio of I! I
! Thought 1: Think as Lance.

In such a configuration, when an L level signal is input from the logic circuit 2, the transistor Trz is turned on and the transistor Trs is turned off. At this time, the third
As shown in the figure, a current 11 flows, and the impedance 71 of the signal source seen from the load side also becomes 7o, achieving impedance matching.

On the other hand, when a 1'' level signal is input from the logic circuit 2, the transistor Trz is turned off, and the transistor T
r3 is turned on. At this time, as shown in Figure 4,
A current 12 flows, and impedance matching is achieved by matching the impedance 7tGZo of the signal source as seen from the load side.

As described above, according to the present invention, in an interface circuit controlled by an output signal from a logic circuit that performs a switching operation, it is possible to obtain an output signal while matching the impedance to a circuit having a predetermined impedance characteristic. The output can be transmitted with high efficiency, and its configuration is simple.As a result, when connecting a logic circuit output signal to a transmission line, or when connecting a filter to extract only a specific frequency component from an output signal, This is a very effective tool.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram showing an example of a conventional interface circuit, Fig. 2 is a circuit diagram showing an embodiment of the present invention, and Figs. 3 and 4 are partial circuit diagrams for explaining operating conditions. be. 1-...Transformer, C1...-Next coil, C2...Secondary side coil, Zo...Impedance, 1...Input circuit, Tr'2, Tr s...Transistor, IVz ,
IVs * IV4 ”・Inverter, 2...Logic circuit. Patent applicant Nobuuki Kobashi, agent of Pioneer Corporation, patent attorney

Claims (1)

[Claims] 1. An interface circuit characterized in that an intermediate tap is provided on the inlet side coil of the Herance to connect an input circuit having a predetermined impedance characteristic, and switch elements that are alternately switched are provided at the ends of the input side coils. .