CN112234826B - Primary controller applied to primary side of power converter and operation method thereof - Google Patents

Primary controller applied to primary side of power converter and operation method thereof Download PDF

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CN112234826B
CN112234826B CN201910637443.4A CN201910637443A CN112234826B CN 112234826 B CN112234826 B CN 112234826B CN 201910637443 A CN201910637443 A CN 201910637443A CN 112234826 B CN112234826 B CN 112234826B
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voltage
current
compensation
power converter
secondary side
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CN112234826A (en
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陈启宾
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Leadtrend Technology Corp
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Leadtrend Technology Corp
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    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/3353—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having at least two simultaneously operating switches on the input side, e.g. "double forward" or "double (switched) flyback" converter
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M3/00—Conversion of dc power input into dc power output
    • H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
    • H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
    • H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
    • H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
    • H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
    • H02M3/33507—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters
    • H02M3/33523—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only with automatic control of the output voltage or current, e.g. flyback converters with galvanic isolation between input and output of both the power stage and the feedback loop
    • H—ELECTRICITY
    • H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
    • H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
    • H02M7/00—Conversion of ac power input into dc power output; Conversion of dc power input into ac power output
    • H02M7/02—Conversion of ac power input into dc power output without possibility of reversal
    • H02M7/04—Conversion of ac power input into dc power output without possibility of reversal by static converters
    • H02M7/12—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode
    • H02M7/21—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal
    • H02M7/217—Conversion of ac power input into dc power output without possibility of reversal by static converters using discharge tubes with control electrode or semiconductor devices with control electrode using devices of a triode or transistor type requiring continuous application of a control signal using semiconductor devices only

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  • Engineering & Computer Science (AREA)
  • Power Engineering (AREA)
  • Dc-Dc Converters (AREA)

Abstract

The invention discloses a primary controller applied to a primary side of a power converter and an operation method thereof. The primary controller comprises a current compensation circuit and a compensation voltage generation circuit. The current compensation circuit is used for generating a compensation current to the sensing resistor of the primary side according to a direct current voltage and an auxiliary voltage, wherein the auxiliary voltage is related to the output voltage of the secondary side of the power converter, and the compensation current changes the peak voltage of the primary side. The compensation voltage generating circuit is used for generating a compensation voltage according to a reference current, the discharge time of the secondary side and a peak current, wherein the reference current can change along with the output voltage. The compensation current and the reference current are used for keeping the output current of the secondary side of the power converter unchanged along with the output voltage. Therefore, compared with the prior art, the invention can effectively eliminate the influence of the output voltage on the output current.

Description

Primary controller applied to primary side of power converter and operation method thereof
Technical Field
The present invention relates to a primary controller applied to a primary side of a power converter and an operating method thereof, and more particularly, to a primary controller and an operating method thereof, which can prevent an output current of a secondary side of a power converter from varying with an output voltage of the secondary side of the power converter.
Background
In the prior art, a designer of a constant current (constant current) power converter may control the power converter to be turned on and off by using a primary controller applied to a primary side of the power converter. The primary controller determines a compensation voltage on a compensation pin of the power converter by using a peak current related to a peak voltage of a primary side of the power converter, a discharge time of a secondary side of the power converter and a reference current, and then controls a power switch of the power converter to be turned on and off according to the compensation voltage, wherein the compensation voltage is related to an output voltage of the secondary side of the power converter, and the primary controller makes an output current of the secondary side of the power converter be a constant current by using the negative feedback mechanism. In addition, it should be understood by those skilled in the art that the output current of the secondary side of the power converter is related to the turn ratio of the primary side inductance and the secondary side inductance of the power converter, the peak current, the sensing resistance of the primary side of the power converter, the discharge time of the secondary side, and the switching period of the power switch. Ideally, the output current of the secondary side of the power converter does not change with the output voltage of the secondary side of the power converter, but because the peak current, the discharge time of the secondary side, and the switching period of the power switch change with the output voltage of the secondary side of the power converter, the output current also changes with the output voltage of the secondary side of the power converter. Therefore, how to make the output current not vary with the output voltage on the secondary side of the power converter becomes an important issue for designers of the power converter.
Disclosure of Invention
An embodiment of the invention discloses a primary controller applied to a primary side of a power converter. The primary controller comprises a current compensation circuit and a compensation voltage generation circuit. The current compensation circuit is used for generating a compensation current to the sensing resistor of the primary side according to a direct current voltage and an auxiliary voltage, wherein the auxiliary voltage is related to the output voltage of the secondary side of the power converter, and the compensation current changes the peak voltage of the primary side. The compensation voltage generating circuit is coupled to the current compensation circuit and used for generating a compensation voltage according to a reference current, the discharge time of the secondary side and a peak current, wherein the reference current changes along with the output voltage of the secondary side of the power converter. The compensation current and the reference current are used for keeping the output current of the secondary side of the power converter unchanged along with the output voltage of the secondary side of the power converter.
Another embodiment of the present invention discloses an operating method of a primary controller applied to a primary side of a power converter, wherein the primary controller includes a current compensation circuit, a compensation voltage generation circuit, and a gate control signal generation circuit. The operation method comprises the steps that the current compensation circuit generates a compensation current to a sensing resistor of the primary side according to a direct current voltage and an auxiliary voltage, wherein the auxiliary voltage is related to the output voltage of the secondary side of the power converter, and the compensation current changes the peak voltage of the primary side; the compensation voltage generating circuit generates a compensation voltage according to a reference current, the discharge time of the secondary side and a peak current, wherein the reference current can change along with the output voltage of the secondary side of the power converter; and the grid control signal generating circuit generates a grid control signal to a power switch on the primary side of the power converter according to the compensation voltage, wherein the grid control signal is used for controlling the power switch to be switched on and off. The compensation current and the reference current are used for keeping the output current of the secondary side of the power converter unchanged along with the output voltage of the secondary side of the power converter.
The invention discloses a primary controller applied to a primary side of a power converter and an operation method thereof. The primary controller and the operation method are used for enabling the output current on the secondary side of the power converter not to change along with the output voltage by utilizing the compensation current which is generated by the current compensation circuit of the primary controller and varies in the reverse direction with the output voltage on the secondary side of the power converter and the reference current which is generated by the reference current source of the primary controller and varies in the forward direction with the output voltage. Therefore, compared with the prior art, the compensation current and the reference current are related to the output voltage, so the invention can effectively eliminate the influence of the output voltage on the output current.
Drawings
Fig. 1 is a schematic diagram of a primary controller applied to a primary side of a power converter according to a first embodiment of the present invention.
Fig. 2 is a schematic diagram illustrating a compensation voltage generation circuit within the primary controller for generating the compensation voltage.
Fig. 3 is a diagram illustrating an actual value of the sensing voltage and an ideal value of the sensing voltage.
Fig. 4 is a schematic diagram illustrating a relationship between an output current on the secondary side of the power converter and an input voltage on the primary side of the power converter.
Fig. 5 is a schematic diagram illustrating a current compensation circuit.
Fig. 6 is a schematic diagram illustrating a relationship between the compensation current and the auxiliary voltage.
Fig. 7 is a diagram illustrating the relationship between output current, output voltage and input voltage.
Fig. 8 is a schematic diagram illustrating a reference current source.
Fig. 9 is a diagram illustrating the relationship between the output current, the output voltage, and the input voltage.
Fig. 10 is a flowchart of an operation method of a primary controller applied to a primary side of a power converter according to a second embodiment of the present invention.
Wherein the reference numerals are as follows:
100 power converter
101 voltage dividing circuit
102 power switch
103 auxiliary winding
104 sense resistor
106 primary side winding
108 secondary side winding
110 diode
200 primary controller
202 current compensation circuit
204 compensation voltage generating circuit
2042 reference current source
2044 switch
2046 Peak Current Source
2022 digital-to-analog converter
20242. 20422, 20424 and 20436 operational amplifier
20244. 20426, 20428, 20434, 20438 NMOS metal oxide semiconductor transistors
20246. 20440 resistor
20248. 20250, 20252, 20430 pmos transistors
20442 capacitance
20444 voltage-current converter
CCOMP compensation capacitor
COMP, GATE, ZCD, CS, HV, VCC, pin
GND
DS1, DS2 digital signals
GCS Gate control Signal
I1 first Current
I2 second Current
IPRI, IS current
IOUT output current
Peak current of IPK
IREF reference current
ICC compensation current
PRI Primary side
SEC Secondary side
TDIS discharge time
TON on time
VDC direct voltage
VCOMP compensation voltage
VS sense voltage
Peak voltage of VPK
Ideal peak voltage of VIPK
VAC input voltage
Auxiliary voltage of VZCD
Constant voltage of VZCDM
VHV, VAUX, VVPO voltages
VOUT output voltage
VREF reference voltage
1000 step 1006
Detailed Description
Referring to fig. 1 and 2, fig. 1 is a schematic diagram of a primary controller 200 applied to a primary side PRI of a power converter 100 according to a first embodiment of the present invention, and fig. 2 is a schematic diagram illustrating a compensation voltage generating circuit 204 for generating a compensation voltage VCOMP in the primary controller 200, wherein the primary controller 200 includes a current compensation circuit 202 and a compensation voltage generating circuit 204, the power converter 100 is a flyback power converter (flyback power converter), and the current compensation circuit 202 is coupled to an auxiliary winding 103 of the primary side PRI of the power converter 100 through a voltage dividing circuit 101. As shown in fig. 2, the compensation voltage generating circuit 204 determines the compensation voltage VCOMP at the pin COMP of the primary controller 200 by using a peak current IPK, the discharge time TDIS of the secondary side SEC of the power converter 100, and a reference current IREF. In addition, as shown in fig. 2, the compensation voltage generating circuit 204 includes a reference current source 2042, a switch 2044, and a peak current source 2046, wherein the reference current source 2042 is configured to provide a reference current IREF, the switch 2044 is turned on according to the discharge time TDIS, the peak current source 2046 is configured to provide a peak current IPK, and the coupling relationship among the reference current source 2042, the switch 2044, and the peak current source 2046 can refer to fig. 2, which is not repeated herein. After the compensation voltage VCOMP is generated, a GATE control signal generating circuit (not shown in fig. 1 and 2) in the power converter 100 generates a GATE control signal GCS according to the compensation voltage VCOMP to control the power switch 102 of the power converter 100 to turn on or off, wherein the GATE control signal GCS is transmitted to the power switch 102 through the pin GATE of the primary controller 200, and the peak current IPK is determined by equation (1):
Figure GDA0003218703310000061
as shown in equation (1), VPK is the peak voltage of the primary side PRI of the power converter 100, RS is the resistance of the sensing resistor 104 of the primary side PRI of the power converter 100, and K is a constant.
In addition, as shown in fig. 2, when the compensation voltage VCOMP is stable, equation (2) can be determined according to the charge conservation on the compensation capacitor CCOMP coupled to the pin COMP:
IREF×TS＝IPK×TDIS (2)
as shown in equation (2), TS is the switching period of the power switch 102. In addition, it should be understood by those skilled in the art that the output current IOUT of the secondary side SEC of the power converter 100 can be determined by equation (3):
Figure GDA0003218703310000062
as shown in equation (3), NP is the number of turns of the primary winding 106 of the primary side PRI of the power converter 100, and NS is the number of turns of the secondary winding 108 of the secondary side SEC of the power converter 100. Since the sensing voltage VS across the sensing resistor 104 is determined by the sensing resistor 104, the on-time TON of the power switch 102 and the current IPRI flowing through the primary side PRI of the power converter 100, the peak voltage VPK of the sensing voltage VS is ideally determined by the sensing voltage VS and the on-time TON of the power switch 102. However, because of the non-ideality of the sensing voltage VS (wherein the actual value of the sensing voltage VS may refer to the solid line shown in fig. 3 and the ideal value of the sensing voltage VS may refer to the dashed line shown in fig. 3), the actual peak voltage VPK is not equal to the ideal peak voltage VIPK, that is, the peak voltage VPK has an error. In addition, in practice, the discharge time TDIS of the secondary side SEC of the power converter 100 is not ideal, that is, the start point and the end point of the discharge time TDIS cannot be accurately determined, so that the discharge time TDIS is not equal to the ideal discharge time, that is, the discharge time TDIS also has an error. Therefore, since the peak voltage VPK has an error and the discharge time TDIS also has an error, the output current IOUT actually varies with the output voltage VOUT of the secondary side SEC of the power converter 100 (as shown in fig. 4), where the vertical axis of fig. 4 is the output current IOUT and the horizontal axis of fig. 4 is the input voltage VAC of the primary side PRI of the power converter 100.
Since the compensation voltage VCOMP is related to the output voltage VOUT and the gate control signal generating circuit can generate the gate control signal GCS to control the on-time TON of the power switch 102 of the power converter 100 according to the compensation voltage VCOMP, the on-time TON of the power switch 102 is related to the output voltage VOUT. Since the on-time TON of the power switch 102 is related to the output voltage VOUT, and the peak voltage VPK can be determined by the sensing voltage VS and the on-time TON of the power switch 102, the peak voltage VPK is also related to the output voltage VOUT. In addition, since the discharge time TDIS of the secondary side SEC of the power converter 100 is related to the on time TON of the power switch 102, the discharge time TDIS is also related to the output voltage VOUT. Therefore, since the peak voltage VPK and the discharging time TDIS are both related to the output voltage VOUT, as shown in fig. 5, the current compensation circuit 202 can generate a compensation current ICC to the sense resistor 104 according to a dc voltage VDC and an auxiliary voltage VZCD, wherein the current compensation circuit 202 receives the auxiliary voltage VZCD through the pin ZCD of the primary controller 200, the compensation current ICC flows to the sense resistor 104 through the pin CS of the primary controller 200 during the on time TON of the power switch 102, and the dc voltage VDC is related to the voltage VHV at the pin HV of the primary controller 200 (for example, the dc voltage VDC is divided by the voltage VHV). In addition, since the voltage VHV is related to the input voltage VAC, the direct-current voltage VDC is also related to the input voltage VAC. In addition, as shown in fig. 1, since the auxiliary voltage VZCD is related to the voltage VAUX generated by the auxiliary winding 103, the auxiliary voltage VZCD is also related to the output voltage VOUT. In addition, as shown in fig. 1, the primary controller 200 receives the voltage VAUX through a pin VCC and a diode 110, and generates an operating voltage in the primary controller 200 according to the voltage VAUX. In addition, as shown in fig. 1, the primary controller 200 is grounded through a pin GND.
As shown in fig. 5, a Digital-to-Analog Converter (DAC) 2022 in the current compensation circuit 202 can convert the auxiliary voltage VZCD into Digital signals DS1 and DS2, but the present invention is not limited to the DAC 2022 being a two-bit DAC. As shown in fig. 5, an operational amplifier 20242, an nmos transistor 20244 and a resistor 20246 in the compensation current generating unit 2024 can determine a current IS according to the dc voltage VDC; then, a first current mirror composed of pmos transistors 20248, 20250, 20252 in the compensation current generating unit 2024 generates the compensation current ICC to the sensing resistor 104 according to the current IS and the digital signals DS1, DS 2. In addition, the operational amplifier 20242, the nmos transistor 20244, the resistor 20246 and the pmos transistors 20248, 20250 and 20252 are coupled with reference to fig. 5, and are not described herein again. In addition, since the current compensation circuit 202 generates the compensation current ICC based on the dc voltage VDC and the auxiliary voltage VZCD as shown in fig. 5, the compensation current ICC is related to both the input voltage VAC and the output voltage VOUT (since the dc voltage VDC is related to the input voltage VAC and the auxiliary voltage VZCD is related to the output voltage VOUT). In addition, as shown in fig. 1, because the compensation current ICC flows to the sensing resistor 104 through the pin CS of the primary controller 200, the compensation current ICC changes the peak current IPK of the primary side PRI of the power converter 100, wherein because the compensation current ICC is related to the input voltage VAC and the output voltage VOUT at the same time, the peak current IPK is also related to the input voltage VAC and the output voltage VOUT at the same time.
In addition, since the on-time TON of the power switch 102 is also larger when the output voltage VOUT is higher, the influence of the error of the on-time TON of the power switch 102 is smaller. Therefore, as shown in fig. 6, when the output voltage VOUT is higher (i.e., the auxiliary voltage VZCD is higher), the compensation current ICC is smaller, i.e., the compensation current ICC decreases with the increase of the output voltage VOUT. In addition, the present invention is not limited to the circuit architecture of the current compensation circuit 202 in fig. 5, that is, a current compensation circuit that can make the compensation current ICC decrease with the increase of the output voltage VOUT falls into the scope of the present invention. In addition, the present invention is not limited to the compensation current generating unit 2024 generating the compensation current ICC in a digital manner as shown in fig. 6, that is, in another embodiment of the present invention, the compensation current generating unit 2024 generates the compensation current ICC in an analog manner. In addition, after the compensation current generating unit 2024 generates the compensation current ICC to the sensing resistor 104, the relationship between the output current IOUT, the output voltage VOUT, and the input voltage VAC may be referred to fig. 7. As shown in fig. 7, although the curves corresponding to the output current IOUT (corresponding to different output voltages VOUT) are flat and consistent, there is an offset between the curves, wherein the offset is related to the smaller gain of the negative feedback loop of the constant current control in the primary controller 200.
Equation (3) is that the negative feedback loop based on the constant current control has a sufficiently large gain, so when the negative feedback loop of the constant current control has a small gain, equation (3) must introduce a factor regarding the gain of the negative feedback loop into equation (4):
Figure GDA0003218703310000091
as shown in equation (4), GCC is the gain of the negative feedback loop. Further, formula (5) can be obtained by substituting formula (1) and formula (2) for formula (4):
Figure GDA0003218703310000092
as shown in equation (5), when the gain GCC of the negative feedback loop is small and the output voltage VOUT varies, the output current IOUT will vary with the output voltage VOUT, so the output current IOUT can be eliminated by adjusting the reference current IREF to eliminate the influence of the gain GCC of the negative feedback loop on the output current IOUT. In addition, as can also be seen from equation (5), the output current IOUT and the reference current IREF are positively correlated, so the reference current IREF provided by the reference current source 2042 must be variable and vary with the output voltage VOUT of the secondary side SEC of the power converter 100 to eliminate the offset between the curves.
Referring to fig. 8, fig. 8 is a schematic diagram illustrating the reference current source 2042. As shown in fig. 8, the operational amplifiers 20422, 20424, the nmos 20426, 20428, the pmos 20430, and the resistor 20432 in the reference current source 2042 determine a first current I1. As shown in fig. 8, a certain voltage vzcm is set according to the maximum value of the operating range of the output voltage VOUT, so that the first current I1 is inversely changed with the auxiliary voltage VZCD, that is, the first current I1 is decreased with the increase of the auxiliary voltage VZCD and the first current I1 is increased with the decrease of the auxiliary voltage VZCD. Since the auxiliary voltage VZCD is positively correlated with the output voltage VOUT, the first current I1 also varies inversely with the output voltage VOUT. Then, a second current mirror formed by the nmos 20428 and the nmos 20434 in the reference current source 2042 can generate a second current I2 according to the first current I1, wherein the ratio of the width-to-length ratio of the nmos 20434 to the width-to-length ratio of the nmos 20428 and the first current I1 can determine the second current I2 according to equation (6), wherein the second current I2 inversely varies with the output voltage VOUT because the first current I1 inversely varies with the output voltage VOUT:
Figure GDA0003218703310000101
as shown in formula (6), (W/L)20434Is the width-to-length ratio of the NMOS transistor 20434, and (W/L)20428Is the width-to-length ratio of nmos transistor 20428.
In addition, as shown in fig. 8, the reference current source 2042 may utilize an operational amplifier 20436, an nmos 20438, a resistor 20440, a reference voltage VREF, and a second current I2 to determine a voltage VVO by equation (7), wherein a capacitor 20442 is used to stabilize the voltage VVO:
VVO＝VREF-(R20440×I2) (7)
as shown in formula (7), R20440The resistance of the resistor 20440, wherein the voltage VVO increases with the increase of the output voltage VOUT when the output voltage VOUT increases because the second current I2 varies inversely with the output voltage VOUT, that is, the voltage VVO varies positively with the output voltage VOUT.
After the voltage VVO is generated, the reference current source 2042 may generate the reference current IREF by using a voltage converter 20444. Because the voltage VVO varies in the forward direction with the output voltage VOUT, the reference current IREF also varies in the forward direction with the output voltage VOUT. Therefore, the offset shown in fig. 7 will be eliminated because the reference current IREF can be changed in the positive direction of the output voltage VOUT (as shown in fig. 9). Therefore, as shown in fig. 9, the primary controller 200 can utilize the compensation current ICC generated by the current compensation circuit 202 and the reference current IREF generated by the reference current source 2042 to make the output current IOUT of the secondary side SEC of the power converter 100 not change with the output voltage VOUT of the secondary side SEC of the power converter 100. In addition, reference may be made to fig. 8 for the coupling relationship between the operational amplifiers 20422, 20424, 20436, the nmos 20426, 20428, 20434, 20438, the pmos 20430, the resistors 20432, 20440, the capacitor 20442 and the vsc, which is not described herein again. In addition, the present invention is not limited to the circuit architecture of the reference current source 2042 in fig. 8, that is, any reference current source that can increase the reference current IREF with the increase of the output voltage VOUT is within the scope of the present invention.
Referring to fig. 1 to 10, fig. 10 is a flowchart illustrating an operation method of a primary controller applied to a primary side of a power converter according to a second embodiment of the present invention. The operation method of fig. 10 is illustrated by using the power converter 100 and the primary controller 200 of fig. 1, the compensation voltage generating circuit 204 of fig. 2, the current compensating circuit 202 of fig. 5 and the reference current source 2042 of fig. 8, and the detailed steps are as follows:
step 1000: starting;
step 1002: the current compensation circuit 202 generates a compensation current ICC to the sense resistor 104 of the primary-side PRI of the power converter 100 according to the dc voltage VDC and the auxiliary voltage VZCD;
step 1004: the compensation voltage generation circuit 204 generates a compensation voltage VCOMP according to the reference current IREF, the discharge time TDIS of the secondary side SEC of the power converter 100, and the peak current IPK;
step 1006: the gate control signal generating circuit generates the gate control signal GCS to the power switch 102 of the primary-side PRI of the power converter 100 according to the compensation voltage VCOMP, and then jumps back to step 1002.
In step 1002, as shown in fig. 5, the current compensation circuit 202 may generate a compensation current ICC to the sensing resistor 104 according to the dc voltage VDC and the auxiliary voltage VZCD, wherein the compensation current ICC flows to the sensing resistor 104 through the pin CS of the primary controller 200 during the on-time TON of the power switch 102, and the dc voltage VDC is related to the voltage VHV at the pin HV of the primary controller 200. In addition, since the voltage VHV is related to the input voltage VAC, the direct-current voltage VDC is also related to the input voltage VAC. In addition, as shown in fig. 1, since the auxiliary voltage VZCD is related to the voltage VAUX generated by the auxiliary winding 103, the auxiliary voltage VZCD is also related to the output voltage VOUT. As shown in fig. 5, the digital-to-analog converter 2022 in the current compensation circuit 202 can convert the auxiliary voltage VZCD into digital signals DS1, DS 2. As shown in fig. 5, the operational amplifier 20242, the nmos transistor 20244 and the resistor 20246 in the compensation current generating unit 2024 can determine the current IS according to the dc voltage VDC; then, the first current mirror composed of the pmos transistors 20248, 20250, 20252 in the compensation current generating unit 2024 can generate the compensation current ICC to the sensing resistor 104 according to the current IS and the digital signals DS1, DS 2. In addition, since the current compensation circuit 202 generates the compensation current ICC based on the dc voltage VDC and the auxiliary voltage VZCD as shown in fig. 5, the compensation current ICC is related to both the input voltage VAC and the output voltage VOUT (since the dc voltage VDC is related to the input voltage VAC and the auxiliary voltage VZCD is related to the output voltage VOUT). In addition, as shown in fig. 1, because the compensation current ICC flows to the sensing resistor 104 through the pin CS of the primary controller 200, the compensation current ICC changes the peak current IPK of the primary side PRI of the power converter 100, wherein because the compensation current ICC is related to the input voltage VAC and the output voltage VOUT at the same time, the peak current IPK is also related to the input voltage VAC and the output voltage VOUT at the same time.
In addition, since the on-time TON of the power switch 102 is also larger when the output voltage VOUT is higher, the influence of the error of the on-time TON of the power switch 102 is smaller. Therefore, as shown in fig. 6, when the output voltage VOUT is higher (i.e., the auxiliary voltage VZCD is higher), the compensation current ICC is smaller, i.e., the compensation current ICC decreases with the increase of the output voltage VOUT. In addition, after the compensation current generating unit 2024 generates the compensation current ICC to the sensing resistor 104, the relationship between the output current IOUT, the output voltage VOUT, and the input voltage VAC may be referred to fig. 7. As shown in fig. 7, although the curves corresponding to the output current IOUT (corresponding to different output voltages VOUT) are flat and consistent, there is an offset between the curves, wherein the offset is related to the smaller gain of the negative feedback loop of the constant current control in the primary controller 200.
In step 1004, as shown in fig. 8, the operational amplifiers 20422, 20424, the nmos 20426, 20428, the pmos 20430, and the resistor 20432 in the reference current source 2042 determine the first current I1. As shown in fig. 8, the constant voltage vzcm is set according to the maximum value of the operating range of the output voltage VOUT, so the first current I1 is inversely changed with the auxiliary voltage VZCD, that is, the first current I1 is decreased with the increase of the auxiliary voltage VZCD and the first current I1 is increased with the decrease of the auxiliary voltage VZCD. Since the auxiliary voltage VZCD is positively correlated with the output voltage VOUT, the first current I1 also varies inversely with the output voltage VOUT. Then, the second current mirror formed by the nmos 20428 and the nmos 20434 in the reference current source 2042 can generate a second current I2 according to the first current I1, wherein the ratio of the width-to-length ratio of the nmos 20434 to the width-to-length ratio of the nmos 20428 and the first current I1 can determine the second current I2 by equation (6), and the second current I2 also inversely varies with the output voltage VOUT because the first current I1 inversely varies with the output voltage VOUT. In addition, as shown in fig. 8, the reference current source 2042 may determine the voltage VVO by equation (7) using the operational amplifier 20436, the nmos 20438, the resistor 20440, the reference voltage VREF, and the second current I2. Since the second current I2 varies inversely with the output voltage VOUT, when the output voltage VOUT increases, the voltage VVO increases with the increase of the output voltage VOUT, that is, the voltage VVO varies positively with the output voltage VOUT. Therefore, after the voltage VVO is generated, the reference current source 2042 can generate the reference current IREF by using the voltage converter 20444. Because the voltage VVO varies in the forward direction with the output voltage VOUT, the reference current IREF also varies in the forward direction with the output voltage VOUT. Then, as shown in fig. 2, the compensation voltage generating circuit 204 can determine the compensation voltage VCOMP at the pin COMP of the primary controller 200 by using the peak current IPK, the discharge time TDIS of the secondary side SEC of the power converter 100, and the reference current IREF.
In step 1006, after the compensation voltage VCOMP is generated, the gate control signal generating circuit (not shown in fig. 1 and 2) generates the gate control signal GCS to control the power switch 102 of the power converter 100 to turn on or off according to the compensation voltage VCOMP.
Therefore, as shown in fig. 9, after the compensation current ICC and the reference current IREF are generated, the primary controller 200 can make the output current IOUT not change with the output voltage VOUT.
In summary, the primary controller applied to the primary side of the power converter and the operating method thereof disclosed by the present invention utilize the compensation current generated by the current compensation circuit and varying in a reverse direction with respect to the output voltage and the reference current generated by the reference current source and varying in a forward direction with respect to the output voltage to make the output current not vary with the output voltage. Therefore, compared with the prior art, the compensation current and the reference current are related to the output voltage, so the invention can effectively eliminate the influence of the output voltage on the output current.
The above description is only a preferred embodiment of the present invention and is not intended to limit the present invention, and various modifications and changes may be made by those skilled in the art. Any modification, equivalent replacement, or improvement made within the spirit and principle of the present invention should be included in the protection scope of the present invention.

Claims (18)

1. A primary controller for a primary side of a power converter, comprising:
a high voltage pin for receiving a rectified voltage, wherein the rectified voltage is related to an input voltage;
a current compensation circuit for generating a compensation current to the sensing resistor of the primary side according to a dc voltage and an auxiliary voltage, wherein the auxiliary voltage is related to an output voltage of the secondary side of the power converter, the compensation current changes a peak voltage of the primary side, and the dc voltage is generated according to the rectified voltage; and
a compensation voltage generating circuit, coupled to the current compensation circuit, for generating a compensation voltage according to a reference current, a discharge time of the secondary side and a peak current, wherein the reference current varies with an output voltage of the secondary side of the power converter;
wherein the compensation current and the reference current are used to make the output current of the secondary side of the power converter not change with the output voltage of the secondary side of the power converter.
2. The primary controller of claim 1, wherein: the power converter is a flyback power converter.
3. The primary controller of claim 1, wherein: the compensation current decreases as the output voltage increases.
4. The primary controller of claim 1, wherein: the reference current increases as the output voltage increases.
5. The primary controller of claim 1, wherein: the output current is related to a discharge time of the secondary side and the peak voltage.
6. The primary controller of claim 1, wherein: the peak current is related to the peak voltage.
7. The primary controller of claim 1, wherein: the discharge time of the secondary side and the peak voltage vary with the output voltage of the secondary side of the power converter.
8. The primary controller of claim 1, wherein: the current compensation circuit is coupled to an auxiliary winding on a primary side of the power converter through a voltage division circuit.
9. The primary controller of claim 1, wherein: the dc voltage is related to an input voltage at a primary side of the power converter.
10. The primary controller of claim 1, further comprising:
the grid control signal generating circuit is used for generating a grid control signal to a power switch on the primary side of the power converter according to the compensation voltage, wherein the grid control signal is used for controlling the power switch to be switched on and off.
11. A method of operating a primary controller applied to a primary side of a power converter, wherein the primary controller includes a high voltage pin, a current compensation circuit, a compensation voltage generation circuit, and a gate control signal generation circuit, the method comprising:
the high voltage pin receives a rectified voltage, wherein the rectified voltage is related to an input voltage; the current compensation circuit generates a compensation current to the sensing resistor of the primary side according to a DC voltage and an auxiliary voltage, wherein the auxiliary voltage is related to the output voltage of the secondary side of the power converter, the compensation current changes the peak voltage of the primary side,
and the direct current voltage is generated according to the rectified voltage;
the compensation voltage generating circuit generates a compensation voltage according to a reference current, the discharge time of the secondary side and a peak current, wherein the reference current can change along with the output voltage of the secondary side of the power converter; and
the grid control signal generating circuit generates a grid control signal to a power switch on the primary side of the power converter according to the compensation voltage, wherein the grid control signal is used for controlling the power switch to be switched on and off;
wherein the compensation current and the reference current are used to make the output current of the secondary side of the power converter not change with the output voltage of the secondary side of the power converter.
12. The method of operation of claim 11, wherein: the compensation current decreases as the output voltage increases.
13. The method of operation of claim 11, wherein: the reference current increases as the output voltage increases.
14. The method of operation of claim 11, wherein: the output current is related to a discharge time of the secondary side and the peak voltage.
15. The method of operation of claim 11, wherein: the peak current is related to the peak voltage.
16. The method of operation of claim 11, wherein: the discharge time of the secondary side and the peak voltage vary with the output voltage of the secondary side of the power converter.
17. The method of operation of claim 11, wherein: the current compensation circuit is coupled to an auxiliary winding on a primary side of the power converter through a voltage division circuit.
18. The method of operation of claim 11, wherein: the dc voltage is related to an input voltage at a primary side of the power converter.
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CN108462393A (en) * 2017-02-20 2018-08-28 通嘉科技股份有限公司 The control circuit and its method of output loss for compensating power supply changeover device

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CN203039589U (en) * 2012-12-12 2013-07-03 杭州士兰微电子股份有限公司 Switch power supply and controller for controlling constant output current thereof
CN104253544A (en) * 2013-06-28 2014-12-31 比亚迪股份有限公司 Compensating circuit of control chip of switch power source
CN103401424A (en) * 2013-07-19 2013-11-20 昂宝电子（上海）有限公司 System and method for regulating output current of power supply transformation system
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