TWI359275B - Zero crossing detecting circuit of ac power - Google Patents

Description

100 years. October 24th, the shuttle is replacing page 1359725. VI. Description of the invention: [Technical field of invention] [0001] The present invention relates to a detection circuit, and more particularly to a method for determining voltage zero when switching AC power. Measuring circuit. _ [Prior technology]

[0002] At present, many electronic devices are equipped with an uninterruptible power supply system to provide backup power when an external power supply is interrupted or fails, and then converted back after the external power supply is repaired. However, when the external power supply and the backup power supply are switched, the voltage waveform is often caused by the alternating AC power supply, which causes power surge interference, resulting in power supply damage. [0003] A zero-point detection circuit is usually added before the power switch circuit, so that the two power sources can be switched at the voltage zero point, which can greatly reduce the power supply interference caused by the switching. The conventional AC power zero detection circuit generally connects a comparator circuit to the output of the AC voltage source, and compares with a reference voltage to sample the zero point of the AC voltage (including the positive half cycle zero and the negative half cycle zero). Test signal. However, the method of applying the comparator circuit is to directly connect through the resistor and the power switch circuit, which is easy to cause noise surge such as static electricity and coupling, and the comparator circuit is an analog circuit, and the peripheral resistor connected thereto, The selection and adjustment of parameters such as capacitors is complicated. [0004] Therefore, it is necessary to improve the conventional zero point detection circuit to eliminate the above-mentioned missing. SUMMARY OF THE INVENTION [0005] In view of the above, it is necessary to provide an AC power supply zero detection circuit that effectively reduces power supply interference. 095149639 Form No. A0101 Page 3 of 12 1003393695-0 1359275 __ October 24th, 2014 Shuttle Replacement Page

[0006] An AC power zero point detecting circuit includes a live line input terminal, a water line input end, a first photocoupler, a first zero point terminal, a second photocoupler, and a second zero point. a lead end and first and second resistors, wherein the live line input end and the water line input end are respectively connected to two ends of the internal light emitting diode of the first photocoupler, and the internal photoelectric crystal of the first photocoupler is shot The pole is grounded, the collector is connected to the DC power source through the first resistor, and the first zero-point terminal is connected to the collector of the photo-electric crystal of the first photocoupler, and the internal light-emitting diode of the second photo-coupler is An internal light-emitting diode of the first photocoupler is connected in anti-parallel, an emitter of the internal optoelectronic crystal of the second photocoupler is grounded, and a collector is connected to the DC power source through the second resistor, the second zero-point terminal Connected to the collector of the internal optoelectronic crystal of the second optocoupler, the first and second zero-out terminals are connected to a power switch circuit.

[0007] Compared with the prior art, the AC power zero detection circuit realizes optical isolation transmission through the photoelectric coupling characteristics of the first photocoupler, thereby greatly reducing voltage surges such as static electricity, lightning strikes, coupling, etc. Noise interference. [0008] Referring to FIG. 1, the AC power zero detection circuit 10 of the present invention is configured to detect a zero point of an AC power source 20 (such as a 110V AC power source), which includes resistors R1, R2, R3, and a first The photocoupler 12, a second photocoupler 14, a DC power supply Vcc, a first zero terminal X and a second zero terminal Y. The first photocoupler 12 includes a first LED D1 and a first photodiode Q1. The second optocoupler 14 includes a second LED D2 and a second photodiode Q2. 095149639 Form No. A0101 Page 4 / Total 12 Page 1003393695-0 1359275 *, * 100: October 24th Nuclear Replacement Page [0009] One end of the resistor R 3 serves as the AC power zero detection circuit 10 The hot line input end is connected to the live line end L of the alternating current power source 20, and the other end of the resistor R3 is connected to the anode of the first light emitting diode D1 of the first photocoupler 12, and the cathode of the first light emitting diode D1 The water line input end of the AC power supply zero point detecting circuit 10 is connected to the water line end N of the AC power source 20; the emitter of the first photo transistor Q1 in the first photocoupler 12 is grounded, and the collector _ The resistor R1 is connected to the DC power source Vcc, and the node between the collector of the first photo-crystal Q1 and the resistor R1 is connected to the first zero-out terminal X, and the first zero-point terminal X is a positive half-cycle. Zero lead. Φ - [0010] The second light-emitting diode D2 of the second photocoupler 14 is connected in anti-parallel with the first light-emitting diode D1 of the first photocoupler 12; the second photo-coupler 14 The emitter of the second photo-crystal Q2 is grounded, the collector is connected to the DC power source Vcc through the resistor R2, and the node between the collector of the second photo-crystal Q2 and the resistor R2 is connected to the second-zero terminal Y. The second zero terminal Y is a negative half cycle zero terminal. [0011] In the present embodiment, the resistance values of the resistor R1 and the resistor R2 are both 10 kΩ •, the resistance of the resistor R3 is 22 kΩ, and the DC power source Vcc is a 5 V DC power source. [0012] Please continue to refer to FIG. 2, which is a schematic diagram 30, 50 of the waveform diagram 30 of the AC power source 20, the first zero-point terminal X and the second zero-point terminal Y. In the initial state, the first zero-point terminal X and the second zero-point terminal Y are both high. When the alternating current power source 20 reaches the positive half-cycle zero, the first photocoupler 12 is turned on, the first The zero terminal X becomes low and continues to the negative half cycle zero of the AC power source 20; when the AC power source 20 reaches the negative half cycle zero b, the first photocoupler 12 is turned off, 095149639 Form No. A0101 Page 5 of 12 1003393695-0 1359275 October 24, 100 Nuclear replacement page The first zero terminal X is re-converted to a high potential and continues to a positive half cycle zero a below the AC power source 20, Then cycle sequentially. When the AC power source 20 reaches the negative half cycle zero point b, the second photocoupler 14 is turned on, and the second zero point terminal Y becomes a low potential and continues to the positive half cycle zero of the AC power source 20; When the AC power source 20 reaches the positive half cycle zero point a, the second photocoupler 14 is turned off, and the second zero point terminal Y is re-converted to a high potential and continues to a negative half cycle zero point b under the AC power source 20 And then loop in turn.

[0013] When a backup power source (not shown) needs to be switched with the AC power source 20, the first zero-point terminal X and the second zero-point terminal Y of the AC power source zero detecting circuit 10 are connected to the power source. On the switch circuit (not shown), the power switch circuit controls the AC power source 20 at a voltage zero point by receiving a positive half cycle a or a negative half cycle b signal received from the first zero terminal X. The power supply circuit is disconnected, and the standby power supply is connected to the power supply circuit at the voltage zero point through the negative half cycle zero point b or the positive half cycle zero point a signal received from the second zero terminal terminal Y, thereby completing a power supply switching. [0014] The AC power zero detection circuit 10 can also be provided with only one zero-point terminal. In this embodiment, two zero-point terminals are provided in order to shorten the switching time of the two power sources in a half cycle. A zero-point output terminal has a switching time of at least one cycle. If the power requirements are not very high, only one zero-point terminal can be set for cost-saving reasons. [0015] The standby power supply and the AC power supply 20 use the AC power supply zero detection circuit 10 to switch the power supply so that the waveform of the output voltage does not change much, 095149639 Form No. A0101 Page 6 / Total 12 Page 1003393695- 0 1359275 100 years. On October 24th, the revised replacement page drastically reduced power supply interference caused by voltage waveform fusion. Secondly, due to the use of optocouplers for isolated transmission, noise interference caused by voltage surges such as static electricity, lightning strikes, coupling, etc. is reduced. In addition, the AC power zero detection circuit has a simple structure, fewer application components, and no complicated parameter setting, so the cost is low.

[0016] In summary, the present invention complies with the requirements of the invention patent, and submits a patent application according to law. The above description is only the preferred embodiment of the present invention, and equivalent modifications or variations made by those skilled in the art will be included in the following claims. BRIEF DESCRIPTION OF THE DRAWINGS [0017] FIG. 1 is a circuit diagram of an alternating current power supply zero point detecting circuit of the present invention. 2 is a schematic diagram showing an output waveform of an AC power supply corresponding to the first and second zero-point terminals of FIG. 1. [Main component symbol description] [0019] AC power supply zero detection circuit: 1 0 [0020] AC power supply: 20 [0021] First photocoupler: 12 [0022] Second photocoupler: 14 [0023] Light Emitting Diode: D1 [0024] Second Light Emitting Diode: D2 [0025] First Photoelectric Crystal: Q1 [0026] Second Photoelectric Crystal: Q2 Form No. A0101 Page 7 of 12

095149639 1003393695-0 October 24, 100 shuttle replacement page 1359275

[0027] First zero point terminal: X

[0028] Point 20: Terminal: Y

[0029] DC power supply: Vcc [0030] Resistance: Rl, R2, R3

095149639 Form No. A0101 Page 8 of 12 1003393695-0

Claims (1)

100 years. October 24th, according to the replacement page 1359275 . . , * VII, the scope of application for patents: 1. An AC power zero detection circuit, including a live input, a water line An input end, a first photocoupler, a first zero-out terminal, a second photocoupler, a second zero-out terminal, and first to second resistors, the live input and the water-line input respectively Connected to the two ends of the internal light-emitting diode of the first photocoupler, the emitter of the internal photo-electric crystal of the first photocoupler is grounded, and the collector is connected to the DC power source through the first resistor, the first zero point The terminal is connected to the collector of the photo-electric crystal of the first photocoupler, and the internal light-emitting diode of the second photo-coupler is connected in anti-parallel with the internal light-emitting diode of the first photo-coupler, the second photoelectric The emitter of the internal photonic crystal of the coupler is grounded, the collector is connected to the DC power source through the second resistor, and the second zero-point terminal is connected to the collector of the internal optoelectronic crystal of the second photocoupler, the first The 20th terminal is connected to a power switch circuit. 2. The AC power supply zero point detection circuit of claim 1, further comprising a third resistor, wherein the live line input is connected to the light emitting diode of the first photocoupler through the third resistor One end. 3. The AC power source zero detecting circuit according to claim 2, wherein the first resistor has a resistance value of ΙΟΙίΩ, and the third resistor has a resistance value of 22 kΩ. 4. The AC power source zero detecting circuit according to claim 1, wherein the second resistor has a resistance value of 10 kΩ. 5. The AC power source zero detection circuit of claim 1, wherein the DC power source is a 5 V DC power source. 6. AC power supply zero detection circuit as described in item 1 of the patent application's 095149639 Form No. A0101 Page 9 / Total 12 Page 1003393695-0 1359275 October 24th, the shuttle replacement page in the power switch The circuit controls the AC power source and the power supply circuit to be disconnected at a voltage zero point through a zero point signal received from the first zero point terminal. 7. The AC power source zero detection circuit according to claim 6, wherein the power switch circuit further controls a standby power supply and a power supply circuit at a voltage zero point through a zero signal received from the second zero terminal. connection. 095149639 Form No. A0101 Page 10 of 12 1003393695-0