Patent Application
20130241517
1. Technical Field
The present disclosure relates to power circuits and, particularly, to a power circuit having a three-terminal regulator capable of increasing power output efficiency.
2. Description of the Related Art
A power circuit employed in an electronic device may include a three-terminal regulator for converting a higher voltage to a lower voltage, which results in a low efficiency and a high heat loss or consumption. Referring to
The components in the drawings are not necessarily drawn to scale, the emphasis instead being placed upon clearly illustrating the principles of the disclosure. Moreover, in the drawing, like reference numerals designate corresponding parts throughout the several views.
Referring to
In the embodiment, the three-terminal regulator 23 is capable of detecting a voltage value at the regulator output port 233 and enabling or disabling the input port 230 depending on the detected voltage value. If the three-terminal regulator 23 determines the detected voltage value is less than a predetermined voltage value, the three-terminal regulator 23 enables the input port 230 to receive voltage signals output by the voltage regulating circuit 24. If the three-terminal regulator 23 determines the detected voltage value is equal to or greater than the predetermined value, the three-terminal regulator 23 disables the input port 230. In the embodiment, the predetermined voltage value is 3.3V.
In the embodiment, the voltage regulating circuit 24 includes a transformer T and a diode D. The transformer T includes a primary coil T1 and a secondary coil T2. The primary coil T1 is connected between the power input port 21 and the input port 230 of the three-terminal regulator 23. A first terminal of the secondary coil T2 is connected to the power output port 22, a second terminal of the secondary coil T2 is grounded via the diode D which is connected in reverse. The charge/discharge circuit 25 includes a capacitor C. A first terminal of the capacitor C is connected to the power output port 22 and a second terminal is grounded.
When a power supply (not shown) is connected to the power input port 21 for powering an electronic device (not shown) connected to the power output port 22, the voltage value of the power input port 21 is equal to the voltage value of the power supply, and the voltage value of the power output port 22 is zero. Thereby, the voltage value of the regulator output port 233 of the three-terminal regulator 23 is equal to that of the power output port 22, namely zero, and the three-terminal regulator 23 determines that the voltage value of the regulator output port 233 is lower than the predetermined value and so enables the input port 230. The electric current provided by the power supply flows into the voltage regulating circuit 24 to drive the primary coil T1 to generate induction. The secondary coil T2 generates voltage according to the generated induction. Then the current flowing through the primary coil T1 is also provided to the three-terminal regulator 23 to charge the capacitor C of the charge/discharge circuit 25. Therefore, a portion of the power provided by the power supply is conducted to secondary coil T2, and another portion of the power provided by the power supply is conducted to the three-terminal regulator C to charge the charge/discharge circuit 25.
The voltage value of the power output port 22 increases following the increase of the voltage across the capacitor C of the charge/discharge circuit 25. When the voltage value of power output port 22 is equal to or greater than the predetermined voltage value, the three-terminal regulator 23 disables the input port 230, thereby the current provided by the power supply flows only to the primary coil T1 and the secondary coil T2 generates a voltage accordingly. Then the voltage generated by the secondary coil T2 and the voltage provided by the capacitor C are used for powering the electronic device connected to the power output port 22.
The power supply transition efficiency is computed by a formula: P′=(Vout1+Vout2)Vin=(Vout1++Vout2)/U, wherein Vout1 is the voltage value of the secondary coil T2, Vout2 is the voltage value of the capacitor C of the charge/discharge circuit 25, namely 3.3V, and U is the voltage value of the power supply 20. If the voltage value provided by the power supply is 12V, the power supply transition efficiency can be easily determined.
The power converted to heat and thus lost is computed by a formula: Pd′=(Vin*P′−Vout2)*I=(U*P′−Vout2)*I, wherein, the I is the current output by the secondary coil T2 and the capacitor C of the voltage regulating circuit 24. If the current output by the secondary coil T2 and the capacitor C of the voltage regulating circuit 24 is 0.5 A, the heat consumption efficiency can be easily determined.
Therefore, the power supply transition efficiency P′ of the power circuit 20 of the present embodiment is greater than the power supply transition efficiency P of the power circuit 20 of related art, and the consumption or loss Pd′ of the power circuit 20 of the present embodiment is less than the consumption Pd of the power circuit 10 of the related art.
The voltage value of the capacitor C of the voltage regulating circuit 25 reduces when power to the electronic device is continued, and the voltage value of the power output port 22 is reduced accordingly. When the voltage value of the power output port 22 is less than the predetermined voltage, the three-terminal regulator 23 enables the input port 230. The current provided by the power supply once again charges the capacitor C of the charge/discharge circuit 25.
It is understood that the present disclosure may be embodied in other forms without departing from the spirit thereof. Thus, the present examples and embodiments are to be considered in all respects as illustrative and not restrictive, and the disclosure is not to be limited to the details given herein.
| Number | Date | Country | Kind |
|---|---|---|---|
| 201210069302.5 | Mar 2012 | CN | national |
