POWER SYSTEM AND METHOD FOR MONITORING A WORKING ENVIRONMENT OF A MONITORED CIRCUIT AND ADJUSTING A WORKING VOLTAGE OF THE MONITORED CIRCUIT

Abstract

The invention provides a power system for monitoring a working environment of a monitored circuit and adjusting a working voltage of the monitored circuit includes: a power circuit, a voltage-controlled oscillator and a counter. The power circuit is configured to output the working voltage to the monitored circuit through a power supply path. The voltage-controlled oscillator is disposed in or around the monitored circuit and is electrically connected to the power supply path and a ground path to which the monitored circuit is electrically connected, and is configured to output an oscillation frequency in accordance with a signal variation on the power supply path and the ground path. The counter is electrically connected to the voltage-controlled oscillator and is configured to generate a counting number signal in accordance with the oscillation frequency and a synchronizing signal, thereby adjusting the working voltage outputted to the monitored circuit.

Claims

1. A power system for monitoring a working environment of a monitored circuit and adjusting a working voltage of the monitored circuit, comprising: a power circuit configured to output the working voltage to the monitored circuit through a first power supply path; a first voltage-controlled oscillator disposed in or around the monitored circuit, wherein the first voltage-controlled oscillator is electrically connected to the first power supply path and a first ground path to which the monitored circuit is electrically connected, and is configured to output an first oscillation frequency in accordance with a first signal variation on the first power supply path and the first ground path; and a first counter electrically connected to the first voltage-controlled oscillator, wherein the first counter is configured to receive the first oscillation frequency and to generate a first counting number signal in accordance with the first oscillation frequency and a synchronizing signal, and to output the first counting number signal to the power circuit to adjust the working voltage outputted to the monitored circuit.

2. The power system of claim 1, further comprising: a second voltage-controlled oscillator disposed in or around the monitored circuit, wherein the second voltage-controlled oscillator is electrically connected to a second power supply path and a second ground path to which the monitored circuit is electrically connected, and is configured to output an second oscillation frequency in accordance with a second signal variation on the second power supply path and the second ground path; and a second counter electrically connected to the second voltage-controlled oscillator, wherein the second counter is configured to receive the second oscillation frequency and to generate a second counting number signal in accordance with the second oscillation frequency and the synchronizing signal, and to output the second counting number signal to the power circuit to adjust the working voltage outputted to the monitored circuit; wherein the first voltage-controlled oscillator is disposed close to the power circuit, the second voltage-controlled oscillator is disposed away from the power circuit, and the power circuit outputs the working voltage in accordance with the first counting number signal and the second counting number signal.

3. The power system of claim 2, further comprising: a third voltage-controlled oscillator disposed in or around the monitored circuit, wherein the third voltage-controlled oscillator is electrically connected to a third power supply path and a third ground path to which the monitored circuit is electrically connected, and is configured to output an third oscillation frequency in accordance with a third signal variation on the third power supply path and the third ground path; and a third counter electrically connected to the third voltage-controlled oscillator, wherein the third counter is configured to receive the third oscillation frequency and to generate a third counting number signal in accordance with the third oscillation frequency and the synchronizing signal, and to output the third counting number signal to the power circuit to adjust the working voltage outputted to the monitored circuit; wherein the third voltage-controlled oscillator is disposed between the first voltage-controlled oscillator and the second voltage-controlled oscillator, and the power circuit outputs the working voltage in accordance with the first counting number signal, the second counting number signal and the third counting number.

4. The power system of claim 3, wherein the working voltage outputted by the power circuit is adjusted to enable the first counting number signal, the second counting number signal and the third counting number signal to be in a predetermined counting number range.

5. The power system of claim 2, wherein the working voltage outputted by the power circuit is adjusted to enable the first counting number signal and the second counting number signal to be in a predetermined counting number range.

6. The power system of claim 1, further comprising: a phase locked loop (PLL) circuit electrically connected between the monitored circuit and an output of the first voltage-controlled oscillator, wherein the phase locked loop circuit is configured to receive the first oscillation frequency and to output an operating frequency to the monitored circuit according to the first oscillation frequency.

7. The power system of claim 6, wherein the operating frequency and the oscillation frequency have a multiple relationship.

8. The power system of claim 1, further comprising: a low-dropout regulator (LDO) electrically connected between the power circuit and the monitored circuit, wherein the low-dropout regulator is configured to stabilize the working voltage supplied by the power circuit to the monitored circuit.

9. The power system of claim 1, wherein the working voltage outputted by the power circuit is adjusted to enable the first counting number signal to be equal to a predetermined counting number.

10. The power system of claim 1, wherein the monitored circuit is a digital circuit, and the first voltage-controlled oscillator further comprises: a plurality of logic gates electrically connected to the first power supply path of the monitored circuit, wherein the plurality of logic gates comprising: a NAND gate; a NOR gate electrically connected to an output of the NAND gate; and an inverter electrically connected to an output of the NOR gate, wherein an output of the inverter is connected to an input of the NAND gate; and a plurality of capacitors, wherein the plurality of logic gates are connected to first ground path through the plurality of capacitors.

11. The power system of claim 1, wherein the synchronizing signal is a reference signal with a fixed time signal.

12. A method for monitoring a working environment of a monitored circuit and adjusting a working voltage of a monitored circuit, comprising: disposing a first voltage-controlled oscillator in or around the monitored circuit, wherein the first voltage-controlled oscillator is electrically connected to a first power supply path and a first ground path to which the monitored circuit is electrically connected; outputting a first oscillation frequency in accordance with a first signal variation on a first power supply path and a first ground path by using the first voltage-controlled oscillator; generating a first counting number signal in accordance with the first oscillation frequency and a synchronizing signal by using a first counter; and adjusting the working voltage outputted to the first power supply path in accordance with the first counting number signal by using a power circuit.

13. The method of claim 12, further comprising: disposing a second voltage-controlled oscillator in or around the monitored circuit and close to the power circuit, wherein the second voltage-controlled oscillator is electrically connected to a second power supply path and a second ground path to which the monitored circuit is electrically connected; outputting an second oscillation frequency in accordance with a second signal variation on the second power supply path and the second ground path by using the second voltage-controlled oscillator; generating a second counting number signal in accordance with the second oscillation frequency and the synchronizing signal by using a second counter; and adjusting the working voltage outputted to the second power supply path in accordance with the first counting number signal and the second counting number signal by using the power circuit; wherein the first voltage-controlled oscillator is disposed close to the power circuit, and the second voltage-controlled oscillator is disposed away from the power circuit.

14. The method of claim 13, further comprising: disposing a third voltage-controlled oscillator in or around the monitored circuit, wherein the third voltage-controlled oscillator is disposed between the first voltage-controlled oscillator and the second voltage-controlled oscillator, and wherein the third voltage-controlled oscillator is electrically connected to a third power supply path and a third ground path to which the monitored circuit is electrically connected; outputting an third oscillation frequency in accordance with a third signal variation on the third power supply path and the third ground path by using the third voltage-controlled oscillator; generating a third counting number signal in accordance with the third oscillation frequency and the synchronizing signal by using a third counter; and adjusting the working voltage outputted to the third power supply path in accordance with the first counting number signal, the second counting number signal and the third counting number signal by using the power circuit.

15. The method of claim 14, wherein adjusting the working voltage outputted to the third power supply path in accordance with the first counting number signal, the second counting number signal and the third counting number signal by using the power circuit comprises: adjusting the working voltage to enable the first counting number signal, the second counting number signal and the third counting number signal to be in a predetermined counting number range.

16. The method of claim 13, wherein adjusting the working voltage outputted to the second power supply path in accordance with the first counting number signal and the second counting number signal by using the power circuit comprises: adjusting the working voltage to enable the first counting number signal and the second counting number signal to be in a predetermined counting number range.

17. The method of claim 12, further comprising: receiving the working voltage from the power circuit and stabilizing the working voltage outputted to the monitored circuit by using a low-dropout regulator.

18. The method of claim 12, further comprising: receiving the first oscillation frequency and outputting an operating frequency to the monitored circuit in accordance with the first oscillation frequency by using a phase locked loop circuit, wherein the operating frequency and the first oscillation frequency have a multiple relationship.

19. The method of claim 12, wherein adjusting the working voltage outputted to the first power supply path in accordance with the first counting number signal by using the power circuit comprises: adjusting the working voltage to enable the first counting number signal to be equal to a predetermined counting number.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0023] FIG. 1 is a schematic diagram showing a power system for monitoring a working environment of a monitored circuit and adjusting a working voltage of the monitored circuit in accordance with an embodiment of the present invention.

[0024] FIG. 2 is a schematic diagram showing the working voltage of the monitored circuit is adjusted in accordance with the counting number signal and the synchronization signal in an embodiment of the invention.

[0025] FIG. 3 is a schematic diagram showing the voltage-controlled oscillators disposed in the monitored circuit in a circuit board in an embodiment of the invention.

[0026] FIG. 4 is a schematic diagram showing an internal logic structure of the voltage-controlled oscillator in an embodiment of the invention.

[0027] FIG. 5 is a schematic diagram showing the voltage-controlled oscillator and the counter applied to an analog circuit in an embodiment of the invention.

[0028] FIG. 6 is a schematic diagram showing a phase locked loop (PLL) circuit included in an embodiment of the invention.

[0029] FIG. 7 is a flowchart showing a flowchart showing a method 300 for monitoring a working environment of a monitored circuit and adjusting a working voltage of the monitored circuit in an embodiment of the invention.

DETAILED DESCRIPTION

[0030] Referring to FIG. 1, FIG. 1 is a schematic diagram showing a power system for monitoring a working environment of a monitored circuit 100 and adjusting a working voltage of the monitored circuit 100 in accordance with an embodiment of the present invention. The monitored circuit 100 can be a digital logic circuit or an analog circuit. In this embodiment, the monitored circuit 100 is a digital integrated circuit, and the digital integrated circuit is designed though circuit synthesis. The power system includes a power circuit 210, a voltage-controlled oscillator (VCO) 220 and a counter 230, which are configured to monitor the working environment of the monitored circuit 100 and to adjust the working voltage of the monitored circuit 100. The power circuit 210 is configured to output a working voltage to the monitored circuit 100 through a power supply path of the monitored circuit 100, and the monitored circuit 100 is electrically connected to ground through a ground path. When a signal variation occurs on the power supply path and/or the ground path of the monitored circuit 100, the power system is capable of detecting the signal variation, and stabilizing an operating frequency of the monitored circuit 100. The voltage-controlled oscillator 220 can be disposed in or around the monitored circuit 100. For example, as shown in FIG. 1, the voltage-controlled oscillator 220 is disposed outside the monitored circuit 100, but embodiments of the present invention are not limited thereto. In some embodiments, the voltage-controlled oscillator 220 can be disposed in the monitored circuit 100 and on the power supply path and the ground path of the monitored circuit 100. Further, in some embodiments, plural voltage-controlled oscillators and plural counters can be used in the power system for monitoring more power paths and ground paths of the power circuit 210. As shown in FIG. 1, the voltage-controlled oscillator 220 is configured to output an oscillation frequency f.sub.o capable of changing in accordance with the signal variation on the power supply path/the ground path of the monitored circuit 100. The counter 230 is electrically connected to an output of the voltage-controlled oscillator 220. The counter 230 is configured to receive the oscillation frequency f.sub.o and to generate a counting number signal in accordance with the oscillation frequency f.sub.o and a synchronizing signal. The counting number signal is then transmitted to the power circuit 210 to adjust the working voltage outputted to the monitored circuit 100. The synchronizing signal is a reference signal having a fixed clock frequency, such as horizontal synchronization (HSYNC) signal or vertical synchronization (VSYNC) signal of a display device. However, embodiments of the present invention are not limited thereto. Fixed clock frequencies provided by other devices can be used as well.

[0031] After the power circuit 210 receives the counting number signal, the working voltage outputted by the power circuit 210 is adjusted to enable the counting number signal to be equal to a predetermined counting number. In this embodiment, it is assumed that the frequency of the oscillation frequency f.sub.o of the voltage-controlled oscillator 220 is desired to be 30 MHz and the fixed clock frequency of the VSYNC/HSYNC signal is 3 us, a desired value of the counting number signal of the counter 230 is 100. When the working voltage has an undesired voltage value 1.1V affected by the signal variation, the oscillation frequency f.sub.o of the voltage-controlled oscillator 220 is changed accordingly, and then the counter 230 outputs a counting number signal having an affected value, for example 80. The counting number signal having the affected value 80 is thereafter outputted to the power circuit 210 to perform a voltage adjusting step to adjust the working voltage. Specifically, in the power circuit 210, the affected value 80 is compared to the desired value 100. Since the affected value 80 is smaller than the desired value 100, the power circuit 210 increases the value of the working voltage to, for example 1.2 V to reduce the affection of the signal variation, thereby achieving the purpose of environment monitoring and working voltage adjustment.

[0032] Further, in some embodiments, the voltage adjusting step can be repeated until the value of the counting number signal of the counter 230 is equal to a predetermined counting number, for example 100. Specifically, in the above case that the power circuit 210 increases the value of the working voltage to, for example 1.2 V to reduce the affection of the signal variation, the working voltage of 1.2 V may be not high enough to allow the counter 230 to output the counting number signal having a value of 100. Therefore, the voltage adjusting step is repeated to increase the value of the working voltage to, for example 1.3V to allow the counter 230 to output the counting number signal having the value of 100.

[0033] Further, if the working voltage of 1.3V is too high, the counter 230 accordingly outputs the counting number signal having a value, for example 110. In this case, the power circuit 210 decreases the value of the working voltage to, for example 1.25 V to allow the counter 230 to output the counting number signal having the value of 100.

[0034] In some embodiments, a predetermined counting number range can used to replace the above predetermined counting number. For example, the predetermined counting number range of 100?5 can be used. In other words, the above voltage adjusting step can be repeated until the counter 130 outputs the counting number signal having a value in the predetermined counting number range of 100?5.

[0035] Therefore, as shown in FIG. 2, the above voltage adjusting step is repeated three times to allow the counter 230 to output the counting number signal having the value of 100.

[0036] In some embodiments, plural voltage-controlled oscillators and plural counters are used in the power system for monitoring more power paths and ground paths of the power circuit 210. For example, as shown in FIG. 3, the voltage-controlled oscillators are disposed in the monitored circuit 100, including a first voltage-controlled oscillator 221, a second voltage-controlled oscillator 222 and a third voltage-controlled oscillator 223 for monitoring different environments of different components at different positons in the monitored circuit 100. In this embodiment, the first voltage-controlled oscillator 221 is disposed close to the power circuit 210. The second voltage-controlled oscillator 222 is disposed away from the power circuit 210. The third voltage-controlled oscillator 223 is disposed between the first voltage-controlled oscillator 221 and the second voltage-controlled oscillator 222. Therefore, the first voltage-controlled oscillator 221 is capable of monitoring the environment of the components at the positions close to the power circuit 210 with respect to a first power supply path P.sub.1/first ground path G.sub.1; the second voltage-controlled oscillator 222 is capable of monitoring the environment of the components at the positions away from the power circuit 210 with respect to a second power supply path P.sub.2/second ground path G.sub.2; the third voltage-controlled oscillator 223 is capable of monitoring the environment of the components at the positions between the first voltage-controlled oscillator 221 and the second voltage-controlled oscillator 222 with respect to a third power supply path P.sub.3/third ground path G.sub.3.

[0037] The plural counters (not shown), including a first counter, a second counter and a third counter, are electrically connected to the first voltage-controlled oscillator 221, the second voltage-controlled oscillator 222 and the third voltage-controlled oscillator 223, respectively.

[0038] The first voltage-controlled oscillator 221 is configured to output a first oscillation frequency f.sub.o1 capable of changing in accordance with a first signal variation on the first power supply path P.sub.1/first ground path G.sub.1 of the monitored circuit 100. The first counter is electrically connected to an output of the first voltage-controlled oscillator 221. The first counter is configured to receive the first oscillation frequency f.sub.o1 and to generate a first counting number signal in accordance with the first oscillation frequency f.sub.o1 and the synchronizing signal.

[0039] The first counting number signal is then transmitted to the power circuit 210 to adjust the working voltage outputted to the monitored circuit 100.

[0040] The second voltage-controlled oscillator 222 is configured to output a second oscillation frequency f.sub.o2 capable of changing in accordance with a second signal variation on the second power supply path P.sub.2/second ground path G.sub.2 of the monitored circuit 100. The second counter is electrically connected to an output of the second voltage-controlled oscillator 222. The second counter is configured to receive the second oscillation frequency f.sub.o2 and to generate a second counting number signal in accordance with the second oscillation frequency f.sub.o2 and the synchronizing signal. The second counting number signal is then transmitted to the power circuit 210 to adjust the working voltage outputted to the monitored circuit 100.

[0041] The third voltage-controlled oscillator 223 is configured to output a third oscillation frequency f.sub.o3 capable of changing in accordance with a third signal variation on the third power supply path P.sub.3/third ground path G.sub.3 of the monitored circuit 100. The third counter is electrically connected to an output of the third voltage-controlled oscillator 223. The third counter is configured to receive the third oscillation frequency f.sub.o3 and to generate a third counting number signal in accordance with the third oscillation frequency f.sub.o3 and the synchronizing signal. The third counting number signal is then transmitted to the power circuit 210 to adjust the working voltage outputted to the monitored circuit 100.

[0042] After the power circuit 210 receives the first counting number signal, the second counting number signal and the third counting number signal, the working voltage outputted by the power circuit 210 is adjusted to enable the first counting number signal, the second counting number signal and the third counting number signal to be in a predetermined counting number range. For example, a predetermined counting number range of 1005 can be used. In other words, the working voltage can be adjusted until the first counting number signal, the second counting number signal and the third counting number signal having values within the predetermined counting number range of 100?5. For example, the first counting number signal having the value of 95, the second counting number signal having the value of 102 and the second counting number signal having the value of 105, which is within the predetermined counting number range of 100?5, so the working voltage outputted to the monitored circuit 100 is allowed. In another example, the first counting number signal having the value of 95, the second counting number signal having the value of 102 and the third counting number signal having the value of 110, which is out of the predetermined counting number range of 100?5. Therefore, the power circuit 210 decreases the value of the working voltage to allow the third counter to output the counting number signal having the value in the range of 100?5. The voltage adjusting step is repeated until the first counting number signal of the first counter, the second counting number signal of the second counter and the third counting number signal of the third counter having the values in the range of 100?5. However, in the embodiments of the present invention, the predetermined counting number range is not limit thereto.

[0043] Referring to FIG. 4, FIG. 4 is a schematic diagram showing an internal logic structure of the voltage-controlled oscillator 220 in an embodiment of the invention. The voltage-controlled oscillator 220 includes a NAND gate 601, a NOR gate 602, an inverter 603 and a plurality of capacitors. The NAND gate 601, the NOR gate 602 and the inverter 603 are electrically connected to the power supply path of the monitored circuit 100. The NAND gate 601 has two input pins and one output pin, in which the output pin of the NAND gate 601 is electrically connected to input pins of the NOR gate 602, one of the input pins of the NAND gate 601 is used as an enable pin, and the other input pin of the NAND gate 601 is electrically connected to an output pin of the inverter 603. The NOR gate 602 has two input pins and one output pin, in which the input pins of the NOR gate 602 are electrically connected to each other, and the output pin of the NOR gate 602 is electrically connected to an input pin of the inverter 603. The inverter 603 has an input pin and an output pin, in which the input pin of the inverter 603 is electrically connected to the output pin of the NOR gate 602, and the output pin of the inverter is electrically connected to the other input pin of the NAND gate 601, thereby outputting the oscillation frequency to the counter. One of the capacitors C.sub.1 is electrically connected between the output pin of the NAND gate 601 and the ground path of the monitored circuit 100, and the other capacitor C.sub.2 is electrically connected between the output pin of the NOR gate 602 and the ground path of the monitored circuit 100. In an embodiment of the invention, the voltage-controlled oscillator 220 may be an analog synthesis circuit. In an embodiment of the invention, the monitored circuit 100 is a digital integrated circuit and the first voltage-controlled oscillator 221 may be included in the monitored circuit 100. It should be understood that the first voltage-controlled oscillator 221, the second voltage-controlled oscillator 222 and the third voltage-controlled oscillator 223 are composed of the plurality of logic gates as well.

[0044] As shown in FIG. 5, FIG. 5 is a schematic diagram showing the voltage-controlled oscillator and the counter applied to an analog circuit in an embodiment of the invention. The voltage-controlled oscillator 220 is electrically connected to a power supply path and a ground path to which the analog circuit 500 is electrically connected. The voltage-controlled oscillator 220 is configured to output an oscillation frequency f.sub.o. When the power supply path/ground path have the signal variation due to the working environment, the oscillation frequency f.sub.o outputted from the voltage-controlled oscillator 220 may change accordingly. The counter 230 is electrically connected to an output of the voltage-controlled oscillator 220. The counter 230 is configured to receive the oscillation frequency f.sub.o and to generate a counting number signal in accordance with the oscillation frequency f.sub.o and a synchronizing signal for monitoring the signal variation of the analog circuit 500. Therefore, the working voltage of the analog circuit 500 may be monitored for stable according to the counting number signal. It should be understood that the voltage-controlled oscillator 220 and the counter 230 may be used in many fields as a monitoring system.

[0045] Referring to FIG. 1, a low-dropout regulator (LDO) 240 is further included in the power system. The low-dropout regulator 240 is electrically connected between the power circuit 210 and the monitored circuit 100, in which the low-dropout regulator 240 is configured to stabilize the working voltage supplied by the power circuit 210 to the monitored circuit 100.

[0046] Referring to FIG. 6, FIG. 6 is a schematic diagram showing a phase locked loop (PLL) circuit included in an embodiment of the invention. The phase locked loop circuit 250 is electrically connected between the monitored circuit 100 and the output of the voltage-controlled oscillator 220. The phase locked loop circuit 250 is configured to receive the oscillation frequency f.sub.o and to output an operating frequency f.sub.sto the monitored circuit 100 according to the oscillation frequency f.sub.o. The oscillation frequency f.sub.oand the operating frequency f.sub.s generated by the phase locked loop circuit 250 have a multiple relationship. In an embodiment of the invention, the oscillation frequency f.sub.o outputted from the voltage-controlled oscillator 220 is 30 MHz, and the required operating frequency f.sub.s of the monitored circuit 100 is 120 MHz. After the oscillation frequency f.sub.o is multiplied by the phase locked loop circuit 250, the operating frequency f.sub.s of 120 MHz (four times the oscillation frequency f.sub.o) is generated. When a signal variation on the power supply path and the ground path changes instantaneously, the oscillation frequency f.sub.o generated by the voltage-controlled oscillator 220 may be slow down, resulting in a slowdown in the operating frequency f.sub.s provided to the monitored circuit 100 after being multiplied by the phase locked loop circuit 250. Therefore, the monitored circuit 100 may be slowdown, avoiding errors in the monitored circuit 110 caused by the instantaneous signal variation on the power supply path and the ground path.

[0047] Referring to FIG. 7, FIG. 7 is a flowchart showing a method 300 for monitoring a working environment of a monitored circuit and adjusting a working voltage of the monitored circuit in an embodiment of the invention. The following takes the configuration shown in FIG. 1 as an example for description, in which the voltage-controlled oscillator 220 is disposed outside the monitored circuit 100. The method 300 for monitoring and adjusting the working voltage of the monitored circuit 100 includes steps 301 to 304. First, step 301 is performed to dispose a voltage-controlled oscillator 220 around the monitored circuit 100. The voltage-controlled oscillator 220 is electrically connected to a power supply path and a ground path to which the monitored circuit 100 is electrically connected.

[0048] After step 301 is performed, step 302 is performed to output an oscillation frequency f.sub.o in accordance with a signal variation on a power supply path and a ground path. The oscillation frequency f.sub.o outputted from the voltage-controlled oscillator 220 capable of changing in accordance with the signal variation on the power supply path/ground path of the monitored circuit 100.

[0049] After step 302 is performed, step 303 is performed to generate a counting number signal in accordance with the oscillation frequency f.sub.o and a synchronizing signal by using a counter 230.

[0050] In step 304, step 304 is performed to adjust the working voltage outputted to the power supply path in accordance with the counting number signal by using a power circuit 210. The power circuit 210 receives the counting number signal and the working voltage outputted by the power circuit 210 is adjusted to enable the counting number signal to be equal to a predetermined counting number. Further, the working voltage can be adjusted until the value of the counting number signal of the counter 230 is equal to the predetermined counting number. In some embodiments, a predetermined counting number range can used to replace the predetermined counting number, thereby adjusting the working voltage until the value of the counting number signal of the counter 230 is within the predetermined counting number range.

[0051] In some embodiments, plural voltage-controlled oscillators and plural counters are used in the power system for monitoring more power paths and ground paths of the power circuit 210. In this case, the method 300 further includes more steps for monitoring more power/ground paths. For example, the method 300 is performed to dispose plural voltage-controlled oscillators (such as the above voltage-controlled oscillators 221-223) to monitor more power/ground paths. Since the steps for disposing the voltage-controlled oscillators 221-223 and monitoring corresponding power/ground paths are similar to the steps 301-304, details are not repeated herein.

[0052] However, the descriptions are only preferred embodiments of the invention as mentioned above, and should not limit the scope of implementation of the invention. That is, any simple equivalent changes and modifications made according to the scope of the claim and the contents of the description of the invention are still within the scope of the claim of the invention.