JPS59192970A - Detecting circuit for voltage variation - Google Patents

Abstract

PURPOSE:To detect variation in power voltage over a wide range by using a semiconductor element which varies in resistance value freely as an equivalent resistance between output terminals of a diode bridge. CONSTITUTION:The semiconductor element 1 which varies in internal resistance value freely is used as the equivalent resistance between output terminals of the diode bridge DB formed of diodes D1-D4 connected to a power source through a capacitor C1. This element 1 is controlled to increase the internal resistance of the element 1, and then the time constant determined by this resistance and capacity of the capacitor C1 increases; even when a source voltage varies slowly, a corresponding detection voltage is developed across the element 1 and rises above a reference voltage, so that a comparator 2 outputs a detection signal for the source voltage variation. Therefore, the source voltage variation such as a rise and a fall over a wide range is detected.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field 1] The present invention relates to a voltage fluctuation detection circuit [Background Art J] Figure 1 shows a conventional example, in which a diode array consisting of four diodes D1 to D4 is used. A series circuit consisting of the diode bridge DB and the capacitor C1 connected to one end of the output end of the diode bridge DB, that is, the connection point between the diodes D3 and D4, is connected to the power supply.

The power source may be direct current or alternating current.Also, a resistor R is connected between the output terminals of the diode ridge DB, that is, between the connection point of the diodes Ω and D3, and the connection point of the diode D2. Both ends of R are used as fluctuation output ends of the power supply voltage Vi of the power supply. And capacitor C1 and resistor R
In the branch-to-junction path between the two, the diode bridge DB converts the change Qj of the power supply voltage Vi into a positive 'voltage' as the output voltage V.
Detection is performed as o. FIG. 2(a) shows a case where the power supply voltage Vi is rising, and the power supply voltage Vi becomes larger than the voltage Vc of the sensor C1, and the diodes l)2 and D
3 is in the forward direction, and a positive output voltage Vo is applied across the resistor R.
I am getting . In addition, FIG. 2(b) shows the case where the power supply voltage 1 is falling, and the power supply voltage V1 becomes smaller than the voltage VO of the capacitor C1, and the diodes DI and D4 become forward direction, and the voltage across the resistor R increases. A positive output voltage as f cut is obtained. In such a case, in order to cope with slow voltage fluctuations, the time constant due to clR must be made quite large, which poses problems in terms of size and cost. Another problem was that it was difficult to set the amount of voltage fluctuation that would occur before starting the previous operation.

[Purpose of the invention]

Misfire 1-! A/-1 This was provided in view of the above points, and detects when the input power supply voltage increases due to load opening, etc., or when the main power supply voltage drops due to load short circuits, power outages, etc. The present invention provides a voltage fluctuation detection circuit for the purpose of preventing load damage.

[Disclosure of the Invention] Hereinafter, one embodiment of the present invention will be described in detail with reference to the drawings. FIG. 5 shows a specific circuit diagram thereof, in which a semiconductor element (1) is connected in place of the resistor R of the conventional example, and the other elements 1 are the same as the conventional example. (2) A comparator connected to both ends of the semiconductor element (1) sets a preset reference voltage vA, and determines whether the fluctuating voltage generated across the semiconductor element (1) is higher than this reference voltage VA. In this case, a detection signal is output, and this detection signal drives, for example, a relay, and the circuit is cut off by its contact. In addition, semiconductor elements (
For 1), a material having the following characteristics is used. first,
For example, by using an element such as a transistor that can control the equal-side internal resistance to increase or decrease, or by controlling the state where the equal-side internal resistance is large to small.
Semiconductor elements (1
) However, when the power supply voltage Vi rises and falls,
A positive voltage (2) is generated between terminals a and b. That voltage V
Detect the value of +, and compare the amount of change in the power supply voltage Vi that adversely affects the load/\Vi with the base l$ voltage vA of F. If V1≧vA, take measures such as disconnecting the power supply. give Furthermore, when the power is turned on, a control signal is given to the semiconductor element (1) to reduce the internal resistance on the equal side and change the charging voltage Vc of the capacitor C1 to the commercial voltage Vi, ! : When they are equal,
The isolateral internal resistance of the semiconductor element (1) is brought into a very large state. Also, when performing detection, the semiconductor element (1)
By making the equal-side internal resistance of the capacitor CI very large, even if the power supply voltage Vi changes slowly, the charging/discharging voltage of the capacitor C1 is very small, and there is no change in the voltage Vc of the capacitor CI. , it is possible to grasp changes in the power supply voltage V1 to a greater degree.

FIG. 4 shows another embodiment, in which the resistor R and the semiconductor element (1)
A series circuit is connected between the output terminals of the diode bridge DB, and voltage fluctuations are detected from both ends of the resistor R.The properties of the semiconductor element (1) are as shown in Fig. 5. As shown in the characteristic diagram, an element is used in which the equal-side internal resistance of the element changes when the voltage applied to the element reaches a certain value.Therefore, when the power supply voltage Vi increases or decreases, its The changed voltage △Vi is applied to the semiconductor element (1
)K multiplied by △Vi becomes 1△V11≧vB, the equal-side internal resistance of the semiconductor element (1) becomes extremely small, and as a result, a positive voltage v, =l△■1: is applied to the terminal C-doll. It takes. This voltage is detected and a comparator (2) uses the detection signal to take load protection measures such as disconnecting the power supply.

[Effects of the Invention] As described in L, the present invention connects a series circuit of a diode bridge and a capacitor connected to one end of the input side of the diode bridge to a power supply, and connects an equal circuit between the output ends of the diode bridge. A semiconductor element whose side internal resistance can be varied by an applied voltage or a control signal is connected, and the voltage generated between the output terminals of the diode bridge via the semiconductor element due to voltage fluctuations in the distribution power source is set to a preset reference voltage. Since we installed a comparator that compares and outputs a voltage fluctuation detection signal,
If the voltage increases or decreases, both fluctuations can be detected at the positive voltage and at the same location by the diode on the forward side of the diode bridge, thus pre-lighting the detector. The detection signal from the comparator can be used to take load protection measures such as disconnecting the power supply. By making the equal-side internal resistance of the semiconductor element very large when the power supply voltage is in , it is possible to accurately detect changes in the power supply voltage, and the capacitance of the capacitor can also be reduced. Furthermore, if voltage fluctuations are detected when the power is turned on,
By making the isolateral internal resistance of the semiconductor element very small, the charging voltage of the capacitor can be immediately made equal to the power supply voltage, which has the effect of improving the detection ability.

[Brief explanation of drawings]

Fig. 1 is a circuit diagram of a conventional example, Fig. 2 (α) [b) is an explanatory diagram of the same example as in the previous example, Fig. 5 is a circuit diagram of an embodiment of the present invention, and Fig. 4 is the same as above. FIG. 5 is a circuit diagram of another embodiment of the present invention, and a characteristic diagram of the semiconductor element of the fifth embodiment. (1) is a semiconductor element, (2) is a td comparator, DB is a tie ridge, and C1 is a capacitor.

Claims (1)

[Claims] (1) Connect a series circuit of a diode bridge and a capacitor connected to one end of the input side of this diode bridge to a power supply, and set an equal internal resistance between the output terminals of the diode bridge by applying a voltage or a control signal. Connect a semiconductor element that has been made freely adjustable, and compare the voltage generated between the output terminals of the diode bridge via the semiconductor element due to the voltage fluctuation of the power supply with a preset reference voltage to output a voltage fluctuation detection signal. A voltage f disturbance detection circuit comprising a comparator.