Power Factor Correction Controller and Its Operating Method

Abstract

The present invention discloses a power factor correction controller and an operation method thereof. The power factor correction controller includes a feedback pin, a sensing pin, a current detection circuit, an output voltage detection circuit, and a judgment circuit. The current detection circuit is configured to detect an output current on the secondary side of the power converter according to a feedback voltage on the feedback pin and a sensing voltage on the sensing pin. The output voltage detection circuit is configured to detect an output voltage on the secondary side of the power converter according to the feedback voltage. The judgment circuit is configured to turn on or off a power factor correction circuit coupled to the power converter according to the output current and the output voltage. Therefore, after detecting an output power and the input voltage, the present invention can automatically turn on or off the power factor correction circuit according to the output power and the input voltage to overcome the disadvantages in the prior art during operation.

Description

Technical Field

[0001] The present invention relates to a power factor correction controller and an operation method thereof, and particularly to a power factor correction controller applicable to different output voltages of Universal Serial Bus (USB) power delivery (PD) and an operation method thereof. Background Art

[0002] In the prior art, a power factor correction (PFC) controller applied to a flyback power converter uses a current flowing out of a current source inside the power factor correction controller and a resistor outside the power factor correction controller to set a reference voltage for turning on / off a power factor correction circuit correspondingly coupled to the flyback power converter, wherein the power factor correction circuit is only applicable to a single output voltage output by the flyback power converter. When the load coupled to the flyback power converter is a heavy load, since the conduction loss of the flyback power converter is greater than the switching loss of the flyback power converter, the power factor correction controller turns on the power factor correction circuit; when the load is a light load, since the switching loss is greater than the conduction loss, the power factor correction controller turns off the power factor correction circuit.

[0003] However, when the flyback power converter is applied to Universal Serial Bus (USB) power delivery (PD), the flyback power converter needs to output different output voltages to respond to different output powers of the flyback power converter. However, the power factor correction controller may not be able to correctly turn on / off the power factor correction circuit in response to the different output powers, so the efficiency of the flyback power converter under some specific load conditions (such as 50% load, 75% load) will decrease. Therefore, when the flyback power converter is applied to the Universal Serial Bus power delivery, the user must manually adjust the resistor outside the power factor correction controller according to the different output voltages to change the reference voltage for turning on / off the power factor correction circuit so that the power factor correction circuit is correctly turned on / off. Therefore, for the user, how to overcome the above-mentioned disadvantages of the power factor correction controller during operation has become an important issue. Summary of the Invention

[0004] An embodiment of the present invention discloses a power factor correction controller applied to the primary side of a power converter. The power factor correction controller includes a feedback pin, a sensing pin, a current detection circuit, an output voltage detection circuit, and a judgment circuit. The current detection circuit is coupled to the feedback pin and the sensing pin for detecting the output current of the secondary side of the power converter according to the feedback voltage on the feedback pin and the sensing voltage on the sensing pin. The output voltage detection circuit is coupled to the feedback pin for detecting the output voltage of the secondary side of the power converter according to the feedback voltage. The judgment circuit is coupled to the current detection circuit and the output voltage detection circuit for turning on or off a power factor correction circuit coupled to the power converter according to the output current and the output voltage.

[0005] Another embodiment of the present invention discloses an operation method of a power factor correction controller applied to the primary side of a power converter, where the power factor correction controller includes a feedback pin, a sensing pin, a current detection circuit, an output voltage detection circuit, and a judgment circuit. The operation method includes the current detection circuit detecting the output current of the secondary side of the power converter according to the feedback voltage on the feedback pin and the sensing voltage on the sensing pin; the output voltage detection circuit detecting the output voltage of the secondary side of the power converter according to the feedback voltage; and the judgment circuit turning on or off a power factor correction circuit coupled to the power converter according to the output current and the output voltage.

[0006] The present invention discloses a power factor correction controller and its operation method. The power factor correction controller and the operation method use a current detection circuit to detect the output current of the secondary side of a power converter according to the feedback voltage on a feedback pin and the sensing voltage on a sensing pin, use an output voltage detection circuit to detect the output voltage of the secondary side of the power converter according to the feedback voltage, use an input voltage detection circuit to detect the input voltage input to the primary side of the power converter, and use a judgment circuit to turn on or off a power factor correction circuit coupled to the power converter according to the output current, the output voltage, and the input voltage. Therefore, compared with the prior art, after detecting an output power (the product of the output current and the output voltage) and the input voltage, the present invention can automatically turn on or off the power factor correction circuit according to the output power and the input voltage to overcome the disadvantages of the power factor correction controller disclosed in the prior art during operation. Description of the Drawings

[0007] Figure 1It is a schematic diagram of a power factor correction controller applied to the primary side of a power converter disclosed in the first embodiment of the present invention.

[0008] Figure 2 It is a flowchart of an operation method of a power factor correction controller applied to the primary side of a power converter disclosed in the second embodiment of the present invention.

[0009] Among them, the reference numerals are explained as follows:

[0010] 100 Power converter

[0011] 101 Bridge rectifier

[0012] 102 Optocoupler

[0013] 104 Auxiliary winding

[0014] 106 Voltage dividing circuit

[0015] 108 Power switch

[0016] 110 Primary side winding

[0017] 112 Secondary side winding

[0018] 200 Power factor correction controller

[0019] 202 Feedback pin

[0020] 204 Sensing pin

[0021] 206 Current detection circuit

[0022] 208 Output voltage detection circuit

[0023] 209 Gate control pin

[0024] 210 Judgment circuit

[0025] 211 Drive pin

[0026] 212 Input voltage detection circuit

[0027] 214 Input voltage pin

[0028] 216 Resistor

[0029] 300 Power factor correction circuit

[0030] GCS Gate control signal

[0031] GND Ground pin

[0032] IOUT Output current

[0033] LO Load

[0034] PRI Primary

[0035] SEC Secondary

[0036] VAC Input Voltage

[0037] VOUT Output Voltage

[0038] VS Sensing Voltage

[0039] VCOMP Feedback Compensation Voltage

[0040] VAREF Adjustable Reference Voltage

[0041] VFB Feedback Voltage

[0042] VAUX Auxiliary Voltage

[0043] VCC Power Supply Voltage

[0044] Steps 400 - 408 Detailed Implementation Manner

[0045] Please refer to Figure 1 , Figure 1 is a schematic diagram of a power factor correction controller 200 applied to the primary side PRI of a power converter 100 disclosed in the first embodiment of the present invention. As shown in Figure 1 , the power factor correction controller 200 includes a feedback pin 202, a sensing pin 204, a current detection circuit 206, an output voltage detection circuit 208, a judgment circuit 210, and an input voltage detection circuit 212. The power converter 100 is a flyback power converter, and a power factor correction circuit 300 is coupled between the power converter 100 and a bridge rectifier 101. Additionally, as shown in Figure 1 , the output voltage detection circuit 208 is coupled to the feedback pin 202, the current detection circuit 206 is coupled to the feedback pin 202 and the sensing pin 204, the input voltage detection circuit 212 is coupled to an input voltage pin 214 included in the power factor correction controller 200, and the judgment circuit 210 is coupled to the current detection circuit 206, the output voltage detection circuit 208, and the input voltage detection circuit 212. Additionally, as shown in Figure 1As shown, the primary side PRI of the power converter 100 is isolated from the secondary side SEC of the power converter 100 by an optocoupler 102. The optocoupler 102 can generate a feedback compensation voltage VCOMP to the power factor correction controller 200. However, the feedback compensation voltage VCOMP has nothing to do with the main technical features of the present invention, so it will not be elaborated here. In addition, those skilled in the art of this technology should understand that the power factor correction circuit 300 is used to improve the power factor of the power converter 100 so that the power factor of the power converter 100 approaches 1 and at the same time suppresses the harmonics of an output current IOUT of the power converter 100. And the power factor correction circuit 300 is also well known to those skilled in the art of this technology, so the architecture of the power factor correction circuit 300 will not be elaborated here. In addition, Figure 1 is only a schematic diagram for illustrating the present invention, so some components that have nothing to do with the main technical features of the present invention are omitted. In addition, as Figure 1 shown, the power factor correction controller 200 receives the ground level through a ground terminal pin GND, and the ground level of the primary side PRI of the power converter 100 is different from the ground level of the secondary side SEC of the power converter 100.

[0046] As Figure 1 shown, the output voltage detection circuit 208 is used to receive the feedback voltage VFB on the feedback pin 202. Since the auxiliary voltage VAUX on the auxiliary winding 104 included in the power converter 100 generates the feedback voltage VFB through a voltage dividing circuit 106, and the auxiliary voltage VAUX is related to the output voltage VOUT of the secondary side SEC of the power converter 100, the feedback voltage VFB is also related to the output voltage VOUT. Therefore, the output voltage detection circuit 208 can detect the output voltage VOUT according to the feedback voltage VFB. In addition, the auxiliary voltage VAUX is also used to generate the supply voltage VCC of the power factor correction controller 200.

[0047] In addition, since the auxiliary voltage VAUX is generated after the power switch 108 on the primary side PRI of the power converter 100 is turned off, the current detection circuit 206 coupled to the feedback pin 202 can know the discharge time TDIS of the secondary side SEC of the power converter 100 according to the feedback voltage VFB. In addition, as Figure 1 shown, since the current detection circuit 206 is also coupled to the sensing pin 204, the current detection circuit 206 can use a sampling circuit (not shown in Figure 1 ) to sample the sensing voltage VS on the sensing pin 204 and thereby know the turn-on time of the power switch 108 (that is, the turn-on time of the primary side PRI of the power converter 100). Therefore, an integrator (not shown in Figure 1)The output current IOUT can be detected based on the feedback voltage VFB (related to the output voltage VOUT), the sense voltage VS, the discharge time TDIS, the turn-on time of the power switch 108, and the turns ratio of the primary winding 110 and the secondary winding 112 of the power converter 100. Additionally, as Figure 1 shown, the power factor correction controller 200 transmits a gate control signal GCS to the power switch 108 through a gate control pin 209 to turn on the power switch 108.

[0048] Additionally, as Figure 1 shown, since the input voltage detection circuit 212 is coupled to the input voltage pin 214, the input voltage detection circuit 212 can be used to detect the input voltage VAC input to the primary side PRI of the power converter 100, where the input voltage VAC is an alternating voltage and the input voltage VAC ranges from 90V to 264V. Thus, in an embodiment of the present invention, the determination circuit 210 can be used to linearly or stepwise turn on or off the power factor correction circuit 300 according to the output current IOUT, the output voltage VOUT, and the input voltage VAC, where the determination circuit 210 uses an internal multiplier (not shown in Figure 1 ) to multiply the output current IOUT and the output voltage VOUT to determine the output power POUT of the power converter 100, and linearly or stepwise turn on or off the power factor correction circuit 300 according to the output power POUT and the input voltage VAC. However, in another embodiment of the present invention, the determination circuit 210 linearly or stepwise turns on or off the power factor correction circuit 300 according to the output current IOUT and the output voltage VOUT, where the determination circuit 210 uses the internal multiplier to multiply the output current IOUT and the output voltage VOUT to determine the output power POUT, and linearly or stepwise turns on or off the power factor correction circuit 300 according to the output power POUT.

[0049] In addition, when the load LO coupled to the secondary side SEC of the power converter 100 is a heavy load, since the conduction loss of the power converter 100 is greater than the switching loss of the power converter 100, the power factor correction controller 200 tends to turn on the power factor correction circuit 300; when the load LO is a light load, since the switching loss is greater than the conduction loss, the power factor correction controller 200 tends to turn off the power factor correction circuit 300. Therefore, based on the operation of the power factor correction controller 200 described above and the EU regulation that the power factor correction circuit 300 must be turned on when the output power POUT is greater than 75W, Table 1 can be obtained. Table 1 is the optimal efficiency table for the power converter 100 corresponding to the turning on and off of the power factor correction circuit 300, and Table 1 takes the judgment circuit 210 as an example to turn on or off the power factor correction circuit 300 according to the output current IOUT, output voltage VOUT, load LO, and input voltage VAC.

[0050]

[0051] Table 1

[0052] For example, as shown in Table 1, when the input voltage VAC is 115V, the output voltage VOUT is 15V, the output current IOUT is 5A, and the load LO is 75% of the full load, the judgment circuit 210 turns on the power factor correction circuit 300; when the input voltage VAC is 230V, the output voltage VOUT is 15V, the output current IOUT is 5A, and the load LO is 75% of the full load, the judgment circuit 210 turns off the power factor correction circuit 300.

[0053] In addition, as shown in Table 1, when the input voltage VAC is 115V and the output voltage VOUT is not less than 10V, the judgment circuit 210 may turn on the power factor correction circuit 300; and when the input voltage VAC is 230V and the output voltage VOUT is not less than 15V, the judgment circuit 210 may turn on the power factor correction circuit 300. Therefore, in another embodiment of the present invention, when the output voltage VOUT is greater than a predetermined voltage (for example, 10V), the judgment circuit 210 starts to determine whether to turn on or off the power factor correction circuit 300 according to the output voltage VOUT, output current IOUT, and input voltage VAC. In addition, in another embodiment of the present invention, when the output voltage VOUT is greater than the predetermined voltage (for example, 10V), the judgment circuit 210 starts to determine whether to turn on or off the power factor correction circuit 300 according to the output voltage VOUT and output current IOUT.

[0054] In addition, as Figure 1As shown, an adjustable reference voltage VAREF input to the power factor correction controller 200 can be controlled by a resistor 216 outside the power factor correction controller 200, where the adjustable reference voltage VAREF is used to finely adjust the load point at which the determination circuit 210 turns on and off the power factor correction circuit 300 so as to optimize the efficiency of the power converter 100. That is to say, the adjustable reference voltage VAREF is used to finely adjust the load point at which the determination circuit 210 linearly or stepwise turns on and off the power factor correction circuit 300 so as to optimize the efficiency of the power converter 100.

[0055] In addition, please refer to Figure 1 、 2 , Figure 2 which is a flowchart of an operation method of a power factor correction controller applied to the primary side of a power converter disclosed in the second embodiment of the present invention. Figure 2 The operation method of Figure 1 is described by using the power converter 100, the power factor correction controller 200, and the power factor correction circuit 300 of

[0056] Step 400: Start;

[0057] Step 402: The current detection circuit 206 detects the output current IOUT of the secondary side SEC of the power converter 100 according to the feedback voltage VFB and the sensing voltage VS on the sensing pin 204, and jumps to step 408;

[0058] Step 404: The output voltage detection circuit 208 detects the output voltage VOUT of the secondary side SEC of the power converter 100 according to the feedback voltage VFB, and jumps to step 408;

[0059] Step 406: The input voltage detection circuit 212 detects the input voltage VAC input to the primary side PRI of the power converter 100, and jumps to step 408;

[0060] Step 408: The determination circuit 210 turns on or off the power factor correction circuit 300 according to the output current IOUT, the output voltage VOUT, and the input voltage VAC, and jumps back to step 402, step 404, and step 406.

[0061] In step 402, since the auxiliary voltage VAUX is generated only after the power switch 108 on the primary side PRI of the power converter 100 is turned off, the current detection circuit 206 can know the discharge time TDIS of the secondary side SEC of the power converter 100 according to the feedback voltage VFB. In addition, as Figure 1 shown, the current detection circuit 206 can use the sampling circuit (not shown in Figure 1)Sense the sensing voltage VS on the sampling sensing pin 204 and thereby know the turn-on time of the power switch 108 (i.e., the turn-on time of the primary side PRI of the power converter 100). Thus, the integrator (not shown in Figure 1 ) in the current detection circuit 206 can detect the output current IOUT according to the feedback voltage VFB (related to the output voltage VOUT), the sensing voltage VS, the discharge time TDIS, the turn-on time of the power switch 108, and the turns ratio of the primary side winding 110 and the secondary side winding 112 of the power converter 100.

[0062] In step 404, as Figure 1 shown, the output voltage detection circuit 208 is used to receive the feedback voltage VFB on the feedback pin 202. Since the auxiliary voltage VAUX on the auxiliary winding 104 is divided by the voltage dividing circuit 106 to generate the feedback voltage VFB, and the auxiliary voltage VAUX is related to the output voltage VOUT of the secondary side SEC of the power converter 100, the feedback voltage VFB is also related to the output voltage VOUT. Thus, the output voltage detection circuit 208 can detect the output voltage VOUT according to the feedback voltage VFB.

[0063] In step 406, additionally, as Figure 1 shown, since the input voltage detection circuit 212 is coupled to the input voltage pin 214, the input voltage detection circuit 212 can be used to detect the input voltage VAC input to the primary side PRI of the power converter 100, where the input voltage VAC is between 90V and 264V. Thus, in step 408, the judgment circuit 210 can be used to linearly or stepwise turn on or off the power factor correction circuit 300 according to the output current IOUT, the output voltage VOUT, and the input voltage VAC. The judgment circuit 210 uses the internal multiplier (not shown in Figure 1 ) to multiply the output current IOUT and the output voltage VOUT to determine the output power POUT of the power converter 100, and linearly or stepwise turn on or off the power factor correction circuit 300 according to the output power POUT and the input voltage VAC. Additionally, in another embodiment of the present invention, the judgment circuit 210 uses the internal multiplier to multiply the output current IOUT and the output voltage VOUT to determine the output power POUT, and linearly or stepwise turn on or off the power factor correction circuit 300 according to the output power POUT.

[0064] In addition, as shown in Table 1, when the input voltage VAC is 115V and the output voltage VOUT is not less than 10V, the determination circuit 210 may turn on the power factor correction circuit 300; and when the input voltage VAC is 230V and the output voltage VOUT is not less than 15V, the determination circuit 210 may turn on the power factor correction circuit 300. Therefore, in another embodiment of the present invention, after the output voltage VOUT is greater than the predetermined voltage (e.g., 10V), the determination circuit 210 starts to turn on or off the power factor correction circuit 300 according to the output voltage VOUT, the output current IOUT, and the input voltage VAC. In addition, in another embodiment of the present invention, after the output voltage VOUT is greater than the predetermined voltage (e.g., 10V), the determination circuit 210 starts to turn on or off the power factor correction circuit 300 according to the output voltage VOUT and the output current IOUT. In addition, as Figure 1 shown, the adjustable reference voltage VAREF is used to fine-tune the load point at which the determination circuit 210 linearly or stepwise turns on or off the power factor correction circuit 300 so as to optimize the efficiency of the power converter 100.

[0065] In summary, the power factor correction controller and its operation method disclosed in the present invention use the current detection circuit to detect the output current on the secondary side of the power converter according to the feedback voltage on the feedback pin and the sensing voltage on the sensing pin, use the output voltage detection circuit to detect the output voltage on the secondary side of the power converter according to the feedback voltage, use the input voltage detection circuit to detect the input voltage input to the primary side of the power converter, and use the determination circuit to turn on or off the power factor correction circuit according to the output current, the output voltage, and the input voltage. Therefore, compared with the prior art, after detecting the output power (the product of the output current and the output voltage) and the input voltage, the present invention can automatically turn on or off the power factor correction circuit according to the output power and the input voltage to overcome the disadvantages of the power factor correction controller disclosed in the prior art during operation.

[0066] The above are only the preferred embodiments of the present invention and are not intended to limit the present invention. For those skilled in the art, the present invention may have various modifications and changes. Any modification, equivalent replacement, improvement, etc. made within the spirit and principle of the present invention shall be included within the protection scope of the present invention.

Claims

1. A power factor correction controller applied to the primary side of a power converter, characterized in that Comprising: A feedback pin; A sensing pin; A current detection circuit, coupled to the feedback pin and the sensing pin, for detecting an output current of a secondary side of the power converter according to a feedback voltage on the feedback pin and a sensing voltage on the sensing pin; An output voltage detection circuit, coupled to the feedback pin, for detecting an output voltage of the secondary side of the power converter according to the feedback voltage; Detecting the output voltage of the secondary side of the power converter; An input voltage detection circuit, coupled to an input voltage pin included in the power factor correction controller, for detecting an input voltage input to a primary side of the power converter, wherein the input voltage is an alternating current voltage; And A judgment circuit, coupled to the current detection circuit and the output voltage detection circuit, for multiplying the output current and the output voltage by an internal multiplier to determine an output power of the power converter and further determine a load state, and for turning on or off a power factor correction circuit coupled to the power converter according to the load state, the output voltage, and the input voltage; Wherein when the output voltage is less than a predetermined voltage and the load state is a light load, the judgment circuit turns off the power factor correction circuit.

2. The power factor correction controller according to claim 1, characterized in that: The power converter is a flyback power converter.

3. The power factor correction controller according to claim 1, characterized in that: The judgment circuit turns on or off the power factor correction circuit linearly or stepwise according to the load state, the output voltage, and the input voltage.

4. The power factor correction controller according to claim 1, characterized in that: The judgment circuit multiplies the output current and the output voltage by an internal multiplier to determine the output power of the power converter, and turns on or off the power factor correction circuit according to the output power.

5. The power factor correction controller according to claim 1, characterized in that: After the output voltage is greater than a predetermined voltage, the judgment circuit starts to turn on or off the power factor correction circuit according to the output voltage and the output current.

6. An operation method of a power factor correction controller applied to the primary side of a power converter, wherein the power factor correction controller includes a feedback pin, a sensing pin, a current detection circuit, an output voltage detection circuit and a judgment circuit, characterized in that Comprising: The current detection circuit detects an output current of the secondary side of the power converter according to a feedback voltage on the feedback pin and a sensing voltage on the sensing pin; The output voltage detection circuit detects an output voltage of the secondary side of the power converter according to the feedback voltage; The input voltage detection circuit detects an input voltage input to the primary side of the power converter, wherein the input voltage is an alternating current voltage; and The judgment circuit multiplies the output current and the output voltage by an internal multiplier to determine the output power of the power converter and further determine a load state, and for turning on or off a power factor correction circuit coupled to the power converter according to the load state, the output voltage, and the input voltage; Wherein when the output voltage is less than a predetermined voltage and the load state is a light load, the judgment circuit turns off the power factor correction circuit.

7. The operation method according to claim 6, characterized in that: The judgment circuit turns on or off the power factor correction circuit linearly or stepwise according to the load state, the output voltage, and the input voltage.

8. The operation method according to claim 6, characterized in that: The determination circuit utilizes an internal multiplier to multiply the output current and the output voltage to determine the output power of the power converter, and turns on or off the power factor correction circuit according to the output power.

9. The operation method according to claim 6, characterized in that: After the output voltage is greater than a predetermined voltage, the determination circuit starts to turn on or off the power factor correction circuit according to the output voltage and the output current.

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