Power supply control chip, flyback AC-DC circuit and power supply

Abstract

The invention belongs to the technical field of flyback power supplies, and particularly provides a power supply control chip, a flyback AC-DC circuit and a power supply, and the power supply control chip integrates a high-voltage power tube, a low-voltage power tube, a voltage detection unit, a current sampling unit, a constant-voltage constant-current unit and a logic control unit, and does not need an external starting circuit and a VCC power supply circuit. An external sampling circuit is not needed, an Iset pin is provided, and power is set through an external resistor; when the transformer with double windings is adopted, an auxiliary winding is not needed, on the basis of simplifying a system circuit and optimizing system cost, chip functions of output voltage detection, input overvoltage and undervoltage protection and the like are achieved, zero-cross detection of inductive current is also achieved, the effect that a power tube is switched on when HV resonance voltage reaches the valley bottom is achieved, and the service life of the power tube is prolonged. And high-efficiency power supply conversion is realized.

Description

Technical Field

[0001] The present application relates to the technical field of flyback power supplies, and in particular to a power control chip, a flyback AC-DC circuit and a power supply. Background Art

[0002] Among the topologies of small and medium power ACDC power supplies, flyback is the absolute mainstream. Due to the fierce competition in the power supply market, the design requirements for power ICs are getting higher and higher. Flyback power ICs need to continuously improve integration, reduce the number of peripheral components, reduce solution costs, and simplify system design.

[0003] Common flyback power supply IC peripheral circuits with internal integrated power switching devices such as Figure 1 As shown, IC1 integrates a flyback control circuit and a primary high-voltage power tube (the high-voltage power tube includes a high-voltage Darlington transistor and a high-voltage MOSFET). Among them, HV is the collector or drain of the high-voltage power tube, which is externally connected to the primary winding of the transformer and the RCD absorption circuit (R1, R2, C1, D1); CS is the emitter or source of the power tube, which is externally grounded through the current sampling resistor Rcs; VCC is the control IC power supply pin, which is externally connected to the start-up resistors R3 and R4, and the auxiliary winding power supply circuit (R5, D2); ZCD is the control IC detection pin, which is externally connected to R6 and R7 to detect the signal from the auxiliary winding after voltage division. The first function is to detect the zero crossing of the inductor current to achieve the valley bottom opening of the power tube, reduce switching losses and improve efficiency; the second function is to detect the output voltage and input voltage signal to achieve input over-voltage and under-voltage protection and output over-voltage and under-voltage protection; COMP is the control IC power control pin, which is externally connected to the output end of the optocoupler and a capacitor, and the input end of the optocoupler is connected to the secondary voltage sampling, and a closed-loop control is formed through the error amplifier circuit; GND is the IC reference ground.

[0004] In order to further simplify the peripheral circuits, the existing technical solutions usually include one or more of the following implementation cases:

[0005] (1) Integrated startup circuit (high voltage tube or high voltage resistor), no need Figure 1 R3 and R4 shown reduce the number of peripheral components and increase the complexity and cost (packaging cost and material cost) of the IC.

[0006] (2) Integrated current sampling circuit, the emitter or source of the internal high-voltage power tube is connected to the drain of the low-voltage MOSFET, and then the source of the low-voltage MOSFET is connected to the IC reference ground, reducing Figure 1 The use of Rcs in the circuit increases the design complexity and cost of the power tube.

[0007] (3) Integrated VCC power supply circuit, even without using external auxiliary winding power supply, reducing Figure 1The use of R5 and D2.

[0008] In summary, in the most simplified state of the existing technical solution, Figure 1 Based on the circuit shown, the use of R3, R4, R5, D2, Rcs1, and Rcs2 is reduced. However, the existing solution still needs to sample the signal after the auxiliary winding is compressed to detect the zero crossing of the output inductor current, otherwise the valley voltage of the power tube cannot be turned on, affecting the power conversion efficiency. Therefore, the transformer needs to have three windings (primary winding, secondary winding, and auxiliary winding). Summary of the invention

[0009] The present application aims to solve at least one of the technical problems existing in the prior art, and proposes a power control chip, comprising:

[0010] A high-voltage power tube, wherein the high-voltage power tube is implemented by a Darlington tube with a two-stage composite triode structure, the collector of the high-voltage power tube is used to connect to the HV pin for controlling the on / off of the power supply, and the emitter is connected to the VCC pin through a power supply circuit;

[0011] A low-voltage power tube, wherein the drain of the low-voltage power tube is connected to the emitter of the high-voltage power tube, and the source of the low-voltage power tube is used to connect to the GND pin of the chip reference ground;

[0012] A voltage detection unit, the input end of which forms an FB pin for accessing a feedback voltage, is used to detect the output voltage and the resonance valley of the HV;

[0013] A current sampling unit, wherein an input end of the current sampling unit is connected to the low-voltage power tube and is used to detect the current flowing through the high-voltage power tube and the low-voltage power tube;

[0014] A constant voltage and constant current unit, whose input end is respectively connected to the output of the voltage detection unit and the current sampling unit, and whose output end is connected to the logic control unit to output a constant voltage and constant current signal;

[0015] A logic control unit, whose input ends are respectively connected to the voltage detection unit and the constant voltage and constant current unit, and is used to control the high-voltage power tube and the low-voltage power tube according to the resonance valley detection signal and the constant voltage and constant current signal. The input ends of the high-voltage power tube and the low-voltage power tube are both connected to the output end of the logic control unit through a driving circuit.

[0016] Preferably, the chip further comprises a startup circuit, and the startup circuit is connected to the HV pin and the input end of the high voltage power tube.

[0017] Preferably, the current sampling unit is provided with an Iset pin for setting chip power, and the Iset pin is connected to the input end of the current sampling unit.

[0018] Preferably, the voltage detection unit has a function of input voltage detection for input over-voltage and under-voltage protection.

[0019] The present invention also provides a flyback AC-DC circuit, comprising the power control chip, a DC source, a transformer, an RCD absorption circuit, and a secondary synchronous rectification circuit;

[0020] The HV pin of the power control chip is connected to the positive pole of the DC source, the opposite-name end of the primary winding of the transformer is connected to the negative pole of the DC source, the same-name end of the primary winding of the transformer is connected to the GND pin of the power control chip, the RCD absorption circuit is connected in parallel to the two ends of the primary winding, the FB pin of the power control chip collects the primary winding voltage signal of the transformer for valley detection and input and output voltage detection, and the secondary synchronous rectification circuit is connected to the secondary winding of the transformer.

[0021] The present invention also provides a flyback AC-DC circuit, comprising the power control chip, a DC source, a transformer, an RCD absorption circuit, and a secondary synchronous rectification circuit;

[0022] The same-name end of the primary winding of the transformer is connected to the positive electrode of the DC source, the GND pin of the power control chip is connected to the negative electrode of the DC source, the opposite-name end of the primary winding of the transformer is connected to the HV pin of the power control chip, and the RCD absorption circuit is connected in parallel to both ends of the primary winding;

[0023] The FB pin of the power control chip collects the transformer auxiliary winding voltage signal for valley detection and input and output voltage detection, and the secondary synchronous rectification circuit is connected to the secondary winding of the transformer.

[0024] The present invention also provides a power supply, which is controlled by the flyback AC-DC circuit as described above.

[0025] Beneficial effects: The present invention provides a power control chip, a flyback circuit and a power supply. The power control chip integrates a high-voltage power tube, a low-voltage power tube, a voltage detection unit, a current sampling unit, a constant voltage and constant current unit, and a logic control unit. No external startup circuit and VCC power supply circuit are required; no external sampling circuit is required, an Iset pin is provided, and the power is set by an external resistor; when a dual-winding transformer is used, no auxiliary winding is required. On the basis of simplifying the system circuit and optimizing the system cost, it not only realizes chip functions such as output voltage detection and input over- and under-voltage protection, but also realizes zero-crossing detection of the inductor current, thereby achieving the effect of turning on the power tube when the HV resonant voltage reaches the bottom, thereby realizing high-efficiency power conversion. BRIEF DESCRIPTION OF THE DRAWINGS

[0026] Figure 1A circuit diagram of a flyback power supply of a commonly used integrated power switch tube provided in the background technology of this application;

[0027] Figure 2 A block diagram of the internal design principle of the power control chip provided in the embodiment of the present application;

[0028] Figure 3 The internal schematic diagram of the power control chip provided in the embodiment of the present application;

[0029] Figure 4 A schematic diagram of a flyback power supply provided in an embodiment of the present application in a high-side application;

[0030] Figure 5 A schematic diagram of a flyback power supply provided in an embodiment of the present application in a low-side application. DETAILED DESCRIPTION

[0031] In order to enable those skilled in the art to better understand the technical solution of the present application, the present application is further described in detail below in conjunction with the accompanying drawings and specific implementation methods.

[0032] Unless otherwise defined, the technical terms or scientific terms used in this application should be understood by people with ordinary skills in the field to which this application belongs. The "first", "second" and similar words used in this application are not any order, quantity or importance, but are only used to distinguish different components. Similarly, similar words such as "one", "one" or "the" are not limited to quantity, but are at least one. "Including" or "including" and similar words mean that the elements or objects appearing before the word cover the elements or objects listed after the word and their equivalents, without excluding other elements or objects. "Connect" or "connected" and similar words are not limited to physical or mechanical connections, but can include electrical connections, whether direct or indirect. "Up", "down", "left", "right" and the like are only used for relative positional relationships. When the absolute position of the described target changes, the relative positional relationship may also change accordingly.

[0033] In each of the accompanying drawings, the same elements are represented by similar reference numerals. For the sake of clarity, the various parts in the accompanying drawings are not all drawn to scale. In addition, some well-known parts may not be shown in the drawings.

[0034] Many specific details of the present application are described below, such as component structures, materials, dimensions, processing techniques, and technologies, in order to more clearly understand the present application. However, as those skilled in the art will appreciate, the present application may be implemented without following these specific details.

[0035] Embodiment 1:

[0036] like Figure 2 and Figure 3 As shown, an embodiment of the present invention provides a power control chip, including:

[0037] A high-voltage power tube, wherein the high-voltage power tube is implemented by a Darlington tube with a two-stage composite triode structure, the collector of the high-voltage power tube is used to connect to the HV pin for controlling the on / off of the power supply, and the emitter is connected to the VCC pin through a power supply circuit;

[0038] A low-voltage power tube, wherein the drain of the low-voltage power tube is connected to the emitter of the high-voltage power tube, and the source of the low-voltage power tube is used to connect to the GND pin of the chip reference ground;

[0039] A voltage detection unit, the input end of which forms an FB pin for accessing a feedback voltage, is used to detect the output voltage and the resonance valley of the HV;

[0040] A current sampling unit, wherein an input end of the current sampling unit is connected to the low-voltage power tube and is used to detect the current flowing through the high-voltage power tube and the low-voltage power tube;

[0041] A constant voltage and constant current unit, whose input end is respectively connected to the output of the voltage detection unit and the current sampling unit, and whose output end is connected to the logic control unit to output a constant voltage and constant current signal;

[0042] A logic control unit, whose input ends are respectively connected to the voltage detection unit and the constant voltage and constant current unit, and is used to control the high-voltage power tube and the low-voltage power tube according to the resonance valley detection signal and the constant voltage and constant current signal. The input ends of the high-voltage power tube and the low-voltage power tube are both connected to the output end of the logic control unit through a driving circuit.

[0043] The current sampling unit is provided with an Iset pin for setting chip power, the Iset pin is connected to the input end of the current sampling unit, and the external system can control the chip overcurrent protection point by adjusting the resistor connected to the Iset pin.

[0044] Specifically refer to Figure 2It can be seen that the power control chip IC includes a logic control unit LOGIC, a voltage detection unit (Valley Detec, Vin Detec, Vout Detec), a constant voltage and current unit (CC / CV), a start-up circuit (Start up Resistor), a power supply circuit (diode), a current sampling unit (LEB), a drive circuit (Driver), a high-voltage power tube, and a low-voltage power tube (LV MOSFET). Among them, the control circuit includes a logic control unit, a voltage detection unit, a current sampling unit, a power control unit, a VCC self-powered circuit (i.e., a power supply circuit) and a drive circuit, etc. The power control chip IC is provided with an FB pin, an HV pin, a GND pin and a VCC pin outside, which are respectively connected to the voltage detection unit, the high-voltage power tube, the low-voltage power tube and the power supply circuit.

[0045] The connection relationship between each circuit module is as follows:

[0046] The voltage detection unit, the constant voltage and constant current unit, and the current sampling unit are all connected to the logic control unit for inputting signals to the logic control unit, and the input signals include: resonance valley detection signal, overvoltage signal, constant voltage and constant current signal. The high-voltage power tube and the low-voltage power tube are both connected to the output end of the logic control unit. The logic control outputs the control signal according to the resonance valley detection signal, the overvoltage signal, and the constant voltage and constant current signal, and the control signal ultimately controls the switches of the high-voltage power tube and the low-voltage power tube respectively through two drive circuits. A drive circuit and a start-up circuit are both connected to the high-voltage power tube, and the high-voltage power tube is also connected to the HV pin together with the other end of the start-up circuit. Another drive circuit is connected to the base of the low-voltage power tube, and the emitter of the low-voltage power tube is connected to the GND pin.

[0047] The voltage detection unit is used for valley detection and input and output over-voltage and under-voltage protection. The valley opening of the power tube is realized through the resonant valley detection circuit, which reduces the switching loss and improves the efficiency. The current sampling unit is used to detect whether the output is overcurrent. The logic control unit is used to output the control signal according to the resonant valley detection signal, the overvoltage signal, the overcurrent signal and the power regulation signal. The control signal finally controls the switch of the high-voltage power tube and the low-voltage power tube LV MOS through the driving circuit.

[0048] The chip further includes a startup circuit, which is connected to the HV pin and the input end of the high-voltage power tube. Figure 3 This is the schematic diagram of the power control chip. Figure 2 and Figure 3 Come and see, Figure 2 The high voltage power tube in the circuit is realized by a two-stage composite triode (i.e. Darlington triode). Figure 2 The startup circuit in the circuit is realized by the startup resistor. Figure 2The power supply circuit in is realized by a power supply diode.

[0049] The power control chip of this embodiment integrates a high-voltage power tube, a low-voltage power tube, a voltage detection unit, a current sampling unit, a constant voltage and constant current unit, and a logic control unit. No external startup circuit and VCC power supply circuit are required; no external sampling circuit is required, an Iset pin is provided, and the power is set by an external resistor; no auxiliary winding is required when a dual-winding transformer is used. On the basis of simplifying the system circuit and optimizing the system cost, it not only realizes chip functions such as output voltage detection and input over-voltage and under-voltage protection, but also realizes zero-crossing detection of the inductor current, thereby achieving the effect of turning on the power tube when the HV resonant voltage reaches the bottom, and realizing high-efficiency power conversion.

[0050] Embodiment 2:

[0051] This embodiment expands the application of the power control chip on the basis of the first embodiment, and specifically provides a flyback AC-DC circuit for the power control chip as described above, including the power control chip as described in the first embodiment, and also including a DC source, a transformer, an RCD absorption circuit and a secondary synchronous rectification circuit.

[0052] The HV pin of the power control chip is connected to the positive pole of the DC source, the opposite-name end of the primary winding of the transformer is connected to the negative pole of the DC source, the same-name end of the primary winding of the transformer is connected to the GND pin of the power control chip, the RCD absorption circuit is connected in parallel to the two ends of the primary winding, the FB pin of the power control chip collects the voltage signal of the primary winding of the transformer for valley detection and input and output voltage detection, and the secondary synchronous rectification circuit is connected to the secondary winding of the transformer. This flyback AC-DC circuit does not require an auxiliary winding (using a double-winding transformer), and on the basis of simplifying the system circuit and optimizing the system cost, it not only realizes comprehensive chip protection functions such as output over-voltage and under-voltage protection, input over-voltage and under-voltage protection, but also realizes zero-crossing detection of the inductor current, thereby achieving the effect of turning on the power tube at the valley voltage, and realizing high-efficiency power conversion.

[0053] Among them, the high-voltage power tube and the low-voltage power tube are placed on the high side of the primary winding, the external VCC is the power supply capacitor C2 of the power control chip; the Iset external resistor is used for overcurrent protection point setting.

[0054] The flyback power supply using the power control chip IC of the first embodiment can work in two modes: high side and low side. The typical application schematic diagrams are shown in FIG. Figure 4 and Figure 5 As shown. Figure 4Taking the high-side application as an example, the HV pin of the power control chip IC is internally connected to the GND pin, and the switching power tube is connected in series with the current detection low-voltage power tube, which is placed on the high side of the primary winding. The external VCC is the IC power supply capacitor C2, and the IC integrates the power supply circuit; the FB pin samples the transformer primary winding voltage signal for valley detection and input and output over-voltage and under-voltage protection; the Iset external resistor is used to set the system's overcurrent protection point.

[0055] Embodiment three:

[0056] This invention is based on the first embodiment, and expands the application of the power control chip. Specifically, a flyback AC-DC circuit for the power control chip as described above is provided, including a power control chip, a DC source, a transformer, an RCD absorption circuit, and a secondary synchronous rectification circuit;

[0057] The same-name end of the primary winding of the transformer is connected to the positive electrode of the DC source, the GND pin of the power control chip is connected to the negative electrode of the DC source, the opposite-name end of the primary winding of the transformer is connected to the HV pin of the power control chip, and the RCD absorption circuit is connected in parallel to both ends of the primary winding;

[0058] The FB pin of the power control chip collects the transformer auxiliary winding voltage signal for valley detection and input and output over-voltage and under-voltage protection. The input end of the secondary voltage sampling and error amplification circuit is connected to the secondary winding of the transformer.

[0059] This embodiment adopts the flyback power supply of the power control chip IC of the first embodiment. Figure 5 For example, unlike high-side applications, Figure 5 When the low-side is used as shown, an auxiliary winding is needed. After resistor voltage division, it is used for input and output voltage detection and inductor current zero-crossing detection through the ZCD pin. Specifically, it includes an auxiliary winding, a resistor R3 and a resistor R4 that are connected in series to form a loop, one end of the resistor R4 is grounded, the FB pin of the power control chip is connected to the resistor R13 and the resistor R14, and the HV pin of the power control chip is connected to the primary winding.

[0060] Embodiment 4:

[0061] This embodiment provides a power supply, which is controlled by the flyback AC-DC circuit in the above embodiment 2 or 3. The application circuit is greatly simplified, which can ensure comprehensive protection and high-efficiency conversion while reducing the implementation cost of the power supply.

[0062] It is to be understood that the above embodiments are merely exemplary embodiments used to illustrate the principles of the present application, but the present application is not limited thereto. For those skilled in the art, various modifications and improvements can be made without departing from the spirit and substance of the present application, and these modifications and improvements are also considered to be within the scope of protection of the present application.

Claims

1. A power control chip, characterized in that: include: A high-voltage power tube, wherein the high-voltage power tube is implemented by a Darlington tube with a two-stage composite triode structure, the collector of the high-voltage power tube is used to connect to the HV pin for controlling the on / off of the power supply, and the emitter is connected to the VCC pin through a power supply circuit; A low-voltage power tube, wherein the drain of the low-voltage power tube is connected to the emitter of the high-voltage power tube, and the source of the low-voltage power tube is used to connect to the GND pin of the chip reference ground; A voltage detection unit, the input end of which forms an FB pin for accessing a feedback voltage, is used to detect the output voltage and the resonance valley of the HV; A current sampling unit, wherein an input end of the current sampling unit is connected to the low-voltage power tube and is used to detect the current flowing through the high-voltage power tube and the low-voltage power tube; A constant voltage and constant current unit, whose input end is respectively connected to the output of the voltage detection unit and the current sampling unit, and whose output end is connected to the logic control unit to output a constant voltage and constant current signal; A logic control unit, whose input ends are respectively connected to the voltage detection unit and the constant voltage and constant current unit, and is used to control the high-voltage power tube and the low-voltage power tube according to the resonance valley detection signal and the constant voltage and constant current signal. The input ends of the high-voltage power tube and the low-voltage power tube are both connected to the output end of the logic control unit through a driving circuit.

2. The power control chip according to claim 1, characterized in that: The chip also includes a startup circuit, which is connected to the HV pin and the input end of the high-voltage power tube.

3. The power control chip according to claim 1, characterized in that: The current sampling unit is provided with an Iset pin for setting chip power, and the Iset pin is connected to the input end of the current sampling unit.

4. The power control chip according to claim 1, characterized in that: The voltage detection unit has a function of input voltage detection and is used for input over-voltage and under-voltage protection.

5. A flyback AC-DC circuit, characterized in that: Comprising a power control chip according to any one of claims 1 to 4, a DC source, a transformer, an RCD absorption circuit, and a secondary synchronous rectification circuit; The HV pin of the power control chip is connected to the positive pole of the DC source, the opposite-name end of the primary winding of the transformer is connected to the negative pole of the DC source, the same-name end of the primary winding of the transformer is connected to the GND pin of the power control chip, the RCD absorption circuit is connected in parallel to the two ends of the primary winding, the FB pin of the power control chip collects the primary winding voltage signal of the transformer for valley detection and input and output voltage detection, and the secondary synchronous rectification circuit is connected to the secondary winding of the transformer.

6. A flyback AC-DC circuit, characterized in that: Comprising a power control chip according to any one of claims 1 to 4, a DC source, a transformer, an RCD absorption circuit, and a secondary synchronous rectification circuit; The same-name end of the primary winding of the transformer is connected to the positive electrode of the DC source, the GND pin of the power control chip is connected to the negative electrode of the DC source, the opposite-name end of the primary winding of the transformer is connected to the HV pin of the power control chip, and the RCD absorption circuit is connected in parallel to both ends of the primary winding; The FB pin of the power control chip collects the transformer auxiliary winding voltage signal for valley detection and input and output voltage detection, and the secondary synchronous rectification circuit is connected to the secondary winding of the transformer.

7. A power supply, characterized in that: The power supply is controlled by a flyback AC-DC circuit as claimed in any one of claims 5 or 6.

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