TW202037051A - Power converter with over temperature protection compensation - Google Patents

Abstract

A power converter with over temperature protection compensation includes a main conversion unit, a primary side control unit, a secondary side control unit, a secondary detection circuit, and an over temperature adjustment circuit. The secondary side control unit obtains a secondary voltage change value through the secondary detection circuit, and the secondary side control unit correspondingly provides a current change value to the over temperature adjustment circuit according to the secondary voltage change value. The over temperature adjustment circuit provides a temperature control voltage according to the current change value, so that the primary side control unit determines whether an over temperature protection is activated or not according to the temperature control voltage.

Description

Power converter with over-temperature protection compensation

The present invention relates to a power converter with over-temperature protection and compensation, in particular to a power converter with over-temperature protection and compensation arranged on the secondary side of a conversion unit.

In the technical field of power converters, the over temperature protection (OTP) mechanism of the internal controller of the power converter has always been indispensable. However, no matter whether the input voltage of the power converter is low voltage or high voltage, or the output current is light load or full load, the power converter must reach a fixed temperature or higher to trigger the resistance value of the over temperature protection. Therefore, when the input voltage or output current of the power converter changes, the actual trigger point of the over-temperature protection mechanism will be different. This will cause the controller to delay the activation of the over-temperature protection mechanism, thereby increasing the damage of the power converter. risk.

Specifically, because the power converter has different conversion efficiency when the input voltage is low or high voltage, or when the output current is light load or full load, the trigger point of the over-temperature protection will actually be due to the difference in input voltage or output The current varies. Generally, the input voltage of the power converter is high, and the conversion efficiency is good, so that the heat loss caused by the energy conversion is small. Conversely, when the input voltage of the power converter is low, the conversion efficiency is poor, which causes more heat loss due to energy conversion. Therefore, the actual trigger point of the over-temperature protection mechanism of the power converter is different under the above-mentioned difference.

Especially in the safety regulations after IEC62368, the maximum surface temperature of the controller's plastic casing shall not exceed 87 degrees Celsius when the power converter is abnormal. Therefore, in the above-mentioned specifications, when the input voltage of the power converter is high, or the output current is full load or light load, it is easy to cause the power converter to actually be overloaded, but the over-temperature protection mechanism is not activated. In order to avoid such a situation, it may be necessary to design the trigger point of the over-temperature protection mechanism at the trigger point where the input voltage of the power converter is low or the output current is light load. However, if the design is below this trigger point, and the power converter is at high input voltage or full output current, there is a large margin of error from the actual trigger point of the over-temperature protection mechanism, which makes the over-temperature protection The mechanism loses its meaning.

Therefore, how to design a power converter with over-temperature protection compensation, which is set on the secondary side of the conversion unit, and compensates the over-temperature protection points according to the input voltage of different voltage values or the output current of different loads, so as to dynamically The local adjustment of the temperature protection point is an important subject that the inventor intends to study.

In order to solve the above problems, the present invention provides a power converter with over-temperature protection compensation to overcome the problems of the prior art. Therefore, the power converter with over-temperature protection compensation of the present invention includes a main conversion unit including a primary side and a secondary side, the primary side is coupled to the input voltage, and the secondary side is coupled to the secondary rectifier filter circuit. The primary side control unit is coupled to the primary side. The secondary side control unit is coupled to the primary side control unit. The secondary detection circuit is coupled to the secondary side. And the temperature adjustment circuit is coupled to the secondary side control unit. Wherein, the secondary side control unit learns the change value of the secondary voltage through the secondary detection circuit, and the secondary side control unit correspondingly provides the current change value to the over temperature adjustment circuit according to the secondary voltage change value; the over temperature adjustment circuit The temperature control voltage is provided according to the current change value, so that the secondary side control unit judges whether to activate the over temperature protection according to the temperature control voltage.

In one embodiment, the secondary-side control unit shuts down the main conversion unit through the primary-side control unit to activate the over-temperature protection.

In one embodiment, it further includes: a protection switch coupled to the secondary rectification filter circuit. Among them, the secondary side control unit turns off the protection switch to start over temperature protection.

In one embodiment, the over-temperature adjustment circuit includes a temperature-controlled resistor, and the temperature-controlled resistor generates a temperature-controlled resistance according to the ambient temperature, and the current change value flows through the temperature-controlled resistance to generate a temperature-controlled voltage.

In one embodiment, the secondary side control unit includes a comparison unit, and when the comparison unit determines that the temperature control voltage is lower than the reference voltage, the secondary side control unit activates the over-temperature protection.

In one embodiment, when the input voltage is higher, the current change value provided by the secondary side control unit is higher, and when the input voltage is lower, the current change value provided by the secondary side control unit is lower.

In one embodiment, it further includes an auxiliary winding coupled to the secondary detection circuit and the main conversion unit. Wherein, the auxiliary winding obtains the auxiliary voltage corresponding to the input voltage change or the output current change provided by the secondary rectification filter circuit through the main conversion unit, and the secondary detection circuit provides the secondary voltage change value according to the auxiliary voltage.

In one embodiment, the secondary detection circuit includes a resistor coupled to the auxiliary winding. And the voltage dividing element, coupled to the resistor. The voltage dividing element is a voltage dividing resistor or a capacitor, and the node between the resistor and the voltage dividing element is coupled to the secondary side control unit; the resistor receives the auxiliary voltage, and provides the secondary voltage change value through the node according to the auxiliary voltage.

In an embodiment, the secondary input voltage detection circuit further includes a diode coupled to a resistor. Among them, the diode limits the polarity of the auxiliary voltage.

In one embodiment, the secondary detection circuit is coupled to the secondary rectification and filter circuit, and the secondary voltage change value is obtained according to the change of the output current provided by the secondary rectification and filter circuit.

In one embodiment, the secondary detection circuit includes a detection side resistor, which is coupled to the secondary rectification filter circuit and the secondary side control unit. Among them, the output current flows through the detection side resistance to produce the secondary voltage change value.

In one embodiment, the secondary-side control unit provides the secondary voltage change value according to the handshaking signal provided by the load.

In order to further understand the technology, means and effects of the present invention to achieve the intended purpose, please refer to the following detailed description and drawings of the present invention. I believe that the purpose, features and characteristics of the present invention can be obtained from this in depth and For specific understanding, however, the accompanying drawings are only provided for reference and illustration, and are not intended to limit the present invention.

The technical content and detailed description of the present invention are described as follows with the drawings:

Please refer to FIG. 1 for a circuit block diagram of a first embodiment of a power converter with over-temperature protection compensation according to the present invention. The power converter 100 receives the input voltage Vin, and converts the input voltage Vin into an output voltage Vo to supply power to the load 200. The power converter 100 is a power converter 100 that can accept a wide input voltage Vin, and the acceptable input voltage Vin range is 90V~264V. The power converter 100 includes a primary rectification filter circuit 1, a main conversion unit 2, a secondary rectification filter circuit 3 and a control module 4. The primary side of the main conversion unit 2 is coupled to the primary rectification and filter circuit 1, and the secondary side is coupled to the secondary rectification and filter circuit 3. The control module 4 controls the main conversion unit 2 to convert the input voltage Vin from the path of the primary rectification filter circuit 1, the main conversion unit 2 and the secondary rectification filter circuit 3 into the output voltage Vo, and the secondary rectification filter circuit 3 provides the output voltage Vo and output current Io to load 200. The primary rectifying and filtering circuit 1 rectifies and filters the input voltage Vin into a DC voltage Vd, and the main conversion unit 2 converts the DC voltage Vd into a secondary voltage Vs through the switching of the power switch 22. The secondary rectifying and filtering circuit 3 rectifies and filters the secondary voltage Vs into an output voltage Vo, and provides the output voltage Vo and the output current Io required by the load to the load 200.

The control module 4 includes a primary-side control unit 42, a secondary-side control unit 44, a secondary detection circuit 46, and an over-temperature adjustment circuit 48, and the primary-side control unit 42 is coupled to the power switch 22 of the main conversion unit 2 to provide The switching signal Ss controls the main conversion unit 2 to convert the DC voltage Vd into the secondary voltage Vs. The secondary side control unit 44 is coupled to the secondary rectification filter circuit 3, and provides a feedback signal Sf to the primary side control unit 42 according to the output voltage Vo, so that the primary side control unit 42 adjusts the switching signal Ss according to the feedback signal Sf The duty cycle, thereby stabilizing the voltage value of the output voltage Vo. Among them, a coupling unit (not shown in the figure, such as but not limited to an optical coupler) can be installed between the secondary side control unit 44 and the primary side control unit 42 so that the primary side control unit 42 and the secondary side control unit 44 The transmission of inter-signal has the effect of electrical isolation. The secondary detection circuit 46 is coupled to the secondary control unit 44, and the secondary control unit 44 obtains the secondary voltage change value Vc through the secondary detection circuit 46. The over-temperature adjustment circuit 48 is coupled to the secondary-side control unit 44, and the secondary-side control unit 44 correspondingly provides the current change value Ic to the over-temperature adjustment circuit 48 according to the secondary voltage change value Vc. The over-temperature adjustment circuit 48 provides a temperature control voltage Vt to the secondary side control unit 44 according to the current change value Ic, so that the secondary side control unit 44 can determine whether to activate the over temperature protection according to the temperature control voltage Vt.

Specifically, the level of the current change value Ic provided by the secondary-side control unit 44 changes with the change of the level of the secondary voltage change value Vc, and the power converter 100 has two types that can affect the secondary voltage change value Vc. The parameters (indicated by dotted lines). One of them is: the level of the secondary voltage variation value Vc varies with the variation of the input voltage Vin. When the input voltage Vin is higher, the secondary voltage change value Vc provided by the secondary detection circuit 46 is higher, so that the current change value Ic provided by the secondary side control unit 44 is higher. When the input voltage Vin is low, the secondary voltage change value Vc provided by the secondary detection circuit 46 is lower, so that the current change value Ic provided by the secondary side control unit 44 is lower. The other is: the secondary voltage variation value Vc varies with the variation of the output current Io (that is, it varies as the load 200 is light load, heavy load, or overload). When the output current Io is high, the secondary voltage change value Vc provided by the secondary detection circuit 46 is relatively high, so that the current change value Ic provided by the secondary side control unit 44 is relatively high. When the output current Io is low, the secondary voltage change value Vc provided by the secondary detection circuit 46 is lower, so that the current change value Ic provided by the secondary side control unit 44 is lower. It is worth mentioning that in an embodiment of the present invention, the above examples of the input voltage Vin and the output current Io may be opposite. That is, when the input voltage Vin is higher, the secondary voltage change value Vc provided by the secondary detection circuit 46 is higher, so that the current change value Ic provided by the secondary side control unit 44 is lower. And, when the output current Io is higher, the secondary voltage change value Vc provided by the secondary detection circuit 46 is higher, so that the current change value Ic provided by the secondary side control unit 44 is lower. And so on, so I won't repeat it here.

The over-temperature adjustment circuit 48 provides a temperature control voltage Vt to the secondary-side control unit 44 according to the current change value Ic and the ambient temperature where the over-temperature adjustment circuit 48 is located. Therefore, the over-temperature protection point of the secondary-side control unit 44 to activate the over-temperature protection varies with the input voltage Vin, or the over-temperature protection point of the secondary-side control unit 44 to activate the over-temperature protection varies with the output current Io The level varies. Therefore, through the above-mentioned compensation method, the over-temperature protection cannot be triggered normally due to the difference in efficiency under the conditions of different input voltage Vin or different output current Io of the power converter 100, thereby avoiding the risk of delaying the over-temperature protection.

Furthermore, the power converter 100 with over-temperature protection compensation of the present invention compensates the over-temperature protection point of the over-temperature protection according to the input voltage Vin or the output current Io. Therefore, as long as the input voltage Vin or The detection method of the output current Io can be applied to the present invention, and the detection method will be further described later.

Please refer to FIG. 2A for the circuit block diagram of the first embodiment of the secondary detection circuit detection method of the present invention, FIG. 2B for the circuit block diagram of the second embodiment of the secondary detection circuit detection method of the present invention, and FIG. 2C. The circuit block diagram of the third embodiment of the detection method of the invented secondary detection circuit is shown in FIG. 1 for complex cooperation. As shown in FIG. 2A, the power converter 100 further includes an auxiliary winding 5. The auxiliary winding 5 is coupled to the secondary side of the transformer of the main conversion unit 2 and obtains the auxiliary voltage Va through electromagnetic coupling. The secondary detection circuit 46 is coupled to the auxiliary winding 5 and provides a secondary voltage change value Vc according to the auxiliary voltage Va. Wherein, when the input voltage Vin changes, the voltage value of the auxiliary voltage Va obtained by the auxiliary winding 5 will change with the input voltage Vin. Therefore, the change of the input voltage Vin can be obtained by detecting the auxiliary voltage Va on the auxiliary winding 5. Moreover, when the output current Io changes, the duty cycle (Duty Cycle) of the auxiliary voltage Va obtained by the auxiliary winding 5 will change with the output current Io. Therefore, the change of the output current Io can be obtained by detecting the auxiliary voltage Va on the auxiliary winding 5. This detection method can be used to detect the level of the input voltage Vin or the level of the output current Io at the same time. Therefore, the secondary-side control unit 44 determines which source is the source, and can be determined according to actual circuit conditions.

As shown in FIG. 2B, the secondary detection circuit 46 is coupled to the secondary rectification filter circuit 3, and the secondary detection circuit 46 provides the secondary voltage variation value Vc according to the output current Io. When the output current Io is provided to the load 200, the output current Io flows through the secondary detection circuit 46. Therefore, the change of the output current Io can be obtained by detecting the output current Io flowing through the secondary detection circuit 46. As shown in FIG. 2C, the secondary detection circuit 46 is a communication unit inside the secondary control unit 44, and the secondary control unit 44 is coupled to the load 200 through the communication unit. The secondary side control unit 44 communicates with the load 200 through the communication unit, so that the secondary side control unit 44 can learn the secondary voltage change value Vc according to the handshaking signal Sg provided by the load 200. Specifically, in the detection method shown in FIG. 2C, the load 200 and the secondary-side control unit 44 must be a controller with a power delivery function. Through the communication between the load 200 and the secondary-side control unit 44, the secondary-side control unit 44 can learn the voltage, current, temperature, power and other information of the load 200 through the handshaking signal Sg provided by the load 200, and then use the handshaking signal Sg knows the secondary voltage change value Vc.

Since the secondary detection circuit 46 includes at least the detection methods of FIGS. 2A to 2C, in addition to the detection method of FIG. 2C that uses a communication line to couple the load 200 and the secondary side control unit 44, FIGS. 2A and 2B The internal circuit must be different according to the above detection method. Please refer to FIG. 3A for the circuit diagram of the first embodiment of the primary detection circuit of the present invention, and FIG. 3B for the circuit diagram of the second embodiment of the primary detection circuit of the present invention. As shown in FIG. 3A and in conjunction with FIG. 2A, the secondary detection circuit 46 includes a resistor 462 and a voltage divider 464. The resistor 462 is coupled to the auxiliary winding 5 (please refer to the coupling relationship in FIG. 2A ), and the voltage dividing element 464 is coupled to the resistor 462. The node A between the resistor 462 and the voltage dividing element 464 is coupled to the secondary side control unit 44, and the resistor 462 receives the auxiliary voltage Va. Wherein, the voltage value of the auxiliary voltage Va responds to the change of the input voltage Vin, and the duty ratio of the voltage of the auxiliary voltage Va responds to the change of the output current Io. The auxiliary voltage Va is divided by the resistor 462 and the voltage divider 464, and then provided at node A The secondary voltage change value Vc reaches the secondary side control unit 44. Wherein, the voltage dividing element 464 may be a voltage dividing resistor or a capacitor. When the voltage dividing element 464 is a voltage dividing resistor, the cost of the element is relatively cheap and the dynamic response is better. When the voltage divider 464 is a capacitor, it has the function of energy storage. Therefore, compared with the voltage divider resistor, it can stabilize the value of the secondary voltage change value Vc, but the dynamic response is poor.

The secondary detection circuit 46 may further include a diode D (indicated by a dashed line), and the diode D is coupled to the resistor 462. The diode D is used to limit the polarity of the auxiliary voltage Va, so as to prevent the secondary voltage change value Vc from generating a voltage of wrong polarity. Specifically, the auxiliary voltage Va may have a negative voltage (due to the switching of the power switch 22). When it is a negative voltage, the value of the secondary voltage change value Vc generated is a negative value, which may cause the secondary side control unit 44 to fail to accept the negative voltage and be damaged (if the secondary side control unit 44 itself has a limited number of times) The function of the polarity of the voltage change value Vc is not limited to this). Therefore, a diode D must be used to limit the polarity of the auxiliary voltage Va to avoid the above situation.

As shown in FIG. 3B and in conjunction with FIG. 2B, the secondary detection circuit 46' includes a detection side resistor Rs. The detection side resistance Rs is coupled to the path from the secondary rectification filter circuit 3 to the load 200, and two ends of the detection side resistance Rs are respectively connected to two different ends of the secondary side control unit 44. When the output current Io flows through the detection side resistance Rs, the voltage drop across the detection side resistance Rs (that is, the secondary voltage change value Vc) will also change accordingly. Therefore, the secondary side control unit 44 can learn the change of the output current Io through the voltage drop across the sensing side resistor Rs.

Please refer to FIG. 4 for a circuit diagram of the over-temperature comparison circuit between the over-temperature adjustment circuit and the primary-side control unit of the present invention. The temperature control circuit 48 includes a temperature control resistor Rt (for example, but not limited to, a negative temperature coefficient resistor), and the temperature control resistor Rt generates a temperature control resistance value according to the ambient temperature of the location. When the ambient temperature is higher, the temperature control resistance value is smaller, and when the ambient temperature is lower, the temperature control resistance value is larger. When the current change value Ic flows through the temperature control resistor Rt, a voltage drop will be generated across the temperature control resistor Rt, and the voltage drop is the temperature control voltage Vt. The secondary side control unit 44 includes a comparison unit 442, and one of the input terminals of the comparison unit 442 receives the temperature control voltage Vt, and the other input terminal of the comparison unit 442 receives the reference voltage Vr. The comparison unit 442 compares the temperature control voltage Vt with the reference voltage Vr to determine whether the over-temperature signal St is provided, so that the secondary side control unit 44 provides over-temperature protection according to whether the over-temperature signal St is received.

Specifically, since the current change value Ic changes with the input voltage Vin or the output current Io, and the temperature control resistance changes with the ambient temperature, the temperature control voltage Vt also changes with the input voltage Vin varies with ambient temperature (or varies with output current Io and ambient temperature). Then, the reference voltage Vr of the fixed voltage value is used to compare the temperature control voltage Vt to enable the secondary side control unit 44 to know whether the over temperature protection needs to be activated. Among them, the value of the reference voltage Vr is the point of over temperature protection.

Please refer to Figures 1~4, and take the input voltage Vin as an example. When the input voltage Vin is relatively high (for example, but not limited to, 264V), the voltage value of the secondary voltage change value Vc obtained by the detection method in FIG. 2A is relatively high, so that the secondary side control unit 44 is based on the secondary voltage value of the higher voltage value. Step-by-step voltage change value Vc produces a higher current value current change value Ic. When the input voltage Vin is low (for example, but not limited to, 90V), the voltage value of the secondary voltage change value Vc obtained by the detection method of FIG. 2A is relatively low, so that the secondary side control unit 44 performs the second order according to the lower voltage value. The step voltage change value Vc generates a current change value Ic with a lower current value.

When the ambient temperature is a fixed value (that is, the temperature control resistance value is a fixed value), when the input voltage Vin is 264V, the temperature control voltage Vt obtained by the secondary side control unit 44 is lower than when the input voltage Vin is 90V When the input voltage Vin is 264V, the voltage value of the temperature control voltage Vt is farther from the over-temperature protection point (that is, the reference voltage Vr) than when the input voltage Vin is 90V. Therefore, if the ambient temperature fluctuates, when the input voltage Vin is 264V, a higher ambient temperature (90V relative to the input voltage Vin) is required to trigger the over-temperature protection. It is worth mentioning that when the input voltage is 90V, it is exactly the opposite of the above-mentioned input voltage of 264V, and will not be repeated here. In addition, the current change value Ic provided by the secondary side control unit 44 may be a value that changes linearly according to the linear change of the input voltage Vin (that is, the curve of the current change value Ic is proportional to the curve of the input voltage Vin), but It can also be a value that changes in sections according to the linear change of the input voltage Vin (for example, but not limited to, the changed points are 90V, 170V, 264V), which can be adjusted according to the resolution set by the secondary side control unit 44. When the above-mentioned same example is applied to the embodiment of FIG. 3B, the change of the current change value Ic is proportional to the level of the output current Io, which is similar to the above-mentioned difference of the level of the input voltage Vin, and will not be repeated here.

Take the circuit of FIG. 4 with the circuits of FIGS. 2A and 3A as an example, and the level of the secondary voltage change value Vc changes with the change of the input voltage Vin. It is assumed that the secondary side control unit 44 provides over-temperature protection when the casing temperature of the power converter 100 is set at 90 degrees, and the voltage of the over-temperature protection is 0.5V (that is, the reference voltage is 0.5V). Under this condition, suppose that when the input voltage Vin is 90V, the temperature control resistance of the temperature control resistor Rt is 1 ohm, and when the input voltage Vin is 264V, the temperature control resistance of the temperature control resistor Rt is 2 ohms. When the input voltage Vin is 90V, the secondary side control unit 44 knows that the input voltage Vin is 90V according to the secondary voltage change value Vc, and provides a current change value Ic of 500 mA to the temperature control resistor Rt. At this time, if the housing temperature of the power converter 100 reaches 90 degrees, the temperature control voltage Vt generated by the temperature control resistance Rt and the current change value Ic is 0.5V (1 ohm*500mA). Therefore, the secondary side control unit 44 provides over-temperature protection. When the input voltage Vin is 264V, the secondary side control unit 44 knows that the input voltage Vin is 264V according to the secondary voltage change value Vc, and provides a current change value Ic of 250 mA to the temperature control resistor Rt. At this time, if the housing temperature of the power converter 100 reaches 90 degrees, the temperature control voltage Vt generated by the temperature control resistance Rt and the current change value Ic is 0.5V (2 ohm*250mA). Therefore, the secondary side control unit 44 provides over-temperature protection.

The same example above is applied in the case where the secondary voltage change value Vc changes with the change of the output current Io (meaning that the load status is known by the duty cycle of the auxiliary voltage Va), and the calculation of the over-temperature protection The method is similar to the situation in which the level of the secondary voltage change value Vc changes with the change of the input voltage Vin. When the output current Io is overloaded (known by the duty cycle), the secondary side control unit 44 knows that the output current Io is overloaded according to the secondary voltage change value Vc. At this time, the secondary side control unit 44 sets a delay time internally. After the output current Io is overloaded and exceeds the delay time, the secondary side control unit 44 changes the current change value Ic to 200 mA. Due to the overload condition, the resistance value of the temperature control resistor Rt must be less than 2 ohms (because the ambient temperature rises, the resistance value of the temperature control resistor Rt becomes smaller). Therefore, the temperature control voltage Vt generated by the temperature control resistance Rt and the current change value Ic (assuming that the temperature control resistance Rt is 1.5 ohms during overload) must be less than 0.5V (1.5 ohm*200mA) of the over temperature protection point. Therefore, the secondary side control unit 44 provides over-temperature protection.

When the circuit of FIG. 4 is combined with the circuits of FIG. 2B and FIG. 3B, the calculation method of the over-temperature protection is similar to the above-mentioned situation where the level of the secondary voltage change value Vc changes with the change of the output current Io. That is, when the load is light, the output current Io is lower, so that the voltage drop across the detection side resistor Rs (that is, the secondary voltage change value Vc) is lower. When the load is full, the output current Io is higher, so that the voltage drop across the detection side resistor Rs (that is, the secondary voltage change value Vc) is higher. When the load is overloaded, the secondary side control unit 44 also sets a delay time. When the delay time is exceeded and the load is still overloaded, the secondary side control unit 44 will reduce the current change value Ic. The rest of the calculation, that is, the control method, is the same as the situation in which the level of the secondary voltage change value Vc changes with the change of the output current Io, and will not be repeated here.

Please refer to FIG. 5A for the circuit block diagram of the first embodiment of the over-temperature protection method of the present invention. Please refer to FIG. 5B for the circuit block diagram of the second embodiment of the over-temperature protection method of the present invention. The secondary side control unit 44 has at least two protection modes for starting the over-temperature protection, and the protection mode can select at least one of the protection modes for over-temperature protection according to the actual circuit conditions. As shown in FIG. 5A, when the secondary-side control unit 44 receives the over-temperature signal St provided by the comparison unit 442, the secondary-side control unit 44 provides a protection signal Sp corresponding to the over-temperature signal St to the primary-side control unit 42. After receiving the protection signal Sp, the primary side control unit 42 turns off the main conversion unit 2 by turning off the power switch 22 of the main conversion unit 2 so that the main conversion unit 2 no longer works to provide over-temperature protection. As shown in FIG. 5B, a protective switch 6 is connected in series on the path from the secondary rectification filter circuit 3 to the load 200. The protection switch 6 is used to provide fault protection when the power converter 100 fails. It is a necessary component in the power converter 100 with a power delivery function. Therefore, when an over-temperature occurs in the power converter 100, the protection switch 6 can also be used to protect the over-temperature. When the secondary side control unit 44 receives the over temperature signal St provided by the comparison unit 442, the secondary side control unit 44 provides the protection signal Sp corresponding to the over temperature signal St to the protection switch 6, so that the secondary side control unit 44 passes The protection switch 6 is turned off to disconnect the path from the secondary rectification filter circuit 3 to the load 200, and the over-temperature protection is activated.

Please refer to FIG. 6 for a circuit block diagram of the second embodiment of the power converter with over-temperature protection compensation according to the present invention, and for complex cooperation, refer to FIGS. 1 to 5B. The difference between this embodiment and the first embodiment in FIG. 1 is that the secondary side control unit 44' generates a fixed current value If according to the secondary voltage change value Vc, and provides the fixed current value If to the over-temperature adjustment circuit 48'. That is, the fixed current value If does not change with the voltage value of the input voltage Vin or the output current Io. The over-temperature adjustment circuit 48' not only has a temperature control resistance value generated according to the ambient temperature of the location, but also has a resistance change value that changes the resistance value according to the voltage value of the input voltage Vin. The over-temperature adjustment circuit 48' provides a temperature control voltage Vt to the secondary side control unit 44' according to the current fixed value If and the resistance change value, so that the secondary side control unit 44' can determine whether to activate the over-temperature protection according to the temperature control voltage Vt .

Specifically, the over-temperature adjustment circuit 48' includes a temperature compensation circuit 482 and a temperature control resistor Rt, and the temperature compensation circuit 482 is coupled to the secondary side control unit 44' and the temperature control resistor Rt. The temperature control resistor Rt is the same as the embodiment in FIG. 4, it generates a temperature control resistance value according to the ambient temperature of the location, and the temperature compensation circuit 482 correspondingly generates a resistance change value according to the change of the input voltage Vin. When the input voltage Vin is high (for example, but not limited to, 264V), the resistance change value provided by the temperature compensation circuit 482 is relatively high, and when the input voltage Vin is low (for example, but not limited to, 264V), the temperature compensation circuit 482 is The provided resistance change value is low. When the fixed current value If flows through the temperature adjustment circuit 48', a first temperature control voltage will be generated on the temperature compensation circuit 482 (that is, the first temperature control voltage is the product of the resistance change value and the fixed current value If), And a second temperature control voltage is generated across the temperature control resistor Rt. The first temperature control voltage plus the second temperature control voltage is the temperature control voltage Vt. Then, the secondary side control unit 44' judges whether to activate the over-temperature protection according to the temperature control voltage Vt.

It is worth mentioning that, in an embodiment of the present invention, the temperature compensation circuit 482 is not limited to the coupling manner as shown in FIG. 6, and it can be coupled between the secondary side control unit 44' and the temperature control resistor Rt, or Connect the temperature control resistor Rt to the grounding point. In addition, in an embodiment of the present invention, the undescribed circuit structure and control method of the power converter 100' of the second embodiment in FIG. 6 are the same as those in FIG. 1, and the secondary voltage change values of FIGS. 2A~2C are also applicable. The detection method of Vc and the internal structure of the secondary detection circuit 46 are also applicable to the circuit structure of FIGS. 3A to 3B, and will not be repeated here.

In summary, the main advantages and effects of the embodiments of the present invention are that the power converter with over-temperature protection compensation of the present invention compensates the over-temperature protection point of the over-temperature protection according to the level of the input voltage. Therefore, the over-temperature protection point of the secondary-side control unit to activate the over-temperature protection varies with the input voltage. Therefore, through the above compensation method, the over-temperature protection cannot be triggered normally due to the difference in efficiency under the condition of different input voltages of the power converter, thereby avoiding the risk of delaying the over-temperature protection.

However, the above are only detailed descriptions and drawings of the preferred embodiments of the present invention. However, the features of the present invention are not limited to these, and are not intended to limit the present invention. The full scope of the present invention should be referred to the following application The scope of the patent shall prevail. All embodiments that conform to the spirit of the scope of the patent application of the present invention and similar variations should be included in the scope of the present invention. Anyone familiar with the art in the field of the present invention can easily think of it. Changes or modifications can be covered in the following patent scope of this case. In addition, the features mentioned in the patent application scope and the specification can be implemented individually or in any combination.

100, 100’: Power converter

1: Primary rectifier filter circuit

2: Main conversion unit

22: Power switch

3: Secondary rectifier filter circuit

4: Control module

42: Primary side control unit

44, 44’: Secondary side control unit

442: comparison unit

46, 46’: Secondary detection circuit

462: Resistance

464: voltage divider element

D: Diode

Rs: Detection side resistance

48, 48’: Over temperature adjustment circuit

482: temperature compensation circuit

482A: Detection circuit

482A-1: Resistance

482A-2: Voltage divider element

482B: voltage control switch

482C: control unit

Q1: The first switch

Q2: The second switch

X: Input

Y: output

Z: control end

482D: Compensation resistor

Rc1: first compensation resistor

Rc2: second compensation resistor

Rt: temperature control resistance

5: auxiliary winding

6: Protection switch

200: load

Vin: input voltage

Vo: output voltage

Vd: DC voltage

Vs: secondary voltage

Va: auxiliary voltage

Va: Detection voltage

Vc: Secondary voltage change value

Vc1: Voltage change value

Vt: temperature control voltage

Vr: Reference voltage

Vcc: working voltage

Io: output current

Ic: current change value

If: current fixed value

Ss: Switch signal

Sf: Feedback signal

St: Over temperature signal

Sc: control signal

Sg: Handshaking signal

Sp: protection signal

A, B: Node

1 is a circuit block diagram of the first embodiment of a power converter with over-temperature protection compensation according to the present invention;

2A is a circuit block diagram of the first embodiment of the detection method of the primary detection circuit of the present invention;

2B is a circuit block diagram of the second embodiment of the detection method of the primary detection circuit of the present invention;

2C is a circuit block diagram of the third embodiment of the detection method of the primary detection circuit of the present invention;

3A is a circuit diagram of the first embodiment of the primary detection circuit of the present invention;

3B is a circuit diagram of the second embodiment of the primary detection circuit of the present invention;

4 is a circuit diagram of the over-temperature comparison circuit between the over-temperature adjustment circuit and the primary-side control unit of the present invention;

5A is a circuit block diagram of the first embodiment of the over-temperature protection method of the present invention;

5B is a circuit block diagram of the second embodiment of the over-temperature protection method of the present invention; and

6 is a circuit block diagram of a second embodiment of a power converter with over-temperature protection compensation according to the present invention.

100: power converter

1: Primary rectifier filter circuit

2: Main conversion unit

22: Power switch

3: Secondary rectifier filter circuit

4: Control module

42: Primary side control unit

44: Secondary side control unit

46: Secondary detection circuit

48: Over temperature adjustment circuit

200: load

Vin: input voltage

Vo: output voltage

Vd: DC voltage

Vs: secondary voltage

Vc: Secondary voltage change value

Vt: temperature control voltage

Ic: current change value

Ss: Switch signal

Sf: Feedback signal

Claims (12)

A power converter with over-temperature protection compensation, including: A main conversion unit, including a primary side and a secondary side, the primary side is coupled to an input voltage, and the secondary side is coupled to the primary rectifier filter circuit; A primary side control unit, coupled to the primary side; A secondary side control unit, coupled to the primary side control unit; A secondary detection circuit, coupled to the secondary side; and Once the temperature adjustment circuit is passed, it is coupled to the secondary side control unit; Wherein, the secondary side control unit learns the change value of the primary voltage through the secondary detection circuit, and the secondary side control unit correspondingly provides a current change value to the over-temperature adjustment according to the secondary voltage change value Circuit; The over-temperature adjustment circuit provides a temperature-controlled voltage according to the current change value, so that the secondary-side control unit determines whether to activate an over-temperature protection according to the temperature-controlled voltage. The power converter according to claim 1, wherein the secondary-side control unit shuts down the main conversion unit through the primary-side control unit to activate the over-temperature protection. The power converter according to claim 1, further including: A protection switch, coupled to the secondary rectifier filter circuit; Wherein, the secondary side control unit turns off the protection switch to start the over temperature protection. The power converter according to claim 1, wherein the over-temperature adjustment circuit includes a temperature-control resistance, the temperature-control resistance generates a temperature-control resistance value according to the ambient temperature, and the current change value flows through the temperature-control resistance value And generate the temperature control voltage. The power converter according to claim 1, wherein the secondary side control unit includes a comparison unit, and when the comparison unit determines that the temperature control voltage is lower than a reference voltage, the secondary side control unit starts the overtemperature protection. The power converter according to claim 1, wherein when the input voltage is higher, the current change value provided by the secondary-side control unit is higher, and when the input voltage is lower, the secondary-side control unit is The current change value provided is low. The power converter according to claim 1, further including: An auxiliary winding coupled to the secondary detection circuit and the main conversion unit; Wherein, the auxiliary winding obtains an auxiliary voltage corresponding to the input voltage change or the output current change provided by the secondary rectification filter circuit through the main conversion unit, and the secondary detection circuit provides the auxiliary voltage according to the auxiliary voltage. Secondary voltage change value. The power converter according to claim 7, wherein the secondary detection circuit includes: A resistor coupled to the auxiliary winding; and A voltage dividing element, coupled to the resistor; Wherein, the voltage dividing element is a voltage dividing resistor or a capacitor, and a node between the resistor and the voltage dividing element is coupled to the secondary-side control unit; the resistor receives the auxiliary voltage, and changes according to the auxiliary voltage The secondary voltage change value is provided through the node. The power converter according to claim 8, wherein the secondary input voltage detection circuit further includes: A diode, coupled to the resistor; Wherein, the diode limits the polarity of the auxiliary voltage. The power converter according to claim 1, wherein the secondary detection circuit is coupled to the secondary rectification and filter circuit, and the secondary voltage is obtained according to a change in an output current provided by the secondary rectification and filter circuit Change value. The power converter according to claim 10, wherein the secondary detection circuit includes: A detection side resistor, coupled to the secondary rectification filter circuit and the secondary side control unit; Wherein, the output current flows through the detection side resistance to generate the secondary voltage change value. The power converter according to claim 1, wherein the secondary side control unit provides the secondary voltage change value according to a handshaking signal provided by a load.

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