Primary side self-powered driving chip and switching power supply starting circuit

Abstract

The invention provides a primary side self-powered driving chip and a switching power supply starting circuit. In the primary side self-powered driving chip, a driving control logic module is respectively connected with a power tube, a first MOS (Metal Oxide Semiconductor) tube and a second MOS tube; the power tube is connected with the Darlington tube, the chip power supply pin, the first MOS tube and the second MOS tube; and the Darlington tube and the second MOS tube are respectively connected to a chip internal power supply pin through a first diode and a second diode. The Darlington tube starting circuit is applied to a switching power supply, the starting current of a switching power supply driving chip is generated by utilizing the characteristic of high amplification factor of the Darlington tube and the turn-off leakage current of the power switch, the traditional mode of constructing a switching power supply starting circuit by depending on a resistor is successfully eliminated, and the area of the chip is saved. Meanwhile, by utilizing the characteristic of threshold voltage drop of an intrinsic collector-emitter of a Darlington tube, the starting circuit can be turned off by adopting a common enhanced MOS (Metal Oxide Semiconductor) tube, and the use requirements of an unconventional depletion MOS tube and a JFET (Junction Field Effect Transistor) are avoided, so that the cost of the whole switching power supply system is remarkably reduced.

Description

Technical Field

[0001] The present invention relates to the technical field of switching power supplies, and in particular to a primary side self-powered driving chip and a switching power supply starting circuit. Background Art

[0002] With the continuous advancement of science and technology and the continuous improvement of application requirements, switching power supply control chips are also constantly developing and innovating, and continue to move towards high efficiency and low power consumption, high integration and miniaturization. The traditional structure of the switching power supply system usually contains three windings: the primary winding, the secondary winding and the auxiliary winding. Among them, the primary winding and the secondary winding are responsible for realizing the isolation and energy transmission of the power supply, while the auxiliary winding is mainly used to provide VDD power supply for the chip and perform some protection detection functions. Patent CN106059279A proposes an innovative self-powered technology. In this technology, in each control cycle of the switch, the main switch is turned off first, and then the secondary switch is turned off with a delay. This design allows part of the current to flow to the internal power supply VDD for charging. However, this structure needs to rely on a startup resistor to ensure the first turn-on of the switch tube. But the problem is that once the power supply system starts to work normally, this startup resistor will lose its function and consume power, resulting in an increase in the standby power consumption of the power supply system. Therefore, an additional switch is required to turn it off. This additional switch needs to remain on without a control signal, and only JFET and depletion-mode MOS tubes can achieve this function, which undoubtedly increases the number of devices and thus increases the cost. What's more troublesome is that some BCD (Bipolar-CMOS-DMOS) platforms do not provide these specific devices. This makes the universality of this solution problematic. At the same time, the resistance of the startup resistor is usually between one million ohms and ten million ohms, which greatly occupies the chip area.

[0003] Therefore, it is necessary to provide a simple and efficient chip power-on startup technology. Summary of the invention

[0004] In order to solve the above technical problems, the present invention provides a primary side self-powered driving chip and a switching power supply starting circuit.

[0005] The present invention provides a primary side self-powered driving chip, comprising: a driving control logic module, a power tube, a Darlington tube, a first MOS tube, a second MOS tube, a first diode, and a second diode;

[0006] The first control end of the drive control logic module is electrically connected to the base of the power tube, the second control end is electrically connected to the gate of the first MOS tube, the third control end is electrically connected to the gate of the second MOS tube, the ground end is electrically connected to the source of the first MOS tube and the ground pin of the chip, the working voltage end is electrically connected to the cathode of the first diode, the cathode of the second diode, and the internal power pin of the chip, and the feedback end is electrically connected to the feedback pin of the chip;

[0007] The collector of the power tube is electrically connected to the collector of the Darlington tube and the chip power supply pin, and the emitter thereof is electrically connected to the base of the Darlington tube, the drain of the first MOS tube, and the drain of the second MOS tube;

[0008] The emitter of the Darlington transistor is electrically connected to the anode of the first diode;

[0009] The source electrode of the second MOS tube is electrically connected to the anode electrode of the second diode;

[0010] When the chip power supply pin is initially powered on, the shutdown current of the power tube is amplified by the Darlington tube and then output to the internal power supply pin of the chip, so that the internal power supply pin of the chip quickly provides a normal working voltage under the action of the external charging circuit;

[0011] After the internal power pin of the chip provides a normal operating voltage, the drive control logic module controls the power tube and the second MOS tube to be turned on, and the Darlington tube to be turned off, and the power supply voltage on the chip power supply pin is output to the internal power pin of the chip through the power tube and the second MOS tube.

[0012] In a possible implementation, the Darlington transistor is of NPN type.

[0013] In a possible implementation, the Darlington transistor includes a first NPN transistor and a second NPN transistor;

[0014] The base of the first NPN transistor serves as the base of the Darlington transistor, the collector of the first NPN transistor is electrically connected to the collector of the second NPN transistor and serves as the collector of the Darlington transistor, and the emitter of the first NPN transistor is electrically connected to the base of the second NPN transistor;

[0015] The emitter of the second NPN transistor serves as the emitter of the Darlington transistor.

[0016] In a possible implementation, the drive control logic module is a PWM drive logic module.

[0017] In a possible implementation, the power tube is of NPN type.

[0018] In a possible implementation manner, the first MOS transistor is an NMOS transistor.

[0019] In a possible implementation manner, the second MOS transistor is an NMOS transistor.

[0020] The present invention also provides a switching power supply startup circuit, comprising: a charging capacitor and the primary side self-powered driving chip as described above;

[0021] One end of the charging capacitor is electrically connected to the chip ground pin, and the other end of the charging capacitor is electrically connected to the chip internal power pin.

[0022] In a possible implementation, the switching power supply startup circuit further includes a transformer;

[0023] One end of the primary winding of the transformer is electrically connected to the chip power supply pin, and one end of the auxiliary winding is electrically connected to the chip feedback pin;

[0024] The other end of the primary winding serves as a voltage input end;

[0025] The other end of the auxiliary winding is electrically connected to the chip ground pin and grounded.

[0026] In a possible implementation, the switching power supply startup circuit further includes a rectifier diode and a filter capacitor;

[0027] The positive electrode of the rectifier diode is electrically connected to one end of the secondary winding of the transformer, and the negative electrode thereof is electrically connected to one end of the filter capacitor and serves as a voltage output end;

[0028] The other end of the secondary winding is electrically connected to the other end of the filter capacitor and is grounded.

[0029] The technical solution provided by the present invention has at least the following beneficial effects:

[0030] By using the shutdown current of the power tube as the starting current, the use of starting resistance is avoided, and a simpler and more efficient starting mechanism is achieved; by using the Darlington tube to amplify the starting current, the starting time of the circuit is shortened, and the fast startup of the switching power supply chip can be achieved; through the conventional depletion-type MOS tube and the inherent driving collector-emitter voltage drop property of the Darlington tube, a simple shutdown of the starting circuit can be achieved. BRIEF DESCRIPTION OF THE DRAWINGS

[0031] Figure 1 A schematic diagram of the structure of a traditional primary-side self-powered driver chip provided by an embodiment of the present invention;

[0032] Figure 2A schematic diagram of the structure of a conventional optimized primary side self-powered driver chip with startup resistor turned off provided in an embodiment of the present invention;

[0033] Figure 3 A schematic diagram of the structure of a primary side self-powered driver chip provided by an embodiment of the present invention;

[0034] In the attached drawings, 10 is a drive control logic module; 20 is a Darlington transistor. DETAILED DESCRIPTION

[0035] In order to deepen the understanding of the present invention, the present invention will be further described in detail below with reference to the accompanying drawings and embodiments. The embodiments are only used to explain the present invention and do not limit the protection scope of the present invention.

[0036] Please refer to Figure 1 and Figure 2 , showing the circuit structure of the traditional primary side self-powered driver chip. Figure 1 In the switching power supply system, there are three windings: primary winding, secondary winding and auxiliary winding. Among them, the primary winding and secondary winding are responsible for realizing power isolation and energy transmission, while the auxiliary winding is mainly used to provide VDD power supply for the chip and perform some protection detection functions. Figure 1 The structure needs to rely on a starting resistor to ensure the first conduction of the switch tube. After the power system starts to work normally, the starting resistor still consumes power, resulting in an increase in the standby power consumption of the power system. Figure 2 In the circuit, an additional switch is set to turn off the startup resistor. This additional switch needs to remain in the on state without a control signal, and only JFET and depletion-type MOS tubes can achieve this function, which undoubtedly increases the number of components and increases the cost. At the same time, the resistance of the startup resistor is usually between one million ohms and ten million ohms, which greatly occupies the chip area.

[0037] Please refer to Figure 3 The present invention provides a primary side self-powered driver chip, including: a drive control logic module 10, a power tube K, a Darlington tube 20, a first MOS tube M1, a second MOS tube M2, a first diode D1, and a second diode D2;

[0038] The first control terminal of the drive control logic module 10 is electrically connected to the base of the power tube K, the second control terminal is electrically connected to the gate of the first MOS tube M1, the third control terminal is electrically connected to the gate of the second MOS tube M2, the ground terminal is electrically connected to the source of the first MOS tube M1 and the chip ground pin GND, the working voltage terminal is electrically connected to the cathode of the first diode D1, the cathode of the second diode D2, and the chip internal power pin VDD, and the feedback terminal is electrically connected to the chip feedback pin FB;

[0039] The collector of the power tube K is electrically connected to the collector of the Darlington tube 20 and the chip power supply pin VCC, and the emitter thereof is electrically connected to the base of the Darlington tube 20, the drain of the first MOS tube M1, and the drain of the second MOS tube M2;

[0040] The emitter of the Darlington transistor 20 is electrically connected to the anode of the first diode D1;

[0041] The source of the second MOS tube M2 is electrically connected to the anode of the second diode D2;

[0042] When the chip power supply pin VCC is initially powered on, the shutdown current of the power tube K is amplified by the Darlington tube 20 and then output to the chip internal power supply pin VDD, so that the chip internal power supply pin VDD quickly provides a normal working voltage under the action of the external charging circuit;

[0043] After the internal power supply pin VDD of the chip provides a normal operating voltage, the drive control logic module 10 controls the power tube K and the second MOS tube M2 to be turned on, and the Darlington tube 20 is turned off, and the power supply voltage on the chip power supply pin VCC is output to the internal power supply pin VDD of the chip through the power tube K and the second MOS tube M2.

[0044] In this embodiment, the drive control logic module 10 adopts a conventional drive control module, such as a PWM drive logic module. The power tube K adopts a conventional model and is used as a switch tube. The Darlington tube 20 adopts a conventional structure, and the specific number of transistor stacking layers and stacking method can be selected according to actual needs. The first MOS tube M1 and the second MOS tube M2 are conventional MOS tubes, such as enhanced MOS tubes. The first diode D1 and the second diode D2 are conventional diodes. In the specific implementation, the primary self-powered driver chip utilizes the high current gain effect of the Darlington tube 20, and fully utilizes the turn-off current of the power tube K as a switch to obtain a larger startup current, which saves chip area and avoids the use of uncommon devices. At the same time, due to the inherent multiple collector-emitter voltage drop properties of the Darlington tube 20, the startup current can be turned off after power-on through conventional enhanced MOS tube control, thereby reducing static power consumption.

[0045] It should be pointed out that the present invention makes full use of the closing principle of the Darlington tube. For example: on the one hand, from the perspective of current amplification, when the second MOS tube M2 is turned off, the leakage current of the power tube K is amplified by the Darlington tube 20, and then passes through the first diode D13, and then is supplied to the VDD pin of the chip, that is, the internal power pin VDD of the chip. On the other hand, since the Darlington tube 20 needs to have a threshold voltage to work, when the Darlington tube 20 is composed of two NPN transistors in cascade, there will be a voltage drop of 2Vbe, about 1.4V, from the first base to the output emitter. When the second MOS tube M2 is turned on, the voltage drop through the drain-source level of the second MOS tube M2 may be only a few millivolts. At this time, the leakage current of the power tube K will go through the circuit with a smaller voltage drop, that is, from the second MOS tube M2 through the second diode D2 to the VDD pin of the chip, which is equivalent to the Darlington tube 20 being turned off.

[0046] In a specific embodiment, in the power-off state, the drive control logic module 10 is in a non-working state, and its first control terminal, the second control terminal, the third control terminal and other control terminals do not output control signals. When the voltage input terminal VIN is initially powered on, since the working voltage terminal of the drive control logic module 10 cannot immediately obtain an effective working voltage, its first control terminal, the second control terminal, the third control terminal and other control terminals still cannot output effective control signals. At this time, the power tube K and the first MOS tube M1 have no driving signals, and the power tube K and the first MOS tube M1 are both in the power-off state. The turn-off current of the power tube K is at the micro-ampere-ampere level, while the turn-off level of the first MOS tube M1 is usually at the nano-ampere level. The mismatch current of the power tube K and the first MOS tube M1 is amplified to the hundred micro-ampere level through the Darlington tube 20, and the power supply pin VDD inside the chip is charged through the first diode D1. When the power supply pin VDD inside the chip provides a normal operating voltage, that is, the chip is powered on successfully, the drive control logic module 10 works normally, the drive control logic module 10 sends a signal to the second MOS tube M2 through the third control terminal, turns on the second MOS tube M2, and the Darlington tube 20, that is, the Darlington start-up loop, is closed due to the inherent voltage drop. The drive control logic module 10 sends a signal to the power tube K through the first control terminal, the power tube K is turned on, and the primary side self-powered drive chip enters the self-powered mode.

[0047] In a possible implementation, the Darlington transistor 20 is of NPN type.

[0048] In a possible implementation, the Darlington transistor 20 includes a first NPN transistor Q1 and a second NPN transistor Q2;

[0049] The base of the first NPN transistor Q1 serves as the base of the Darlington transistor 20, the collector thereof is electrically connected to the collector of the second NPN transistor Q2 and serves as the collector of the Darlington transistor 20, and the emitter thereof is electrically connected to the base of the second NPN transistor Q2;

[0050] The emitter of the second NPN transistor Q2 serves as the emitter of the Darlington transistor 20 .

[0051] In this embodiment, the first NPN transistor Q1 and the second NPN transistor Q2 are conventional NPN transistors. Since the Darlington transistor 20 is composed of the first NPN transistor Q1 and the second NPN transistor Q2, the Darlington transistor 20 has a 2-fold collector-emitter voltage drop property, and is controlled by a conventional enhanced MOS transistor. After power-on, the Darlington transistor 20, i.e., the Darlington startup loop, is closed due to the inherent voltage drop (approximately equal to 1.2V), thereby shutting off the startup current, thereby reducing static power consumption.

[0052] In a possible implementation, the drive control logic module 10 is a PWM drive logic module.

[0053] In this embodiment, the PWM driving logic module adopts a conventional PWM driving module used for driving chips in switching power supplies.

[0054] In a possible implementation, the power tube K is of NPN type.

[0055] In a possible implementation manner, the first MOS transistor M1 is an NMOS transistor.

[0056] In a possible implementation manner, the second MOS transistor M2 is an NMOS transistor.

[0057] The present invention also provides a switching power supply startup circuit, comprising: a charging capacitor C1 and the primary side self-powered driving chip as described above;

[0058] One end of the charging capacitor C1 is electrically connected to the chip ground pin GND, and the other end thereof is electrically connected to the chip internal power pin VDD.

[0059] In this embodiment, the charging capacitor C1 is a conventional capacitor, which is used to provide a startup voltage for the power supply pin VDD inside the chip.

[0060] In a possible implementation, the switching power supply startup circuit further includes a transformer T;

[0061] One end of the primary winding NP of the transformer T is electrically connected to the chip power supply pin VCC, and one end of the auxiliary winding NA thereof is electrically connected to the chip feedback pin FB;

[0062] The other end of the primary winding NP serves as a voltage input end VIN;

[0063] The other end of the auxiliary winding FB is electrically connected to the chip ground pin GND and grounded.

[0064] In this embodiment, the transformer T adopts a conventional type.

[0065] In a possible implementation, the switching power supply startup circuit further includes a rectifier diode D3 and a filter capacitor C2;

[0066] The positive electrode of the rectifier diode D3 is electrically connected to one end of the secondary winding NS of the transformer T, and the negative electrode thereof is electrically connected to one end of the filter capacitor C2 and serves as a voltage output terminal VOUT;

[0067] The other end of the secondary winding NS is electrically connected to the other end of the filter capacitor C2 and is grounded.

[0068] In this embodiment, the rectifier diode D3 and the filter capacitor C2 are both conventional types.

[0069] The above embodiments should not limit the present invention in any way, and any technical solutions obtained by equivalent replacement or equivalent conversion shall fall within the protection scope of the present invention.

Claims

1. A primary side self-powered driver chip, characterized in that: include: Drive control logic module, power tube, Darlington tube, first MOS tube, second MOS tube, first diode, second diode; The first control end of the drive control logic module is electrically connected to the base of the power tube, the second control end is electrically connected to the gate of the first MOS tube, the third control end is electrically connected to the gate of the second MOS tube, the ground end is electrically connected to the source of the first MOS tube and the ground pin of the chip, the working voltage end is electrically connected to the cathode of the first diode, the cathode of the second diode, and the internal power pin of the chip, and the feedback end is electrically connected to the feedback pin of the chip; The collector of the power tube is electrically connected to the collector of the Darlington tube and the chip power supply pin, and the emitter thereof is electrically connected to the base of the Darlington tube, the drain of the first MOS tube, and the drain of the second MOS tube; The emitter of the Darlington transistor is electrically connected to the anode of the first diode; The source electrode of the second MOS tube is electrically connected to the anode electrode of the second diode; When the chip power supply pin is initially powered on, the shutdown current of the power tube is amplified by the Darlington tube and then output to the internal power supply pin of the chip, so that the internal power supply pin of the chip quickly provides a normal working voltage under the action of the external charging circuit; After the internal power pin of the chip provides a normal operating voltage, the drive control logic module controls the power tube and the second MOS tube to be turned on, and the Darlington tube to be turned off, and the power supply voltage on the chip power supply pin is output to the internal power pin of the chip through the power tube and the second MOS tube.

2. The primary side self-powered driver chip according to claim 1, characterized in that: The Darlington tube is of NPN type.

3. The primary side self-powered driver chip according to claim 2, characterized in that: The Darlington transistor includes a first NPN transistor and a second NPN transistor; The base of the first NPN transistor serves as the base of the Darlington transistor, the collector of the first NPN transistor is electrically connected to the collector of the second NPN transistor and serves as the collector of the Darlington transistor, and the emitter of the first NPN transistor is electrically connected to the base of the second NPN transistor; The emitter of the second NPN transistor serves as the emitter of the Darlington transistor.

4. The primary side self-powered driver chip according to claim 1, characterized in that: The drive control logic module is a PWM drive logic module.

5. The primary side self-powered driver chip according to claim 1, characterized in that: The power tube is of NPN type.

6. The primary side self-powered driver chip according to claim 1, characterized in that: The first MOS tube is an NMOS tube.

7. The primary side self-powered driver chip according to claim 1, characterized in that: The second MOS tube is an NMOS tube.

8. A switching power supply starting circuit, characterized in that: include: A charging capacitor and a primary side self-powered driver chip as claimed in claim 1; One end of the charging capacitor is electrically connected to the chip ground pin, and the other end of the charging capacitor is electrically connected to the chip internal power pin.

9. The switching power supply startup circuit according to claim 8, characterized in that: Also includes transformers; One end of the primary winding of the transformer is electrically connected to the chip power supply pin, and one end of the auxiliary winding is electrically connected to the chip feedback pin; The other end of the primary winding serves as a voltage input end; The other end of the auxiliary winding is electrically connected to the chip ground pin and grounded.

10. The switching power supply startup circuit according to claim 9, characterized in that: It also includes rectifier diodes and filter capacitors; The positive electrode of the rectifier diode is electrically connected to one end of the secondary winding of the transformer, and the negative electrode thereof is electrically connected to one end of the filter capacitor and serves as a voltage output end; The other end of the secondary winding is electrically connected to the other end of the filter capacitor and is grounded.

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