JP2522686Y2 - Microcomputer power-on circuit - Google Patents

Description

[Detailed description of the invention] [Industrial application field] The invention relates to a power-on circuit of a microcomputer, and more particularly to a power-on circuit that reduces the current consumption of a battery-driven microcomputer.

2. Description of the Related Art Conventionally, there is an apparatus such as a so-called electronic organizer in which power is turned on by a key switch of an operation keyboard, and processing is performed by software when the power is turned off.

FIG. 3 of the accompanying drawings shows a conventional general power-on circuit (1). In FIG. 3, (2) is a microcomputer, (3) is a CPU, and (4) is a JK flip-flop. The terminal J of the JK flip-flop (4) is connected to the power source (5), and the terminal K is connected to the ground (6). The reset terminal CL is connected to a port (7) of the CPU (3), and the clock terminal CK is connected to a key switch (8) of a keyboard (not shown) and a reset terminal (9) of the CPU (3). I have.

The operation of the JK flip-flop (4) is as shown in the truth table of the separate table 1, and the input of the reset terminal (9) is
In the case of Lo, the output Q becomes Lo and Hi regardless of the input level of the J terminal and the K terminal and the clock input pulse.
When the input of the reset terminal CL is Hi, the output Q becomes Hi and Lo at the falling edge of the clock pulse, and does not change at the rising edge.

As shown in the timing chart of FIG. 4, the reset terminal CL and the clock terminal CK of the power-on circuit (1) in the standby state are set to Hi by the input from the power supply. When the key switch (8) is turned on, the output Q becomes Hi due to the fall (A) of the input level of the clock terminal CK.
Turns on the transistors (10) and (11) to turn on the power of the microcomputer (2),
(3) is reset.

At this time, as shown in the truth table, when the input of the reset terminal CL is Lo, the output Q becomes Lo, and since the power cannot be turned on, the voltage is always supplied to the CPU (3) and the port (7)
Is set to Hi. When the power is turned off, the port output of the CPU (3) is lowered (B) by the built-in software, the input level of the reset terminal (9) is changed to Lo, and the output Q is changed to Lo. ) Turn off (11).

[Problem to be Solved by the Invention] The conventional power-on circuit described above always supplies power to the CPU for system startup. Further, it is necessary to supply a voltage in order to prevent the destruction of the CPU due to the latch when the power is turned on.

Therefore, to reduce current consumption in the standby state,
Has a standby mode, and is limited to those in which the port output is Hi during standby.

In order to reduce the current consumption when the power is turned off as much as possible and eliminate the restriction on the selection of the CPU, the solution is to provide a power-on circuit for microcomputers that extends battery life and expands the design flexibility. The technical problem to be solved arises, and the present invention aims to solve the problem.

[Means for Solving the Problems] This invention has been proposed in order to achieve the above-mentioned object, and activates a micro computer by turning on a transistor of a power supply circuit with an output Q by a clock pulse input to a clock terminal of a flip-flop. The first and second JK flip-flops, the terminal J of the first and second JK flip-flops is connected to a power source, the terminal K is connected to ground, and the second JK flip-flop is connected to the ground.
The port output of the CPU of the micro computer is connected to the clock terminal of the JK flip-flop, and the output Q of the second JK flip-flop is connected to the reset terminals of the first and second JK flip-flops via an integrating circuit. , The output Q of the first JK flip-flop is input to the power supply circuit, and the output Q is inverted by the clock pulse input to the clock terminal of the first JK flip-flop irrespective of the port output. Another object of the present invention is to provide a micro computer power-on circuit characterized by turning on a transistor and starting the micro computer.

[Operation] The second JK in which the port output of the CPU is connected to the clock terminal
The output of the flip-flop becomes Hi by the power supply connection,
The signal is delayed and input to the reset terminals of the first and second JK flip-flops via the integration circuit. When a clock pulse is input to the clock terminal of the first JK flip-flop by operating the key switch, the output Q becomes Hi because the reset terminal input level is Hi, and the transistor of the power supply circuit is turned on to turn on the micro computer. Is started.

When the power is turned off, when the port output of the CPU connected to the second JK flip-flop is lowered, the output becomes Lo at the falling edge, and the reset terminal input of the first and second JK flip-flops becomes Lo. And the first JK
The output Q of the flip-flop is set to Lo, and the transistor of the power supply circuit is turned off.

Further, since the reset terminal of the first JK flip-flop receives the output of the second JK flip-flop via the integration circuit, the first JK flip-flop is connected to the first JK flip-flop when the battery is installed or the main power switch is turned on. Output Q is Hi at the same time
And destruction of the CPU due to the latch-up is prevented.

Embodiment An embodiment of the present invention will be described below in detail with reference to FIGS. 1 and 2 of the accompanying drawings. The parts having the same configuration as the reference numerals used in the conventional example will use the same reference numerals. FIG. 1 is a circuit diagram of a power-on circuit (20), (2) a microcomputer, (3) a CPU, and (4) a first JK.
The flip-flop (hereinafter referred to as FF1) and (21) are the second JK flip-flop (hereinafter referred to as FF2). The port (7) of the CPU (3) is connected to the clock terminal CK2 of the FF2 (21), and the output of the FF2 (21) is supplied to the FF2 (21) and the FF1 ( 4) connected to the respective reset terminals CL1 and CL2.

A reset terminal (9) of the CPU (3) is connected to a subsequent FF1 through a transistor (23) to prevent a latch.
It is connected to the clock terminal CK1 of (4) and the key switch (8). The J terminal of FF1 (4) and FF2 (21) is connected to the power supply (5), and the K terminal is grounded to the earth (6). The output Q of the FF1 (4) is a transistor (1
0) Connects to the power supply circuit (24) configured in (11) and controls on / off of the power supply to the microcomputer (2). Incidentally, (25) is a power switch.

FIG. 2 is a timing chart of each part of the power-on circuit (20), which will be described with reference to a separate truth table shown in the conventional example. First, when the power is turned on by the power switch (25) (C), the output of FF2 (21) becomes Hi, and the inputs of the reset terminals CL1 and CL2 become Hi with a delay of t for a predetermined time by the integration circuit (22). Next, when a clock pulse is inputted to the clock terminal CK1 by the operation of the key switch (8) (D), the output Q becomes Hi due to the fall of the pulse, and the transistors (10) and (11) are turned on, and the microcontroller is turned on. The computer (2) is energized and started. At this time, FF2
The input of the clock terminal CK2 of (21) is Hi regardless of the output Hi / Lo of the port (7) of the CPU (3).

When turning off the power to the microcomputer (2), the port (7) of the CPU (3) is controlled by software.
(E) When the output Q is set to Lo, the reset terminal
The inputs of CL1 and CL2 are delayed by time t and become Lo. Therefore, FF2
The output of (21) becomes Hi, and CL1 and CL2 become Hi.

The present invention can be variously modified without departing from the spirit of the present invention. For example, it is also possible to control the power supply using the output of FF1 (4).

[Effects of the Invention] In the present invention, as described in detail in the above-described embodiment, since the power supply of the CPU is turned off during standby, it is not necessary to provide the CPU with a standby mode. Further, conventionally, the port output has been made impossible to start-up of the power supply in which the L _o CPU in the standby mode, the start-up of the power supply in a state where the indefinite port output, according to the present invention has been input to the clock terminal it can.

Therefore, the current consumption is reduced, and the restriction on the selection of the CPU is eliminated, which can contribute to an improvement in performance and a reduction in cost.

[Brief description of the drawings]

1 and 2 show an embodiment of the present invention. FIG. 1 is a circuit diagram of a power-on circuit, and FIG. 2 is a timing chart of the circuit. 3 and 4 show a conventional example, and FIG.
FIG. 4 is a circuit diagram of a power-on circuit, and FIG. 4 is a timing chart of the circuit. (2) Microcomputer (3) CPU (4) First JK flip-flop (7) Port (10) (11) Transistor (20) Power-on circuit (21) …… the second JK flip-flop (22) …… the integration circuit, (24) …… the power supply circuit

Claims (1)

(57) [Scope of request for utility model registration] 1. A power supply circuit for starting a micro computer by turning on a transistor of a power supply circuit with an output Q by a clock pulse input to a clock terminal of a flip-flop, comprising a first and a second JK flip-flop. The terminal J of the second JK flip-flop is connected to the power supply, the terminal K is connected to the ground, the port output of the micro computer CPU is connected to the clock terminal of the second JK flip-flop, and the second JK flip-flop is connected to the clock terminal of the second JK flip-flop. The output of the flip-flop is connected to the reset terminals of the first and second JK flip-flops via an integrating circuit, the output Q of the first JK flip-flop is input to the power supply circuit, and the clock terminal of the first JK flip-flop is connected. In response to a clock pulse input to the The turns on the transistor of the power supply circuit in inverted power-up circuit of the microcomputer, characterized in that to activate the microcomputer.