CN1909354B

CN1909354B - starting circuit of power converter

Info

Publication number: CN1909354B
Application number: CN2006101097194A
Authority: CN
Inventors: 杨大勇; 黄志丰
Original assignee: System General Corp Taiwan
Current assignee: Fairchild Taiwan Corp
Priority date: 2006-08-07
Filing date: 2006-08-07
Publication date: 2010-11-10
Anticipated expiration: 2026-08-07
Also published as: CN1909354A

Abstract

The invention relates to a starting circuit of a power converter, which comprises a first transistor, an impedance device, a second transistor, a third transistor and a diode. The first transistor is coupled to a voltage source. The third transistor is connected in series with the first transistor to output a supply voltage to a control circuit of the power converter according to the voltage source. The diode is coupled to a transformer winding of the power converter and the control circuit to supply another supply voltage to the control circuit. The second transistor controls the first transistor and the third transistor according to a control signal. The impedance device is coupled with the first transistor and the third transistor. When the second transistor is turned off, the impedance device provides a bias voltage to enable the first transistor and the third transistor to be turned on; when the second transistor is turned on, the third transistor is turned off, and the first transistor is in a negative bias state.

Description

Start-up circuit of power converter

技术领域technical field

本发明是有关于一种启动电路，特别是指一种功率转换器的高压启动电路。The invention relates to a starting circuit, in particular to a high-voltage starting circuit of a power converter.

背景技术Background technique

请参阅图1，其为习用功率转换器的启动电路的电路图。如图所示，习用启动电路用于控制一电压源V_IN的导通与截止，进而提供一电压V_D作为一功率转换器的一控制电路10的供应电压。当功率转换器启动时，电压源V_IN即经由一电晶体11而供应电压V_D。电晶体11，其一汲极与一源极分别耦接电压源V_IN与控制电路10。当控制电路10开始运作时，功率转换器的一变压器绕组16会经由一二极体17与一电容18提供另一个供应电压至控制电路10。之后，电晶体11将会受一电晶体12驱动而截止，以节省电源消耗。变压器绕组16，其耦接于一接地端与二极体17的一端。电容18则耦接于二极体17的另一端与接地端之间，电容18更耦接于控制电路10。一电阻15，其耦接于电晶体11的汲极与电晶体11的一闸极之间。电阻15用于提供一偏压以导通电晶体11。Please refer to FIG. 1 , which is a circuit diagram of a start-up circuit of a conventional power converter. As shown in the figure, the conventional start-up circuit is used to control the on and off of a voltage source V _IN , and then provide a voltage V _D as a supply voltage of a control circuit 10 of a power converter. When the power converter starts up, the voltage source V _IN supplies the voltage V _D through a transistor 11 . A drain and a source of the transistor 11 are respectively coupled to the voltage source V _IN and the control circuit 10 . When the control circuit 10 starts to operate, a transformer winding 16 of the power converter provides another supply voltage to the control circuit 10 through a diode 17 and a capacitor 18 . Afterwards, the transistor 11 is driven by a transistor 12 to turn off, so as to save power consumption. The transformer winding 16 is coupled to a ground terminal and one end of the diode 17 . The capacitor 18 is coupled between the other end of the diode 17 and the ground, and the capacitor 18 is further coupled to the control circuit 10 . A resistor 15 is coupled between the drain of the transistor 11 and a gate of the transistor 11 . The resistor 15 is used to provide a bias voltage to turn on the transistor 11 .

电晶体12，其一汲极与一源极分别耦接电晶体11的闸极以及接地端。此外电晶体12的一闸极是耦接一反相器14的一输出端，反相器14的一输入端则接收一控制讯号S_N，如此控制讯号S_N可透过反相器14控制电晶体12。电晶体12会在控制讯号S_N于禁能状态时导通，进而使电晶体11截止。然而，当电晶体12导通时，电阻15将会消耗一功率P_R，其可表示为如下：A drain and a source of the transistor 12 are respectively coupled to the gate and the ground of the transistor 11 . In addition, a gate of the transistor 12 is coupled to an output terminal of an inverter 14, and an input terminal of the inverter 14 receives a control signal _SN , so that the control signal _SN can be controlled by the inverter 14. Transistor 12. The transistor 12 is turned on when the control signal _SN is in a disabled state, thereby turning off the transistor 11 . However, when the transistor 12 is turned on, the resistor 15 will consume a power P _R , which can be expressed as follows:

${P P}_{R R} = = \frac{{V V}_{IN IN}^{22}}{{R R}_{1515}} - - - - - - ((11))$

其中，R₁₅为电阻15的电阻值。Wherein, R ₁₅ is the resistance value of the resistor 15 .

一般而言，电压源V_IN通常是由一交流电源供应，当一很高的线电压(High Line Voltage)耦接至电压源V_IN并经过整流后，电压源V_IN的电压可能高达直流电压350伏特。如此由方程式(1)可得知，电阻15将产生一显著的功率损耗。依据上述方程式(1)可得知，若电阻15的电阻值越高即可降低功率损耗，所以采用高电阻值的电阻15，例如几百万欧姆，可有效降低功率损耗。然而，高电阻值的电阻15不适合整合于积体电路(integratedcircuit)中。Generally speaking, the voltage source V _IN is usually supplied by an AC power source. When a high line voltage (High Line Voltage) is coupled to the voltage source V _IN and rectified, the voltage of the voltage source V _IN may be as high as DC voltage 350 volts. It can be known from equation (1) that the resistor 15 will generate a significant power loss. According to the above equation (1), it can be known that the higher the resistance of the resistor 15 can reduce the power loss, so the use of a high resistance resistor 15, such as several million ohms, can effectively reduce the power loss. However, the high-resistance resistor 15 is not suitable for integration in an integrated circuit.

因此，本发明即针对上述问题而提供一种高效率的启动电路，其可降低功率损耗，并可整合于积体电路，以有效解决上述问题。Therefore, the present invention provides a high-efficiency start-up circuit for the above-mentioned problems, which can reduce power consumption and can be integrated into an integrated circuit to effectively solve the above-mentioned problems.

发明内容Contents of the invention

本发明的主要目的，在于提供一种功率转换器的启动电路，其可降低功率损耗。The main purpose of the present invention is to provide a start-up circuit of a power converter, which can reduce power loss.

本发明功率转换器的启动电路，其包含有一第一电晶体、一阻抗装置、一第二电晶体、一第三电晶体与一二极体。第一电晶体具有一负临界电压，而第二电晶体与第三电晶体为正临界电压装置。第一电晶体耦接一电压源。第三电晶体串联于第一电晶体，而提供一供应电压至功率转换器的一控制电路。二极体耦接于功率转换器的一变压器绕组与控制电路，而提供另一供应电压至控制电路。第二电晶体依据一控制讯号控制第一电晶体与第三电晶体。阻抗装置耦接第一电晶体与第三电晶体，并在第二电晶体截止时，提供一偏压至第一电晶体与第三电晶体，以使第一电晶体与第三电晶体导通。一旦第二电晶体导通时，第三电晶体将截止，且第一电晶体为负偏压状态。The starting circuit of the power converter of the present invention includes a first transistor, an impedance device, a second transistor, a third transistor and a diode. The first transistor has a negative threshold voltage, and the second transistor and the third transistor are positive threshold voltage devices. The first transistor is coupled to a voltage source. The third transistor is connected in series with the first transistor to provide a supply voltage to a control circuit of the power converter. The diode is coupled to a transformer winding of the power converter and the control circuit, and provides another supply voltage to the control circuit. The second transistor controls the first transistor and the third transistor according to a control signal. The impedance device is coupled to the first transistor and the third transistor, and provides a bias voltage to the first transistor and the third transistor when the second transistor is cut off, so that the first transistor and the third transistor conduct Pass. Once the second transistor is turned on, the third transistor is turned off, and the first transistor is in a negative bias state.

根据本发明，可以降低功率损耗。According to the present invention, power loss can be reduced.

附图说明Description of drawings

图1为习用功率转换器的启动电路的电路图；FIG. 1 is a circuit diagram of a start-up circuit of a conventional power converter;

图2为本发明功率转换器的启动电路的一较佳实施例的电路图；Fig. 2 is the circuit diagram of a preferred embodiment of the starting circuit of the power converter of the present invention;

图3为本发明具有负临界电压的电晶体的电压对电流的曲线图；Fig. 3 is the graph that the present invention has the voltage of the transistor of negative threshold voltage to electric current;

图4为本发明的启动电路导通时电流流向的电路示意图；Fig. 4 is the circuit schematic diagram of the current flow direction when the starting circuit of the present invention is turned on;

图5为本发明的启动电路截止时电流流向的电路示意图；Fig. 5 is the circuit schematic diagram of the current flow direction when the starting circuit of the present invention is cut off;

图6为本发明功率转换器的启动电路的另一较佳实施例的电路图。FIG. 6 is a circuit diagram of another preferred embodiment of the start-up circuit of the power converter of the present invention.

图号说明：Description of figure number:

10 控制电路 11 电晶体10 Control circuit 11 Transistor

12 电晶体 14 反相器12 Transistor 14 Inverter

15 电阻 16 变压器绕组15 Resistor 16 Transformer winding

17 二极体 18 电容17 Diode 18 Capacitor

20 第一电晶体 25 第三电晶体20 first transistor 25 third transistor

30 阻抗装置 40 反相器30 Impedance device 40 Inverter

50 第二电晶体 60 电阻50 second transistor 60 resistor

70 电容 90 二极体70 capacitor 90 diode

100 变压器绕组 I_J 电流100 Transformer winding I _J current

V_D 电压 V_IN 电压源V _D voltage V _IN voltage source

V_J 电压 S_N 控制讯号V _J voltage S _N control signal

具体实施方式Detailed ways

请参阅图2，其为本发明启动电路的一较佳实施例的电路图。如图所示，本发明的启动电路包含有一第一电晶体20、一第二电晶体50、一第三电晶体25、一阻抗装置30与一二极体90。第一电晶体20具有一负临界电压，所以第一电晶体为一负临界电压装置。第二电晶体50与第三电晶体25为正临界电压装置。第一电晶体20具有一第一端、一第二端与一第三端，第一电晶体20的第一端耦接于一电压源V_IN。第三电晶体25，其串联于第一电晶体20，而依据电压源V_IN输出一电压V_D，以提供一供应电压至功率转换器的控制电路10。第三电晶体25的一汲极连接于第一电晶体20的第二端，而第三电晶体25的一源极则耦接于控制电路10。Please refer to FIG. 2 , which is a circuit diagram of a preferred embodiment of the startup circuit of the present invention. As shown in the figure, the startup circuit of the present invention includes a first transistor 20 , a second transistor 50 , a third transistor 25 , an impedance device 30 and a diode 90 . The first transistor 20 has a negative threshold voltage, so the first transistor is a negative threshold voltage device. The second transistor 50 and the third transistor 25 are positive threshold voltage devices. The first transistor 20 has a first terminal, a second terminal and a third terminal, and the first terminal of the first transistor 20 is coupled to a voltage source V _IN . The third transistor 25 is connected in series with the first transistor 20 and outputs a voltage V _D according to the voltage source V _IN to provide a supply voltage to the control circuit 10 of the power converter. A drain of the third transistor 25 is connected to the second end of the first transistor 20 , and a source of the third transistor 25 is coupled to the control circuit 10 .

本发明为了导通第一电晶体20与第三电晶体25，是将阻抗装置30耦接于第一电晶体20的第二端与第三端之间。另外，阻抗装置30更耦接于第三电晶体25的汲极与第三电晶体25的一闸极之间。所以阻抗装置30会提供一偏压至第一电晶体20与第三电晶体25。其中，阻抗装置30可为一电阻或者一电晶体。一电容70，其一端耦接于控制电路10，电容70的另一端则耦接于接地端。一二极体90，其一端耦接于电容70与控制电路10，二极体90的另一端则耦接于功率转换器的一变压器绕组100。当控制电路10开始运作时，变压器绕组100将经由二极体90与电容70提供另一供应电压至控制电路10。之后，藉由第一电晶体20与第三电晶体25截止电压源V_IN传输电源，以节省电源消耗。复参考图2，一控制讯号S_N传输至启动电路的一输入端，以导通第二电晶体50，进而截止电压源V_IN。第二电晶体50，其一闸极经由一反相器40接收控制讯号S_N。其中，反相器40的一输入端接收控制讯号S_N，而反相器40的一输出端则耦接于第二电晶体50的闸极。第二电晶体50的一源极耦接于接地端，第二电晶体50的一汲极耦接于第三电晶体25的闸极与第一电晶体20的第三端。所以，当第二电晶体50依据控制讯号S_N的致能状态而截止时，阻抗装置30会提供偏压至第三电晶体25与第一电晶体20，该偏压可以导通第三电晶体25与第一电晶体20。In order to conduct the first transistor 20 and the third transistor 25 in the present invention, the impedance device 30 is coupled between the second terminal and the third terminal of the first transistor 20 . In addition, the impedance device 30 is further coupled between the drain of the third transistor 25 and a gate of the third transistor 25 . Therefore, the impedance device 30 provides a bias voltage to the first transistor 20 and the third transistor 25 . Wherein, the impedance device 30 can be a resistor or a transistor. One end of a capacitor 70 is coupled to the control circuit 10 , and the other end of the capacitor 70 is coupled to the ground. One end of a diode 90 is coupled to the capacitor 70 and the control circuit 10 , and the other end of the diode 90 is coupled to a transformer winding 100 of the power converter. When the control circuit 10 starts to operate, the transformer winding 100 provides another supply voltage to the control circuit 10 through the diode 90 and the capacitor 70 . Afterwards, the first transistor 20 and the third transistor 25 cut off the voltage source V _IN to transmit power, so as to save power consumption. Referring again to FIG. 2 , a control signal _SN is transmitted to an input terminal of the start-up circuit to turn on the second transistor 50 to turn off the voltage source V _IN . A gate of the second transistor 50 receives the control signal _SN through an inverter 40 . Wherein, an input end of the inverter 40 receives the control signal _SN , and an output end of the inverter 40 is coupled to the gate of the second transistor 50 . A source of the second transistor 50 is coupled to the ground terminal, and a drain of the second transistor 50 is coupled to the gate of the third transistor 25 and the third terminal of the first transistor 20 . Therefore, when the second transistor 50 is turned off according to the enable state of the control signal _SN , the impedance device 30 will provide a bias voltage to the third transistor 25 and the first transistor 20, and the bias voltage can conduct the third transistor 25. The crystal 25 and the first transistor 20.

一旦，功率转换器中控制电路10开始运作之后，而第二电晶体50依据控制讯号S_N的禁能状态导通时，第三电晶体25将会截止，以截止电压源V_IN，进而停止输出供应电压至控制电路10。同时，阻抗装置30将提供一负偏压至第一电晶体20。也就是第二电晶体50将经由阻抗装置30提供负偏压至第一电晶体20，如此即可控制第一电晶体20截止。其中，第一电晶体20具有一负临界电压-V_TH，如图3所示。Once the control circuit 10 in the power converter starts to operate and the second transistor 50 is turned on according to the disabled state of the control signal _SN , the third transistor 25 will be turned off to cut off the voltage source V _IN , thereby stopping Output the supply voltage to the control circuit 10 . At the same time, the impedance device 30 will provide a negative bias voltage to the first transistor 20 . That is, the second transistor 50 provides a negative bias voltage to the first transistor 20 through the impedance device 30 , so that the first transistor 20 can be controlled to be cut off. Wherein, the first transistor 20 has a negative threshold voltage -V _TH , as shown in FIG. 3 .

请参阅图3，其为本发明的第一电晶体20的电压对电流的曲线图。图示中的电流I_J为通过第一电晶体20的第一端与第二端的电流。电压V_J为第一电晶体20的第三端与第二端之间的电压。于本发明中，第一电晶体20为一电压控制阻抗装置。如图3所示，电压V_J降低时，电流I_J亦会随着降低，而当电压V_J低于第一电晶体20的负临界电压-V_TH时，第一电晶体20将会截止。Please refer to FIG. 3 , which is a graph of voltage versus current of the first transistor 20 of the present invention. The current I _J in the figure is the current passing through the first terminal and the second terminal of the first transistor 20 . The voltage V _J is the voltage between the third terminal and the second terminal of the first transistor 20 . In the present invention, the first transistor 20 is a voltage controlled impedance device. As shown in Figure 3, when the voltage V _J decreases, the current I _J will also decrease, and when the voltage V _J is lower than the negative threshold voltage -V _TH of the first transistor 20, the first transistor 20 will be cut off .

请参阅图4与图5，其分别显示本发明的启动电路于导通和截止时，电流I_J流动的方向。图示中的电阻60为图2的阻抗装置30的实施态样。于图4中，控制讯号S_N为致能状态，第二电晶体50则依据控制讯号S_N的致能状态而截止，故没有电流通过电阻60，所以电阻60提供一零偏压至第一电晶体20的电压V_J。此外电阻60亦提供一相同偏压于第三电晶体25的闸极与汲极之间，因此，第一电晶体20与第三电晶体25两者皆会导通。Please refer to FIG. 4 and FIG. 5 , which respectively show the flow direction of the current I _J when the start-up circuit of the present invention is turned on and turned off. The resistor 60 in the illustration is an implementation of the impedance device 30 in FIG. 2 . In FIG. 4, the control signal _SN is in the enable state, and the second transistor 50 is turned off according to the enable state of the control signal _SN , so no current flows through the resistor 60, so the resistor 60 provides a zero bias voltage to the first The voltage V _J of transistor 20 . In addition, the resistor 60 also provides a same bias voltage between the gate and the drain of the third transistor 25, so both the first transistor 20 and the third transistor 25 are turned on.

于图5中，控制讯号S_N为禁能状态，第二电晶体50则依据控制讯号S_N的禁能状态而导通，第三电晶体25因其闸极为低电压准位而截止。同一时间，电流I_J是流过第二电晶体50与电阻60。此时电阻60提供负偏压至第一电晶体20的电压V_J。在此瞬间，电流I_J的增加会进一步使得提供至第一电晶体20的电压V_J的负偏压增大。当负偏压达到负临界电压-V_TH时，第一电晶体20将截止以避免电流I_J增加。In FIG. 5 , the control signal _SN is in a disabled state, the second transistor 50 is turned on according to the disabled state of the control signal _SN , and the third transistor 25 is turned off because its gate is at a low voltage level. At the same time, the current _IJ flows through the second transistor 50 and the resistor 60 . At this time, the resistor 60 provides a negative bias voltage to the voltage V _J of the first transistor 20 . At this moment, the increase of the current I _J will further increase the negative bias of the voltage V _J provided to the first transistor 20 . When the negative bias voltage reaches the negative threshold voltage -V _TH , the first transistor 20 will be turned off to prevent the current I _J from increasing.

本发明的启动电路是以负回授方式操作。虽然当第三电晶体25截止时，仍然有一电流通过第一电晶体20，但是此电流的电流值非常小，所以其造成的功率消耗可以忽略。由于第一电晶体20与阻抗装置30可整合至积体电路中，所以本发明的图2所示启动电路可达到本发明的目的而整合于积体电路中。The start-up circuit of the present invention operates in a negative feedback mode. Although there is still a current flowing through the first transistor 20 when the third transistor 25 is turned off, but the current value is very small, so the power consumption caused by it can be ignored. Since the first transistor 20 and the impedance device 30 can be integrated into an integrated circuit, the start-up circuit shown in FIG. 2 of the present invention can achieve the purpose of the present invention and be integrated into an integrated circuit.

请参阅图6，其为本发明功率转换器的启动电路的另一较佳实施例的电路图。如图所示，此实施例不包括有图2的实施例所示的第三电晶体25。此实施例的第一电晶体20耦接于电压源V_IN，以接收电压源V_IN而提供一供应电压至功率转换器的控制电路10。此实施例不具有第三电晶体25，所以当第二电晶体50导通时，一电流将经由阻抗装置30从电容70流至第二电晶体50。虽然，阻抗装置30将提供负偏压以截止第一电晶体20，由于从电容70输出的电流会导致功率损耗。所以，图6的阻抗装置30必须具有高电阻值，以减少功率损耗。Please refer to FIG. 6 , which is a circuit diagram of another preferred embodiment of the startup circuit of the power converter of the present invention. As shown, this embodiment does not include the third transistor 25 shown in the embodiment of FIG. 2 . In this embodiment, the first transistor 20 is coupled to the voltage source V _IN to receive the voltage source V _IN and provide a supply voltage to the control circuit 10 of the power converter. This embodiment does not have the third transistor 25 , so when the second transistor 50 is turned on, a current will flow from the capacitor 70 to the second transistor 50 through the impedance device 30 . Although the impedance device 30 will provide a negative bias to turn off the first transistor 20 , power loss will result due to the current output from the capacitor 70 . Therefore, the impedance device 30 of FIG. 6 must have a high resistance value to reduce power loss.

以上所述，仅为本发明一较佳实施例而已，并非用来限定本发明实施的范围，凡依本发明权利要求范围所述的形状、构造、特征及精神所为的均等变化与修饰，均应包括于本发明的权利范围内。The above description is only a preferred embodiment of the present invention, and is not intended to limit the scope of the present invention. All equivalent changes and modifications made in accordance with the shape, structure, characteristics and spirit described in the scope of the claims of the present invention, All should be included in the scope of rights of the present invention.

Claims

1. the start-up circuit of a power converter is characterized in that, it includes:

One the first transistor, it has one first end, one second end and one the 3rd end, and this first end couples a voltage source;

One the 3rd transistor, it has a drain electrode, one source pole and a grid, the 3rd transistorized should the drain electrode connects this second end of this first transistor, the 3rd transistorized this source electrode is coupled to a control circuit of this power converter, and the 3rd transistor provides a supply voltage to this control circuit;

One diode, it is coupled to a Transformer Winding and this control circuit of this power converter, to provide another supply voltage to this control circuit;

One transistor seconds, it has a drain electrode, one source pole and a grid, this drain electrode of this transistor seconds couples the 3rd end of the 3rd transistorized this grid and this first transistor, this source electrode of this transistor seconds is coupled to an earth terminal, this grid of this transistor seconds receives a controlling signal, this controlling signal is used for this transistor seconds of conducting, to end the 3rd transistor;

One impedance means, it is coupled between the 3rd end and this second end of this first transistor;

Wherein, when this transistor seconds ended, this impedance means provided a bias voltage, with this first transistor of conducting the 3rd transistor AND gate;

This first transistor has a negative critical voltage, and when this bias voltage reaches this negative critical voltage, this first transistor ends;

During this transistor seconds conducting, this impedance means provides a back bias voltage to this first transistor;

After this control circuit comes into operation, this transistor seconds conducting.

2. start-up circuit as claimed in claim 1 is characterized in that, this transistor seconds and the 3rd transistor are positive critical voltage device.

3. start-up circuit as claimed in claim 1 is characterized in that, this first transistor is a voltage control impedance means, when the 3rd transistor ends, an electric current is still arranged by this first transistor.

4. start-up circuit as claimed in claim 1 is characterized in that, this impedance means can be a resistance or a transistor.

5. the start-up circuit of a power converter is characterized in that, it includes:

One the 3rd transistor, it has a drain electrode, one source pole and a grid, and the 3rd transistorized should the drain electrode connects this second end of this first transistor, so that the control circuit of a supply voltage to this power converter to be provided according to this voltage source;

One impedance means, it couples between the 3rd end and this second end of this first transistor, and couples the 3rd transistorized this drain electrode, in order to a bias voltage to be provided, with this first transistor of conducting and the 3rd transistor;

One transistor seconds, it couples the 3rd transistor, in order to end the 3rd transistor;

Wherein, this transistor seconds is controlled by a controlling signal;

This start-up circuit more includes a diode, and this diode is coupled to a Transformer Winding and this control circuit of this power converter, to provide another supply voltage to this control circuit;

During this transistor seconds conducting, provide a back bias voltage to this first transistor via this impedance means.

6. start-up circuit as claimed in claim 5 is characterized in that, this transistor seconds and the 3rd transistor are positive critical voltage device.

7. start-up circuit as claimed in claim 5 is characterized in that, this first transistor is a voltage control impedance means, when the 3rd transistor ends, an electric current is still arranged by this first transistor.

8. start-up circuit as claimed in claim 5 is characterized in that, this impedance means can be a resistance or a transistor.

9. the start-up circuit of a power converter is characterized in that, it includes:

One the first transistor, this first transistor have first end, second end and the 3rd end, and this first end couples a voltage source, so that the control circuit of a supply voltage to this power converter to be provided;

One impedance means, it couples this first transistor and this supply voltage, in order to a bias voltage to be provided, with this first transistor of conducting;

One transistor seconds, it couples this first transistor and this impedance means, in order to end this first transistor;

Wherein, this transistor seconds is controlled by a controlling signal;

After this control circuit comes into operation, this transistor seconds conducting;

During this transistor seconds conducting, provide a back bias voltage to this first transistor, to end this first transistor via this impedance means.

10. the start-up circuit of a power converter is characterized in that, it includes:

One the first transistor, this first transistor have first end, second end and the 3rd end, and this first end couples a voltage source, so that a control circuit of supply voltage to one power converter to be provided;

Wherein, this transistor seconds is controlled by a controlling signal;

Wherein, this first transistor has a negative critical voltage, and when this bias voltage reaches this negative critical voltage, this first transistor ends;