Flyback switching power supply supporting wide output voltage range and charging method

Abstract

The present application relates to a flyback switching power supply and a charging method supporting a wide output voltage range, belonging to the field of power supply technology. The flyback switching power supply includes a power supply circuit, a first error amplifier, a second error amplifier, a pulse width modulation circuit, an inverter, a delay adjustment circuit, a drive circuit, an AND gate circuit, and a control switch; it can solve the problem that the operating voltage of the switching power supply chip is insufficient or too high when the output voltage of the flyback switching power supply changes; because the power supply chip can be powered by time division multiplexing technology, the energy on the coil can be flexibly used. When the secondary coil is turned on, the energy on the coil is first used to provide power output; when the auxiliary coil is turned on, the remaining energy on the coil is used to provide the operating voltage for the primary switching power supply chip; avoiding the waste of coil energy by the switching power supply chip. The output range of the present application is wide, the working principle is simple, and it is easy to implement.

Description

Technical Field

[0001] The present application relates to a flyback switching power supply supporting a wide output voltage range and a charging method, belonging to the technical field of power supplies. Background Art

[0002] In recent years, due to the increase in the types of electronic products, universal chargers have become an inevitable trend, and chargers that support the USB Power Delivery (USB-PD) protocol can meet this demand. The charger can fast charge mobile phones, notebooks, tablets and other terminals through the Type-C connector (maximum power 100W). At the same time, when the terminal does not support fast charging or does not use the Type-C connector, a charger that supports a wide output voltage range can also charge the terminal at a low power, so a charger that supports a wide output voltage range allows a wide output voltage range. Flyback switching power supplies are widely used due to their high safety, low cost and simple peripheral circuits.

[0003] In a typical flyback switching power supply, the power supply of the switching power supply chip generally comes from the induced voltage of the auxiliary coil. Because the system always tries to keep the output voltage stable, the induced voltage of the auxiliary coil is in phase with the output coil and is subject to the voltage of the secondary coil. At the lowest output voltage (for example, when the USB PD charger works at the initial 5V output voltage), a corresponding and sufficient auxiliary coil voltage is required to avoid insufficient power supply; when the output voltage of the flyback switching power supply is higher (for example, when the USB PD charger works at a 20V output voltage), the induced voltage on the auxiliary coil is bound to become very high. In order to ensure that the chip power supply is within the allowable range, the induced voltage on the auxiliary coil needs to take necessary limiting measures (such as using a series regulator) so that the chip power supply voltage is not higher than the allowable voltage value, which will waste part of the coil energy, thereby reducing the efficiency of the flyback switching power supply and increasing the power consumption of the flyback switching power supply. At the same time, the series voltage regulator circuit also generates a lot of heat.

[0004] The present invention provides a flyback switching power supply supporting a wide output voltage range. The power supply only needs to add a simple control circuit to meet the requirement that after the output voltage range of the power supply is expanded, the power supply chip can also obtain a normal working voltage through the induced voltage on the auxiliary coil. Summary of the invention

[0005] The present application provides a flyback switching power supply and a charging method supporting a wide output voltage range, which can solve the problem that the operating voltage of the switching power supply chip is insufficient or too high when the power output voltage changes; the present application provides the following technical solutions:

[0006] In a first aspect, a flyback switching power supply supporting a wide output voltage range is provided, wherein the flyback switching power supply supporting a wide output voltage range comprises a switching power supply chip, wherein the switching power supply chip comprises:

[0007] A power supply circuit for generating a low voltage for internal operation of the switching power supply chip;

[0008] A first error amplifier having a first non-inverting input terminal connected to a first power supply output terminal of the power supply circuit and a first inverting input terminal leading to a first pin of the switching power supply chip;

[0009] A second error amplifier whose second in-phase input terminal is connected to the second power supply output terminal of the power supply circuit and whose second inverting input terminal leads to the second pin of the switching power supply chip;

[0010] A pulse width modulation circuit having a first signal input terminal connected to the output terminal of the first error amplifier and a second signal input terminal leading to a third pin of the switching power supply chip;

[0011] an inverting circuit connected to the output end of the pulse width modulation circuit;

[0012] A driving circuit connected to the output end of the pulse width modulation circuit; the output end of the driving circuit leads to the fifth pin of the switching power supply chip;

[0013] A delay adjustment circuit whose input end is respectively connected to the output end of the first error amplifier and the output end of the second error amplifier;

[0014] an AND gate circuit whose input ends are respectively connected to the output end of the delay adjustment circuit, the output end of the inverter circuit and the third power supply output end of the power supply circuit; and,

[0015] A control switch connected to the output end of the AND gate circuit, wherein the control switch is used to control the connection or disconnection between the fourth power output end of the power circuit and the fourth pin of the switching power chip.

[0016] Optionally, the switching power supply chip further includes a ground pin.

[0017] Optionally, the power supply circuit also includes a working voltage output terminal and a power supply input terminal.

[0018] Optionally, the delay adjustment circuit outputs a square wave signal after a delay time; wherein the delay time is negatively correlated with the output voltage of the second error amplifier; and positively correlated with the output voltage of the first error amplifier.

[0019] In a second aspect, a charging method is provided, which is used in the flyback switching power supply supporting a wide output voltage range provided in the first aspect, and the method comprises:

[0020] When the secondary coil of the flyback switching power supply is turned on, a delay time is determined based on an output voltage of the first error amplifier and an output voltage of the second error amplifier, wherein the delay time is positively correlated with the output voltage of the first error amplifier and negatively correlated with the output voltage of the second error amplifier;

[0021] During the delay time, the output voltage is provided to the load through the secondary coil;

[0022] When the current duration reaches the delay duration, the control switch is controlled to close, and the auxiliary coil of the flyback switching power supply stores energy in the energy storage capacitor.

[0023] Optionally, at the falling edge of the pulse width modulation signal output by the pulse width modulation circuit, the second error amplifier compares the voltage signal sampled by the second pin with the second reference voltage output by the second voltage output terminal, and generates a second error amplification signal;

[0024] The second error amplified signal and the first error amplified signal output by the first error amplifier are combined to obtain a delay control square wave signal having the delay time length, and the delay control square wave signal is used to generate a control signal for controlling the control switch.

[0025] The beneficial effects of the present application are as follows: by additionally setting a delay adjustment circuit in a flyback switching power supply supporting a wide output voltage range, the delay adjustment circuit determines the delay time of the square wave signal according to the first error amplification signal and the second error amplification signal; so that the secondary coil of the flyback switching power supply provides an output voltage for charging the load within the delay time, and when the delay time reaches the square wave signal position, the residual energy of the transformer charges the energy storage capacitor through the auxiliary coil; the problem of insufficient or excessive working voltage of the flyback switching power supply supporting a wide output voltage range when the power supply output voltage changes can be solved; because the energy on the coil can be flexibly utilized through time division multiplexing technology, when the secondary coil is turned on, the energy on the secondary coil is first used to provide power output; when the auxiliary coil is turned on, the residual energy on the secondary coil is used to provide working voltage for the primary switching power supply chip; the switching power supply chip avoids wasting the energy of the secondary coil; when the auxiliary coil supplies power to the chip, the coil voltage is forced to be pulled down to the level of the chip voltage, and the chip power supply capacitor is charged with the current current, and the output diode is reverse biased and cut off at this time.

[0026] In addition, the flyback switching power supply using the switching power supply chip can ensure a wider range of voltage output and can be used as a charger that supports a wide output voltage range (such as a USB PD charger, a lithium-ion battery pack charger, etc.).

[0027] In addition, the switching power supply chip has a high degree of integration, does not require additional peripheral devices, adopts active control technology, has a simple control circuit, and is suitable for all flyback switching power supplies.

[0028] The above description is only an overview of the technical solution of the present application. In order to more clearly understand the technical means of the present application and implement it according to the contents of the specification, the following is a detailed description of the preferred embodiments of the present application in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 It is a structural schematic diagram of an existing flyback charging power supply provided by an embodiment of the present application;

[0030] Figure 2 It is a schematic block diagram of a switching power supply chip in a flyback switching power supply supporting a wide output voltage range;

[0031] Figure 3 This is a schematic diagram of a flyback switching power supply circuit that supports a wide output voltage range.

[0032] Figure 4 It is the internal signal waveform diagram of the flyback switching power supply supporting a wide output voltage range;

[0033] Figure 5 The present invention is a flow chart of a charging method of a flyback switching power supply supporting a wide output voltage range. DETAILED DESCRIPTION

[0034] The specific implementation methods of the present application are further described in detail below in conjunction with the accompanying drawings and examples. The following examples are used to illustrate the present application but are not intended to limit the scope of the present application.

[0035] First, the terms used in this application are explained.

[0036] USB-PD protocol: USB Power Delivery power transmission protocol, its standard voltages are 5V, 9V, 15V, and 20V, and their corresponding standard currents are shown in Table 1, which shows the standard voltage and current pairs.

[0037] Table 1

[0038]

[0039] In addition to the above standard voltage and current pairs, the charger can also be optimized according to special terminals to provide programmable power output. For the USB-PD protocol, each fixed standard voltage level corresponds to a programmable voltage range, and the corresponding relationship is shown in Table 2 below. Table 2 shows the programmable charging voltage range.

[0040] Table 2

[0041]

[0042] Figure 1 It is a structural diagram of an existing flyback switching power supply, such as Figure 1 As shown, the flyback switching power supply includes a switching power supply chip 11 , a primary coil 12 , a secondary coil 13 and an auxiliary coil 14 .

[0043] Among them, the primary coil 12, the secondary coil 13 and the auxiliary coil 14 have mutual inductance ( Figure 1 For the convenience of illustration, the auxiliary coil 14 and the secondary coil 13 are shown separately. In actual implementation, the primary coil 12, the secondary coil 13 and the auxiliary coil 14 are integrated).

[0044] The operating principle of the above-mentioned flyback switching power supply is: when K2 is closed and the primary coil 12 is turned on, the secondary coil 13 and the auxiliary coil 14 are disconnected; the input end of the flyback switching power supply is the coil storing electricity; when K2 is disconnected and the primary coil is disconnected, the primary coil 12 conducts the stored electricity to the secondary coil 13; the secondary coil 13 provides an output voltage and conducts part of the energy to the auxiliary coil 14; the auxiliary coil 14 charges the capacitor C1 to power the switching power supply chip 11.

[0045] According to the above working principle, the power supply of the switching power supply chip 11 comes from the induced voltage of the auxiliary coil 14. The induced voltage of the auxiliary coil 14 is subject to the voltage of the secondary coil 13 and the turns ratio between the secondary coil and the auxiliary coil.

[0046] When the power supply output voltage V OUT When the voltage is higher, the induced voltage on the auxiliary coil 14 becomes higher. To ensure that the chip operating voltage provided by the induced voltage on the auxiliary coil 14 is not too high, part of the coil energy will be wasted, thereby reducing the power efficiency and increasing the power consumption of the power supply.

[0047] When the power supply output voltage V OUT When the induction voltage is lower, the induction voltage on the auxiliary coil 14 becomes lower. When the induction voltage cannot make the switching power supply chip 11 generate a signal to control the power switch, the power supply cannot work normally.

[0048] Based on the above problems, the present application provides a flyback switching power supply supporting a wide output voltage range and a charging method for the power supply.

[0049] Figure 2 is a schematic block diagram of a switching power supply chip in a flyback switching power supply supporting a wide output voltage range provided by an embodiment of the present application, such as Figure 2 As shown, the switching power supply chip includes: a power supply circuit 21; a delay adjustment circuit 26, a pulse width modulation circuit 24, a first error amplifier 22, a second error amplifier 23, a driving circuit 29, an inverter 25, an AND gate circuit 27 and a control switch 28.

[0050] The first error amplifier 22 includes a first non-inverting input terminal, a first inverting input terminal and an output terminal, wherein the first non-inverting input terminal is connected to the first power output terminal of the power circuit 21, and the first inverting input terminal leads to the first pin (VFB) of the switching power chip.

[0051] The second error amplifier 23 includes a second non-inverting input terminal, a second inverting input terminal and an output terminal, wherein the second non-inverting input terminal is connected to the second power supply output terminal of the power supply circuit 21, and the second inverting input terminal leads to the second pin (VCC) of the switching power supply chip.

[0052] The pulse width modulation circuit 24 includes a first signal input terminal, a second signal input terminal and an output terminal, wherein the first signal input terminal is connected to the output terminal of the first error amplifier 22, and the second signal input terminal is connected to the third pin (CS) of the switching power supply chip.

[0053] The input end of the inverter circuit 25 and the input end of the drive circuit 29 are connected to the output end of the pulse width modulation circuit 24. The output end of the drive circuit 29 leads to the fifth pin (DRV) of the switch power chip.

[0054] The input end of the delay adjustment circuit 26 is connected to the output end of the first error amplifier 22 and the output end of the second error amplifier 23 respectively.

[0055] The input end of the gate circuit 27 is connected to the output end of the delay adjustment circuit 26 , the output end of the inverter circuit 25 , and the third power supply output end of the power supply circuit 21 , respectively.

[0056] The control switch 28 is connected to the output end of the AND gate circuit 27. The control switch 28 is used to control the connection or disconnection between the second pin (VCC) and the fourth pin (Vin).

[0057] The switching power supply chip further includes a ground pin (GND).

[0058] The power supply circuit also includes a working voltage output terminal (VDD) and a power supply input terminal.

[0059] Figure 3The schematic diagram of the structure of a flyback switching power supply supporting a wide output voltage range provided by an embodiment of the present application is shown in FIG. Figure 2 The switching power supply chip shown in the figure. Figure 3 As shown, the fourth pin (Vin) of the switching power chip is connected to the first diode D1, the second pin (VCC) of the switching power chip is connected to the capacitor C1, the first pin (VFB) of the switching power chip is connected to the resistors R1 and R2, the third pin (CS) of the switching power chip is connected to the switch K2 and the resistor R3, and the fifth pin (DRV) of the switching power chip controls the switch K2.

[0060] The operating principle of the above-mentioned flyback switching power supply supporting a wide output voltage range includes: when the pulse width modulation signal generates a SW=0 signal (falling edge signal), K2 is disconnected, and the second error amplifier 23 outputs a second error amplified signal eaout2 between the VCC signal inputted at the second pin and the second reference voltage Vref2; the first error amplifier 22 outputs a first error amplified signal eaout1 between the feedback voltage VFB inputted at the first pin and the first reference voltage Vref1; the first error amplified signal eaout1 and the second error amplified signal eaout2 are simultaneously inputted into the delay adjustment circuit 26. The delay adjustment circuit 26 outputs a square wave signal S_dly after a delay time, and the delay time is positively correlated with the voltage of the first error amplified signal eaout1, and the delay time is negatively correlated with the voltage of the second error amplified signal eaout2.

[0061] Based on the above process, it can be known that the control signal of the control switch 28 can be obtained through the delay adjustment circuit 26 after the delay time. After the control switch 28 is closed, the current on the auxiliary coil 33 begins to charge the capacitor 32. In this way, when the output voltage of the flyback switching power supply is high, the energy on the secondary coil 35 is first charged to the output capacitor C2 within the delay time, and a stable output voltage is provided to the load; when the square wave signal output by the delay adjustment circuit 26 is reached, the remaining energy on the secondary coil 35 is charged to the energy storage capacitor 32 through the auxiliary coil 33, thereby providing a suitable operating voltage for the flyback switching power supply chip supporting a wide output voltage range, which can solve the problem of insufficient or excessive operating voltage of the flyback switching power supply chip supporting a wide output voltage range when the output voltage of the flyback switching power supply changes.

[0062] refer to Figure 4 The internal signal waveform of the flyback switching power supply supporting a wide output voltage range is shown in the figure. on The corresponding waveform is the current on the primary coil, I offThe corresponding waveform is the current on the secondary coil or the auxiliary coil. When the pulse width modulation signal SW is at a high level, K2 is closed and only the primary coil has current. When the pulse width modulation signal SW is at a low level, K2 is disconnected and current flows through the secondary coil and the auxiliary coil. When the secondary coil is turned on, the voltage of the auxiliary coil senses the voltage of the secondary coil. The voltage of the auxiliary coil will be much higher than the VCC voltage of the power chip, but it will not act on the power chip until the auxiliary coil is turned on. At the falling edge of the pulse width modulation signal SW, the second error amplifier 23 compares the sampled VCC voltage signal with the second reference voltage Vref2 and generates a second error amplified signal eaout2. Combined with the result of the first error amplified signal eaout1, a delayed square wave signal S_dly can be obtained, and then the enable signal of the control switch 28 is obtained. After a period of delay, the current on the auxiliary coil will charge the energy storage capacitor 32. According to Figure 4 It can be seen that when the SW falling edge VCC>Vref2 is detected, the output second error amplification signal eaout2 is too small, and the square wave signal S_dly=1 is output after a delay of Tdly1 time; when the SW falling edge VCC<Vref2 is detected, the output second error amplification signal eaout2 is too large, and S_dly=1 after a delay of Tdly2 time, where Tdly1>Tdly2.

[0063] In summary, the flyback switching power supply supporting a wide output voltage range provided in the present embodiment is provided with an additional delay adjustment circuit, through which the delay adjustment circuit determines the delay length of the square wave signal according to the first error amplification signal and the second error amplification signal; so that the secondary coil of the flyback switching power supply provides the output voltage for charging the load within the delay length, and when the delay length reaches the square wave signal position, the residual energy of the secondary coil charges the energy storage capacitor through the auxiliary coil; the problem of insufficient or excessive working voltage of the flyback switching power supply supporting a wide output voltage range when the power supply output voltage changes can be solved; because the energy on the coil can be flexibly utilized through time division multiplexing technology, when the secondary coil is turned on, the energy on the secondary coil is first used to provide power output; when the auxiliary coil is turned on, the residual energy on the secondary coil is used to provide working voltage for the primary switching power supply chip; avoiding the switching power supply chip from wasting the energy of the secondary coil.

[0064] In addition, the switching power supply chip has a high degree of integration, does not require additional peripheral devices, adopts active control technology, has a simple control circuit, and is suitable for all flyback switching power supplies.

[0065] Figure 5 is a flowchart of a flyback switching power supply method supporting a wide output voltage range provided by an embodiment of the present application. Figure 3 The flyback switching power supply shown in FIG. is used as an example for explanation. The method includes at least the following steps:

[0066] Step 501, when the secondary coil is turned on, a delay time is determined based on the output voltage of the first error amplifier and the output voltage of the second error amplifier, wherein the delay time is positively correlated with the output voltage of the first error amplifier and negatively correlated with the output voltage of the second error amplifier.

[0067] Optionally, at the falling edge of the pulse width modulation signal output by the pulse width modulation circuit, the second error amplifier compares the voltage signal sampled through the second pin with the second reference voltage output by the second voltage output terminal, and generates a second error amplified signal; the second error amplified signal is combined with the first error amplified signal output by the first error amplifier to obtain a delay control square wave signal with a delay time length.

[0068] The delayed control square wave signal is used to generate a control signal for controlling the control switch.

[0069] Step 502: providing output voltage to the load through the secondary coil within the delay time.

[0070] Step 503, when the current duration reaches the delay duration, the control switch is controlled to close, so that the secondary coil stops conducting, and the auxiliary coil stores energy for the energy storage capacitor.

[0071] The closing time is the width of the square wave signal output by the delay adjustment circuit.

[0072] For related contents, please refer to the above embodiment, which will not be described in detail in this embodiment.

[0073] In summary, the power charging method provided in this embodiment determines the delay time based on the output voltage of the first error amplifier and the output voltage of the second error amplifier when the secondary coil is turned on, and the delay time is positively correlated with the output voltage of the first error amplifier and negatively correlated with the output voltage of the second error amplifier; during the delay time, the output voltage is provided to the load through the secondary coil; when the current time reaches the delay time, the control switch is controlled to close so that the secondary coil stops conducting, and the auxiliary coil stores energy in the energy storage capacitor; the problem of insufficient or excessive working voltage of the switching power supply chip when the power supply output voltage changes can be solved; because the energy on the coil can be flexibly utilized through time division multiplexing technology, when the secondary coil is turned on, the energy on the coil is first used to provide power output; when the auxiliary coil is turned on, the remaining energy on the coil is used to provide working voltage for the primary switching power supply chip, avoiding the switching power supply chip from wasting energy of the secondary coil.

[0074] The technical features of the above-described embodiments may be arbitrarily combined. To make the description concise, not all possible combinations of the technical features in the above-described embodiments are described. However, as long as there is no contradiction in the combination of these technical features, they should be considered to be within the scope of this specification.

[0075] The above-mentioned embodiments only express several implementation methods of the present application, and the descriptions thereof are relatively specific and detailed, but they cannot be understood as limiting the scope of the invention patent. It should be pointed out that, for a person of ordinary skill in the art, several variations and improvements can be made without departing from the concept of the present application, and these all belong to the protection scope of the present application. Therefore, the protection scope of the patent of the present application shall be subject to the attached claims.

Claims

1. A flyback switching power supply supporting a wide output voltage range, characterized in that: The invention comprises a switching power supply chip, wherein the switching power supply chip comprises: A power supply circuit for generating a low voltage for internal operation of the switching power supply chip; A first error amplifier having a first non-inverting input terminal connected to a first power supply output terminal of the power supply circuit and a first inverting input terminal leading to a first pin of the switching power supply chip; A second error amplifier whose second in-phase input terminal is connected to the second power supply output terminal of the power supply circuit and whose second inverting input terminal leads to the second pin of the switching power supply chip; A pulse width modulation circuit having a first signal input terminal connected to the output terminal of the first error amplifier and a second signal input terminal leading to a third pin of the switching power supply chip; an inverting circuit connected to the output end of the pulse width modulation circuit; A driving circuit connected to the output end of the pulse width modulation circuit; the output end of the driving circuit leads to the fifth pin of the switching power supply chip; A delay adjustment circuit whose input end is respectively connected to the output end of the first error amplifier and the output end of the second error amplifier; an AND gate circuit whose input ends are respectively connected to the output end of the delay adjustment circuit, the output end of the inverter circuit and the third power supply output end of the power supply circuit; and, A control switch connected to the output end of the AND gate circuit, wherein the control switch is used to control the connection or disconnection between the second pin and the fourth pin.

2. The flyback switching power supply supporting a wide output voltage range according to claim 1, characterized in that: The switching power supply chip also includes a ground pin.

3. The flyback switching power supply supporting a wide output voltage range according to claim 1, characterized in that: The power supply circuit also includes a working voltage output terminal and a power supply input terminal.

4. The flyback switching power supply supporting a wide output voltage range according to any one of claims 1 to 3, characterized in that: The delay adjustment circuit outputs a square wave signal after a delay time; wherein the delay time is negatively correlated with the output voltage of the second error amplifier; and positively correlated with the output voltage of the first error amplifier.

5. A charging method, characterized in that: Used in a flyback switching power supply supporting a wide output voltage range as claimed in any one of claims 1 to 4, the method comprising: When the secondary coil of the flyback switching power supply is turned on, a delay time is determined based on an output voltage of the first error amplifier and an output voltage of the second error amplifier, wherein the delay time is positively correlated with the output voltage of the first error amplifier and negatively correlated with the output voltage of the second error amplifier; During the delay time, the output voltage is provided to the load through the secondary coil; When the current duration reaches the delay duration, the control switch is controlled to close, and the auxiliary coil of the flyback switching power supply stores energy for the energy storage capacitor.

6. The method according to claim 5, further comprising: At the falling edge of the pulse width modulation signal output by the pulse width modulation circuit, the second error amplifier compares the voltage signal sampled by the second pin with the second reference voltage output by the second voltage output terminal of the power supply circuit, and generates a second error amplification signal; The second error amplified signal and the first error amplified signal output by the first error amplifier are combined to obtain a delay control square wave signal having the delay time length, and the delay control square wave signal is used to generate a control signal for controlling the control switch.

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