TWI767432B - Zero-voltage switching power control system - Google Patents

Abstract

The present invention discloses a zero-voltage switching power supply control system, which includes a power supply controller, a rectifier unit, a power supply unit, a transformer unit, a primary side switching unit, an auxiliary switching unit, an output unit and a current sensing unit for realizing flyback conversion , and the power controller includes a power pin, a ground pin, a primary driving pin, a voltage sensing pin, an auxiliary driving pin and an auxiliary winding sensing pin. In particular, the present invention controls the auxiliary switching unit to influence the primary side winding by the auxiliary winding to reduce the drain voltage of the primary side switching unit, so that the primary side switching unit is only turned on when the drain voltage of the primary side switching unit is the lowest voltage, thereby reducing the drain voltage of the primary side switching unit. Significantly reduce switching losses and improve power conversion efficiency.

Description

Zero voltage switching power control system

The invention relates to a zero-voltage switching power supply control system, in particular, an auxiliary switching unit is used to connect to an auxiliary winding, and the power supply controller generates an auxiliary driving signal to control the opening and closing of the auxiliary switching unit, and then the auxiliary winding affects the primary side winding to reduce the drain voltage of the primary side switching unit, so that the primary drive signal generated by the power controller can turn on the primary side switching only when the drain voltage of the primary side switching unit is the lowest voltage or close to zero voltage unit, so as to greatly reduce the switching loss and improve the power conversion efficiency.

With the advancement of electronic technology and the continuous improvement of semiconductor manufacturing process, the related end product manufacturers also continue to introduce various electronic products with more powerful functions and high integration, and different electronic devices require specific power sources to provide the required power, such as Integrated circuits (ICs) require 1.2V low-voltage DC, electric motors require 12V DC, and backlight modules require high-voltage power supplies of hundreds of volts or more. Therefore, high-quality and high-efficiency power conversion devices are required. The power supply is used to meet the required power supply.

Among the current power supplies, using a switching power supply (Switching Power Supply) with Pulse Width Modulation (PWM) characteristics is one of the most common methods because it can achieve a relatively high power conversion efficiency . Take the flyback power converter as For example, it mainly includes a power supply controller, a transformer, a switching unit, a current sensing resistor, a secondary side rectifier and an output capacitor, and the transformer includes a primary side winding and a secondary side winding, among which the power supply controller, the primary side winding, and the switching unit and the current sensing resistor are connected in series to form the primary side loop, while the secondary side winding, the secondary side rectifier and the output capacitor are connected in series to form the secondary side loop. The power controller generates a PWM drive signal to drive the switching unit connected to the transformer, such as a power transistor, and the PWM drive signal itself has a high-speed switching frequency, which can quickly turn on and off the switching unit periodically to turn on and off the flow through the transformer. The purpose of the primary side winding and the current of the switching unit is to convert the input voltage into different output voltages by means of the electromagnetic induction between the primary side winding and the secondary side winding in the transformer and the preset winding ratio. Supply power to external loads to achieve power conversion function.

In addition, the primary side winding is composed of magnetizing inductance (Magnetizing Inductance) and leakage inductance. The reason for the generation of leakage inductance is because the primary side magnetic flux (Magnetic Flux) cannot be coupled to the secondary side, and the stored energy must be transferred to other Local consumption, the energy in the leakage inductance is the reason why the drain of the switching unit will generate a huge voltage surge when it is turned off.

When the switching unit is turned on and turned on, the current flows through the primary side winding, that is, the input power is to store energy in the primary side winding. When the switching unit is turned off and turned off, because the energy stored in the leakage inductance cannot be coupled to the secondary side, it will form an LC resonance with the capacitance across the drain-source of the switching unit, and the drain-source of the switching unit will form an LC resonance. Voltage surges are generated at both ends of the poles. After the LC resonance, the drain-source cross-voltage begins to slowly decrease from the peak value to a certain fixed value, which is called the knee (Knee), indicating that the energy stored in the magnetizing inductance has been completely released. At this time, the secondary side The current is completely zero and is in an open circuit state, where the circuit on the primary side forms an RLC resonant tank, which produces an underdamped resonance or ringing, and has a resonant frequency, so the time of the valley can be predicted based on the resonant frequency.

Further, when the switching unit is rapidly turned on and off by the PWM drive signal in a periodic manner, discontinuities in related electrical signals, such as current and voltage, will result in switching loss, and the overall power conversion efficiency will decrease. . For example, if the switching unit can be turned on when the drain-source voltage is the lowest, that is, the valley voltage, the switching loss can be greatly reduced. Therefore, in the prior art, it is usually selected when the drain-source voltage of the switching unit falls to a low voltage, and the current of the magnetizing inductance is zero at this time, and the switching unit is turned on, which is collectively referred to as quasi-resonance. QR) switching or valley switching, the main reason is that the energy loss when the switching unit is turned on at this time is less, which can reduce the problem of switching loss.

Usually, the practice of quasi-resonant switching or valley switching is to first estimate the time when the knee occurs, and calculate the valley switching time according to the frequency of the ringing, so as to use it as the time point to turn on the switching unit, or to select a certain time. The switch is only at the bottom of the valley, such as the third valley bottom. Although the above switching on method can moderately reduce the switching loss, the characteristics of each electrical component will affect the knee time and the frequency of damping, so it needs to be adjusted or calculated with the current circuit, otherwise it cannot be accurately at the bottom of the valley. The switching is performed to open the switching unit. In addition, when the load is light, it needs to be opened later, but when the load is heavy and light, it needs to be opened earlier.

Obviously, the change of any component in the circuit or the change of electrical characteristics requires readjustment or calculation of the opening time, resulting in a lack of flexibility and inconvenience in practical applications, so the disadvantage of the above-mentioned conventional technology is that with the change of the application environment, different loads The optimal turn-on time required by different degrees is also different. The power controller cannot predict in advance and dynamically adjust to set the corresponding turn-on time. Therefore, in practice, it is difficult to meet most of the existing application fields.

Therefore, there is a great need for a novel design of a zero-voltage switching power supply control system, which uses an auxiliary switching unit to connect to the auxiliary winding, and the power supply controller generates an auxiliary driving signal to control the opening and closing of the auxiliary switching unit, and then the auxiliary winding affects the primary. side winding, lowering the primary side switching unit Therefore, the primary drive signal generated by the power controller can turn on the primary side switching unit when the drain voltage of the primary side switching unit is the lowest voltage, or when it is close to zero voltage, so as to greatly reduce the switching loss. The power conversion efficiency is improved, thereby overcoming the problems of the prior art.

The main purpose of the present invention is to provide a zero-voltage switching power supply control system, which includes a power supply controller, a rectifier unit, a power supply unit, a transformer unit, a primary side switching unit, an auxiliary switching unit, an output unit and a current sensing unit, for realizing Flyback power conversion function, and the power controller includes a power pin, a ground pin, a primary drive pin, a voltage sensing pin, an auxiliary drive pin and an auxiliary winding sense pin, wherein the transformer unit includes a primary coupled to each other The side winding, the auxiliary winding and the secondary side winding, and the primary side switching unit and the auxiliary switching unit may comprise MOSFETs, GaN field effect transistors, or SiC-MOSFETs.

The rectifier unit receives the external input power, and generates rectified power after rectification, and the rectifier unit is connected to the ground potential through the auxiliary capacitor, and the power unit also receives the external input power, and after processing, generates and outputs the power supply voltage to the power pin , which is used for the operation of the power controller.

The transformer unit includes a primary side winding, an auxiliary winding and a secondary side winding coupled with each other, wherein one end of the primary side winding is connected to the rectifier unit for receiving rectified power.

The drain of the primary side switching unit is connected to the other end of the primary side winding, the gate of the primary side switching unit is connected to the primary driving pin, and the source of the primary side switching unit is connected to the voltage sensing pin.

One end of the current sensing unit is connected to the voltage sensing pin, and the other end of the current sensing unit is connected to the ground potential, and the current sensing signal is generated by the voltage sensing pin.

The drain of the auxiliary switching unit is connected to the rectifier unit to receive the rectified power supply, the gate of the auxiliary switching unit is connected to the auxiliary driving pin, the source of the auxiliary switching unit is connected to one end of the auxiliary winding and the auxiliary winding sensing pin, and the auxiliary winding The other end is connected to ground potential. In addition, the source of the auxiliary switching unit generates an auxiliary winding voltage, and the auxiliary winding voltage corresponds to the drain voltage of the primary side switching unit, and in particular, the drain voltage refers to the drain voltage of the primary side switching unit.

Furthermore, the drain of the auxiliary switching unit is further connected to the ground potential through the auxiliary capacitor.

One end of the output unit is connected to one end of the secondary side winding to generate output power and supply power to the load connected to the output unit, and the other end of the secondary side winding is connected to the ground potential.

The above-mentioned power supply controller generates a primary driving signal and an auxiliary driving signal by performing a zero-voltage switching control operation, wherein the primary driving signal is transmitted to the primary driving pin, and the auxiliary driving signal is transmitted to the auxiliary driving pin. Essentially, the primary drive signal is a pulse width modulated (PWM) signal with a PWM frequency, and includes a periodic turn-on level and a turn-off level to periodically turn on or turn off the primary side switching unit, wherein the turn-on level The on-time is maintained, and the off-level is maintained for the off-time. In particular, the PWM frequency is determined according to the load level of the load, and the on-time is determined according to the output power.

Specifically, the zero-voltage switching control operation includes: when the primary side switching unit is turned off after the auxiliary switching unit is turned off, detecting and judging whether the auxiliary winding voltage drops to the knee; The time between when the side switching unit is turned off and when the auxiliary winding voltage drops to the knee is regarded as the demagnetization time, and the turn-on delay time is calculated; then, after waiting for the turn-on delay time, the auxiliary drive signal is driven to turn on the auxiliary switching unit, and the setting and adjustment Variable or calculated auxiliary on-time; waiting for auxiliary After the turn-on time, the auxiliary driving signal is driven to turn off the auxiliary switching unit, and the interval time is calculated; finally, after the waiting interval time, the primary driving signal is driven to turn on the primary side switching unit.

Therefore, the turn-off time of the primary-side switching unit includes demagnetization time, turn-on delay time, auxiliary turn-on time, and interval time.

In general, the present invention uses the auxiliary switching unit to connect to the auxiliary winding, and the power supply controller generates an auxiliary driving signal to control the opening and closing of the auxiliary switching unit, and then the auxiliary winding affects the primary side winding, reducing the primary side switching unit. Drain voltage, so that the primary drive signal generated by the power controller can turn on the primary side switching unit when the drain voltage of the primary side switching unit is the lowest voltage, or when it is close to zero voltage, so as to greatly reduce the switching loss and improve the Power conversion efficiency.

10: Power Controller

20: Rectifier unit

21: Power supply unit

30: Transformer unit

50: Output unit

60: Current sensing unit

CA: auxiliary capacitor

CB: auxiliary capacitor

IDS: Primary side switching unit current

IP: Primary side current

IS: Secondary side current

LA: auxiliary winding

LP: Primary side winding

LS: Secondary side winding

QA: Auxiliary switching unit

QP: Primary side switching unit

RL: load

T1: Power pin

T2: Ground pin

T3: Primary driver pin

T4: Voltage sensing pin

T5: Auxiliary driver pin

T6: Auxiliary winding sensing pin

VAC: External input power

VCS: Current Sense Signal

VDD: Power supply voltage

VDP: Drain voltage

VGA: Auxiliary drive signal

VGND: ground potential

VGP: Primary drive signal

Vb: rectified power supply

VOUT: output power

VZVS: auxiliary winding voltage

TSW PWM: Frequency Period

TPON: On Time

TPOFF: off time

TFW: Demagnetization time

TD: Turn on delay time

TAON: auxiliary on-time

TDEAD: interval time

K: knee

The first figure shows a system schematic diagram of a zero-voltage switching power supply control system according to an embodiment of the present invention.

The second figure shows an operation waveform diagram of the zero-voltage switching power supply control system according to the embodiment of the present invention.

The third figure shows a simplified operation waveform diagram of the zero-voltage switching power supply control system according to the embodiment of the present invention.

The embodiments of the present invention will be described in more detail below with reference to the drawings and component symbols, so as to enable those skilled in the art to implement them after studying the description.

Please refer to the first figure and the second figure at the same time, which are a system schematic diagram and an operation waveform diagram of the zero-voltage switching power supply control system according to the first embodiment of the present invention, respectively. As shown in the first and second figures, the zero-voltage switching power control system according to the first embodiment of the present invention includes a power controller 10, a rectifier unit 20, a power supply The source unit 21 , the transformer unit 30 , the primary side switching unit QP, the auxiliary switching unit QA, the output unit 50 and the current sensing unit 60 are used to realize a flyback power conversion function.

Specifically, the power controller 10 includes a power pin T1, a ground pin T2, a primary driving pin T3, a voltage sensing pin T4, an auxiliary driving pin T5 and an auxiliary winding sensing pin T6, and the transformer unit 30 The primary side winding LP, the auxiliary winding LA and the secondary side winding LS may be coupled to each other. In addition, the primary side switching unit QP and the auxiliary switching unit QA may comprise metal-oxide-semiconductor (MOS) transistors, or Gallium Nitride Field Effect Transistor (GaN (Gallium Nitride) FET), or Silicon Carbide-Metal Oxide Semi Field Effect Transistor (SiC-MOSFET).

Further, the rectifying unit 20 receives the external input power VAC, and rectifies the external input power VAC to generate the rectified power Vb. In particular, the rectifying unit 20 is further connected to the ground potential VGND through the auxiliary capacitor CB to provide filtering for the rectified power Vb. The power supply unit 21 also receives the external input power VAC, and generates and outputs the power supply voltage VDD after processing, and the power supply pin T1 receives the power supply voltage VDD for the operation of the power supply controller 10 . , In addition, one end of the primary side winding LP is connected to the rectifier unit 20 to receive the rectified power supply Vb, the drain electrode of the primary side switching unit QP is connected to the other end of the primary side winding LP, and the gate electrode of the primary side switching unit QP is connected to the primary drive pin T3, and furthermore, the source of the primary side switching unit QP is connected to the voltage sensing pin T4.

One end of the current sensing unit 60 is connected to the voltage sensing pin T4, and the other end of the current sensing unit 60 is connected to the ground potential VGND, and a current sensing signal VCS is generated at the voltage sensing pin T4.

以接收整流電源Vb，輔助切換單元QA的閘極連接輔助驅動接腳T5，而輔助切換單元QA的 源極連接至輔助繞組LA的一端以及輔助繞組感測接腳T6，且輔助繞組LA的另一端連接至接地電位VGND。此外，輔助切換單元QA的汲極進一步經由輔助電容CA而連接該接地電位VGND。再者，輔助切換單元QA的源極產生輔助繞組電壓VZVS，其中輔助繞組電壓VZVS是對應於初級側切換單元QP的汲極電壓，而汲極電壓是指初級側切換單元QP的汲極的電壓。 The drain of the auxiliary switching unit QA is connected to the power supply unit 21

In order to receive the rectified power supply Vb, the gate of the auxiliary switching unit QA is connected to the auxiliary driving pin T5, and the source of the auxiliary switching unit QA is connected to one end of the auxiliary winding LA and the auxiliary winding sensing pin T6, and the other side of the auxiliary winding LA. One end is connected to the ground potential VGND. In addition, the drain of the auxiliary switching unit QA is further connected to the ground potential VGND via the auxiliary capacitor CA. Furthermore, the source of the auxiliary switching unit QA generates the auxiliary winding voltage VZVS, wherein the auxiliary winding voltage VZVS corresponds to the drain voltage of the primary side switching unit QP, and the drain voltage refers to the voltage of the drain of the primary side switching unit QP. .

One end of the output unit 50 is connected to one end of the secondary side winding LS to generate the output power VOUT and supply power to the load RL connected to the output unit 50, and the other end of the secondary side winding LS is connected to the ground potential VGND.

More specifically, the power controller 10 performs a zero-voltage switching control operation to generate a primary driving signal VGP and an auxiliary driving signal VGA, wherein the primary driving signal VGP is transmitted to the primary driving pin T3, and the auxiliary driving signal VGA is transmitted to the auxiliary driving signal VGA. Drive pin T5.

The above-mentioned primary drive signal VGP is substantially a pulse width modulation (Pulse Width Modulation, PWM) signal, and has a PWM frequency or a PWM period TSW, and includes a periodic turn-on level and a turn-off level for periodic turn-on or turn-off. The primary-side switching unit QP is turned off, the on-level is maintained for the on-time TPON, and the off-level is maintained for the off-time TPOFF. In particular, the PWM frequency or the PWM period TSW is determined according to the load level of the load RL, and the on-time TPON is determined according to the output power VOUT, and the selection of the PWM frequency and the on-time TPON is a common practice of flyback power conversion. Known in the technical field, so will not be further explained in detail below.

More specifically, the zero-voltage switching control operation includes the following steps. However, it should be noted that since the auxiliary winding voltage VZVS itself corresponds to the drain voltage VDP of the primary side switching unit QP, the following operations using the auxiliary winding voltage VZVS are actually for the drain voltage of the primary side switching unit QP VDP.

First, the primary side switching unit QP detects and determines whether the auxiliary winding voltage VZVS drops to the knee (Knee) K when the auxiliary switching unit QA is turned off after the auxiliary switching unit QA is turned off, The turning point when the descent turns into a steeper and more abrupt descent curve. Generally speaking, it is regarded as the turning point of the knee K, which means that the demagnetization of the transformer unit 30 has been completed, and the judgment method can be realized by detecting whether the descending slope of the auxiliary winding voltage VZVS is greater than a predetermined slope value. It belongs to the conventional technology and will not be described in detail below.

When the auxiliary winding voltage VZVS drops to the knee K, the time between when the primary side switching unit QP is turned off until the auxiliary winding voltage VZVS drops to the knee K is regarded as the demagnetization time TFW, and the whole period of the demagnetization time TFW can generally be regarded as It is called the Free-wheeling phase, after which the auxiliary winding voltage VZVS enters the underdamped resonance, which is generally called the Oscillation phase, and then the turn-on delay time TD is calculated or set. After waiting for the turn-on delay time TD, the auxiliary driving signal VGA is driven to turn on the auxiliary switching unit QA, and then the auxiliary on-time TAON is generated by setting, modulating or calculating.

After waiting for the auxiliary turn-on time TAON, drive the auxiliary driving signal VGA to turn off the auxiliary switching unit QA, then wait for a preset interval time TDEAD, preferably, the interval time TDEAD can be preset to be between 150ns and 250ns, and then drive The primary driving signal VGP is used to turn on the primary side switching unit QP, in other words, the primary side switching unit QP and the auxiliary switching unit QA are not turned on at the same time, but are separated by the interval time TDEAD. Next, the primary-side switching unit QP is turned off after maintaining the on-time TPON, thereby completing the periodic operation of the primary driving signal VGP and the auxiliary driving signal VGA.

In general, the above-mentioned off time TPOFF includes the demagnetization time TFW, the turn-on delay time TD, the auxiliary on-time TAON and the interval time TDEAD, and the auxiliary switching unit Q is the demagnetization time TFW, turn on after the turn-on delay time TD, and The auxiliary turn-on time TAON is maintained and then turned off, in particular, the primary-side switching unit QP is then turned on after the interval time TDEAD has elapsed.

Further, the main purpose of the auxiliary driving signal VGA is to reduce the drain voltage of the primary side switching unit QP, that is, when the primary side switching unit QP is turned on, it can greatly reduce the drain voltage of the primary side switching unit QP, as shown in the figure As shown in , even close to zero voltage, thus reducing switching losses, can further improve the overall power conversion efficiency. Obviously, the more the auxiliary on-time TAON is increased, the lower the drain voltage of the primary-side switching unit QP will be. However, if the auxiliary on-time TAON is too large, the interval time TDEAD will be too small to ensure the primary-side switching unit QP and the auxiliary switching unit. QA will not be turned on at the same time, so under the condition that the interval time TDEAD must meet the necessary condition of 150ns to 250ns, the auxiliary on-time TAON can have a maximum value, so that the drain voltage of the primary side switching unit QP has a minimum value.

Therefore, the auxiliary on-time TAON can be set, modulated or calculated according to the requirements of the application system, so it is very specific and flexible in practical applications. Of course, compared with the traditional flyback converter, the present invention additionally uses the auxiliary driving signal VGA, so it will consume further power. However, after the actual measurement, it is found that the power consumed by the auxiliary driving signal VGA is still far less than the reduced switching loss. .

As mentioned above, the auxiliary on-time TAON can be generated by setting, adjusting or calculating, and further, it can be divided into adjustable setting operation, adaptive adjusting operation or calculating operation, and the individual descriptions are as follows.

The adjustable setting operation is to individually set the auxiliary on-time TAON according to the voltage of the external input power VAC and the load level of the load RL. Light load, medium load and full load. In general, the auxiliary on-time TAON is extended as the voltage of the external input power VAC is higher, and when the load is heavier, the auxiliary on-time TAON is set to be shorter.

Alternatively, in the adjustable setting operation, when the voltage of the external input power supply VAC is 90Vac, first set the auxiliary conduction time TAON to a certain initial conduction time, and use the initial conduction time when the voltage of the external input power supply VAC is 115 or 230Vac. time, and according to the voltage of the external input power supply VAC, the corresponding auxiliary conduction time TAON is set in a proportional amplification method. In other words, the auxiliary on-time TAON is set in proportion to the voltage of the external input power supply VAC.

If the adaptive modulation operation is used, it includes judging whether the auxiliary winding voltage VZVS is lower than a certain threshold voltage value, and when the auxiliary winding voltage VZVS is not lower than the threshold voltage value, in a cycle-to-cycle manner (cycle by cycle), change and set the auxiliary on-time TAON until the auxiliary winding voltage VZVS is lower than the threshold voltage value. Since the auxiliary winding voltage VZVS will decrease with the increase of the auxiliary conduction time TAON, in practice, a shorter auxiliary conduction time TAON is used first, and the auxiliary conduction time TAON is gradually increased, so that the auxiliary winding voltage VZVS is lower than the temporary auxiliary conduction time TAON. Limit the voltage value, and turn on and turn on the primary side switching unit QP.

：

，其中V_b為整流電源，V_or為初級側切換單元QP的汲極電壓VDP在欠阻尼諧振的最大振幅電壓，T_r為欠阻尼諧振的週期。上述的計算式主要是依據能量不滅頂律而推導，包含：

，其中L_m為初級側繞組LP的電感值，I_vspk為變壓器單元30的激磁電流Img的電流峰值，C_oss為初級側切換單元QP的汲極的寄生電容。 In addition, referring to the third figure, the simplified operation waveform diagram of the zero-voltage switching power supply control system according to the embodiment of the present invention is similar to the second figure, but the period of the underdamped resonance has been shortened and simplified, and the above calculation operation includes: The auxiliary on-time is calculated and set according to the following formula, which is expressed as

:

, where V _b is the rectified power supply, V _or is the maximum amplitude voltage of the drain voltage _VDP of the primary side switching unit QP at the underdamped resonance, and Tr is the period of the underdamped resonance. The above calculation formula is mainly derived based on the law of energy immortality, including:

, where L _m is the inductance value of the primary side winding LP, I _vspk is the current peak value of the magnetizing current Img of the transformer unit 30 , and _Coss is the parasitic capacitance of the drain of the primary side switching unit QP.

In addition, another simple calculation method of the auxiliary conduction time is: auxiliary conduction time=(voltage of the external input power supply x P1)+P2, where P1 is the first parameter, P2 is the second parameter, and the first parameter is 0.98~0.99 ns, and the second parameter is between 31.1 and 31.9 ns. It should be noted that this formula essentially uses the way that the auxiliary on-time TAON increases linearly with the voltage of the external input power supply VAC to reduce the drain voltage of the primary side switching unit QP and reduce the switching loss.

To sum up, the main feature of the present invention is that the auxiliary switching unit is connected to the auxiliary winding, and the power supply controller generates an auxiliary driving signal to control the opening and closing of the auxiliary switching unit, and then the auxiliary winding affects the primary side winding and reduces the primary side winding. Switch the drain voltage of the unit, so that the primary drive signal generated by the power controller can turn on the primary side switching unit when the drain voltage of the primary side switching unit is the lowest voltage, or when it is close to zero voltage, so as to greatly reduce the switching loss and improve power conversion efficiency.

Further, for the general flyback system that can only achieve low-voltage switching, it is mainly to use a higher coil ratio, or use a quasi-resonant controller to perform when the drain voltage of the primary-side switching unit drops to a low valley voltage. Switching on and on, if you want to achieve zero voltage switching (ZVS), you must use ACF or AHB architecture, or you need to add additional windings, which will lead to a significant increase in cost and unrealistic In contrast to the present invention, the auxiliary winding LA is shared, or combined with the synchronous rectification control of the secondary measurement, the ZVS control signal can be adjusted according to the input voltage and load or coil ratio of the overall system, and the ZVS control signal can be adjusted slowly from the preset width. Adjust and modulate to the most suitable ZVS switching point, so as to improve the overall power conversion efficiency of the system.

The above descriptions are only used to explain the preferred embodiments of the present invention, and are not intended to limit the present invention in any form. Therefore, any modification or change of the present invention should be made within the same spirit of the invention. , all should still be included in the scope of the intended protection of the present invention.

10: Power Controller

20: Rectifier unit

21: Power supply unit

30: Transformer unit

50: Output unit

60: Current sensing unit

CA: auxiliary capacitor

CB: auxiliary capacitor

IDS: Primary side switching unit current

IP: Primary side current

IS: Secondary side current

LA: auxiliary winding

LP: Primary side winding

LS: Secondary side winding

QA: Auxiliary switching unit

QP: Primary side switching unit

RL: load

T1: Power pin

T2: Ground pin

T3: Primary driver pin

T4: Voltage sensing pin

T5: Auxiliary driver pin

T6: Auxiliary winding sensing pin

VAC: External input power

VCS: Current Sense Signal

VDD: Power supply voltage

VDP: Drain voltage

VGA: Auxiliary drive signal

VGND: ground potential

VGP: Primary drive signal

Vb: rectified power supply

VOUT: output power

VZVS: auxiliary winding voltage

Claims (7)

A zero-voltage switching power control system is used to realize a flyback power conversion function, including: a power controller, including a power pin, a ground pin, a primary drive pin, a voltage sense pin A measuring pin, an auxiliary driving pin and an auxiliary winding sensing pin; a rectifier unit, which receives and rectifies an external input power to generate a rectified power supply, and the rectifier unit is connected to a ground through an auxiliary capacitor electric potential; a power supply unit, which receives the external input power, and generates and outputs a power supply voltage after processing, the power supply pin receives the power supply voltage for the operation of the power supply controller; a transformer unit includes a primary coupled to each other side winding, an auxiliary winding and a secondary side winding, one end of the primary side winding is connected to the rectifier unit to receive the rectified power supply; a primary side switching unit, a drain of the primary side switching unit is connected to a At the other end, a gate of the primary-side switching unit is connected to the primary driving pin, a source of the primary-side switching unit is connected to the voltage sensing pin; a current sensing unit, one end of the current sensing unit is connected to to the voltage sensing pin, the other end of the current sensing unit is connected to the ground potential, the voltage sensing pin generates a current sensing signal; an auxiliary switching unit, a drain of the auxiliary switching unit is connected The power supply unit receives the power supply voltage, a gate of the auxiliary switching unit is connected to the auxiliary driving pin, a source of the auxiliary switching unit is connected to one end of the auxiliary winding and the auxiliary winding sensing pin, the auxiliary switching unit is connected to the sensing pin. The other end of the winding is connected to the ground potential, the source of the auxiliary switching unit generates an auxiliary winding voltage, the auxiliary winding voltage is a drain voltage corresponding to the primary side switching unit, and the drain voltage is the primary side a voltage of the drain of the switching unit, the drain of the auxiliary switching unit is further connected to the ground potential through an auxiliary capacitor; and an output unit, one end of the output unit is connected to one end of the secondary side winding to generate an output power and supply power to a load connected to the output unit, and the other end of the secondary side winding is connected to the ground potential, wherein the power controller performs a zero-voltage switching control operation to generate a primary drive signal and an auxiliary drive signal, the primary drive signal is sent to the primary drive pin, and the auxiliary drive signal is sent to the auxiliary drive Pin, the primary drive signal is a pulse width modulation (Pulse Width Modulation, PWM) signal, has a PWM frequency, and includes a periodic turn-on level and a turn-off level for periodic turn-on or turn-off In the primary side switching unit, the on-level is maintained for an on-time, the off-level is maintained for an off-time, the PWM frequency is determined according to a load level of the load, and the on-time is determined according to the output power , the zero-voltage switching control operation includes: when the primary side switching unit is turned off after the auxiliary switching unit is turned off, detecting and judging whether the auxiliary winding voltage drops to a knee; when the auxiliary winding voltage drops to the knee When the primary-side switching unit is turned off until the auxiliary winding voltage drops to the knee, the time between when the auxiliary winding voltage drops to the knee is regarded as a demagnetization time, and the primary-side switching unit enters an underdamped resonance, which is calculated by the power supply controller. a turn-on delay time; after waiting for the turn-on delay time, drive the auxiliary driving signal to turn on the auxiliary switching unit, and set, modulate or calculate an auxiliary on-time; after waiting for the auxiliary on-time, drive the auxiliary driving signal to turn off the auxiliary switching unit, and calculating an interval time; and after waiting for the interval time, driving the primary drive signal to turn on the primary side switching unit, the turn-off time includes the demagnetization time, the turn-on delay time, the auxiliary turn-on time and the interval time. The zero-voltage switching power control system as claimed in claim 1, wherein the primary side switching unit and the auxiliary switching unit comprise a metal-oxide-semiconductor (MOS) transistor, or a gallium nitride field effect transistor (GaN (Gallium Nitride) FET), or a silicon carbide-metal oxide semi-field effect transistor (SiC-MOSFET). The zero-voltage switching power control system as claimed in claim 1, wherein the voltages of the external input power include 90, 115 and 230Vac, and the load levels include a very light load, a light load, a medium load and a full load, And the auxiliary on-time is generated by an adjustable setting operation, and the adjustable setting operation is to individually set the auxiliary on-time according to the voltage of the external input power supply and the load level. The zero-voltage switching power control system as claimed in claim 3, wherein the voltage of the external input power includes 90, 115 and 230Vac, and the load level includes a very light load, a light load, a medium load and a full load, And the auxiliary conduction time is generated by an adjustable setting operation, and the adjustable setting operation is to set the auxiliary conduction time as an initial conduction time when the voltage of the external input power supply is 90Vac, and set the auxiliary conduction time to the external input When the voltage of the power supply is 115 or 230Vac, the initial on-time is used to set the corresponding auxiliary on-time in a proportional amplification manner according to the voltage of the external input power. The zero-voltage switching power control system as claimed in claim 1, wherein the auxiliary on-time is generated by an adaptive modulation operation, and the adaptive modulation operation comprises: judging whether the auxiliary winding voltage is lower than a threshold voltage value, and when the auxiliary winding voltage is not lower than the threshold voltage value, change and set the auxiliary on-time in a cycle-by-cycle manner until the auxiliary winding voltage is lower than the threshold voltage value limit voltage value. The zero-voltage switching power supply control system as claimed in claim 1, wherein the auxiliary on-time is generated by a calculation operation, and the calculation operation includes: calculating and setting the auxiliary on-time according to a calculation formula below, the The auxiliary on-time is expressed as

,

, V _b is the rectified power supply, V _or is a maximum amplitude voltage of the drain voltage of the primary side switching unit at the under-damped resonance, and _Tr is the period of the under-damped resonance. The zero-voltage switching power supply control system as claimed in claim 1, wherein the auxiliary on-time is generated by a calculation operation, and the calculation operation includes: calculating and setting the auxiliary on-time according to a calculation formula below, the Auxiliary conduction time=(the voltage of the external input power supply x P1)+P2, and P1 is a first parameter, P2 is a second parameter, the first parameter is between 0.98~0.99ns, and the second parameter is 31.1 Between ~31.9ns.

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