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

Abstract

The utility model 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] This application relates to the field of flyback power supply technology, and in particular to a power control chip, a flyback AC-DC circuit, and a power supply. Background Technology

[0002] In the topology of low-to-medium power AC / DC power supplies, flyback converters dominate. Due to intense competition in the power supply market, the design requirements for power ICs are becoming increasingly stringent. Flyback power ICs need to continuously improve their integration, reduce the number of external components to lower the cost of the solution, and simplify system design.

[0003] Common external circuits for flyback power supply ICs with integrated power switching devices include: Figure 1 As shown, IC1 integrates a flyback control circuit and a primary-side high-voltage power transistor (the high-voltage power transistor includes a high-voltage Darlington transistor and a high-voltage MOSFET). HV is the collector or drain of the high-voltage power transistor, externally connected to the primary winding of the transformer and the RCD snubber circuit (R1, R2, C1, D1); CS is the emitter or source of the power transistor, externally grounded through the current sampling resistor Rcs; VCC is the power supply pin of the control IC, externally connected to the start-up resistors R3 and R4, and the auxiliary winding power supply circuit (R5, D2); ZCD is the detection pin of the control IC, externally connected to R6 and R7, detecting the signal from the auxiliary winding after voltage division. Its first function is to detect the inductor current crossing zero, realizing the valley turn-on of the power transistor, reducing switching losses and improving efficiency; its second function is to detect the output voltage and input voltage signal, realizing input over- and under-voltage protection and output over- and under-voltage protection; COMP is the power control pin of the control IC, externally connected to the output of the optocoupler and a capacitor. The input of the optocoupler is connected to the secondary voltage sampling, forming a closed-loop control through the error amplifier circuit; GND is the IC reference ground.

[0004] To further simplify the peripheral circuitry, existing technical solutions typically include one or more of the following implementation use cases:

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

[0006] (2) An integrated current sampling circuit connects the emitter or source of the internal high-voltage power transistor to the drain of the low-voltage MOSFET, and then connects the source of the low-voltage MOSFET to the IC reference ground, reducing... Figure 1 The use of RCS in the middle increases the design complexity and cost of power transistors.

[0007] (3) Integrated VCC power supply circuit, reducing the need for external auxiliary winding power supply even when no external auxiliary winding power supply is used. Figure 1The use of R5, D2.

[0008] In summary, in the simplest state of the prior art solution, Figure 1 The use of R3, R4, R5, D2 and Rcs1, Rcs2 is reduced based on the circuit shown. However, the existing solution still needs to sample the voltage after the auxiliary winding to detect the output inductor current zero crossing, otherwise it cannot achieve the valley voltage turn-on of the power tube, which affects the power conversion efficiency. Therefore, the transformer needs to have three windings (primary winding, secondary winding and auxiliary winding). SUMMARY

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

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

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

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

[0013] A current sampling unit, the input end of the current sampling unit is connected with 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, the input end is connected with the output of the voltage detection unit and the current sampling unit respectively, and the output end is connected with the logic control unit to output the constant voltage and constant current signal;

[0015] A logic control unit, the input end is connected with the voltage detection unit and the constant voltage and constant current unit respectively, and is used to control the high-voltage power tube and the low-voltage power tube according to the resonance valley bottom detection signal and the constant voltage and constant current signal, and the input end of the high-voltage power tube and the low-voltage power tube is connected with the output end of the logic control unit through the drive circuit.

[0016] Preferably, the chip further comprises a start-up circuit, which is connected between 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 the power of the chip, and the Iset pin is connected with the input end of the current sampling unit.

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

[0019] The utility model also provides a kind of flyback AC-DC circuit, including according to the power control chip, direct current source, transformer, RCD absorption circuit, secondary side synchronous rectification circuit;

[0020] The HV pin of the power control chip is connected to the positive pole of the direct current source, the opposite end of the primary winding of the transformer is connected to the negative pole of the direct current source, the same 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 detection of input and output voltage, and the secondary side synchronous rectification circuit is connected to the secondary winding of the transformer.

[0021] The utility model also provides a kind of flyback AC-DC circuit, including according to the power control chip, direct current source, transformer, RCD absorption circuit, secondary side synchronous rectification circuit;

[0022] The same end of the primary winding of the transformer is connected to the positive pole of the direct current source, the GND pin of the power control chip is connected to the negative pole of the direct current source, the opposite 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 the two ends of the primary winding.

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

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

[0025] Beneficial effects: the utility model provides a kind of power control chip, flyback circuit and power supply, and the power control chip is integrated with high-voltage power tube, low-voltage power tube, voltage detection unit, current sampling unit, constant voltage constant current unit and logic control unit, without external starting circuit and VCC power supply circuit;Without external sampling circuit, provide Iset foot, set power through an external resistance;When adopting double-winding transformer, auxiliary winding is not needed, on the basis of simplifying system circuit and optimizing system cost, not only realizes the chip functions such as output voltage detection, input over / under voltage protection, but also realizes zero-crossing detection of inductance current, so as to achieve the effect that power tube is turned on when HV resonant voltage reaches valley, realize high-efficiency power conversion. BRIEF DESCRIPTION OF DRAWINGS

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

[0027] Figure 2 An internal design principle block diagram of a power supply control chip provided in the embodiments of the application;

[0028] Figure 3 An internal principle diagram of a power supply control chip provided in the embodiments of the application;

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

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

[0031] In order to make the skilled in the art better understand the technical solutions of the present application, the present application is described in further detail below in conjunction with the drawings and specific embodiments.

[0032] Unless otherwise defined, technical or scientific terms used in the present application should be understood as having the meaning commonly understood by one of ordinary skill in the art to which this application belongs. The terms "first", "second", and similar terms used in the present application do not imply any order, number or importance, but are only used to distinguish different components. Similarly, the terms "one", "a" or "the" and similar terms do not limit the quantity, but mean that there is at least one. The terms "include" or "contain" and similar terms mean that the elements or objects before the term encompass the elements or objects listed after the term and their equivalents, without excluding other elements or objects. The terms "connect" or "connected" and similar terms do not limit to physical or mechanical connections, but can include electrical connections, whether direct or indirect. The terms "up", "down", "left", "right" and the like are only used for relative positional relationship, and when the absolute position of the described object changes, the relative positional relationship may also change accordingly.

[0033] In the various drawings, the same elements are designated by like reference numerals. For the sake of clarity, not all parts of the drawings are to scale.

[0034] Many specific details of the present application are described below in the context of the application, such as the structure, material, size, processing and technology of the components, in order to make the present application more clearly understood. However, as those skilled in the art can understand, the present application can be implemented without these specific details.

[0035] Embodiment one:

[0036] As Figure 2 And Figure 3 The utility model embodiment provides a power control chip, comprising:

[0037] High voltage power tube, the high voltage power tube is realized by two stage composite triode structure's darlington tube, the collector of high voltage power tube is used for connecting the HV pin of control power on-off, the emitter is connected with VCC pin through power supply circuit;

[0038] Low voltage power tube, the drain of low voltage power tube is connected with the emitter of high voltage power tube, the source of low voltage power tube is used for connecting the GND pin of chip reference ground;

[0039] Voltage detection unit, input end forms the FB pin for connecting feedback voltage, is used for detecting output voltage, detecting the resonance valley bottom of HV;

[0040] Current sampling unit, the input end of current sampling unit is connected with the low voltage power tube, is used for detecting the current flowing through high voltage power tube and low voltage power tube;

[0041] Constant voltage constant current unit, the input end is connected with the output of voltage detection unit, current sampling unit respectively, the output end is connected with logic control unit to output constant voltage constant current signal;

[0042] Logic control unit, the input end is connected with voltage detection unit and constant voltage constant current unit respectively, is used for controlling high voltage power tube and low voltage power tube according to resonance valley bottom detection signal, constant voltage constant current signal, the input end of high voltage power tube and low voltage power tube is connected with the output end of logic control unit through drive circuit.

[0043] Wherein, current sampling unit is equipped with Iset pin for setting chip power, the input end of current sampling unit is connected with Iset pin, and external system can control chip overcurrent protection point by adjusting the resistance connected with Iset pin.

[0044] Specifically refer to Figure 2It can be seen that the power control chip IC internally includes a logic control unit LOGIC, a voltage detection unit (Valley Detec, Vin Detec, Vout Detec), a constant voltage and constant 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-power supply circuit (i.e. a power supply circuit), and a drive circuit, etc. The power control chip IC is externally provided with FB pins, HV pins, GND pins, and VCC pins, 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 of each circuit module is as follows:

[0046] The voltage detection unit, the constant voltage and constant current unit, and the current sampling unit are connected with the logic control unit, for inputting signals to the logic control unit, including: a resonance valley bottom detection signal, an overvoltage signal, and a constant voltage and constant current signal. The high-voltage power tube and the low-voltage power tube are connected with the output end of the logic control unit. The logic control outputs a control signal according to the resonance valley bottom detection signal, the overvoltage signal, and the constant voltage and constant current signal, and the control signal is finally controlled by two drive circuits to control the switching of the high-voltage power tube and the low-voltage power tube. One drive circuit is connected with the high-voltage power tube, and the high-voltage power tube is also connected with the other end of the start-up circuit together with the HV pin. The other drive circuit is connected with the base of the low-voltage power tube, and the emitter of the low-voltage power tube is connected with the GND pin.

[0047] The voltage detection unit is used for valley bottom detection and over / under voltage protection of input and output, and the valley bottom of the power tube is opened through a resonance valley bottom detection circuit to reduce switching loss and improve efficiency. The current sampling unit is used for detecting whether the output is overcurrent. The logic control unit is used for outputting a control signal according to the resonance valley bottom detection signal, the overvoltage signal, the overcurrent signal, and the power regulation signal, and the control signal is finally controlled by a drive circuit to control the switching of the high-voltage power tube and the low-voltage power tube LV MOS.

[0048] Among them, the chip also includes a start-up circuit connected between the HV pin and the input end of the high-voltage power tube. Referring to Figure 3 is the schematic diagram of the power control chip. Referring to Figure 2 and Figure 3 , it can be seen that the high-voltage power tube in Figure 2 is realized by a two-stage composite triode (i.e. Darlington triode), Figure 2 the start-up circuit in Figure 2The power supply circuit in the power supply control chip is realized by a power supply diode.

[0049] 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 and constant current unit, and a logic control unit, and does not need an external starting circuit and a VCC power supply circuit; does not need an external sampling circuit, provides an Iset pin, and sets power through an external resistor; when a double-winding transformer is used, an auxiliary winding is not needed, and on the basis of simplifying a system circuit and optimizing a system cost, the chip functions of output voltage detection, input overvoltage and undervoltage protection, and the like are realized, and zero-crossing detection of inductance current is also realized, so that the power tube is turned on when HV resonance voltage reaches a valley, and high-efficiency power conversion is realized.

[0050] Embodiment Two

[0051] The embodiment is an extended application of the power supply control chip based on Embodiment One. Specifically, a flyback AC-DC circuit for the power supply control chip is provided, which includes the power supply control chip described in Embodiment One, and further includes a DC source, a transformer, an RCD absorption circuit, and a secondary side synchronous rectification circuit.

[0052] The HV pin of the power supply control chip is connected to the positive pole of the DC source, the opposite-phase end of the primary winding of the transformer is connected to the negative pole of the DC source, the same-phase end of the primary winding of the transformer is connected to the GND pin of the power supply control chip, the RCD absorption circuit is connected in parallel to the two ends of the primary winding, the FB pin of the power supply control chip collects a transformer primary winding voltage signal, which is used for valley detection and detection of input and output voltages, and the secondary side synchronous rectification circuit is connected to the secondary winding of the transformer. The flyback AC-DC circuit does not need an auxiliary winding (a double-winding transformer is used), on the basis of simplifying a system circuit and optimizing a system cost, comprehensive chip protection functions of output overvoltage and undervoltage protection, input overvoltage and undervoltage protection, and the like are realized, and zero-crossing detection of inductance current is also realized, so that the power tube is turned on at the valley voltage, and high-efficiency power conversion is realized.

[0053] The high-voltage power tube and the low-voltage power tube are arranged at the high side of the primary winding, and the VCC outside is a power supply capacitor C2 for the power supply control chip; the Iset external resistor is used for overcurrent protection point setting.

[0054] The flyback power supply using the power supply control chip IC of Embodiment One can work in two modes of high side and low side, and typical application principle diagrams are shown in Figure 4 and Figure 5 respectively. In Figure 4For example, the high side application, the HV pin and the GND pin of the power control chip IC are connected with a switch power tube in series with a current detection low voltage power tube, which is placed in the high side of the primary winding, and the VCC outside is provided with an IC power supply capacitor C2, and the IC is internally integrated with a power supply circuit; the FB pin samples the voltage signal of the transformer primary winding for valley detection and over / under voltage protection of input and output; the Iset is externally connected with a resistor for setting the overcurrent protection point of the system.

[0055] Embodiment three:

[0056] This is based on the power control chip of embodiment one, which is extended for application. Specifically, a flyback AC-DC circuit for the power control chip is provided, which includes a power control chip, a DC source, a transformer, an RCD absorption circuit, and a secondary side synchronous rectification circuit.

[0057] The same name end of the primary winding of the transformer is connected to the positive pole of the DC source, the GND pin of the power control chip is connected to the negative pole of the DC source, the different 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 the two ends of the primary winding.

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

[0059] This embodiment scheme adopts the flyback power supply of the power control chip IC of embodiment one, Figure 5 which is different from the high side application, Figure 5 as shown in the low side application, an auxiliary winding is needed, and after resistance voltage division, the ZCD pin is used for input and output voltage detection and inductor current zero-crossing detection. Specifically, the auxiliary winding, the resistor R3 and the resistor R4 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 with the resistor R13 and the resistor R14, and the HV pin of the power control chip is connected with the primary winding.

[0060] Embodiment four:

[0061] This embodiment provides a power supply, which is controlled by the flyback AC-DC circuit in the above-mentioned embodiments two or three. The application circuit is greatly simplified, which can guarantee comprehensive protection, high efficiency conversion, and reduce the implementation cost of the power supply.

[0062] It can be understood that the above embodiments are only exemplary embodiments for illustrating the principles of the present application, and the present application is not limited thereto. Various modifications and improvements can be made by those of ordinary skill in the art without departing from the spirit and essence of the present application, and these modifications and improvements are also considered to be within the protection scope of the present application.

Claims

1. A power control chip, characterized by, The chip comprises: a high-voltage power tube realized by a Darlington tube of a two-stage compound triode structure, a collector of the high-voltage power tube being used for connecting to an HV pin for controlling on-off of a power supply, and an emitter being connected to a VCC pin through a power supply circuit; a low-voltage power tube, a drain of the low-voltage power tube being connected to an emitter of the high-voltage power tube, and a source of the low-voltage power tube being used for connecting to a GND pin for a chip reference ground; a voltage detection unit, an input end of the voltage detection unit being formed as an FB pin for connecting to a feedback voltage, and being used for detecting an output voltage and detecting a resonance valley bottom of the HV; a current sampling unit, an input end of the current sampling unit being connected to the low-voltage power tube, and being used for detecting a current flowing through the high-voltage power tube and the low-voltage power tube; a constant voltage and constant current unit, input ends of the constant voltage and constant current unit being connected to output ends of the voltage detection unit and the current sampling unit respectively, and an output end of the constant voltage and constant current unit being connected to a logic control unit to output a constant voltage and constant current signal; the logic control unit, input ends of the logic control unit being connected to the voltage detection unit and the constant voltage and constant current unit respectively, and being used for controlling the high-voltage power tube and the low-voltage power tube according to a resonance valley bottom detection signal and a constant voltage and constant current signal, and input ends of the high-voltage power tube and the low-voltage power tube being connected to an output end of the logic control unit through a driving circuit.

2. The power control chip of claim 1, wherein, The chip further comprises a starting circuit, the starting circuit being connected between the HV pin and the input end of the high-voltage power tube.

3. The power control chip of claim 1, wherein, The current sampling unit is provided with an Iset pin for setting a chip power, the Iset pin being connected to an input end of the current sampling unit.

4. The power control chip of claim 1, wherein, 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 by, The power supply control chip, a direct current source, a transformer, an RCD absorption circuit, and a secondary side synchronous rectification circuit according to any one of claims 1-4 are comprised. The HV pin of the power supply control chip is connected to a positive pole of the direct current source, a same name end of a primary side winding of the transformer is connected to a negative pole of the direct current source, a GND pin of the power supply control chip is connected to a same name end of the primary side winding of the transformer, the RCD absorption circuit is connected in parallel to both ends of the primary side winding, an FB pin of the power supply control chip collects a voltage signal of the primary side winding of the transformer, and is used for valley bottom detection and input and output voltage detection, and the secondary side synchronous rectification circuit is connected to a secondary side winding of the transformer.

6. A flyback AC-DC circuit characterized by, The power supply control chip, a direct current source, a transformer, an RCD absorption circuit, and a secondary side synchronous rectification circuit according to any one of claims 1-4 are comprised. A same name end of a primary side winding of the transformer is connected to a positive pole of the direct current source, a GND pin of the power supply control chip is connected to a negative pole of the direct current source, an opposite name end of the primary side winding of the transformer is connected to an HV pin of the power supply control chip, and the RCD absorption circuit is connected in parallel to both ends of the primary side winding. An FB pin of the power supply control chip collects a voltage signal of an auxiliary winding of the transformer, and is used for valley bottom detection and input and output voltage detection, and the secondary side synchronous rectification circuit is connected to a secondary side winding of the transformer.

7. A power supply, characterized by, The power supply is controlled by the flyback AC-DC circuit according to any one of claims 5 or 6.

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