JP2000329796A - Voltage detector - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an alternating current voltage detector capable of relaxing temperature dependence of detection circuit side diodes 29a and 29b and detecting exact voltage without being affected by temperature variation. SOLUTION: A voltage divider circuit dividing a detection object alternating current voltage causing in a detection point P1 is provided with a circuit connected in between the detection point P1 and a reference voltage point P0. A detection circuit connecting a voltage division point P2 on the voltage dividing circuit with a measuring point P3 is provided. Voltage dividing circuit side diodes 19a and 19b are provided for inserting in between the voltage division point P2 and the reference voltage point P0. A detection circuit side diode 29a is provided for inserting in between the voltage division point P2 and the measuring point P3. The interrelationship between the voltage division circuit side diodes 19a and 19b and the detection circuit side diode 29a is determined so that the temperature dependency is mutually cancelled and the voltage change at the measuring point P3 due to temperature change becomes small.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an AC voltage detecting device in which the temperature dependency of a diode on a detecting circuit side is reduced.

[0002]

2. Description of the Related Art When detecting a change in an AC voltage, it is common to rectify the voltage by using a diode after dividing the voltage with a resistor or the like, thereby detecting the change as a low-voltage DC voltage.

[0003]

The diode has a temperature dependency, and the on-voltage of the diode changes according to the temperature change. That results in a detection error. Particularly, when a small voltage change is to be detected, a relatively large detection error occurs. The present invention provides an AC voltage detection device capable of reducing the temperature dependency of the diode (for convenience, referred to as a detection circuit side diode) and detecting a more accurate voltage without being affected by a temperature change.

[0004]

A diode (hereinafter, referred to as a voltage dividing circuit side diode) is incorporated in the voltage dividing circuit side so as to reduce a change in the ON voltage of the detecting circuit side diode, and the ON voltage is controlled by both temperature characteristics. Offset fluctuations.

[0005]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A description will be given with reference to FIG. The AC voltage detection device according to the present invention shown in FIG. 1 is a voltage dividing circuit that divides a detection target AC voltage generated at a detection point P1.
And a voltage dividing circuit connected between the reference potential point P0.
A detection circuit is provided for connecting the voltage dividing point P2 and the measuring point P3 on the voltage dividing circuit. A voltage measuring means 30 is provided between the reference potential point P0 and the measuring point P3. Voltage dividing point P2, reference potential point P
It has voltage dividing circuit side diodes 19a and 19b inserted between zeros. A detection circuit side diode 29a is provided between the voltage dividing point P2 and the measurement point P3. Voltage divider circuit side diode 1
The mutual relationship between 9a and 19b and the diode 29a on the detection circuit side is determined such that the temperature dependence of both is canceled out and the voltage change at the measurement point P3 due to the temperature change becomes small.

FIG. 1 will be supplemented. Detection point P1 shown
Is on the AC load circuit of the inverter which is the AC load terminal of the pair of transistors 51 in series. AC load is discharge lamp 5
4. Inductor 52 for ballast 52 / Inductor 53 for preheating
And the point between the discharge lamp 54 and the ballast inductor 52 is defined as a detection point P1. An arm capacitor 56 is a component of the modified half-bridge inverter circuit. The detection point P1 is used for abnormality detection at the end of the life of the discharge lamp 54. The detection target is a high-frequency AC voltage. The components of the voltage dividing circuit are a coupling capacitor 55 and a resistor 11.
.Resistor 12 and voltage dividing circuit side diodes 19a and 19b
It is. The voltage division point P2 is between the resistors 11 and 12. The components of the detection circuit between the voltage dividing point P2 and the measurement point P3 are the coupling capacitor 21 and the detection circuit side diode 29a. When an overvoltage is detected by the voltage measuring means 30, the inverter operation is stopped to protect the circuit.

For convenience of explanation, the detection circuit side diode is set to 2
Although 9a was used, 29b is the same. Coupling capacitor 21 and detection circuit side diode 29a.2
9b forms a voltage doubler rectifier circuit and applies a DC potential to the measurement point P3. In the voltage doubler output as the voltage doubler rectifier circuit, a diode on the detection circuit side is formed in the capacitor 22 on the output side of 29a. 23 is a discharge resistance of the capacitor 22. Each ON voltage of the detection circuit side diodes 29a and 29b works to lower the potential of the measurement point P3. They can cause detection errors. If the detection circuit side is not a voltage doubler rectifier circuit, the detection circuit side diode 29b is unnecessary.

The diodes 29a and 29b on the detection circuit side are conventionally known. The voltage dividing circuit side diodes 19a and 19b are added according to the present invention. In the present invention, the former on-voltage change and the latter on-voltage change cancel each other out, thereby reducing an undesired potential change at the measurement point P3 due to a temperature change. When the on-voltage increases (decreases) due to the temperature dependency of the voltage dividing circuit side diode 19a, the potential of the voltage dividing point P2 increases by that much, but the on-voltage of the detecting circuit side diode 29a increases (decreases) accordingly. ), Measuring point P
The change in potential of No. 3 is very small. Voltage dividing circuit side diode 19
When the on-voltage increases (decreases) due to the temperature dependence of b, the potential (absolute value) at the voltage dividing point P2 increases by that amount, but the on-voltage of the detection circuit side diode 29b increases (decreases) accordingly. And the voltage of the coupling capacitor 21 decreases accordingly,
The potential change at the measurement point P3 is very small.

The description will be supplemented. The potential of the voltage dividing point P2 during the negative potential period of the detection point P1 depends on the resistor 12 and the voltage dividing circuit side diode 19b. As a result, the voltage of the coupling capacitor 21 is divided by the potential of the voltage dividing point P2 and the diode 29
b. Even if both the voltage dividing circuit side diode 19b and the detecting circuit side diode 29b rise (fall), the voltage of the coupling capacitor 21 remains unchanged.

[0010]

According to the present invention, the voltage dividing point P2 and the reference potential point P0
The main characteristic feature is to provide a voltage dividing circuit side diode interposed therebetween to cancel the mutual temperature dependence of the voltage dividing circuit side diode and the detection circuit side diode. According to this, it is possible to accurately detect the voltage at the detection point P1 even if there is a temperature change.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of the device of the present invention.

[Explanation of symbols]

P0: reference potential point, P1: detection point, P2: partial pressure point, P
3: measurement point, 19a / 19b: voltage dividing circuit side diode,
29a and 29b: diodes on the detection circuit side, 30: voltage measuring means

Claims (1)

[Claims] 1. A voltage dividing circuit for dividing an AC voltage to be detected generated at a detection point P1, wherein said detection point P1 and a reference potential point P
A voltage dividing circuit connected between the reference potential point P0 and the measuring point P3; and a detecting circuit connecting the voltage dividing point P2 and the measuring point P3 on the voltage dividing circuit. And a voltage dividing circuit side diode inserted between the voltage dividing point P2 and the reference potential point P0, and the voltage dividing point P2 and the measuring point P
And a detection circuit-side diode inserted between the two. The potential change at the measurement point P3 due to the temperature change due to the mutual dependency of the voltage-dividing circuit-side diode and the detection circuit-side diode is canceled out. An AC voltage detection device characterized in that it is set to be small.