Load identification system
A load identification system includes an AC-power input unit, a load, a zero-crossing detector, a microcontroller, a first and a second current phase detectors. The zero-crossing detector is configured to output a zero-voltage pulse signal when a zero-crossing signal of the AC-power input unit is detected. The first current phase detector detects a current flowing through the load to output a first voltage signal. When the current flows along a first direction, the first voltage signal is at a high level. The second current phase detector is configured to detect the current flowing through the load to output a second voltage signal. When the current flows along a second direction, the second voltage signal is at a high level. The microcontroller is configured to receive and identify the type of the load according to the zero-voltage pulse signal, the first and the second voltage signals.
1. A load identification system, comprising:
an AC power input component;
a load, coupled to the AC power input component;
a zero-crossing detection circuit, coupled to the AC power input component, configured to output a zero-voltage pulse signal when a zero-crossing signal of the AC power input component is detected;
a first current phase detection circuit, coupled to the AC power input component, configured to detect a current flowing through the load to output a first voltage signal, wherein the first voltage signal is at a high level when the current flows along a first direction;
a second current phase detection circuit, coupled to the AC power input component, configured to detect the current flowing through the load to output a second voltage signal, the second voltage signal is at the high level when the current flows along a second direction; and
a control circuit, configured to receive the zero-voltage pulse signal, the first voltage signal and the second voltage signal and to identify a type of the load according to the zero-voltage pulse signal, the first voltage signal and the second voltage signal;
wherein the first current phase detection circuit comprises a first comparator and a first resistance, the second current phase detection circuit comprises a second comparator and a second resistance, the first resistance, the second resistance and the load are connected in series.
2. The load identification system of claim 1 , wherein if the zero-voltage pulse signal has a peak value at a first time, and the first voltage signal or the second voltage signal turns from the high level to a low level at the first time, the control circuit identifies the load as a resistive load.
3. The load identification system of claim 1 , wherein if the zero-voltage pulse signal has a peak value at a first time, and the first voltage signal or the second voltage signal turns from the high level to a low level after the first time, the control circuit identifies the load as an inductive load.
4. The load identification system of claim 1 , wherein if the zero-voltage pulse signal has a peak value at a first time, and the first voltage signal or the second voltage signal turns from the high level to a low level before the first time, the control circuit identifies the load as a capacitive load.
5. The load identification system of claim 1 , wherein the zero-crossing detection circuit comprises an optical coupler.
6. The load identification system of claim 1 , wherein when the current is flowing through the first resistance along the first direction, if the zero-voltage pulse signal has a peak value while the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as a resistive load.
7. The load identification system of claim 1 , wherein when the current flowing through the second resistance along the second direction, if the zero-voltage pulse signal has a peak value while the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as a resistive load.
8. The load identification system of claim 1 , wherein when the current flowing through the first resistance along the first direction, if the zero-voltage pulse signal has a peak value before the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as an inductive load.
9. The load identification system of claim 1 , wherein when the current flowing through the second resistance along the second direction, if the zero-voltage pulse signal has a peak value before the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as an inductive load.
10. The load identification system of claim 1 , wherein when the current flowing through the first resistance along the first direction, if the zero-voltage pulse signal has a peak value after the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as a capacitive load.
11. The load identification system of claim 1 , wherein when the current flowing through the second resistance along the second direction, if the zero-voltage pulse signal has a peak value after the first voltage signal is turning from the high level to a low level, the control circuit identifies the load as a capacitive load.
12. The load identification system of claim 1 , wherein a first input terminal of the first comparator is configured to receive the current, a second input terminal of the first comparator is configured to receive a system low voltage, a first input terminal of the second comparator is configured to receive the current, a second input terminal of the second comparator is configured to receive the system low voltage.
13. The load identification system of claim 1 , wherein a first input terminal of the first comparator is coupled to a first terminal of the first resistance, a second terminal of the first resistance and a first terminal of the second resistance are coupled to ground, a first input terminal of the second comparator is coupled to a second terminal of the second resistance.
14. The load identification system of claim 1 , wherein when the current flowing through the first resistance has the first direction, the first voltage signal is at the high level, the second voltage signal is at a low level.
15. The load identification system of claim 1 , wherein when the current flowing through the second resistance has the second direction, the second voltage signal is at the high level, the first voltage signal is at a low level.