TWI416298B - Voltage regulation circuit and power adapter using the same - Google Patents

Abstract

A voltage regulation circuit, includes a voltage division circuit, a reference voltage generation circuit and an impedance regulation circuit. The voltage division circuit includes a first voltage reference terminal and a second voltage reference terminal, and the second voltage reference terminal is connected to the voltage output terminal of the voltage regulation circuit. The reference voltage generation circuit includes a third voltage reference terminal, which outputs a stable reference voltage to the first voltage reference terminal, to stabilize the voltage of the first voltage reference terminal at the reference voltage. The impedance regulation circuit provides an equivalent impedance for the first voltage reference terminal, when the current of the voltage output terminal changes, the impedance value of the equivalent impedance changes pursuant to the current. The voltage division circuit regulates the voltage of the voltage output terminal under the co-actions of the reference voltage generation circuit and the impedance regulation circuit. The present invention also provides a power adapter with such a voltage regulation circuit.

Description

Voltage regulating circuit and power adapter having the same

The present invention relates to a voltage regulating circuit, and more particularly to a voltage regulating circuit capable of compensating for voltage loss caused by impedance of a transmission line and a power adapter having the voltage regulating circuit.

The power adapter is used to output a standard operating voltage to an external device for the external device to work properly. At present, the power adapters use 1m or 1.5m, and even longer transmission lines can be connected to external devices. However, due to the certain impedance on the transmission line, when there is current flowing, the voltage loss on the transmission line will cause the external device to actually receive. The voltage reached is lower than its standard operating voltage, which may result in system instability of the external device.

In view of the above, it is necessary to provide a voltage regulating circuit capable of effectively performing voltage compensation on a voltage loss on a transmission line and providing a stable output voltage.

It is also necessary to provide a power adapter including the voltage regulating circuit capable of effectively voltage-compensating the voltage loss on the transmission line to provide a stable output voltage to the power adapter.

A voltage regulating circuit includes a voltage dividing circuit, a reference voltage generating circuit and an impedance adjusting circuit, wherein the voltage dividing circuit has a first voltage reference end and a second voltage reference end, and the voltage of the second voltage reference end and the voltage regulating circuit The output is connected. The reference voltage generating circuit has a third voltage reference terminal for outputting a stable reference voltage, and the third voltage reference terminal is connected to the first voltage reference terminal of the voltage dividing circuit, thereby connecting the voltage of the first voltage reference terminal Limited to this reference voltage. The impedance adjusting circuit is connected to the voltage output end of the voltage regulating circuit and the first voltage reference end, and is configured to provide an equivalent impedance to the first voltage reference end, and the impedance value of the equivalent impedance is output current at the voltage output end of the voltage regulating circuit When a change occurs, a corresponding change is made according to the change of the current. The voltage dividing circuit adjusts the voltage of the second voltage reference terminal under the joint action of the reference voltage generating circuit and the impedance adjusting circuit, thereby adjusting the voltage of the voltage output terminal of the voltage regulating circuit.

A power adapter includes an alternating current interface, an AC/DC circuit, a voltage regulating circuit, and an output port for connecting an external alternating current to supply current to the AC/DC circuit, and the AC/DC circuit converts the alternating current into a direct current input voltage adjusting circuit The voltage regulating circuit then adjusts the direct current to a suitable voltage output to the output port. The voltage regulating circuit includes a voltage dividing circuit, a reference voltage generating circuit and an impedance adjusting circuit, and the voltage dividing circuit has a first voltage reference end and a second voltage reference end, and the voltage output of the second voltage reference end and the voltage regulating circuit End connection. The reference voltage generating circuit has a third voltage reference terminal for outputting a stable reference voltage, and the third voltage reference terminal is connected to the first voltage reference terminal of the voltage dividing circuit, thereby connecting the voltage of the first voltage reference terminal Limited to this reference voltage. The impedance adjusting circuit is connected to the voltage output end of the voltage regulating circuit and the first voltage reference end for reference to the first voltage The terminal provides an equivalent impedance, and the impedance value of the equivalent impedance changes correspondingly according to the change of the current when the output current of the voltage output terminal of the voltage regulating circuit changes. The voltage dividing circuit adjusts the voltage of the second voltage reference terminal under the joint action of the reference voltage generating circuit and the impedance adjusting circuit, thereby adjusting the voltage of the voltage output terminal of the voltage regulating circuit.

The voltage regulating circuit of the present invention can limit the voltage of the first voltage reference terminal of the voltage dividing circuit through the third voltage reference end of the reference voltage generating circuit according to different voltage losses generated by different transmission lines connected, and automatically through the impedance adjusting circuit The ground impedance of the first voltage reference terminal is dynamically adjusted to adjust the output voltage of the power adapter to offset the voltage loss on the transmission line for voltage compensation purposes.

100‧‧‧Power adapter

10‧‧‧AC interface

20‧‧‧AC/DC circuit

30‧‧‧Voltage adjustment circuit

31‧‧‧ Voltage dividing circuit

32‧‧‧reference voltage generation circuit

33‧‧‧ Impedance adjustment circuit

40‧‧‧ Output埠

50‧‧‧ transmission line

60‧‧‧External equipment

1 is a functional block diagram of a power adapter in accordance with an embodiment of the present invention, the power adapter having a voltage regulating circuit.

2 is a detailed circuit diagram of the voltage regulating circuit of FIG. 1.

Referring to FIG. 1, a power adapter 100 is composed of an AC interface 10, an AC/DC circuit 20, a voltage regulation circuit 30, and an output port 40. Wherein, the AC interface 10 is used to connect the external AC power Vin to supply current to the AC/DC circuit 20, and the AC/DC circuit 20 converts the AC power Vin into the DC power input voltage adjustment circuit 30, and the voltage adjustment circuit 30 adjusts the DC power to a suitable voltage. Uout is output to output 埠40.

Referring to FIG. 2, in the embodiment, the voltage regulating circuit 30 includes a voltage dividing circuit 31, a reference voltage generating circuit 32, and an impedance adjusting circuit 33. The voltage dividing circuit 31 has a first voltage. Reference end A1 and second voltage reference end A2, the first The two voltage reference terminal A1 is connected to the voltage output terminal Vout of the voltage regulating circuit 30. The reference voltage generating circuit 32 has a third voltage reference terminal R for outputting a stable reference voltage, and the third voltage reference terminal R is connected to the first voltage reference terminal A1 of the voltage dividing circuit 31, thereby The voltage of a voltage reference terminal A1 is limited to the reference voltage. The impedance adjusting circuit 33 is connected to the voltage output terminal Vout of the voltage regulating circuit 30 and the first voltage reference terminal A1 for providing an equivalent impedance to the first voltage reference terminal A1. The impedance value of the equivalent impedance is in the voltage regulating circuit 30. When the output current of the voltage output terminal Vout changes, a corresponding change is made according to the change of the current. The voltage dividing circuit 31 adjusts the voltage of the second voltage reference terminal A2 by the reference voltage generating circuit 32 and the impedance adjusting circuit 33, thereby adjusting the voltage of the voltage output terminal Vout of the voltage regulating circuit 30.

In the present embodiment, the voltage dividing circuit 31 includes a first voltage dividing resistor R1 and a second voltage dividing resistor R2 connected in series, and a connection node of the first voltage dividing resistor R1 and the second voltage dividing resistor R2 constitutes the first voltage. The first voltage-dividing resistor R1 is grounded away from one end of the first voltage reference terminal A1, and the second voltage-dividing resistor R2 is away from the first voltage reference terminal A1 to form a second voltage reference terminal A2. The reference terminal A2 is connected to the voltage output terminal Vout of the voltage regulating circuit 30, and is connected to the voltage input terminal V'in through the inductor L1 and the diode D1. In the embodiment, the input voltage of the voltage input terminal V'in is AC. The output voltage of the /DC circuit 20.

The reference voltage generating circuit 32 includes a voltage regulator D2 and an optical coupler U1. The anode A of the voltage regulator D2 is grounded, and the cathode C passes through the optical coupler U1 and the voltage of the diode D1 and the voltage regulating circuit 30. The input terminal V'in is connected, and the voltage regulator D2 further has a reference terminal R, which constitutes a third voltage reference terminal R of the reference voltage generating circuit 32. The reference terminal R is connected to the cathode C through a capacitor C3 and a resistor R3. The Zener diode D2 obtains an operating voltage through the optical coupler U1 and outputs a stable reference voltage Uref at its reference terminal R, thereby limiting the voltage of the first voltage reference terminal A1 to the reference voltage Uref.

The impedance adjusting circuit 33 includes a first switching element Q1 and a second switching element Q2, wherein the first switching element Q1 and the second switching element Q2 each include a control end and first and second conduction ends. In this embodiment, when there is a certain voltage difference between the control terminal of the first switching element Q1 and the second switching element Q2 and the first conducting terminal, the first switching element Q1 and the second switching element Q2 are in an on state. Otherwise deadline. When the control terminal and the first conduction terminal are at different voltage differences, the first switching element Q1 and the second switching element Q2 are both at different conduction levels and have different conduction internal resistances.

In the present embodiment, the first switching element Q1 uses a PNP transistor, and the second switching element Q2 uses an NPN transistor. The control ends of the first switching element Q1 and the second switching element Q2 correspond to the base of the triode, the first conducting end corresponds to the emitter of the triode, and the second conducting end corresponds to the collector of the triode. The base of the PNP transistor Q1 is connected to the voltage output terminal Vout of the voltage regulating circuit 30 through the resistor R4, the emitter of Q1 is connected to the voltage output terminal Vout through the inductor L1, and the collector of the Q1 is connected to the base of the NPN transistor Q2. . The emitter of the NPN transistor Q2 is grounded, and the collector is connected to the first voltage reference terminal A1 of the voltage regulating circuit 30 via a resistor R5.

In the present embodiment, the first voltage dividing resistor R1 and the second voltage dividing resistor R2 are resistors having a large impedance value. When the voltage output terminal Vout is not connected to the external device 60, that is, when the load is idling, the inductor L1 flows first. The current of the circuit composed of the voltage dividing resistor R1 and the second voltage dividing resistor R2 is very small, the voltage drop across the inductor L1 is close to zero, and no voltage drop occurs on the resistor R4. Therefore, the voltage difference between the base and the emitter of the PNP transistor Q1 is zero, and Q1 is turned off, so that the base of the NPN transistor Q2 has no input current flowing, and therefore, Q2 is also turned off. At this time, the voltage regulating circuit 30 outputs a stable voltage value Uout at the voltage output terminal Vout of the voltage regulating circuit 30 through the Zener diode D2, the first voltage dividing resistor R1, and the second voltage dividing resistor R2. The voltage value Uout= (R1 + R2) * Uref / R1, the voltage value Uout is preset to be equal to the standard operating voltage required by the external device 60 connected to the power adapter 100.

When the voltage output terminal Vout is connected to the external device 60 through the transmission line 50, the voltage output terminal Vout and the load of the external device 60 form a loop, so that the output current is not zero, and the transmission line 50 has a certain voltage drop due to a certain impedance, and the external The voltage value actually obtained by the device 60 is smaller than its operating voltage Uout.

At this time, the inductor L1 and the resistor R4 respectively generate a voltage drop due to the current flowing. The emitter and the base of the PNP transistor Q1 have a voltage difference between the emitter L1 and the resistor R4 in series, so the PNP transistor Q1 is turned on. . The base of the NPN transistor Q2 is connected to the voltage output terminal through the turned-on PNP transistor Q1 and the inductor L1 to obtain a voltage, and thus the NPN transistor Q2 is also turned on. At this time, the total resistance of the resistance R5 and the conduction internal resistance Rq2 of the NPN transistor Q2 constitutes the equivalent parallel impedance of the second voltage dividing resistor R2, thereby reducing the impedance to the ground of the first voltage reference terminal A1. At this time, the output voltage Uout = (R2+R1//(R5+Rq2))*Uref/(R1//(R5+Rq2)), the output voltage Uout is increased to compensate for the voltage loss on the transmission line 50, so that the voltage acquired by the external device 60 It is equal to its working voltage.

For the same external device 60, the longer the transmission line 50, the greater the impedance of the transmission line 50, the greater the voltage drop across the transmission line 50, so that the same supply voltage is transmitted. The voltage value will be smaller after the line 50 is transmitted to the external device 60. At this time, the external device 60 cannot operate normally because the input voltage is less than its standard operating voltage, and its equivalent impedance is lowered, resulting in the voltage output terminal Vout of the voltage regulating circuit 30 being provided. The output current to the external device 60 becomes large. At this time, the current flowing through the inductor L1 and the resistor R4 becomes large, and the potential difference between the inductor L1 and the resistor R4 also increases, so that the voltage difference between the base and the emitter of the PNP transistor Q1 increases, and the conduction degree of the PNP transistor Q1 increases. As the voltage increases, the voltage of the base of the NPN transistor Q2 rises, so that the conduction degree of the NPN transistor Q2 also becomes larger, and the conduction internal resistance of the NPN transistor Q2 decreases, resulting in a decrease in the equivalent parallel impedance of the resistor R2, and the voltage output terminal Vout The voltage is boosted higher to offset the voltage drop across the transmission line 50, thereby achieving voltage compensation.

The voltage regulating circuit 30 of the present invention can limit the voltage of the first voltage reference terminal A1 of the voltage dividing circuit 31 through the third voltage reference terminal R of the reference voltage generating circuit 32 according to different voltage losses generated by the different transmission lines 50 that are accessed. And the impedance of the first voltage reference terminal A1 is automatically and dynamically adjusted by the impedance adjusting circuit 33, thereby adjusting the output voltage of the power adapter 100 to offset the voltage loss on the transmission line 50, thereby achieving the purpose of voltage compensation.

It is to be understood by those skilled in the art that the above embodiments are only intended to illustrate the invention, and are not intended to limit the invention, as long as it is within the spirit of the invention Changes and modifications are intended to fall within the scope of the invention.

30‧‧‧Voltage adjustment circuit

31‧‧‧ Voltage dividing circuit

32‧‧‧reference voltage generation circuit

33‧‧‧ Impedance adjustment circuit

Claims (10)

A voltage regulating circuit is improved, comprising: a voltage dividing circuit, a reference voltage generating circuit and an impedance adjusting circuit, the voltage dividing circuit has a first voltage reference end and a second voltage reference end, the second voltage reference end and the voltage The voltage output terminal of the regulating circuit is connected; the reference voltage generating circuit has a third voltage reference terminal for outputting a stable reference voltage, and the third voltage reference terminal is connected to the first voltage reference terminal of the voltage dividing circuit, thereby Limiting the voltage of the first voltage reference terminal to the reference voltage; the impedance adjusting circuit is connected to the voltage output end of the voltage regulating circuit and the first voltage reference end, and is configured to provide an equivalent impedance to the first voltage reference end, the equivalent The impedance value of the impedance changes correspondingly according to the change of the current when the output current of the voltage output terminal of the voltage regulating circuit changes; the voltage dividing circuit adjusts the first step under the joint action of the reference voltage generating circuit and the impedance adjusting circuit The voltage at the voltage reference terminal, thereby adjusting the voltage at the voltage output of the voltage regulating circuit. The voltage regulating circuit of claim 1, wherein the voltage dividing circuit comprises a first voltage dividing resistor and a second voltage dividing resistor connected in series with each other, the first voltage dividing resistor and the second voltage dividing resistor The connecting node constitutes the first voltage reference end, and the end of the second voltage dividing resistor away from the first voltage reference end constitutes a second voltage reference end. The voltage regulating circuit of claim 1, wherein the reference voltage generating circuit comprises a voltage regulator, the voltage regulator having a reference end, the reference terminal forming a third voltage reference end of the reference voltage generating circuit, It is used to output a stable reference voltage to limit the voltage of the first voltage reference terminal to the reference voltage. The voltage regulating circuit of claim 1, wherein the impedance adjustment The circuit includes a first switching element and a second switching element, the first switching element and the second switching element each include a control end and first and second conduction ends, and the control end of the first switching component passes through a third resistor The voltage output terminal of the voltage regulating circuit is connected, the first conducting end is connected to the voltage output end through an inductor, the second conducting end is connected to the control end of the second switching element, the first conducting end of the second switching element is grounded, and the second The conductive terminal is connected to the first voltage reference terminal of the voltage regulating circuit through a fourth resistor. The voltage regulating circuit of claim 4, wherein when a predetermined voltage difference is reached between the control end of the first switching element and the second switching element and the first conducting end, the first switching element and The second switching element is in an on state, otherwise turned off; when the control terminal and the first conduction end are at different voltage differences, the first switching element and the second switching element are both at different conduction levels and have different conduction internal resistances. The voltage regulating circuit of claim 5, wherein the first switching element uses a PNP transistor, the second switching element uses an NPN transistor, and the control terminal of the first switching element and the second switching element corresponds to a triode The base of the transistor corresponds to the emitter of the transistor, and the second terminal corresponds to the collector of the transistor. A power adapter includes an alternating current interface, an AC/DC circuit, a voltage regulating circuit, and an output port for connecting an external alternating current to supply current to the AC/DC circuit, and the AC/DC circuit converts the alternating current into a direct current input voltage adjusting circuit The voltage regulating circuit adjusts the direct current to a suitable voltage output to the output port. The improvement is that the voltage regulating circuit includes a voltage dividing circuit, a reference voltage generating circuit and an impedance adjusting circuit, and the voltage dividing circuit has a first voltage reference. And a second voltage reference terminal connected to the voltage output terminal of the voltage regulating circuit; the reference voltage generating circuit has a third voltage reference terminal for outputting a stable parameter Testing the voltage, the third voltage reference terminal is connected to the first voltage reference terminal of the voltage dividing circuit, thereby limiting the voltage of the first voltage reference terminal to the reference voltage; the voltage regulating terminal of the impedance adjusting circuit and the voltage regulating circuit and a voltage reference terminal is connected to provide an equivalent impedance to the first voltage reference terminal, and the impedance value of the equivalent impedance is changed according to the change of the current when the output current of the voltage output terminal of the voltage regulating circuit changes The voltage dividing circuit adjusts the voltage of the second voltage reference terminal under the joint action of the reference voltage generating circuit and the impedance adjusting circuit, thereby adjusting the voltage of the voltage output terminal of the voltage regulating circuit. The power adapter of claim 7, wherein the voltage dividing circuit comprises a first voltage dividing resistor and a second voltage dividing resistor connected in series, and the first voltage dividing resistor is connected to the second voltage dividing resistor. The node constitutes the first voltage reference end, and the end of the second voltage dividing resistor away from the first voltage reference terminal constitutes a second voltage reference end. The power adapter of claim 7, wherein the reference voltage generating circuit comprises a voltage regulator, the voltage regulator having a reference end, the reference terminal forming a third voltage reference end of the reference voltage generating circuit, A stable reference voltage is output to limit the voltage of the first voltage reference terminal to the reference voltage. The power adapter of claim 7, wherein the impedance adjustment circuit includes a first switching element and a second switching element, the first switching element and the second switching element each including a control end and the first and the a second conducting end, the control end of the first switching component is connected to the voltage output end of the voltage regulating circuit through a third resistor, the first conducting end is connected to the voltage output end through an inductor, and the second conducting end and the second switching component are The control terminal is connected, the first conductive terminal of the second switching component is grounded, and the second conductive terminal is connected to the first voltage reference terminal of the voltage regulating circuit through a fourth resistor.