CN201113378Y - electronic current limiter - Google Patents

Abstract

The utility model belongs to the technical field of emergency protection circuit device. The problems of difficulty in controlling parameters, difficulty in production, instability and low accuracy in the prior art are solved. The electronic current limiter comprises a power supply conversion circuit (1), a current detection circuit (2), a detection control circuit (3), the detection control circuit (3) is provided with a mutual inductor T1, a primary coil and lamp connecting end OUT1 and OUT2 are connected in series in an input loop end CN1 and CN2, a secondary coil is connected in series with a rectifier diode D3 to form a voltage signal output end, the detection control circuit is provided with a one-way silicon controlled rectifier Q1 and a relay, the output end of the power supply conversion circuit is connected with a relay coil J connected in series with the cathode and the anode of the one-way silicon controlled rectifier, the control pole and the cathode of the one-way silicon controlled rectifier are connected at the voltage signal output end, the voltage signal output end is connected with a reset switch K1 in parallel, and the normally closed contact of the relay switch S1 is.

Description

electronic current limiter

technical field

The utility model belongs to the technical field of emergency protection circuit devices, and is an electronic current limiter for limiting the load power of an illuminating lamp.

Background technique

According to the requirements of the user, for example, for a lamp with multiple lamp caps, the total power consumption must not exceed a certain wattage, such as 190 watts. Most of the existing control circuits for limiting the power of the lighting load are designed by using general-purpose integrated circuits such as LM324 or LM358. The circuit block diagram of the control circuit can be divided into: sampling circuit, rectification and filtering circuit, amplification and comparison circuit and output control circuit. The amplification and comparison circuit is generally sampled with manganin wire, and the signal is amplified by an operational amplifier for processing, or a transformer is used for sampling. Then use the output of the comparator to control the on and off of the thyristor and the relay, so as to turn off the load to achieve the purpose of power limitation. However, because the magnetic core on the transformer is discrete, it is difficult to control the parameters to be consistent during production, so the productivity will be reduced. Reduction is not easy to produce, and the cost is high. At the same time, the method of using an operational amplifier will also lead to an increase in cost. In short, the production cost and maintenance cost of the existing dimming and power limiting control circuit are too high, and the performance is unstable and the accuracy is not high.

Utility model content

The purpose of the utility model is to provide an electronic current limiter with simple structure, high reliability and low cost, which can cut off the power circuit when the limiting load power increases to a certain value.

In order to achieve the purpose of this utility model, the electronic current limiter includes a power conversion circuit connected to the input circuit terminals CN1 and CN2 to convert the AC power supply into a DC working power supply; the current sensing is performed on the input circuit terminals CN1 and CN2 A current detection circuit for detection; a detection control circuit for performing on-off switching to the power grid according to the output signal of the current detection circuit; the detection control circuit is provided with a transformer T1, and the primary coil of the transformer T1 is connected to the lamp RL connection end OUT1 and OUT2 are connected in series in the input circuit terminals CN1 and CN2, the secondary coil of the transformer T1 is connected in series with the rectifier diode D3 to form a voltage signal output terminal; the detection control circuit is provided with a one-way thyristor Q1 and the relay, the output terminal of the power conversion circuit is connected with the relay coil J connected in series with the cathode and anode of the one-way thyristor Q1, and the control pole and the cathode of the one-way thyristor Q1 are connected to The voltage signal output terminal, the voltage signal output terminal is connected with a reset switch K1, the normally closed contact of the switch S1 of the relay is connected in series with the primary coil and the lamp connection terminals OUT1 and OUT2 The input circuit ends CN1, CN2.

When in use, connect the input circuit terminals CN1 and CN2 to the power supply, and connect the lamp RL to the lamp connection terminals OUT1 and OUT2. On the one hand, the power supply passes through the power conversion circuit to output DC working voltage to provide DC working power for other circuits; on the other hand, it passes through the lamp RL, the normally closed contact of the switch S1 and the primary coil to generate a Induced voltage which varies with load current through lamp RL. When the load current changes to a certain value, the voltage signal output by the voltage signal output terminal is added to the control pole and cathode of the one-way thyristor Q1, so that the cathode and anode of the one-way thyristor Q1 are in a conducting state, and the relay Coil J is energized to make the normally closed contact of switch S1 open, thereby disconnecting the power supply to lamp RL, which plays a protective role of limiting excessive current. At this time, if the reset switch K1 is pressed, the control pole and the cathode of the one-way thyristor Q1 are short-circuited, the cathode and the anode are switched to the cut-off state, the relay coil J is powered off, and the normally closed contact of the switch S1 is closed , and the lamp RL can be connected in series to the input circuit terminals CN1 and CN2 to work, so as to realize power-on reset.

Description of drawings

The descriptions of the attached drawings are as follows:

Fig. 1 is the circuit block diagram of the utility model electronic current limiter.

Figure 2 is a schematic diagram of the circuit in Figure 1.

Detailed ways

Below in conjunction with accompanying drawing, the specific embodiment of electronic current limiter of the present utility model is described in further detail:

The electronic current limiter described in the utility model includes a power conversion circuit (1) connected to input circuit terminals CN1 and CN2 to convert AC power into DC working power. The power conversion circuit (1) is provided with a resistor R2 and a diode D1 connected in series on the input circuit terminals CN1 and CN2, the capacitor C1 and the resistor R1 are connected in series and connected to both ends of the resistor R2, and the anode of the diode D2 is connected to the The cathode of the diode D1 is connected to the cathode of the diode D4, the cathode of the diode D4 is connected to the cathode of the diode D4, and the anode of the diode D1 and the input circuit terminal CN2 are connected to the ground. The two ends of the Zener diode D4 are connected in parallel with the energy storage filter capacitor C2. The two ends of the capacitor C2 are the DC output terminals of the power conversion circuit (1). When the power supply is applied to the input circuit terminals CN1 and CN2, for the AC power supply, the capacitive reactance of the capacitor C1 is much larger than that of the resistors R1 and R2, so when the AC voltage is in the positive half cycle, the current flows through the capacitor C1 and the resistor After being rectified by diode D2, R1 and R2 are added to Zener diode D4 to stabilize the voltage to obtain a stable DC voltage. The voltage drop of the power conversion circuit (1) of the power supply to the power supply is mainly concentrated on the capacitor C1, thus avoiding the problems of large volume, complex circuit and high cost caused by using a transformer for voltage reduction. The power conversion circuit (1) of the power supply is a simple DC voltage stabilized output circuit. Although the DC output signal has certain voltage fluctuations and ripples, it is sufficient to meet the working voltage of the detection control circuit (3).

A current detection circuit (2) for performing current induction detection on the input loop terminals CN1 and CN2. The detection control circuit (3) is provided with a transformer T1, the primary coil of the transformer T1 is a wire passing through the magnetic core, and the primary coil is connected in series with the lamp connection terminals OUT1 and OUT2 at the input circuit terminals CN1 and CN2 In the above, the secondary coil of the transformer T1 is connected in series with the rectifier diode D3 to form a voltage signal output terminal. According to the use of the light bulb load, the secondary coil is designed to output an AC voltage of about 1.5 volts. Since the primary coil is a wire passing through the magnetic core, the turn ratio between it and the secondary coil is relatively large. When the primary coil When the current changes slightly, the output voltage of the secondary coil will change greatly, so it has a large signal change ratio, which is convenient for current induction detection. The two ends of the secondary coil of the transformer T1 are connected in parallel with a resistor R3, and the resistor R3 makes the output voltage at both ends of the secondary coil of the transformer T1 relatively stable.

According to the output signal of the current detection circuit (2), the detection control circuit (3) is used to switch the grid on and off. The detection control circuit (3) is provided with a one-way thyristor Q1, a relay, a reset switch K1, and a diode D5.

The output terminal of the power conversion circuit (1) is connected with a relay coil J connected in series with the cathode and anode of the one-way thyristor Q1, and the control pole and the cathode of the one-way thyristor Q1 are connected to the The voltage signal output described above.

The voltage signal output terminal is connected with a reset switch K1 in parallel, and the normally closed contact of the switch S1 of the relay is connected in series with the primary coil and the lamp connection terminals OUT1 and OUT2 to the input circuit terminal CN1, CN2.

When a conduction voltage is applied between the control electrode and the cathode of the one-way thyristor Q1, the cathode and the anode are in the conduction state, otherwise they are in the cut-off state. Therefore, when the cathode and the anode are in the conduction state, the DC voltage at the output terminal of the power conversion circuit (1) is applied to the relay coil J, so that the switch S1 of the relay acts, and is converted from normally closed to open. On the contrary, when the cathode and the anode are in the cut-off state, the switch S1 is switched from open to closed.

The voltage signal output end is connected with an energy storage capacitor C4 in parallel. The parameter value of the energy storage capacitor C4 is 100 microfarads, so that the DC component of the voltage signal output terminal becomes smooth, and the smooth DC component voltage is used as the on-off control of the control electrode and the cathode of the one-way thyristor Q1.

The voltage signal output terminal is connected with a high-frequency filter capacitor C3 in parallel. The parameter value of the high-frequency filter capacitor C3 is 0.01 microfarads. When a high-frequency interference signal is generated at the input circuit terminals CN1 and CN2, the high-frequency pulse output at the voltage signal output terminal is added to the high-frequency filter capacitor C3 and becomes equivalent to a short circuit. It is absorbed, so as to avoid false triggering between the control electrode and the cathode of the one-way thyristor Q1, so that the switch S1 is switched from normally closed to open.

The voltage signal output terminal is connected with an adjustable resistor RT1 in parallel. When the power supply is completely cut off, the adjustable resistor RT1 can release the electric energy stored in the capacitors C3 and C4. In case of overload, that is, the voltage stored on the capacitor is higher than the trigger voltage of the control electrode and cathode of the one-way thyristor Q1. The trigger voltage keeps the one-way thyristor Q1 in the conduction state, causing the normally closed contact of the switch S1 to change from closed to open, so that the lamp RL is always in the open state. On the other hand, the adjustable resistor RT1 is also the load of the secondary coil of the transformer T1. By adjusting the resistance value of the adjustable resistor RT1, the conduction voltage applied between the control pole and the cathode corresponds to the voltage flowing through the transformer T1. The current value of the primary coil.

The two ends of the relay coil J are connected in parallel with a diode D5 reversely connected in series with the cathode and anode of the one-way thyristor Q1. When the one-way thyristor Q1 is cut off, a forward high voltage applied to the anode and cathode will be generated at both ends of the relay coil J. At this time, since the anode of the diode D5 is connected to the anode, the forward high voltage can be discharged through the diode D5. To prevent the cathode and anode of the one-way silicon controlled rectifier Q1 from switching to the cut-off state instantaneously, the high voltage generated at both ends of the relay coil J is applied to both ends of the cathode and anode, causing breakdown and burning.

The input circuit terminals CN1 and CN2 are provided with a light-emitting diode LED and a resistor R4 connected in series with the normally open contact of the switch S1 and the primary coil. When the normally closed contact of the switch S1 is disconnected, the normally open contact is closed. At this time, the lamp RL is disconnected, and the light emitting diode LED and the resistor R4 replace the lamp RL and are connected in series in the input circuit terminals CN1 and CN2 to emit light. Prompt overload.

Claims (8)

1. An electronic current limiter comprising: Connected to the input circuit terminals CN1 and CN2, a power conversion circuit (1) for converting AC power into DC working power; A current detection circuit (2) for performing current induction detection on the input circuit terminals CN1 and CN2; A detection control circuit (3) for performing on-off switching of the power grid according to the output signal of the current detection circuit (2); Its characteristics are: The detection control circuit (3) is provided with a transformer T1, the primary coil of the transformer T1 is connected in series with the lamp connection terminals OUT1 and OUT2 in the input circuit terminals CN1 and CN2, and the secondary coil of the transformer T1 is The stage coil is connected in series with the rectifier diode D3 to form a voltage signal output terminal; The detection control circuit (3) is provided with a one-way thyristor Q1 and a relay, and the output terminal of the power conversion circuit (1) is connected with a relay connected in series with the cathode and anode of the one-way thyristor Q1 The coil J, the control pole and the cathode of the one-way thyristor Q1 are connected to the voltage signal output end, and the voltage signal output end is connected with a reset switch K1, and the normally closed of the relay switch S1 The contacts are connected in series with the primary coil and lamp connection terminals OUT1 and OUT2 in the input circuit terminals CN1 and CN2. 2. The electronic current limiter according to claim 1, characterized in that the output terminal of the voltage signal is connected with an energy storage capacitor C4 in parallel. 3. The electronic current limiter according to claim 1, characterized in that the output terminal of the voltage signal is connected with a high-frequency filter capacitor C3. 4. The electronic current limiter according to claim 2, characterized in that the output terminal of the voltage signal is connected with a high-frequency filter capacitor C3. 5. The electronic current limiter according to claim 1, 2, 3 or 4, characterized in that the voltage signal output terminal is connected with an adjustable resistor RT1. 6. The electronic current limiter according to claim 1, 2, 3 or 4, characterized in that the two ends of the relay coil J are connected in parallel with the cathode and anode of the one-way thyristor Q1 reversely connected in series Diode D5. 7. The electronic current limiter according to claim 1, 2, 3 or 4, characterized in that the input circuit terminals CN1 and CN2 are provided with a light-emitting diode connected in series with the normally open contact of the switch S1 and the primary coil LED and resistor R4. 8. The electronic current limiter according to claim 1, 2, 3 or 4, characterized in that the two ends of the secondary coil of the transformer T1 are connected in parallel with a resistor R3.

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