Power supply control chip, flyback 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 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 field of flyback power supply technology, and in particular to a power control chip, a flyback 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 1 The use of R5 and D2 in Chinese.

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

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

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

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

[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 output the over-voltage signal;

[0013] a current sampling unit, the input end of the current sampling unit is connected to the low-voltage power tube, 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 regulation signal;

[0015] a logic control unit, 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 tube and the low-voltage power tube according to the valley detection signal, the output over-voltage signal, the over-current signal and the power regulation signal, and the input ends of the high-voltage power tube and the low-voltage power tube are connected to the output end of the logic control unit through a drive circuit.

[0016] Preferably, the chip further comprises a start-up circuit 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 to the input end of the current sampling unit. ​

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

[0019] The utility model also provides a flyback circuit, including as the power control chip, direct current source, transformer, RCD absorption circuit and vice edge voltage sampling and error amplifier circuit as described above,

[0020] The HV pin of the power control chip is connected to the positive pole of the direct current source, the opposite name end of the primary winding of the transformer is connected to the negative pole of the direct current 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 ZCD pin of the power control chip collects the voltage signal of the primary winding of the transformer, is used for valley bottom detection and the over / under voltage protection of input and output, the input end of the vice edge voltage sampling and error amplifier circuit is connected to the secondary winding of the transformer, and the output end of the vice edge voltage sampling and error amplifier circuit is connected to the COMP pin of the power control chip.

[0021] The utility model also provides a flyback circuit, including as the power control chip, direct current source, transformer, RCD absorption circuit and vice edge voltage sampling and error amplifier circuit as described above,

[0022] The same name 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 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.

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

[0024] The utility model also provides a power supply, and the power supply is controlled through the flyback circuit as described above.

[0025] Beneficial effects: the utility model provides a power control chip, flyback circuit and power, the power control chip integrates high voltage power tube, low voltage power tube, voltage detection unit, current sampling unit, power control unit, logic control unit, need not additional starting circuit and VCC power supply circuit, need not external sampling circuit, provides Iset foot, sets up power through an external resistance, adopts double winding transformer without auxiliary winding, on the basis of simplifying system circuit and optimizing system cost, realizes comprehensive chip protection function such as output overvoltage protection, input overvoltage protection, also realizes inductance current zero-crossing detection, thereby reaches the effect that power tube opens at the bottom voltage, realizes high -efficient power conversion. Wherein, voltage detection unit is used for valley bottom detection and input output overvoltage protection, realizes the valley bottom opening of power tube through valley bottom detection circuit, reduces switching loss and improves efficiency. Current sampling unit is used for detecting whether output is overcurrent. Power control unit is used for accessing COMP pin of feedback signal, and according to feedback signal output power regulation signal. Logic control unit is used for according to valley bottom detection signal, overvoltage signal, overcurrent signal and the power regulation signal output control signal, and control signal passes through drive circuit and finally controls the switch of high voltage power tube and low voltage power tube LV MOS. BRIEF DESCRIPTION OF DRAWINGS

[0026] Figure 1 It is the circuit diagram of flyback power supply of commonly used integrated power switch tube provided in the background art of the application;

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

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

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

[0030] Figure 5 It is the schematic diagram of flyback power supply in low side application provided in the embodiment of the application. DETAILED DESCRIPTION

[0031] In order to make those skilled in the art better understand the technical scheme of the application, the application will be further described in detail below with the drawings and specific embodiments.

[0032] Unless otherwise defined, technical terms or scientific terms used in the present application shall have the same meaning as commonly understood by one of ordinary skill in the art to which this application belongs. Unless otherwise defined, the terms "first", "second", and the like, used in the present application do not necessarily have any order or sequence or importance, but are used to distinguish different components. Also, the terms "a", "an", or "the" and the like, do not necessarily refer to a quantity or to one or more of something, but refer to the existence of at least one of something. The terms "comprises", "comprising", "includes", "including" and the like, mean including but not limited to, and the terms "connected", "coupled", "linked" and the like, do not necessarily mean physically or mechanically connected or linked, but can include electrical connection or linkage, whether direct or indirect. The terms "upper", "lower", "left", "right", and the like, are used only for relative positional relationship, and when the absolute position of the described object is changed, the relative positional relationship can also be changed accordingly.

[0033] In the various drawings, the same elements are denoted 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 order to provide a thorough understanding of the present application. However, as will be readily understood by one skilled in the art, the present application can be implemented without these specific details.

[0035] Embodiment one:

[0036] As shown in Figure 2 and Figure 3 The utility model embodiment provides a kind of power control chip, comprising:

[0037] High-voltage power tube, the high-voltage end (drain or collector) of the high-voltage power tube is used to access the HV pin of control power on-off, low-voltage end (source or emitter) is used to access the VCC pin of chip power supply, low-voltage end (source or emitter) and the VCC pin are provided with power supply circuit between them;

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

[0039] Voltage detection unit, input end forms ZCD pin for accessing feedback voltage, for collecting valley detection signal, output overvoltage signal;

[0040] Current sampling unit, the input end of the current sampling unit is connected with the low-voltage power tube, for collecting overcurrent signal;

[0041] a power control unit, an input end of which forms a COMP pin for accessing a feedback signal, for collecting a power regulation signal;

[0042] a logic control unit, three input ends of which are connected with the voltage detection unit, the current sampling unit and the power control unit respectively, for controlling the high-voltage power tube and the low-voltage power tube according to the valley detection signal, the over-voltage signal, the over-current signal and the power regulation signal, and the input ends of the high-voltage power tube and the low-voltage power tube are connected with 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 power of the chip, the Iset pin is connected with the input end of the current sampling unit, and the external system can control the over-current protection point of the chip by adjusting the resistance connected with the Iset pin.

[0044] wherein the voltage detection unit further has the function of input voltage detection, for input over-voltage protection.

[0045] Specifically referring to Figure 2 It can be seen that the power supply control chip IC internally includes a logic control unit, a voltage detection unit, a power control unit, a start-up circuit, a power supply circuit, a current sampling unit, a drive circuit, a high-voltage power tube and a low-voltage power tube (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. a power supply circuit) and a drive circuit, etc. The power supply 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 with the voltage detection unit, the power control unit, the low-voltage power tube, the high-voltage power tube and the power supply circuit.

[0046] The connection relationship of each circuit module is as follows:

[0047] The voltage detection unit, the power control unit and the drive current sampling unit are connected with the logic control unit, for inputting signals to the logic control unit, the input signals including a valley detection signal, an over-voltage signal, an over-current signal and a power regulation 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 control signals according to the valley detection signal, the over-voltage signal, the over-current signal and the power regulation signal, and the control signals are finally controlled through two drive circuits to control the switches 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 start-up circuit, and the high-voltage power tube is connected with the HV pin together with the other end of the start-up circuit. 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.

[0048] The voltage detection unit is used for valley detection and over / under voltage protection of the input and output. The valley detection circuit enables the power transistor to turn on during valley periods, reducing switching losses and improving efficiency. The current sampling unit is used to detect output overcurrent. The power control unit connects to the COMP pin of the feedback signal and outputs a power adjustment signal based on the feedback signal. The logic control unit outputs a control signal based on the valley detection signal, overvoltage signal, overcurrent signal, and the power adjustment signal. The control signal ultimately controls the switching of the high-voltage power transistor and the low-voltage power transistor LV MOS through the drive circuit.

[0049] The chip also includes a startup circuit, which is connected to the HV pin and the input terminal of the high-voltage power transistor. (Reference) Figure 3 This is the schematic diagram of the power control chip. (Refer to...) Figure 2 and Figure 3 Let's take a look. Figure 2 The high-voltage power transistor in the circuit is implemented using a two-stage composite transistor (i.e., a Darlington transistor). Figure 2 The startup circuit is implemented by a startup resistor. Figure 2 The power supply circuit is implemented by a power supply diode.

[0050] Example 2:

[0051] This embodiment extends the application of the power control chip based on Embodiment 1. Specifically, it provides a flyback circuit for the power control chip described above, including the power control chip in Embodiment 1, and further including a DC source, a transformer, an RCD snubber circuit, and a secondary voltage sampling and error amplification circuit. The HV pin of the power control chip is connected to the positive terminal of the DC source. The opposite-named terminal of the primary winding of the transformer is connected to the negative terminal of the DC source, and the same-named terminal of the primary winding of the transformer is connected to the GND pin of the power control chip. The RCD snubber circuit is connected in parallel across 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 / under voltage protection of the input and output. The input terminal of the secondary voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output terminal of the secondary voltage sampling and error amplification circuit is connected to the COMP pin of the power control chip. The flyback circuit eliminates the need for auxiliary windings (using a dual-winding transformer), simplifying the system circuit and optimizing system costs. It achieves comprehensive chip protection functions such as output over / under voltage protection and input over / under voltage protection, as well as zero-crossing detection of inductor current, thereby enabling the power transistor to turn on at the valley voltage and achieving 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 the loop optocoupler to control the peak operating current inside the power control chip. VCC is external to the power control chip, which is supplied by capacitor C2. The ZCD pin samples the voltage signal of the transformer primary winding for valley detection and input / output over / under voltage protection. The Iset external resistor is used for overcurrent protection point setting.

[0053] The flyback power supply using the power control chip IC in this embodiment can operate in both high-side and low-side modes. Typical application schematics are shown below. Figure 4 and Figure 5 As shown. Figure 4 Taking a high-side application as an example, the HV pin and GND pin of the power control chip IC are internally connected to a series current-sensing low-voltage power transistor, which 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. VCC is external to the IC power supply capacitor C2, and the IC integrates a power supply circuit. The ZCD pin samples the voltage signal of the transformer primary winding for valley detection and over / under voltage protection of input and output. The Iset external resistor is used to set the overcurrent protection point of the system.

[0054] Example 3:

[0055] This invention extends the application of the power control chip based on Embodiment 1. Specifically, it provides a flyback circuit for the power control chip described above, including the power control chip, a DC source, a transformer, an RCD snubber circuit, and a secondary voltage sampling and error amplification circuit.

[0056] The same-name terminal of the primary winding of the transformer is connected to the positive terminal of the DC source, the GND pin of the power control chip is connected to the negative terminal of the DC source, the opposite-name terminal of the primary winding of the transformer is connected to the HV pin of the power control chip, and the RCD snubber circuit is connected in parallel across the two ends of the primary winding.

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

[0058] This embodiment uses the flyback power supply of the power control chip IC from Embodiment 1, to... Figure 5 For example, unlike high-side applications, Figure 5When the low-side application is shown, the auxiliary winding needs to be used, and the resistance voltage division is used for the input and output voltage detection and the inductor current zero-crossing detection through the ZCD pin. Specifically, the auxiliary winding, the resistance R13 and the resistance R14 are sequentially connected in series to form a loop, one end of the resistance R14 is grounded, the ZCD pin of the power control chip is connected with the resistance R13 and the resistance R14, and the HV pin of the power control chip is connected with the primary winding.

[0059] Embodiment four:

[0060] The embodiment provides a power supply which is controlled by the flyback circuit in the above-mentioned embodiment two or three. The application circuit is greatly simplified, the comprehensive protection and the high-efficiency conversion can be ensured, and the implementation cost of the power supply is reduced.

[0061] It can be understood that the above implementation manners are only exemplary implementation manners adopted for illustrating the principles of the application, and the application is not limited thereto. Various modifications and improvements can be made by those skilled in the art without departing from the spirit and essence of the application, and the modifications and improvements are also regarded as the protection scope of the application.

Claims

1. A power control chip, characterized in that, include: A high-voltage power transistor, wherein the drain or collector of the high-voltage power transistor is used to connect to the HV pin for controlling the on / off state of the power supply, and the source or emitter is used to connect to the VCC pin for power supply of the chip, and a power supply circuit is provided between the source or emitter and the VCC pin. A low-voltage power transistor, wherein the drain of the low-voltage power transistor is connected to the 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; The voltage detection unit has a ZCD pin at its input terminal for receiving feedback voltage, which is used to acquire valley detection signals and output over / under voltage signals. A current sampling unit, the input terminal of which is connected to the low-voltage power transistor, is used to collect overcurrent signals; The power control unit has a COMP pin at its input terminal for receiving feedback signals and for acquiring power regulation signals; The logic control unit has three input terminals connected to the voltage detection unit, the current sampling unit, and the power control unit, respectively. It is used to control the high-voltage power transistor and the low-voltage power transistor according to the valley detection signal, the output over / under voltage signal, the overcurrent signal, and the power adjustment signal. The input terminals of the high-voltage power transistor and the low-voltage power transistor are connected to the output terminal of the logic control unit through a drive 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 terminal of the high-voltage power transistor.

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

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

5. A flyback circuit, characterized in that, Includes the power control chip, DC source, transformer, RCD snubber circuit, and secondary voltage sampling and error amplification circuit as described in any one of claims 1-4; The HV pin of the power control chip is connected to the positive terminal of the DC source. The opposite terminal of the primary winding of the transformer is connected to the negative terminal of the DC source. The same terminal of the primary winding of the transformer is connected to the GND pin of the power control chip. The RCD snubber circuit is connected in parallel across the two 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 / under voltage protection of input and output. The input terminal of the secondary voltage sampling and error amplification circuit is connected to the secondary winding of the transformer. The output terminal 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, Includes the power control chip, DC source, transformer, RCD snubber circuit, and secondary voltage sampling and error amplification circuit as described in any one of claims 1-4; The same-name terminal of the primary winding of the transformer is connected to the positive terminal of the DC source, the GND pin of the power control chip is connected to the negative terminal of the DC source, the opposite-name terminal of the primary winding of the transformer is connected to the HV pin of the power control chip, and the RCD snubber circuit is connected in parallel across the two ends of the primary winding. The ZCD pin of the power control chip acquires the voltage signal of the auxiliary winding of the transformer for valley detection and over / under voltage protection of input and output. The input terminal of the secondary voltage sampling and error amplification circuit is connected to the secondary winding of the transformer, and the output terminal 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 described in any one of claims 5 or 6.

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