TWI736275B - Power supply device for over current protection - Google Patents

Abstract

A power supply device for over current protection includes a first transformer, an output stage circuit, a detection circuit, a second transformer, a protection circuit, and a control IC (Integrated Circuit). The first transformer includes a first main coil for receiving an input voltage, a first secondary coil for generating a first induced voltage, and an auxiliary coil for generating a second induced voltage. The output stage circuit generates an output current according to the first induced voltage. The detection circuit monitors the output current and generates a detection voltage according to the output current. The second transformer includes a second main coil for receiving the detection voltage, and a second secondary coil for generating a control voltage. The protection circuit selectively enables or disables the control IC according to the second induced voltage and the control voltage.

Description

Power supply with over-current protection function

The present invention relates to a power supply, and particularly relates to a power supply with overcurrent protection function.

Traditional power supplies usually design a sensing resistor at its output terminal to achieve the function of overcurrent protection. However, if the power of the power supply is large, the sensing resistor must withstand a large dynamic current. It is prone to damage after multiple use cycles, and at the same time, the reliability of the power supply is insufficient. In view of this, it is necessary to propose a new solution to overcome the difficulties faced by the previous technology.

In a preferred embodiment, the present invention provides a power supply with overcurrent protection function, including: a first transformer, including a first main coil, a first auxiliary coil, and an auxiliary coil, wherein the first transformer The main coil is used to receive an input potential, the first auxiliary coil is used to generate a first induced potential, and the auxiliary coil is used to generate a second induced potential; an output stage circuit, according to the first induced potential To generate an output current; a detection circuit to monitor the output current, and generate a detection potential according to the output current; a second transformer, including a second main coil and a second auxiliary coil, wherein the second The main coil is used to receive the detection potential, and the second auxiliary coil is used to generate a control potential; a control integrated circuit; and a protection circuit, selectively based on the second induced potential and the control potential Enable or disable the control integrated circuit.

In order to make the purpose, features and advantages of the present invention more comprehensible, specific embodiments of the present invention are listed below, with the accompanying drawings, and detailed descriptions are as follows.

Certain vocabulary is used to refer to specific elements in the specification and the scope of the patent application. Those skilled in the art should understand that hardware manufacturers may use different terms to refer to the same component. This specification and the scope of the patent application do not use differences in names as a way to distinguish elements, but use differences in functions of elements as a criterion for distinguishing. The terms "including" and "including" mentioned in the entire specification and the scope of the patent application are open-ended terms and should be interpreted as "including but not limited to". The term "approximately" means that within an acceptable error range, those skilled in the art can solve the technical problem within a certain error range and achieve the basic technical effect. In addition, the term "coupling" includes any direct and indirect electrical connection means in this specification. Therefore, if it is described in the text that a first device is coupled to a second device, it means that the first device can be directly electrically connected to the second device, or indirectly electrically connected to the second device through other devices or connection means. Two devices.

FIG. 1 is a schematic diagram of a power supply 100 according to an embodiment of the invention. For example, the power supply 100 can be applied to a desktop computer, a notebook computer, or an integrated computer. As shown in FIG. 1, the power supply 100 includes a first transformer 110, an output stage circuit 120, a detection circuit 130, a second transformer 140, a protection circuit 150, and a control integrated circuit 160. It should be noted that although not shown in Figure 1, the power supply 100 may further include other components, such as a voltage regulator or (and) a negative feedback circuit.

The first transformer 110 includes a first main winding 111, a first auxiliary winding 112, and an auxiliary winding 113. Both the first main winding 111 and the auxiliary winding 113 can be located on the same side of the first transformer 110, and the first auxiliary winding The coil 112 may be located on the opposite side of the first transformer 110. The first main coil 111 can receive an input potential VIN, and in response to the input potential VIN, the first auxiliary coil 112 can generate a first induced potential VS1, and the auxiliary coil 113 can generate a second induced potential VS2. The input potential VIN can come from an external input power source, where the input potential VIN can have any frequency and any amplitude. For example, the frequency of the input potential VIN may be about 50 Hz or 60 Hz, and the root mean square value of the input potential VIN may be about 110V or 220V, but it is not limited to this. The output stage circuit 120 can generate an output current IOUT according to the first induced potential VS1. The detection circuit 130 can monitor the output current IOUT, and generate a detection potential VD according to the output current IOUT. In some embodiments, the output stage circuit 120 can further generate an output potential VOUT, which can be transmitted to an electronic device via the detection circuit 130. The second transformer 140 includes a second main coil 141 and a second auxiliary coil 142. The second main coil 141 can be located on one side of the second transformer 140, and the second auxiliary coil 142 can be located opposite to the second transformer 140. The other side. The second main coil 141 can receive the detection potential VD, and in response to the detection potential VD, the second auxiliary coil 142 can generate a control potential VC. The protection circuit 150 can selectively enable or disable the control integrated circuit 160 according to the second induced potential VS2 and the control potential VC. According to the monitoring and detection results of the detection circuit 130, if the output current IOUT has not reached a critical value, the protection circuit 150 will be enabled to control the integrated circuit 160, and if the output current IOUT has reached the aforementioned critical value, the protection circuit 150 The control integrated circuit 160 will be disabled. The control integrated circuit 160 can be regarded as one of the processing cores of the power supply 100. If it is disabled, the power supply 100 will also be shut down synchronously to achieve the effect of over-current protection. Under this design, since the output current IOUT can be completely monitored and limited, the combination of the detection circuit 130, the second transformer 140, and the protection circuit 150 can effectively prevent the internal components of the power supply 100 from being damaged, thereby The reliability of the power supply 100 can be improved.

The following embodiments will introduce the detailed structure and operation of the power supply 100. It must be understood that these drawings and descriptions are only examples, and are not used to limit the scope of the present invention.

FIG. 2 is a schematic diagram of the power supply 200 according to an embodiment of the invention. In the embodiment of Figure 2, the power supply 200 has an input node NIN and an output node NOUT, and includes a first transformer 210, an output stage circuit 220, a detection circuit 230, a second transformer 240, A protection circuit 250, and a control integrated circuit 260. The input node NIN of the power supply 200 can receive an input potential VIN from an external input power source, and the output node NOUT of the power supply 200 can output an output potential VOUT to an electronic device.

The first transformer 210 includes a first main winding 211, a first auxiliary winding 212, and an auxiliary winding 213. Both the first main winding 211 and the auxiliary winding 213 can be located on the same side of the first transformer 210, and the first auxiliary winding The coil 212 may be located on the opposite side of the first transformer 210. The first end of the first main coil 211 is coupled to the input node NIN, and the second end of the first main coil 211 is coupled to a ground potential VSS (for example, 0V). The first end of the first auxiliary winding 212 is coupled to a first node N1 to output a first induced potential VS1, and the second end of the first auxiliary winding 212 is coupled to a second node N2. The first end of the auxiliary coil 213 is coupled to a third node N3 to output a second induced potential VS2, and the second end of the auxiliary coil 213 is coupled to the ground potential VSS.

The output stage circuit 220 includes a first diode D1 and a first capacitor C1. The anode of the first diode D1 is coupled to the first node N1 to receive the first induced potential VS1, and the cathode of the first diode D1 is coupled to a fourth node N4. The first terminal of the first capacitor C1 is coupled to the fourth node N4, and the second terminal of the first capacitor C1 is coupled to the second node N2. The fourth node N4 is used to output an output current IOUT to the detection circuit 230.

The detection circuit 230 includes a first transistor M1, a second capacitor C2, a third capacitor C3, and a second diode D2. The first transistor M1 may be an N-type MOSFET, and the first transistor M1 has a built-in parasitic capacitor CP1. The control terminal of the first transistor M1 is coupled to the fourth node N4, the first terminal of the first transistor M1 is coupled to a fifth node N5, and the second terminal of the first transistor M1 is coupled to The fourth node N4. It must be noted that the total parasitic capacitance between the first terminal and the second terminal of the first transistor M1 can be simulated as the aforementioned parasitic capacitor CP1, which is not an external independent component. The first end of the parasitic capacitor CP1 is coupled to the fourth node N4, and the second end of the parasitic capacitor CP1 is coupled to the fifth node N5. The first end of the second capacitor C2 is coupled to the fourth node N4 to receive the output current IOUT, and the second end of the second capacitor C2 is coupled to the output node NOUT. The first end of the third capacitor C3 is coupled to the fifth node N5, and the second end of the third capacitor C3 is coupled to the output node NOUT. The anode of the second diode D2 is coupled to the fourth node N4, and the cathode of the second diode D2 is coupled to a sixth node N6 to output a detection potential VD. It should be noted that the detection potential VD here can be equivalent to a potential difference between the sixth node N6 and the output node NOUT.

The second transformer 240 includes a second main coil 241 and a second secondary coil 242. The second primary coil 241 can be located on one side of the second transformer 240, and the second secondary coil 242 can be located opposite to the second transformer 240. The other side. The first end of the second main coil 241 is coupled to the sixth node N6 to receive the detection potential VD, and the second end of the second main coil 241 is coupled to the output node NOUT. The first end of the second auxiliary winding 242 is coupled to a seventh node N7 to output a control potential VC, and the second end of the second auxiliary winding 242 is coupled to the ground potential VSS.

The protection circuit 250 includes a second transistor M2, a third diode D3, and a fourth capacitor C4. The second transistor M2 can be an N-type MOSFET. The control terminal of the second transistor M2 is coupled to the seventh node N7 to receive the control potential VC, the first terminal of the second transistor M2 is coupled to the ground potential VSS, and the second terminal of the second transistor M2 is It is coupled to the third node N3 to receive the second induced potential VS2. The anode of the third diode D3 is coupled to the third node N3, and the cathode of the third diode D3 is coupled to a supply node NP. The first end of the fourth capacitor C4 is coupled to the supply node NP, and the second end of the fourth capacitor C4 is coupled to the ground potential VSS. The supply node NP is used to output a supply potential VP to the control integrated circuit 260.

On the whole, if the output current IOUT has not reached a critical value, the protection circuit 250 will output the supply potential VP with a high logic level so as to control the integrated circuit 260; on the contrary, if the output current IOUT has reached the aforementioned critical value, then The protection circuit 250 outputs the supply potential VP with a low logic level to disable the control of the integrated circuit 260.

FIG. 3 is a schematic diagram showing the equivalent capacitor 370 of the detection circuit 230 according to an embodiment of the present invention. As shown in Figure 3, when the first transistor M1 is activated, the total capacitance value of the equivalent capacitor 370 of the detection circuit 230 (that is, the total capacitance value between the fourth node N4 and the output node NOUT) can be as follows As described in the following equation (1):

…………………………………..(1)

其中「CT」代表偵測電路230之等效電容器370之總電容值，「CP1」代表寄生電容器CP1之電容值，「C2」代表第二電容器C2之電容值，而「C3」代表第三電容器C3之電容值。

…………………………………..(1)

Where "CT" represents the total capacitance value of the equivalent capacitor 370 of the detection circuit 230, "CP1" represents the capacitance value of the parasitic capacitor CP1, "C2" represents the capacitance value of the second capacitor C2, and "C3" represents the third capacitor The capacitance value of C3.

On the other hand, since the output current IOUT will pass through the parasitic capacitor CP1, the second capacitor C2, and the third capacitor C3 at the same time, its correlation with the charge stored in the equivalent capacitor 370 of the detection circuit 230 can be as shown in the following equation (2 ) Said:

…………………………….(2) 其中「Q」代表等效電容器370所儲存之電荷，「CT」代表等效電容器370之總電容值，「VD」代表偵測電位VD之位準，「IOUT」代表輸出電流IOUT之大小，而「TD」代表輸出電流IOUT通過等效電容器370所費之延遲時間(此處假設第二二極體D2為理想，其切入電位可視同0V)。

………………………. (2) where "Q" represents the charge stored in the equivalent capacitor 370, "CT" represents the total capacitance of the equivalent capacitor 370, and "VD" represents the detection potential VD "IOUT" represents the magnitude of the output current IOUT, and "TD" represents the delay time for the output current IOUT to pass through the equivalent capacitor 370 (here assuming that the second diode D2 is ideal, the cut-in potential can be regarded as the same 0V).

In some embodiments, the power supply 200 can operate in a normal mode or a protection mode, and the operating principles will be as follows, respectively.

In the normal mode, the output current IOUT has not reached a critical value, so the equivalent capacitor 370 of the detection circuit 230 has not stored enough charge. At this time, the detection potential VD and the corresponding control potential VC are both relatively low to turn off the second transistor M2, and the protection circuit 250 will output the supply potential VP with a high logic level to control the integrated circuit 260.

In the protection mode, the output current IOUT has reached the aforementioned threshold, so the equivalent capacitor 370 of the detection circuit 230 has stored enough charge. At this time, the detection potential VD and the corresponding control potential VC are both relatively high to activate the second transistor M2, and the protection circuit 250 will output the supply potential VP with a low logic level to disable the control integrated circuit 260. Since the control integrated circuit 260 can be regarded as one of the processing cores of the power supply 200, the disabled control integrated circuit 260 will synchronously shut down the power supply 200 to prevent the excessive output current IOUT from causing internal circuit damage.

Fig. 4 shows a potential waveform diagram of the power supply 200 according to an embodiment of the present invention, in which the horizontal axis represents time, and the vertical axis represents potential level or current value. According to the measurement result in Figure 4, when the output current IOUT rises and reaches a critical value ITH, both the detection potential VD and the corresponding control potential VC will rise synchronously, and finally, the second transistor M2 will form a short-circuit path And disable the control integrated circuit 260, so that the output potential VOUT of the power supply 200 drops to 0V quickly.

In some embodiments, the component parameters of the power supply 200 may be as described below. The capacitance value of the first capacitor C1 may be between 646 μF and 714 μF, preferably 680 μF. The capacitance value of the second capacitor C2 can be between 108.9 mF and 111.1 mF, preferably 110 mF. The capacitance value of the third capacitor C3 may be between 9.9 mF and 10.1 mF, and preferably may be 10 mF. The ratio of the number of turns of the first main coil 211 to the first auxiliary coil 212 may be between 5 and 100, preferably 20. The ratio of the number of turns of the first main coil 211 to the auxiliary coil 213 may be between 0.5 and 10, preferably 1.33. The ratio of the number of turns of the second main coil 241 to the second auxiliary coil 242 may be between 0.1 and 5, preferably 0.67. The critical value ITH of the output current IOUT can be between 10A and 30A, preferably 21.97A. The delay time for the output current IOUT to pass through the equivalent capacitor 370 may be between 10 mS and 100 mS, and preferably may be 50 mS. The above parameter range is based on the results of many experiments, which helps to optimize the overcurrent protection function and reliability of the power supply 200.

The present invention provides a novel power supply, which includes a negative feedback mechanism formed by a detection circuit and a protection circuit. According to the actual measurement results, the use of the aforementioned power supply design can greatly reduce the risk of damage due to excessive output current. Because the design of the traditional sensing resistor is discarded, the present invention can further improve the reliability of the power supply, so it is very suitable for application in various types of devices.

It is worth noting that the above-mentioned potential, current, resistance value, inductance value, capacitance value, and other component parameters are not limitations of the present invention. The designer can adjust these settings according to different needs. The power supply of the present invention is not limited to the state shown in Figures 1-4. The present invention may only include any one or more of the features of any one or more of the embodiments in FIGS. 1-4. In other words, not all the features shown in the figures need to be implemented in the power supply of the present invention at the same time. Although the embodiment of the present invention uses metal oxide half field effect transistors as an example, the present invention is not limited to this. Those skilled in the art can use other types of transistors, such as junction field effect transistors or fins. Type field effect transistors, etc., without affecting the effect of the present invention.

Although the present invention is disclosed as above in the preferred embodiment, it is not intended to limit the scope of the present invention. Anyone who is familiar with the art can make some changes and modifications without departing from the spirit and scope of the present invention. Therefore, The scope of protection of the present invention shall be subject to those defined by the attached patent scope.

100,200: power supply 110,210: the first transformer 111, 211: the first main coil 112,212: the first secondary coil 113,213: auxiliary coil 120, 220: output stage circuit 130, 230: detection circuit 140, 240: second transformer 141, 241: second main coil 142,242: The second secondary coil 150, 250: protection circuit 160,260: control integrated circuit 370: Equivalent capacitor of detection circuit C1: The first capacitor C2: second capacitor C3: third capacitor C4: The fourth capacitor CP1: Parasitic capacitor D1: The first diode D2: The second diode D3: The third diode IOUT: output current ITH: critical value M1: The first transistor M2: second transistor N1: the first node N2: second node N3: third node N4: Fourth node N5: fifth node N6: sixth node N7: seventh node NIN: input node NOUT: output node NP: supply node VC: control potential VD: Detection potential VIN: input potential VOUT: output potential VP: supply potential VS1: First induction potential VS2: second induction potential VSS: Ground potential

Fig. 1 is a schematic diagram of a power supply according to an embodiment of the invention. FIG. 2 is a schematic diagram of the power supply according to an embodiment of the invention. FIG. 3 is a schematic diagram showing the equivalent capacitor of the detection circuit according to an embodiment of the present invention. Fig. 4 shows a potential waveform diagram of the power supply according to an embodiment of the invention.

100: power supply

110: The first transformer

111: The first main coil

112: The first secondary coil

113: auxiliary coil

120: output stage circuit

130: detection circuit

140: second transformer

141: The second main coil

142: The second secondary coil

150: Protection circuit

160: control integrated circuit

IOUT: output current

VC: control potential

VD: Detection potential

VIN: input potential

VOUT: output potential

VS1: First induction potential

VS2: second induction potential

Claims (7)

A power supply with overcurrent protection function includes: a first transformer, including a first main coil, a first auxiliary coil, and an auxiliary coil, wherein the first main coil is used to receive an input potential, The first auxiliary coil is used to generate a first induced potential, and the auxiliary coil is used to generate a second induced potential; an output stage circuit generates an output current according to the first induced potential; a detection circuit , Monitor the output current, and generate a detection potential according to the output current; a second transformer, including a second main coil and a second auxiliary coil, wherein the second main coil is used to receive the detection potential , And the second auxiliary coil is used to generate a control potential; a control integrated circuit; and a protection circuit to selectively enable or disable the control integrated circuit according to the second induced potential and the control potential Wherein the first main coil has a first end and a second end, the first end of the first main coil is coupled to an input node to receive the input potential, the second of the first main coil The terminal is coupled to a ground potential, the first secondary coil has a first terminal and a second terminal, and the first terminal of the first secondary coil is coupled to a first node to output the first induced potential , The second end of the first auxiliary coil is coupled to a second node, the auxiliary coil has a first end and a second end, and the first end of the auxiliary coil is coupled to a The third node outputs the second induced potential, and the second end of the auxiliary coil is coupled to the ground potential; wherein the output stage circuit includes: a first diode having an anode and a cathode, wherein The anode of the first diode is coupled to the first node to receive the first induced potential, and the cathode of the first diode is coupled to a fourth node; and a first capacitor, Having a first terminal and a second terminal, wherein the first terminal of the first capacitor is coupled to the fourth node, and the second terminal of the first capacitor is coupled to the second node; wherein The fourth node is used to output the output current to the detection circuit; wherein the detection circuit includes: a first transistor having a control terminal, a first terminal, and a second terminal, wherein the first transistor The control terminal of the transistor is coupled to the fourth node, the first terminal of the first transistor is coupled to a fifth node, and the second terminal of the first transistor is coupled to the The fourth node. The power supply of claim 1, wherein the first transistor system has a built-in parasitic capacitor, the parasitic capacitor has a first terminal and a second terminal, and the first terminal of the parasitic capacitor is coupled to The fourth node and the second terminal of the parasitic capacitor are coupled to the fifth node. The power supply according to claim 1, wherein the detection circuit further includes: A second capacitor has a first terminal and a second terminal, wherein the first terminal of the second capacitor is coupled to the fourth node to receive the output current, and the second terminal of the second capacitor Is coupled to an output node; a third capacitor has a first end and a second end, wherein the first end of the third capacitor is coupled to the fifth node, and the third capacitor The second end is coupled to the output node; and a second diode having an anode and a cathode, wherein the anode of the second diode is coupled to the fourth node, and the second diode The cathode of the polar body is coupled to a sixth node to output the detection potential. The power supply of claim 3, wherein the second main coil has a first end and a second end, and the first end of the second main coil is coupled to the sixth node to receive the detection To measure the potential, the second end of the second main coil is coupled to the output node, the second auxiliary coil has a first end and a second end, and the first end of the second auxiliary coil is coupled To a seventh node to output the control potential, and the second end of the second auxiliary coil is coupled to the ground potential. The power supply of claim 4, wherein the protection circuit includes: a second transistor having a control terminal, a first terminal, and a second terminal, wherein the control terminal of the second transistor is Coupled to the seventh node to receive the control potential, the first terminal of the second transistor is coupled to the ground potential, and the second terminal of the second transistor is coupled to the third node To receive the second induced potential. The power supply of claim 5, wherein the protection circuit further comprises: a third diode having an anode and a cathode, wherein the anode of the third diode is coupled to the third node , And the cathode of the third diode is coupled to a supply node; and a fourth capacitor having a first end and a second end, wherein the first end of the fourth capacitor is coupled to The supply node and the second end of the fourth capacitor are coupled to the ground potential; wherein the supply node is used to output a supply potential to the control integrated circuit. The power supply of claim 6, wherein if the output current has not reached a critical value, the protection circuit will output the supply potential with a high logic level to enable the control integrated circuit, and if the output current Having reached the critical value, the protection circuit will output the supply potential with a low logic level to disable the control integrated circuit.

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