CN116937938A - Control method for power factor correction and power supply controller - Google Patents

Abstract

The invention provides a control method for power factor correction and a power supply controller. The control method is suitable for a power factor correction power converter, and comprises a power switch and an inductor. The control method comprises the following steps: providing a compensation signal according to an output voltage; providing a correction signal according to an on time of the power switch and the compensation signal, so that the on time, the compensation signal and the correction signal accord with a preset relation; and controlling the opening time according to the correction signal.

Description

Control method for power factor correction and power supply controller

Technical Field

The present invention relates generally to a control method and a power controller for a power factor correction power converter, and more particularly, to a control method and a power controller capable of providing a good power factor when the power factor correction power converter is operated in a discontinuous conduction mode.

Background

A power factor (power factor) represents whether or not the supplied power can be effectively utilized. The maximum value of the power factor is 1, which is also the ideal value of the power factor. When the power factor of an electronic device is not equal to 1, it means that a power supply unit (such as an electric power company) needs to have a power supply capacity higher than the power consumption of the electronic device, so that the electronic device can operate normally. In order for the power supply capability of a power system to be effectively utilized, industry regulations dictate that many electronic devices, such as lighting electronics or power supplies above 75W, be capable of meeting power levels up to 0.9 or more.

The active power factor correction (power factor correction, PFC) refers to the use of active devices, including control circuitry and electronic circuits such as power switches, to adjust the input current waveform to be as similar as possible to the input voltage waveform, so that the power factor correction can be approximately 100%. Active power factor correction is typically implemented using a switching power supply. For example, a constant ON-time boost circuit (boost) or flyback converter can achieve a relatively high power factor. However, in light load, the constant on-time often has a problem of too high switching frequency, which results in too high switching loss and poor conversion efficiency.

Disclosure of Invention

The embodiment of the invention provides a control method which is suitable for a power factor correction power converter and is provided with a power switch and an inductor. The control method comprises the following steps: providing a compensation signal according to an output voltage; providing a correction signal according to an on time of the power switch and the compensation signal, so that the on time, the compensation signal and the correction signal accord with a preset relation; and controlling the opening time according to the correction signal.

The embodiment of the invention provides a power supply controller which is suitable for a power factor correction power supply converter. The power factor correction power converter comprises a power switch and an inductor, and is used for providing an output power supply with an output voltage. The power supply controller comprises a compensation circuit, a correction circuit and a starting time controller. The compensation circuit compares the output voltage with a target voltage to provide a compensation signal. The correction circuit generates a correction signal according to an on time of the power switch and the compensation signal, so that the on time, the compensation signal and the correction signal accord with a preset relation. The on-time controller controls the on-time according to the correction signal.

Drawings

FIG. 1 is a schematic diagram of a power factor correction power converter according to the present invention.

Fig. 2 shows some of the signal waveforms of fig. 1.

Fig. 3 shows the power supply controller of fig. 1.

Fig. 4 shows the correction circuit of fig. 3.

[ symbolic description ]

100. Power factor correction power converter

102. Bridge rectifier

104. Power switch

106. Current detection resistor

108. Power supply controller

162. Compensation circuit

164. Correction circuit

166. Closing time controller

168. Multiplier unit

170 SR trigger

172. Opening time controller

182. 184 voltage-to-current converter

186. Switch

188. Capacitance device

190. Update circuit

192. Logic circuit

CCOM compensation capacitor

CO, CVCC output capacitor

D01, D02 rectifier

FB feedback end

GND grounding wire

I _DR Electric current

I _LIN Inductor current

I _LIN-AVG Average current value

I _PEAK Peak value

I _SR Electric current

LA auxiliary winding

LIN line power line

LP main winding

PLAT platform

RA, RB, RC, RD, RE resistor

S _DIS Discharge signal

S _DRV Drive signal

TCYC switching period

TDIS discharge time

TOFF off time

TON on time

V _AC AC mains supply

V _AUX Terminal voltage

V _CAP Capacitor voltage

V _COMP Compensation signal

V _COMP-A Correction signal

V _CS Current detection signal

V _FB Feedback voltage

V _LIMIT Product signal

V _LIN Line voltage signal

VL ₁ 、VL ₂ Signal trough

V _MULT Input signal

V _OUT Output voltage

VOUT output power supply

V _PEAK Peak value

ZCD zero current detection end

Detailed Description

In this description, there are some common symbols that represent elements of the same or similar structure, function, and principle, and will be apparent to those skilled in the art in light of the teachings of this description. Elements of the same symbols will not be repeated for brevity of description.

Although the present invention is exemplified by a boost circuit, the present invention is not limited thereto. The invention is also applicable to other power converters, such as flyback converters or buck-boost power converters.

In one embodiment of the present invention, a power factor correction power converter has a power switch and an inductor connected in series, and a power controller for controlling the power switch. The power factor correction power converter converts an input line power to generate an output power having an output voltage. The power supply controller is provided with a compensation circuit, a correction circuit and an on-time controller. The compensation circuit compares the output voltage with a target voltage to provide a compensation signal. The correction circuit generates a correction signal according to an on time of the power switch, a discharge time of the power switch and the compensation signal. The on-time controller controls the on-time according to the correction signal. The correction circuit enables the on time, the discharge time, the compensation signal and the correction signal to accord with a preset relation.

In one embodiment, the predetermined relationship may be such that when the power factor correction power converter operates in the discontinuous conduction mode, an average current of the inductor is approximately proportional to a line voltage signal of the input line power source even if an off time of the power switch is much longer than the discharge time, and has a relatively good power factor.

Fig. 1 is a schematic diagram of a power factor correction power converter 100 according to the present invention. The power source correction power converter 100 is a boost circuit, and includes a bridge rectifier 102, a transformer formed by a main winding LP and an auxiliary winding LA, a power switch 104, a current detection resistor 106, a power source controller 108, a resistor RA, RB, RC, RD, RE, output capacitors CO, CVCC, a compensation capacitor CCOM, and rectifiers D01, D02, which are connected to each other in the same manner as shown in fig. 1. The power factor correction power converter 100 provides an output power VOUT having an output voltage V _OUT 。

Bridge rectifier 102 full waveRectifying AC mains V _AC A line power supply line LIN and a ground line GND are provided. The voltage of the ground GND is considered to be 0V, while the line power line LIN has a line voltage signal V _LIN 。

The main winding LP, the power switch 104, and the current detection resistor 106 are connected in series between the line power supply line LIN and the ground line GND. The power controller 108 controls the power switch 104 to control the inductor current I flowing through the main winding LP _LIN . The current detection resistor 106 provides a current detection signal V _CS To the power supply controller 108. When the power switch 104 is turned on to present a short circuit, the current detection signal V _CS Can represent inductor current I _LIN 。

Fig. 2 shows some of the signal waveforms of fig. 1, from top to bottom, respectively with the driving signals S of the power switch 104 controlled by the power controller 108 _DRV Current detection signal V _CS Inductor current I _LIN Terminal voltage V on auxiliary winding LA _AUX 。

The power controller 108 drives the signal S _DRV The control power switch 104 is periodically turned on and off. When the power switch 104 is a short circuit, it is on time TON; when the power switch 104 is open, it is off for time TOFF. A switching period TCYC is composed of an on time TON and an off time TOFF.

During the on time TON, the main winding LP stores energy and the inductor current I _LIN And a current detection signal V _CS Are increasing over time. During the off time TOFF, the current detection signal V is generated because the power switch 104 is open _CS Maintained at about 0V. During the off time TOFF, the inductor current I _LIN Over time, until the main winding LP is fully energized, inductor current I _LIN About 0A. The time for which the main winding LP releases energy, i.e. from the end of the on-time TON, to the inductor current I _LN Time of 0A is referred to as discharge time TDIS of main winding LP.

During the on time TON, the terminal voltage V _AUX About a fixed negative value, reflecting the line voltage signal V _LIN . At discharge time TDIS, terminal voltage V _AUX About a fixed wayAs shown in the platform PLAT of fig. 2, reflects the output voltage V _OUT And line voltage signal V _LIN Difference between them. After the discharge time TDIS, the terminal voltage V _AUX Oscillation starts until the next on time TON, as shown in fig. 2. Terminal voltage V _AUX Oscillating to produce signal trough VL ₁ 、VL ₂ As illustrated in fig. 2.

FIG. 3 shows the power controller 108 of FIG. 1, including a compensation circuit 162, a correction circuit 164, a multiplier 168, an off-time controller 166, an on-time controller 172, and an SR flip-flop 170.

Compensation circuit 162 compares output voltage V _OUT And a preset target voltage to provide the compensation signal V _COMP . For example, the compensation circuit 162 has a transconductor (transconductor) for comparing the feedback voltage V at the feedback terminal FB _FB And 2.5V to determine whether to charge or discharge the compensation capacitor CCOM, so as to generate the compensation signal V _COMP . For example, when a load supplied by the output power source VOUT is heavy load, the compensation signal V _COMP Will be higher than if the load is light. Because of the feedback voltage V _FB Based on the output voltage V _OUT Generated by dividing the voltage through resistors RA and RB, the compensation circuit 162 equally compares the output voltage V _OUT And a predetermined target voltage.

The correction circuit 164 receives the driving signal S _DRV Discharge signal S _DIS And compensation signal V _COMP To generate a correction signal V _COMP-A . The correction circuit 164 may be derived from the drive signal S _DRV Knowing the on time TON from the discharge signal S _DIS The discharge time TDIS is known. Correction circuit 164 causes compensation signal V _COMP Correction signal V _COMP-A The on-time TON, and the discharge time TDIS conform to a predetermined relationship. In one embodiment, this relationship is the following equation (I).

V _COMP-A ＝KA*V _COMP *T _CYC /(T _ON +T _DIS )…(I)

Wherein KA is a constant, T _ON 、T _DIS And T is _CYC Respectively is the on time TON and the discharge time T _DIS And the length of the switching period TCYC. As will be further described, equation (I) may enable the power factor correction power converter 100 to operate in a discontinuous conduction mode with a relatively good power factor.

Multiplier 168 corrects signal V _COMP-A And input signal V _MULT Multiplication to generate a product signal V _LIMIT . Input signal V _MULT Is based on the line voltage signal V _LIN Generated by the voltage division of resistors RC and RD, the multiplier 168 equalizes the product line voltage signal V _LIN And correction signal V _COMP-A To generate the product signal V _LIMIT . For example, the following formula (II) shows the product signal V _LIMIT Correction signal V _COMP-A And line voltage signal V _LIN Is a relationship of (3).

V _LIMIT ＝Km*V _MULT *V _COMP-A

＝KM*V _LIN *V _COMP-A …(II).

Wherein Km and Km are two fixed constants. Correction signal V in equation (II) _COMP-A Instead of the formula (I), the following formula (III) can be obtained

V _LIMIT ＝KO*V _LIN *V _COMP *T _CYC /(T _ON +T _DIS )…(III)。

KO is another constant related to the constants KM and KA.

The on-time controller 172 determines the length T of the constant on-time TON _ON . For example, the on-time controller 172 may be a comparator for comparing the product signal V _LIMIT And a current detection signal V _CS . In the current detection signal V _CS High overproduct signal V _LIMIT At this time, the driving signal S is caused to pass through the SR flip-flop 170 _DRV The power switch 104 is turned off for a logical "0" and the on-time TON is ended. The on-time controller 172 causes the current detection signal V to be _CS Peak value V of (2) _PEAK Approximately equal to the product signal V _LIMIT . In FIG. 2, peak value V _PEAK About equal to I _PEAK *R ₁₀₆ WhereinI _PEAK For inductor current I _LN Peak value of R ₁₀₆ Is the resistance value of the current detection resistor 106.

The off-time controller 166 determines the length T of the off-time TOFF _OFF . For example, the off-time controller 166 detects the terminal voltage V on the auxiliary winding LA through the zero current detection terminal ZCD _AUX . Referring to fig. 2 and 3, the off-time controller 166 can detect the terminal voltage V _AUX Whether to fall from the platform PLAT to determine whether the discharge time TDIS is over, generating a discharge signal S _DIS . The off-time controller 166 may detect the terminal voltage V _AUX Whether to drop and cross 0V to judge whether to use the terminal voltage V _AUX A signal trough of (a) is about to occur, thereby ending the off-time TOFF. For example, the off-time controller 166 is based on the compensation signal V _COMP Providing a masking time TBLNK, and after the masking time TBLNK, approximately the voltage V _AUX When the first signal trough of (1) occurs, the driving signal S is caused to pass through the SR flip-flop 170 _DRV To a logical "1", the power switch 104 is turned on, ending the off time TOFF. Compensation signal V _COMP The lower the load, the lighter the masking time TBLNK is. Therefore, the off-time controller 166 may cause the power switch 104 to turn on at voltage V _AUX Providing a valley switching when a first signal valley of the (b) signal occurs. This mode of operation is referred to as critical mode (BM) if the power switch 104 is turned on approximately when the first signal trough occurs after the discharge time TDIS, a special case of discontinuous mode (Discontinuous mode, DCM). The off-time controller 166 is equal to the compensation signal V _COMP The length of the switching period TCYC is controlled and the switching frequency is determined.

FIG. 4 shows a correction circuit 164 including voltage-to-current converters 182, 184, a switch 186, a capacitor 188, and an update circuit 190, which can be implemented in equation (I), the compensation signal V _COMP Correction signal V _COMP-A The on-time TON, and the discharge time TDIS. The voltage-to-current converter 182 is based on the compensation signal V _COMP Generating a current I _SR . Current I _SR About equal to K1V _COMP And K1 is a constant. Current I _SR The capacitor 188 is fixedly charged so that the capacitor voltage V _CAP And (3) increasing. Similarly, the voltage-to-current converter 184 is based on the correction signal V _COMP-A Generating a current I _DR About equal to K2V _COMP-A And K2 is a constant. The switch 186 is controlled by the driving signal S through the logic circuit 192 _DRV And discharge signal S _DIS Only the on-time TON and the discharge time TDIS are on. Therefore, the current I _DR Only at the on-time TON and the discharge time TDIS, the capacitor 188 is discharged to enable the capacitor voltage V _CAP Descending. The refresh circuit 190 is based on the capacitor voltage V _CAP To adjust the correction signal V _COMP-A . For example, the refresh circuit 190 is a switched capacitor circuit, which is responsive to the capacitor voltage V _CAP Sampling, and adjusting the correction signal V by the sampling result _COMP-A . At the beginning and end of each switching period TCYC, the capacitance voltage V is equal to the capacitance voltage V at the time when the correction circuit 164 reaches the balance _CAP Having about the same value. In other words, for the charge amount of the capacitor 188 to be equal to the discharge amount in the switching period TCYC, the following formula (IV) can be obtained,

I _SR *T _CYC ＝I _DR *(T _ON +T _DIS )…(IV)。

the current I in the formula (VI) _SR And I _DR To compensate for signal V _COMP And correction signal V _COMP-A Instead, and after rearrangement, the following formula (V) can be obtained,

V _COMP-A ＝(K1/K2)*V _COMP *T _CYC /(T _ON +T _DIS )…(V)。

the constant KA in equation (I) may be equal to K1/K2 in equation (V). Thus, the correction circuit 164 of FIG. 4 can implement the compensation signal V in equation (I) _COMP Correction signal V _COMP-A The on-time TON, and the discharge time TDIS.

The power factor correction power converter 100 may have a very good power factor when operating in DCM, such that the inductor current I _LIN Average current value I of (1) _LIN-AVG About and line voltage signal V _LIN Is a proportional relationship. Referring to FIG. 2, the average current value I _LIN-AVG Heel inductor current I _LIN Peak value I of (2) _PEAK The following formula (VI) can be produced in relation to each other.

I _LIN-AVG ＝0.5*I _PEAK *(T _ON +T _DIS )/T _CYC

＝0.5*V _PEAK /R ₁₀₆ *(T _ON +T _DIS )/T _CYC …(VI)

As previously described, peak V _PEAK Approximately equal to the product signal V _LIMIT And the product signal V _LIMIT Can be replaced by formula (III).

I _LIN-AVG ＝0.5*(KO*V _LIN *V _COMP *T _CYC /(T _ON +T _DIS ))

/R ₁₀₆ *(T _ON +T _DIS )/T _CYC

＝0.5*KO*V _LIN *V _COMP /R ₁₀₆

＝KT*V _COMP *V _LIN …(VII)

Wherein KT is a correlation constant KO and a resistance value R ₁₀₆ Is a constant of (a). As can be seen from equation (VII), the inductor current I _LIN Average current value I of (1) _LIN-AVG About and line voltage signal V _LIN Is a proportional relationship which is defined by the compensation signal V _COMP Controlled by the controller. Thus, power factor correction power converter 100 may have a very good power factor when operating in DCM.

When the load is light or no load, the masking time TBLNK may enable the power factor correction power converter 100 to operate in DCM, which has a very low operating frequency, reduces switching losses, and increases conversion efficiency. Further, even if the discharge time TDIS is shorter than the off time TOFF, the power factor correction power converter 100 can be very good.

The foregoing description is only of the preferred embodiments of the present invention, and all equivalent changes and modifications made in the claims should be construed to fall within the scope of the present invention.

Claims (10)

1. A control method is suitable for a power factor correction power converter, which is provided with a power switch and an inductor, and comprises the following steps:

providing a compensation signal according to the output voltage;

providing a correction signal according to the on time of the power switch and the compensation signal so that the on time, the compensation signal and the correction signal accord with a preset relation; and

and controlling the opening time according to the correction signal.

2. The control method of claim 1, comprising:

providing the correction signal according to the on time of the power switch, the discharging time of the inductor and the compensation signal;

wherein the preset relationship correlates the on time, the discharge time, the compensation signal, and the correction signal.

3. The control method of claim 1, comprising:

according to the compensation signal, the closing time of the power switch is controlled so that the power factor correction power converter operates in a discontinuous conduction mode (discontinuous conduction mode).

4. The control method of claim 1, comprising:

providing a first current according to the compensation signal, so that the capacitance voltage of the capacitor changes towards a first direction;

providing a second current according to the correction signal and the on time to enable the capacitor voltage to change towards a second direction, wherein the second direction is opposite to the first direction; and

and adjusting the correction signal according to the capacitor voltage.

5. The control method of claim 1, comprising:

multiplying the modified signal with the line voltage signal to produce a product signal; and

controlling the on time according to the product signal and the current detection signal;

wherein the current detection signal represents an inductor current flowing through the inductor.

6. A power supply controller for a power factor correction power converter, comprising a power switch and an inductor for providing an output power, having an output voltage, the power supply controller comprising:

a compensation circuit for comparing the output voltage with a target voltage to provide a compensation signal;

the correction circuit generates a correction signal according to the on time of the power switch and the compensation signal, so that the on time, the compensation signal and the correction signal accord with a preset relation; and

and the starting time controller is used for controlling the starting time according to the correction signal.

7. The power supply controller of claim 6, wherein the correction circuit provides the correction signal according to the on-time, the compensation signal and a discharge time of the inductor, and the predetermined relationship is related to the on-time, the compensation signal, the discharge time, the on-time and a switching period of the power switch.

8. The power supply controller of claim 6, wherein the correction circuit comprises:

a capacitor;

a first voltage-current converter for converting the compensation signal into a first current so as to change the capacitance voltage of the capacitor towards a first direction;

a second voltage-to-current converter for converting the correction signal into a second current to change the capacitor voltage in a second direction opposite to the first direction; and

and the updating circuit adjusts the correction signal according to the capacitor voltage.

9. The power controller of claim 6, wherein the on-time controller comprises:

a multiplier for generating a product signal according to the correction signal and the line voltage signal; and

a comparator for comparing the product signal with a current detection signal to control the on time;

wherein the current detection signal represents an inductor current flowing through the inductor.

10. The power supply controller of claim 6, further comprising:

and the closing time controller is used for enabling the closing time of the power switch to be not shorter than the shielding time according to the compensation signal, and the shielding time is generated according to the compensation signal.