JPS5832534B2 - Control circuit with microprocessor - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a control circuit with a one-chip microprocessor.

In recent years, the application of microprocessors (hereinafter referred to as CPUs) to various control devices has become popular.
Chip CPUs are increasingly being used in home appliances as their prices fall.

An example of this is its application to fully automatic washing machines.

This is intended to replace the conventional mechanical timer, and allows the CPU to execute operating procedures corresponding to predetermined keys.
It is stored in the internal ROM, and the loads such as the motor, drain valve, water supply valve, etc. are operated by the CPP output.

However, when controlling a load using the CPU output, a practical problem arises when the power switch is turned on.

The present invention will be described in detail below with reference to the schematic diagram of FIG. 1 (FIG. 1 shows only a part of the circuit showing application to a fully automatic washing machine).

First, when voltage is applied to the circuit by turning on the switch 1, the rectifier 3 connected to the secondary side of the transformer 2,
Due to the function of the smoothing capacitor 4, a DC voltage appears between E and A.

This voltage is the load 5 of the washing machine (e.g. motor, drain valve,
This is the gate voltage for driving the bidirectional thyristor 6 for controlling the water supply valve, etc. (although there are a plurality of them, only one is shown here to simplify the explanation).

On the other hand, a voltage held at a predetermined value by the resistor 7, transistor 8, and Zener diode 9 is applied as a power supply voltage to the CPU10 (the CPU is described as an N-channel type in the figure).

After a certain period of time has elapsed, the CPU 10 outputs a predetermined signal to each output port in accordance with an operating procedure previously stored in the CPU's internal memory using a signal from an input circuit (not shown).

For example, when driving the load 5, the output port A becomes H level, and by operating the transistor 11, the bidirectional thyristor 6 is fired, and the load 5 is driven.

In addition, in the figure, 12 is a resistor for limiting the gate current, and 13 is a CP.
A resistor is shown to limit the output current from the U output port.

In this way, no problem occurs after a certain period of time has elapsed, but a practically undesirable problem occurs within several tens of m5ec after the switch 1 is turned on.

This state will be explained using FIG. 2.

In the figure, the vertical axis indicates voltage, and the horizontal axis indicates elapsed time after turning on the switch.

In other words, this figure shows how the voltages at each part rise, where a is the voltage between E and A (gate voltage of the bidirectional thyristor 6) in FIG. 1, b is the power supply voltage of the CPU 10, and C
is the output port of the CPU 10 (for example, the port in Figure 1)
shows the voltage.

As the E-A voltage a rises, the power supply voltage of the CPU 10 also rises, and when the voltage rises to a certain voltage level, if the reset terminal (not shown) of the CPU 10 is at L level, the memory inside the CPU is are all cleared and all output ports become L level.

(Hereinafter referred to as "initial clear") However, even if the reset terminal is at L level, if the CPU power supply voltage is low, initial clear will not occur and the output port level will become unstable and sometimes become H level. There is.

In FIG. 2, the voltage C indicates this, and the voltage V1 rises to the extent that the initial clear is applied, and when the initial clear is applied (at time 1), the output port becomes L level and becomes stable.

When the output port becomes H level in this manner, for example, when the output port becomes H level in FIG. 1, the transistor 11 is driven, the bidirectional thyristor 6 is turned on, and the load 5 is driven.

This is the same for all output ports, and if the water supply valve, drain valve, motor, etc. are each controlled by separate bidirectional sysrisks, such as in a washing machine, all of them will enter at the same time, sometimes causing a whirring sound. Naturally, a large inrush current may flow and destroy circuit components.

In a commonly used circuit like the one shown in Figure 1, malfunctioning of the load when the switch is turned on poses problems such as loud noises in washing machines, as well as issues with component reliability. There were also disadvantages.

In view of this, the present invention provides an inexpensive control circuit that solves the problems that occur when a switch is turned on.

A second purpose is to solve the problems that occur when the switch is turned on, and at the same time to obtain a control circuit that takes into account the gate characteristics of the bidirectional thyrisk.

A specific example will be explained below. One embodiment is shown in FIG. 3, and the numbers 1 to 130 in the figure correspond to the same numbers in FIG. 1, and their explanation will be omitted.

The feature of the present invention is to solve the problem when the switch 1 is turned on by adding a circuit indicated by 14 in the figure.

A detailed explanation including FIG. 4 will be added below.

Note that FIG. 4 corresponds to FIG. 2 and shows the voltage rise in each region after the switch is turned on. When switch 1 is turned on, the terminal voltage of the capacitor 4 (curve a in FIG. 4) increases, At the same time, the CPU power supply voltage (curve b in FIG. 4) also increases.

On the other hand, as the terminal voltage of capacitor 4 rises, the terminal voltage of capacitor 16 also rises, and when it rises to a certain level, transistor 17 is activated.

By the operation of this transistor 17, transistor 1
9 also operates instantaneously, applying a voltage to the gate circuit of the bidirectional zyristor 6 (curve d in FIG. 4).

That is, the voltage is supplied to the gate circuit of the bidirectional thyristor 6 with a delay with respect to the application of the power supply voltage of the CPU 10 (curve b in FIG. 4).

As a result, the CPU output port, for example, the port, becomes H level before the initial clear is applied, and even if the transistor 11 is driven, the bidirectional thyristor 6
does not ignite, making it possible to prevent the load 5 from malfunctioning.

The delay time t2 of the voltage curve d in FIG. 4 can be freely selected by adjusting the values of the resistor 15 and capacitor 16, but in a practical circuit, a value of 50 msee or less is appropriate.

In FIG. 3, reference numeral 18 indicates a resistor for limiting the collector current of the transistor 1γ, and reference numeral 20 indicates a resistor for limiting the emitter current of the transistor 19.

Further, the delay circuit indicated by 14 is not limited to the embodiment shown in FIG. 3, and may be a single transistor circuit as shown in FIG. 5, for example.

In this circuit, a voltage is applied to the gate of the bidirectional zyristor 6 by switching the transistor 23, and the delay time is determined by the capacitor 20 and the resistor 21.

22 indicates a current limiting resistor.

The gist of the present invention is to supply voltage to the gate circuit of the bidirectional zyristor 6 after the time period during which the output port of the CPU 1Q is at an unstable level (time t in FIG. 2, time 1+ in FIG. 4) has elapsed. In particular, it does not restrict the specific circuit for that purpose.

Note that until now, the voltage applied to the gate of the bidirectional thyristor 6 within time t3 in FIG. 4 is zero, and at time t.
Although it has been explained that a predetermined voltage is applied for the first time at time t1, it does not necessarily have to be zero before time t1, and the point is that even when the transistor 11 operates, the gate is applied only to cause the bidirectional thyristor 6 to fire. The gist of the present invention is not impaired as long as the voltage is at a level that does not supply current.

The second object of the present invention is focused on this point.

The second purpose is to serve both as a constant voltage circuit and a delay circuit to keep the power supplied to the gate of the bidirectional thyristor 6 constant.
Our goal is to provide inexpensive and highly reliable circuits.

The bidirectional thyristor 6 has a predetermined suitable gate range, and if it is outside the range, it will result in failure of ignition, failure of commutation, or destruction of the element, so sufficient care must be taken in designing.

When driving a bidirectional thyrisk using direct current, this suitable range is narrow (particularly in the examples shown in Figures 1 and 3, fluctuations in the power supply voltage directly affect the gate load curve of the bidirectional thyrisk). (variation in the load point), so it is currently difficult to use it in practice when temperature characteristics are also taken into account.

As a countermeasure to this problem, when driving a bidirectional cyrisk with direct current, a constant voltage circuit is usually used.

The present invention focuses on this point and attempts to obtain an inexpensive control circuit by utilizing such a constant voltage circuit and making it also function as a delay circuit.

FIG. 6 shows this circuit side, showing only 14 portions of FIG. 3.

A constant voltage circuit is composed of a resistor 24, a constant voltage diode 25, and a transistor 26, and a capacitor 27 and a resistor 24
This causes a delay.

The resistor 28 is used to suppress the charge discharge current of the capacitor 27, but is not necessary when the capacitance of the capacitor 27 is small.

In such a circuit, how the voltages at each part rise are as shown in FIG.

a in the figure. b and c correspond to FIG. 4, and d indicates the output of the transistor 26, that is, the voltage applied to the gate circuit of the bidirectional thyristor 6.

At time t1 when the initial clear of CPU10 is applied, ■2 is applied to the gate of the bidirectional thyristor 6, but even if the transistor 11 (Fig. 3) operates, the bidirectional thyristor 6 is not activated at this voltage V2. The values of the resistor 24 and the capacitor 27 in FIG. 6 are determined so as not to ignite, and the value of the resistor 12 in FIG. 3 is determined.

By configuring as above, it is possible to solve the problem of turning on the switch and at the same time keep the power supplied to the gate constant. When driving a bidirectional circuit with direct current, the design is easy and reliable. It is possible to improve performance at low cost and has great practicality.

Although all the explanations have been made regarding N-channel CPUs, the present invention is not limited to this, and can also be applied to circuits other than those using bidirectional silices.

Naturally, the application is not limited to washing machines, but can be applied to any control equipment using a CPU.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a general control circuit equipped with a microprocessor, FIG. 2 is a diagram showing the voltage rise characteristics of each part in the same circuit, and FIG. 3 is a diagram showing an embodiment of the control circuit according to the present invention. FIG. 4 is a diagram showing the voltage rise characteristics of each part in the same circuit, FIG. 5 is a diagram showing a modification of the main part of the circuit in FIG. 3, and FIG. 6 is a circuit diagram according to another embodiment of the present invention. , FIG. 7 is a diagram showing the voltage rise characteristics of each part of a control circuit equipped with the same circuit. 5...Load, 6...Bidirectional Sairisk, 10...Microprocessor, 11...
...Transistor, 14...Delay circuit.

Claims (1)

[Claims] In a control circuit that uses an 11-chip microprocessor and operates a bidirectional sirisk by driving a transistor connected to the output terminal of this microprocessor,
A control circuit comprising a microprocessor configured such that a gate power supply for the bidirectional thyrisk is delayed compared to a power supply for the microprocessor and is configured to have a constant voltage in a steady state.