TWI835291B - Boost switching power supply and its boost controller - Google Patents

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 a boost controller. The voltage at the switch control pin of the boost controller is provided by the auxiliary winding of the transformer. The chip power supply pin of the boost controller The voltage is both the supply voltage of the boost controller and the 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; and the voltage at the switch control pin of the boost controller starts to increase during the pulse width modulation It starts to increase after the variable controller is started. When the voltage at the switch control pin of the boost controller is greater than the startup 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 The controller starts.

Description

Boost switching power supply and its boost controller

The invention relates to the field of integrated circuits, and in particular to a boost switching power supply and a boost controller thereof.

Switching power supply, also known as switching power supply and switching converter, is a type of power supply. The function of the switching power supply is to convert a level of voltage to the user's desired voltage through different architectures (for example, fly-back architecture, buck architecture, or boost architecture, etc.) required voltage or current.

According to a boost controller for a boost switching power supply according to an embodiment of the present invention, the boost switching power supply includes a transformer, a pulse width modulation controller, and a boost controller, and the switch control pin of the boost controller The voltage at the pin is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the supply voltage of the boost controller and the supply voltage of the pulse width modulation controller. The boost controller is configured as: 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 starts up , where, 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 starts; when the switch control pin of the boost controller When the voltage at is greater than the startup 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 starts.

According to a boost controller for a boost switching power supply according to an embodiment of the present invention, the boost switching power supply includes a transformer, a pulse width modulation controller, and a boost controller, and the switch control pin of the boost controller The voltage at pin is provided by the auxiliary winding of the transformer, and the boost controller 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 is at the boost level. The switching power supply begins to increase after power 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 voltage at the chip power supply pin of the boost controller At the undervoltage lockout shutdown threshold, the boost controller starts, the power switch is turned off, and the supply voltage of the boost controller switches from the voltage at the chip power supply pin of the boost controller to the switch control pin of the boost controller. The pulse width modulation controller starts 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.

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.

100: Flyback switching power supply

U2: Boost controller

200: Boost switching power supply

300: Boost control circuit

400,700: Start control circuit

Burst: pulse generator

C1, C2, C11: capacitor

CS: current sensing pin

D1: Diode

DFF1:D flip-flop

Dischar_en: signal

Duty max: maximum duty cycle signal

EN_SW: switch enable signal

ENA: enable signal

FB: Output feedback signal

Fboost: clock signal

Gm: transconductance operational amplifier

M, M11, M22: power switch

Naux: auxiliary winding

Np: primary winding

Q:Output terminal

Rocp, Rstart: resistance

S1: Power switch

SW: switch control pin

SW_ocp: protection signal

T: Transformer

U1: Pulse width modulation (PWM) controller

UVLO_off_bwm: Undervoltage lockout shutdown threshold

UVLO_on_bst,UVLO_on_pwm: undervoltage lockout threshold

V0,Vreg,Vref_ocp,Vth1: threshold voltage

Vac: system input voltage divider

VC, Vsw, VR: voltage

VDD: supply voltage

Vdio: turn-on voltage

Vin: input voltage

Vout: system output voltage

Vs1_on: conduction threshold

Vsw_on: starting voltage

Vsw_off: turn off voltage

The present invention can be better understood from the following description of specific embodiments of the present invention in conjunction with the drawings, in which: Figure 1 shows a system circuit diagram of a traditional flyback switching power supply.

Figure 2 shows a system circuit diagram of a boost switching power supply according to an embodiment of the present invention.

FIG. 3 shows a circuit schematic diagram of the boost control circuit of the boost controller shown in FIG. 2 .

FIG. 4 shows an example circuit diagram of a startup control circuit for the boost controller shown in FIG. 2 .

FIG. 5 shows a flow chart of the startup control process implemented by the startup control circuit shown in FIG. 4 .

FIG. 6 shows a flow chart of the shutdown/power-down control process implemented by the startup control circuit shown in FIG. 4 .

FIG. 7 shows an example circuit diagram of another startup control circuit for the boost controller shown in FIG. 2 .

FIG. 8 shows an example circuit diagram of yet another startup control circuit for the boost controller shown in FIG. 2 .

FIG. 9 shows a flow chart of the startup control process implemented by the startup control circuit shown in FIG. 8 .

Features and exemplary embodiments of various aspects of the invention are described in detail below. In the following detailed description, numerous specific details are set forth in order to provide a thorough understanding of the invention. However, it will be apparent to one skilled in the art that the present invention may be practiced without some of these specific details. The following description of the embodiments is merely intended to provide a better understanding of the invention by illustrating examples of the invention. The present invention is in no way limited to any specific configurations and algorithms set forth below, but covers any modifications, substitutions and improvements of elements, components and algorithms without departing from the spirit of the invention. In the drawings and the following description, well-known structures and techniques are not shown in order to avoid unnecessarily obscuring the present invention.

Figure 1 shows a system circuit diagram of a traditional flyback switching power supply 100. As shown in Figure 1, the flyback switching power supply 100 includes a transformer T, a power switch M connected to the primary winding Np of the transformer T, and a pulse width modulation (PWM) controller U1, wherein the PWM controller U1 is based on the representation flow The current sensing pin CS of the primary current of the primary winding Np of the transformer T and the output feedback signal FB representing the system output voltage Vout of the flyback switching power supply 100 are used to control the on and off of the power switch M, thereby controlling the flyback. The system output voltage Vout of the switching power supply 100.

In the flyback switching power supply 100 shown in Figure 1, the supply voltage VDD of the PWM controller U1 is provided by the auxiliary winding Naux of the transformer T, and changes in proportion to the system output voltage Vout, so within the variation range of the system output voltage Vout In a very wide situation, the variation range of the supply voltage VDD of the PWM controller U1 must also be very wide (that is, the difference between the maximum value VDDmax and the minimum value VDDmin of the supply voltage VDD must be very large). However, since the semiconductor device used in PWM controller U1 has a certain operating voltage range, when the maximum withstand voltage of the semiconductor device is determined, the maximum value VDDmax of the supply voltage VDD of PWM controller U1 is basically fixed (subject to Semiconductor manufacturing process limitations), the minimum value VDDmin of the supply voltage VDD of the PWM controller U1 must be very low to meet the very wide variation range requirement of the supply voltage VDD of the PWM controller U1.

However, when the minimum value VDDmin of the power supply voltage VDD of the PWM controller U1 is very low, it is difficult to meet the power supply requirements of the PWM controller U1. At this time, a boost function must be added to the flyback switching power supply 100, and the boost function will The minimum value VDDmin of the power supply voltage VDD of the PWM controller U1 is increased to a higher voltage value to ensure that the power supply requirements of the PWM controller U1 are met.

FIG. 2 shows a system circuit diagram of a boost switching power supply 200 according to an embodiment of the present invention. The difference between the boost switching power supply 200 shown in FIG. 2 and the flyback switching power supply 100 shown in FIG. 1 is that, in addition to including a transformer T, a power switch M connected to the primary winding Np of the transformer T, and a PWM controller U1 Also included is 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 at the SW pin of the boost controller U2 Vsw is the input voltage Vin provided by the auxiliary winding Naux of the transformer T; the chip power supply pin (ie, VDD pin) of the boost controller U2 is connected to the VDD pin of the PWM controller U1, and the VDD of the boost controller U2 The voltage VDD at the pin is both the supply voltage of the boost controller U2 and the supply voltage of the PWM controller U1. Here, the working principle of the PWM controller U1 is similar to the working principle described in conjunction with Figure 1 and will not be described again.

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, The supply voltage VDD of the boost controller U2 and the supply voltage VDD of the PWM controller U1 can be used interchangeably.

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 adjusts the input voltage Vin to the threshold voltage V0 and sets the threshold voltage V0 as The supply voltage VDD of the PWM controller U1 is provided to 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 adjust the input voltage Vin, but directly The power supply voltage VDD of the PWM controller U1 is provided to the PWM controller U1. Therefore, the supply voltage VDD of the PWM controller U1 remains at the threshold voltage V0 to VDDmax.

During the startup process of the boost switching power supply 200, the AC input voltage is processed by the electromagnetic interference screening program and the voltage dividing network to obtain the system input divided voltage Vac, which charges the capacitor C1 through the starting resistor Rstart. The supply voltage of the PWM controller U1 The VDD slope increases; when the supply voltage VDD of the PWM controller U1 reaches the undervoltage lockout shutdown threshold UVLO_off_bwm of the PWM controller U1, the PWM controller U1 starts to work.

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

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

Currently, the starting schemes of the boost switching power supply 200 include the following two: Scheme 1) PWM controller U1 starts first, and then starts the boost controller U2 after the input voltage Vin provided by the auxiliary winding Naux of the transformer T increases to a certain value. , but when the PWM controller U1 restarts 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, and the PWM controller U1 cannot start due to insufficient starting current. Start; Option 2) The boost controller U2 starts first, and the PWM controller U1 starts later. However, due to the power consumption of the boost controller U2 itself, the PWM controller U1 may not start due to insufficient starting current.

In view of the above situation, a starting scheme for the boost switching power supply 200 shown in FIG. 2 is proposed according to an embodiment of the present invention to ensure that the boost switching power supply 200 can start, work, and shut down normally.

FIG. 4 shows an example circuit diagram of startup control circuit 400 for boost controller U2 shown in FIG. 2 . The startup control circuit 400 shown in FIG. 4 can control the boost controller U2 to restart after the PWM controller U1 is started, and can avoid the problem that the PWM controller U1 cannot restart due to insufficient startup current when the system is restarted.

FIG. 5 shows a flowchart of the startup control process implemented by the startup control circuit 400 shown in FIG. 4 . It can be seen from Figure 2, Figure 4, and Figure 5 that after the boost switching power supply 200 is powered on: the voltage VDD slope at the VDD pin of the boost controller U2 increases; when the VDD of the boost controller U2 When the voltage VDD at the pin is greater than the undervoltage lockout threshold UVLO_off_pwm of the PWM controller U2, the PWM controller U1 starts, and the SW pin of the boost controller U2 The voltage Vsw at the boost controller ramps up; when the voltage Vsw at the SW pin of the boost controller U2 is less than the startup voltage Vsw_on of the boost controller U2, the boost controller U2 does not start; when the SW pin of the boost controller U2 When the voltage Vsw at the pin is greater than the startup 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 undervoltage lockout turn-off threshold UVLO_off_bst of the boost transformer U2, the boost transformer U2 starts.

FIG. 6 shows a flow chart of the shutdown/power-down control process implemented by the startup control circuit shown in FIG. 4 . Combining 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 used to drive the power switch M on and off. signal, the voltage Vsw at the SW pin of the boost controller U2 ramps down, and the voltage VDD at the VDD pin of the boost controller U2 is maintained by the boost controller U2 for a while and then also ramps down; when the boost When the voltage VDD at the VDD pin of the 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 boost control When the voltage VDD at the VDD pin of the 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 U2 is less than the boost controller U2 When the shutdown voltage Vsw_off 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 the main discharge path is turned off, waiting for the boost. Switching power supply 200 restarts.

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

FIG. 7 shows an example circuit diagram of startup control circuit 700 for boost controller U2 shown in FIG. 2 . The difference between the startup control circuit 700 shown in FIG. 7 and the startup control circuit 400 shown in FIG. 4 is that when the boost switching power supply 200 is started, no matter the size of the input voltage Vin provided by the auxiliary winding Naux of the transformer T, as long as VDD of boost controller U2 When the voltage VDD at the pin is greater than the undervoltage lockout turn-off threshold UVLO_off_bst of the boost controller U2, a PG signal is generated; only 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 , the boost controller U2 starts. In this way, the PG signal generation circuit of the boost controller U2 is started first, and it only needs to wait for Vin>Vsw_on to work normally. There is no need to worry about whether VDD is greater than UVLO_off_bst when Vin>Vsw_on.

FIG. 8 shows an example circuit diagram of startup control circuit 800 for boost controller U2 shown in FIG. 2 . The startup control circuit 800 shown in FIG. 8 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 starting current.

FIG. 9 shows a flowchart of the startup control process implemented by the startup control circuit 700 shown in FIG. 8 . Combining Figure 2, Figure 8, and Figure 9, it can be seen that after the boost switching power supply 200 is powered on: the system input divided voltage Vac charges the capacitor C2 through the resistor Rstart. When the VDD pin of the boost controller U2 When the voltage VDD is greater than the conduction 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 boost controller U2 When the voltage VDD at the VDD pin is greater than the undervoltage lockout threshold UVLO_off_bst of the boost controller U2, the boost controller U2 starts and the power switch S1 turns off; the switch enable signal EN_SW=1, only the capacitor C1 Voltage controller U2 supplies power, and capacitor C2 no longer supplies power to boost controller U2; the system input divided voltage Vac continues to charge capacitor C2 through resistor Rstart, when the voltage VDD at the VDD pin of boost controller U2 is greater than the PWM controller When the undervoltage lockout shutdown threshold of U1 is UVLO_off_pwm, 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 When Vth1, switch back to the capacitor C2 to power the boost controller U2; when 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. .

The present invention may be implemented in other specific forms without departing from its spirit and essential characteristics. For example, the algorithms described in particular embodiments may be modified, and the system architecture may not without departing from the basic spirit of the invention. The present embodiments are therefore to be considered in all respects as illustrative and not restrictive, the scope of the invention being defined by the appended claims rather than the foregoing description, and the meanings and equivalents falling within the claims. All changes within the scope are therefore included in the scope of the invention.

U1: Pulse width modulation (PWM) controller

U2: Boost controller

UVLO_on_bst,UVLO_on_pwm: undervoltage lockout threshold

VDD: supply voltage

Vsw: voltage

Vsw_on: starting voltage

Claims (6)

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, and the switch control of the boost controller The voltage at the pin is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the supply voltage of the boost controller and the supply voltage of the pulse width modulation controller. , the boost controller is configured such that: the voltage at the chip power supply pin of the boost controller begins to increase after the boost switching power supply is powered on; and the switch control of the boost controller The voltage at the pin begins 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 switch of the pulse width modulation controller When the off threshold value is exceeded, the pulse width modulation controller starts; when the voltage at the switch control pin of the boost controller is greater than the startup voltage of the boost controller and the chip power supply pin of the boost controller When the voltage at the pin is greater than the undervoltage lockout threshold of the boost controller, the boost controller starts; the voltage at the switch control pin of the boost controller is in the boost switching power supply. It begins to decrease after a power outage or protective shutdown; and the voltage at the chip power supply pin of the boost controller drops to the point where the voltage at the switch control pin of the boost controller cannot maintain the boost controller. The voltage at the chip power supply pin remains unchanged and then begins to decrease, wherein when the voltage at the chip power supply pin of the boost controller is less than the undervoltage lockout opening threshold of the pulse width modulation controller, the The pulse width modulation controller is turned off when the voltage at the switch control pin of the boost controller is less than the shutdown voltage of the boost control chip and the voltage at the chip power supply pin of the boost controller is less than the When the undervoltage lockout threshold of the boost controller is reached, the boost controller is turned off. The boost controller as described in claim 1 is further configured to: When the voltage at the chip power supply pin of the boost controller is less than the discharge threshold, the voltage at the switch control pin of the boost controller is discharged. The boost controller of claim 1, further configured to: generate a power good signal after the boost controller is started; and trigger the switch control of the boost controller based on the power good signal. The voltage at the pin is discharged. The boost controller of claim 1, further configured to: generate a power supply 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. a good signal; and discharging the voltage at a switch control pin of the boost controller based on the power good signal. 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, and the switch control of the boost controller The voltage at the pin is provided by the auxiliary winding of the transformer. The voltage at the chip power supply pin of the boost controller is both the supply voltage of the boost controller and the supply voltage of the pulse width modulation controller. , the boost controller is configured such that: 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 chip power supply of the boost controller When the voltage at the pin 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, causing the switch control of the boost controller The voltage at the pin 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 When , the boost controller is started, the power switch is turned off, and the supply voltage of the boost controller is switched from the voltage at the chip power supply pin of the boost controller to the voltage of the boost controller. The voltage at the switch control pin, where the voltage at the chip supply pin of the boost controller is greater than the pulse width modulation controller When the undervoltage lockout shutdown threshold is reached, the pulse width modulation controller starts; the voltage at the chip power supply pin of the boost controller begins to decrease after the pulse width modulation controller starts; when the When the voltage at the chip power supply pin of the boost controller is less than the switching threshold, the power supply voltage of the boost controller is switched back to the boost controller from the voltage at the switch control pin of the boost controller. the voltage at the supply pin. A boost switching power supply includes the boost controller described in any one of claims 1 to 5.

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