On-time controller, power converter, and switching operation method therefor

Abstract

A turn-on time controller for controlling a switching operation of a power converter includes a turn-on time control circuit for controlling a turn-on time signal of a switching circuit of the power converter according to a reference voltage, where the reference voltage varies with an output voltage of an output terminal of the switching circuit; and a frequency adjustment circuit, coupled to the on-time control circuit, for sensing the output voltage of the output terminal of the switching circuit, generating a load sensing current according to the output voltage, and providing the load sensing current to the on-time control circuit to compensate the reference voltage, therefore, the turn-on time signal of the switching circuit and the switching frequency of the switching circuit are adjusted.

Description

Technical Field

[0001] The present invention relates to an on-time controller, a power converter and a switching operation method for the power converter, and in particular to an on-time controller, a power converter and a switching operation method for the power converter that can adjust or compensate the operating frequency of the power converter. Background Art

[0002] Please refer to Figure 1 , Figure 1 The schematic diagram of a conventional ripple-based constant on-time (RBCOT) power converter 10 is shown. The power converter 10 includes a comparator CMP, a constant on-time generator 102, a flip-flop FF, and a switch driving circuit 104. The power converter 10 operates in a fast transient response control mode to provide an output voltage VOUT to a load LOAD. Specifically, the power converter 10 compares a divided voltage VFB of the output voltage VOUT and a reference voltage VREF. When the voltage VFB is less than the reference voltage VREF, the constant on-time generator 102 of the power converter 10 is triggered to generate a turn-on reset signal TON_RESET, so that the switch driving circuit 104 of the power converter 10 performs a switch switching operation; in this way, the power converter 10 can convert an input voltage VIN into an output voltage VOUT.

[0003] Please refer to Figure 2 , Figure 2 1 is a schematic diagram of a conventional constant on-time control generator 102. When a voltage VIN_TON of a capacitor C_TON of the constant on-time control generator 102 increases to be higher than a threshold VO_TON, the on-reset signal TON_RESET is reset from a high potential to a low potential to perform a switching operation of the switch driving circuit 104. However, in the conventional ripple-modulated constant on-time control power converter 10, under the above operation, as the load LOAD of the power converter 10 increases, a turn-off interval TOFF of the power converter 10 decreases accordingly, resulting in an increase in the switching frequency of the power converter 10.

[0004] Therefore, the prior art needs to be improved. Summary of the invention

[0005] In view of this, an embodiment of the present invention provides an on-time controller, a power converter, and a switching operation method for the power converter to adjust an operating frequency of the power converter.

[0006] An embodiment of the present invention discloses a conduction time controller for controlling a switching operation of a power converter, including a conduction time control circuit for controlling a conduction time signal of a switching circuit of the power converter according to a reference voltage, wherein the reference voltage changes with an output voltage of an output end of the switching circuit; and a frequency adjustment circuit coupled to the conduction time control circuit for sensing the output voltage of the output end of the switching circuit, generating a load sensing current according to the output voltage, and providing the load sensing current to the conduction time control circuit to compensate for the reference voltage, so as to adjust the conduction time signal of the switching circuit and a switching frequency of the switching circuit.

[0007] An embodiment of the present invention further discloses a power converter, including a switching circuit, including an output terminal connected to a load, for generating an output voltage according to the conduction and shutdown of the switching circuit, and providing the output voltage to the load; and a conduction controller, coupled to the switching circuit, including a conduction time control circuit, for controlling a conduction time signal of the switching circuit of the power converter according to a reference voltage, wherein the reference voltage changes with an output voltage of the output terminal of the switching circuit; and a frequency adjustment circuit, coupled to the conduction time control circuit, for sensing the output voltage of the output terminal of the switching circuit, generating a load sensing current according to the output voltage, and providing the load sensing current to the conduction time control circuit to compensate for the reference voltage, so as to adjust the conduction time signal of the switching circuit and a switching frequency of the switching circuit.

[0008] An embodiment of the present invention further discloses a switching operation method for a power converter, wherein the power converter includes a switching circuit and a conduction controller, and the conduction controller includes a conduction time control circuit and a frequency adjustment circuit. The switching operation method includes the conduction time control circuit controlling a conduction time signal of the switching circuit of the power converter according to a reference voltage, wherein the reference voltage changes with an output voltage of an output end of the switching circuit; and the frequency adjustment circuit sensing the output voltage of the output end of the switching circuit, generating a load sensing current according to the output voltage, and providing the load sensing current to the conduction time control circuit to compensate for the reference voltage, so as to adjust the conduction time signal of the switching circuit and a switching frequency of the switching circuit. BRIEF DESCRIPTION OF THE DRAWINGS

[0009] Figure 1 A schematic diagram of a conventional ripple modulation power converter with on-time control is shown.

[0010] Figure 2 FIG. 1 is a schematic diagram of a conventional constant on-time control generator.

[0011] Figure 3 FIG. 4 is a schematic diagram of a power converter according to an embodiment of the present invention.

[0012] Figure 4 FIG. 4 is a schematic diagram of a constant on-time control generator according to an embodiment of the present invention.

[0013] Figure 5 FIG. 4 is a schematic diagram of a frequency adjustment circuit according to an embodiment of the present invention.

[0014] Figure 6 FIG. 1 is a timing diagram of a comparison voltage node before and after frequency compensation according to an embodiment of the present invention.

[0015] Figure 7 FIG. 4 is a schematic diagram of a switching operation process according to an embodiment of the present invention.

[0016] The reference numerals are described as follows:

[0017] 10: Power Converter

[0018] 102: Constant on-time control generator

[0019] 104: Switch drive circuit

[0020] 30: Power Converter

[0021] 302: Switching Circuit

[0022] 304: conduction controller

[0023] 304_2: On-time control circuit

[0024] 304_2_OTG: Constant On-Time Control Generator

[0025] 304_4: Frequency adjustment circuit

[0026] 70: Switching operation process

[0027] 702-708: Steps

[0028] CM_1: First current mirror

[0029] CM_2: Second current mirror

[0030] CMP, CMP1, CMP2: Comparator

[0031] COUT: Capacitor

[0032] C_TON: Capacitance

[0033] Driver_UG, Driver_LG: Driver

[0034] FF: Trigger

[0035] FI: Filter

[0036] iL: Inductor current

[0037] ISEN_LOAD: Load sensing current

[0038] ILOAD: current

[0039] IVIN: Input current

[0040] LOAD: Load

[0041] R: resistance unit

[0042] R1, R2, R3, R4: resistors

[0043] S_TON,S_TON': On-time signal

[0044] SW: Output terminal

[0045] SW_21, SW_22: Switch

[0046] SW_1: First switch

[0047] SW_2: Second switch

[0048] TOFF: Off interval

[0049] TON: conduction interval

[0050] TON_RESET, TON_RESET: Turn-on reset signal

[0051] TON_SHOT: signal

[0052] VIN: Input voltage

[0053] VFB: voltage

[0054] VOUT: output voltage

[0055] VO_TON, VO_TON': reference voltage

[0056] VREF: reference voltage

[0057] VSW: output voltage DETAILED DESCRIPTION

[0058] Please refer to Figure 3 , Figure 3Schematic diagram of a power converter 30 according to an embodiment of the present invention. The power converter 30 includes a switch circuit 302, a conduction controller 304, and drivers Driver_UG and Driver_LG. The switch circuit 302 includes an output terminal SW connected to a load LOAD, which is used to generate an output voltage VOUT according to the conduction and shutdown of the switch circuit 302, and provide the output voltage VOUT to the load LOAD. The conduction controller 304 is coupled to the switch circuit 302, and includes an on-time control circuit 304_2 and a frequency adjustment circuit 304_4. The on-time control circuit 304_2 is used to control an on-time signal S_TON of the switch circuit 302 of the power converter 30 according to a reference voltage VO_TON, wherein the reference voltage VO_TON changes with an output voltage VSW of the output terminal SW of the switch circuit 302. The frequency adjustment circuit 304_4 is coupled to the on-time control circuit 304_2, and is used to sense the output voltage VSW of the output terminal SW of the switch circuit 302, generate a load sensing current ISEN_LOAD according to the output voltage VSW, and provide the load sensing current ISEN_LOAD to the on-time control circuit 304_2 to compensate for the reference voltage VO_TON, thereby adjusting the on-time signal S_TON of the switch circuit 302 and a switching frequency of the switch circuit.

[0059] In detail, the switch circuit 302 includes a first switch SW_1 and a second switch SW_2, wherein the first switch SW_1 and the second switch SW_2 can be Metal-Oxide-Semiconductor Field-Effect Transistor (MOSFET) switches. In this example, the first switch SW_1 is a PMOS switch and the second switch SW_2 is an NMOS switch, but this is not limited to this.

[0060] The first switch SW_1 and the second switch SW_2 are coupled to the drivers Driver_UG and Driver_LG, respectively. When the switch circuit 302 is turned on (i.e., the first switch SW_1 is turned on and the second switch SW_2 is turned off), the embodiment of the present invention does not detect the inductor current iL; when the switch circuit 302 is turned off (i.e., the first switch SW_1 is turned off and the second switch SW_2 is turned on), the power converter 30 senses the inductor current iL flowing through the output terminal SW, and compensates the frequency change caused by the change of the load LOAD according to the sensed inductor current iL. The above compensation amount can be provided to the on-time control circuit 304_2 to compensate the reference voltage VO_TON, and then adjust the on-time signal S_TON of the switch circuit 302 accordingly, for example, increase the on-time interval TON of the on-time signal S_TON in one cycle.

[0061] It is worth noting that since a duty cycle of the switch circuit 302 of the power converter 30 of the embodiment of the present invention is a certain value, and a single duty cycle of the shutdown circuit 302 is composed of a conduction interval TON and a shutdown interval TOFF. Therefore, the frequency adjustment circuit 304_4 can adjust the shutdown interval TOFF of the switch circuit 302 according to the conduction interval TON of the conduction time signal S_TON. In this way, the power converter 30 can adjust the shutdown interval TOFF of the power converter 30 according to the sensed inductor current iL.

[0062] The on-time control circuit 304_2 includes a comparator CMP, a constant on-time control generator 304_2_OTG, and a flip-flop FF. The comparator CMP is used to compare a reference voltage VREF with a voltage VFB related to the output voltage VOUT to generate a signal TON_SHOT.

[0063] Please refer to Figure 4 , Figure 4 Schematic diagram of a constant on-time control generator 304_2_OTG according to an embodiment of the present invention. The constant on-time control generator 304_2_OTG comprises a capacitor C_TON, a first current mirror CM_1 and a comparator CMP. The first current mirror CM_1 is used to generate an input current IVIN to charge the capacitor C_TON according to an input voltage VIN; the comparator CMP1 is coupled to the capacitor C_TON and the first current mirror CM_1, and is used to compare the capacitor voltage VIN_TON of the capacitor C_TON with the reference voltage VO_TON to determine a conduction reset signal TON_RESET, wherein the conduction reset signal TON_RESET is a pulse signal, which can be used to determine the conduction time signal S_TON of the switch circuit 302.

[0064] Please refer to Figure 3 The flip-flop FF generates an on-time signal TON according to the on-reset signal TON_RESET and the signal TON_SHOT, wherein the on-time signal S_TON may be a pulse-width modulation (PWM) signal, and the PWM signal may be determined by the on-reset signal TON_RESET. For example, when the on-reset signal TON_RESET is a high-voltage pulse signal, the on-time signal S_TON will switch from a high voltage to a low voltage, that is, switch from the on-interval TON to the off-interval TOFF, and also determine the falling edge of the PWM signal at the same time.

[0065] Please refer to Figure 5 , Figure 5FIG. 1 is a schematic diagram of a frequency adjustment circuit 304_4 according to an embodiment of the present invention. The frequency adjustment circuit 304_4 includes a comparator CMP2, a second current mirror CM_2, a resistor unit R, and a filter FI. The comparator CMP2 is used to compare a ground voltage GND and an output voltage VSW of the output terminal SW of the switch circuit 302, and output a comparison result. The second current mirror CM_2 is coupled to the comparator CMP, and is used to generate a load sensing current ISEN_LOAD according to the comparison result of the comparator CMP. The resistor unit R is coupled to the second current mirror CM_2, and includes resistors R1, R2, R3, and R4 (herein, resistors R1-R4 are used as examples for description, and the number of resistor elements and individual resistance values ​​contained in the resistor unit R can be adjusted according to design requirements, and the embodiment of the present invention is not limited to this), and is used to receive the load sensing current ISEN_LOAD provided by the second current mirror CM_2, so as to generate a voltage compensation amount corresponding to the load sensing current ISEN_LOAD when the switch circuit 302 is turned off. The filter FI is coupled to the resistor unit R. The filter FI may be an integrator for integrating the voltage compensation amount corresponding to the load sensing current ISEN_LOAD to determine the reference voltage VO_TON. That is, the filter FI increases the reference voltage VO_TON according to the result of integrating the load sensing current ISEN_LOAD.

[0066] In order to obtain information about the load LOAD, the power converter 30 can sense the current of the output terminal SW. In one embodiment, the frequency adjustment circuit 304_4 is used to sense the output voltage VSW of the output terminal SW to detect the inductor current iL flowing through the inductor L when the switch circuit 302 is turned off, and the inductor current iL is used as a basis for compensating the load LOAD variation.

[0067] It is worth noting that since the power converter 30 senses the inductor current iL flowing through the output terminal SW in the interval when the second switch SW_2 is turned on, the load sensing current ISEN_LOAD used for compensation is fed back to the reference voltage VO_TON for frequency compensation in the interval when the second switch SW_2 is turned on.

[0068] The comparator CMP2 of the frequency adjustment circuit 304_4 of the embodiment of the present invention compares the ground voltage GND and the output voltage VSW of the output terminal SW of the switch circuit 302 to generate a load sensing current ISEN_LOAD, wherein when the output voltage VSW of the output terminal SW of the switch circuit 302 is less than zero (i.e., when a switch SW_22 of the current mirror CM_2 is turned on), the load sensing current ISEN_LOAD increases as the output voltage VSW decreases, and when the output voltage VSW is greater than zero (i.e., when a switch SW_21 of the current mirror CM_2 is turned on), the load sensing current ISEN_LOAD is not generated.

[0069] A voltage value VO_TON for frequency compensation according to the above embodiment COMP As shown in formula (1):

[0070]

[0071] Duty is a duty cycle of the power converter 30 , for example, a ratio of the working time of the power converter 30 to the total time in one cycle.

[0072] On the other hand, the relationship between the on-time interval TON and the off-time TOFF of the on-time signal S_TON of the power converter 30 is as shown in equations (2) and (3):

[0073]

[0074]

[0075] When the duty cycle Duty of the switch circuit 302 is constant, the compensation load sensing current ISEN_LOAD of the frequency adjustment circuit 304_4 can be used to increase the on-time TON and the off-time TOFF of the switch circuit 302 .

[0076] In this way, through the load sensing current ISEN_LOAD used for compensation, when the working cycle of the power converter 30 is fixed, the reference voltage VO_TON, the on-time TON and the off-time TOFF are also increased, thereby adjusting / compensating the operating frequency of the switching circuit 302 of the power converter 30.

[0077] Please refer to Figure 6 , Figure 6 FIG. 1 is a timing diagram of the comparison voltage node before and after frequency compensation according to an embodiment of the present invention. Figure 6 As shown, compared with the reference voltage VO_TON, the on-reset signal TON_RESET and the on-time signal S_TON, the reference voltage VO_TON′, the on-reset signal TON_RESET′ and the on-time signal S_TON′ are the results of frequency compensation of the power converter 30 .

[0078] There is a load compensation difference D between the reference voltage VO_TON' and the reference voltage VO_TON, wherein through the frequency compensation of the power converter 30, a capacitor voltage VIN_TON' maintains a slope same as that of the capacitor voltage VIN_TON and rises to the reference voltage VO_TON'. In this case, the time point at which the high-voltage pulse signal of the conduction reset signal TON_RESET' appears is relatively delayed, so that the duration of the conduction interval TON of the conduction time signal S_TON' increases. In addition, since the duty cycle of the power converter 30 is a constant value, the off interval TOFF of the power converter 30 also increases accordingly to adjust / compensate the operating frequency of the switching circuit 302 of the power converter 30.

[0079] The operation of the power converter 30 can be summarized as a switching operation process 70. Figure 7 The switching operation process 70 of the power converter 30 includes the following steps:

[0080] Step 702: Start;

[0081] Step 704: The on-time control circuit 304_2 controls the on-time signal S_TON of the switch circuit 302 of the power converter 30 according to the reference voltage VO_TON;

[0082] Step 706: The frequency adjustment circuit 304_4 senses the output voltage VSW of the output terminal SW of the switch circuit 302, generates a load sensing current ISEN_LOAD according to the output voltage VSW, and provides the load sensing current ISEN_LOAD to the on-time control circuit 304_2 to compensate the reference voltage VO_TON, so as to adjust the on-time signal S_TON of the switch circuit 302 and the switching frequency of the switch circuit;

[0083] Step 708: End.

[0084] Regarding the operation process of the switching operation process 70 , reference may be made to the above-mentioned embodiment of the power converter 30 , which will not be described in detail herein.

[0085] In summary, the embodiments of the present invention provide an on-time controller, a power converter, and a switching operation method for the power converter, which detects the load current to perform frequency compensation and thus adjust the operating frequency of the power converter.

[0086] 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 conduction time controller for controlling all switching operations of a power converter, comprising: a conduction time control circuit for controlling a conduction time signal of a switch circuit of the power converter according to a reference voltage, wherein the reference voltage varies with an output voltage of an output terminal of the switch circuit; as well as A frequency adjustment circuit is coupled to the on-time control circuit, and is used to sense the output voltage of the output end of the switch circuit, generate a load sensing current according to the output voltage, and provide the load sensing current to the on-time control circuit to compensate for the reference voltage, so as to adjust the on-time signal of the switch circuit and a switching frequency of the switch circuit. 2 . The on-time controller as claimed in claim 1 , wherein the frequency adjustment circuit senses the output voltage of the output terminal to detect an inductor current when the switch circuit is turned off. 3 . The on-time controller as claimed in claim 1 , wherein the frequency adjustment circuit adjusts a closing interval of the switch circuit according to a on-time interval of the on-time signal, wherein a duty cycle of the switch circuit is a constant value. 4 . The on-time controller as claimed in claim 1 , wherein the switch circuit is used to generate an output voltage to a load of the power converter according to the on and off state of the switch circuit.

5. The on-time controller as claimed in claim 1, wherein the on-time control circuit comprises: A capacitor; a first current mirror, for generating an input current to charge the capacitor according to an input voltage; and A comparator is coupled to the capacitor and the first current mirror, and is used for comparing a capacitor voltage of the capacitor with the reference voltage to determine a conduction reset signal.

6. The on-time controller as claimed in claim 1, wherein the frequency adjustment circuit comprises: a comparator, used for comparing a ground voltage with the output voltage of the output terminal of the switch circuit, and outputting a comparison result; a second current mirror, coupled to the comparator, for generating the load sensing current according to the comparison result; a resistor unit, coupled to the second current mirror, for receiving the load sensing current provided by the second current mirror, so as to generate a voltage compensation amount corresponding to the load sensing current when the switch circuit is turned off; as well as A filter is coupled to the resistor unit and is used for integrating the voltage compensation amount corresponding to the load sensing current to determine the reference voltage. 7 . The on-time controller as claimed in claim 6 , wherein when the output voltage of the output terminal of the switch circuit is less than zero, the load sensing current increases as the output voltage decreases.

8. The on-time controller as claimed in claim 1, wherein when a duty cycle of the switch circuit is a certain value, the frequency adjustment circuit compensates the load sensing current to increase a conduction interval of the on-time signal and a turn-off interval of the switch circuit.

9. A power converter, comprising: a switch circuit, comprising an output terminal connected to a load, for generating an output voltage according to the on and off state of the switch circuit, and providing the output voltage to the load; and A conduction controller, coupled to the switch circuit, comprises: a conduction time control circuit for controlling a conduction time signal of the switch circuit of the power converter according to a reference voltage, wherein the reference voltage varies with an output voltage of the output terminal of the switch circuit; as well as A frequency adjustment circuit is coupled to the on-time control circuit, and is used to sense the output voltage of the output end of the switch circuit, generate a load sensing current according to the output voltage, and provide the load sensing current to the on-time control circuit to compensate for the reference voltage, so as to adjust the on-time signal of the switch circuit and a switching frequency of the switch circuit. 10 . The power converter as claimed in claim 9 , wherein the frequency adjustment circuit is arranged to sense the output voltage of the output terminal to detect an inductor current when the switch circuit is turned off. 11 . The power converter as claimed in claim 9 , wherein the frequency adjustment circuit adjusts a closing interval of the switch circuit according to a conducting interval of the conducting time signal, wherein a duty cycle of the switch circuit is a constant value.

12. The power converter as claimed in claim 9, wherein the on-time control circuit comprises: A capacitor; a first current mirror, for generating an input current to charge the capacitor according to an input voltage; and A comparator is coupled to the capacitor and the first current mirror, and is used for comparing a capacitor voltage of the capacitor with the reference voltage to determine a conduction reset signal.

13. The power converter as claimed in claim 9, wherein the frequency adjustment circuit comprises: a comparator, used for comparing a ground voltage with the output voltage of the output terminal of the switch circuit, and outputting a comparison result; a second current mirror, coupled to the comparator, for generating the load sensing current according to the comparison result; a resistor unit, coupled to the second current mirror, for receiving the load sensing current provided by the second current mirror, so as to generate a voltage compensation amount corresponding to the load sensing current when the switch circuit is turned off; as well as A filter is coupled to the resistor unit and is used for integrating the voltage compensation amount corresponding to the load sensing current to determine the reference voltage. 14 . The power converter as claimed in claim 13 , wherein when the output voltage at the output terminal of the switch circuit is less than zero, the load sensing current increases as the output voltage decreases. 15 . The power converter as claimed in claim 9 , wherein when a duty cycle of the switch circuit is a constant value, the frequency adjustment circuit compensates the load sensing current to increase a conduction interval of the conduction time signal and a turn-off interval of the switch circuit.

16. A switching operation method for a power converter, wherein the power converter comprises a switch circuit and a conduction controller, and the conduction controller comprises a conduction time control circuit and a frequency adjustment circuit, the switching operation method comprising: The on-time control circuit controls an on-time signal of the switch circuit of the power converter according to a reference voltage, wherein the reference voltage changes with an output voltage of an output terminal of the switch circuit; as well as The frequency adjustment circuit senses the output voltage of the output end of the switch circuit, generates a load sensing current according to the output voltage, and provides the load sensing current to the on-time control circuit to compensate the reference voltage to adjust the on-time signal of the switch circuit and a switching frequency of the switch circuit.

17. The switching operation method for a power converter as claimed in claim 16, further comprising: A first current mirror of the conduction time control circuit generates an input current according to an input voltage to charge a capacitor of the conduction time control circuit; and A comparator of the on-time control circuit compares a capacitor voltage of the capacitor with the reference voltage to determine a on-reset signal.

18. The switching operation method for a power converter as claimed in claim 16, further comprising: A comparator of the frequency adjustment circuit compares a ground voltage with the output voltage of the output end of the switch circuit and outputs a comparison result; A second current mirror of the frequency adjustment circuit generates the load sensing current according to the comparison result; A resistor unit of the frequency adjustment circuit receives the load sensing current provided by the second current mirror to generate a voltage compensation amount corresponding to the load sensing current when the switch circuit is turned off; and A filter of the frequency adjustment circuit integrates the voltage compensation amount corresponding to the load sensing current to determine the reference voltage. 19 . The switching operation method for a power converter as claimed in claim 16 , wherein when the output voltage of the output terminal of the switch circuit is less than zero, the load sensing current increases as the output voltage decreases.

20. The switching operation method for a power converter as claimed in claim 16, wherein when a duty cycle of the switch circuit is a certain value, the frequency adjustment circuit compensates the load sensing current to increase a conduction interval of the conduction time signal and a turn-off interval of the switch circuit.

Images