JPS5820032A - Resetting circuit - Google Patents

Abstract

PURPOSE:To ensure correct resetting during turning-on and -off of a power supply and during a drop of voltage, by extracting the voltage to be compared with the voltage which is proportional to the power supply voltage out of the power supply voltage via a constant voltage element. CONSTITUTION:A voltage divider consists of resistances R1 and R2. A Zener diode 4 is connected between a voltage applying point A and the resistance R1, and a capacitor C3 is connected in parallel with the resistance R2. The power supply voltage VA and the both-end voltage VB of the C3 are led to a deciding circuit 5. The circuit 5 compares the voltage VB with voltage VTH(=1/2VA) which is proportional to the voltage VA and delivers a reset signal VO when VB<VTH is obtained. When the power supply is applied, the voltage VTH increases as the rise of the voltage VA. The voltage VB rises up to the final level VR which is decided by the voltage dividing ratio of the voltage divider as well as the Zener voltage of the diode 4 on the basis of the time constant CR1. The circuit 5 delivers the signal VO while VB<VTH is satisfied. When the power supply is cut, the discharge current of the C3 and the current from the power supply side flow to the resistance R2. Then VB<VTH is assuredly obtained during a drop of VA. Thus the circuit 5 delivers the signal V0.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a reset circuit that outputs a reset signal to prevent malfunctions or malfunctions that occur in electronic control circuits when power is turned on, cut off, or voltage drops.

For example, in an electronic control circuit that controls an inverter,
When the power is turned on, shut off, or when the voltage drops, a situation occurs in which the circuit cannot operate normally and a malfunction signal is output, causing a pair of inverter arms connected in series to the power supply to become conductive at the same time. This may cause a power short circuit. Even in devices other than the inverter, there may be cases where, for example, a trip signal of -9 is output, or conversely, a signal that should be output is not output. In order to eliminate such inconveniences, an electronic control circuit or a reset circuit is used. Examples of conventional configurations of this type of reset circuit are shown in FIGS. 1 and 2.

In FIG. 1, a resistor 1 and a capacitor 3 are connected in series with respect to the power supply voltage t, the terminal voltage VBI of the capacitor 3 taken out from the series connection point is used as the first input signal of the judgment circuit 5, and the power supply is applied. The voltage VA at the point is led to the determination circuit 5 as a second input signal.

In FIG. 2, a resistor 2 is connected in parallel to the capacitor 3 of FIG. 1, so that the resistor 1 and the resistor 2 constitute a voltage divider. The rest is the same as the circuit shown in FIG.

In both FIG. 1 and FIG. 2, the second input signal vA taken out from the power supply point is divided in the judgment circuit 5 into an appropriate value vTH1, for example, 1/2 of the power supply voltage. compared to the input signal.

Now, suppose that a voltage with a waveform shown by 1 KvA in FIG. 3 is applied to the circuits shown in FIGS. 1 and 2.
The terminal voltage of capacitor 3 in the figure is Atsushi 3 K VB 14
IL VB 2 (Steady state Wl Teha VB 2 > V
TH), it gradually increases according to a time constant determined by the product of the resistance value B of the resistor 1 and the capacitance C3 of the capacitor 3. The determination circuit 5 determines the voltage vB1. Compare VB2 with voltage vTH, vBl<v'rl'l t f,=Gt V
Reset signal vo1 (FIG. 1) to V in the range B2 <V'rh. 2 (Figure 2) is output.

In this way, in the circuits shown in Figs. 1 and 2, when the power is turned on, the reset signal is output until the power supply voltage reaches almost a steady value (rated value) or until a predetermined time has elapsed after reaching the steady value. Properly reset electronic control circuits. However, the drawback of this type of conventional circuit is Due to the voltage remaining in the capacitor 3 at the time of shutoff, the attenuation of the voltages VB□ and VB□ lags behind the attenuation of the voltage vTH. Therefore, the state of V<V or vB2<vTH does not occur, so no reset signal is generated. That's true. %, this problem is caused by a power supply system that has a smoothing circuit, etc., and whose power decreases at a slow rate when the power is cut off, and cannot cope with failures that occur when controlling other power supply systems. In that sense,
A solution was desired.

An object of the present invention is to provide a reset circuit that operates correctly not only when the power is turned on but also when the power is turned off or when the voltage drops.

To achieve this objective, the present invention provides power interruption.

In case of time or voltage drop, the voltage to be compared with the power supply voltage is extracted from the power supply voltage through a voltage tolerance element. Based on the details, explained in detail.

FIG. 4 shows an embodiment of the present invention.

In this embodiment, a voltage divider is constructed by the resistor 1.2, and a Zener diode 4 is connected in series as a constant voltage confectioner to the resistor IK on the voltage application point A side, and the resistor on the voltage division output side is Capacitor 3 is connected to 2. Power supply voltage VA, ``f, i.e. Zener diode 4, resistor 1
A voltage applied to a circuit consisting of a resistor 2 and a capacitor 3, and a voltage vBv across the resistor 2 and a capacitor 3 in parallel thereto is conducted to a circuit 5 for determining vBv. The determination circuit 5 compares the voltage VB with the voltage vT□ which is proportional to the voltage vA. Set. In addition, in the illustrated example, the 0 judgment is VT□-TvA, and the -path 5
outputs a reset signal vo when v8<-1. ◎In the circuit shown in Figure 4, when the power is turned on, the voltage VA increases as shown in Figure 5. Voltage vT
H increases. The voltage VB is the voltage V□ which is the diode under Zener.
, starts to increase from the point where it exceeds the Zener voltage v2 of node 4. The final value Arashi of voltage 1 is the rated value V of power supply voltage 4
V81. The resistance is 1.2, and the voltage VBI is this 'vR.
1, the time constant c]lt (where C is the capacitance of the capacitor 3)K therefore increases. In this process, VB<
The VTH period determination circuit 5 outputs a reset signal vo.

Next, consider the case where the voltage VA attenuates from the value v8 with a predetermined time constant as shown in the figure when the power is cut off. In this case, the discharge current of the capacitor 3 and the current supplied from the power supply side via the Zener diode 4 and the resistor 1 are flowing in the resistor 2 in a superimposed manner, and the voltage V which becomes the input signal to the determination circuit 5 is , (t.

(VA-Vz)! '2/ (R, + R2)<VB
<0 which becomes VA-VZ, that is, VB is always vA-vz
The following is true. Since vZ takes a nearly constant value, in the process shown in Fig. 5, v, <VTH must occur during the descent of ■.
(-vA/2), and the determination circuit 5 issues the reset signal vo again.@ In the circuit of No. 411iI, the determination circuit input signals at power-on and power-off are obtained by the same circuit, but both signals are separately generated. It can also be obtained with the following circuit. An example thereof is shown in FIG.

In the reset circuit shown in FIG. 6, a resistor 11 is provided as a signal forming circuit 10 for obtaining a reset signal for power-on, a resistor 12 in series with this, and a capacitor 13 in parallel with this resistor 2. As a signal forming circuit section for obtaining a reset signal for fast-acting, a constant voltage element array and a resistor n connected in series with the constant voltage element array are provided.
2 voltages are led to both input terminals of the determination circuit 15.The signal forming circuit 10 sums the sum and outputs a reset signal in exactly the same way as in the case of FIG. As already mentioned, it is not output.

Next, regarding the signal forming circuit section, the voltage vg of the resistor ρ is the voltage across each constant voltage element, and if it is z, then VB20 `` vA + vz ``t'' Table Jtt, tentatively d v2 = vTH, +vA. ,
As the power supply voltage V□ attenuates, the voltages VTR and ηl change as shown in FIG.
Since B2o becomes zero when V□=vz, and VB20=vTH in the process up to this point, the determination circuit 15 outputs a reset signal light. However, since the circuit section loses the reset signal rather quickly when the power is turned on, it is preferable to use it only when the power is turned off.

In each of the above embodiments, the circuit is based on zero volts, but the circuit shown in FIG.
Of course, a similar circuit configuration would also work. FIG. 9 shows a case where the circuit is applied to the circuit of FIG. 4 as an example, and each reference numeral corresponds to that of FIG. 4 as is. Of course, the circuit operation is also exactly the same.

As described above, according to the present invention, by skillfully using a constant voltage element, it is possible to reliably obtain a reset signal even when the power supply voltage is cut off. It becomes easier to control systems with circuits. In addition, even though inexpensive circuit components are used, by appropriately selecting circuit constants, a reset signal can be reliably obtained even in a system where the power supply voltage rises slowly when turned on.

[Brief explanation of the drawing]

1 and 2 are connection diagrams showing different conventional reset circuits, FIG. 3 is a diagram showing the operating characteristics of the circuits shown in FIGS. 1 and 2, and FIG. The wiring diagram illustrating the embodiment, FIG. 5, is as follows:
Figure 4 is a diagram showing the operating characteristics of the circuit, Figure 6 is a wiring diagram showing another embodiment of the present invention, Figure 7 is a diagram showing the operating characteristics of the circuit in Figure 6. FIG. 3 is a wiring diagram showing still another embodiment of the present invention. 1, 2.11.12. Recommendation...Resistance, 3.13...
Capacitor, 4... Zener diode, U... Constant voltage element, 5.15... Judgment circuit. Applicant's Representative Kiyoshi Inomata 4th Prisoner
6″6 Diagram □ 7 Diagram 8 Prison procedure amendment Showa Kuni Year/V-day Commissioner of the Patent Office Shima 1) Haru Judono 1, Indication of the case Showa Country Patent Application No. 118029 2, Invention Name of ``Detailed Description of the Invention'' in the patent applicant (307) Tokyo Shibaura Electric Co., Ltd. Specification related to the person making the amendment, Seven Circuits 3, and Drawing 8, Contents of the amendment (1) In the specification, add "consisting of a krNAND circuit" in front of "judgment circuit" on page 8, line 7. (2) Add "when the power supply voltage - is at the rated value" before "temporary k" on page 8, line 16. (3) Correct Figure 6 on the WJ screen as shown in the attached sheet. that's all

Claims (1)

[Scope of Claims] 1. A voltage signal circuit that outputs a voltage proportional to the voltage obtained from the power supply voltage via a constant voltage element, and the output voltage of this voltage signal circuit is set to be lower than this during normal operation. and a determination circuit that compares the pJIL#1 voltage with a voltage proportional to the pJIL#1 voltage and outputs a reset signal when the former is lower than the latter. 2. A voltage signal circuit consisting of a constant voltage element connected to a power supply, a series circuit of a voltage divider, and a capacitor connected in parallel to the voltage divider element on the output side of the voltage divider; and a determination circuit that compares the output voltage of the circuit with a voltage proportional to the power supply voltage that is set to be lower than this during steady state, and outputs a reset signal when the former is lower than the latter. TS) 1 circuit. 3. A first voltage signal circuit consisting of a voltage divider that divides the power supply voltage and a capacitor connected in parallel to the voltage divider element on the output side of the voltage divider, and a voltage obtained from the power supply voltage through the constant voltage element. a second voltage signal circuit that outputs a voltage proportional to the output voltage of the first voltage signal circuit and the second voltage signal circuit, and a second voltage signal circuit that outputs a voltage proportional to and a determination circuit that outputs a reset signal to the terminal when the former is lower than the latter.