阅读说明：本技术 一种集成启动功能的晶体管模块及其半导体模块和电压变换电路 (Transistor module integrated with starting function, semiconductor module and voltage conversion circuit thereof ) 是由 张波 于 2019-10-08 设计创作，主要内容包括：本发明公开了一种晶体管模块。晶体管模块包括作为功率开关的第一晶体管和作为启动电路的第二晶体管,第二晶体管用于为控制电路提供启动电流,其中第一晶体管的第一端耦接第二晶体管的第一端,第一晶体管的第二端耦接第二晶体管的控制端,第二晶体管的第二端用于提供启动电流。该方案将启动电路完全和功率开关集成,启动电路无需采用外部电阻和内置集成电阻,集成度高。因避免了耐高压大电阻的集成,降低了集成电阻带来的损耗,控制简单。(The invention discloses a transistor module. The transistor module comprises a first transistor serving as a power switch and a second transistor serving as a starting circuit, wherein the second transistor is used for providing starting current for the control circuit, the first end of the first transistor is coupled with the first end of the second transistor, the second end of the first transistor is coupled with the control end of the second transistor, and the second end of the second transistor is used for providing starting current. The starting circuit is completely integrated with the power switch, the starting circuit does not need to adopt an external resistor and a built-in integrated resistor, and the integration level is high. The integration of high-voltage-resistant large resistors is avoided, so that the loss caused by the integrated resistors is reduced, and the control is simple.)

1. A transistor module, comprising:

A first transistor having a first terminal, a second terminal, and a control terminal; and

The second transistor is used for providing starting current for the control circuit and is provided with a first end, a second end and a control end, wherein the first end of the first transistor is coupled with the first end of the second transistor, the second end of the first transistor is coupled with the control end of the second transistor, and the second end of the second transistor is used for providing starting current.

2. The transistor module of claim 1, wherein when the system is started up, the first transistor is in an off state and the second transistor is in an on state; when the first transistor operates normally, the second transistor is turned off.

3. The transistor module of claim 1, wherein the first transistor forms all or a portion of a power switch of the switching circuit.

4. The transistor module of claim 1, fabricated on a same semiconductor substrate to form a semiconductor die having four ports, wherein a first port is coupled to a first terminal of the first transistor and a first terminal of the second transistor, a second port is coupled to a second terminal of the first transistor and a control terminal of the second transistor, a third port is coupled to the control terminal of the first transistor, and a fourth port is coupled to the second terminal of the second transistor.

5. The transistor module of claim 4, wherein the fourth port is coupled to the first terminal of the control circuit, and the second transistor is in a conducting state when an input impedance of the first terminal of the control circuit is less than a first resistance value; when the input impedance of the first end of the control circuit is larger than the second resistance value, the second transistor is turned off, wherein the first resistance value is smaller than the second resistance value.

6. The transistor module of claim 1, wherein the first transistor comprises an enhancement mode MOSFET transistor, the second transistor comprises a depletion mode MOSFET transistor, a drain of the first transistor is coupled to a drain of the second transistor, a gate of the second transistor is coupled to a source of the first transistor, the second transistor channel is present when a value of a source voltage of the second transistor minus a gate voltage of the second transistor is less than a first threshold, the second transistor channel is pinched off when a value of the source voltage of the second transistor minus the gate voltage of the second transistor is greater than a second threshold, and wherein the first threshold is less than the second threshold.

7. a power transistor module with integrated start-up function, having a drain terminal, a source terminal, a start-up terminal and a control terminal, wherein the start-up terminal is coupled to a first terminal of a control circuit, and the control terminal is coupled to a second terminal of the control circuit, wherein:

In a starting stage, current flows into a drain end in a first current mode, the first current flows to a first end of the control circuit from the starting end to provide starting current for the control circuit, and the voltage of the control end is smaller than a third threshold value; and

In the working stage, the starting terminal has no current, and the control terminal voltage is at least partially greater than a fourth threshold value, wherein the third threshold value is less than the fourth threshold value.

8. The power transistor module of claim 7 having and only having a drain terminal, a source terminal, a start-up terminal and a control terminal.

9. The power transistor module of claim 7 further having a sense terminal, wherein the sense terminal is coupled to the third terminal of the control circuit, wherein during the active phase, the sense terminal voltage signal is proportional to the current signal flowing from the source terminal, and wherein the power transistor module has and only has a drain terminal, a source terminal, a enable terminal, a control terminal, and a sense terminal.

10. A semiconductor module including a start-up circuit and a power transistor, the semiconductor module having:

the first port is used for being coupled with a voltage upper end of the power transistor;

The second port is used for being coupled with the voltage lower end of the power transistor;

a third port for coupling to a control terminal of the power transistor; and

And the fourth port is externally coupled to the first end of the control circuit, when the voltage difference between the fourth port and the second port is smaller than a first threshold value, the impedance between the first port and the fourth port is smaller than a third resistance value, and when the voltage difference between the fourth port and the second port is larger than a second threshold value, the impedance between the first port and the fourth port is larger than a fourth resistance value, wherein the first threshold value is smaller than the second threshold value, and the third resistance value is smaller than the fourth resistance value.

11. A semiconductor module, comprising:

The starting circuit is used for providing starting current for the control circuit and comprises a depletion type field effect transistor, and one end of the depletion type field effect transistor is used for providing the starting current; and

And the conduction state of the power switch tube is controlled by the control circuit, the power switch tube comprises an enhancement type field effect tube, and the grid electrode of the depletion type field effect tube is coupled with the source electrode of the enhancement type field effect tube.

12. A voltage conversion circuit comprising a transistor module according to any one of claims 1 to 9 or a semiconductor module according to any one of claims 10 to 11 and a control circuit having a first terminal coupled to the transistor module or the semiconductor module for receiving a start-up current and a second terminal for controlling a power transistor or a power switch.

13. The voltage conversion circuit of claim 12, further comprising:

The primary winding is coupled with the transistor module or the semiconductor module;

The secondary winding is coupled with the secondary rectifying tube and used for providing output voltage;

an auxiliary winding; and

A capacitor coupled to the auxiliary winding and the third terminal of the control circuit, wherein when activated, the transistor module or the semiconductor module provides a start-up current to the first terminal of the control circuit for charging the capacitor; when the circuit works normally, the capacitor is powered by the auxiliary winding, wherein the first resistance value is smaller than the second resistance value.

Technical Field

the present invention relates to the field of electronics, and more particularly, but not exclusively, to a power transistor module integrated with a start function, a semiconductor module thereof, and a voltage conversion circuit.

Background

The starting circuit is used for providing power for the control circuit before the control circuit provides the control pulse signal for the switch circuit. A common starting circuit usually adopts a resistor, and an input voltage source generates current through the resistor to supply power to a control circuit. Fig. 1 shows a typical starting circuit in the prior art, which includes a starting resistor Rs, when the switching circuit starts to operate, the input power forms a charging current through the starting resistor Rs to charge a capacitor Cdd, and the control circuit (shown as an IC) is supplied with power to start the system to operate. When the switching circuit is working normally, the control circuit is powered by the power supply circuit, for example, by the voltage generated on the auxiliary winding Na in the figure.

However, the resistor of the starting circuit continuously consumes a large amount of electric energy, resulting in a large loss. In addition, since the resistance value of the resistor is generally large in consideration of the loss of the starting resistor, the starting current is small, thereby resulting in a long starting time of the system.

Meanwhile, a high-resistance resistor which can bear high voltage is not easy to integrate, the volume of a system can be increased by adopting an external resistor, the difficulty of the process can be increased by adopting an integrated resistor, and the area and the cost of a semiconductor chip can be increased.

disclosure of Invention

In order to solve at least part of the problems, the invention provides a power transistor module integrated with a starting function, a semiconductor module and a voltage conversion circuit thereof.

According to a first aspect of the invention, a transistor module comprises: a first transistor having a first terminal, a second terminal, and a control terminal; and a second transistor for providing a start-up current for the control circuit, the second transistor having a first terminal, a second terminal and a control terminal, wherein the first terminal of the first transistor is coupled to the first terminal of the second transistor, the second terminal of the first transistor is coupled to the control terminal of the second transistor, and the second terminal of the second transistor is used for providing a start-up current voltage.

In one embodiment, when the system is started, the first transistor is in an off state, and the second transistor is in an on state; when the first transistor operates normally, the second transistor is turned off.

In one embodiment, the first transistor forms all or a portion of a power switch of the switching circuit.

In one embodiment, the transistor module is fabricated on the same semiconductor substrate to form a semiconductor wafer having four ports, wherein the first port is coupled to the first terminal of the first transistor and the first terminal of the second transistor, the second port is coupled to the second terminal of the first transistor and the control terminal of the second transistor, the third port is coupled to the control terminal of the first transistor, and the fourth port is coupled to the second terminal of the second transistor.

In one embodiment, the fourth port is coupled to the first terminal of the control circuit, and when a voltage difference between the fourth port and the second port is smaller than a first threshold value and an input impedance of the first terminal of the control circuit is smaller than a first resistance value, the second transistor is in a conducting state; when the voltage difference between the fourth port and the second port is greater than a second threshold value, and the input impedance of the first end of the control circuit is greater than a second resistance value, the second transistor is turned off, wherein the first threshold value is less than the second threshold value, and the first resistance value is less than the second resistance value.

in one embodiment, the first transistor comprises an enhancement MOSFET, the second transistor comprises a depletion MOSFET, a drain of the first transistor is coupled to a drain of the second transistor, a gate of the second transistor is coupled to a source of the first transistor, the second transistor channel is present when a source voltage of the second transistor minus a gate voltage of the second transistor is less than a first threshold, and the second transistor channel is pinched off when the source voltage of the second transistor minus the gate voltage of the second transistor is greater than a second threshold, wherein the first threshold is less than the second threshold.

According to a second aspect of the present invention, a power transistor module with integrated start-up function has a drain terminal, a source terminal, a start-up terminal and a control terminal, wherein the start-up terminal is configured to be coupled to a first terminal of a control circuit, and the control terminal is configured to be coupled to a second terminal of the control circuit, wherein: in a starting stage, current flows into a drain end in a first current mode, the first current flows to a first end of the control circuit from the starting end to provide starting current for the control circuit, and the voltage of the control end is smaller than a third threshold value; and in the working stage, the starting terminal has no current, and the control terminal voltage is at least partially greater than a fourth threshold value, wherein the third threshold value is less than the fourth threshold value.

In one embodiment, the power transistor module has, and only has, a drain terminal, a source terminal, a start-up terminal, and a control terminal.

in one embodiment, the power transistor module further has a detection terminal, wherein the detection terminal is coupled to the third terminal of the control circuit, the detection terminal voltage signal is proportional to the current signal flowing from the source terminal during the operation phase, and the power transistor module has and only has a drain terminal, a source terminal, a start terminal, a control terminal and a detection terminal.

According to a third aspect of the present invention, a semiconductor module includes a start-up circuit and a power transistor, the semiconductor module having: the first port is used for being coupled with a voltage upper end of the power transistor; the second port is used for being coupled with the voltage lower end of the power transistor; a third port for coupling to a control terminal of the power transistor; and the fourth port is externally coupled to the first end of the control circuit, when the voltage difference between the fourth port and the second port is smaller than a first threshold value, the impedance between the first port and the fourth port is smaller than a third resistance value, and when the voltage difference between the fourth port and the second port is larger than a second threshold value, the impedance between the first port and the fourth port is larger than a fourth resistance value, wherein the first threshold value is smaller than the second threshold value, and the third resistance value is smaller than the fourth resistance value. The input impedance of the first end of the control circuit is smaller than a first resistance value, when the voltage difference between the fourth port and the second port is larger than a second threshold value, the input impedance of the second end of the control circuit is larger than the second resistance value, wherein the first threshold value is smaller than the second threshold value, and the first resistance value is smaller than the second resistance value.

According to a fourth aspect of the present invention, a semiconductor module includes: the starting circuit is used for providing starting voltage starting current for the control circuit and comprises a depletion type field effect transistor, and one end of the depletion type field effect transistor is used for providing the starting voltage starting current; and the conduction state of the power switch tube is controlled by the control circuit, the power switch tube comprises an enhancement type field effect tube, and the grid control end of the depletion type field effect tube is coupled with the source electrode of the enhancement type field effect tube.

According to a fifth aspect of the present invention, a voltage converting circuit comprises a transistor module or a semiconductor module as described in any of the above embodiments, and a control circuit having a first terminal and a second terminal coupled to the transistor module or the semiconductor module, wherein the first terminal is configured to receive a start-up current, and the second terminal is configured to control a power transistor or a power switch.

In one embodiment, the voltage conversion circuit further comprises: the primary winding is coupled with the transistor module or the semiconductor module; the secondary winding is coupled with the secondary rectifying tube and used for providing output voltage; an auxiliary winding; and a capacitor coupled to the auxiliary winding and the third terminal of the control circuit, wherein when started, the transistor module or the semiconductor module provides a starting current to the first terminal of the control circuit for charging the capacitor; when the circuit works normally, the capacitor is powered by the auxiliary winding, wherein the first resistance value is smaller than the second resistance value.

In the transistor module, the semiconductor module and the voltage conversion circuit in the embodiment of the invention, the starting circuit and the power transistor are integrated on the same semiconductor substrate, and the integration of the starting function and the power switch can be realized only through four external ports. The starting circuit does not need to adopt an external resistor, has few external pins and high integration level, avoids the integration of a high-voltage-resistant large resistor with a complex built-in process, reduces the loss caused by the integrated resistor and is simple to control.

Drawings

Fig. 1 shows a typical start-up circuit in the prior art.

Fig. 2 shows a circuit schematic of a transistor module 10 according to an embodiment of the invention.

Fig. 3 shows a schematic diagram of a semiconductor module according to an embodiment of the invention.

Fig. 4 shows a circuit schematic of a transistor module 20 with a start-up function and a current sensing function according to an embodiment of the invention.

Fig. 5 shows a schematic diagram of a voltage conversion circuit according to an embodiment of the invention.

Detailed Description

preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.

For a further understanding of the invention, reference will now be made to the preferred embodiments of the invention by way of example, and it is to be understood that the description is intended to further illustrate features and advantages of the invention, and not to limit the scope of the claims.

The description in this section is for several exemplary embodiments only, and the present invention is not limited only to the scope of the embodiments described. It is within the scope of the present disclosure and protection that the same or similar prior art means and some features of the embodiments may be interchanged.

"coupled" or "connected" in this specification includes both direct and indirect connections, such as through an electrically conductive medium such as a metal, which may have parasitic parameters.

Fig. 2 shows a circuit schematic of a transistor module 10 according to an embodiment of the invention. The transistor module 10 integrates a start-up function, including a first transistor Q1 as a power transistor and a second transistor Q2 as a start-up circuit. The first transistor Q1 has a first terminal coupled to the port D, a second terminal coupled to the port S, and a control terminal coupled to the port G. The second transistor Q2 is used to provide a start-up current at port V for the control circuit 11. The second transistor Q2 has a first terminal coupled to the port D, a second terminal coupled to the port V, and a control terminal coupled to the port S. Specifically, a first terminal of the second transistor Q2 is coupled to a first terminal of the first transistor Q1, a control terminal of the second transistor Q2 is coupled to a second terminal of the first transistor Q1, and the second terminal of the second transistor Q2 is used for providing a start-up current.

Accordingly, the transistor module 10 has four ports, a first port D, a second port S, a third port G and a fourth port V. The first port D is coupled to the first terminal of the first transistor Q1 and the first terminal of the second transistor Q2, the second port S is coupled to the second terminal of the first transistor Q1 and the control terminal of the second transistor Q2, the third port G is coupled to the control terminal of the first transistor Q1, and the fourth port V is coupled to the second terminal of the second transistor Q2. In the illustrated embodiment, the first port D is a drain terminal, the second port S is a source terminal, the third port G is a control terminal, and the fourth port V is a start terminal.

In the preferred embodiment, the transistor module 10 is fabricated independently on a semiconductor substrate to form a power semiconductor die, wherein the four ports D, S, G, V are the four pins of the semiconductor die. In one embodiment, the semiconductor die 10 has, and only has, a drain pin D, a source pin S, a control pin G, and an enable pin V. In one embodiment, the semiconductor die 10 is packaged separately in a package. In another embodiment, the semiconductor die 10 and the control die 11 with the control circuit fabricated thereon are packaged in the same package by a multi-die packaging process.

in one embodiment, the transistor module 10 and other components are fabricated on a semiconductor substrate, and some of the four ports D, S, G, V may be located within a semiconductor die.

Externally, the fourth port V of the transistor module 10 is coupled to the first terminal CTR of the control circuit 11 for providing the start-up current for the control circuit 11, and the third port G of the transistor module 10 is coupled to the second terminal Gate of the control circuit 11 for receiving the control signal for controlling the first transistor Q1. In the start-up phase, the input impedance of the first terminal CTR of the control circuit 11 is low impedance, and at this time, the second transistor Q2 is in a conducting state, and a current flows from the first terminal D through the second transistor Q2 to the fourth terminal V as a start-up current for charging the capacitor C1 connected to the control circuit terminal VDD, so as to generate a start-up voltage, so that the control circuit generates a driving voltage for driving the first transistor Q1. When the first transistor Q1 operates normally, the input impedance of the first terminal CTR is high impedance, the second transistor Q2 is turned off, and the capacitor C1 of the control circuit 11 is powered by other external circuits.

in one embodiment, the first transistor Q1 is a power switch of the switching circuit, and in the initial stage of starting, the control circuit fails to provide an effective driving voltage, and the first transistor Q1 is in an off state; in normal operation, the first transistor Q1 operates in a switching state under the control of a switching control signal Gate output from the control circuit 11 for controlling the output voltage. Preferably, the switching control signal Gate is a Pulse Width Modulation (PWM) signal. Of course, the first transistor Q1 may also be used as a part of a power switch, which is connected in parallel with other transistors to form a power switch, as a part of a power conversion circuit, such as a Buck circuit (Buck), a Flyback voltage conversion circuit (Flyback) or a Boost circuit (Boost). The first transistor Q1 may also operate in the variable resistance region as a power transistor for a linear circuit.

preferably, the first transistor Q1 includes an enhancement transistor, and the second transistor Q2 includes a depletion transistor. When the system starts, the input impedance of the first terminal CTR of the control circuit 11 is low impedance and smaller than the first resistance value, the voltage of the start terminal V and the voltage of the source terminal S are both low levels, the voltage of the start terminal V is smaller than the first threshold value relative to the voltage of the source terminal S, the original channel of the second transistor Q2 exists, the transistor Q2 is in a conducting state, the impedance between the first port D and the fourth port V is low impedance and smaller than the third resistance value, and a current flows from the D to the source terminal of the transistor Q2 through the transistor Q2 to charge the capacitor C1 to provide the start current for the control circuit. At this time, the voltage at the control terminal G provided by the second terminal Gate of the control circuit 11 is at a low level, which is smaller than the third threshold, and the first transistor Q1 is in an off state. When the system starts to work normally, the second terminal Gate of the control circuit 11 outputs a driving signal to drive the power transistor Q1 to work normally, the voltage at the control terminal G is at a high level for at least a part of the time, which is greater than the fourth threshold value, if the transistor Q1 works in the on-off state, the voltage at the control terminal G appears at the high level intermittently, and if the transistor Q1 works in the linear state, the voltage at the control terminal G is at the high level for a longer time. At this time, other circuits provide a power supply voltage for the control circuit, for example, an auxiliary winding Na in the isolated voltage converter shown in fig. 2 is used to charge the capacitor C1 to provide a power supply voltage, at this time, the input impedance of the first terminal CTR of the control circuit is high impedance and larger than the second resistance value, the voltage of the start terminal V is raised, the voltage of the start terminal V is larger than the second threshold value relative to the voltage of the source terminal S, the channel of the second transistor Q2 is pinched off, the second transistor Q2 is turned off, and the impedance between the first port D and the fourth port V is high impedance and larger than the fourth resistance value. The first threshold is smaller than the second threshold, the first resistance is smaller than the second resistance, the third resistance is smaller than the fourth resistance, and the third threshold is smaller than the fourth threshold. The first threshold, the second threshold, the third threshold, the fourth threshold, the first resistance, the second resistance, the third resistance and the fourth resistance are parameter values arbitrarily selected in a reasonable range and used for qualitatively reflecting the characteristics in the embodiment.

Therefore, a built-in high-voltage-resistant integrated resistor with a complex process is not required to be introduced, an external resistor is not required to be additionally introduced to realize a starting function, the system does not generate current through the resistor during normal work, the power consumption is extremely low, the starting circuit is in a low-impedance conduction state during a starting stage, the starting current is high, and the starting speed is high.

Fig. 3 shows a schematic diagram of a semiconductor module according to an embodiment of the invention. The semiconductor module is a transistor module including a first transistor Q1 and a second transistor Q2. The first transistor Q1 is a power transistor, and its conducting state is controlled by the control circuit. The second transistor Q2 acts as a start-up circuit for providing a start-up current to the control circuit. The semiconductor module is provided with a first port D which is used for being coupled with a voltage upper end of the power transistor Q1; a second port S for coupling to the voltage low terminal of the power transistor Q1; a third port G for coupling to a control terminal of the power transistor Q1; and a fourth port V, externally coupled to the control circuit, for providing a starting current for the control circuit. In the illustrated embodiment, the power transistor includes an enhancement mode fet Q1, Q1 being turned off when the control terminal G voltage is low and Q1 being turned on when the control terminal G voltage is high. The second transistor Q2 includes a depletion mode fet Q2 having a control terminal coupled to the source of an enhancement mode fet Q1. In the embodiment shown in fig. 3, the first transistor Q1 is an enhancement mode Metal Oxide Semiconductor Field Effect Transistor (MOSFET) and the second transistor Q2 is a depletion mode MOSFET. The drain of the first transistor Q1 is coupled to the drain of the second transistor Q2 as the first port D of the semiconductor module, the gate of the second transistor Q2 is coupled to the source of the first transistor Q1 as the second port S of the semiconductor module, the gate of the first transistor Q1 as the third port G of the semiconductor module, and the source of the second transistor as the fourth port V of the semiconductor module. The channel of the N-type transistor Q2 is N-doped, so when the source (fourth port V) voltage of Q2 is less than a threshold value relative to the control (second port S) voltage, Q2 is in a conducting state due to the presence of the channel of transistor Q2, and current flows from the first port D to the fourth port V through the channel of transistor Q2. The N communication can allow a large current to pass through, and the large current can quickly charge the capacitor C1 to raise the starting voltage, so that the quick starting is realized. When the power supply circuit 12 shown in fig. 2 gradually operates normally, the source terminal (fourth port V) voltage of Q2 is raised by the CTR terminal. When the source terminal (V terminal) voltage of the Q2 is increased relative to the control terminal (S terminal)) voltage, the channel of the Q2 is narrowed until the channel is pinched off, the transistor Q2 is turned off, a high impedance is presented, the start-up circuit hardly generates power loss, and the power consumption is extremely low.

As can be seen from fig. 3, the transistor modules are fabricated on the same semiconductor substrate to form a semiconductor wafer, which has four ports, including a drain terminal D, a source terminal S, a control terminal G and a start-up terminal V, wherein the first port D is coupled to the drain (first terminal) of the first transistor Q1 and the drain (first terminal) of the second transistor Q2, the second port S is coupled to the source (second terminal) of the first transistor Q1, the third port G is coupled to the control terminal of the first transistor Q1, and the fourth port V is coupled to the second terminal of the second transistor Q2 for providing a start-up current.

With continued reference to fig. 2. The second port S of the power transistor module 10 is coupled to the ground reference, the start terminal V of the power transistor module 10 is coupled to the first terminal CTR of the control circuit 11, and the control terminal G of the power transistor module 10 is coupled to the second terminal Gate of the control circuit 11. In one embodiment, the ground reference to which the second port S is coupled is the ground reference of the control circuit 11. When the circuit is started, the input impedance of the first end CTR of the control circuit 11 is low impedance, the voltages on the fourth port V and the second port S are low level, the voltage difference between the fourth port V and the second port S is smaller than a first threshold value, and the first port D and the fourth port V are in a low impedance conduction state. During normal operation, due to normal operation of the power transistor Q1, the power supply circuit 12 generates a voltage for supplying power to the control circuit 11, the voltage at the port CTR rises, the voltage at the fourth port V of the transistor module 10 rises, and the input impedance of the control terminal CTR of the control circuit 11 is high impedance. In the illustrated embodiment, the power supply circuit 12 includes an auxiliary winding Na, a diode D, and a capacitor C1. When the voltage difference between the fourth port V and the second port S is greater than the second threshold, the first port D and the fourth port V are in a high-impedance cutoff state. Wherein the second threshold is greater than the first threshold.

The second port S of the transistor module may also be coupled to other nodes. In one embodiment, the second port S is externally coupled to a sampling resistor. In another embodiment, the second port S is externally coupled to a ground reference of the input power source, wherein a voltage difference between the third port G and the second port S has a sufficient magnitude for driving the first transistor Q1.

Continuing with the description of fig. 2, during the start-up phase, when the second transistor Q2 is in the on state, the current flows into the drain terminal D as the first current, and flows from the start-up terminal V to the control circuit 11 for providing the start-up current for the control circuit 11, and the voltage at the control terminal G is lower, such as lower than the third threshold, and the first transistor Q1 does not operate normally. In the working phase, the system is powered by the power supply circuit 12, the second transistor Q2 is turned off, no current flows out from the starting terminal V of the module 10, and the voltage at the control terminal G is greater than a fourth threshold value at least for a part of the time, so as to drive the first transistor Q1 to work, wherein the third threshold value is less than the fourth threshold value. The transistor Q1 can be operated in a switching state and a linear amplification state, wherein the third threshold and the fourth threshold can be reference voltages of any suitable magnitude for qualitatively indicating that the first transistor Q1 is in an off state or an operating state.

The grid electrode of the second transistor Q2 is internally connected with the source electrode of the first transistor Q1, namely, the starting function is integrated in the power transistor module, so that the pins of the power transistor wafer with the starting function are reduced to the maximum extent, the integration of the starting circuit and the power transistor is realized by only adopting four external ports, the integration level is improved, and the control is simple.

fig. 4 shows a circuit schematic of a transistor module 20 with a start-up function and a current sensing function according to an embodiment of the invention. The transistor module 20 has five ports, which are a drain terminal D, a source terminal S, a start terminal V, a control terminal G and a detection terminal CS. Compared with the transistor module 10 shown in fig. 2, the transistor module 20 has a sensing terminal CS added thereto, and the sensing terminal CS is coupled to a third terminal CS of the control circuit 21 except for the ports CTR and Gate for providing a current sensing function, so that the control circuit 21 controls the output current of the first transistor Q1 based on the current sensing signal CS. The transistor module 20 further includes a third transistor Q3, wherein the first terminal (drain) of the third transistor Q3 is connected to the first terminal (drain) of the first transistor Q1, and the control terminal (gate) of the third transistor Q3 is connected to the control terminal (gate) of the first transistor Q1. A second terminal (source) of the third transistor Q3 is coupled to a second terminal (source) of the first transistor Q1 through a resistor R, and a second terminal (source) of the third transistor Q3 provides a current sense signal. With such a connection, the current flowing through the third transistor Q3 is proportional to the current flowing through the first transistor Q1, and the voltage signal at the sensing terminal CS is proportional to the current flowing through the first transistor Q1, i.e., the voltage signal at the sensing terminal CS is proportional to the current signal flowing from the source terminal S, so that the current sensing is realized. The resistor R may be any resistor suitable for semiconductor fabrication. Because the resistance value and the withstand voltage of the resistor R are small, the integration can be conveniently realized by doping the semiconductor part region, and the integration is convenient.

In one embodiment, the transistor module with the start-up function and the current detection function is fabricated on the same semiconductor substrate to form a semiconductor chip, wherein the power transistor module chip has only five pins corresponding to the drain pin D, the source pin S, the start-up pin V, the control pin G, and the detection pin CS, respectively.

Fig. 5 shows a schematic diagram of a voltage conversion circuit according to an embodiment of the invention. The voltage conversion circuit includes a primary winding Np, a transistor module 30 coupled to the primary winding Np, a control circuit 31, a secondary winding Ns, an auxiliary winding Na, and a capacitor C1. One end of the primary winding receives an input voltage source Vin, and the other end of the primary winding is coupled to the transistor module 30, specifically, to a power switch in the transistor module 30. In one embodiment, transistor module 30 is a semiconductor module. The control circuit 31 has a first terminal CTR coupled to the transistor module 30 or the semiconductor module for receiving the start-up current flowing from the fourth port V of the transistor module 30, and a second terminal Gate for controlling the power transistor or the power switch in the transistor module 30. The secondary winding N is coupled to a secondary rectifier Do for providing the output voltage Vout. The capacitor C1 is coupled to the auxiliary winding Na and the third terminal VDD of the control circuit 31, wherein when the system is started and the input impedance of the first terminal CTR of the control circuit 31 is smaller than the first resistance value, the transistor module 30 or the semiconductor module provides a starting current to the first terminal CTR of the control circuit 31 for charging the capacitor C1, providing a starting voltage to the control circuit 31, and further providing a driving signal to the power switch in the transistor module 30, under the operation of the power switch, energy is transferred from the primary winding Np to the secondary winding Ns for providing an output voltage Vout at the output terminal, while the supply voltage at the port VDD gradually rises through the auxiliary winding Na, and the voltage at the second terminal CTR of the control circuit rises with the rise of the voltage at the port VDD. When the system works normally, the voltage at the port CTR is high, the input impedance of the first terminal CTR of the control circuit 31 is greater than the second resistance value, the start transistor in the transistor module 30 is turned off, and the capacitor C1 is completely powered by the auxiliary winding Na. The first resistance value is smaller than the second resistance value, and the first resistance value and the second resistance value can be reference values in any suitable range and are used for qualitatively describing the electrical characteristics of the embodiment.

According to some embodiments of the invention, the power transistor module with the starting function can provide the starting current function by additionally manufacturing only one transistor in the power transistor module without using an additional external resistor or an additional integrated resistor, so that the power consumption of the system is extremely low, and the process is simple. Meanwhile, the power transistor module with the starting function can only have four external pins through the connection of two internal transistors, the system integration level is high, and the control is simple.

The description and applications of the invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the invention.