TWI435518B - Power control circuit - Google Patents

Description

Power control circuit

The present invention relates to a power supply control circuit, and more particularly to a power supply control circuit with pulse width modulation.

Pulse Width Modulation (PWM) is a conventional technique in switching mode power supply circuits by controlling the on-time of the switching elements to achieve the required load requirements.

Please refer to FIG. 1 , which is a functional block diagram of a conventional power supply control circuit 1 . The power control circuit 1 has a power supply unit 11, a conversion unit 12, a voltage feedback unit 13, and a control unit 14. The power supply unit 11 outputs a power signal PS. The converting unit 12 outputs a driving signal DS according to the power signal PS to drive a load device L. The voltage feedback unit 13 outputs the feedback signal V _C to the control unit 14 according to the change of the driving signal DS (ie, the load change of the load device L). The control unit 14 outputs a control signal CS according to the feedback signal V _C to control whether one of the switching switches (not shown) of the conversion unit 12 is turned on or off. The control signal CS can control the duty cycle of the switch (ie, control the on time). The driving signal DS generated by the converting unit 12 can be balanced with the load device L by the conduction of the different duty cycles of the switching switch.

For example, when the load device L is lightly loaded, the voltage value of the driving signal DS will rise, and the voltage feedback unit 13 senses the change of the driving signal DS and outputs the feedback signal V _C to be input to the control unit 14. The control unit 14 outputs the control signal CS according to the feedback signal V _{C to} reduce the duty cycle of the switch (ie, reduce the on-time of the switching signal) to reduce the output power of the conversion unit 12, thereby reducing the output power of the power unit 11 and the load device. L reaches equilibrium.

However, in the pulse width modulation technique described above, regardless of any change in the voltage value outputted by the power supply unit 11, the switching frequency of the switching control of the switching signal controlled by the control unit 14 controlled by the control unit 14 is fixed. . In addition, in order to reduce the component volume of the power control circuit 1 and reduce the circuit cost, the switching frequency of the switching switch is designed to be relatively high (for example, up to 1 megahertz), and therefore, the switching loss of the switching unit 12 is also considerable. This in turn causes the efficiency of the power supply control circuit 1 to decrease.

Therefore, how to provide a power control circuit, which can adjust the switching frequency according to the input voltage to reduce the switching loss, thereby improving the efficiency of the power control circuit has become one of the important topics.

In view of the above problems, an object of the present invention is to provide a power supply control circuit that can adjust a switching frequency according to an input voltage to reduce switching loss and thereby improve efficiency.

To achieve the above object, a power supply control circuit according to the present invention includes a power supply unit, a conversion unit, a control unit, and a frequency linear adjustment unit. The power unit outputs a power signal. The conversion unit is electrically connected to the power supply unit and generates a driving signal according to the power signal. The control unit is electrically connected to the conversion unit and generates a control signal to control the conversion unit. The control unit has a frequency adjustment capacitor. The frequency linear adjustment unit is electrically connected to the power supply unit and the frequency adjustment capacitor, and generates a frequency adjustment signal according to the power signal, and the frequency adjustment signal input frequency adjusts the first end of the capacitor to reduce the charging current of the frequency adjustment capacitor, thereby making the control signal Reduce the switching frequency of the conversion unit.

In an embodiment of the invention, the conversion unit is a flyback converter, or a forward converter, or a boost converter, or a buck converter, or a step-up/down converter, or A Cuk converter, or a Sepic converter, or a Zeta converter, or a push-pull converter, or a full bridge converter, or a half bridge converter.

In an embodiment of the invention, the conversion unit has at least one switching element, and the control signal reduces the switching frequency of the conversion unit by reducing the switching frequency of the switching element.

In an embodiment of the invention, the control unit further has a controller, and the frequency adjustment signal reduces the charging current of the frequency adjustment capacitor, thereby reducing the oscillation frequency of the controller.

In an embodiment of the invention, the frequency linear adjustment unit has a first resistor and a second resistor. The first end of the first resistor is electrically connected to the output end of the power unit, and the second end and the second end of the first resistor The first end of the resistor is electrically connected, and the second end of the second resistor is grounded.

In an embodiment of the invention, the frequency linear adjustment unit further has a switching element, the first end of the switching element is electrically connected to the second end of the first resistor, and the second end of the switching element is electrically connected to the frequency adjusting capacitor At the first end, the third end of the switching element is electrically grounded.

In an embodiment of the invention, the switching element and the switching element comprise a bipolar junction transistor, or a field effect transistor, or a metal oxide semiconductor field effect transistor.

In an embodiment of the invention, the power control circuit further includes a voltage feedback unit electrically connected to the conversion unit and the control unit, and generating a voltage feedback signal according to the driving signal.

In an embodiment of the invention, the voltage feedback unit converts the voltage of the driving signal and outputs a voltage feedback signal, so that the control signal changes the duty cycle of the switching element.

In an embodiment of the invention, the control unit outputs the control signal according to the voltage feedback signal and the frequency adjustment signal.

In an embodiment of the invention, the power control circuit further includes a current feedback unit electrically connected to the conversion unit and the control unit, and the current feedback unit outputs a current feedback signal according to the conversion unit for input control. unit.

In an embodiment of the invention, the control unit generates a control signal according to the frequency adjustment signal, the voltage feedback signal, and the current feedback signal to control the switching element.

In an embodiment of the invention, when the voltage value of the power signal is higher, the control unit adjusts the frequency of the frequency adjustment capacitor according to the frequency adjustment signal, thereby reducing the switching frequency of the control signal switching component.

According to the above, the frequency linear adjustment unit of the power control circuit according to the present invention generates a frequency adjustment signal according to the power signal outputted by the power unit, and the frequency adjustment signal is input to the first end of the frequency adjustment capacitor of the control unit. Therefore, the charging current of the frequency adjustment capacitor of the control unit can be reduced according to the voltage level of the power signal output by the power unit, thereby increasing the charging time of the frequency adjusting capacitor, thereby reducing the oscillation frequency of the control IC in the control unit, thereby reducing the conversion. Switching loss of the switching elements of the unit. Compared with the conventional one, the power control circuit of the present invention can adjust (lower) the switching frequency of the switching element of the conversion unit according to the input voltage, thereby reducing the transient loss when the switching element is switched, thereby improving the efficiency of the power control circuit.

DETAILED DESCRIPTION OF THE INVENTION A power supply control circuit in accordance with a preferred embodiment of the present invention will be described with reference to the accompanying drawings, wherein like elements will be described with the same reference numerals.

First embodiment

Please refer to FIG. 2A and FIG. 2B simultaneously, which are respectively a functional block diagram and a circuit diagram of a power control circuit 2 according to the first embodiment of the present invention. The power control circuit 2 is a power supply and can supply power to a load device L according to different load conditions. The load device L can be, for example, an electric product, a mobile phone, a computer, a global position system (GPS), a personal digital assistant (PDA), or other electronic products. Here, there is no limitation.

The power control circuit 2 includes a power supply unit 21, a conversion unit 22, a control unit 23, a frequency linear adjustment unit 24, and a voltage feedback unit 25.

The power unit 21 outputs a power signal PS. Here, the power signal PS is a DC voltage signal. The power signal P may have a fixed voltage level or a variable voltage level. If it is a variable voltage level, its voltage level can vary, for example, between 36 volts and 75 volts. Further, when the load device L is driven by the AC power source, the power supply unit 21 includes a rectifier circuit for causing the output power signal PS to be a DC voltage signal.

The converting unit 22 is electrically connected to the power unit 21, and the converting unit 22 generates a driving signal DS according to the power signal PS to supply the power required by the load device L. The conversion unit 22 is a DC-DC converter, and may be, for example, a flyback converter, a forward converter, or a boost converter, or a buck converter. Or a boost/buck converter, or a Cuk converter, or a Sepic converter, or a Zeta converter, or a push-pull converter, or a full bridge converter, or a half bridge converter. In this embodiment, the conversion unit 22 is exemplified by a flyback converter.

In addition, the conversion unit 22 has at least one switching element 221, and the control unit 23 is electrically connected to the switching element 221 of the conversion unit 22. This embodiment is described by taking a switching element 221 as an example. The control unit 23 generates a control signal CS to control the switching element 221 of the conversion unit 22 to operate. The control signal CS is a pulse width modulation signal, and can control the on and off of the switching element 221, so that the conversion unit 22 outputs the driving signal DS according to the power signal PS.

The voltage feedback unit 25 is electrically connected to the conversion unit 22 and the control unit 23. The voltage feedback unit 25 outputs a voltage feedback signal V _C according to the driving signal DS. In this embodiment, the voltage feedback unit 25 has two resistors R3 and R4 connected in series such that the voltage feedback signal V _C is a divided voltage of the driving signal DS. In other words, the voltage feedback unit 25 divides and converts the voltage of the driving signal DS to output the voltage feedback signal V _C , so that the control signal CS can change the duty cycle when the switching element 221 is switched. Here, the voltage feedback signal V _C is equal to R4 × DS / (R3 + R4).

If the driving signal DS becomes lighter and its voltage level rises, the voltage level of the voltage feedback signal V _C also rises in the same proportion. In other words, when the voltage value of the driving signal DS rises due to the load of the load device L, the voltage feedback unit 25 can output a voltage feedback signal V _C according to the voltage level of the rising driving signal DS, and input the control unit. 23, and the control unit 23 outputs the control signal CS according to the voltage feedback signal V _C to reduce the conduction time of the switching element 221 (ie, reduce the duty cycle of the switching element 221) to reduce the output power of the power unit 21, thereby achieving the power supply. The output of unit 21 is balanced with the power required by load device L.

The control unit 23 is electrically connected to the conversion unit 22 and the frequency linear adjustment unit 24. The control unit 23 generates a frequency adjustment signal FS output control signal CS according to the voltage feedback signal V _C and the frequency linear adjustment unit 24 to control the switching element 221. Here, the control unit 23 integrates the voltage feedback signal V _C and the frequency adjustment signal FS and outputs a control signal CS to control the switching element 221.

The control unit 23 has a frequency adjustment capacitor C1, a frequency adjustment resistor R5 and a controller 231. The controller 231 has a control IC (not shown) and a circuit for driving the switching element 221 to operate. Further, the frequency adjustment capacitor C1 and a frequency adjustment resistor R5 determine the oscillation frequency of the control IC in the controller 231.

The frequency linearity adjustment unit 24 is electrically connected to the power supply unit 21 and the frequency adjustment capacitor C1 of the control unit 23. The frequency linearity adjusting unit 24 generates a frequency adjustment signal FS according to the power signal PS. Here, the frequency linearity adjusting unit 24 generates the frequency adjustment signal FS according to the voltage level of the power signal PS.

The frequency linearity adjusting unit 24 has a first resistor R1, a second resistor R2, and a switching element S1. The first end R11 of the first resistor R1 is electrically connected to the output end of the power source unit 21, the second end R12 of the first resistor R1 is electrically connected to the first end R21 of the second resistor R2, and the second resistor R2 is The two ends R22 are grounded. In addition, the second end R12 of the first resistor R1 is electrically connected to the first end S11 of the switching element S1 via a current limiting resistor R6. The second end S12 of the switching element S1 is electrically connected to the first end C11 of the frequency adjusting capacitor C1, and the third end S13 of the switching element S1 is electrically grounded. The second end S12 of the switching element S1 outputs a frequency adjustment signal FS, and the frequency adjustment signal FS is input to the first end C11 of the frequency adjustment capacitor C1 to reduce the charging current of the frequency adjustment capacitor C1, so that the controller 231 is within the controller 231. The oscillation frequency of the control IC is lowered, thereby causing the control signal CS to lower the switching frequency of the conversion unit 22.

The switching element 221 and the switching element S1 are respectively Bipolar Junction Transistor (BJT), Field Effect Transistor (FET), or Metal Oxide Semiconductor Field Effect Transistor (Metal) -Oxide-Semiconductor Field-Effect Transistor, MOSFET). In the present embodiment, the switching element 221 is exemplified by a metal oxide semiconductor field effect transistor, and the switching element S1 is exemplified by an NPN type double carrier junction transistor. However, this is not a limitation.

Please refer to FIG. 2B again to further explain how the frequency linearity adjusting unit 24 adjusts (reduces) the charging current of the frequency adjusting capacitor C1.

It can be seen from the partial pressure theorem that the voltage level of the node A of the frequency linearity adjusting unit 24 is equal to R2 × PS / (R1 + R2). In other words, the voltage level of the node A is proportional to the voltage level of the power signal PS. If the voltage level of the power signal PS rises, the voltage level of the node A also rises. vice versa.

When the current of the node A is input to the first terminal S11 of the switching element S1 via the current limiting resistor R6, the switching element S1 can be turned on, and the second terminal S12 of the switching element S1 outputs the frequency adjustment signal FS. Here, the current input to the first terminal S11 of the switching element S1 can control the conduction ratio of the switching element S1, so that the current 1 flows to the third terminal S13 via the second end S12 of the switching element S1. Therefore, a part of the charging current originally flowing into the first end C11 of the frequency adjusting capacitor C1 is shunted, and flows from the second end S12 of the switching element S1 to the third end S13, so that the charging current flowing into the frequency adjusting capacitor C1 is reduced. Therefore, the frequency adjustment signal FS can reduce the charging current of the frequency adjustment capacitor C1 of the control unit 23, increase the charging time of the frequency adjustment capacitor C1, and further reduce the oscillation frequency of the control IC in the controller 231. Thereby, the switching frequency of the switching element 221 can be reduced by the control signal CS outputted by the control unit 23. The switching frequency of the switching element 221 is lowered, that is, the number of switching of the switching element 221 is reduced, so that the transient loss when the switching element 221 is switched can be reduced, thereby reducing the loss of the power supply control circuit 2 and improving the efficiency. Therefore, the power control circuit 2 can adjust (lower) the switching frequency of the switching element 221 of the conversion unit 22 according to the power signal PS outputted by the power unit 21, so that the transient loss when the switching element 221 is switched can be reduced, thereby improving the power control circuit. 2 efficiency.

Specifically, since the voltage level of the node A is proportional to the voltage level of the power signal PS, and the current of the first terminal S11 of the input switching element S1 can control the conduction ratio of the switching element S1, the current I is passed through the switching element. The second end S12 of S1 flows to the third end S13. Therefore, the frequency linear adjustment unit 24 of the present invention can linearly adjust the switching frequency of the switching element 221. In addition, when the voltage level of the power signal PS is higher, the voltage level of the node A of the frequency linearity adjusting unit 24 is higher, so that the current of the first terminal S11 of the input switching element S1 is higher, and the switching element S1 is turned on. The higher the ratio, the smaller the charging current of the frequency adjustment capacitor C1, and the more the switching frequency of the control signal CS control switching element 221 is lowered. Therefore, the loss of switching of the power supply control circuit 2 will be lower. When the load is lower, the efficiency of the power supply control circuit 2 can be improved more than the conventional circuit.

Second embodiment

Please refer to FIG. 3A and FIG. 3B simultaneously, which are respectively a functional block diagram and a circuit diagram of a power control circuit 3 according to a second embodiment of the present invention.

The power control circuit 3 includes a power supply unit 31, a conversion unit 32, a control unit 33, a frequency linear adjustment unit 34, and a voltage feedback unit 35. In addition, the main difference between the power supply control circuit 3 of the present embodiment and the power supply control circuit 2 of the first embodiment is that the power supply control circuit 3 further includes a current feedback unit 36. The current feedback unit 36 is a feedforward feedback circuit.

The current feedback unit 36 is electrically connected to the conversion unit 32 and the control unit 33. The current feedback unit 36 generates a current feedback signal RS according to the conversion unit 32 and inputs it to the control unit 33. The current feedback unit 36 converts the primary side input current of the conversion unit 32 to output a current feedback signal RS and inputs it to the control unit 33. In the present embodiment, the current feedback unit 36 is a resistor R7. The current feedback unit 36 converts the current on the primary side of the input conversion unit 32 into a current feedback signal RS by the resistor R7 and inputs it to the control unit 33. In fact, the current feedback signal RS is also a voltage signal.

The control unit 33 generates the control signal CS according to the frequency adjustment signal FS, the voltage feedback signal V _C and the current feedback signal RS to control the switching element 321 . In other words, in the embodiment, the control unit 33 integrates the frequency adjustment signal FS, the voltage feedback signal V _C and the current feedback signal RS and outputs the control signal CS to control the duty cycle and the switching frequency of the switching element 321 . The control signal CS controls the duty cycle of the switching component 321 according to the voltage feedback signal V _C and the current feedback signal RS, and controls the switching frequency of the switching component 321 according to the frequency adjustment signal FS.

In addition, the technical contents of the power supply unit 31, the conversion unit 32, the control unit 33, the frequency linear adjustment unit 34, and the voltage feedback unit 35 of the power supply control circuit 3 can refer to the power supply unit 21, the conversion unit 22, and the control unit 23 of the power supply control circuit. The frequency linearity adjusting unit 24 and the voltage feedback unit 25 are not described herein again.

Therefore, the same as the first embodiment, the frequency adjustment signal FS of the embodiment can reduce the charging current of the frequency adjustment capacitor C1, increase the charging time of the frequency adjustment capacitor C1, and further reduce the control IC in the controller 331. Oscillation frequency. Thereby, the switching frequency of the switching element 321 can be reduced by the control signal CS outputted by the control unit 33, so that the transient loss when the switching element 321 is switched can be reduced, and the power supply control circuit 3 can be reduced and the efficiency can be improved. Therefore, the power control circuit 3 of the present invention can reduce the switching frequency of the switching element 331 of the conversion unit 32 according to the power signal PS outputted by the power supply unit 31, so as to reduce the switching loss of the conversion unit 32, thereby improving the efficiency of the power supply control circuit 3.

In summary, the frequency linear adjustment unit of the power control circuit according to the present invention generates a frequency adjustment signal according to the power signal outputted by the power unit, and the frequency adjustment signal is input to the first end of the frequency adjustment capacitor of the control unit. Therefore, the charging current of the frequency adjustment capacitor of the control unit can be reduced according to the voltage level of the power signal output by the power unit, thereby increasing the charging time of the frequency adjusting capacitor, thereby reducing the oscillation frequency of the control IC in the control unit, thereby reducing the conversion. Switching loss of the switching elements of the unit. Compared with the conventional one, the power control circuit of the present invention can adjust (lower) the switching frequency of the switching element of the conversion unit according to the input voltage, thereby reducing the transient loss when the switching element is switched, thereby improving the efficiency of the power control circuit.

The above is intended to be illustrative only and not limiting. Any equivalent modifications or alterations to the spirit and scope of the invention are intended to be included in the scope of the appended claims.

1, 2, 3. . . Power control circuit

11, 21, 31. . . Power unit

12, 22, 32. . . Conversion unit

13, 25, 35. . . Voltage feedback unit

14, 23, 33. . . control unit

221, 321. . . Switching element

231, 331. . . Controller

24, 34. . . Frequency linear adjustment unit

36. . . Current feedback unit

A. . . node

C1. . . Frequency adjustment capacitor

C11, R11, R12, R21, R22, S11, S12, S13. . . end

CS. . . Control signal

DS. . . Drive signal

FS. . . Frequency adjustment signal

I. . . Current

L. . . Load device

PS. . . Power signal

R1, R2, R3, R4, R5, R6, R7. . . resistance

RS. . . Current feedback signal

S1. . . Switching element

V. . . Voltage

V _C . . . Voltage feedback signal

1 is a functional block diagram of a power control circuit;

2A is a functional block diagram of a power control circuit according to a first embodiment of the present invention;

2B is a schematic circuit diagram of a power control circuit according to a first embodiment of the present invention;

3A is a functional block diagram of a power control circuit according to a second embodiment of the present invention;

FIG. 3B is a schematic circuit diagram of a power control circuit according to a second embodiment of the present invention.

2. . . Power control circuit

twenty one. . . Power unit

twenty two. . . Conversion unit

twenty three. . . control unit

twenty four. . . Frequency linear adjustment unit

25. . . Voltage feedback unit

C1. . . Frequency adjustment capacitor

C11. . . end

CS. . . Control signal

DS. . . Drive signal

FS. . . Frequency adjustment signal

L. . . Load device

PS. . . Power signal

V _C . . . Voltage feedback signal

Claims (12)

A power control circuit includes: a power supply unit that outputs a power signal; a conversion unit electrically connected to the power supply unit and generates a driving signal according to the power signal; and a control unit electrically connected to the conversion unit a connection, and a control signal to control the conversion unit, the control unit has a frequency adjustment capacitor; and a frequency linear adjustment unit electrically connected to the power supply unit and the frequency adjustment capacitor, and generated according to the power signal a frequency adjustment signal, the frequency adjustment signal is input to the first end of the frequency adjustment capacitor to reduce the charging current of the frequency adjustment capacitor, thereby causing the control signal to lower the switching frequency of the conversion unit, wherein the frequency linear adjustment unit has a a first resistor, a second resistor and a switching element, the first end of the first resistor is electrically connected to the output end of the power unit, and the second end of the first resistor is electrically connected to the first end of the second resistor Connecting, the second end of the second resistor is grounded, and the switching element is electrically connected to the first resistor and the second resistor respectively The power control circuit of claim 1, wherein the conversion unit is a flyback converter, or a forward converter, or a boost converter, or a buck converter, or a rise/ Buck converter, or Cuk converter, or Sepic converter, or Zeta converter, or push-pull converter, or full-bridge converter, or half-bridge converter Converter. The power control circuit of claim 1, wherein the conversion unit has at least one switching component, and the control signal reduces the switching frequency of the switching unit by reducing the switching frequency of the switching component. The power control circuit of claim 1, wherein the control unit further comprises a controller, wherein the frequency adjustment signal reduces the charging current of the frequency adjustment capacitor, thereby reducing the oscillation frequency of the controller. The power control circuit of claim 1, wherein the first end of the switching element is electrically connected to the second end of the first resistor, and the second end of the switching element is electrically connected to the frequency adjusting capacitor At the first end, the third end of the switching element is electrically grounded. The power control circuit of claim 3, wherein the switching element and the switching element comprise a bipolar junction transistor, or a field effect transistor, or a metal oxide semiconductor field effect transistor. The power control circuit of claim 3, further comprising: a voltage feedback unit electrically connected to the conversion unit and the control unit, and generating a voltage feedback signal according to the driving signal. The power control circuit of claim 7, wherein the voltage feedback unit converts the voltage of the driving signal and outputs the voltage feedback signal, so that the control signal changes the duty cycle of the switching element. The power control circuit of claim 7, wherein the power control circuit The control unit outputs the control signal according to the voltage feedback signal and the frequency adjustment signal. The power control circuit of claim 7, further comprising: a current feedback unit electrically connected to the conversion unit and the control unit, the current feedback unit outputting a current back according to the conversion unit Grant a signal to enter the control unit. The power control circuit of claim 10, wherein the control unit generates the control signal according to the frequency adjustment signal, the voltage feedback signal and the current feedback signal to control the switching element. The power control circuit of claim 3, wherein when the voltage value of the power signal is higher, the control unit adjusts the signal according to the frequency to make the charging current of the frequency adjusting capacitor smaller, thereby making the control signal The more the switching frequency of the switching element is controlled to decrease.