JPH03224311A - Switching circuit - Google Patents

Abstract

PURPOSE:To prevent the change of the duty ratio of an output signal generated at the time of switching by setting the other gate part to the conductive state at the time of the change of the other input signal after the change of a select signal. CONSTITUTION:When a select signal E is changed from the low level to the high level, an inverter circuit 6 generates an inverted signal C in the low level and applies it to the clear input terminal of a flip flop 4. Then, the gate of an AND circuit 7 is closed. When the select signal E is changed from the low level to the high level, a flip flop 5 sends an output signal D to an AND circuit 8 to open the gate of this circuit 8. Since an output signal G sent by switching acquires the rise of an input signal B by the flip flop 5 at this time to open the gate of the AND circuit 8, the duty ratio of the input signal B is surely secured.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present circuit relates to a switching circuit for switching clocks and the like.

[Prior Art] Conventionally, as a circuit for switching input signals such as clocks,
There is a selection circuit. An example of this selection circuit is shown in FIG. Further, a waveform diagram of the selection circuit of FIG. 3 is shown in FIG. 4.

The selection circuit 14 shown in FIG. Select input signal A from among. Then, input signal A is set as output signal F, and output terminal 1
Send to 5. Also, when the selection signal E changes to the "high" state, the input signal A is switched to the input signal B, and the output signal F
Send it out as.

In this way, the conventional selection circuit is a circuit that performs switching control of input signals using selection signals.

[Problem to be solved by the invention]

In the conventional selection circuit, since switching control is performed by the selection signal, there is a problem that the duty ratio of the signal switched depending on the timing, that is, the output signal changes as shown in FIG. 4.

An object of the present invention is to provide a switching circuit that eliminates such drawbacks and prevents changes in the duty ratio of the output signal that occur during switching.

[Means to solve the problem]

According to the present invention, from pulsed first and second input signals,
A switching circuit that selects one of the input signals as an output signal according to a change in a selection signal, the switching circuit comprising: a first gate section that makes the first input signal conductive or non-conductive; and a second input signal; a second gate section that makes the first and second gate sections conductive and non-conductive; a control section that controls whether the first and second gate sections are made conductive or non-conductive according to a change in a selection signal; a first input terminal to which an input signal is applied, and a second input terminal to which an input signal from the second gate section is applied; and a selection section that selects and outputs the selected signal as an output signal, and the control circuit selects one gate section that sends one input signal to one input terminal of the selection section when the selection signal changes. the selection circuit selects the other input terminal when the selection signal changes; and the control circuit selects the other input terminal when a change in the other input signal occurs after the selection signal changes; The feature is that the gate portion of the device is made conductive.

The present invention also provides a switching circuit that selects one of the input signals as an output signal from pulse-shaped first and second input signals by changing a selection signal. a first AND gate comprising a terminal and performing an AND operation between a first input signal applied to the first input terminal and a signal applied to the second input terminal; a second AND gate, which is provided with an input terminal and performs an AND operation between a second input signal applied to the first input terminal and a signal applied to the second input terminal; a control section that sends "high" and "low" signals to the first and second AND gates according to the change; a first input terminal to which an input signal from the first AND gate is applied; and a second input terminal; a second input terminal to which an input signal from the AND gate is applied, and a selection section that selects the input signal of either input terminal as an output signal according to a change in the selection signal; The control circuit causes a second input terminal of one AND gate that sends one input signal to one input terminal of the selection section to be "low" when the selection signal changes, and the selection circuit: The control circuit selects the other input terminal when the selection signal changes, and the control circuit selects the other AND gate when the other input signal changes from "low" to "high" after the selection signal changes. The second input terminal of the controller is set to "high".

〔Example〕

Next, embodiments of the present invention will be described with reference to the drawings.

FIG. 1 is a circuit diagram showing one embodiment of the present invention. 1st
The switching circuit shown in the figure consists of a flip-flop 4.5
, inverter circuit 6, AND circuit 7.8
and a selection circuit 9.

The inverter circuit 6 of such a switching circuit inverts the selection signal E applied to the input terminal 3 to generate an inverted signal C.

The flip-flop 4 includes an input terminal 4a, a clock input terminal 4b, an output terminal 4C, and a clear input terminal. A signal in the "1" state is applied to the input terminal 4a, and an input signal A via the input terminal 1 is applied to the clock input terminal 4b. An inverted signal from the inverter circuit 6 is applied to the clear input terminal.

The flip-flop 5 includes an input terminal 5a, a clock input terminal 5b, an output terminal 5c, and a clear input terminal. A signal in the "1" state is applied to the input terminal 5a, and an input signal B via the input terminal 2 is applied to the clock input terminal 5b. A selection signal E is applied to the clear input terminal via the input terminal 3.

The AND circuit 7 performs a logical product operation between the signal from the output terminal 4c of the flip-flop 4 and the input signal A via the input terminal 1. Then, the calculation result is sent to the selection circuit 9.

The AND circuit 8 performs a logical product operation between the signal from the output terminal 5c of the flip-flop 5 and the input signal B via the input terminal 2. Then, the calculation result is sent to the selection circuit 9.

The selection circuit 9 includes input terminals 9a, 9b, 9c and an output terminal 9d. The AND circuit 7 is connected to the input terminal 9a.
The calculation results from AND are added to the input terminal 9b.
The calculation results from circuit 8 are added. Further, a selection signal E via the input terminal 3 is applied to the input terminal 9c. The selection operation of this selection circuit 9 is the same as the conventional one. Then, the output signal G from the output terminal 9d
is sent to the output terminal 10.

Next, the operation of this switching circuit will be explained with reference to the waveform diagram of FIG.

The signal applied to the input terminal 4a of the flip-flop 4 is fixed at 41''.

Further, the selection signal A applied to the input terminal 3 is turned into an inverted signal C by the inverter circuit 6, and is applied to the clear input terminal of the flip-flop 4. When the input signal A is applied to the clock input terminal 4b of the flip-flop 4 in such a state, the flip-flop 4
Open the gate of D circuit 7. As a result, the AND circuit 7 transfers the input signal A applied to the input terminal 1 to the selection circuit 90.
It is sent to input terminal 9a.

On the other hand, the signal applied to the input terminal 5a of the flip-flop 5 is also fixed at the "1" state. Further, the selection signal E applied to the input terminal 3 is applied to the flip-flop 5.
has been added to the clear input terminal. The clock input terminal 4b of the flip-flop 5 is in this state.
When input signal B is applied to , the flip-flop 4 becomes
Close the gate of AND circuit 7. As a result, the AND circuit 8 prevents the input signal B applied to the input terminal 2 from passing through.

A selection signal E in a "low" state is applied to an input terminal 9c of the selection circuit 9. As a result, the selection circuit 9 selects the input signal A applied to the input terminal 9a and uses it as the output signal G. Then, this output signal G is sent to the output terminal 10.
send to

By the way, when the selection signal E changes from "40-" to the "high" state, the inverter circuit 6 generates the inverted signal C of the "low" state and applies it to the clear input terminal 4 of the flip-flop 4. This closes the gate of AND circuit 7.

At the same time, when the selection signal E changes from low to high, the flip-flop 5 ANDs the output signal.
The signal is sent to circuit 8 and the gate of AND circuit 8 is opened. At this time, the output signal G that is switched and sent out catches the rise of the input signal B by the flip-flop 5, and
Since the gate of the AND circuit 8 is opened, the duty ratio of the input signal B can be ensured. Therefore, changes in the duty ratio of the output signal F generated by the conventional technique can be prevented.

In this way, the switching circuit of this embodiment inputs “
By inputting an input signal to the clock input terminal of a flip-flop fixed to 1P and inputting a selection signal to the clear signal, when switching is performed, the clear signal of the flip-flop becomes "high" and the input signal The flip-flop receives the rising edge of the signal and outputs it, which serves to open the gate of the AND circuit. That is, the input signal is used as the input clock of the flip-flop, and the gate of the AND circuit is opened and closed by taking in the rising edge of the input signal. Therefore, the signal output from the AND circuit makes it possible to switch the input signal while ensuring the duty ratio of the input signal.

〔Effect of the invention〕

As described above, the present invention has the effect of making it possible to switch the input signal while ensuring the duty ratio of the input signal by opening and closing the AND gate.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram showing an embodiment of the present invention, and FIG. 2 is a circuit diagram showing an embodiment of the present invention.
FIG. 3 is a circuit diagram showing an example of a conventional selection circuit, and FIG. 4 is a waveform diagram of the selection circuit shown in FIG. 3. 1 to 3...Input terminal 4.5...Flip-flop 6...Inverter circuit 7.8...AND circuit 9...Selection circuit 1O...Output terminal input signal A Figure 2 Beat 3 Figure 4

Claims (2)

[Claims] (1) In a switching circuit that selects one of the pulse-shaped input signals as an output signal by changing the selection signal, the first input signal is made conductive or non-conductive. a first gate section that makes the second input signal conductive or non-conductive; and a second gate section that makes the first and second gate sections conductive due to a change in the selection signal; A control section that controls non-conduction, a first input terminal to which an input signal from the first gate section is applied, and a second input terminal to which an input signal from the second gate section is applied. , a selection unit that selects the input signal of one of the input terminals as an output signal according to a change in the selection signal, and the control circuit selects the input signal of one of the input terminals as the output signal when the selection signal changes. One of the gates sending to one input terminal of the selection section is made non-conductive, and the selection circuit selects the other input terminal when the selection signal changes, and the control circuit selects the other input terminal when the selection signal changes. A switching circuit characterized in that when a change in the input signal of the other occurs after the switching circuit, the gate of the other becomes conductive. (2) In a switching circuit that selects one of the input signals from pulse-shaped first and second input signals as an output signal by a change in the selection signal,
a first AND gate, which is provided with an input terminal, and performs an AND operation between a first input signal applied to the first input terminal and a signal applied to the second input terminal; a second AND gate comprising a second input terminal and performing an AND operation between a second input signal applied to the first input terminal and a signal applied to the second input terminal; a control section that sends "high" and "low" signals to the first and second AND gates according to a change in the signal; a first input terminal to which an input signal from the first AND gate is applied; a second input terminal to which input signals from the two AND gates are applied, and a selection section that selects the input signal of one of the input terminals as an output signal according to a change in the selection signal; The control circuit sets a second input terminal of one AND gate that sends one input signal to one input terminal of the selection section to "low" when the selection signal changes; , the other input terminal is selected when the selection signal changes, and the control circuit selects the other input terminal when the other input signal changes from “low” to “high” after the selection signal changes. A switching circuit characterized by setting a second input terminal of a gate to "high".