Power conversion circuit

Abstract

The invention discloses a power conversion circuit. The power conversion circuit comprises a control circuit, the control circuit comprises a reference signal generating circuit, a comparator, an on-time control circuit and a driving circuit. The reference signal generating circuit is used for compensating the first reference voltage and generating a corrected reference voltage. The reference signal generating circuit comprises an operational amplifier circuit, a compensation capacitor and a compensation branch circuit. The operational amplifier circuit receives the first reference voltage and generates a corrected reference voltage according to the first reference voltage. The comparator outputs a comparison signal according to a signal related to the first output voltage and a signal related to the correction reference voltage. The turn-on time control circuit generates a turn-on time control signal according to the comparison signal. The drive circuit generates a drive control signal according to the turn-on time control signal to control the operation of a main switch of the power conversion circuit.

Description

Technical Field

[0001] The present invention relates to a power conversion circuit, and more particularly to a power conversion circuit capable of improving system stability and output voltage accuracy. Background Art

[0002] With the development of technology, the types of electronic products are increasing day by day, such as laptops, mobile communication devices, mobile communication devices, etc. These electronic products all need to use power conversion circuits to convert high-voltage AC power or DC power into a low-voltage and stable DC power that meets the requirements as a power source for normal operation. Please refer to Figure 1 , Figure 1 The schematic diagram of a conventional power conversion circuit 1 with ripple-based constant on-time control (RBCOT) is shown. The power conversion circuit 1 with ripple-based constant on-time control can provide a fast transient response control method. The power conversion circuit 1 includes a comparator 12, an on-time control circuit 14, a drive circuit 16, a main switch UG, an inductor L, and an output capacitor C. O The comparator 12 compares the first output voltage V O The voltage V FB With the first reference voltage V REF When the voltage V FB Less than the first reference voltage V REF When the comparator 12 generates a comparison signal TON_SHOT to trigger the on-time control circuit 14, the on-time control circuit 14 generates an on-time control signal S with a high level pulse. TON To the driving circuit 16. The driving circuit 16 controls the on-time signal S TON The main switch UG is controlled to perform a switching operation to convert an input voltage V I Converted to the first output voltage V O , and supplies a load current I LOAD to a load.

[0003] However, due to the inductor current I of the power conversion circuit 1 L With the first output voltage V O The phase difference is 90 degrees. Once the output capacitor C O The equivalent series resistance ESR is too small, for example, a multilayer ceramic capacitor is used to realize the output capacitor C O , the ripple voltage generated by the equivalent series resistance ESR is relatively small, so it will produce subharmonic oscillation or continuous hitting phenomenon and cause unstable operation of the power conversion circuit. Generally speaking, according to the stability conditions of the power conversion circuit, the output capacitor C O The product of the equivalent series resistance ESR must be greater than the on-time TON That is, when the output capacitor C O The product of the equivalent series resistance ESR is greater than the on-time T ON When the power conversion circuit reaches half of the original value, the power conversion circuit begins to stabilize. The stability condition of the power conversion circuit 1 controlled by ripple constant conduction time can be expressed by the following formula.

[0004]

[0005] Where ESR is the output capacitance C O The equivalent series resistance, C O is the output capacitance, T ON is the on-time control signal S TON The on-time of

[0006] For example, see Figure 2 , Figure 2 for Figure 1 Schematic diagram of the operation waveform of the power conversion circuit 1. Figure 2 As shown, when the output capacitor C O When the equivalent series resistance ESR is too small to meet the above stability conditions, the inductor current I L The peak value of the first output voltage V O The peak phase difference is 90 degrees, and during the conduction time T ON During this period, subharmonic oscillation and continuous beating phenomena are generated, thereby causing the system operation of the power conversion circuit 1 to be unstable.

[0007] On the other hand, during the ripple constant on-time control operation, the comparator 102 of the power conversion circuit 1 compares the first output voltage V O The voltage V FB With the first reference voltage V REF This negative feedback control mechanism is based on the voltage V FB (The first output voltage V O ) is less than the first reference voltage V REF To control the power conversion circuit 1 to switch operation. For example, please refer to Figure 3 , Figure 3 for Figure 1 Another operation waveform diagram of the power conversion circuit 1 is shown in FIG. Figure 3 As shown, the conduction time T ON The period starts at the voltage V FB (The first output voltage V O ) reaches the valley value and is triggered by the control. In this way, this negative feedback control mechanism can only reach the voltage V FB (The first output voltage V O ) is equal to the first reference voltage VREF When the first output voltage V O The larger the ripple, the higher the first output voltage V O will be related to the first reference voltage V REF The larger the difference, the more inaccurate the output voltage will be. Therefore, there is room for improvement in the prior art. Summary of the invention

[0008] In order to solve the above problems, the present invention provides a power conversion circuit which can improve system stability and output voltage accuracy to solve the above problems.

[0009] The present invention provides a power conversion circuit, wherein the power conversion circuit includes a power supply, a main switch, an inductor, an output capacitor and a control circuit electrically connected in sequence, and the control circuit includes: a reference signal generating circuit, used to compensate a first reference voltage and generate a modified reference voltage, including: an operational amplifier circuit, including a common-phase input terminal, used to receive the first reference voltage, an inverting input terminal, and an output terminal, coupled to the inverting input terminal of the operational amplifier circuit, used to generate the modified reference voltage; a compensation capacitor, coupled between the output terminal of the operational amplifier circuit and a ground terminal; and a compensation branch circuit, coupled between the output terminal of the operational amplifier circuit and the ground terminal. terminals, and includes an auxiliary switch and a current source connected in series; a comparator, including a first input terminal, coupled to the output capacitor, for receiving a signal related to a first output voltage of the power conversion circuit, a second input terminal, coupled to the reference signal generating circuit, for receiving a signal related to the corrected reference voltage, and an output terminal, for outputting a comparison signal; a conduction time control circuit, coupled to the output terminal of the comparator, for generating a conduction time control signal according to the comparison signal; and a driving circuit, coupled to the conduction time control circuit, for generating a driving control signal according to the conduction time control signal to control the operation of the main switch of the power conversion circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0010] Figure 1 A schematic diagram of a conventional power conversion circuit with ripple-type constant on-time control.

[0011] Figure 2 and Figure 3 for Figure 1 Schematic diagram of the operating waveform of the power conversion circuit.

[0012] Figure 4 FIG. 4 is a schematic diagram of a power conversion circuit according to the first embodiment of the present invention.

[0013] Figure 5 for Figure 4 Schematic diagram of the operating waveform of the power conversion circuit.

[0014] Figure 6 for Figure 4 A schematic diagram of a variation of an embodiment of a current source in a reference signal generating circuit.

[0015] Figure 7 for Figure 4 Schematic diagram of another variation of an embodiment of a current source in a reference signal generating circuit.

[0016] Figure 8 for Figure 4 A schematic diagram of another variation of an embodiment of a current source in a reference signal generating circuit.

[0017] Fig. 9 for Figure 4 A schematic diagram of a variation of a power conversion circuit.

[0018] Fig.10 FIG. 4 is a schematic diagram of a power conversion circuit according to a second embodiment of the present invention.

[0019] Fig.11 FIG. 4 is a schematic diagram of a power conversion circuit according to a third embodiment of the present invention.

[0020] Fig.12 FIG. 4 is a schematic diagram of a power conversion circuit according to a fourth embodiment of the present invention.

[0021] Fig.13 FIG. 4 is a schematic diagram of a power conversion circuit according to a fifth embodiment of the present invention.

[0022] Fig.14 FIG. 4 is a schematic diagram of a power conversion circuit according to a sixth embodiment of the present invention.

[0023] The reference numerals are described as follows:

[0024] 1, 4, 100, 110, 120, 130, 140: Power conversion circuit

[0025] 1006, 1106, 1406: Voltage gain circuit

[0026] 1008, 1108, 1308, 1408: Addition circuit

[0027] 12, 46: Comparator

[0028] 14, 48: On-time control circuit

[0029] 16,50: Driving circuit

[0030] 40: Control circuit

[0031] 42: Reference signal generation circuit

[0032] 422: Operational amplifier circuit

[0033] 424: Compensation branch circuit

[0034] 426: Current Source

[0035] 44, 1002, 1102, 1202, 1302, 1402: offset control circuit

[0036] 442, 1004, 1104, 1204, 1304, 1404: Error amplifier

[0037] 602, 802: Controlled current source

[0038] 604, 804: Voltage to current control circuit

[0039] 902: Voltage divider circuit

[0040] C O : Output capacitor

[0041] C RP : Compensation capacitor

[0042] DCR: DC resistance

[0043] ESR: Equivalent Series Resistance

[0044] L: Inductance

[0045] I L : Inductor current

[0046] I LOAD : Load current

[0047] PS: Power supply

[0048] R, R1, R2: resistors

[0049] S TON : On-time control signal

[0050] SW: Auxiliary switch

[0051] T ON : On time

[0052] TON_SHOT: comparison signal

[0053] UG: Main switch

[0054] V C : Error signal

[0055] V FB :Voltage

[0056] V I: Input voltage

[0057] V O : First output voltage

[0058] V O ': Second output voltage

[0059] V off_c : Offset compensation signal

[0060] V REF : First reference voltage

[0061] V REF ': Second reference voltage

[0062] V RP : Corrected reference voltage

[0063] V RP ': First correction reference voltage DETAILED DESCRIPTION

[0064] The terms "include", "including", "have", etc. used in the present invention are open-ended terms, meaning including but not limited to. In addition, the terms "coupled" or "connected" used in the present invention may refer to two or more elements making direct physical or electrical contact, or making indirect physical or electrical contact with each other.

[0065] Please refer to Figure 4 , Figure 4 FIG. 4 is a schematic diagram of a power conversion circuit 4 according to a first embodiment of the present invention. The power conversion circuit 4 can be used to convert an input voltage V I Converted into a first output voltage V O , and supplies a load current I LOAD To a load. The power conversion circuit includes but is not limited to a step-down circuit. The load can be any electronic device that requires power. The power conversion circuit 4 includes a power supply PS, a main switch UG, an inductor L, a DC resistor DCR, an equivalent series resistor ESR, an output capacitor C, which are electrically connected in sequence. O and a control circuit 40. The control circuit 40 includes a reference signal generating circuit 42, an offset control circuit 44, a comparator 46, an on-time control circuit 48 and a driving circuit 50. The reference signal generating circuit 42 can generate a first reference voltage V REF Compensation is performed and a corrected reference voltage V is generated RP The comparator 46 can receive and compare the modified reference voltage V generated by the reference signal generating circuit 42. RP The first output voltage V of the power conversion circuit 4 OThe related signal is used to generate a comparison signal TON_SHOT to trigger the on-time control circuit 48, so that the on-time control circuit 48 generates a high-level pulse (on-time T ON ) of the on-time control signal S TON To the driving circuit 50. The driving circuit 50 controls the on-time according to the signal S TON The main switch UG is controlled to perform a switching operation. When the comparison signal TON_SHOT is a rising edge, the control circuit 40 controls the main switch UG to be turned on, so that the inductor L draws power from the power source PS and outputs power to the load, so as to increase the input voltage V I Converted to the first output voltage V O .

[0066] The reference signal generating circuit 42 can generate a first reference voltage V REF Compensation is performed and a corrected reference voltage V is generated RP The reference signal generating circuit 42 includes an operational amplifier circuit 422, a compensation capacitor C RP and a compensation branch circuit 424. A common-phase input terminal of the operational amplifier circuit 422 is used to receive a first reference voltage V REF The first reference voltage V REF It can be generated by a voltage generator or a bandgap reference voltage circuit (not shown in the figure). The first reference voltage V REF can be a fixed value, and the first reference voltage V REF The setting can be made according to actual needs. An inverting input terminal of the operational amplifier circuit 422 is coupled to the output terminal of the operational amplifier circuit 422. The output terminal of the operational amplifier circuit 422 is used to generate a modified reference voltage V RP For example, the operational amplifier circuit 422 may be an operational transconductance amplifier, but is not limited thereto. The compensation capacitor C RP The operational amplifier circuit 422 and the compensation capacitor C are coupled between the output terminal of the operational amplifier circuit 422 and a ground terminal. RP A unit gain buffer can be formed to buffer the first reference voltage V received by the non-inverting input terminal of the operational amplifier circuit 422. REF And output the corrected reference voltage V RP .

[0067] Furthermore, the compensation branch circuit 424 is coupled between the output terminal of the operational amplifier circuit 422 and the ground terminal. The compensation branch circuit 424 includes an auxiliary switch SW and a current source 426 connected in series. The auxiliary switch SW is controlled by the on-time control signal S generated by the on-time control circuit 48. TON For example, during the on-time control signal S TON The on time T ONDuring this period, the auxiliary switch SW is controlled according to the on-time control signal S TON For example, the auxiliary switch SW can be a metal-oxide-semiconductor field-effect transistor (MOSFET), a bipolar junction transistor (BJT) or other components with similar functions, but not limited thereto. The current source 426 is used to generate a first current I DCHG , so that when the auxiliary switch SW is turned on, the first current I DCHG For compensation capacitor C RP Discharge and adjust the reference voltage V RP For example, the current source 426 may be a fixed current source, but is not limited thereto. In other words, the compensation branch circuit 424 is controlled by the on-time control signal S TON The compensation capacitor C RP Discharge.

[0068] Please continue to refer to Figure 4 and Figure 5 , Figure 5 for Figure 4 Schematic diagram of the relevant operation waveform of the power conversion circuit 4. TON The on time T ON During this period, the auxiliary switch SW is controlled according to the on-time control signal S TON When switched to the on state, the first current I DCHG Flowing through the compensation capacitor C RP , the auxiliary switch SW and the current source 426 to form a discharge path to compensate the capacitor C RP Discharge is performed to correct the reference voltage V RP And, the auxiliary switch SW is controlled according to the conduction time control signal S TON In the off state, the compensation capacitor C RP Charge to correct the reference voltage V RP Rise. Figure 5 As shown, the reference voltage V is corrected when the system is running. RP Gradually rises, and, during the on time T ON During the period based on the compensation capacitor C RP The current source 426 discharges the modified reference voltage V RP In other words, the reference voltage V RP The waveform is equivalent to the reverse phase inductor current I L The modified reference voltage V generated by the embodiment of the present invention is RPEquivalent to the conventional first reference voltage V REF and the inductor current I L The subtracted value can reduce the first output voltage V of the power conversion circuit 4. O and the inductor current I L The phase difference between them reduces the output capacitance C O The influence of the equivalent series resistance (ESR) can effectively improve the system stability.

[0069] Please continue to refer to Figure 4 The offset control circuit 44 includes an error amplifier 442. A first input terminal (eg, an inverting input terminal) of the error amplifier 442 receives a first output voltage V O For example, Figure 4 As shown, the first input terminal of the error amplifier 442 receives the first output voltage V O A second input terminal (eg, a non-inverting input terminal) of the error amplifier 442 receives a first reference voltage V REF An output terminal of the error amplifier 442 is coupled to a control signal terminal of the operational amplifier circuit 422. The error amplifier 442 generates a first output voltage V O and the first reference voltage V REF Generate an error signal V C To the control signal terminal of the operational amplifier circuit 422. The error amplifier 442 can be an amplifier circuit with a high gain (for example, greater than 60 decibels (dB)), and can amplify the slight difference between the signals into a larger signal. When the system is running, the error amplifier 442 performs error accumulation and continuously accumulates the signals at the two input terminals (the first output voltage V O and the first reference voltage V REF ) to generate the error signal V C Among them, the error signal V C The corrected reference voltage V output by the operational amplifier circuit 422 is RP is based on the first reference voltage V REF and an offset voltage V of the operational amplifier circuit 422 off The offset voltage V of the operational amplifier circuit 422 is determined by off Based on the first output voltage V O and the first reference voltage V REF The error signal V C The offset voltage V off and error signal V c The relationship can be expressed as follows.

[0070]

[0071] Among them, V off represents the offset voltage, V C represents an error signal, and K represents a gain voltage value.

[0072] Please continue to refer to Figure 4 , when the power conversion circuit 4 is running, when the first output voltage V O Less than the first reference voltage V REF When the error amplifier 442 generates an error signal V C The level of the error signal V C rises, the offset voltage V off Also increases, thus making the corrected reference voltage V RP In this case, the comparator 46 corrects the reference voltage V RP The comparison signal TON_SHOT is generated to control the on-time control circuit 48 to generate a high level pulse (on-time T ON ) of the on-time control signal S TON To drive the main switch to operate, so that the first output voltage V O Thus, through the control of the offset control circuit 44, the first output voltage V O and the first reference voltage V REF will eventually be very close to or equal to each other. That is, the first output voltage V O The average value will be very close to or equal to the first reference voltage V REF , thus effectively improving the output voltage accuracy.

[0073] Please continue to refer to Figure 4 A first input terminal (eg, an inverting input terminal) of the comparator 46 is coupled to the output capacitor C O , for receiving the first output voltage V that can reflect the power conversion circuit 4 O For example, Figure 4 As shown, the first input terminal of the comparator 46 receives the first output voltage V O A second input terminal (eg, the non-inverting input terminal) of the comparator 46 is coupled to the reference signal generating circuit 42 to receive the modified reference voltage V RP An output terminal of the comparator 46 is used to output a comparison signal TON_SHOT. The comparator 46 compares the first output voltage V O With the corrected reference voltage V RP The on-time control circuit 48 is coupled to the output terminal of the comparator 46 and is used to generate an on-time control signal S according to the comparison signal TON_SHOT. TONThe driving circuit 50 is coupled to the on-time control circuit 48 and is used to control the on-time control signal S TON A driving control signal is generated to control the main switch UG of the power conversion circuit 4 to perform a switching operation. When the comparison signal TON_SHOT is a rising edge, the control circuit 40 controls the main switch UG to turn on, so that the inductor L draws power from the external power supply and outputs power to the load, so as to increase the input voltage V I Converted to the first output voltage V O For example, at the first output voltage V O Less than the corrected reference voltage V RP When the comparator 102 generates a comparison signal TON_SHOT to trigger the on-time control circuit 48, the on-time control circuit 48 generates a high level pulse (on-time T ON ) of the on-time control signal S TON To the driving circuit 50, the driving circuit 50 generates a driving control signal to control the main switch UG of the power conversion circuit 4 to turn on. That is, when the first output voltage V O Less than the corrected reference voltage V RP When the control circuit 40 controls the main switch UG to turn on, the power supply PS transfers energy to the output capacitor C O And the first output voltage V O In addition, the on-time control signal S generated by the on-time control circuit 48 TON The operation of the main switch UG can be controlled to adjust the first output voltage V O The auxiliary switch SW of the compensation branch circuit 424 is also controlled by the on-time control signal S TON The compensation capacitor C RP Discharge to adjust the reference voltage V RP The level.

[0074] In other words, the embodiment of the present invention can generate a modified reference voltage V by the reference signal generating circuit 42. RP To reduce the first output voltage V of the power conversion circuit 4 O and the inductor current I L The phase difference between them can improve the system stability. And, through the control of the offset control circuit 44, the first output voltage V O The average value is very close to or equal to the first reference voltage V REF This can effectively improve the output voltage accuracy.

[0075] In one embodiment, please refer to Figure 6 , Figure 6 for Figure 4The current source 426 of the reference signal generating circuit 42 is used to generate a first current I DCHG , so that when the auxiliary switch SW is turned on, the first current I DCHG For compensation capacitor C RP Discharge to adjust the reference voltage V RP The level of Figure 6 As shown, the current source 426 includes a controlled current source 602 and a voltage-to-current control circuit 604. The controlled current source 602 and the auxiliary switch SW are connected in series. The voltage-to-current control circuit 604 is coupled to the controlled current source 602 and is used to control the controlled current source 602 to output a first current I according to a voltage Vx. DCHG That is, the first current I output by the current source 426 is DCHG Controlled by the voltage Vx, if the transconductance gain of the voltage-to-current control circuit 604 is gm_DCHG, the on-time control signal S TON The conduction time is T ON , the first current I DCHG The current value is equal to the product of the voltage value of the voltage Vx and the transconductance gain gm_DCHG of the voltage-to-current control circuit 604 (ie, I DCHG =Vx*gm_DCHG). In this case, the reference voltage V RP The amplitude A can be expressed as follows.

[0076]

[0077] According to formula (3), the embodiment of the present invention can set the voltage Vx according to the system requirements to adjust the modified reference voltage V RP For example, the voltage Vx can be set to the input voltage V according to system requirements. I , the first output voltage V O , the first reference voltage V REF Or any other voltage value to adjust the reference voltage V RP For example, the voltage Vx can be set according to the duty cycle state requirements of the power conversion circuit to adjust the modified reference voltage V RP The amplitude of the vibration.

[0078] In one embodiment, please refer to Figure 7 , Figure 7 for Figure 4 Schematic diagram of another variation of the current source 426. Figure 7 As shown, the current source 426 includes a resistor R. When the auxiliary switch SW is turned on, the first current I DCHG Flowing through the compensation capacitor C RP, auxiliary switch SW and resistor R to form a discharge path to compensate capacitor C RP Discharge, and then adjust the reference voltage V RP In one embodiment, please refer to Figure 8 , Figure 8 for Figure 4 A schematic diagram of another variation of the current source 426 is shown. Figure 8 As shown, the current source 426 includes a resistor R, a controlled current source 802, and a voltage-to-current control circuit 804. The resistor R and the auxiliary switch SW are connected in series, and the controlled current source 802 is connected in parallel to the resistor R. The voltage-to-current control circuit 804 is coupled to the controlled current source 802 and is used to control the controlled current source 802 to generate a second current according to a voltage Vx, so that the current source 426 outputs the first current I DCHG , and then when the auxiliary switch SW is turned on, the first current I DCHG For compensation capacitor C RP Discharge to adjust the reference voltage V RP The level.

[0079] Since the first input terminal of the comparator 46 and the first input terminal of the error amplifier 442 receive the first output voltage V O The first input terminal of the comparator 46 and the first input terminal of the error amplifier 442 can receive any voltage signal that is different from the first output voltage V O For example, please refer to Fig. 9 , Fig. 9 for Figure 4 A schematic diagram of a variation of the power conversion circuit 4. Fig. 9 As shown, the power conversion circuit 4 further includes a voltage divider circuit 902, which is used to divide the first output voltage V O Divide the voltage to provide a voltage V FB To comparator 46. Fig. 9 As shown, the voltage divider circuit 902 is connected in parallel to the output capacitor C O The voltage divider circuit 902 includes a resistor R1 and a resistor R2 connected in series, wherein the resistance values ​​of the resistors R1 and R2 can be set according to actual needs. The first input terminal of the comparator 46 is coupled to the common node FB between the resistors R1 and R2 to receive the first output voltage V O A voltage V FB . Similarly, Fig. 9 As shown, the first input terminal of the error amplifier 442 can also be coupled to a voltage that can reflect the first output voltage V O The voltage V FB , for related operations.

[0080] Please refer to Fig.10 , Fig.10 FIG. 1 is a schematic diagram of a power conversion circuit 100 according to a second embodiment of the present invention. It is worth noting that due to Fig.10 The power conversion circuit 100 and Figure 4 The components with the same name in the power conversion circuit 4 have similar operation modes and functions. Therefore, for the sake of brevity of the description, detailed descriptions are omitted here. The connection relationship of these components is as follows: Fig.10 Compared with Figure 4 The power conversion circuit 4 in the control circuit 40 further includes an offset control circuit 1002. The offset control circuit 1002 includes an error amplifier 1004, a voltage gain circuit 1006, and an adder circuit 1008. The error amplifier 1004 can be an amplifier circuit with a high gain. A first input terminal (e.g., an inverting input terminal) of the error amplifier 1004 receives a first output voltage V O For example, Fig.10 As shown, the first input terminal of the error amplifier 1004 receives the first output voltage V O A second input terminal (eg, the non-inverting input terminal) of the error amplifier 1004 receives a second reference voltage V REF An output terminal of the error amplifier 1004 is coupled to the voltage gain circuit 1006. The error amplifier 1004 generates a voltage gain according to the first output voltage V O and the second reference voltage V REF 'Generate an error signal V C The voltage gain circuit 1006 is coupled to the error amplifier 1004 to generate a voltage gain of the error signal V C A gain process is performed to generate an offset compensation signal V off_c . The offset compensation signal V off_c According to the error signal V C For example, the offset compensation signal V off_c Can be the error signal V C The adding circuit 1008 is coupled to the voltage gain circuit 1006 and the non-inverting input terminal of the operational amplifier circuit 422 to convert the offset compensation signal V off_c and the second reference voltage V REF 'Added together to generate a first reference voltage V REF To the non-inverting input terminal of the operational amplifier circuit 422. The reference signal generating circuit 42 can generate the first reference voltage V REF Compensation is performed to generate a corrected reference voltage V RP For example, the operational amplifier circuit 422 of the reference signal generating circuit 42 and the compensation capacitor C RPA unity gain buffer may be formed to buffer the first reference voltage V received by the non-inverting input terminal of the operational amplifier circuit 422. REF And output correction reference voltage V RP Therefore, when the power conversion circuit 100 is running, when the first output voltage V O is less than the second reference voltage V REF ', the error signal V generated by the error amplifier 1004 C When the error signal V C rises, the offset compensation signal V off_c Increase the reference voltage V RP In this case, the main switch UG is turned on through the control of the comparator 46, the on-time control circuit 48 and the drive circuit 50, so that energy is transferred to the output capacitor C O , the first output voltage V O Thus, through the control of the offset control circuit 1002, the first output voltage V O The average value will be very close to or equal to the second reference voltage V REF ', thus effectively improving the output voltage accuracy. The second reference voltage V REF ' can be a fixed value, and the second reference voltage V REF 'It can be set according to actual needs.

[0081] Please refer to Fig.11 , Fig.11 FIG. 1 is a schematic diagram of a power conversion circuit 110 according to a third embodiment of the present invention. It is worth noting that Fig.11 The power conversion circuit 110, Fig.10 The power conversion circuit 100 and Figure 4 The components with the same name in the power conversion circuit 4 have similar operation modes and functions. Therefore, for the sake of brevity of the description, detailed descriptions are omitted here. The connection relationship of these components is as follows: Fig.11 Compared with Figure 4 The power conversion circuit 4 and Fig.10 The power conversion circuit 100, the control circuit 40 further includes an offset control circuit 1102. The offset control circuit 1102 includes an error amplifier 1104, a voltage gain circuit 1106 and an adding circuit 1108. Fig.10 The error amplifier 1004 and the voltage gain circuit 1106 are configured such that the error amplifier 1104 can be an amplifier circuit with a high gain. The error amplifier 1104 can reflect the first output voltage V of the power conversion circuit. O The voltage signal and the first reference voltage V REF Generate an error signal VC To the voltage gain circuit 1106. The voltage gain circuit 1106 is used to adjust the error signal V C A gain process is performed to generate an offset compensation signal V off_c . The offset compensation signal V off_c According to the error signal V C For example, the offset compensation signal V off_c Can be the error signal V C The adding circuit 1108 is coupled to the voltage gain circuit 1106 and the inverting input terminal of the operational amplifier circuit 422. In this way, the operational amplifier circuit 422 can generate a voltage signal according to the first reference voltage V REF And the offset compensation signal V off_c To generate a corrected reference voltage V RP Therefore, through the control of the offset control circuit 1102, the first output voltage V O The average value will be very close to or equal to the first reference voltage V REF , which can effectively improve the output voltage accuracy.

[0082] Please refer to Fig.12 , Fig.12 FIG. 1 is a schematic diagram of a power conversion circuit 120 according to a fourth embodiment of the present invention. It is worth noting that due to Fig.12 The power conversion circuit 120 and Figure 4 The components with the same name in the power conversion circuit 4 have similar operation modes and functions. Therefore, for the sake of brevity of the description, detailed descriptions are omitted here. The connection relationship of these components is as follows: Fig.12 Compared with Figure 4 In the power conversion circuit 4, the control circuit 40 further includes an offset control circuit 1202. The offset control circuit 1202 includes an error amplifier 1204. Figure 4 The error amplifier 442 of the embodiment of the present invention can be an amplifier circuit with a high gain. The error amplifier 1204 can be based on the first output voltage V O and the first reference voltage V REF Generate an error signal V C The comparator 46 can control the offset voltage of the comparator 46 according to the error signal V C , Corrected reference voltage V RP And the first output voltage V O Generate a comparison signal TON_SHOT. The comparison signal TON_SHOT is based on the modified reference voltage V RP And the first output voltage V O and an offset voltage V of the comparator 46 off1 The offset voltage V of the comparator 46 is determined byoff1 Based on the first output voltage V O and the first reference voltage V REF The error signal V C For example, the offset voltage V off1 Can be the error signal V C The product of the first output voltage V O Less than the corrected reference voltage V RP With the offset voltage V off1 When the sum of the comparison signal TON_SHOT and the on-time control circuit 48 is equal to 1, the comparator 46 outputs a high-level comparison signal TON_SHOT to trigger the on-time control circuit 48, so that the on-time control circuit 48 generates a high-level pulse (on-time T ON ) of the on-time control signal S TON to the driving circuit 50, thereby controlling the main switch UG to turn on so that the power supply PS transfers energy to the output capacitor C O , the first output voltage V O Therefore, through the control of the offset control circuit 1202, the first output voltage V O The average value will be very close to or equal to the first reference voltage V REF This can effectively improve the output voltage accuracy.

[0083] Please refer to Fig.13 , Fig.13 FIG. 1 is a schematic diagram of a power conversion circuit 130 according to the fifth embodiment of the present invention. It is worth noting that Fig.13 The power conversion circuit 130 and Figure 4 The components with the same name in the power conversion circuit 4 have similar operation modes and functions. Therefore, for the sake of brevity of the description, detailed descriptions are omitted here. The connection relationship of these components is as follows: Fig.13 Compared with Figure 4 In the power conversion circuit 4, the control circuit 40 further includes an offset control circuit 1302. The offset control circuit 1302 includes an error amplifier 1304, a voltage gain circuit 1306 and an adding circuit 1308. Fig.10 The error amplifier 1004 and the voltage gain circuit 1106 are configured such that the error amplifier 1304 can be an amplifier circuit with a high gain. The error amplifier 1304 can reflect the first output voltage V of the power conversion circuit. O The voltage signal and the first reference voltage V REF Generate an error signal V C To the voltage gain circuit 1306. The voltage gain circuit 1306 is used to adjust the error signal V C A gain process is performed to generate an offset compensation signal V off_c. The offset compensation signal V off_c According to the error signal V C For example, the offset compensation signal V off_c Can be the error signal V C The adding circuit 1308 is coupled to the voltage gain circuit 1306 and the output terminal of the operational amplifier circuit 422 to convert the offset compensation signal V off_c The corrected reference voltage V output by the operational amplifier circuit 422 RP The voltage V RP ' to the second input terminal (eg, the non-inverting input terminal) of the comparator 46. The comparator 46 compares the first output voltage V O With the first correction reference voltage V RP ' and generates a comparison signal TON_SHOT accordingly. When the power conversion circuit 130 is running, when the first output voltage V O Less than the first reference voltage V REF When the error amplifier 1304 generates an error signal V C The level of the offset compensation signal V off_c Increase, so that the first correction reference voltage V RP In this case, the main switch UG is turned on through the control of the comparator 46, the on-time control circuit 48 and the drive circuit 50, so that energy is transferred to the output capacitor C O , the first output voltage V O Thus, through the control of the offset control circuit 1302, the first output voltage V O The average value will be very close to or equal to the first reference voltage V REF , thus effectively improving the output voltage accuracy.

[0084] Please refer to Fig.14 , Fig.14 FIG. 1 is a schematic diagram of a power conversion circuit 140 according to a sixth embodiment of the present invention. It is worth noting that Fig.14 The power conversion circuit 140 and Figure 4 The components with the same name in the power conversion circuit 4 have similar operation modes and functions. Therefore, for the sake of brevity of the description, detailed descriptions are omitted here. The connection relationship of these components is as follows: Fig.14 Compared with Figure 4 In the power conversion circuit 4, the control circuit 40 further includes an offset control circuit 1402. The offset control circuit 1402 includes an error amplifier 1404, a voltage gain circuit 1406 and an adding circuit 1408. Fig.10The error amplifier 1004 and the voltage gain circuit 1106 are configured such that the error amplifier 1404 can be an amplifier circuit with a high gain. The error amplifier 1404 can be configured such that the first output voltage V O and the first reference voltage V REF Generate an error signal V C To the voltage gain circuit 1406. The voltage gain circuit 1406 is used to adjust the error signal V C A gain process is performed to generate an offset compensation signal V off_c The adding circuit 1408 is coupled to the output capacitor C O , the voltage gain circuit 1406 and a first input terminal (eg, the inverting input terminal) of the comparator 46. The adding circuit 1408 can convert the offset compensation signal V off_c With the first output voltage V O The second output voltage V O ' to the first input terminal of the comparator 46. The comparator 46 compares the second output voltage V O 'With the corrected reference voltage V RP The comparison signal TON_SHOT is generated accordingly. When the power conversion circuit 140 is running, when the first output voltage V O Less than the first reference voltage V REF The error signal V generated by the error amplifier 1404 is C The level of the offset compensation signal V off_c increases, so that the second output voltage V O In this case, the main switch UG is turned on through the control of the comparator 46, the on-time control circuit 48 and the drive circuit 50, so that energy is transferred to the output capacitor C O , the first output voltage V O Thus, through the control of the offset control circuit 1402, the first output voltage V O The average value will be very close to or equal to the first reference voltage V REF , thus effectively improving the output voltage accuracy.

[0085] On the other hand, since the first input terminal of the comparator 46 and the first input terminals of the error amplifiers 1004, 1104, 1204, 1304 and 1404 receive signals that reflect the first output voltage V O That is, the first input terminal of the comparator 46 and the first input terminals of the error amplifiers 1004, 1104, 1204, 1304 and 1404 can receive any voltage signal that is different from the first output voltage V O In this case, similar to Fig. 9The first input terminals of the error amplifiers 1004, 1104, 1204, 1304 and 1404 may also be coupled to the first output voltage V O A voltage divider circuit is configured to receive a first output voltage V O A divided voltage is used to perform related operations.

[0086] In summary, the embodiment of the present invention generates a corrected reference voltage through a reference signal generating circuit to reduce the phase difference between the output voltage of the power conversion circuit and the inductor current, thereby effectively improving the system stability. In addition, the embodiment of the present invention can make the average value of the output voltage very close to or equal to the reference voltage through the control of the offset control circuit, thereby greatly improving the output voltage accuracy.

[0087] The above description is only a preferred embodiment of the present invention. All equivalent changes and modifications made according to the claims of the present invention should fall within the scope of the present invention.

Claims

1. A power conversion circuit, wherein the power conversion circuit comprises a power supply, a main switch, an inductor, an output capacitor and a control circuit electrically connected in sequence, the control circuit comprising: A reference signal generating circuit, used for compensating a first reference voltage and generating a modified reference voltage, comprises: an operational amplifier circuit, comprising an in-phase input terminal for receiving the first reference voltage, an inverting input terminal, and an output terminal coupled to the inverting input terminal of the operational amplifier circuit for generating the modified reference voltage; a compensation capacitor coupled between the output terminal of the operational amplifier circuit and a ground terminal; and a compensation branch circuit coupled between the output terminal of the operational amplifier circuit and the ground terminal, and comprising an auxiliary switch and a current source connected in series; a comparator comprising a first input terminal coupled to the output capacitor for receiving a signal related to a first output voltage of the power conversion circuit, a second input terminal coupled to the reference signal generating circuit for receiving a signal related to the modified reference voltage, and an output terminal for outputting a comparison signal; a conduction time control circuit coupled to the output terminal of the comparator, for generating a conduction time control signal according to the comparison signal; and A driving circuit is coupled to the on-time control circuit and is used to generate a driving control signal according to the on-time control signal to control the operation of the main switch of the power conversion circuit.

2. The power conversion circuit according to claim 1, wherein: When the comparison signal is at a rising edge, the control circuit controls the main switch to be turned on. 3 . The power conversion circuit as claimed in claim 1 , wherein the auxiliary switch is controlled by the on-time control signal, and the current source is used to generate a first current. 4 . The power conversion circuit as claimed in claim 3 , wherein when the auxiliary switch is turned on, the first current discharges the compensation capacitor.

5. The power conversion circuit as claimed in claim 1, wherein the power conversion circuit further comprises: A voltage divider circuit is connected in parallel to the output capacitor, and includes a first resistor and a second resistor connected in series. The first input terminal of the comparator is coupled to a common node between the first resistor and the second resistor. 6 . The power conversion circuit as claimed in claim 1 , wherein the operational amplifier circuit is an operational transconductance amplifier. 7 . The power conversion circuit as claimed in claim 1 , wherein the current source of the compensation branch circuit is a fixed current source.

8. The power conversion circuit as claimed in claim 1, wherein the current source of the compensation branch circuit comprises: a controlled current source connected in series with the auxiliary switch; as well as A voltage-to-current control circuit is coupled to the controlled current source and is used for controlling the controlled current source to output the first current according to a first voltage.

9. The power conversion circuit as claimed in claim 1, wherein the current source of the compensation branch circuit comprises: A third resistor is connected in series with the auxiliary switch.

10. The power conversion circuit as claimed in claim 1, wherein the current source of the compensation branch circuit comprises: a third resistor connected in series with the auxiliary switch; a controlled current source connected in parallel to the third resistor; as well as A voltage-to-current control circuit is coupled to the controlled current source and is used for controlling the controlled current source to output a second current according to a first voltage, so that the current source outputs the first current.

11. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier coupled to a control signal terminal of the operational amplifier circuit, for generating an error signal to the control signal terminal of the operational amplifier circuit according to the first output voltage and the first reference voltage; The operational amplifier circuit generates the modified reference voltage according to the first reference voltage and the error signal, the modified reference voltage is determined according to the first reference voltage and an offset voltage of the operational amplifier circuit, and the offset voltage is adjusted according to the error signal generated based on the first output voltage and the first reference voltage.

12. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier, used for generating an error signal according to the first output voltage and a second reference voltage; a voltage gain circuit, coupled to the error amplifier, for performing a gain process on the error signal to generate an offset compensation signal; as well as An adding circuit is coupled to the voltage gain circuit and the non-inverting input terminal of the operational amplifier circuit, and is used for adding the offset compensation signal and the second reference voltage to generate the first reference voltage to the non-inverting input terminal of the operational amplifier circuit.

13. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier, configured to generate an error signal according to the first output voltage and the first reference voltage; a voltage gain circuit, coupled to the error amplifier, for performing a gain process on the error signal to generate an offset compensation signal; and an adding circuit coupled to the voltage gain circuit, the inverting input terminal of the operational amplifier circuit, and the output terminal of the operational amplifier circuit; The operational amplifier circuit generates the modified reference voltage according to the first reference voltage and the offset compensation signal.

14. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier coupled to an offset voltage control signal terminal of the comparator, for generating an error signal to the offset voltage control signal terminal of the comparator according to the first output voltage and the first reference voltage; The comparator generates the comparison signal according to the error signal, the corrected reference voltage and the first output voltage, the comparison signal is determined according to the corrected reference voltage, the first output voltage and an offset voltage of the comparator, and the offset voltage is adjusted according to the error signal generated based on the first output voltage and the first reference voltage.

15. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier, configured to generate an error signal according to the first output voltage and the first reference voltage; a voltage gain circuit, coupled to the error amplifier, for performing a gain process on the error signal to generate an offset compensation signal; as well as An adding circuit is coupled to the voltage gain circuit and the output end of the operational amplifier circuit, and is used to add the offset compensation signal and the corrected reference voltage output by the reference signal generating circuit and output a first corrected reference voltage to the second input end of the comparator.

16. The power conversion circuit as claimed in claim 1, wherein the control circuit further comprises an offset control circuit, comprising: an error amplifier, configured to generate an error signal according to the first output voltage of the output capacitor and the first reference voltage; a voltage gain circuit, coupled to the error amplifier, for performing a gain process on the error signal to generate an offset compensation signal; as well as An adding circuit is coupled to the voltage gain circuit and is used for adding the offset compensation signal and the first output voltage of the power conversion circuit to generate a second output voltage to the first input terminal of the comparator.

Images