Output feedback circuit and operation method thereof

Abstract

An output feedback circuit is used for providing a feedback signal to a conversion circuit, so that the conversion circuit balances output power at different output voltages according to the feedback signal. The output feedback circuit comprises a compensation circuit and a feedback circuit, and the compensation circuit is coupled with the output end of the conversion circuit. The feedback circuit is coupled to the compensation circuit and receives a current detection signal corresponding to the output current of the conversion circuit. The compensation circuit provides a reference standard according to the magnitude of the output voltage so as to compensate the current detection signal or the first reference voltage, and the feedback circuit samples the current detection signal under the compensation of the reference standard so as to provide a feedback signal.

Description

Technical Field

[0001] The present invention relates to an output feedback circuit and an operation method thereof, and more particularly to an output feedback circuit with a function of balancing output power and an operation method thereof. Background Art

[0002] Due to the development of technology, electronic devices have become increasingly popular, and the convenience and portability of electronic devices are becoming more and more important. Therefore, battery-powered technology is increasingly relied on. In battery-powered technology, most battery charging and discharging rely on power converters. In application modes such as battery charging and large capacitive loads, the power converter needs to control the output current / power. Currently, the power converter generally controls the output current by adding a constant current function, but this will cause the output power to decrease at low output voltages and increase at high output voltages. In this situation, the power converter needs to be designed according to the highest voltage / power, which will result in a low utilization rate of the power converter at low output voltages.

[0003] In addition, in the field of battery charging and discharging, some power converters use a constant power controller (such as, but not limited to, devices such as ICs and MCUs) to sample the output voltage or output current so that the controller can actively adjust the output current according to the power converter at different output voltages. However, this method requires the use of a high-order controller, which increases the cost of the power converter and easily makes the product lose competitiveness.

[0004] Therefore, how to design an output feedback circuit and an operation method thereof to reduce the cost of the power converter without using a constant power controller is a major issue that the inventors of this case want to study. Summary of the Invention

[0005] To solve the above problems, the present invention provides an output feedback circuit. The output feedback circuit of the present invention is used to provide a feedback signal to a conversion circuit, so that the conversion circuit balances the output power at different output voltages according to the feedback signal. The output feedback circuit includes a compensation circuit and a feedback circuit, and the compensation circuit is coupled to the output terminal of the conversion circuit. The feedback circuit is coupled to the compensation circuit and receives a current detection signal corresponding to the output current of the conversion circuit. Among them, the compensation circuit provides a reference benchmark according to the magnitude of the output voltage to compensate the current detection signal or the first reference voltage, and the feedback circuit samples the current detection signal under the compensation of the reference benchmark to provide a feedback signal.

[0006] To solve the above problems, the present invention provides an operation method for an output feedback circuit. The output feedback circuit of the present invention is used to provide a feedback signal to a conversion circuit, so that the conversion circuit can balance the output power at different output voltages according to the feedback signal. The operation method of the output feedback circuit includes the following steps: (a) receiving a current detection signal corresponding to the output current of the conversion circuit; (b) providing a reference benchmark according to the magnitude of the output voltage to compensate the current detection signal or a first reference voltage; (c) sampling the current detection signal under the compensation of the reference benchmark to provide a feedback signal.

[0007] The beneficial effect of the present invention is that: by using a specific output feedback circuit to implement the operation mode of the constant power mode (CP Mode) of the power converter, the conversion circuit can balance the output power at different output voltages according to the feedback signal. Therefore, compared with the prior art, this embodiment can use a controller without the constant power mode (CP Mode) to reduce the cost of the power converter and improve the competitiveness of the product. Brief Description of the Drawings

[0008] Figure 1 It is a circuit block diagram of the conversion circuit of this embodiment; Figure 2A It is a circuit schematic diagram of the first embodiment of the output feedback circuit of this embodiment; Figure 2B It is a circuit schematic diagram of the second embodiment of the output feedback circuit of this embodiment; Figure 2C It is a circuit schematic diagram of the third embodiment of the output feedback circuit of this embodiment; Figure 3A It is a circuit schematic diagram of the fourth embodiment of the output feedback circuit of this embodiment; Figure 3B It is a circuit schematic diagram of the fifth embodiment of the output feedback circuit of this embodiment; and Figure 4 It is a flowchart of the operation method of the output feedback circuit of this embodiment.

[0009] Among them, 100: power converter, 1: conversion circuit, 1A: output terminal, 2: controller, 3: output feedback circuit, 30: compensation circuit, 302: first voltage division circuit, P1: first voltage division node, Q: transistor, E, C: input terminal, C, E: output terminal, B: control terminal, 304: third voltage division circuit, P3: third voltage division node, 32: feedback circuit, 320: second voltage division circuit, P2: second voltage division node, 322: comparator, OP: operational amplifier, (+): positive input terminal, (-): negative input terminal, O: operational amplifier output terminal, 324: fourth voltage division circuit, P4: fourth voltage division node, 34: optocoupler circuit, OC: optocoupler, D1, D2: diodes, R1~R11: resistors, 200: load, Po: output power, Vin: input voltage, Vo: output voltage, Vref1: first reference voltage, Vref2: second reference voltage, V1: first voltage, V2: second voltage, V3: third voltage, Vs: sampling voltage, V: voltage, Io: output current, I, Ib: current, Sf: feedback signal, PWM: pulse width modulation signal, Si: current detection signal, Sc: comparison signal, Cv: reference, (S100)~(S300): steps Detailed implementation manners Regarding the technical content and detailed description of the present invention, it is described in detail below in conjunction with the drawings: Please refer to Figure 1 It is a circuit block diagram of the conversion circuit of this embodiment. The power converter 100 receives the input voltage Vin and provides the output voltage Vo to supply power to the load 200 coupled to the backend. Among them, the power converter 100 can operate in the constant current mode (CC Mode). Therefore, the load 200 is preferably an energy storage device such as a battery, but is not limited thereto. The power converter 100 includes a conversion circuit 1, a controller 2, and an output feedback circuit 3, and the output feedback circuit 3 is coupled between the conversion circuit 1 and the controller 2. The output feedback circuit 3 provides a feedback signal Sf to the controller 2 according to the output voltage Vo and the output current Io at the output terminal 1A of the conversion circuit 1, so that the controller 2 can adjust the pulse width modulation signal PWM provided to the conversion circuit 1 according to the feedback signal Sf to control the conversion circuit 1 to adjust and stabilize the output power.

[0010] Among them, the conversion circuit 1 can be an isolated conversion circuit with an isolation transformer to isolate the primary side circuit and the secondary side circuit (such as but not limited to flyback, LLC resonant, etc. conversion circuits). Alternatively, the conversion circuit 1 can also be a non-isolated conversion circuit without an isolation transformer (such as but not limited to boost, buck, etc. conversion circuits). In addition, the power converter 100 is characterized in that the controller 2 can adjust the voltage level of the output voltage according to the requirements of the load 200, and its adjustable range is, for example but not limited to, 3V to 20V, to meet the requirements of the load 200, especially when the load is a battery, the requirements of the battery platform voltage.

[0011] The main feature is that in this embodiment, the constant power mode (CP Mode) operation of the power converter 100 is realized through a specific output feedback circuit 3, so that the conversion circuit 1 can balance the output power Po at different output voltages Vo according to the feedback signal Sf. Therefore, compared with the prior art, this embodiment can use a controller 2 without a constant power mode (CP Mode) to reduce the cost of the power converter 100 and improve the product competitiveness. Specifically, the output feedback circuit 3 of this embodiment includes a compensation circuit 30 and a feedback circuit 32. The compensation circuit 30 is coupled to the output terminal 1A of the conversion circuit 1, and the feedback circuit 32 is coupled to the compensation circuit 30 and the controller 2. The power converter 100 can detect the output current Io of the conversion circuit 1 through, for example but not limited to, a current detection circuit (not shown in the figure), and provide a current detection signal Si corresponding to the output current Io to the feedback circuit 32. Among them, the current detection circuit (not shown in the figure) is not limited to being coupled to the output terminal 1A of the conversion circuit 1, and it can be coupled to a suitable position according to the different circuit structures of the conversion circuit 1.

[0012] Furthermore, the compensation circuit 30 provides a reference level Cv according to the magnitude of the output voltage Vo to compensate the current detection signal Si or the first reference voltage Vref1. When the voltage level of the output voltage Vo becomes higher (for example, but not limited to, when it is increased to 20V), the compensation circuit 30 lowers the reference level Cv. Conversely, when the voltage level of the output voltage Vo becomes lower (for example, but not limited to, when it is decreased to 5V), the compensation circuit 30 raises the reference level Cv. The feedback circuit 32 compensates the current detection signal Si or the first reference voltage Vref1 for the reference level Cv, samples the current detection signal Si under the compensation of the reference level Cv, and provides a feedback signal Sf according to the sampling result. Therefore, when the voltage level of the output voltage Vo becomes higher, the controller 2 lowers the current limit value of the output current Io according to the feedback signal Sf, and when the voltage level of the output voltage Vo becomes lower, the controller 2 raises the current limit value of the output current Io according to the feedback signal Sf. In this way, the conversion circuit 1 can balance the output power Po at different output voltages Vo according to the feedback signal Sf, and further enable the power converter 100 to provide an operation mode of constant power mode (CP Mode).

[0013] On the other hand, since the controller 2 has other operation modes (such as, but not limited to, constant voltage mode, constant current mode, etc.). Therefore, the compensation circuit 30 may further include a trigger switch (not shown in the figure). When the power converter 100 has a demand for constant power output, the controller 2 can incorporate the compensation circuit 30 by turning on the trigger switch (not shown in the figure) to provide an operation mode of constant power mode (CP Mode). Conversely, when the power converter 100 does not have a demand for constant power output, the controller 2 can disable the compensation circuit 30 by turning off the trigger switch (not shown in the figure) to not provide an operation mode of constant power mode (CP Mode).

[0014] Please refer to Figure 2A for the circuit schematic diagram of the first embodiment of the output feedback circuit of this embodiment, and also refer to Figure 1. The compensation circuit 30 includes a first voltage dividing circuit 302 and a transistor Q. The first voltage dividing circuit 302 is coupled to the output terminal 1A to receive the output voltage Vo, and provides a first voltage V1 at the first voltage dividing node P1 according to the variation of the output voltage Vo. Among them, the first voltage dividing circuit 302 may be composed of resistors R1, R2 connected in series and a resistor R3 coupled to the first voltage dividing node P1, but is not limited thereto. When the voltage level of the output voltage Vo is relatively high, the first voltage V1 divided at the first voltage dividing node P1 is relatively high, and vice versa. The transistor Q may be a bipolar junction transistor (BJT, but is not limited thereto), and includes an input terminal E, an output terminal C, and a control terminal B. The transistor Q is coupled to the feedback circuit 32 (through the input terminal E and the output terminal C), and the control terminal B is coupled to the first voltage dividing node P1 (through the resistor R3) to receive the first voltage V1. Therefore, the transistor Q can adjust the current I flowing through the transistor Q according to the variation of the first voltage V1.

[0015] Specifically, the transistor Q is mainly configured to operate in the amplification region. The current I flows through the input terminal E and the output terminal C, and the current I is controlled by the base current Ib between the input terminal E and the control terminal B of the transistor Q. Therefore, when the voltage level of the output voltage Vo is relatively high (for example, but not limited to 15V), as the output voltage Vo increases, the voltage at the control terminal B remains unchanged, but the first voltage V1 increases, causing the voltage across the resistor R3 to decrease (that is, the voltage difference between the voltage at the control terminal B and the first voltage V1 becomes smaller), resulting in a decrease in the current flowing through the resistor R3. Therefore, the base current Ib at the control terminal B decreases, causing the current I flowing through the input terminal E and the output terminal C to also decrease. Conversely, when the voltage level of the output voltage Vo is relatively low (for example, but not limited to 3V), as the output voltage Vo decreases, the voltage at the control terminal B still remains unchanged, but the first voltage V1 decreases, causing the voltage across the resistor R3 to increase (that is, the voltage difference between the voltage at the control terminal B and the first voltage V1 becomes larger), resulting in an increase in the current flowing through the resistor R3. Therefore, the base current Ib at the control terminal B increases, causing the current I flowing through the input terminal E and the output terminal C to also increase. Therefore, in summary, in Figure 2A the embodiment, the reference standard Cv is the value of the current I, and the current I is inversely proportional to the first voltage V1.

[0016] The feedback circuit 32 includes a second voltage dividing circuit 320 and a comparator 322. The second voltage dividing circuit 320 receives the first reference voltage Vref1 and provides a second voltage V2 at the second voltage dividing node P2 according to the first reference voltage Vref1. Moreover, the second voltage dividing node P2 is coupled to the transistor Q. Among them, the second voltage dividing circuit 320 may be composed of resistors R4 and R5 connected in series, but is not limited thereto. Also, the input terminal E and the output terminal C of the transistor Q are respectively coupled to both ends of the resistor R4. The comparator 320 receives the second voltage V2 through the positive input terminal (+) and receives the current detection signal Si through the negative input terminal (-) to provide a comparison signal Sc at the operational amplifier output terminal O according to the second voltage V2 and the current detection signal Si.

[0017] Among them, when the conversion circuit 1 is an isolated conversion circuit, the feedback circuit 32 may include an optocoupler circuit 34. The optocoupler circuit 34 includes an optocoupler OC, and one end of the optocoupler OC is coupled to the secondary side circuit of the conversion circuit 1, and the other end is coupled to the output terminal of the comparator 32. Also, the optocoupler circuit 34 may also selectively include diodes D1 and D2 for unidirectional conduction to avoid power backflow. On the other hand, when the conversion circuit 1 is a non-isolated conversion circuit, the operational amplifier output terminal O of the comparator 320 may be coupled to other feedback circuits of the conversion circuit 1 (such as but not limited to a comparison circuit, an amplification circuit, etc.). However, it is not limited to the above illustrative examples, and it mainly depends on the type of the controller 2 and the requirements of the conversion circuit 1.

[0018] Furthermore, the second voltage V2 varies according to the magnitude of the current I. Therefore, when the current I flowing through the input terminal E (the collector C in Figure 2A the embodiment is the collector C) and the output terminal C (the emitter E in Figure 2A the embodiment is the emitter E) decreases (i.e., when the output voltage Vo is larger), the second voltage V2 divided by the second voltage dividing node P2 is smaller (such as but not limited to 2V). On the contrary, when the current I increases, the second voltage V2 divided by the second voltage dividing node P2 is higher (such as but not limited to 2.5V). Also, in one embodiment, when the output current Io is under specific conditions (such as but not limited to no load or full load), the channel of the transistor Q can be designed to be fully conductive or fully non-conductive (similar to a switch) to provide the function of bypassing the resistor R4 or not.

[0019] When the second voltage V2 divided by the second voltage dividing node P2 is small, the comparison signal Sc has a larger coverage range at a low level (for example, but not limited to 0V) (that is, it is easier to be triggered to a low level), so that the emitting end of the optocoupler OC is easier to emit a brighter light (that is, the feedback signal Sf represents the brightness of the light). Thus, the controller 2 can reduce the current limiting value of the output current Io according to the feedback signal Sf. On the contrary, the comparison signal Sc has a larger coverage range at a high level (for example, but not limited to 5V) (that is, it is easier to be triggered to a high level), so that the emitting end of the optocoupler OC is easier to emit a dimmer light. Thus, the controller 2 can increase the current limiting value of the output current Io according to the feedback signal Sf. Through the above operation mode, the feedback circuit 32 can sample the current detection signal Si and the second voltage V2 to provide the feedback signal Sf, and adjust the feedback signal Sf according to the magnitude of the output voltage Vo to change the current limiting value of the output current Io.

[0020] Please refer to Figure 2B which is a schematic circuit diagram of the second embodiment of the output feedback circuit of this embodiment. Also refer to Figures 1 - 2A . Figure 2B And Figure 2A the difference is that Figure 2B the transistor Q is coupled to both ends of the resistor R5. And due to the different coupling positions, the types of the transistor Q are different. In Figure 2A the transistor is of PNP type, and in Figure 2B the transistor is of NPN type. In Figure 2B the input terminal C and the output terminal E of the transistor Q happen to be Figure 2A opposite to those in Figure 2A , but its operation mode is similar to that of

[0021] Please refer to Figure 2C which is a schematic circuit diagram of the third embodiment of the output feedback circuit of this embodiment. Also refer to Figures 1 - 2B . In Figure 2C the structure of the compensation circuit 30 is similar to that of Figure 2A, the difference is that the input terminal E of the transistor Q receives the second reference voltage Vref2, and the output terminal of the transistor Q is coupled to the negative input terminal (-) of the comparator 322. Therefore, the transistor Q can also adjust the current I according to the variation of the first voltage V1. That is, the change in the voltage difference between the second reference voltage Vref2 and the first voltage V1 can correspondingly generate a change in the current Ib in the resistor R3, and thereby adjust the current I. Moreover, when the current I changes, the current I flows through the resistor R6 and generates a voltage across the two ends of the resistor R6, causing the current detection signal Si to generate a sampling voltage Vs at the negative input terminal (-) of the comparator 322 through the voltage across the resistor R6.

[0022] When the current I is smaller, the voltage across the resistor R6 is smaller, making the sampling voltage Vs larger. Conversely, the voltage across the resistor R6 is larger, making the sampling voltage Vs smaller. Therefore, when the sampling voltage Vs is larger, the coverage range where the comparison signal Sc is at a low level (such as but not limited to 0V) is larger (that is, it is easier to trigger to a low level), so that the controller 2 can reduce the current limit value of the output current Io according to the feedback signal Sf. Conversely, the current limit value of the output current Io is increased. Therefore, Figure 2C The operation mode of Figure 2A is exactly the opposite of 2B . In Figure 2A , 2B , mainly the constant current point of the first reference voltage Vref1 is compensated (that is, the first reference voltage Vref1 is adjusted), and in Figure 2C , mainly the constant current point of the current detection signal Si is compensated (that is, the current detection signal Si is adjusted). However, no matter which of the above compensations is performed, it is for the gap point (i.e., the reference benchmark Cv) between the current detection signal Si and the first reference voltage Vref1. Therefore, both of these operation modes can achieve the effect of enabling the conversion circuit 1 to balance the output power Po when the output voltage Vo is different according to the feedback signal Sf, and further enabling the power converter 100 to provide the operation mode of the constant power mode (CPMode).

[0023] Please refer to Figure 3A which is the circuit schematic diagram of the fourth implementation manner of the output feedback circuit of this embodiment, and also refer to Figures 1 - 2C . In Figure 3A , mainly the operational amplifier OP is used to replace the Figures 2A - 2C transistor Q. Moreover, since the individual parameter deviation of the operational amplifier OP is small and the temperature stability is better, compared with the transistor Q, Figure 3AThe compensation circuit 30 can achieve precise control, and the control effect is less affected by temperature. When the output voltage Vo changes, the constant power value can be more precisely fixed at a certain value. Specifically, the operational amplifier OP includes a positive input terminal (+), a negative input terminal (-), and an operational amplifier output terminal O. The negative input terminal (-) is coupled to the first voltage division node P1 and the operational amplifier output terminal O to form a negative feedback amplifier circuit, so that the compensation circuit 30 can adjust the first reference voltage Vref1 of the operational amplifier output terminal O according to the change of the first voltage V1.

[0024] Furthermore, the compensation circuit 30 further includes a third voltage division circuit 304. The third voltage division circuit 304 receives the second reference voltage Vref2 and is coupled to the positive input terminal (+) to provide a third voltage V3 at the third voltage division node P3 according to the second reference voltage Vref2. Among them, the third voltage division circuit 304 can be composed of resistors R8 and R9 connected in series, but is not limited thereto. Since the negative input terminal (-) of the operational amplifier OP is coupled to the operational amplifier output terminal O through the resistor R7, the voltage of the operational amplifier output terminal O is determined by the current flowing through the resistor R7, and the current flowing through the resistor R7 is determined by the first voltage V1. Therefore, when the voltage level of the output voltage Vo is relatively high, the first voltage V1 divided by the first voltage division node P1 is relatively high, so that the voltage difference between the first voltage V1 and the third voltage V3 is relatively low (through virtual ground), resulting in a relatively low first reference voltage Vref1. On the contrary, the first reference voltage Vref1 is relatively high. Therefore, in Figure 3A , the reference datum Cv is the value of the first reference voltage Vref1, and the first reference voltage Vref1 is inversely proportional to the first voltage V1.

[0025] When the first reference voltage Vref1 is relatively low, the second voltage V2 divided by the second voltage division circuit 320 is relatively low. When the second voltage V2 is smaller and compared with the current detection signal Si, the comparison signal Sc output by the comparator 322 is at a low level (such as but not limited to 0V) for a larger range (that is, it is easier to trigger to a low level). Therefore, the controller 2 can reduce the current limiting value of the output current Io according to the feedback signal Sf. On the contrary, when the first reference voltage Vref1 is relatively high, the comparison signal Sc is at a high level (such as but not limited to 5V) for a larger range (that is, it is easier to trigger to a high level), so that the controller 2 can increase the current limiting value of the output current Io according to the feedback signal Sf.

[0026] Please refer to Figure 3B which is a schematic circuit diagram of the fifth embodiment of the output feedback circuit of this embodiment. Please also refer to Figures 1 - 2C . Figure 3B The principle is similar to Figure 3A , and it mainly also uses the operational amplifier OP to enable the compensation circuit 30 to achieve the effect of precise control. And Figure 3B andFigure 3A The difference is that Figure 3B mainly compensates for the constant current point of the current detection signal Si (i.e., adjusts the current detection signal Si). Specifically, the operational amplifier OP also includes a positive input terminal (+), a negative input terminal (-), and an operational amplifier output terminal O, and the positive input terminal (+) is coupled to the first voltage division node P1. The third voltage division circuit 304 is coupled between the negative input terminal (-) and the operational amplifier output terminal O, and the operational amplifier output terminal O is coupled to the feedback circuit 32. Therefore, the operational amplifier OP can form a non-inverting amplifier circuit, so that the compensation circuit 30 can adjust the voltage V at the operational amplifier output terminal O according to the change of the first voltage V1.

[0027] Furthermore, the third voltage division circuit 304 can also be composed of resistors R8 and R9 connected in series. The resistor R8 is coupled between the negative input terminal (-) and the operational amplifier output terminal O, and the resistor R9 is coupled to the resistor R8, but it is not limited thereto. Since the negative input terminal (-) of the operational amplifier OP is coupled to the operational amplifier output terminal O through the resistor R8, the voltage at the operational amplifier output terminal O is affected by the resistor R8, and the current flowing through the resistor R8 is determined by the first voltage V1 (that is, the voltage at the positive input terminal (+) will change due to the change of the first voltage V1, and the third voltage V3 is affected through the principle of virtual ground of the operational amplifier OP). Therefore, when the third voltage V3 changes, the current flowing through the resistor R8 changes accordingly, resulting in the change of the voltage V. When the voltage level of the output voltage Vo is relatively high, the first voltage V1 divided by the first voltage division node P1 is relatively high, making the voltage V relatively high (through virtual ground). On the contrary, the voltage V is relatively low. So, in Figure 3B the reference benchmark Cv is the value of the voltage V, and the voltage V is proportional to the first voltage V1.

[0028] On the other hand, the feedback circuit 32 further includes a fourth voltage division circuit 324. The fourth voltage division circuit 324 is coupled between the compensation circuit 30 and the negative input terminal (-) of the comparator 322, and receives the current detection signal Si to provide a sampling voltage Vs at the fourth voltage division node P4 according to the change of the voltage V. Among them, the fourth voltage division circuit 324 can be composed of resistors R10 and R11 connected in series, but it is not limited thereto. The resistor R11 is coupled between the negative input terminal (-) of the comparator 322 and the operational amplifier output terminal O, and the resistor R10 is coupled to the resistor R11 and receives the current detection signal Si. Since the negative input terminal (-) of the comparator 322 is coupled to the operational amplifier output terminal O through the resistor R11, when the voltage V at the operational amplifier output terminal O changes, the sampling voltage Vs will change accordingly (that is, the fourth voltage division circuit 324 divides the voltage difference between the current detection signal Si and the voltage V to generate a sampling voltage Vs at the fourth voltage division node P4, and the sampling voltage Vs changes following the change of the voltage V).

[0029] When the voltage V is relatively high, the sampled voltage Vs divided by the fourth voltage dividing circuit 324 is relatively low. And when the second voltage V2 is smaller and compared with the detection signal Si, the comparison signal Sc output by the comparator 322 is at a low level (for example, but not limited to 0V) for a larger coverage range (that is, it is more likely to be triggered to a low level). Therefore, the controller 2 can adjust down the current limiting value of the output current Io according to the feedback signal Sf. On the contrary, when the voltage V is relatively low, the comparison signal Sc is at a high level (for example, but not limited to 5V) for a larger coverage range (that is, it is more likely to be triggered to a high level), enabling the controller 2 to adjust up the current limiting value of the output current Io according to the feedback signal Sf.

[0030] Please refer to Figure 4 which is a flowchart of the operation method of the output feedback circuit of this embodiment, and please also refer to Figures 1 - 3B . The output feedback circuit 3 of this embodiment is mainly used to provide the feedback signal Sf to the conversion circuit 1, so that the conversion circuit 1 can balance the output power Po at different output voltages Vo according to the feedback signal Sf. Therefore, the operation method of the output feedback circuit 3 includes receiving a current detection signal corresponding to the output current of the conversion circuit (S100). A preferred implementation is that the power converter 100 can detect the output current Io of the conversion circuit 1 through, for example, but not limited to, a current detection circuit (not shown in the figure), and provide the current detection signal Si corresponding to the output current Io to the feedback circuit 32.

[0031] Then, provide a reference benchmark according to the magnitude of the output voltage to compensate the current detection signal or the first reference voltage (S200). A preferred implementation is that the compensation circuit 30 provides a reference benchmark Cv according to the magnitude of the output voltage Vo to compensate the current detection signal Si or the first reference voltage Vref1. When the voltage level of the output voltage Vo becomes higher (for example, but not limited to, when it is increased to 20V), the compensation circuit 30 reduces the reference benchmark Cv. On the contrary, when the voltage level of the output voltage Vo becomes lower (for example, but not limited to, when it is decreased to 5V), the compensation circuit 30 increases the reference benchmark Cv.

[0032] Finally, sample the current detection signal to provide the feedback signal (S300). A preferred implementation is that the feedback circuit 32 compensates the current detection signal Si or the first reference voltage Vref1 for the reference benchmark Cv, samples the current detection signal Si under the compensation of the reference benchmark Cv, and provides the feedback signal Sf according to the sampling result. Therefore, when the voltage level of the output voltage Vo becomes higher, the controller 2 reduces the current limiting value of the output current Io according to the feedback signal Sf, and when the voltage level of the output voltage Vo becomes lower, the controller 2 increases the current limiting value of the output current Io according to the feedback signal Sf. It is worth mentioning that in an embodiment, the detailed operation method of the output feedback circuit 3 of this embodiment can be referred to Figures 2A - 3B , and will not be elaborated here.

[0033] In summary Figures 1 - 4 As shown above, the power converter 100 of this embodiment can compensate the constant current point through a low-cost output feedback circuit to achieve the operation mode of the constant power mode (CP Mode). When the output voltage Vo is low, it is matched with a large output current Io, and when the output voltage Vo is high, it is matched with a small output current Io, which can reduce the difference in the output power Po at different output voltages Vo, thereby reducing the peak power requirement of the design and reducing the electrical stress and overall cost of the components of the power converter 100.

Claims

1. An output feedback circuit for providing a feedback signal to a conversion circuit so that the conversion circuit balances output power at different output voltages according to the feedback signal, the output feedback circuit comprising: A compensation circuit coupled to the output end of the conversion circuit; and A feedback circuit coupled to the compensation circuit and receiving a current detection signal corresponding to an output current of the conversion circuit; The compensation circuit provides a reference base according to the output voltage to compensate the current detection signal or the first reference voltage, and the feedback circuit samples the current detection signal under the compensation of the reference base to provide the feedback signal.

2. The output feedback circuit according to claim 1, characterized in that: The compensation circuit includes: a first voltage-dividing circuit coupled to the output terminal and providing a first voltage at a first voltage-dividing node according to a change in the output voltage; and a transistor coupled to the feedback circuit and coupled to the first voltage-dividing node through a control terminal to adjust a current flowing through the transistor according to a change in the first voltage; The reference standard is the value of the current, and the current is inversely proportional to the first voltage.

3. The output feedback circuit according to claim 2, characterized in that: The feedback circuit includes: A second voltage-dividing circuit provides a second voltage at a second voltage-dividing node according to the first reference voltage, and the second voltage-dividing node is coupled to the transistor; A comparator receives the second voltage and the current detection signal to provide a comparison signal according to the second voltage and the current detection signal; The transistor adjusts the current according to the variation of the first voltage, so as to change the second voltage through the adjustment of the current, and the feedback circuit provides the feedback signal according to the comparison signal.

4. The output feedback circuit according to claim 2, characterized in that: The feedback circuit includes: A second voltage dividing circuit, providing a second voltage at a second voltage dividing node according to the first reference voltage; and a comparator, receiving the second voltage; The transistor adjusts the current according to the variation of the first voltage to adjust the current detection signal to a sampling voltage through the current, and the feedback circuit provides a comparison signal according to the sampling voltage and the second voltage to provide the feedback signal according to the comparison signal.

5. The output feedback circuit according to claim 1, characterized in that: The compensation circuit includes: a first voltage-dividing circuit coupled to the output terminal and providing a first voltage at a first voltage-dividing node according to a change in the output voltage; and an operational amplifier comprising a positive input terminal, a negative input terminal and an operational amplifier output terminal, the negative input terminal being coupled to the first voltage-dividing node and the operational amplifier output terminal, and the operational amplifier output terminal being coupled to the feedback circuit to adjust the first reference voltage of the operational amplifier output terminal according to a change in the first voltage; The reference standard is a value of the first reference voltage, and the first reference voltage is inversely proportional to the first voltage.

6. The output feedback circuit according to claim 1, characterized in that: The feedback circuit includes: a second voltage-dividing circuit, providing a second voltage at a second voltage-dividing node according to the first reference voltage; and a comparator, receiving the second voltage and the current detection signal, to provide a comparison signal according to the second voltage and the current detection signal; The feedback circuit provides the feedback signal according to the comparison signal.

7. The output feedback circuit according to claim 5, characterized in that: The compensation circuit further comprises: A third voltage-dividing circuit is coupled to the positive input terminal and provides a third voltage at a third voltage-dividing node according to a second reference voltage; The operational amplifier adjusts the first reference voltage according to the change of the voltage difference between the first voltage and the third voltage.

8. The output feedback circuit according to claim 1, characterized in that: The compensation circuit includes: A first voltage dividing circuit is coupled to the output terminal and provides a first voltage at a first voltage dividing node according to a change in the output voltage; An operational amplifier, comprising a positive input terminal, a negative input terminal and an operational amplifier output terminal, wherein the positive input terminal is coupled to the first voltage dividing node, and the operational amplifier output terminal is coupled to the feedback circuit; and A third voltage divider circuit is coupled to the negative input terminal and the operational amplifier output terminal, and adjusts the voltage of the operational amplifier output terminal according to the variation of the first voltage; The reference standard is the value of the voltage, and the voltage is proportional to the first voltage.

9. The output feedback circuit according to claim 8, characterized in that: The feedback circuit includes: A second voltage dividing circuit provides a second voltage at a second voltage dividing node according to the first reference voltage; a fourth voltage-dividing circuit, providing a sampling voltage at a fourth voltage-dividing node according to the current detection signal and the voltage; and a comparator, receiving the second voltage and the sampling voltage, to provide a comparison signal according to the second voltage and the sampling voltage; The feedback circuit provides the feedback signal according to the comparison signal.

10. A method for operating an output feedback circuit, characterized in that: The output feedback circuit is used to provide a feedback signal to the conversion circuit, so that the conversion circuit balances the output power at different output voltages according to the feedback signal. The operation method includes the following steps: receiving a current detection signal corresponding to an output current of the conversion circuit; Providing a reference benchmark according to the magnitude of the output voltage to compensate the current detection signal or the first reference voltage; The current detection signal is sampled under compensation of a reference standard to provide the feedback signal.

11. The operating method according to claim 10, characterized in that: The following steps are also included: Providing a first voltage accordingly according to the change of the output voltage; adjusting the current flowing through the transistor according to the variation of the first voltage; Providing a second voltage correspondingly according to the first reference voltage, and changing the second voltage by adjusting the current; and Providing a comparison signal according to the second voltage and the current detection signal, and providing the feedback signal according to the comparison signal; The reference standard is the value of the current, and the current is inversely proportional to the first voltage.

12. The operating method according to claim 10, characterized in that: The following steps are also included: Providing a first voltage accordingly according to the change of the output voltage; Adjusting a current flowing through the transistor according to the variation of the first voltage; Providing a second voltage correspondingly according to the first reference voltage, and adjusting the current detection signal to a sampling voltage through the current; and Providing a comparison signal according to the sampled voltage and the second voltage, so as to provide the feedback signal according to the comparison signal; The reference standard is the value of the current, and the current is inversely proportional to the first voltage.

13. The operating method according to claim 10, characterized in that: The following steps are also included: Providing a first voltage accordingly according to the change of the output voltage; The first reference voltage at the output terminal of the operational amplifier is adjusted according to the second reference voltage and the changed first voltage; and a second voltage is provided in response to the change of the first reference voltage; and a comparison signal is provided according to the second voltage and the current detection signal, so as to provide the feedback signal according to the comparison signal; The reference standard is a value of the first reference voltage, and the first reference voltage is inversely proportional to the first voltage.

14. The operating method according to claim 10, characterized in that: The following steps are also included: Providing a first voltage accordingly according to the change of the output voltage; adjusting a voltage of an output terminal of an operational amplifier according to the variation of the first voltage, and providing a sampling voltage corresponding to the varied voltage according to the current detection signal; and Providing a second voltage accordingly according to the first reference voltage; and Providing a comparison signal according to the sampled voltage and the second voltage, and providing the feedback signal according to the comparison signal; The reference standard is the value of the voltage, and the voltage is proportional to the first voltage.

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