Patent Application
20080013225
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The circuit device 20 includes a rectifying/stabilizing unit 30, a load voltage sampling unit 40, an operation unit 50 and a relay 70. The operation unit 50 includes an IC comparator 52. In this embodiment, the IC comparator 52 is an integrated circuit under Model No. LM324. The comparator 52 has 14 contacts and four inbuilt operation amplifiers. The contacts 2 and 3 are the input terminals of the first set of operation amplifier, while the contact 1 is the output terminal thereof. The contacts 5 and 6 are the input terminals of the second set of operation amplifier, while the contact 7 is the output terminal thereof. The contacts 9 and 10 are the input terminals of the third set of operation amplifier, while the contact 8 is the output terminal thereof. The contacts 12 and 13 are the input terminals of the fourth set of operation amplifier, while the contact 14 is the output terminal thereof. The contact 11 is grounded.
The rectifying/stabilizing unit 30 includes a first capacitor 31, a first resistor 32, a first diode 33, a second diode 34, a second capacitor 35, a third capacitor 36 and a Zener diode 37. The input terminal of the rectifying/stabilizing unit 30 is connected to the input terminal 26 of an AC power source. The output terminal of the rectifying/stabilizing unit 30 is connected to the operation unit 50. The AC power is pulled down by the first capacitor 31 and the first resistor 32 and rectified, filtered and stabilized by the first and second diodes 33, 34, the second and third capacitor 35, 36 and the Zener diode 37 into 11V DC voltage as the necessary working voltage.
The load voltage sampling unit 40 is connected to the input terminal 26 of the AC power source and is composed of a second resistor 41, a third diode 42, a fourth diode 43, a third resistor 44 and a variable resistor 45. In loaded state, the second resistor 41 provides a pull-down effect. The third and fourth diodes 42, 43 provide great current protection effect to avoid too great leakage. The third resistor 44 and the variable resistor 45 form a voltage-dividing sampling section 46 for obtaining a load sampling voltage. The value of the load sampling voltage is adjustable by means of the variable resistor 45. For example, the voltage can be adjusted to 160 W or 180 W. The output terminal of the sampling unit 40 is connected to the contact 3 of the comparator 52 of the operation unit 50, which is the positive electrode input terminal of the first set of operation amplifier.
A fourth capacitor 47 is connected with the output terminal of the load voltage sampling unit 40 to provide a filtering effect for the sampling unit 40 so as to avoid mis-operation caused by poor signals.
Besides the IC comparator 52, the operation unit 50 further includes a fourth resistor 53, a fifth resistor 54, a sixth resistor 55, a fifth capacitor 56, a sixth capacitor 57, a seventh resistor 58, an eighth resistor 59, a fifth diode 60, a ninth resistor 61, a tenth resistor 62, an eleventh resistor 63, a twelfth resistor 64 and a sixth capacitor 65. The fourth resistor 53 provides a pull-down effect. The fifth and sixth capacitors 56, 57 serve to eliminate ripple interference and wave current. The eleventh resistor 63 and the twelfth resistor 64 are serially connected. The contact between the two resistors 63, 64 serves as a standard comparison voltage 66. The value of the standard comparison voltage 66 is compared with the sampling voltage of the voltage-dividing sampling section 46 of the sampling unit 40. The standard comparison voltage 66 is connected to the contacts 2, 6, 9 and 13 of the comparator 52, which respectively are the negative electrode input terminals of the four sets of operation amplifiers. The positive electrode of the fifth diode 60 is connected to the contact 1 of the comparator 52, while the negative electrode of the fifth diode 60 is connected to the contact 5 of the comparator 52. The polarity of the sixth diode 65 is reverse to the fifth diode 60. The positive electrode of the sixth diode 65 is connected to the contacts 8 and 12 of the comparator 52, while the negative electrode of the sixth diode 65 is connected to the contact 5 of the comparator 52 to provide a feedback effect.
Two terminals of the relay 70 are respectively connected to the contact 14 of the comparator 52 of the operation unit 50 and the AC power source. The contact 14 is the output terminal of the fourth set of operation amplifier of the comparator 52. In normal state, the relay 70 is always closed to switch on the circuit. A seventh diode 72 is parallelly connected with the relay for restraining the anti-peak voltage of the coil and protecting the relay.
The operation of the present invention is described hereinafter. The circuit device of the present invention is applicable to a light to achieve a current-limiting effect. In this embodiment, a bulb under 190 watts (not limited) is used. In the case that the bulb as the load is over 190 watts, the bulb will be turned on for a moment and then extinguished.
In the case that a bulb under 190 watts serves as a load, after powered by the AC power supply, the first set of operation amplifier of the comparator 52 of the operation unit 50 will compare the voltage. In loaded state, the voltage-dividing sampling section 46 of the load voltage sampling unit 40 obtains a load voltage and inputs the load voltage into the contact 3 of the comparator 52. The load voltage is compared with the standard comparison voltage 66 connected to the contact 2 of the comparator 2. At this time, the load is within the nominal working range of the circuit so that the first set of operation amplifier of the comparator 52 will compare the voltage of the contact 3 with the voltage of the contact 2 to find that the voltage of the contact 3 is lower than the voltage of the contact 2. Under such circumstance, the circuit device 20 is in a working state and the contact 74 of the relay 70 is closed to switch on the circuit to turn on the bulb 80.
In the case that the load of the bulb exceeds the nominal working range, for example, higher than 190 watts, the first set of operation amplifier of the comparator 52 will compare the voltage of the contact 3 with the voltage of the contact 2 to find that the voltage of the contact 3 is higher than the voltage of the contact 2. Under such circumstance, the output terminal of the first set of operation amplifier, that is, the contact 1, outputs high potential into the contact 5 of the comparator. After compared by the second set of operation amplifier of the comparator 52, the contact 7 outputs high potential into the contact 10. Then, after compared by the third set of operation amplifier of the comparator 52, the contact 8 outputs high potential into the contact 12. And after compared by the fourth set of operation amplifier of the comparator 52, the contact 14 outputs high potential for driving the relay 70 to work. At this time, the relay 70 is switched to the contact 76 to cut off the circuit and turn off the bulb.
In the case of override, the relay 70 cuts off the load circuit for automatic protection. At this time, the contact 1 of the comparator 52 turns to output low potential, while the sixth diode 65 provides a feedback effect to keep the contacts 5, 7, 8 and 14 of the comparator 52 outputting high potential, whereby the relay 70 keeps switched off to cut off the load circuit.
When it is desired to restore the circuit device 20 back to its working state, a user must stop from supplying the AC power. For example, the user must switch off the switch 29 of the protection switch 25 as shown in
By means of the present invention, a user can easily judge whether the bulb pertains to high power or low power. This can minimize the possibility of human negligence. The relay of the circuit device serves as the on-off switch of the load circuit. In the case of small wattage bulb, the bulb can be normally used and turned on. Reversely, in the case of large wattage bulb, the bulb will be turned on for a moment and then extinguished. This reminds the user that the wattage of the bulb is too great to save energy. The lighting time of the override bulb is determined by the exceeding wattage. The more the exceeding wattage is, the shorter the lighting time is. In the case of override bulb, after powered off for about five seconds and the bulb is replaced with a bulb under the load, the plug can be re-plugged into the socket to turn on the bulb.
The above embodiments are only used to illustrate the present invention, not intended to limit the scope thereof. Many modifications of the above embodiments can be made without departing from the spirit of the present invention.
