Power supply control chip, flyback 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 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 power control unit and a logic control unit, and does not need an additional 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; an auxiliary winding is not needed when the transformer with the double windings is adopted, comprehensive chip protection functions such as output overvoltage and undervoltage protection and input overvoltage and undervoltage protection are achieved on the basis of simplifying a system circuit and optimizing system cost, zero-cross detection of inductive current is achieved, the effect that a power tube is switched on at valley voltage 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 technical field of flyback power supplies, and particularly to a power control chip, a flyback circuit, and a power supply. Background Art

[0002] In the topology of medium and small power ACDC power supplies, flyback occupies an 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 to lower the solution cost, and simplify the system design at the same time.

[0003] The peripheral circuit of a common flyback power IC with an internal integrated power switch device is as Figure 1 shown. IC1 integrates a flyback control circuit and a primary high-voltage power transistor (the high-voltage power transistor includes a high-voltage Darlington transistor and a high-voltage MOSFET). Among them, HV is the collector or drain of the high-voltage power transistor, 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 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 after voltage division from the auxiliary winding. The first function is to detect the zero crossing of the inductor current, realize the valley turn-on of the power transistor, reduce the switching loss and improve the efficiency. The second function is to detect the output voltage and the input voltage signal, and realize the input over-voltage / under-voltage protection and the output over-voltage / under-voltage protection; COMP is the power control pin of the control IC, externally connected to the output end of the optocoupler and a capacitor. The input end of the optocoupler is connected to the secondary side voltage sampling, and through the error amplification circuit, a closed-loop control is formed; GND is the reference ground of the IC.

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

[0005] (1) Integrate the start-up circuit (high-voltage transistor or high-voltage resistor), without the Figure 1 shown R3 and R4, reducing the number of peripheral components, but increasing the complexity and cost of the IC (package cost and material cost).

[0006] (2) Integrate the current sampling circuit. The emitter or source of the internal high-voltage power transistor 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 the Figure 1 use of Rcs in. Increasing the design complexity and cost of the power transistor.

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

[0008] In summary, in the simplest state of the existing technical solution, based on the circuit shown in Figure 1 , the use of R3, R4, R5, D2, and Rcs1, Rcs2 is reduced. However, the existing solution still needs to sample the signal after the auxiliary winding is divided by voltage to detect the zero crossing of the output inductor current. Otherwise, it is impossible to achieve the valley voltage turn-on of the power transistor, which affects the power conversion efficiency. Therefore, the transformer needs to have three windings (primary winding, secondary winding, and auxiliary winding). SUMMARY OF THE INVENTION

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

[0010] A high-voltage power transistor, the high-voltage end (drain or collector) of the high-voltage power transistor is used to access the HV pin for controlling the power on and off, and the low-voltage end (source or emitter) is used to access the VCC pin for chip power supply. A power supply circuit is provided between the low-voltage end (source or emitter) and the VCC pin;

[0011] A low-voltage power transistor, the drain of the low-voltage power transistor is connected to the low-voltage end (source or emitter) of the high-voltage power transistor, and the source of the low-voltage power transistor is used to connect to the GND pin of the chip reference ground;

[0012] A voltage detection unit, the input end forms a ZCD pin for accessing the feedback voltage, and is used to collect the valley detection signal and the output over-voltage and under-voltage signals;

[0013] A current sampling unit, the input end of the current sampling unit is connected to the low-voltage power transistor, and is used to collect the over-current signal;

[0014] A power control unit, the input end forms a COMP pin for accessing the feedback signal, and is used to collect the power adjustment signal;

[0015] A logic control unit, the three input ends are respectively connected to the voltage detection unit, the current sampling unit, and the power control unit, and are used to control the high-voltage power transistor and the low-voltage power transistor according to the valley detection signal, the output over-voltage and under-voltage signals, the over-current signal, and the power adjustment signal. The input ends of the high-voltage power transistor and the low-voltage power transistor are both connected to the output end of the logic control unit through a drive circuit.

[0016] Preferably, the chip further includes a startup circuit, and the startup circuit is connected between the HV pin and the input end of the high-voltage power transistor.

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

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

[0019] The present invention also provides a flyback circuit, including the power control chip, DC source, transformer, RCD absorption circuit, and secondary side voltage sampling and error amplification circuit as described above;

[0020] The HV pin of the power control chip is connected to the positive pole of the DC source, the non-corresponding end of the primary winding of the transformer is connected to the negative pole of the DC source, the corresponding 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 across both ends of the primary winding, the ZCD pin of the power control chip collects the voltage signal of the primary winding of the transformer for valley detection and over-voltage and under-voltage protection of the input and output, the input end of the secondary side voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output end of the secondary side voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip.

[0021] The present invention also provides a flyback circuit, including the power control chip, DC source, transformer, RCD absorption circuit, and secondary side voltage sampling and error amplification circuit as described above;

[0022] The corresponding 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 non-corresponding 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 across both ends of the primary winding;

[0023] The ZCD pin of the power control chip collects the voltage signal of the auxiliary winding of the transformer for valley detection and over-voltage and under-voltage protection of the input and output, the input end of the secondary side voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output end of the secondary side voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip.

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

[0025] Beneficial effects: The present invention provides a power control chip, a flyback circuit, and a power supply. This power control chip integrates a high-voltage power transistor, a low-voltage power transistor, a voltage detection unit, a current sampling unit, a power control unit, and a logic control unit, eliminating the need for an additional startup circuit and a VCC power supply circuit; eliminating the need for an external sampling circuit, providing an Iset pin, and setting the power through an external resistor; when using a dual-winding transformer, no auxiliary winding is required. 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 transistor at the valley voltage and realizing high-efficiency power conversion. Among them, the voltage detection unit is used for valley detection and over-voltage and under-voltage protection of the input and output, and realizes the valley turn-on of the power transistor through the valley detection circuit, reducing the switching loss and improving the efficiency. The current sampling unit is used to detect whether the output is over-current. The power control unit is used to connect to the COMP pin of the feedback signal and output a power adjustment signal according to the feedback signal. The logic control unit is used to output a control signal according to the valley detection signal, over-voltage signal, over-current signal, and the power adjustment signal, and the control signal finally controls the switching of the high-voltage power transistor and the low-voltage power transistor LV MOS through the drive circuit. Description of the Drawings

[0026] Figure 1 is the circuit diagram of the flyback power supply with a common integrated power switch tube provided in the background art of the present application;

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

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

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

[0030] Figure 5 is the schematic diagram of the flyback power supply in the low-side application provided in the embodiment of the present application. Detailed Embodiments

[0031] To enable those skilled in the art to better understand the technical solutions of the present application, the present application will be further described in detail below with reference to the drawings and specific embodiments.

[0032] Unless otherwise defined, technical terms or scientific terms used in this application shall have the ordinary meanings as understood by those of ordinary skill in the art to which this application pertains. The "first", "second" and similar terms used in this application are not for any order, quantity or importance, but are only used to distinguish different components. Similarly, terms such as "a", "an" or "the" are not limited to quantity, but mean there is at least one. Terms such as "comprising" or "including" mean that the elements or objects appearing before this term cover the elements or objects listed after this term and their equivalents, without excluding other elements or objects. Terms such as "connected" or "coupled" are not limited to physical or mechanical connections, but may include electrical connections, whether direct or indirect. Terms such as "upper", "lower", "left" and "right" are only for relative positional relationships, and when the absolute position of the object being described changes, the relative positional relationship may also change accordingly.

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

[0034] Many specific details of this application are described below, such as the structure, materials, dimensions, processing techniques and technologies of components, in order to understand this application more clearly. However, as those skilled in the art can understand, this application can be implemented without these specific details.

[0035] Embodiment 1:

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

[0037] A high-voltage power transistor, the high-voltage terminal (drain or collector) of the high-voltage power transistor is used to connect to the HV pin for controlling the on / off of the power supply, and the low-voltage terminal (source or emitter) is used to connect to the VCC pin for chip power supply. A power supply circuit is provided between the low-voltage terminal (source or emitter) and the VCC pin;

[0038] A low-voltage power transistor, the drain of the low-voltage power transistor is connected to the low-voltage terminal (source or emitter) of the high-voltage power transistor, and the source of the low-voltage power transistor is used to connect to the GND pin of the chip reference ground;

[0039] A voltage detection unit, the input terminal forms a ZCD pin for accessing the feedback voltage, and is used to collect the valley detection signal and output the over-voltage / under-voltage signal;

[0040] A current sampling unit, the input terminal of the current sampling unit is connected to the low-voltage power transistor, and is used to collect the over-current signal;

[0041] A power control unit, with a COMP pin formed at the input end for accessing a feedback signal, for collecting a power regulation signal;

[0042] A logic control unit, with three input ends respectively connected to the voltage detection unit, the current sampling unit and the power control unit, for controlling the high-voltage power transistor and the low-voltage power transistor according to the valley detection signal, the output over- and under-voltage signal, the over-current signal and the power regulation signal, and the input ends of the high-voltage power transistor and the low-voltage power transistor are both connected to the output end of the logic control unit through a drive circuit.

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

[0044] Wherein, the voltage detection unit also has the function of input voltage detection, for input over- and under-voltage protection.

[0045] Specifically referring to Figure 2 It can be known that the power control chip IC internally includes a logic control unit, a voltage detection unit, a power control unit, a startup circuit, a power supply circuit, a current sampling unit, a drive circuit, a high-voltage power transistor, and a low-voltage power transistor (LVMOS). 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., the power supply circuit) and a drive circuit, etc. The power control chip IC is externally provided with a ZCD pin, a COMP pin, a GND pin, an HV pin and a VCC pin, which are respectively connected to the voltage detection unit, the power control unit, the low-voltage power transistor, the high-voltage power transistor and the power supply circuit.

[0046] The connection relationships of each circuit module are as follows:

[0047] The voltage detection unit, the power control unit, and the drive current sampling unit are all connected to the logic control unit, for inputting signals to the logic control unit, and the input signals include: valley detection signal, over-voltage signal, over-current signal and power regulation signal. The high-voltage power transistor and the low-voltage power transistor are both connected to the output end of the logic control unit. The logic control outputs a control signal according to the valley detection signal, the over-voltage signal, the over-current signal and the power regulation signal, and the control signal finally controls the switching of the high-voltage power transistor and the low-voltage power transistor respectively through two drive circuits. One drive circuit and the startup circuit are both connected to the high-voltage power transistor, and the high-voltage power transistor is also connected to the other end of the startup circuit to the HV pin together. The other drive circuit is connected to the base of the low-voltage power transistor, and the emitter of the low-voltage power transistor is connected to the GND pin.

[0048] The voltage detection unit is used for valley detection and over- and under-voltage protection of the input and output. The valley detection circuit is used to achieve valley turn-on of the power tube, reduce the switching loss and improve the efficiency. The current sampling unit is used to detect whether the output is overcurrent. The power control unit is used to connect to the COMP pin of the feedback signal and output a power adjustment signal according to the feedback signal. The logic control unit is used to output a control signal according to the valley detection signal, overvoltage signal, overcurrent signal and the power adjustment signal, and the control signal finally controls the switching of the high-voltage power tube and the low-voltage power tube (LV MOS) through the drive circuit.

[0049] Among them, the chip further includes a startup circuit, and the startup circuit is connected between the HV pin and the input end of the high-voltage power tube. Refer to Figure 3 for the schematic diagram of the power control chip. Comparing Figure 2 and Figure 3 it can be seen that Figure 2 the high-voltage power tube in Figure 2 is implemented by two-stage composite triodes (i.e., Darlington triodes), Figure 2 the startup circuit in

[0050] is implemented by a startup resistor,

[0051] the power supply circuit in

[0050] is implemented by a power supply diode.

[0050] Embodiment 2:

[0051] This embodiment is an extended application of the power control chip on the basis of Embodiment 1. Specifically, a flyback circuit for the above-mentioned power control chip is provided, which includes the power control chip in Embodiment 1, and also includes a DC source, a transformer, an RCD absorption circuit, and a secondary-side voltage sampling and error amplification circuit. The HV pin of the power control chip is connected to the positive pole of the DC source, the non-homonymous end of the primary winding of the transformer is connected to the negative pole of the DC source, the homonymous 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 at both ends of the primary winding, the ZCD pin of the power control chip samples the voltage signal of the primary winding of the transformer for valley detection and over- and under-voltage protection of the input and output, the input end of the secondary-side voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output end of the secondary-side voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip. The flyback circuit does not require an auxiliary winding (using a transformer with two windings). 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- and under-voltage protection and input over- and under-voltage protection, but also realizes zero-crossing detection of the inductor current, so as to achieve the effect of turning on the power tube at the valley voltage and realize high-efficiency power conversion.

[0052] Among them, the high-voltage power transistor and the low-voltage power transistor are placed on the high side of the primary winding. The COMP pin is connected to a loop optocoupler to control the peak operating current inside the power control chip. The external VCC is the power supply capacitor C2 for the power control chip; the ZCD pin samples the voltage signal of the primary winding of the transformer for valley detection and over- and under-voltage protection of the input and output; the externally connected Iset resistor is used for setting the over-current protection point.

[0053] The flyback power supply using the power control chip IC of the first embodiment can operate in two modes: high side and low side. The typical application schematic diagrams are respectively as Figure 4 and Figure 5 shown. Taking Figure 4 the high-side application as an example, the switch power transistor connected in series with the low-voltage power transistor for current detection inside the HV pin and GND pin of the power control chip IC is placed on the high side of the primary winding. The COMP pin is connected to a loop optocoupler to control the peak operating current inside the IC. The external VCC is the power supply capacitor C2 for the IC, and the power supply circuit is integrated inside the IC; the ZCD pin samples the voltage signal of the primary winding of the transformer for valley detection and over- and under-voltage protection of the input and output; the externally connected Iset resistor is used for setting the over-current protection point of the system.

[0054] Embodiment 3:

[0055] This is an extended application of the power control chip based on Embodiment 1. Specifically, a flyback circuit for the above-mentioned power control chip is provided, including a power control chip, a DC source, a transformer, an RCD absorption circuit, and a secondary-side voltage sampling and error amplification circuit;

[0056] 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 across both ends of the primary winding;

[0057] The ZCD pin of the power control chip collects the voltage signal of the auxiliary winding of the transformer for valley detection and over- and under-voltage protection of the input and output. The input end of the secondary-side voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output end of the secondary-side voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip.

[0058] The solution of this embodiment uses the flyback power supply of the power control chip IC of Embodiment 1. Taking Figure 5 as an example, different from the high-side application, Figure 5When the low-side application is shown, an auxiliary winding is required. 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, resistor R13, and resistor R14 connected in series in sequence to form a loop. One end of the resistor R14 is grounded. The ZCD pin of the power control chip is connected to resistor R13 and resistor R14. The HV pin of the power control chip is connected to the primary winding.

[0059] Embodiment 4:

[0060] This embodiment provides a power supply, and the power supply is controlled by the flyback 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.

[0061] It can be understood that the above embodiments are merely exemplary embodiments adopted to illustrate the principle of the present application. However, the present application is not limited thereto. For those of ordinary skill in the art, various modifications and improvements can be made without departing from the spirit and essence of the present application, and these modifications and improvements are also regarded as the protection scope of the present application.

Claims

1. A power control chip, characterized in that: include: A high-voltage power tube, wherein the drain or collector of the high-voltage power tube is used to connect to the HV pin for controlling the on / off of the power supply, the source or emitter is used to connect to the VCC pin for powering the chip, and a power supply circuit is provided between the source or emitter and the VCC pin; A low-voltage power tube, wherein the drain of the low-voltage power tube is connected to the source or 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; The voltage detection unit, the input end forms a ZCD pin for accessing the feedback voltage, which is used to collect the valley detection signal and output the over-voltage and under-voltage signal; A current sampling unit, wherein the input end of the current sampling unit is connected to the low-voltage power tube and is used to collect an overcurrent signal; A power control unit, the input end of which forms a COMP pin for receiving a feedback signal, and is used to collect a power regulation signal; A logic control unit, wherein three input ends are respectively connected to the voltage detection unit, the current sampling unit and the power control unit, and is used to control the high-voltage power tube and the low-voltage power tube according to the valley detection signal, the output over-voltage and under-voltage signal, the overcurrent signal and the power regulation 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 circuit, characterized in that: It comprises a power control chip according to any one of claims 1 to 4, a DC source, a transformer, an RCD absorption circuit, a secondary voltage sampling and error amplification circuit; The HV pin of the power control chip is connected to the positive electrode of the DC source, the opposite-name end of the primary winding of the transformer is connected to the negative electrode 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, and the ZCD pin of the power control chip collects the primary winding voltage signal of the transformer for valley bottom 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, and the output end of the secondary voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip.

6. A flyback circuit, characterized in that: It comprises a power control chip according to any one of claims 1 to 4, a DC source, a transformer, an RCD absorption circuit, a secondary voltage sampling and error amplification 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 ZCD 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, and the output end of the secondary voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip.

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

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