KR100614726B1 - Arc-Fault Detection Circuit in the High Voltage Inverter System - Google Patents

Abstract

According to the present invention, the arc leakage detection circuit 10 of a high voltage inverter used for high-pressure discharge lamps such as neon lamps, cold cathode fluorescent lamps, and external electrode fluorescent lamps has a secondary side to which a high voltage is applied is adjacent to ground, a frame, and other conductors. When an arc is generated by contact, a circuit that detects a voltage change and converts it into a magnitude of voltage in a DC smoothing capacitor of a primary power supply stage, an output capacitor of a power factor correction circuit, or a series capacitor of a half-bridge circuit and a magnitude of the voltage Is limited to the set voltage (V_r) by limiting the operation of the primary side controller 20, the circuit is configured to cut off the power supply to the secondary side of the high voltage inverter.

The present invention adds a simple circuit to the primary side of the high voltage inverter to detect arc generation on the load connection line on the secondary side, thereby improving the stability and reliability of the inverter at low cost, and early warning and preventing fire and electric shock due to the arc generation. Do it.

Arc detection, high voltage inverter, high voltage discharge lamp, neon lamp, CCFL, EEFL

Description

Arc fault detection circuit of high voltage inverter {Arc-Fault Detection Circuit in the High Voltage Inverter System}

FIG. 1 is a waveform diagram illustrating a change in primary input voltage when an arc leakage occurs on a secondary side of a transformer 60 in a high voltage inverter.

2 is a basic circuit diagram for arc short circuit detection according to the present invention.

3 is a block diagram showing an embodiment connected to the voltage comparator inside the switching controller to limit the operation of the switching controller 20 using the arc leakage detection according to the present invention of FIG.

FIG. 4 is a block diagram showing an embodiment in which an arc short circuit is determined through an external voltage comparator 30 using arc short circuit detection according to the present invention of FIG. 2.

5 is used to prevent the application of high voltage on the secondary side of the inverter by limiting the operation of the switching controller 20 by determining the arc leakage through the external reference voltage comparator 40 using the arc leakage detection according to the present invention. It is a block diagram which shows an Example.

Explanation of symbols on the main parts of the drawings

10: arc leakage detection circuit

20: switching controller

30: voltage comparator

40: Voltage Reference Comparator

50: switch

60: transformer

70: input voltage smoothing capacitor

D1, D2: Diode

C1, C2: Capacitor

R1: dummy resistance

The present invention relates to an apparatus for providing safety and reliability of an electric circuit. In particular, the present invention relates to a method and apparatus for early detection and warning of arc leakage in a high voltage inverter.

High voltage inverters used in high-voltage discharge lamps such as neon lamps and CCFL, EEFL are adopted by adopting the following protection methods.

a) Cut off the current in the event of a short circuit or overload to prevent dangerous overcurrent. This is a method of limiting the operation of the switching controller 20 when a fuse is used at the power input terminal or when the current of the inverter is detected to be higher than a predetermined current.

b) By restricting the operation of the switching controller 20 in a low load or no load state, a high voltage is prevented from being applied to the output side.

c) Protect the system by limiting the operation of the switching controller 20 when supplying power outside the input voltage range.

As another type of electrical failure, arc leakage may occur when current flows between the secondary output stage and adjacent conductors separated by voids. Arc leakage of a high voltage inverter can easily occur between the conductor or ground where the discharge lamp is installed and fixed due to the high frequency of the high frequency formed on the secondary side, which may cause the inverter to fail, and furthermore, the temperature rise at the arc generating site. It may cause personal injury by fire and electric shock.

When an arc occurs, the current is limited by the load resistance, and if the current is below the short or overload setting, it cannot be prevented by short circuit or overload protection. Moreover, since most high voltage inverters are configured in an electrically insulated manner between the primary side and the secondary side for safety, and there is no direct closed circuit by the current between the secondary output terminal and the external conductor, detection by primary current increase It's hard to be.

The detection and alarm for arc generation plays a role in preventing fires, inadvertent power outages and damage to electrical appliances, so the need for systems using high voltage inverters is obvious.

Various devices have been introduced for the detection of arc leakage in the past. However, most of the devices are related to the power grid and are difficult to apply to high voltage inverter circuits or to implement individual inverters at low cost.

The technical problem of the present invention is to limit the operation of the inverter by detecting an arc short circuit in a high voltage inverter circuit. In an inverter based on high voltage high frequency switching, it is not easy to detect high frequency noise due to an arc short circuit. The arc leakage detection method at is not applicable. When the arc leakage occurs on the secondary side of the inverter, when the state change reflected on the primary side of the inverter is observed, it is similar to the transient response state caused by the sudden load change, and the arc leakage is detected by limiting the operation of the inverter by detecting such transient response state. To provide early warning.

An arc short circuit detecting circuit 10, which is a feature of the present invention for achieving the above object, is connected to both ends of the smoothing capacitor 70, which is an energy reservoir on the primary side of the inverter. The smoothing capacitor 70 on the primary side of the inverter is used for full-wave rectification or half-wave rectification of the AC input, and may be used for output smoothing of the power factor correction circuit. When the input power is DC, it is used in front of the power stage to supply power to the transformer. In the case of using the half ridge type inverting method, two capacitors may be configured in series. At this time, the arc leakage detection circuit may be connected to both ends of the capacitors in series or both ends of the low-side capacitor.

2 is a basic circuit for generating a detection voltage V_s.

When an arc leakage occurs on the secondary side of the inverter, the voltage variation across the capacitor V_c repeatedly occurs as in the example shown in FIG. This is caused by irregular and sudden load fluctuation due to arc leakage, and the voltage variation is filtered through the capacitor C1 connected in series with the diode D1 of the arc leakage detection circuit, and only the voltage fluctuation portion is detected. ). The diode D2 serves to prevent the detection voltage from being formed in the reverse direction, and the capacitor C2 removes noise of a high frequency to maintain the detection voltage in the form of a DC voltage. In addition, the resistor R1 slowly consumes the accumulated charge of the capacitor C2 to maintain the detection voltage V_s at zero voltage while no arc leakage occurs.

The detection voltage V_s is compared with a reference voltage V_r set by a comparator or a voltage reference, and it is determined that an arc short has occurred when a voltage change greater than the set reference voltage V_r is detected.

3 illustrates an embodiment using an error amplifier or a comparator inside the switching controller 20, and FIG. 4 illustrates an embodiment of determining an arc leakage using the external comparator 30.

Once it is determined that an arc short has occurred, this signal is preferably latched. When the arc short circuit is detected to limit the operation of the switching controller 20, the arc short circuit due to the application of the high voltage on the secondary side of the transformer 60 is blocked, and thus the detection voltage V_s is not maintained. Therefore, it is preferable that the cause of generating the arc leakage is eliminated, and the arc leakage determination is kept in the latched state until the power is turned on again. This can be implemented by using a controller input terminal capable of trip mode operation or by adding a latch circuit outside the controller.

5 is a circuit diagram showing an embodiment of the inverter using the arc leakage detecting circuit 10 of the high voltage inverter according to the present invention and determining the arc leakage using the reference voltage comparator 40.

The arc leakage detecting circuit 10 is connected to an input voltage smoothing capacitor 70 in an inverter composed of a switching controller 20, a switching circuit 50, a high voltage transformer 60, and the like, to change voltage generated by an arc leakage. It is applied in a manner to limit the operation of the switching controller 20 by detecting and operating the reference voltage comparator 40.

The present invention provides a method of preventing arcing and electric shock that may occur due to arc leakage, and preventing accidental power failure and damage to electrical appliances by monitoring an arc leakage of a high voltage inverter through a simple circuit configuration and appropriately blocking it. do. In particular, there is an effect of improving the safety of the high voltage inverter.

Claims (2)

In the method for detecting the arc leakage of the high voltage inverter, A diode D1 connected directly to the inverter DC input voltage or connected to the input voltage smoothing capacitor; A capacitor C1 connected in series with the diode; Comprising a diode (D2), a capacitor (C2) and a dummy resistor (R1) connected in parallel between the capacitor (C1) and zero voltage, An arc short circuit detecting circuit comprising: detecting an arc short circuit by detecting a change in an input voltage generated by an arc short and comparing it with a predetermined reference voltage (V_r). The method of claim 1, In order to compare the set reference voltage V_r and the detected voltage V_s, an internal comparator of the switching controller 20 or an external voltage comparator 30 or a reference voltage comparator 40 is added and used. Arc leakage detection circuit.

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