Patent Application
20130279218
1. Technical Field
The disclosed embodiments relate to a switch circuit and an electronic device.
2. Description of Related Art
An electronic device includes a switch control circuit, a power supply, and a load. The switch control circuit includes a key switch and a control unit. When the electronic device is powered on, the power supply powers the key switch and the load. When the electronic device is powered off, the power supply still powers the key switch and stops powering the load. The key switch generates a first command or a second command in response to an operation by the user. The control unit enables the power supply to power the load in response to the first command or enables the power supply to stop powering the load in response to the second command.
However, when software malfunctions occur in the control unit due to ESD, the control unit may fail to enable the power supply to power the load in response to the first command or may fail to enable the power supply to stop powering the load in response to the second command.
Therefore, there is room for improvement in the art.
Many aspects of the embodiments can be better understood with reference to the following drawings. The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the present embodiments. Moreover, in the drawings, like reference numerals designate corresponding parts throughout two views.
Referring to
The switch circuit 100 includes a filtering unit 10, a key switch 20, a voltage stabilizing unit 30, and a control unit 40. The filtering unit 10 filters a supply voltage from the power supply 200. The key switch 20 establishes an electrical connection between the filtering unit 10 and the voltage stabilizing unit 30 or cuts off the electrical connection in response to an operation by the user. In this embodiment, the key switch 20 is a single pole double throw switch.
When the key switch 20 establishes the electrical connection between the filtering unit 10 and the voltage stabilizing unit 30, the voltage stabilizing unit 30 receives the filtered supply voltage from the filtering unit 10, and coverts the filtered supply voltage to a stabilizing voltage. Therefore, the control unit 40 is charged-up by the stabilizing voltage to generate the first control signal. The first control signal enables the power supply 200 to power the load 300.
When the key switch 20 cuts off the electrical connection between the filtering unit 10 and the voltage stabilizing unit 30, the voltage stabilizing unit 30 stops receiving the filtered supply voltage from the filtering unit 10, and stops outputting the stabilizing voltage. Therefore, the control unit 40 is discharged to generate a second control signal, the second control signal enables the power supply 200 to stop powering the load 300. In this embodiment, the power supply 200 provides the supply voltage to the filtering unit 10 and powers the load 300 when the electronic device 900 is powered on. In addition, the power supply 200 provides a supply voltage to the filtering unit 10 and stops powering the load 300 when the electronic device 900 is powered off. In other embodiments, the voltage stabilizing unit 30 is not included in the switch circuit 100, and furthermore, the filtering unit 10 is also not included in the switch circuit 100.
Referring to
The voltage stabilizing unit 30 includes a zener diode D2, a limiting resistor R2, a capacitor C2, and a diode D1. An anode of the zener diode D2 is grounded, an anode of the diode D1 is connected to the key switch 20 through the limiting resistor R2, a cathode of the diode D1 is connected to a cathode of the zener diode D2. The cathode of the zener diode D2 is connected to the control unit 40. One end of the capacitor C2 is connected to the anode of the diode D1, and the other end of the capacitor C2 is grounded.
The control unit 40 includes a capacitor C3, a first dividing resistor R3, and a second dividing resistor R4. An anode of the capacitor C3 is connected to the cathode of the zener diode D2, a cathode of the capacitor C3 is grounded. One end of the first dividing resistor R3 is connected to the anode of the capacitor C3, and the other end of the first dividing resistor R3 is grounded through the second dividing resistor R4; the other end of the first dividing resistor R3 is further connected to the power supply 200.
In this embodiment, the capacitance of the capacitor C3 is adjustable. In other embodiments, the resistance of the first dividing resistor R3 is adjustable, and the resistance of the second dividing resistor R4 is adjustable. In still other embodiments, the resistance of one of the first dividing resistor R3 and the second dividing resistor R4 is adjustable.
In the electronic device 900, when the key switch 20 establishes the electrical connection between the filtering unit 10 and the voltage stabilizing unit 30 in response to an operation from the user, the capacitor C3 is charged-up by the stabilizing voltage generated by the stabilizing circuit 30 to generate the first control signal, therefore the power supply 200 is enabled by the first control signal to power the load 300.
When the key switch 20 cuts off the electrical connection between the filtering unit 10 and the voltage stabilizing unit 30 in response to an operation by the user, the capacitor C3 is discharged to generate the second control signal, therefore the power supply 200 is enabled by the second control signal to stop powering the load 300. Compared to the prior art, the control signals are generated by hardware and not software, and hence malfunctions in the switch circuit 100 to cause the power supply 200 to be failed to power the load 300 or stop powering the load 300 is minimized or non-existence.
Alternative embodiments will become apparent to those skilled in the art without departing from the spirit and scope of what is claimed. Accordingly, the present disclosure should not be deemed to be limited to the above detailed description, but rather only by the claims that follow and the equivalents thereof.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201210119734.2 | Apr 2012 | CN | national |
