JPS6043726A - Power supply circuit for electronic parts - Google Patents

Abstract

PURPOSE:To prevent a malfunction of a load and a wrong display of a display element by cutting off the power supply feed path to the load in case the power supply voltage of the load which is driven based on the output of a microcomputer is lowered less than a prescribed level. CONSTITUTION:A power supply voltage breaking circuit 8 is connected to a power supply voltage feed path led to a load 6 and a display element 7 from a DC power supply 1. For the circuit 8, the feed or cut-off of the power supply voltage is controlled to the load 6 and the element 7 through a voltage level sensor circuit 9 which detects the level of voltage VD applied to a microcomputer 4 and has different types of actuation is response to the level of voltage VD higher or lower a prescribed level. In case the voltage VD does not reach a fixed level like a case immediately after a power supply switch 2 is applied, the feed of the power supply voltage is cut off to the load 6 and the element 7. Thus these load 6 and element 7 have no malfunction.

Description

Detailed Description of the Invention (a) Technical field The present invention relates to a power source for electronic components that prevents load malfunctions and display element erroneous display that occur when a power switch is turned on or when the power supply voltage drops. Regarding circuits.

(b) Prior art Recent microcomputers (hereinafter referred to as "microcomputers")
are used in many electronic devices, such as automatic air conditioners, which often drive electronic components such as loads (for example, solenoids) and display elements based on the output of a microcomputer.

On the other hand, power supply circuits used to drive these electronic components are often connected as shown in FIG. In the figure, 1 is a DC m source, 2 is a TIE source switch,
3 is a constant voltage circuit; 4 is a microphone that operates by receiving a constant voltage supply from the constant voltage circuit 3; 5 is a drive unit that drives a load 6 and a display element 7, which are composed of various electronic components, based on the output of the microcomputer 4; When the power switch 2 is turned on, the load 6 and the display element 7 are driven based on the output signal of the microcomputer 4.

FIG. 2 shows another example of a conventional power supply circuit for electronic components. In this example, as can be seen from the figure, a load 6 and a display element 7
A power supply voltage supply line L is connected to the output side of the constant voltage circuit 3, and the load 6 and the display element 7 are driven based on the output signal of the microcomputer 4 in the same manner as in the example shown in FIG. .

Now, in the above circuit, the power supply voltage vD to the microcomputer 4 gradually increases when the power switch 2 is turned on at time t1, as shown in FIG. Thereafter, when the power switch 2 is turned off at time t4, the value decreases at that point, and becomes zero at time t6.

By the way, in order to operate the microcomputer 4 normally, a power supply voltage higher than a certain constant voltage level l-1 (corresponding to the voltage level v1 at times t2 and t5 in Fig. 3) is required, but when the power switch 2P is turned on, If the power supply voltage does not reach the minimum voltage level V□ required for operation, as immediately after, or if the power supply voltage drops below the voltage level vI due to driving many loads at once, the microcontroller 4
operation becomes unstable. Therefore, there is a problem that an abnormal signal is output from the microcomputer 4, and as a result, the load 6 malfunctions or the display element 7 displays an erroneous display.

(c) Object and structure of the invention The present invention has been made in view of the above points, and provides a power supply circuit that supplies a power supply voltage to a microcomputer and a load driven based on an output signal of the microcomputer. The purpose is to prevent load malfunctions and display element display errors that occur when power is turned on or when the power supply voltage drops.To this end, the power supply voltage supply path from the power supply to the load is closed when the power supply voltage is below a specified level. It is designed to shut off.

) Example The present invention will be explained below based on the drawings.

FIG. 4 shows a power supply circuit for an electronic component according to the present invention connected to a microcomputer control section, and in the figure, the same reference numerals as in FIG. 1 indicate the same parts. In this embodiment, a power supply voltage cutoff circuit 8 that supplies or cuts off the supply of power supply voltage is connected to a power supply voltage supply path from a DC power supply 1 to a load 6 and a display element 7.
The original voltage cutoff circuit 8Vi senses the level of the power supply voltage VD to the microcomputer 4 and sets the voltage level to the predetermined voltage level Vs.
(See Figure 3)? The load 6 and the display element (
Control is performed to supply or cut off the power supply voltage to the load 7. The rest of the configuration is the same as the conventional example shown in FIG.

Now, what happens when the level of the power supply voltage VD to the microcomputer 4 is a constant voltage and has not reached the level v1, as is the case immediately after the switch 2 is turned on? Then, the supply voltage from the DC power supply 1 to the load 6 and the display element 7 is cut off by the power supply voltage cutoff circuit 8 via the pressure level sensing circuit 9. Therefore,
Even if the microcomputer 4 outputs an abnormal signal, the load 6 and the display element 7 do not operate, so there is no possibility of the load 6 malfunctioning or the display element 7 erroneously displaying information.

FIG. 5 shows another embodiment in which a power supply circuit for an electronic component according to the present invention is connected to a microcomputer control section.
In this embodiment, the input terminal VB to the constant pressure circuit 3 and the output voltage VD have a constant relationship in the transient state when the power switch 2 is on and off, and the voltage level 4 is The circuit 9 is connected to the input terminal of the constant voltage circuit 30. In this case, if the input terminal VB falls below the minimum voltage level necessary for normal operation of the microcomputer 4 due to driving many loads at once, the circuit will be shut off. Since the load 6'J=- and the display element 7 are not activated by the signal, malfunction of the load 6 and erroneous display of the display element 7 do not occur.

FIG. 6 specifically shows the embodiment shown in FIG. 4, where 10 is a three-terminal constant 1-voltage regulator (corresponding to constant voltage circuit 3 in FIG. 4), and 11 is used as a load. A driving transistor for energizing the solenoid 12 (corresponding to the load 6 in Fig. 4), 131J display LE
A driving transistor D14 (corresponding to the display element 7 in FIG. 4); 15 a constant voltage diode that conducts at a constant voltage higher than a predetermined voltage level from a three-terminal constant pressure regulator lO; 16 a solenoid 12 and a display LED 14; The positive voltage cutoff transistor 17 that controls the supply of power supply voltage to the mmmm positive voltage cutoff transistor 17 is a transistor that controls the on/off state of the transistor [6].

Now, the level of power supply voltage vD is the lowest operating voltage level■!
When it is larger, the microcomputer 4 operates normally, and when its output signal is applied to the bases of the driving transistors 11 and 13, the driving transistors 11 and 13 become conductive. On the other hand, when the level of the output 'R voltage vD of the three-terminal constant voltage regulator 10 is greater than the voltage level 1 shown in FIG. The pressure cutoff transistor 16 becomes conductive. Therefore,
Since the power supply voltage from the DC power supply 1 is supplied to the solenoid 12 and the display LED 14 through the transistor 16, the solenoid 12 is energized and the display LED 14 emits light.

On the other hand, when the level of the output voltage VD of the three-terminal constant voltage regulator 10 drops below the operating minimum voltage level v1, such as when driving many loads at once, the voltage constant diode 15 does not conduct, so the transistor 17
becomes non-conductive, so the power supply voltage cutoff transistor 16i
j It becomes a non-conducting state. Therefore, in this case, the power supply voltage supply path from the DC power supply 1 to the solenoid 12 and display LED 14 via the transistor 16 is cut off, so even if an abnormal signal is output from the microcomputer 4, the solenoid 1
2 and the display element 14 do not operate, so the solenoid 12 does not malfunction or the display LED I 4 does not display an erroneous display.

FIG. 7 specifically shows the embodiment shown in FIG. 5, and the same reference numerals as in FIG. 6 are the same + lr.

The component parts are shown. In this case, as shown in the figure, the power supply voltage at the input terminal of the three-terminal constant voltage regulator 10 (corresponding to the constant voltage circuit 3 in FIG. 5) is applied to the constant voltage diode 15. The only difference is that the other configurations are exactly the same as the embodiment shown in FIG. In this way, the input m to the three-terminal constant voltage regulator 10
When the level of the voltage V is higher than the minimum operating voltage level v1, the constant voltage diode 5 becomes conductive, and as a result, the solenoid 12 (corresponding to the load 6 in Fig. 5) is energized and the display The LED I 4 (corresponding to the display element 7 in FIG. 5) emits light. On the other hand, when the level of the input m pressure V to the three-terminal constant voltage regulator 10 has not reached the minimum operating pressure level vl, such as immediately after the power switch 2 is turned on, the constant voltage diode 15
Solenoid 12 and display LWD
The power supply voltage supply path to 14 is cut off. Therefore, in this case, the solenoid 12 and the display LED 1.4 will not operate due to the abnormal signal from the microcomputer 4, so the solenoid 12 may malfunction and the display LED 1.4 will not operate.
14 will not be displayed incorrectly.

In this way, when the power supply voltage of the power supply circuit is lower than a predetermined voltage level (the minimum voltage level required for normal operation of the microcomputer), the power supply voltage supply path from the power supply to the load and display element is cut off. Therefore, when the power switch is turned on or the power supply voltage drops, power supply voltage is not supplied to the load and display element, so even if an abnormal signal is output from the microcontroller, the load and display element will not operate. Since there is no load, malfunction of the load and erroneous display of the display element will not occur.

Note that the straight power source of the power supply circuit in this embodiment may be a rectified AC power source or a battery. Further, in this embodiment, a constant voltage diode was used as a voltage level sensing circuit to control the Shingen Kame J:lZ cutoff circuit, but when the level of the power supply voltage is compared with a certain reference voltage, as a result, the power supply voltage is lower than the reference voltage level. A comparator may be used to control the power supply voltage cutoff circuit so that the power supply voltage supply path is cut off when the voltage is low.

(E) Detailed Description of the Invention As described above, the present invention provides a power supply circuit that supplies a power supply voltage to a microcomputer and a load driven based on an output signal of the microcomputer. When the source voltage is below a predetermined level due to driving many loads at once, we cut off the power supply voltage supply path from the power supply to the negative load, so the load does not operate and the microcontroller issues an error message. The load will not malfunction even if the signal is output.

[Brief explanation of the drawing]

Figures 1 and 2 show the power supply circuits of conventional 1u child components connected to the microcomputer control unit in different columns. ! Figure J31 is a diagram showing changes in the power supply voltage after the power switch is turned on, Figures 4 and 5 are different embodiments showing the power supply circuit of an electronic component according to the present invention connected to a microcomputer control section, and Figure 6 is a diagram showing changes in the power supply voltage after the power switch is turned on. The figure shows a specific circuit example of the embodiment shown in FIG. 4, and FIG. 7 shows a specific circuit example of the embodiment shown in FIG. DESCRIPTION OF SYMBOLS 1... DC power supply, 2... Power switch, 3... Constant voltage IMIk, 4... Microcomputer, 5
...Output circuit, 6...Load, 7...Display element (load), 8...M source voltage cutoff circuit, 9...Voltage level sensing circuit, ]0...3 terminal fixed end Pressure regulator, 11
．． 13... Drive transistor, 12... Solenoid, 14... Display LED, is... Constant voltage diode, 16... Core? M tonne pressure cutoff transistor patent applicant: Nissan Automatic G, Co., Ltd. Agent Patent attorney: Hiroshi Suzuki Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] In a power supply circuit that supplies power supply voltage to a microcomputer and a load driven based on an output signal of the microcomputer, a power supply that cuts off a power supply voltage supply path from the power supply to the load when the power supply voltage is below a predetermined level. A power supply circuit for an electronic component, characterized in that it is provided with a voltage cutoff means.