JPS6194123A - Power supply device with voltage drop detecting circuit - Google Patents

Abstract

PURPOSE:To decrease the number of component parts and to reduce the fault factor by delivering a reset signal to an electronic device from a reset circuit after the reduction of the input power supply voltage is detected by a voltage reduction detecting circuit. CONSTITUTION:The voltage of an input power supply 12 is stabilized by a constant voltage circuit A and supplied to the electronic devices including a microcomputer, etc. The voltage reduction of the supply 12 is detected and the reset signal of the microcomputer. Then a voltage reduction detecting circuit B and a reset circuit C are provided along with an oscillation circuit D which transmits reset signals periodically. A base is connected to a junction between a Zener diode 11 of the circuit A and a resistance 15. Such 1st transistor Tr16 and the 2nd Tr18 connected to the cathode of the diode 11 via a resistance 19 detect the reduction of the power supply voltage. Then the reset signal is obtained via an Rc circuit consisting of a capacitor 23 and a resistance 22 of the circuit C and a buffer 24 which is used for formation of a waveform. The obtained reset signal is delivered to the circuit D, and the reset signals produced periodically are supplied to the microcomputer.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides a power supply device with a voltage drop detection circuit that outputs a reset signal for an electronic device such as a microcomputer when a drop in cardiac pressure of an input power source is detected. It's about what.

[Conventional technology]

Electronic devices such as microcomputers (hereinafter referred to as microcomputers) require a stabilized 72-volt power supply, and when the input voltage drops, electronic devices and peripheral circuits must be reset to prevent malfunctions. It is necessary to

A conventional power supply device that supplies a stable voltage to such electronic equipment and outputs a reset signal when the input power supply voltage drops is shown in FIG. 2.

In FIG. 2, 1 is a stabilized power supply circuit, which is generally constructed using a transistor, a Tsunar diode, a three-terminal regulator, etc., and stabilizes the input power supply and outputs a constant voltage. 2 is a voltage drop detection circuit that detects an abnormal state when the voltage of the input power source drops;
Reference numeral 3 denotes a reset circuit that resets a microcomputer (not shown) and peripheral circuits.

In the power supply device having the above configuration, when the power is turned on, the reset circuit 3 detects the rise of the output of the power supply circuit 1, and outputs a reset 1- signal to the microcomputer and the h'J side circuit. This reset signal is a signal necessary to start the microcomputer, and a pulse signal of several tens of micrometers to several hundreds of micrometers from the rise of the output of the power supply circuit 1 is used. I cut it,
Voltage drop detection circuit 2 outputs a detection signal when the input power supply voltage drops and normal operation becomes impossible, and reset circuit 3
outputs a reset signal for the microcomputer and peripheral circuits based on this detection signal to prevent malfunctions of the microcomputer and IJ side circuits.

In this way, a stable output voltage is supplied to the microcomputer and peripheral circuits, and a reset signal is issued when the input power supply voltage drops below a predetermined value, thereby preventing malfunctions of the microcomputer and peripheral circuits.

[Problem that the invention seeks to solve]

In the above power supply device, a stabilized power supply circuit 1,
Since the voltage drop detection circuit 2 and the reset circuit 3 are each constructed independently (II7), the number of circuits for the b'IY components is complicated, and the mounting area of each 6'q component is large and expensive. There were problems in that it was easy to use, had a high failure rate, and consumed a lot of power.

This invention has been made by focusing on the m point among such conventional devices, and provides an inexpensive power supply device with a voltage drop detection circuit that can be configured with a simple circuit with a small number of components, has a low failure rate, and has a low failure rate. The purpose is to

[Means for solving m points between]

The power supply device with a voltage drop detection circuit of the present invention includes a constant voltage circuit using a Zener diode, a first transistor whose base is connected to the anode side of the Zener diode, and a switching operation of the first transistor. A voltage drop detection circuit including a second transistor that opens and closes according to the opening and closing conditions, and a reset circuit that outputs a reset signal depending on the opening and closing state of the second transistor are provided.

[For production]

A constant voltage circuit supplies a stable voltage to electronic equipment. When the -pressure drop detection circuit detects that the human power source'11C pressure has dropped below a predetermined value, the reset circuit outputs a reset signal to the electronic device.

〔Example〕

An embodiment of the present invention will be described below with reference to the drawings.

FIG. 1 shows a circuit diagram of a power supply device according to the present invention. This power supply device is composed of a constant voltage circuit A, a voltage drop detection circuit B, a reset circuit C, and an oscillation circuit. In addition to supplying the specified voltage, it also resets the icon when the input power supply voltage drops.
It's just like that.

In FIG. 1, 11 is a Zener diode (hereinafter referred to as ZD) connected to the input power supply 12 through a resistor 13, its cathode side is connected to the base of an N P N-type transistor 140, and its anode side is connected through a resistor 15. connected to ground. Reference numeral 16 denotes an N P N-type transistor (first transistor) whose base is connected to the anode side of ZDll, whose emitter is grounded and whose collector is connected via a resistor 17 to the DC power supply that serves as the output of the transistor 14. There is. 18 is an NPN transistor (second transistor) whose base is connected to the collector of transistor 16, and the collector is connected to the cathode of ZDl 1 and resistor 1.
The transistor 16 opens and closes in accordance with the switching operation of the transistor 16. Further, a series circuit of a diode 20 and a resistor 21 is connected to the collector of the transistor 18, so that the voltage of the DC power supply is connected to the resistor 2.
2 is applied throughout. 23 is a capacitor connected between the resistor 22 and the ground, and the voltage of this capacitor 23 becomes H (high level) or L (low level) depending on the open/closed state of the transistor 18, and is used as a reset signal to the microcontroller, which will be described later. be done.

In other words, the reset circuit C includes a resistor 22 and a capacitor 2.
3 RC circuit and a buffer 24 for waveform shaping.
The voltage waveform of the capacitor 23 is shaped and output as a reset signal.

The oscillation circuit is used to periodically send a reset signal to the microcomputer, and in systems that do not require periodic reset signals, this oscillation circuit can be omitted, and the reset circuit C When the manually inputted reset signal becomes H, it outputs a periodically oscillating reset signal to the microcomputer.

Next, to explain the operation, first, in constant voltage circuit A, ZDI
The voltage across the resistor 13, ZDl 1, and the pace-emitter voltage VBE2 of the transistor 16 are almost constant regardless of the current value flowing through them. Although the current flowing between them also changes, the voltage at point A in the figure remains almost constant at VZD+VBK2. Here, the pace-emitter voltage VBEI of the transistor 14 has almost the same value as the voltage VBE2 of the transistor 16, so the voltage at point D is VZD+VBE2 vBKl'FvZD
The Tonaruko voltage V Z D has little voltage fluctuation due to temperature changes, and the voltages VElil and VBE2 have similar change characteristics, so the four points are that the output voltage is stable regardless of changes in the ambient temperature. can be obtained.

Next, in the voltage drop detection circuit, the input power supply 121) 1
1i, Pressure V work H is enough to be covered! l: @ (VxN:
zVzD+vBEz) Transistor 16 as above
The main current flows through the base and it is turned on, so the pace potential of the transistor 18 is L and the transistor 18 is turned off.
F and F1-. It's on. Therefore, there is no influence on the reset circuit C, and the point D becomes H.

17 However, as the input voltage ■IN decreases (■Work N〈
N'z D+VE Z 2 ), transistor 16 is O
When the FF is turned on, the transistor 18 is turned on. As a result, the output point becomes L, which notifies the reset circuit C that the input voltage VIH has decreased. At this time, since the resistor 15 is connected between the ZDI 1 and the ground, there is no effect of the leakage ↑) of the ZDll, and the switching characteristics of the transistor 16 are also improved. Furthermore, when the transistor 18 starts to turn on, positive feedback is applied to point A through the resistor 19, so that the switching speed is fast and unstable operating conditions are eliminated.

In the reset circuit C, the voltage signal at point D, which is the detection signal from the voltage drop detection circuit B, is connected to a resistor 22 and a capacitor 2.
The signal is delayed by the RC circuit No. 3, and the waveform is shaped by the buffer 24. That is, the voltages at the two points rise with a delay of a time determined by the start-up resistor 22 and capacitor 23 of the DC power supply mentioned above. Then, when the input voltage V is reduced and the transistor 18 is turned on, the capacitor 23 is not charged forever and the two points remain at L (IJ upper set state). Note that the connection point between the resistor 22 and the capacitor 23 is connected to the collector of the transistor 18 through the diode 20 and the resistor 21, but this diode 20 is connected to the collector of the transistor 18 through the resistor 19. 21 are provided to protect the transistor 18 by limiting the current.

In addition, the oscillation circuit periodically sends a reset signal to the microcontroller, but if the input voltage vI drops slightly and becomes L at two points, the oscillation stops and the microcontroller is held in the reset state. be done. Then, when the input voltage N becomes high and the transistor 18 turns off, the capacitor 2
3 is charged again and the 2 points become H. At this point, the oscillation circuit DI'll:M starts oscillating, and the microcomputer starts operating normally.

In this way, a stable output voltage is always supplied to the microcomputer, and when the input heavy pressure is removed, the microcomputer is set to the reset state, and malfunctions including the w-side circuit can be prevented.

Each of the above circuits is not independent as in the past, but each component can be mounted on a single board. It has a simple circuit configuration with a small number of IS components.

Further, connection cables for each circuit are not required, 114 charge is reduced, and failures are reduced.

[Effect of the invention] As explained above, according to this invention, each time Y,, 4
+ can be grouped together into a simple configuration, so 1'? It is a simple circuit with a small number of components, which has the effect of reducing the mounting area and the number of failures, as well as reducing current consumption and making it inexpensive.

[Brief explanation of drawings]

FIG. 1 is a circuit diagram of a power supply device with a voltage drop detection circuit according to the present invention, and FIG. 2 is a block diagram showing a conventional example. A: Constant voltage circuit B: Voltage drop detection circuit C: Reset circuit 11: Zener diode 12: Input power supply

Claims (1)

[Claims] A constant voltage circuit that supplies a constant voltage to an electronic device using a Zener diode connected to an input power source, a first transistor whose base is connected to the anode side of the Zener diode, and a switching operation of this first transistor. A power supply device with a voltage drop detection circuit, which includes a voltage drop detection circuit for an input power source, which includes a second transistor that opens and closes, and a reset circuit that outputs a reset signal to an electronic device depending on the open and close state of the second transistor.