TWI589108B - A control device for a switching power supply system and a switching power supply system - Google Patents

Description

Control device for switching power supply system, and switching power supply system

The present invention relates to the field of circuits, and more particularly to a control device for a switching power supply system and a switching power supply system.

The source-driven power switching power supply system is widely used in the fields of Light Emitting Diode (LED) lighting and mobile phone charging due to its simple structure and fast system startup.

Figure 1 is a circuit diagram of a typical BUCK-BOOST architecture source-driven power switching power supply system. In the system shown in Figure 1, the AC input voltage V _AC is rectified by the full-wave rectifier BD1, and a voltage Vbulk is generated across the capacitor C1; the GATE pin of the Pulse Width Modulation (PWM) controller passes. Resistor R1 is connected to voltage Vbulk and connected to ground through capacitor C4. Resistor R1 and capacitor C4 together form an RC charging circuit. During voltage Vbulk charging capacitor C4 through resistor R1, the voltage at the GATE pin of the PWM controller V _GATE gradually increases; there is a clamp circuit inside the PWM controller to maintain the voltage V _GATE at a high potential; when the gate voltage of the power switch M1 (ie, voltage V _GATE ) and the source voltage (ie, PWM control) When the voltage difference between the voltage V _SW at the SW pin of the device is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; at this time, the control SW pin inside the PWM controller is The connection of the power supply path of the VDD pin and the open switch are closed, and the PWM controller starts to charge the capacitor C3; when the voltage V _DD at the VDD pin of the PWM controller (ie, the supply voltage of the PWM controller) is higher than PWM Under-setting of the controller Protected voltage threshold, PWM control is started by controlling the power switch SW pin M1 is turned on and off, while the control pin to the SW power supply path VDD pin connection and disconnection of the switch is turned off, the voltage V _DD by a secondary Group winding L2 is provided.

In various conventional source-driven power switching power supply systems including the source-driven power switching power supply system of the BUCK-BOOST architecture shown in FIG. 1, additional power supply elements such as the auxiliary winding L2 are required. The device supplies power to a control device such as a PWM controller, so there are disadvantages such as high cost and low power supply efficiency.

The present invention provides a novel control device for a switching power supply system, and a switching power supply system.

A control device for a switching power supply system according to an embodiment of the invention includes a first pin, a second pin, a third pin, a fourth pin, and a clamp element connected between the first pin and the ground a module, a diode connected between the first pin and the second pin, a device power switch connected between the second pin and the third pin, and a second lead and a fourth lead connected a first switch between the feet, wherein: the first pin is connected to the input voltage of the control device through the first resistor, connected to the ground through the first capacitor, and connected to the gate of the system power switch in the switching power supply system, The second pin is connected to the source of the system power switch, the third pin is connected to the ground through the second resistor, and the fourth pin is connected to the ground through the second capacitor. After the control device is powered up, the voltage at the first pin gradually increases, is clamped by the clamp module, and is coupled to the second via the second pin and the fourth pin when the system power switch is turned on Capacitor charging; when the voltage on the second capacitor is higher than the undervoltage protection voltage threshold of the control device, the control device controls the turning on and off of the power switch of the system by controlling the power switch to be turned on and off, and is controlled by the first The closing and opening of the switch controls the charging and discharging of the second capacitor.

A control device for a switching power supply system according to an embodiment of the invention includes a first pin, a second pin, a third pin, a fourth pin, and a clamp element connected between the first pin and the ground a module, a diode connected between the first pin and the second pin, a diode connected between the first pin and the fourth pin, and connected to the second pin and the third pin a device power switch between the device and a first switch connected between the second pin and the fourth pin, wherein: the first pin is connected to a gate of a system power switch in the switching power supply system, and the second pin And system power switch The source is connected, the third pin is connected to the ground through the second resistor, and the fourth pin is connected to the input voltage of the control device through the first resistor, and is connected to the ground through the first capacitor. After the control device is powered up, the voltage at the first pin gradually increases with the voltage at the fourth pin, is clamped by the clamp module, and is passed through the second pin and the system when the system power switch is turned on. The four pins charge the first capacitor; when the voltage on the second capacitor is higher than the undervoltage protection voltage threshold of the control device, the control device controls the turning on and off of the system power switch by controlling the power switch to be turned on and off. And controlling the charging and discharging of the first capacitor by controlling the closing and opening of the first switch.

A switching power supply system according to an embodiment of the present invention includes the control device as described above.

In a switching power supply system including a control device according to an embodiment of the invention, the supply voltage to the control device is generated by controlling the turn-on and turn-off of the system power switch, so that no additional peripheral components or transformer windings need to be added. This makes the system of the switching power supply system including the control device according to the embodiment of the present invention low in cost and high in power conversion efficiency.

BD1‧‧‧ Full Wave Rectifier

Drain‧‧‧汲polar voltage

U1‧‧‧ clamp element module

Tblank‧‧‧ mask time

U2‧‧‧ drive module

Clamp‧‧‧ clamp

U3‧‧‧Detection Module

FUSE‧‧‧Fuse

U4‧‧‧ comparator

V _AC ‧‧‧AC input voltage

RC‧‧‧Charging circuit

PWM‧‧‧ pulse width modulation

L2‧‧‧Auxiliary winding

D1, D2, D3‧‧‧ diode

Vref‧‧‧reference voltage

300, 500, 600‧‧‧ control devices

R1, R2‧‧‧ resistance

C1, C3, C4, C5‧‧‧ capacitors

K1, K2‧‧‧ switch

GATE, SW, VDD, CS‧‧‧ pins

M1, M2‧‧‧ power switch

Vbulk, V _GATE , V _SW , V _DD , V _CS ‧‧‧ voltage

Other features, objects, and advantages of the present invention will become more apparent from the aspects of the appended claims.

1 is a circuit diagram of a source-driven power switching power supply system of a typical BUCK-BOOST architecture; FIG. 2 is a circuit diagram of a switching power supply system according to an embodiment of the present invention; and FIG. 3 is a diagram of a first embodiment according to the present invention. FIG. 4 is a circuit diagram of a control device of the switching power supply system shown in FIG. 2; FIG. 4 is a PWM signal in the control device shown in FIG. 3, a voltage signal at the CS pin, a voltage signal at the SW pin, and a timing chart of a control signal of the switch K1; Fig. 5 is a circuit diagram of a control device for the switching power supply system shown in Fig. 2 according to the second embodiment of the present invention; Fig. 6 is a circuit diagram of a control device for the switching power supply system shown in Fig. 2 according to the third embodiment of the present invention.

Example embodiments will now be described more fully with reference to the accompanying drawings. However, the example embodiments can be embodied in a variety of forms and should not be construed as being limited to the embodiments set forth herein; rather, these embodiments are provided to make the present invention more complete and complete, and to fully convey the concept of the example embodiments. Those skilled in the art. The same reference numerals in the drawings denote the same or similar structures, and thus their detailed description will be omitted.

Furthermore, the described features, structures, or characteristics may be combined in any suitable manner in one or more embodiments. In the following description, numerous specific details are set forth However, those skilled in the art will appreciate that the technical solution of the present invention may be practiced without one or more of the specific details, or other methods, components, materials, and the like may be employed. In other instances, well-known structures, materials, or operations are not shown or described in detail to avoid obscuring the invention.

In view of the above, the present invention proposes a novel control device and control method for a switching power supply system, and a switching power supply system. Hereinafter, a control device and a control method for a switching power supply system, and a switching power supply system according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings.

Fig. 2 is a circuit diagram of a switching power supply system according to an embodiment of the present invention. As can be seen from Fig. 1 and Fig. 2, the difference between the switching power supply system shown in Fig. 2 and the switching power supply system shown in Fig. 1 is that the PWM controller supply voltage V _DD is generated internally by the PWM controller. No additional transformer windings are needed. The control principle for the switching power supply system shown in Fig. 2 will be described in detail below with reference to Figs. 3 to 5.

It should be noted that the present invention is not limited to the switching power supply system of the BUCK-BOOST architecture. The control principles described below are also applicable to the switching power supply system such as FLY-BUCK, BUCK, and BOOST. Therefore, the devices related to the system architecture of the switching power supply system are no longer shown in Figures 3 and 5, but instead are rectified. The voltage Vbulk and the drain voltage Drain of the power switch M1.

Fig. 3 is a circuit diagram of a control device for the switching power supply system shown in Fig. 2 according to the first embodiment of the present invention. As shown in FIG. 3, the control device 300 includes a clamp module U1, a drive module U2, a diode D2, a diode D3, a switch K1, and a power switch M2; the external connection relationship of the control device 300 is as follows: The GATE pin of the control device 300 is connected to the voltage Vbulk through the resistor R1 and connected to the ground through the capacitor C4. The resistor R1 and the capacitor C4 together form an RC charging circuit; the GATE pin of the control device 300 is also connected to the gate of the power switch M1; The SW pin of the control device 300 is connected to the source of the power switch M1; the CS pin of the control device 300 is connected to the ground through a resistor R2; and the VDD pin of the control device 300 is connected to the ground through a capacitor C5. Here, the switch K1 is a switch that controls the connection and disconnection of the power supply path of the SW pin to the VDD pin inside the control device 300, and its initial state is a closed state.

After the switching power supply system including the control device 300 is powered on, the voltage Vbulk charges the capacitor C4 through the resistor R1, so that the voltage V _GATE at the GATE pin of the control device 300 gradually increases; the clamp module inside the control device 300 The high potential of the U1 sustain voltage V _GATE is not higher than the clamp voltage; when the gate voltage of the power switch M1 (ie, the voltage V _GATE ) and the source voltage (ie, the voltage V _SW at the SW pin of the control device 300) When the voltage difference between the voltage switches is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; at this time, since the control device 300 internally controls the connection of the SW pin to the power supply path of the VDD pin and The open switch K1 is closed, so the control device 300 starts charging the capacitor C5; when the voltage V _DD at the VDD pin of the control device 300 (ie, the power supply voltage of the control device 300) is higher than the internal setting of the control device 300 When the voltage threshold is undervoltage protection, the control device 300 starts to generate a PWM signal; the driving module U2 controls the turning on and off of the power switch M2 based on the PWM signal, thereby controlling the turning on and off of the power switch M1; the switch K1 is based on the PWM signal Closing or opening to the signal.

Here, when the PWM signal is at a high level, the power switch M2 is turned on, and the switch K1 is turned off; when the PWM signal is at a low level, the power switch M2 is turned off, the switch K1 is turned off; when the PWM signal is changed from the low level to the high level, the power switch M2 Change from turn off On, the switch K1 changes from closed to open. In order to make the main charge of the ringing voltage generated at the SW pin of the control device 300 when the power switch M2 is changed from on to off is supplied to the GATE pin of the control device 300, the PWM signal is changed from the high level to the low level switch. K1 does not immediately change from open to closed but after a period of masking.

Fig. 4 is a timing chart of the PWM signal, the voltage signal at the CS pin, the voltage signal at the SW pin, and the control signal of the switch K1 in the control device shown in Fig. 3. As can be seen in conjunction with Figures 3 and 4:

When the PWM signal is high, the power switch M2 is turned on, the switch K1 is turned off, and the voltage V _SW at the SW pin of the control device 300 is pulled down to the lower level by the power switch M2, that is, at the CS pin of the control device 300. The voltage V _CS , the diode D2 and the diode D3 are in an off state, and the voltage V _DD at the VDD pin of the control device 300 is held by the capacitor C5, and the voltage V _GATE at the GATE pin of the control device 300 is capacitive. C4 remains. At this time, since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on.

When the PWM signal changes from a high level to a low level, the power switch M2 is turned off, the switch K1 is still turned off, and a high ringing voltage due to LC resonance exists at the SW pin of the control device 300; at this time, since the switch K1 is still Disconnected, the ringing voltage is clamped by the clamp module U1 inside the control device 300 and the diode D2 clamp between the SW pin and the GATE pin; the excess charge corresponding to the ringing voltage flows into the GATE of the control device 300. The capacitor C4 connected to the pin; the portion of the ringer voltage higher than the clamp voltage of the clamp module U1 is discharged to the ground by the clamp module U1, and the voltage V _GATE at the GATE pin of the control device 300 is maintained at the clamp The clamp module U1 is near the clamp voltage. At this time, since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is lower than the conduction threshold of the power switch M1, the power switch M1 is turned off.

After the PWM signal changes from the high level to the low level for a period of time, the power switch M2 is still turned off, and the switch K1 is closed due to the voltage V _SW at the SW pin of the control device 300 and the voltage V at the VDD pin of the control device 300. The voltage difference between the _DDs is greater than the conduction threshold of the diode D3, so the diode D3 is turned on, and the voltage V _SW at the SW pin of the control device 300 is clamped by the diode D3 to the VDD of the control device 300. Near the voltage V _DD at the foot; when the supply voltage of the control device 300 (ie, the voltage V _DD ) drops lower due to power supply to the control device 300, the gate voltage V _GATE and the source voltage V of the power switch M1 The voltage difference between the _SW is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; the power switch M1 supplies its gate voltage V _GATE to the VDD pin of the control device 300 to make the voltage V _{DD is} maintained at a stable level.

Specifically, the voltage V _DD at the VDD pin of the control device 300 can be expressed by the following equation: VDD = V _GATE - V _GS - V _D3

Wherein, V _GATE is the voltage at the GATE pin of the control device 300 and is equal to the clamp voltage of the clamp module U1, V _GS is the conduction threshold of the power switch M1, and V _D3 is the conduction threshold of the diode D3.

In the control device 300 shown in Fig. 3, the power supply to the control device 300 is controlled by the internal control of the control device 300 without the need for an external auxiliary winding. In order to make the main charge of the ringing voltage generated at the SW pin of the control device 300 when the power switch M2 is turned off is supplied to the GATE pin of the control device 300, the control switch is turned on when the PWM signal changes from a high level to a low level. K1 is closed after the set mask time Tblank.

Fig. 5 is a circuit diagram of a control device for the switching power supply system shown in Fig. 2 according to the second embodiment of the present invention. As shown in FIG. 5, the control device 500 further includes a switch K2 and a detection, in addition to the clamp module U1, the drive module U2, the diode D2, the diode D3, the switch K1, and the power switch M2. Module U3, and comparator U4; the external connection relationship of the control device 500 is as follows: the GATE pin of the control device 500 is connected to the voltage Vbulk through the resistor R1 and connected to the ground through the capacitor C4, and the resistor R1 and the capacitor C4 together form an RC charging circuit. The GATE pin of the control device 500 is also connected to the gate of the power switch M1; the SW pin of the control device 500 is connected to the source of the power switch M1; the CS pin of the control device 500 is connected to the ground through the resistor R2; 500 VDD pin through capacitor C5 Connected to the ground. Here, the switch K1 is a switch that controls the connection and disconnection of the power supply path of the SW pin to the VDD pin inside the control device 500, and its initial state is a closed state; the switch K2 is a control GATE pin to the VDD inside the control device 500. The pin-powered switch has an initial state that is off.

After the switching power supply system including the control device 500 is powered up, the voltage Vbulk charges the capacitor C4 through the resistor R1, so that the voltage V _GATE at the GATE pin of the control device 500 is gradually increased; the clamp mode of the control device 500 is internal. The high potential of the group U1 sustain voltage V _GATE is not higher than the clamp voltage; when the gate voltage of the power switch M1 (ie, the voltage V _GATE ) and the source voltage (ie, at the SW pin of the control device 500) When the voltage difference between the voltages V _SW ) is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; at this time, since the control device 500 internally controls the power supply path from the SW pin to the VDD pin. The connected and disconnected switch K1 is closed, so the control device 500 starts charging the capacitor C5; when the voltage V _DD at the VDD pin of the control device 500 (ie, the supply voltage of the control device 500) is higher than the control device 500 When the undervoltage protection voltage threshold is set internally, the control device 500 starts to generate a PWM signal; the driving module U2 controls the turning on and off of the power switch M2 based on the PWM signal, thereby controlling the turning on and off of the power switch M1; the switch K1 is based on P The reverse signal of the WM signal is closed or opened.

Here, when the PWM signal is at a high level, the power switch M2 is turned on, and the switch K1 is turned off; when the PWM signal is at a low level, the power switch M2 is turned off, the switch K1 is turned off; when the PWM signal is changed from the low level to the high level, the power switch M2 From off to on, switch K1 changes from closed to open. In order to make the main charge of the ringing voltage generated at the SW pin of the control device 500 when the power switch M2 is turned off is supplied to the GATE pin of the control device 500, the switch K1 does not immediately turn when the PWM signal changes from a high level to a low level. It changes from open to closed, but after a period of masking, it changes from open to closed.

When the PWM signal is at a high level, the power switch M2 is turned on, the switch K1 is turned off, and the voltage V _SW at the SW pin of the control device 500 is pulled down to a lower level by the power switch M2, that is, at the CS pin of the control device 500. The voltage V _CS , so the diode D2 and the diode D3 are in the off state, the voltage V _DD at the VDD pin of the control device 500 is held by the capacitor C5, and the voltage V _GATE at the GATE pin of the control device 500 is Capacitor C4 is held. At this time, since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on.

When the PWM signal changes from a high level to a low level, the power switch M2 is turned off, the switch K1 is still turned off, and a high ringing voltage due to LC resonance exists at the SW pin of the control device 500; at this time, since the switch K1 is still Disconnected, the ringing voltage is clamped by the clamp module U1 inside the control device 500 and the diode D2 clamp between the SW pin and the GATE pin; the excess charge corresponding to the ringing voltage flows into the GATE of the control device 500. The capacitor C4 connected to the foot; the detecting module U3 detects the voltage V _GATE at the GATE pin of the control device 500, and outputs the detection result to the comparator U4; the comparator U4 is when the voltage V _{GATE is} higher than the reference voltage Vref The switch K2 that controls the connection to the VDD pin of the control device 500 is closed, and controls the switch K2 connected to the VDD pin of the control device 500 to be turned off when the voltage V _{GATE is} lower than the reference voltage Vref to set the ringing voltage higher than the reference voltage. The corresponding excess charge is supplied to the capacitor C5 via the pin VDD of the control device 500, thereby improving the power supply efficiency; the voltage V _GATE at the GATE pin of the control device 500 is maintained near the clamp voltage of the clamp module U1. . At this time, since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is lower than the conduction threshold of the power switch M1, the power switch M1 is turned off. Here, the reference voltage Vref may be a predetermined voltage that is greater than the voltage V _DD at the VDD pin of the control device 500 and smaller than the clamp voltage of the clamp module U1.

After the PWM signal changes from the high level to the low level for a period of time, the power switch M2 is still turned off, and the switch K1 is closed due to the voltage V _SW at the SW pin of the control device 500 and the voltage V at the VDD pin of the control device 500. The voltage difference between the _DDs is greater than the turn-on threshold of the diode D3, so the diode D3 is turned on, and the voltage V _SW at the SW pin of the control device 500 is pulled down by the diode D3 to the VDD pin of the control device 500. Near the voltage V _DD ; when the supply voltage of the control device 500 (ie, the voltage V _DD ) drops lower because of the power supply to the control device 500, the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW The voltage difference between the two is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; the power switch M1 supplies its gate voltage V _GATE to the VDD pin of the control device 500 to maintain the voltage V _DD At a stable level.

It can be seen that a control device (for example, control device 300) for a switching power supply system including a first pin (for example, a GATE pin) and a second pin (described in conjunction with FIGS. 3 to 5) is described. For example, a SW pin), a third pin (eg, a CS pin), a fourth pin (eg, a VDD pin), a clamp module connected between the first pin and ground (eg, Clamping element module U1), a diode connected between the first pin and the second pin (for example, diode D2), and a device power connected between the second pin and the third pin a switch (eg, power switch M2), and a first switch (eg, switch K1) coupled between the second pin and the fourth pin, wherein: the first pin passes the first resistor (eg, resistor R1) Connected to an input voltage of the control device (eg, voltage Vbulk), connected to ground through a first capacitor (eg, capacitor C4), and connected to a gate of a system power switch (eg, power switch M1) in the switching power supply system, The second pin is connected to the source of the system power switch, and the third pin is connected to the ground through a second resistor (for example, resistor R2). A second capacitor connected to ground via (e.g., capacitors C5). After the control device is powered up, the voltage at the first pin (eg, voltage V _GATE ) gradually increases, is clamped by the clamp module, and is passed through the second pin and the fourth when the system power switch is turned on. The pin charges the second capacitor; when the voltage on the second capacitor is higher than the undervoltage protection voltage threshold of the control device, the control device controls the turn-on and turn-off of the system power switch by controlling the power switch to be turned on and off. The charge and discharge of the second capacitor are controlled by controlling the closing and opening of the first switch. Here, the control device controls the turning on and off of the device power switch based on the first control signal (eg, the PWM signal), and controls the closing and opening of the first switch based on the reverse signal of the first control signal.

In some embodiments, the control device (eg, the control device 500) may further include a second switch (eg, the switch K2) connected between the first pin and the fourth pin, detecting the first pin The voltage detection module (for example, the detection module U3) and the comparison between the voltage detected by the detection module and a predetermined voltage (for example, the reference voltage Vref) A comparator (eg, comparator U4) that controls the closing and opening of the second control signal of the second switch is generated. Wherein, when the voltage detected by the detecting module is higher than the predetermined voltage, the second control signal is at a high level, and the second switch is closed; when the detected voltage of the detecting module is lower than a predetermined voltage, the second control The signal is at a low level and the second switch is open.

Fig. 6 is a circuit diagram of a control device for the switching power supply system shown in Fig. 2 according to the third embodiment of the present invention. As shown in FIG. 6, the control device 600 includes a clamp module U1, a drive module U2, a detection module U3, a comparator U4, a diode D2, a diode D3, a switch K1, and a switch K2. And the power switch M2 further includes a diode D4; and the external connection relationship of the control device 600 is as follows: the VDD pin of the control device 600 is connected to the voltage Vbulk through the resistor R1 and connected to the ground through the capacitor C5, and the resistor R1 is combined with the capacitor C4 Forming an RC charging circuit; the GATE pin of the control device 600 is connected to the gate of the power switch M1; the SW pin of the control device 600 is connected to the source of the power switch M1; and the CS pin of the control device 600 is connected to the ground through the resistor R2 . Here, the switch K1 is a switch that controls the connection and disconnection of the power supply path of the SW pin to the VDD pin inside the control device 600, and its initial state is a closed state; the switch K2 is a control GATE pin to the VDD inside the control device 600. The pin-powered switch has an initial state that is off.

After powering up the switching power supply system including the control device 600, the voltage Vbulk charges the capacitor C5 through the resistor R1, so that the voltage V _DD at the VDD pin of the control device 600 gradually increases; when the VDD pin of the control device 600 When the voltage V _DD (ie, the power supply voltage of the control device 600) is higher than the undervoltage protection voltage threshold set by the control device 600, the control device 600 starts generating the PWM signal; the driving module U2 controls the conduction of the power switch M2 based on the PWM signal. And turning off, thereby controlling the turning on and off of the power switch M1; the switch K1 is turned on or off based on the reverse signal of the PWM signal.

Here, when the PWM signal is at a high level, the power switch M2 is turned on, and the switch K1 is turned off; when the PWM signal is at a low level, the power switch M2 is turned off, the switch K1 is turned off; when the PWM signal is changed from the low level to the high level, the power switch M2 From off to on, switch K1 changes from closed to open. In order to control the device 600 when the power switch M2 is turned off The main charge of the ringing voltage generated at the SW pin is supplied to the GATE pin of the control device 600, and the switch K1 does not immediately change from open to closed but passes through a mask when the PWM signal changes from a high level to a low level. It will change from disconnected to closed after time.

Inside the control device 600, the VDD pin is connected to the GATE pin via a diode D4, and the voltage V _GATE at the GATE pin of the control device 600 is controlled by the voltage V _DD at its VDD pin. Specifically, the voltage V _GATE can be represented by the equation V _GATE =V _DD -D4, where D4 represents the conduction threshold of the diode D4.

When the PWM signal is high, the power switch M2 is turned on, the switch K1 is turned off, and the voltage V _SW at the SW pin of the control device 600 is pulled down to the lower level by the power switch M2, that is, at the CS pin of the control device 600. The voltage V _CS . At this time, the voltage V _DD at the VDD pin of the control device 600 is held by the capacitor C5, and the voltage V _GATE at the GATE pin of the control device 600 is clamped by the diode D4 to the vicinity of the voltage V _DD , the diode D2 And D3 is in the off state. Since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is greater than the conduction threshold of the power switch M1, the power switch M1 is turned on.

When the PWM signal changes from a high level to a low level, the power switch M2 is turned off, the switch K1 is still turned off, and a high ringing voltage due to LC resonance exists at the SW pin of the control device 600; at this time, since the switch K1 is still Disconnected, the ringing voltage is controlled by the clamp element module U1 inside the control device 600 and the diode D2 clamp element between the SW pin and the GATE pin; the excess charge corresponding to the ringing voltage flows into the GATE of the control device 600. feet; V _GATE voltage detection module detects U3 at pin GATE control device 600; comparator U4 when the voltage at pin V _GATE GATE control device 600 is lower than the reference voltage Vref, the control device 600 control The switch K2 connected to the VDD pin is disconnected, and the voltage V _GATE at the GATE pin of the control device 600 is clamped by the diode D4 to the voltage V _DD at the VDD pin of the control device 600, and the capacitor C5 is discharged. Powering the control device 600; when the voltage V _GATE at the GATE pin of the control device 600 is higher than the reference voltage Vref, the switch K2 that controls the connection with the VDD pin of the control device 600 is closed to turn the control device 600 the voltage V _GATE GATE pin charge director The control device 600 of the VDD pin, charging the capacitor C5, thereby improving the power supply efficiency; voltage V _GATE GATE pin if the control means 600 continues to rise to a higher element module U1 will be clamped thereto with clamp forceps Near the bit voltage. At this time, since the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW is lower than the conduction threshold of the power switch M1, the power switch M1 is turned off. Here, the reference voltage Vref may be a predetermined voltage that is greater than the voltage V _DD at the VDD pin of the control device 600 and less than the clamp voltage of the clamp module U1.

After the PWM signal changes from the high level to the low level for a period of time, the power switch M2 is still turned off, and the switch K1 is closed, when the voltage V _DD at the VDD pin of the control device 600 is lowered due to the power supply to the control device 600. The voltage difference between the voltage V _SW at the SW pin of the control device 600 and the voltage V _DD at the VDD pin of the control device 600 is greater than the conduction threshold of the diode D3, and the diode D3 is turned on, and the control device 600 The voltage V _SW at the SW pin is pulled down by the diode D3 to the voltage V _DD near the VDD pin of the control device 600, and the voltage difference between the gate voltage V _{GATE of the} power switch M1 and the source voltage V _SW The value is higher than the conduction threshold of the power switch M1, the power switch M1 is turned on and forms a source follower; the power switch M1 supplies its gate voltage V _GATE to the VDD pin of the control device 600 to maintain the voltage V _DD at a stable level .

It can be seen that a control device (eg, control device 600) is described in conjunction with FIG. 6, including a first pin (eg, a GATE pin), a second pin (eg, a SW pin), a third lead. a pin (eg, a CS pin), a fourth pin (eg, a VDD pin), a clamp module connected between the first pin and ground (eg, clamp module U1), connected a diode between the first pin and the second pin (for example, the diode D2), a diode connected between the first pin and the fourth pin (for example, the diode D4), a device power switch (eg, power switch M2) connected between the second pin and the third pin, and a first switch (eg, switch K1) connected between the second pin and the fourth pin, Wherein: the first pin is connected to the gate of the system power switch (for example, the power switch M1) in the switching power supply system, the second pin is connected to the source of the system power switch, and the third pin is passed through the second resistor (for example , the resistor R2) is connected to the ground, and the fourth pin is passed through the first resistor (for example, the resistor R1) It is connected to the input voltage of the control device and is connected to the ground through a first capacitor (for example, capacitor C5). After the control device is powered up, the voltage at the first pin gradually increases with the voltage at the fourth pin, is clamped by the clamp module, and is passed through the second pin and the system when the system power switch is turned on. The four pins charge the first capacitor; when the voltage on the second capacitor is higher than the undervoltage protection voltage threshold of the control device, the control device controls the turning on and off of the system power switch by controlling the power switch to be turned on and off. And controlling the charging and discharging of the first capacitor by controlling the closing and opening of the first switch.

In some embodiments, the control device (eg, the control device 600) may further include a second switch (eg, the switch K2) connected between the first pin and the fourth pin, detecting the first pin The voltage detecting module (for example, the detecting module U3) and the comparison result of the voltage detected by the detecting module and the predetermined voltage (for example, the reference voltage Vref) are generated to control the closing and opening of the second switch. A comparator of the second control signal (eg, comparator U4). Wherein, when the voltage detected by the detecting module is higher than the predetermined voltage, the second control signal is at a high level, and the second switch is closed; when the detected voltage of the detecting module is lower than a predetermined voltage, the second control The signal is at a low level and the second switch is open.

In various conventional source-driven power switching power supply systems including the source-driven power switching power supply system of the BUCK-BOOST architecture shown in FIG. 1, additional power supply elements such as the auxiliary winding L2 are required. The device supplies power to a control device such as a PWM controller, so there are disadvantages such as high cost and low power supply efficiency.

The control device according to the embodiment of the present invention can be widely applied to a plurality of switching power supply fields such as a power adapter, a mobile phone charger, and an LED illumination controlled by a source switch.

However, it is to be understood that the invention is not limited to the specific configurations and processes described above and illustrated in the drawings. Also, a detailed description of known method techniques is omitted herein for the sake of brevity. In the above embodiments, several specific steps have been described and illustrated as examples. However, the method of the present invention is not limited to the specific steps described and illustrated, and those skilled in the art can make various changes, modifications, and additions after the spirit of the present invention. Or change the order between the steps.

The invention may be embodied in other specific forms without departing from the spirit and essential characteristics. For example, the algorithms described in the specific embodiments can be modified, and the system architecture does not depart from the basic spirit of the invention. The present embodiments are to be considered in all respects as illustrative and not limiting, and the scope of the invention All changes in the scope of the invention are thus included in the scope of the invention.

300‧‧‧Control device

R1, R2‧‧‧ resistance

U1‧‧‧ clamp element module

M1, M2‧‧‧ power switch

U2‧‧‧ drive module

D2, D3‧‧‧ diode

K1‧‧‧ switch

C4, C5‧‧‧ capacitor

Drain‧‧‧汲polar voltage

Vbulk‧‧‧ voltage

PWM‧‧‧ pulse width modulation

Clamp‧‧‧ clamp

GATE, SW, VDD, CS‧‧‧ pins

Claims (11)

A control device for a switching power supply system includes a first pin, a second pin, a third pin, a fourth pin, a clamp module connected between the first pin and the ground, a diode connected between the first pin and the second pin, a device power switch connected between the second pin and the third pin, and a connection in the a first switch between the two pins and the fourth pin, wherein: the first pin is connected to an input voltage of the control device through a first resistor, connected to the ground through a first capacitor, and a gate connection of a system power switch in the switching power supply system, the second pin is connected to a source of the system power switch, and the third pin is connected to the ground through a second resistor, and the fourth pin passes The second capacitor is connected to the ground. After the control device is powered on, the voltage at the first pin is gradually increased, clamped by the clamp module, and when the system power switch is turned on. Charging the second capacitor via the second pin and the fourth pin, in the When the voltage on the capacitor is higher than the undervoltage protection voltage threshold of the control device, the control device controls the turning on and off of the power switch of the system by controlling the turning on and off of the power switch of the device, and by controlling The first switch is closed and opened to control charging and discharging of the second capacitor. The control device according to claim 1, wherein the control device controls on and off of the device power switch based on the first control signal, and controls the device based on the reverse signal of the first control signal The first switch is closed and opened. The control device of claim 2, wherein the first switch changes from closed to open when the first control signal changes from a low level to a high level, and the first control signal is The high level becomes the low level and changes from open to closed after a period of masking. The control device of claim 1, further comprising a second switch connected between the first pin and the fourth pin, detecting a voltage at the first pin a measuring module, and a comparator for controlling a second control signal for closing and opening the second switch based on a comparison result of the voltage detected by the detecting module and a predetermined voltage, wherein When the voltage detected by the detecting module is higher than the predetermined voltage, the second control signal is at a high level, and the second switch is closed, when the detecting module detects a low voltage At the predetermined voltage, the second control signal is at a low level and the second switch is turned off. The control device of claim 4, wherein the predetermined voltage is greater than a voltage at the fourth pin and less than a clamp voltage of the clamp module. A control device for a switching power supply system includes a first pin, a second pin, a third pin, a fourth pin, a clamp module connected between the first pin and the ground, a diode connected between the first pin and the second pin, a diode connected between the first pin and the fourth pin, connected to the second a device power switch between the pin and the third pin, and a first switch connected between the second pin and the fourth pin, wherein: the first pin and the first pin a gate of the system power switch in the switching power supply system, the second pin is connected to a source of the system power switch, the third pin is connected to the ground through a second resistor, and the fourth pin passes the a resistor is connected to the input voltage of the control device, and is connected to the ground through the first capacitor. After the control device is powered on, the voltage at the first pin follows the voltage at the fourth pin. Enlarged, clamped by the clamp module, and via the first when the system power switch is turned on The pin and the fourth pin charge the first capacitor, and when the voltage on the second capacitor is higher than an undervoltage protection voltage threshold of the control device, the control device controls the device power The switch is turned on and off to control the turning on and off of the system power switch, and the charging and discharging of the first capacitor is controlled by controlling the closing and opening of the first switch. The control device of claim 6, wherein the control device controls on and off of the device power switch based on the first control signal, and controls the station based on the reverse signal of the first control signal The first switch is closed and opened. The control device of claim 7, wherein the first switch is in the The first control signal changes from closed to open when changing from a low level to a high level, and changes from off to closed after a period of masking when the first control signal changes from a high level to a low level. The control device of claim 6, further comprising a second switch connected between the first pin and the fourth pin, detecting a voltage at the first pin a measuring module, and a comparator that controls a second control signal that controls closing and opening of the second switch based on a comparison result of the voltage detected by the detecting module and a predetermined voltage, wherein the detecting When the voltage detected by the module is higher than the predetermined voltage, the second control signal is at a high level, and the second switch is closed, when the voltage detected by the detecting module is lower than the predetermined voltage. The second control signal is at a low level and the second switch is turned off. The control device of claim 9, wherein the predetermined voltage is greater than a voltage at the fourth pin and less than a clamp voltage of the clamp module. A switching power supply system comprising the control device according to any one of claims 1 to 10.