Boosting switching power supply and boosting controller thereof

Abstract

A boost switching power supply and a boost controller thereof are provided. The boost switching power supply includes a transformer, a pulse width modulation controller, and the boost controller. A voltage at a switch control pin of the boost controller is provided by an auxiliary winding of the transformer, and a voltage at a chip supply pin of the boost controller is both a supply voltage of the boost controller and a supply voltage of the pulse width modulation controller. The boost controller is configured to: the voltage at the chip supply pin of the boost controller starts to increase after the boost switching power supply is powered on; and the voltage at the switch control pin of the boost controller starts to increase after the pulse width modulation controller is started. The boost controller is started when the voltage at the switch control pin of the boost controller is greater than a start voltage of the boost controller and the voltage at the chip supply pin of the boost controller is greater than an under-voltage lockout shutdown threshold of the boost controller.

Description

Technical Field

[0001] The present invention relates to the field of integrated circuits, and in particular to a boost switching power supply and a boost controller thereof. Background Art

[0002] A switching power supply, also known as an alternating current power supply or switching converter, is a type of power supply. Its function is to convert a voltage level to the voltage or current required by the user through various topologies (such as flyback, buck, or boost). Summary of the Invention

[0003] According to an embodiment of the present invention, a boost controller for a boost switching power supply is provided, wherein the boost switching power supply includes a transformer, a pulse width modulation controller, and a boost controller, the voltage at the switch control pin of the boost controller is provided by the auxiliary winding of the transformer, the voltage at the chip power supply pin of the boost controller is both the power supply voltage of the boost controller and the power supply voltage of the pulse width modulation controller, and the boost controller is configured as follows: the voltage at the chip power supply pin of the boost controller starts to increase after the boost switching power supply is powered on; and the voltage at the switch control pin of the boost controller starts to increase after the pulse width modulation controller is started, wherein when the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout shutdown threshold of the pulse width modulation controller, the pulse width modulation controller is started; when the voltage at the switch control pin of the boost controller is greater than the start-up voltage of the boost controller and the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout shutdown threshold of the boost controller, the boost controller is started.

[0004] According to an embodiment of the present invention, a boost controller for a boost switching power supply includes a transformer, a pulse width modulation controller, and a boost controller. The voltage at the switch control pin of the boost controller is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the power supply voltage of the boost controller and the power supply voltage of the pulse width modulation controller. The boost controller is configured as follows: the voltage at the chip power supply pin of the boost controller begins to increase after the boost switching power supply is powered on; when the voltage at the chip power supply pin of the boost controller is greater than the voltage at the chip power supply pin connected to the boost controller and the switch control pin, the boost controller is configured as follows: When the turn-on voltage of the power switch between the pins is greater than the turn-on voltage of the power switch, the power switch is turned on, so that the voltage at the switch control pin of the boost controller is equal to the voltage at the chip power supply pin of the boost controller; when the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout shutdown threshold of the boost controller, the boost controller is started, the power switch is disconnected, and the power supply voltage of the boost controller is switched from the voltage at the chip power supply pin of the boost controller to the voltage at the switch control pin of the boost controller, wherein when the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout shutdown threshold of the pulse width modulation controller, the pulse width modulation controller is started.

[0005] A boost switching power supply according to an embodiment of the present invention includes the above-mentioned boost controller for a boost switching power supply. BRIEF DESCRIPTION OF THE DRAWINGS

[0006] The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the accompanying drawings, in which:

[0007] Figure 1 The system circuit diagram of a traditional flyback switching power supply is shown.

[0008] Figure 2 A system circuit diagram of a boost switching power supply according to an embodiment of the present invention is shown.

[0009] Figure 3 Shown Figure 2 The circuit schematic diagram of the boost control circuit of the boost controller shown.

[0010] Figure 4 Shown for Figure 2 An example circuit diagram of a startup control circuit of a boost controller is shown.

[0011] Figure 5 Shown Figure 4 The flowchart of the startup control process implemented by the startup control circuit is shown.

[0012] Figure 6 Shown Figure 4 Flowchart of the shutdown / power-off control process implemented by the startup control circuit shown.

[0013] Figure 7 Shown for Figure 2 An example circuit diagram of another startup control circuit of a boost controller is shown.

[0014] Figure 8 Shown for Figure 2 An example circuit diagram of another startup control circuit of a boost controller is shown.

[0015] Figure 9 Shown Figure 8 The flowchart of the startup control process implemented by the startup control circuit is shown. DETAILED DESCRIPTION

[0016] The features and exemplary embodiments of various aspects of the present invention will be described in detail below. In the detailed description below, many specific details are proposed to provide a comprehensive understanding of the present invention. However, it will be apparent to those skilled in the art that the present invention can be implemented without the need for some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the present invention by illustrating examples of the present invention. The present invention is by no means limited to any specific configuration and algorithm proposed below, but covers any modification, replacement, and improvement of elements, components, and algorithms without departing from the spirit of the present invention. In the accompanying drawings and the following description, known structures and techniques are not shown to avoid causing unnecessary ambiguity to the present invention.

[0017] Figure 1 FIG. 1 shows a system circuit diagram of a conventional flyback switching power supply 100. Figure 1 As shown, the flyback switching power supply 100 includes a transformer T, a power switch M connected to a primary winding Np of the transformer T, and a pulse width modulation (PWM) controller U1. The PWM controller U1 controls the on and off state of the power switch M based on a current sensing signal CS representing a primary current flowing through the primary winding Np of the transformer T and an output feedback signal FB representing a system output voltage Vout of the flyback switching power supply 100, thereby controlling the system output voltage Vout of the flyback switching power supply 100.

[0018] exist Figure 1In the illustrated flyback switching power supply 100, the supply voltage VDD of the PWM controller U1 is provided by the auxiliary winding Naux of the transformer T and varies proportionally with the system output voltage Vout. Therefore, if the system output voltage Vout varies over a wide range, the supply voltage VDD of the PWM controller U1 must also vary over a wide range (i.e., the difference between the maximum value VDDmax and the minimum value VDDmin of the supply voltage VDD must be very large). However, because the semiconductor devices used in the PWM controller U1 have a certain operating voltage range, and given a certain maximum withstand voltage of the semiconductor devices, the maximum value VDDmax of the supply voltage VDD of the PWM controller U1 is essentially fixed (due to semiconductor manufacturing process limitations). Therefore, the minimum value VDDmin of the supply voltage VDD of the PWM controller U1 must be very low to meet the requirement for a wide supply voltage VDD range.

[0019] However, when the minimum value VDDmin of the supply voltage VDD of the PWM controller U1 is very low, it is difficult to meet the power supply requirement of the PWM controller U1. In this case, a boost function must be added to the flyback switching power supply 100. The boost function can increase the minimum value VDDmin of the supply voltage VDD of the PWM controller U1 to a higher voltage value to ensure that the power supply requirement of the PWM controller U1 is met.

[0020] Figure 2 FIG. 2 shows a system circuit diagram of a boost switching power supply 200 according to an embodiment of the present invention. Figure 2 The boost switching power supply 200 shown is Figure 1 The difference of the flyback switching power supply 100 shown is that, in addition to the transformer T, the power switch M connected to the primary winding Np of the transformer T, and the PWM controller U1, it also includes a boost controller U2, wherein the switch control pin (i.e., SW pin) of the boost controller U2 is connected to the auxiliary winding Naux of the transformer T, and the voltage Vsw at the SW pin of the boost controller U2 is the input voltage Vin provided by the auxiliary winding Naux of the transformer T; the chip power supply pin (i.e., VDD pin) of the boost controller U2 is connected to the VDD pin of the PWM controller U1, and the voltage VDD at the VDD pin of the boost controller U2 is both the power supply voltage of the boost controller U2 and the power supply voltage of the PWM controller U1. Here, the working principle of the PWM controller U1 is combined with the Figure 1 The working principle described is similar and will not be repeated here.

[0021] Below, for the convenience of description, the voltage Vsw at the SW pin of the boost controller U2 and the input voltage Vin provided by the auxiliary winding Naux of the transformer T can be used interchangeably, and the voltage VDD at the VDD pin of the boost controller U2 and the supply voltage VDD of the PWM controller U1 can be used interchangeably.

[0022] During normal operation of the boost switching power supply 200, if the input voltage Vin provided by the auxiliary winding Naux of the transformer T is lower than the threshold voltage V0, the boost controller U2 regulates the input voltage Vin to the threshold voltage V0 and provides the threshold voltage V0 as the supply voltage VDD of the PWM controller U1. If the input voltage Vin provided by the auxiliary winding Naux of the transformer T is higher than the threshold voltage V0, the boost controller U2 does not regulate the input voltage Vin but directly provides the input voltage VDD to the PWM controller U1 as the supply voltage VDD. Therefore, the supply voltage VDD of the PWM controller U1 remains within the range from the threshold voltage V0 to VDDmax.

[0023] During the startup process of the boost switching power supply 200, the AC input voltage is processed by the electromagnetic interference filter and the voltage divider network to obtain a system input divided voltage Vac, which charges the capacitor C2 through the startup resistor Rstart. The supply voltage VDD of the PWM controller U1 increases in a ramp. When the supply voltage VDD of the PWM controller U1 reaches the undervoltage lockout threshold UVLO_off_bwm of the PWM controller U1, the PWM controller U1 starts to operate.

[0024] Figure 3 Shown Figure 2 The circuit schematic diagram of the boost control circuit 300 of the boost controller U2 is shown in FIG. Figure 3As shown, in the boost control circuit of boost controller U2: Diode D1 is connected between the SW pin and the VDD pin of boost controller U2; when the voltage Vsw at the SW pin of boost controller U2 is greater than the sum of the voltage VDD at the VDD pin and the conduction voltage Vdio of diode D1 (i.e., Vsw > VDD + Vdio), diode D1 conducts, and the voltage Vsw at the SW pin of boost controller U2 is supplied to the VDD pin of boost controller U2 via diode D1 and serves as the supply voltage VDD of PWM controller U1; when the voltage Vsw at the SW pin of boost controller 102 is less than the sum of the voltage VDD at the VDD pin and the conduction voltage Vdio of diode D1 (i.e., Vsw < VDD + Vdio), diode D1 turns off, and the voltage Vsw at the SW pin of boost controller 102 is adjusted to the threshold voltage V0 by controlling the conduction and turn-off of power switches M11 and M22, and the threshold voltage V0 is supplied to the VDD pin of boost controller U2 and serves as the supply voltage VDD of PWM controller U1.

[0025] As Figure 3 shown, in the boost control circuit 300 of boost controller U2: The transconductance operational amplifier Gm compares the voltage VDD at the VDD pin of boost controller U2 with the threshold voltage Vreg, and generates a charging current to charge capacitor C11 when VDD < Vreg; the voltage VC on capacitor C11 increases, and the pulse generator Burst generates an enable signal ENA = 1 based on the voltage VC on capacitor C11; the clock signal Fboost triggers the Q output of D flip-flop DFF1 to output Q = 1, causing power switches M11 and M22 to conduct; the resistor Rocp samples the current flowing through power switch M22; the comparator Comp compares the voltage VR on resistor Rocp with the threshold voltage Vref_ocp, and generates a protection signal SW_ocp = 0 when VR > Vref_ocp. At this time, the Q output of D flip-flop DFF1 outputs Q = 0, causing power switches M11 and M22 to turn off; when the conduction time of power switches M11 and M22 reaches the maximum conduction time, the maximum duty cycle signal Duty max indicating whether the conduction time of power switches M11 and M22 reaches the maximum conduction time is 0, and the Q output of D flip-flop DFF1 also outputs Q = 0, causing power switches M11 and M22 to turn off; when VDD > Vreg, the transconductance operational amplifier Gm generates a discharging current to discharge capacitor C11, the voltage VC on capacitor C11 decreases, the pulse generator Burst generates an enable signal ENA = 0 based on the voltage VC on capacitor C11, and the Q output of D flip-flop DFF1 outputs Q = 0, causing power switches M11 and M22 to disconnect.

[0026] Currently, the starting schemes for the boost switching power supply 200 include the following two schemes: Scheme 1) The PWM controller U1 is started first, and the boost controller U2 is started after the input voltage Vin provided by the auxiliary winding Naux of the transformer T increases to a certain value. However, when the PWM controller U1 is restarted next time, the input voltage Vin provided by the auxiliary winding Naux of the transformer T may be higher, causing the boost controller U2 to start earlier than the PWM controller U1. The PWM controller U1 cannot start due to insufficient starting current. Scheme 2) The boost controller U2 is started first, and the PWM controller U1 is started later. However, due to the power consumption of the boost controller U2 itself, the PWM controller U1 may not be able to start due to insufficient starting current.

[0027] In view of the above situation, a method for Figure 2 The startup scheme of the boost switching power supply 200 is shown to ensure that the boost switching power supply 200 can start, operate, and shut down normally.

[0028] Figure 4 Shown for Figure 2 An example circuit diagram of a startup control circuit 400 of a boost controller U2 is shown. Figure 4 The startup control circuit 400 shown can control the boost controller U2 to start after the PWM controller U1 starts, and can avoid the problem that the PWM controller U1 cannot restart due to insufficient startup current when the system restarts.

[0029] Figure 5 Shown Figure 4 FIG. 4 is a flowchart of a startup control process implemented by the startup control circuit 400. Figure 2 、 Figure 4 ,and Figure 5 It can be seen that after the boost switching power supply 200 is powered on: the voltage VDD at the VDD pin of the boost controller U2 slopes up; when the voltage VDD at the VDD pin of the boost controller U2 is greater than the under-voltage lockout threshold UVLO_off_pwm of the PWM controller U2, the PWM controller U1 starts up, and the voltage Vsw at the SW pin of the boost controller U2 slopes up; when the voltage Vsw at the SW pin of the boost controller U2 is less than the start-up voltage Vsw_on of the boost controller U2, the boost controller U2 does not start up; when the voltage Vsw at the SW pin of the boost controller U2 is greater than the start-up voltage Vsw_on of the boost controller U2 and the voltage VDD at the VDD pin of the boost transformer U2 is greater than the under-voltage lockout threshold UVLO_off_bst of the boost transformer U2, the boost transformer U2 starts up.

[0030] Figure 6 Shown Figure 4Flowchart of the shutdown / power-off control process implemented by the startup control circuit shown. In combination with Figure 2 , Figure 4 , and Figure 6 It can be seen that when the boost switching power supply 200 is powered off or protectively shut down: The PWM controller U1 does not output the gate drive signal for driving the conduction and cutoff of the power switch M, the voltage Vsw at the SW pin of the boost controller U2 decreases in a ramp manner, and the voltage VDD at the VDD pin of the boost controller U2 also decreases in a ramp manner after being maintained by the boost controller U2 for a period of time; When the voltage VDD at the VDD pin of the boost controller U2 is less than the discharge threshold Vdischar, the discharge enable signal Dischar_en = 1, the main discharge path is turned on, and the voltage Vsw at the SW pin of the boost controller U2 decreases rapidly; When the voltage VDD at the VDD pin of the boost controller U2 is less than the undervoltage lockout turn-on threshold UVLO_on_pwm of the PWM controller U1, the PWM controller U1 is turned off; When the voltage Vsw at the SW pin of the boost controller U@ is less than the shutdown voltage Vsw_off of the boost controller U2 and the voltage VDD at the VDD pin of the boost controller U2 is less than the undervoltage lockout turn-on threshold UVLO_on_bst of the boost controller U2, the boost controller U2 is turned off, and at the same time the main discharge path is turned off, waiting for the boost switching power supply 200 to restart.

[0031] In some embodiments, Figure 4 the startup control circuit 400 shown may also not include the main discharge path, as long as it can ensure that Vin < Vsw_off before VDD < UVLO_on_bst. In some cases, an auxiliary discharge path can also be added to the startup control circuit 400 shown to ensure that Vin < Vsw_off before VDD < UVLO_on_bst. For example, the conduction of the discharge path can be controlled based on the power good signal (i.e., PG signal) inside the boost controller U2.

[0032] Figure 7 Shows an example circuit diagram of the startup control circuit 700 for Figure 2 the boost controller U2 shown. Figure 7 The startup control circuit 700 shown and Figure 4 ​The difference between the startup control circuit 400 and the boost switching power supply 200 is that, during startup, the PG signal is generated as long as the voltage VDD at the VDD pin of the boost controller U2 is greater than the undervoltage lockout threshold UVLO_off_bst of the boost controller U2, regardless of the magnitude of the input voltage Vin provided by the auxiliary winding Naux of the transformer T. The boost controller U2 is only started when the input voltage Vin provided by the auxiliary winding Naux of the transformer T is greater than the startup voltage Vsw_on of the boost controller U2. This allows the PG signal generation circuit of the boost controller U2 to start first and then to operate normally only when Vin > Vsw_on, without having to worry about whether VDD is greater than UVLO_off_bst when Vin > Vsw_on.

[0033] Figure 8 Shown for Figure 2 An example circuit diagram of a startup control circuit 800 of a boost controller U2 is shown. Figure 8 The startup control circuit 800 shown can control the boost controller U2 to start before the PWM controller U1 starts, and can avoid the problem that the PWM controller U1 cannot start due to insufficient startup current.

[0034] Figure 9 Shown Figure 8 FIG. 7 is a flowchart of a startup control process implemented by the startup control circuit 700 shown in FIG. Figure 2 、 Figure 8 ,and Figure 9It can be seen that after the boost switching power supply 200 is powered on: the system input voltage Vac charges the capacitor C2 through the resistor Rstart. When the voltage VDD at the VDD pin of the boost controller U2 is greater than the on-threshold Vs1_on of the power switch S1, the power switch S1 is turned on, and the voltage Vsw at the SW pin of the boost controller U2 is equal to the voltage VDD at the VDD pin and charges the capacitor C1. When the voltage VDD at the VDD pin of the boost controller U2 is greater than the undervoltage lockout threshold UVLO_off_bst of the boost controller U2, the boost controller U2 is started and the power switch S1 is turned off. When the switch enable signal EN_SW=1, only the capacitor C1 supplies power to the boost controller U2, and the capacitor C 2 no longer supplies power to the boost controller U2; the system input voltage divider Vac continues to charge the capacitor C2 through the resistor Rstart. When the voltage VDD at the VDD pin of the boost controller U2 is greater than the undervoltage lockout threshold UVLO_off_pwm of the PWM controller U1, the PWM controller U1 starts, and the voltage VDD at the VDD pin of the boost controller U2 ramps down; when the voltage VDD at the VDD pin of the boost controller U2 is less than the threshold voltage Vth1, the capacitor C2 is switched back to supply power to the boost controller U2; when the voltage VDD at the VDD pin of the boost controller U2 is less than the undervoltage lockout threshold UVLO_on_bst of the boost controller U2, the boost controller U2 is turned off.

[0035] The present invention may be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithms described in the specific embodiments may be modified without departing from the basic spirit of the present invention. Therefore, the present embodiments are to be considered in all respects as illustrative and not restrictive, the scope of the invention is defined by the appended claims rather than the foregoing description, and all modifications coming within the meaning and scope of equivalents of the claims are intended to be included within the scope of the present invention.

Claims

1. A boost controller for a boost switching power supply, wherein: The boost switching power supply includes a transformer, a pulse width modulation controller, and the boost controller. The voltage at the switch control pin of the boost controller is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the power supply voltage of the boost controller and the power supply voltage of the pulse width modulation controller. The boost controller is configured as follows: The voltage at the chip power supply pin of the boost controller starts to increase after the boost switching power supply is powered on; The voltage at the switch control pin of the boost controller begins to increase after the pulse width modulation controller is started, wherein the pulse width modulation controller is started when the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout threshold of the pulse width modulation controller, and the boost controller is started when the voltage at the switch control pin of the boost controller is greater than the start-up voltage of the boost controller and the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout threshold of the boost controller; The voltage at the switch control pin of the boost controller begins to decrease after the boost switching power supply is powered off or protectively shut down; and The voltage at the chip power supply pin of the boost controller starts to decrease after the voltage at the switch control pin of the boost controller decreases to a point where the voltage at the chip power supply pin of the boost controller can no longer be maintained unchanged. When the voltage at the chip power supply pin of the boost controller is less than the undervoltage lockout turn-on threshold of the pulse width modulation controller, the pulse width modulation controller is turned off. When the voltage at the switch control pin of the boost controller is less than the turn-off voltage of the boost controller and the voltage at the chip power supply pin of the boost controller is less than the undervoltage lockout turn-on threshold of the boost controller, the boost controller is turned off.

2. The boost controller according to claim 1 , further configured to: When the voltage at the chip power supply pin of the boost controller is less than a discharge threshold, the voltage at the switch control pin of the boost controller is discharged.

3. The boost controller according to claim 1, further configured to: generating a power good signal after the boost controller is started; and A voltage at a switch control pin of the boost controller is discharged based on the power good signal.

4. The boost controller according to claim 1, further configured to: generating a power good signal when a voltage at a chip power supply pin of the boost controller is greater than an undervoltage lockout shutdown threshold of the boost controller; and A voltage at a switch control pin of the boost controller is discharged based on the power good signal.

5. A boost controller for a boost switching power supply, wherein: The boost switching power supply includes a transformer, a pulse width modulation controller, and the boost controller. The voltage at the switch control pin of the boost controller is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the power supply voltage of the boost controller and the power supply voltage of the pulse width modulation controller. The boost controller is configured as follows: The voltage at the chip power supply pin of the boost controller starts to increase after the boost switching power supply is powered on; When the voltage at the chip power supply pin of the boost controller is greater than the turn-on voltage of the power switch connected between the chip power supply pin and the switch control pin of the boost controller, the power switch is turned on, so that the voltage at the switch control pin of the boost controller is equal to the voltage at the chip power supply pin of the boost controller; When the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout threshold of the boost controller, the boost controller is started, the power switch is turned off, and the power supply voltage of the boost controller is switched from the voltage at the chip power supply pin of the boost controller to the voltage at the switch control pin of the boost controller, wherein the pulse width modulation controller is started when the voltage at the chip power supply pin of the boost controller is greater than the undervoltage lockout threshold of the pulse width modulation controller; The voltage at the chip power supply pin of the boost controller begins to decrease after the pulse width modulation controller is started; and When the voltage at the chip power supply pin of the boost controller is less than a switching threshold, the power supply voltage of the boost controller is switched from the voltage at the switch control pin of the boost controller back to the voltage at the power supply pin of the boost controller.

6. A boost switching power supply comprising the boost controller according to any one of claims 1 to 5.

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