TWI418125B - Switched-mode power supplies and control methods thereof - Google Patents

Description

Switching power supply and control method thereof

The present invention is related to a power supply and an operating method utilized therein.

Constant current control has been the desired goal of many power supplies. For example, for a power supply in the field of lighting, the power supply should provide a certain current output when the light is emitted, and the constant current output should not be 100V or 220V with the input line voltage. Variety.

For today's power supplies, power factor is also a key consideration. To put it simply, a power supply with good power can be regarded as a resistor equivalent to the input grid line, and its input line voltage is substantially in phase with the input line current. . The power supply of the good cause provides power factor correction (PFC), which can effectively use the power given by the power company.

However, how to achieve constant current control and power factor correction depends on the designer's creativity and skill.

Figure 1 is a diagram of a conventional switched mode power supply 8 architecture, which is a buck converter. The load 16 in FIG. 1 is exemplified by a light-emitting diode string and a capacitor.

The bridge rectifier 12 integrates the AC mains of the AC terminal into DC and outputs it to the line voltage terminal IN. Line voltage terminal IN line voltage V _IN will generally M-shaped waveform. In the conversion module 10, the shorted power switch 15 causes the main winding PRM to store energy; the open power switch 15 causes the main winding PRM to discharge through the diode 11. A feedback module 20 detects the voltage across the load 16 and transmits the feedback signal V _FB through the optical coupler 23. The controller 18 can be a pulse-width modulator (PWM) that controls the current flowing through the main winding PRM in response to the feedback signal V _FB . Operating power supply source 14, having an auxiliary winding AUX, produces an operating voltage _VCC required by controller 18. The controller 18 detects the current detection signal V _{CS of the} current detecting resistor 24 and provides the gate signal V _{GATE to} turn the power switch 15 on or off.

Figure 2 illustrates a conventional controller 18. Logic control 82 generates a gate signal V _GATE based on the output of comparator 88 and clock generator 87. It is known to those skilled in the art that the feedback signal V _FB can be regarded as a limiting signal that controls the peak value of the current detecting signal V _CS and also controls the peak current flowing through the main winding PRM.

An embodiment of the present invention provides a control method for a switching power supply having an inductive component coupled to a line of power input terminals. The control method includes: providing a voltage divider having a resistor and a controllable resistor connected in series to a connection end, wherein the resistance value of the controllable resistor is controlled by a control signal; An input voltage of the line power input terminal generates a limit signal at the connection end; and, according to the limit signal, controls a current peak flowing through the inductance element.

In an embodiment of the invention, a switched mode power supply is provided that controls an inductive component. The switched mode power supply includes a voltage divider and a peak controller. The voltage divider has a resistor and a controllable resistor connected in series at a connection end. The resistance value of the controllable resistor can be varied by a control signal. The voltage divider generates a limit signal at the connection end according to a line input voltage of the line power input end of the switch mode power supply. The peak controller controls a current peak flowing through the inductive component according to the limit signal.

An embodiment of the present invention provides a control method for a switching power supply having an inductive component coupled to a line of power input terminals. The control method includes providing a limit signal; causing the limit signal to be in phase with a line input voltage of the line power input terminal; providing a feedback mechanism such that a maximum value of the limit signal is substantially a certain value, not exceeding a maximum of the input voltage The value changes; and, according to the limit signal, the current peak flowing through the inductive element is controlled.

In the following embodiments, elements or signals represented by the same or similar symbols indicate the same or similar elements or signals, and the possible variations thereof are those of ordinary skill in the art, and may be based on the teachings of the present specification. Can be inferred. For the sake of streamlining, this manual will not be repeated.

The following embodiments are exemplified by buck converters, but these embodiments do not limit the present invention. Generally speaking, those who have common knowledge of power supply can apply the invention to other kinds of converters after reading this specification, such as boost converter, buck-boost converter, and return. Flyback converter and so on.

Figure 3 illustrates a switched mode power supply 36 implemented in accordance with the present invention. In the third figure, there is a feedback module 60 different from the first one. The feedback module 60 not only detects the voltage across the load 16 from the line voltage terminal IN and the terminal OG, but also detects the current flowing through the load 16 through the terminal OG1 and the terminal OG, thereby controlling the feedback end FB. The feedback signal V _{FB is applied} to achieve the purpose of outputting current and voltage. At the same time, the feedback module 60 can also make the feedback signal V _FB and the line voltage V _IN of the line voltage terminal _IN substantially in phase, and achieve the function of power factor correction.

Figure 4 illustrates the internal circuitry of the feedback module 60. The photo coupler 23 isolates the left and right circuits. The lowest voltage of the left circuit is the voltage of the terminal OG, and the lowest voltage of the right circuit is the voltage of the ground line.

In the left circuit, the constant voltage reference voltage V _REF-CV and the constant current reference voltage V _REF-CC are both constant voltages with respect to the terminal OG. The amplifier 32 and the voltage divider 27 substantially amplify the difference between the voltage across the load 16 (from terminal IN to terminal OG) to a target voltage corresponding to a certain voltage reference voltage V _REF-CV . Resistor 29 can be viewed as an output current detector whose voltage across is proportional to the value of output current I _OUT . The average current detector 25 further includes a low-pass filter formed by a resistor and a capacitor. The amplifier 30 and the average current detector 25 substantially amplify the difference between the average value of the output current I _OUT and a target current corresponding to the constant current reference voltage V _REF-CC . The optical coupler 23 converts the result of the amplifier 30 or the amplifier 32 to the right circuit.

In the right circuit, the output of the optocoupler 23 is low pass filtered by a capacitor and a resistor, and a control signal V _{AV is} generated at the terminal _AV . The voltage divider 37 is coupled between the line voltage terminal IN and the ground GND, and has two resistors and an N-type MOSFET 34. The voltage divider 37 generates a feedback signal V _FB on the feedback terminal FB whose relationship with the line voltage V _IN is substantially as shown in the following formula I:

V _FB =V _IN /K -----------(I).

Where K is the divisor and is controlled by the control signal V _AV . As is known to those of ordinary skill in the art, the N-type MOSFET 34 can be considered a controllable resistor whose channel resistance R _DS is controlled by its gate voltage. Therefore, the control signal V _AV controls the channel resistance R _{DS of} the N-type MOSFET 34, and also controls the divisor K equivalently. The higher the gate voltage, the smaller the channel resistance R _{DS and the} smaller K. Moreover, the voltage divider 37 causes the feedback signal V _FB to be approximately in phase with the line voltage V _IN .

Figure 5 shows some of the signal waveforms in Figure 4; where the line voltage V _IN represents the voltage signal at the line voltage terminal IN; the feedback signal V _FB represents the signal on the feedback terminal FB; the current detection signal V _CS represents the current The voltage signal on the detection terminal CS; the output current I _OUT represents the current flowing between the terminals OG1 to OG, and is also the current flowing through the load 16; the current signal I _CA represents the current drawn by the amplifier 30; the control signal V _AV is The gate voltage signal on the N-type MOSFET 34.

It can be seen from Fig. 5 that the feedback signal V _FB is almost in phase with the line voltage V _IN . In addition, when the maximum value of the line voltage V _IN becomes small, for example, from 220V to 110V, the feedback signal V _FB initially decreases with the line voltage V _IN , but because the output current I _OUT becomes smaller, the control The signal V _AV will gradually decrease, so that the channel resistance R _{DS of the} N-type MOSFET 34 gradually increases, thereby gradually increasing the maximum value of the feedback signal V _FB , and finally returning to the value before the maximum value of the line voltage V _IN changes. It can be inferred from the signal feedback path in Fig. 4 that whether the maximum value of the line voltage V _IN is 220V, 100V or 90V, at the steady-state constant current output, the maximum value of the feedback signal V _FB due to the feedback mechanism It will be a fixed value, and this setting can also make the maximum value of the peak value of the current detection signal V _CS about a constant and will not change with the line voltage V _IN .

The circuit shown in Figure 6 can replace the circuit on the right in Figure 4. In the voltage divider 37a, the luminance of the illuminator in the photocoupler 23 is equivalent to the equivalent resistance of the receiver, so that the divisor K (=V _IN /V _FB ) of the voltage divider 37a is equivalently controlled.

The circuit shown in Figure 7 can replace the circuit on the left of Figure 4. When the output current I _{OUT is} too high, so that the voltage signal V _CO output by the average current detector 25 exceeds 2.5V, the LT431 causes the illuminator in the photocoupler 23 to emit light; when the load 16 is over the voltage (from the terminal IN to When the terminal OG) exceeds the corresponding voltage set by the Zener diode 38, the Zener diode 38 is turned on to cause the illuminator in the photocoupler 23 to emit light. The photocoupler 23 can affect the resistance value of the controllable resistor of the voltage divider 37 or 37a.

In one embodiment, the right circuit of Figure 4 is replaced by Figure 6, and the left circuit of Figure 4 is replaced by Figure 7.

Figure 8 illustrates a switched mode power supply 70 implemented in accordance with the present invention. Different from FIG. 1, the embodiment in FIG. 8 may not operate the power supply 14 and the feedback module 20, and the controller 80 may reach the PFC and the constant current without the feedback terminal FB. Output control.

FIG. 9 illustrates the controller 80 of FIG. 8, which includes a limit signal generator 98 and a controller 18. The controller 18 in Fig. 9 and the controller 18 in Fig. 2 may have identical internal components, and therefore the principle of operation will not be repeated. The difference is that the controller 18 in Fig. 2 receives the feedback signal V _FB and the controller 18 in Fig. 9 receives the limit signal V _DIN on the connection point _DIN . Similar to Fig. 2, the limit signal V _DIN controls the peak value of the current detecting signal V _CS and also controls the peak value of the current flowing through the main winding PRM.

The limit signal generator 98 provides a feedback mechanism that maintains the maximum value of the limit signal V _DIN at approximately a constant value. Taking Fig. 9 as an example, even if the limit signal V _DIN has an M-like wave form with the line voltage V _IN , the limit signal generator 98 can make the maximum value of the limit signal V _DIN at steady state. Approximately equal to the reference voltage V _{REF-OVER at} one of the inputs of comparator 94. The following is exemplified by the reference voltage V _REF-OVER being equal to 2V and the reference voltage V _REF-VLY being equal to 0.1V.

When the limit signal V _DIN exceeds 2V, the SR flip-flop maintains the output Q as a logical one. After a while, the limit signal VDIN will drop as the line voltage V _IN drops. When the limit signal V _{DIN is} lower than 0.1 V, the counter 92 counts down, and the output digital signals D0-D3 become control signals, so that the equivalent resistance of the connection point DIN to the ground GND is lowered. At the same time, the output of the SR flip-flop is reset by the comparator 96 to a logical zero. Therefore, the maximum value of the subsequent limit signal V _DIN will be lower than the maximum value of the previous limit signal V _DIN .

Conversely, when the limit signal V _DIN has never exceeded 2V, the output of the SR flip-flop will remain at a logical zero. Thus, when the limit signal V _{DIN is} lower than 0.1 V, the counter 92 counts up so that the equivalent resistance of the connection point DIN to the ground GND rises. Therefore, the maximum value of the subsequent limit signal V _DIN will become high.

Thus, comparators 94, 96, SR flip-flops, and counter 92, together, can be considered a maximum controller. It provides a feedback mechanism such that the maximum value of the limit signal V _DIN is approximately 2V.

Thus, at steady state, although the maximum value of the limit signal V _DIN is not exactly equal to 2V, it will trip around about 2V and will not change with the maximum value of the line voltage V _IN . Also, since the maximum value of the limit signal V _DIN is about 2V, the maximum value of the peak value of the current detecting signal V _CS is also approximately a fixed value, so that the function of the constant current output can be achieved.

In addition, since the limit signal V _DIN is generated by the divided line voltage V _IN , the limit signal V _DIN can be in phase with the line voltage V _IN , so it can be expected that the average value of the current detection signal V _CS will also be approximately the same as the line voltage. V _{IN is in} phase and can achieve the function of PFC.

Fig. 10 is a controller 18a which can replace the controller 18 of Fig. 2 or Fig. 9 and can be applied to embodiments of the present invention. In contrast to controller 18, controller 18a adds comparator 42 and OR gate 44 to substantially limit the peak value of current sense signal V _CS from exceeding the limit reference voltage V _REF-LIM . If it is in Fig. 9, but the controller 18 therein is replaced by the controller 18a of Fig. 10, such an embodiment is explained. If the limit signal generator 98 causes the maximum value of the limit signal V _DIN to be approximately 2 V, the divided voltage signal V _FB-DIV has a maximum value of about 250 mV, and the value of the limit reference voltage V _REF-LIM is assumed to be 200 mV. Then, when the divided voltage signal V _{FB-DIV is} less than 200 mV, the peak value of the current detecting signal V _CS changes by changing the divided voltage signal V _FB - _DIV . When the voltage dividing signal V _{FB-DIV is} greater than 200 mV, the peak value of the current detecting signal V _CS is only about 200 mV at most. Although such an example PF may be reduced, it has the advantage of preventing the load 16 from being subjected to excessive current and burning. In another embodiment, the limiting reference voltage V _REF-LIM may be higher than the maximum value of the divided voltage signal V _FB-DIV .

The above are only the preferred embodiments of the present invention, and all changes and modifications made to the scope of the present invention should be within the scope of the present invention.

8. . . Switching power supply

10. . . Conversion module

11. . . Dipole

12. . . Bridge rectifier

14. . . Operating power supply

15. . . Power switch

16. . . load

18. . . Controller

20. . . Feedback module

twenty three. . . Optocoupler

twenty four. . . Current detecting resistor

25. . . Average current detector

27. . . Voltage divider

29. . . resistance

30. . . Amplifier

32. . . Amplifier

34. . . N-type MOSFET

36. . . Switching power supply

37, 37a. . . Voltage divider

38. . . Kina diode

42. . . Comparators

44. . . Gate

60. . . Feedback module

70. . . Switching power supply

80. . . Controller

82. . . Logical control

87. . . Clock generator

88. . . Comparators

92. . . counter

94. . . Comparators

98. . . Limit signal generator

AC. . . Communication end

AUX. . . Auxiliary winding

AV. . . end

CS. . . Current detection terminal

D0-D3. . . Digital signal

DIN. . . Junction

FB. . . Feedback end

GATE. . . Gate end

GND. . . Ground terminal

I _CA . . . Current signal

IN. . . Line voltage terminal

I _OUT . . . Output current

OG. . . end

OG1. . . end

PRM. . . Main winding

V _AV . . . control signal

V _CC . . . Operating voltage

VCC. . . Operating power terminal

V _CO . . . Voltage signal

V _CS . . . Current detection signal

V _DIN . . . Limit signal

V _FB . . . Feedback signal

V _FB-DIV . . . Partial voltage signal

V _GATE . . . Gate signal

V _IN . . . Line voltage

V _REF-CC . . . Constant current reference voltage

V _REF-CV . . . Constant voltage reference voltage

V _REF-LIM . . . Limit reference voltage

V _REF-OVER . . . Reference voltage

V _REF-VLY . . . Reference voltage

Figure 1 is a diagram of a conventional switched mode power supply architecture.

Figure 2 illustrates a conventional controller.

Figure 3 illustrates a switched mode power supply implemented in accordance with the present invention.

Figure 4 illustrates an internal circuit of a feedback module.

Figure 5 shows some of the signal waveforms in Figure 4.

Figure 6 shows the circuit that can replace the right circuit of Figure 4.

Figure 7 shows the circuit that can replace the left circuit of Figure 4.

Figure 8 illustrates a switching power supply in accordance with the practice of the present invention.

Fig. 9 illustrates the controller in Fig. 8.

Fig. 10 is a controller which can replace the controller of Fig. 2 or Fig. 9.

10. . . Conversion module

12. . . Bridge rectifier

14. . . Operating power supply

16. . . load

18. . . Controller

36. . . Switching power supply

60. . . Feedback module

AC. . . Communication end

CS. . . Current detection terminal

FB. . . Feedback end

GATE. . . Gate end

IN. . . Line voltage terminal

OG. . . end

OG1. . . end

VCC. . . Operating power terminal

Claims (9)

A control method for a switching power supply having an inductive component coupled to a line of power input, the control method comprising: providing a voltage divider, having a resistor and a controllable a resistor connected in series to a connection end, wherein the resistance value of the controllable resistor is controlled by a control signal; generating a limit signal at the connection end according to the input voltage of the line power input; and according to the limit signal Controlling a current peak flowing through the inductive component; wherein the controllable resistor includes a metal oxide half field effect transistor (MOS FET), the control signal is sent to the gold oxide half field effect transistor, and the gold oxide half field is linearly changed The channel equivalent resistance of the effect transistor. The control method of claim 1, wherein the switching power supply system drives a light emitting diode string, the method further comprising: flowing the light emitting diode according to the voltage of the light emitting diode string or according to the light emitting diode The current of the body changes the control signal. The control method according to claim 2, wherein the control signal is changed by an optical coupler according to the voltage of the LED string or according to the current flowing through the LED. The control method of claim 1, comprising: changing the control signal according to a maximum value of the limit signal such that the maximum value is approximately a fixed value. A switching power supply device for controlling an inductive component comprises: a voltage divider having a resistor and a controllable resistor connected in series to a connection end, wherein the resistance value of the controllable resistor is controlled by a control signal Alternatively, the voltage divider generates a limit signal at the connection end according to a line input voltage of the line power input end of the switch mode power supply; and a peak controller that controls the flow of the inductance element according to the limit signal a current peak; wherein the controllable resistor comprises a metal oxide half field effect transistor (MOS FET), the control signal is sent to the gold oxide half field effect transistor, and the channel equivalent resistance of the gold oxide half field effect transistor is linearly changed. . The switch power supply device of claim 5, further comprising: an output voltage detector for detecting an output load across the voltage; and an output current detector for detecting the output through the output a current of the load; and at least one amplifier that controls the control signal based on the output voltage detector or the output current detector. The switch mode power supply as claimed in claim 5, further comprising an up/down counter, wherein the plurality of digital signals outputted are used as the control signal. The switched mode power supply of claim 5 includes a maximum value controller that provides a feedback mechanism such that the maximum value of the limit signal is approximately a fixed value. A control method is applicable to a switching power supply device having an inductance component coupled to a line power input end, the control method comprising: providing a limit signal; and causing the limit signal and the line power input line The input voltage is in phase; a feedback mechanism is provided such that the maximum value of the limit signal is substantially constant, does not change with the maximum value of the input voltage; and the current peak flowing through the inductive element is controlled according to the limit signal.