TWI720681B - 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 primary detection circuit, and an over temperature adjustment circuit. The primary side control unit obtains a primary voltage change value through the primary detection circuit, and the primary side control unit correspondingly provides a current change value to the over temperature adjustment circuit according to the primary 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 primary 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, the power converter must reach a fixed temperature or higher to be able to trigger the resistance value of the over-temperature protection. Therefore, when the input voltage 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 risk of damage to the power converter.

Specifically, because the conversion efficiency of the power converter is different when the input voltage is low or high, or the power converter is overloaded, the trigger point of the over-temperature protection is actually due to the difference in input voltage or output current. The difference 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. On the contrary, when the input voltage of the power converter is low, the conversion efficiency is poor, which makes the heat loss caused by the energy conversion Lose more. Therefore, the power converter will actually trigger the over-temperature protection mechanism at different trigger points under the above-mentioned difference.

Especially in the safety regulations after IEC62368, when the power converter is abnormal, the maximum surface temperature of the controller's plastic casing shall not exceed 87 degrees Celsius. Therefore, in the above-mentioned specifications, when the input voltage of the power converter is high, or the output current is overloaded, 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. However, if the design is below this trigger point and the power converter is at a high input voltage, there is a large margin of error from the actual trigger point of the over-temperature protection mechanism, making the over-temperature protection mechanism meaningless.

Therefore, how to design a power converter with over-temperature protection compensation, which is set on the primary 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 Adjusting the temperature protection point is an important subject that the inventor intends to study.

In order to solve the above-mentioned 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, which receives an input voltage, and includes a primary side, which is coupled to a primary rectifier filter circuit. The primary side control unit is coupled to the primary side. The primary detection circuit is coupled to the primary side control unit, and the primary detection circuit includes a resistor, which is coupled to the primary rectification filter circuit or the main conversion unit. And the voltage dividing element, coupled to the resistor. And the temperature adjustment circuit is coupled to the primary side control unit. its In this case, the primary side control unit learns the change value of the primary voltage through the primary detection circuit, and the primary side control unit correspondingly provides the current change value to the over temperature adjustment circuit according to the change of the primary voltage change value; the over temperature adjustment circuit changes according to the current change The value of the temperature control voltage is provided, so that the primary side control unit judges whether to activate the over-temperature protection according to the temperature control voltage. Among them, 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 primary side control unit; the resistor receives the detection voltage corresponding to the input voltage, and provides the primary voltage through the node according to the detection voltage Change value.

In one embodiment, the primary rectification filter circuit includes: a primary rectification circuit, which receives the input power. And the primary filter circuit is coupled to the primary rectifier circuit and the primary side. Among them, the primary rectifier circuit rectifies the input voltage into a rectified voltage, and the primary filter circuit filters the rectified voltage into a DC voltage.

In one embodiment, the primary detection circuit is coupled to the primary filter circuit, and the primary detection circuit provides the primary voltage change value according to the DC voltage; or, the primary detection circuit is coupled to the primary rectifier circuit, and the primary detection circuit is based on the input Voltage and provide the primary voltage change value.

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

In one embodiment, the primary 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 primary side control unit turns off the main conversion unit to activate the over-temperature protection.

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

In one embodiment, it further includes an auxiliary winding, which is coupled to the primary detection circuit and the main conversion unit. Wherein, the auxiliary winding obtains the auxiliary voltage through the main conversion unit, and the primary detection circuit provides the primary voltage change value according to the auxiliary voltage.

In one embodiment, the primary detection circuit further includes: a diode coupled to a resistor. Among them, the diode limits the polarity of the detection voltage.

In order to solve the above-mentioned problems, the present invention provides another 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 the primary side is coupled to a primary rectifier filter circuit. The primary side control unit is coupled to the primary side. The primary detection circuit is coupled to the primary side control unit. And the temperature adjustment circuit is coupled to the primary side control unit. Among them, the primary side control unit learns the primary voltage change value corresponding to the input voltage through the primary detection circuit, and the primary side control unit provides a fixed current value to the over-temperature adjustment circuit according to the primary voltage change value; the over-temperature adjustment circuit is based on the input voltage The resistance change value is generated correspondingly to the change of, and the temperature control voltage is provided according to the fixed current value and the resistance change value, so that the primary side control unit judges whether to activate the over-temperature protection according to the temperature control voltage.

In an embodiment, the over-temperature adjustment circuit includes: a temperature compensation circuit, which is coupled to the primary side control unit. And a temperature control resistor, coupled to the temperature compensation circuit. Among them, the temperature compensation circuit correspondingly generates a resistance change value according to the change of the input voltage, and the temperature control resistance generates a temperature control resistance value according to the ambient temperature; the fixed value of current flows through the resistance change value and the temperature control resistance value to generate a temperature control voltage .

In one embodiment, when the input voltage is higher, the resistance change value provided by the temperature compensation circuit is higher, and when the input voltage is lower, the resistance change value provided by the temperature compensation circuit is lower.

In one embodiment, the temperature compensation circuit includes a detection circuit coupled to the primary rectification filter circuit or the main conversion unit. The voltage control switch is coupled to the detection circuit. The control unit is coupled to the pressure control switch. And a compensation resistor, coupled to the control unit. Among them, the detection circuit receives the detection voltage corresponding to the input voltage, and provides a voltage change value according to the detection voltage; the voltage control switch provides a control signal according to the voltage change value, and the control unit adjusts the resistance change of the compensation resistor according to the control signal value.

In one embodiment, the compensation resistor includes: a first compensation resistor, coupled to the primary side control unit, the temperature control resistor, and the control unit. And the second compensation resistor, coupled to the primary side control unit and the temperature control Resistance and control unit. Wherein, the control unit controls the first compensation resistor to be connected in parallel or not in parallel to the second compensation resistor according to the control signal to adjust the resistance change value.

In one embodiment, the temperature compensation circuit further includes a diode coupled to the detection circuit. Among them, the diode limits the polarity of the detection voltage.

In order to have a better understanding of the technology, means and effects adopted by 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.

100, 100’: Power converter

1: Primary rectifier filter circuit

12: Primary rectifier circuit

14: Primary filter circuit

2: Main conversion unit

22: Power switch

3: Secondary rectifier filter circuit

4: Control module

42, 42’: Primary side control unit

422: comparison unit

44, 44’: Primary detection circuit

442: Resistance

444: voltage divider element

D: Diode

Rs: Detection side resistance

46, 46’: Over-temperature adjustment circuit

462: temperature compensation circuit

462A: Detection circuit

462A-1: Resistance

462A-2: Voltage divider element

462B: Voltage control switch

462C: control unit

Q1: The first switch

Q2: The second switch

X: input

Y: output

Z: control end

462D: Compensation resistor

Rc1: The first compensation resistor

Rc2: second compensation resistor

Rt: temperature control resistance

48: Secondary side control unit

5: auxiliary winding

200: load

Vin: input voltage

Vo: output voltage

Vb: Rectified voltage

Vd: DC voltage

Va: auxiliary voltage

Vs: Detection voltage

Vc: Primary 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

Ip: Primary side current

Ss: Switch signal

Sf: Feedback signal

St: Over temperature signal

Sc: control signal

A, B: Node

Fig. 1 is a circuit block diagram of the first embodiment of a power converter with over-temperature protection compensation according to the present invention; Fig. 2A is a circuit block diagram of the first embodiment of the primary detection circuit detection method of the present invention; Fig. 2B is a primary circuit diagram of the present invention The circuit block diagram of the second embodiment of the detection method of the detection circuit; FIG. 2C is the circuit block diagram of the third embodiment of the primary detection circuit detection method of the present invention; FIG. 2D is the fourth embodiment of the primary detection circuit detection method of the present invention The circuit block diagram of the embodiment; FIG. 3A is the circuit diagram of the first embodiment of the primary detection circuit of the present invention; FIG. 3B is the 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 of the over-temperature adjustment circuit and the primary side control unit of the present invention; FIG. 5 is a circuit block diagram of the second embodiment of the power converter with over-temperature protection compensation according to the present invention; and FIG. 6 is the temperature of the present invention The circuit block diagram of the compensation circuit.

The technical content and detailed description of the present invention are described as follows in conjunction with the drawings: Please refer to FIG. 1 for a circuit block diagram of the first embodiment of the power converter with over-temperature protection compensation of the present invention. The power converter 100 receives an input voltage Vin, and converts the input voltage Vin into an output voltage Vo to supply power to the load 200. Among them, the power converter 100 is a power converter 100 that can accept a wide input voltage Vin, and the acceptable input voltage Vin is in a range of 90V to 264V. The power converter 100 includes a primary rectification and filter circuit 1, a main conversion unit 2, a secondary rectification and 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 rectifier filter circuit 1 includes a primary rectifier circuit 12 and a primary filter circuit 14, and the primary filter circuit 14 is coupled to the primary rectifier circuit 12 and the primary side of the main conversion unit 2. The primary rectifier circuit 12 rectifies the input voltage Vin into a rectified voltage Vb, and the primary filter circuit 14 filters the rectified voltage Vb into a DC voltage Vd.

The control module 4 includes a primary-side control unit 42, a primary detection circuit 44, an over-temperature adjustment circuit 46, and a secondary-side control unit 48. The primary-side control unit 42 is coupled to the power switch 22 of the main conversion unit 2 to provide switching The signal Ss controls the main conversion unit 2 to convert the DC voltage Vd into an output voltage Vo. The secondary side control unit 48 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 48 and the primary side control unit 42 so that the primary side control unit 42 and the secondary side control unit 48 The transmission of inter-signal has the effect of electrical isolation. The primary detection circuit 44 is coupled to the primary side control unit 42, and the primary side control unit 42 learns the primary voltage change value Vc corresponding to the change in the input voltage Vin through the primary detection circuit 44 (due to the different detection methods included) , So the input voltage Vin is represented by a dashed line). The over-temperature adjustment circuit 46 is coupled to the primary-side control unit 42, and the primary-side control unit 42 correspondingly provides the current change value Ic to the over-temperature adjustment circuit 46 according to the primary voltage change value Vc. The over temperature adjustment circuit 46 provides a temperature control voltage Vt to the primary side control unit 42 according to the current change value Ic, so that the primary side control unit 42 can determine whether to activate the over temperature protection according to the temperature control voltage Vt.

Specifically, the current change value Ic provided by the primary-side control unit 42 changes with the change of the primary voltage change value Vc, and the power converter 100 has two parameters that can affect the primary voltage change value Vc ( Shown by dashed lines). One of them is that the level of the primary voltage change value Vc varies with the level of the input voltage Vin. When the input voltage Vin is higher, the current change value Ic provided by the primary-side control unit 42 is higher, and when the input voltage Vin is lower, the current change value Ic provided by the primary-side control unit 42 is lower. The other is: the level of the primary voltage variation value Vc varies with the variation of the output current Io (that is, it varies as the load 200 is light-loaded, heavy-loaded, or overloaded). When the output current Io is high, the primary voltage change value Vc provided by the primary detection circuit 44 is relatively high, so that the current change value Ic provided by the primary-side control unit 42 is relatively high. When the output current Io is low, the primary voltage change value Vc provided by the primary detection circuit 44 is relatively low, so that the current change value Ic provided by the primary-side control unit 42 is relatively low. It is worth mentioning that, in an embodiment of the present invention, the above example of the output current Io may be reversed. That is, when the output current Io is high, the primary voltage change value provided by the primary detection circuit 44 is The higher Vc makes the current change value Ic provided by the primary-side control unit 42 lower, and so on, which will not be repeated here.

The over-temperature adjustment circuit 46 provides a temperature control voltage Vt to the primary side control unit 42 according to the current change value Ic and the ambient temperature where the over-temperature adjustment circuit 46 is located. Therefore, the over-temperature protection point of the primary-side control unit 42 to activate the over-temperature protection varies with the level of the input voltage Vin, or the over-temperature protection point of the primary-side control unit 42 to activate the over-temperature protection varies with the level of the output current Io And change. 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 level of the input voltage Vin or the output current Io. Therefore, as long as the input voltage Vin or The detection methods for the level of the output current Io can be applied to the present invention. In one embodiment of the present invention, at least four detection methods are included to determine the level of the input voltage Vin, which will be further described later.

Please refer to FIG. 2A for the circuit block diagram of the first embodiment of the primary detection circuit detection method of the present invention, FIG. 2B is the circuit block diagram of the second embodiment of the primary detection circuit detection method of the present invention, and FIG. 2C is the primary circuit diagram of the present invention The circuit block diagram of the third embodiment of the detection circuit detection method and FIG. 2D are the circuit block diagrams of the fourth embodiment of the primary detection circuit detection method of the present invention. Please refer to FIG. 1 for further cooperation. As shown in FIG. 2A, the primary detection circuit 44 is coupled to the primary filter circuit 14, and the primary detection circuit 44 provides the primary voltage change value Vc according to the DC voltage Vd. When the input voltage Vin changes, the voltage value of the DC voltage Vd stored on the primary filter circuit 14 will change with the input voltage Vin. Therefore, the change of the input voltage Vin can be obtained by detecting the DC voltage Vd on the primary filter circuit 14. As shown in FIG. 2B, the primary detection circuit 44 is coupled to the primary rectifier circuit 12, and the primary detection circuit 44 provides a primary voltage change value Vc according to the input voltage Vin. When the input voltage Vin changes, the primary detection circuit By directly detecting the input voltage Vin, the change of the input voltage Vin can be accurately known, and then a more accurate primary voltage change value Vc can be provided.

As shown in FIG. 2C, the power converter 100 further includes an auxiliary winding 5. The auxiliary winding 5 is coupled to the transformer of the main conversion unit 2 and obtains the auxiliary voltage Va through electromagnetic coupling. The primary detection circuit 44 is coupled to the auxiliary winding 5 and provides a primary voltage change value Vc according to the auxiliary voltage Va. When the level of the input voltage Vin changes, the voltage value of the auxiliary voltage Va obtained by the auxiliary winding 5 will change with the level of 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 level of 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 level of 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. As shown in FIG. 2D, the primary detection circuit 44 is coupled to the path from the power switch 22 of the main conversion unit 2 to the ground point, and the primary detection circuit 44 is provided according to the primary side current Ip flowing from the power switch 22 to the ground point. Primary voltage change value Vc. When the input voltage Vin changes, the primary side current Ip changes inversely proportional to the input voltage Vin changes. Therefore, the change of the input voltage Vin can be obtained by detecting the primary side current Ip flowing through the primary detection circuit 44. Moreover, when the output current Io changes, it will change with the output current Io. Therefore, the change of the output current Io can be known by detecting the change of the primary side current Ip. The detection methods of FIGS. 2C to 2D 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 primary side control unit 42 should be based on which of the sources is, and can be determined according to actual circuit conditions.

Since the primary detection circuit 44 includes at least the detection methods described in FIGS. 2A to 2D, the internal circuits must be different according to the detection methods described above. 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, the primary detection circuit 44 includes a resistor 442 and a voltage divider 444. The resistor 442 is coupled to the primary rectifying and filtering circuit 1 or the main conversion unit 2 (please refer to the coupling relationship in FIGS. 2A to 2C), and the voltage dividing element The piece 444 is coupled to the resistor 442. The node A between the resistor 442 and the voltage dividing element 444 is coupled to the primary side control unit 42, and the resistor 442 receives the detection voltage Vs corresponding to the input voltage Vin (please refer to FIGS. 2A~2C, and its voltage value means the input voltage Vin , DC voltage Vd or auxiliary voltage Va, and the duty ratio of the auxiliary voltage Va responds to the change of the output current Io). After the voltage value is divided by the resistor 442 and the voltage dividing element 444, the primary voltage change value Vc is provided at the node A to the primary side control unit 42. Wherein, the voltage dividing element 444 may be a voltage dividing resistor or a capacitor. When the voltage dividing element 444 is a voltage dividing resistor, the cost of the element is relatively cheap, and the dynamic response is better. When the voltage dividing element 444 is a capacitor, it has the function of energy storage. Therefore, compared with the voltage dividing resistor, it can stabilize the value of the primary voltage change value Vc, but the dynamic response is poor. Among them, the application of FIG. 3A is applicable to the above-mentioned embodiments of FIGS. 2A to 2C.

The primary detection circuit 44 may further include a diode D (indicated by a dashed line), and the diode D is coupled to the resistor 442. The diode D is used to limit the polarity of the detection voltage Vs, so as to prevent the primary voltage change value Vc from generating a voltage of wrong polarity. Specifically, the input voltage Vin and the auxiliary voltage Va may have negative voltages. When it is a negative voltage, the value of the primary voltage change value Vc generated is a negative value, which may cause the primary side control unit 42 to be unable to accept the negative voltage and be damaged (if the primary side control unit 42 itself has a limit to the primary voltage change value The function of Vc polarity is not limited to this). Therefore, the diode D must be used to limit the polarity of the detection voltage Vs to avoid the above situation. Among them, the application of the diode D is particularly suitable for the above-mentioned embodiments of FIGS. 2B and 2C.

As shown in Fig. 3B, the primary detection circuit 44' includes a detection side resistor Rs. One end of the detection side resistance Rs is coupled to the power switch 22, and the other end is coupled to the ground point, and two ends of the detection side resistance Rs are respectively two different ends of the primary side control unit 42. Since the change of the primary side current Ip is proportional to the change of the input voltage Vin, when the primary side current Ip flows through the detection side resistance Rs, the voltage drop across the detection side resistance Rs (that is, the primary voltage change value Vc) will also Changes will follow. Also, the duty ratio of the current of the primary side current Ip responds to the change of the output current Io. Therefore, the primary-side control unit 42 can detect the voltage drop across the resistor Rs. Know the change of the input voltage Vin or the change of the output current Io. Wherein, the application of the detection side resistance Rs is applicable to the above-mentioned embodiment of FIG. 2D.

Please refer to FIG. 4 for the circuit diagram of the over-temperature comparison circuit between the over-temperature adjustment circuit and the primary side control unit of the present invention, and refer to FIGS. 1 to 3B for the complex cooperation. The over-temperature adjustment circuit 46 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 primary side control unit 42 includes a comparison unit 422, and one of the input terminals of the comparison unit 422 receives the temperature control voltage Vt, and the other input terminal of the comparison unit 422 receives the reference voltage Vr. The comparison unit 422 compares the temperature control voltage Vt with the reference voltage Vr to determine whether the temperature signal St is provided, so that the primary side control unit 42 turns off the power switch 22 according to whether the temperature signal St is received, and then turns off the main conversion unit 2. Provide over temperature protection.

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 will also change with the input voltage Vin varies with the ambient temperature. Then, the reference voltage Vr of a fixed voltage value is used to compare the temperature control voltage Vt to enable the primary side control unit 42 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. 1 to 4, when the input voltage Vin is relatively high (for example, but not limited to, 264V), the voltage value of the primary voltage change value Vc obtained by the detection method of FIGS. 2A to 2C is relatively high, so that the primary side control unit 42 According to the primary voltage change value Vc of the higher voltage value, the current change value Ic of the higher current value is generated. When the input voltage Vin is low (for example, but not limited to, 90V), the voltage value of the primary voltage change value Vc obtained by the detection methods of FIGS. 2A to 2C is relatively low, so that the primary side control unit 42 is based on the primary voltage value of the lower voltage value. The voltage change value Vc produces 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 primary side control unit 42 is higher 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 the opposite of the above-mentioned input voltage of 264V, which will not be repeated here. In addition, the current change value Ic provided by the primary-side control unit 42 may be a value that linearly changes 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 linear change of the input voltage Vin), but also It can be a value that changes stepwise 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 primary-side control unit 42.

When the same example described above is applied to the embodiment of FIG. 3B, since the change of the primary side current Ip will be proportional to the change of the input voltage Vin, when the input voltage Vin is higher, the primary side current Ip will be higher. A higher primary side current Ip will produce a higher primary voltage change value Vc (that is, a higher voltage drop across the detection side resistor Rs). Therefore, when applied to the embodiment of FIG. 3B, the primary side control unit 42 will provide a current change value Ic with a higher current value (90V relative to the input voltage Vin) according to the primary voltage change value Vc with a higher voltage value, and vice versa. Provides a current change value Ic with a lower current value. It is worth mentioning that the subsequent protection control is the same as the above-mentioned embodiment, and will not be repeated here. In addition, the same example described above is applied to the embodiment of detecting the level of the output current Io, 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 in the level of the input voltage Vin, and will not be repeated here. .

Taking the circuit of FIG. 4 and the circuit of FIG. 3A as a schematic example (that is, detecting the level of the input voltage Vin), it is assumed that the primary-side control unit 42 provides over-temperature protection when the case 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, assuming that the input voltage Vin is 90V, the temperature control resistance of the temperature control resistor Rt is 1 ohm, and the input When the 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 primary side control unit 42 knows that the input voltage Vin is 90V according to the primary 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 temperature of the housing 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 primary-side control unit 42 provides over-temperature protection. When the input voltage Vin is 264V, the primary side control unit 42 knows that the input voltage Vin is 264V according to the primary 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 primary side control unit 42 provides over-temperature protection.

The same example above is applied when the primary voltage change value Vc varies with the output current Io. When the output current Io is overloaded (known by the duty cycle), the primary-side control unit 42 changes according to the primary voltage The change value Vc knows that the output current Io is overloaded. At this time, the primary side control unit 42 internally sets the delay time. After the output current Io is overloaded and exceeds the delay time, the primary-side control unit 42 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 when overloaded) must be less than 0.5V (1.5 ohm*200mA) of the over temperature protection point. Therefore, the primary-side control unit 42 provides over-temperature protection.

Please refer to FIG. 5 for the circuit block diagram of the second embodiment of the power converter with over-temperature protection compensation according to the present invention, and for further cooperation, refer to FIGS. 1 to 4. The difference between this embodiment and the first embodiment in FIG. 1 is that the primary side control unit 42' generates a fixed current value If according to the primary voltage change value Vc, and provides the fixed current value If to the over-temperature adjustment circuit 46'. That is, the fixed current value If does not change with the change in the voltage value of the input voltage Vin. In addition to the temperature control resistance value generated by the over-temperature adjustment circuit 46' according to the ambient temperature at the location, it also has a resistance change that changes the resistance value according to the voltage value of the input voltage Vin. 化值。 The value. The over temperature adjustment circuit 46' provides a temperature control voltage Vt to the primary side control unit 42' according to the current fixed value If and the resistance change value, so that the primary side control unit 42' can determine whether to activate the over temperature protection according to the temperature control voltage Vt.

Specifically, the over-temperature adjustment circuit 46' includes a temperature compensation circuit 462 and a temperature control resistor Rt, and the temperature compensation circuit 462 is coupled to the primary side control unit 42' 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 462 generates a resistance change value correspondingly 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 462 is relatively high, and when the input voltage Vin is low (for example, but not limited to, 264V), the temperature compensation circuit 462 is The provided resistance change value is low. When the fixed current value If flows through the temperature adjustment circuit 46', a first temperature control voltage will be generated in the temperature compensation circuit 462 (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 primary side control unit 42' 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 462 is not limited to the coupling manner as shown in FIG. 5, and it can be coupled between the primary side control unit 42' and the temperature control resistor Rt, or coupled Between the temperature control resistor Rt and 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. 5 are the same as those in FIG. 1, and the primary voltage change value Vc of FIGS. 2A~2D is also applicable. The detection method and the internal structure of the primary detection circuit 44 are also applicable to the circuit structures of FIGS. 3A to 3B, and will not be described here.

Please refer to FIG. 6 for the circuit block diagram of the temperature compensation circuit of the present invention, and refer to FIGS. 1 to 5 for complex cooperation. The temperature compensation circuit 462 includes a detection circuit 462A, a voltage control switch 462B, a control unit 462C, and a compensation resistor 462D. One end of the detection circuit 462A is coupled to the primary rectification filter circuit 1 or the main conversion unit 2, and the other end is coupled to one end of the voltage-controlled switch 462B. The other end of the voltage-controlled switch 462B is coupled to the working voltage One end of the Vcc and the control unit 462C, and the other end of the control unit 462C is coupled to the compensation resistor 462D, the primary side control unit 42' and the temperature control resistor Rt. Among them, the coupling positions of the primary side control unit 42' and the temperature control resistor Rt can be interchanged, and since the temperature compensation circuit 462 can be coupled to the temperature control resistor Rt and the grounding point, both ends of the compensation resistor 462D can also be The temperature control resistor Rt and the ground point are respectively coupled.

Specifically, the circuit structure of the detection circuit 462A can be the same as the circuit structure of FIG. 3A. The resistor 462A-1 is the same as the resistor 442, and the voltage dividing element 462A-2 is the same as the voltage dividing element 444. The resistor 462A-1 receives the detection voltage Vs corresponding to the input voltage Vin (please refer to Figures 2A~2C, the voltage value means the input voltage Vin, the DC voltage Vd or the auxiliary voltage Va, where the auxiliary voltage Va can be coupled by the auxiliary winding The primary or secondary winding of the transformer of the main conversion unit 2), and the node B between the resistor 462A-1 and the voltage dividing element 462A-2 provides the voltage change value Vc1 to the voltage control switch 462B. The difference between the working voltage Vcc and the voltage change value Vc1 causes the voltage-controlled switch 462B to be turned on or off to provide the control signal Sc to the control unit 462C. It is worth mentioning that the temperature compensation circuit 482 can also include a diode D (indicated by a dashed line) as shown in FIG. 3A, which is coupled to the resistor 482A-1, and has the same function as that of FIG. 3A, which will not be repeated here. In addition, the working voltage Vcc can be an externally provided voltage (for example, but not limited to, the voltage provided by an additional power supply) or a voltage provided by the power converter internally (for example, but not limited to, an additional auxiliary winding through Is coupled to the voltage generated by the main conversion unit 2).

The control unit 462C includes a first switch Q1 and a second switch Q2, and the control terminal Z of the first switch Q1 is coupled to the pressure-controlled switch 462B to receive the control signal Sc. The output terminal Y and the control terminal Z of the second switch Q2 are coupled to the input terminal X of the first switch Q1, and the input terminal X and the output terminal Y of the second switch Q2 are coupled to the compensation resistor 462D. The compensation resistor 462D includes a first compensation resistor Rc1 and a second compensation resistor Rc2, and one end of the first compensation resistor Rc1 is coupled to the output terminal Y of the second switch Q2. One end of the second compensation resistor Rc2 is coupled to the input terminal X of the second switch Q2, and the other end of the second compensation resistor Rc2 is coupled to the other end of the first compensation resistor Rc1. The control unit 462C controls the first compensation resistor Rc1 to be connected in parallel or not in parallel to the second compensation resistor Rc2 according to the control signal Sc to adjust the resistance change value of the compensation resistor 462D.

Furthermore, when the voltage value of the input voltage Vin is relatively high (for example, but not limited to, 264V), a voltage change value Vc1 with a relatively high voltage value will be generated at point B. The higher voltage value of the voltage change value Vc1 will turn on the voltage-controlled switch 462B to provide a low-level control signal Sc (that is, the control signal Sc of the ground point voltage value). The low-level control signal Sc will make the first switch Q1 of the control unit 462C non-conducting, thereby making the second switch Q2 non-conducting. Since the second switch Q2 is not turned on, the first compensation resistor Rc1 cannot be connected in parallel with the second compensation resistor Rc2, so the compensation resistor 462D provides the resistance change value of the first compensation resistor Rc1. When the voltage value of the input voltage Vin is low (for example, but not limited to, 90V), a voltage change value Vc1 with a lower voltage value will be generated at point B. The voltage variation value Vc1 of the lower voltage value will make the voltage control switch 462B non-conducting and provide a high-level control signal Sc (that is, the control signal Sc of the voltage value of the operating voltage Vcc). The high-level control signal Sc will turn on the first switch Q1 of the control unit 462C, thereby turning on the second switch Q2. Due to the conduction of the second switch Q2, the first compensation resistor Rc1 is connected in parallel with the second compensation resistor Rc2, so that the compensation resistor 462D provides the resistance change value of the resistance of the first compensation resistor Rc1 in parallel with the second compensation resistor Rc2.

Refer to Figures 4 to 5 for the complex coordination. The internal circuit structure of the primary side control unit 42' is the same as that shown in Figure 4. 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 resistance change value is larger than when the input voltage Vin is 90V, so the fixed current value If and temperature control The product of the resistance Rt and the resistance change value is large, so that the obtained temperature control voltage Vt is higher than when the input voltage Vin is 90V. Therefore, the voltage value of the temperature control voltage Vt when the input voltage Vin is 264V 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 the opposite of the above-mentioned input voltage of 264V, which will not be repeated here. In addition, since the primary-side control unit 42' of the embodiment of FIG. 5 can use a conventional controller, it uses the temperature compensation circuit 462 that generates different resistance changes according to the voltage value of the input voltage Vin to generate an over-temperature protection point. With the input voltage Different and changing characteristics. 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 voltage Vin of the power converter 100, thereby avoiding the risk of delaying the over-temperature protection.

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 for the over-temperature protection of the over-temperature protection according to the level of the input voltage or the level of the output current. point. Therefore, the over-temperature protection point of the primary-side control unit to activate the over-temperature protection changes with the level of the input voltage or the level of the output current. Therefore, through the above compensation method, the over-temperature protection cannot be triggered normally due to the difference in efficiency under the conditions of different input voltages or different output currents 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 scope of the patent application and the specification can be implemented individually or in any combination.

100: power converter

1: Primary rectifier filter circuit

12: Primary rectifier circuit

14: Primary filter circuit

2: Main conversion unit

22: Power switch

3: Secondary rectifier filter circuit

4: Control module

42: Primary side control unit

422: comparison unit

44: Primary detection circuit

46: Over temperature adjustment circuit

48: Secondary side control unit

200: load

Vin: input voltage

Vo: output voltage

Vb: Rectified voltage

Vd: DC voltage

Vc: Primary voltage change value

Vt: temperature control voltage

Io: output current

Ic: current change value

Ss: Switch signal

Sf: Feedback signal

Claims (14)

A power converter with over-temperature protection compensation includes: a main conversion unit that receives an input voltage, and includes a primary side coupled to a primary rectifier filter circuit; a primary side control unit coupled to the primary side Side; a primary detection circuit, coupled to the primary side control unit, the primary detection circuit includes: a resistor, coupled to the primary rectifier filter circuit or the main conversion unit; and a voltage divider element, coupled to the resistor; And an over-temperature adjustment circuit, coupled to the primary side control unit; wherein the primary side control unit learns a primary voltage change value through the primary detection circuit, and the primary side control unit changes according to the primary voltage change value And correspondingly provide a current change value to the over temperature adjustment circuit; the over temperature adjustment circuit provides a temperature control voltage according to the current change value, so that the primary side control unit judges whether to activate an over temperature protection according to the temperature control voltage 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 primary side control unit; the resistor receives a detection voltage corresponding to the input voltage, And according to the detection voltage, the primary voltage change value is provided through the node. The power converter according to claim 1, wherein the primary rectifier filter circuit includes: a primary rectifier circuit receiving the input voltage; and a primary filter circuit coupled to the primary rectifier circuit and the primary side; wherein, the primary rectifier circuit The circuit rectifies the input voltage into a rectified voltage, and the primary filter circuit filters the rectified voltage into a DC voltage. The power converter according to claim 2, wherein the primary detection circuit is coupled to the primary filter circuit, and the primary detection circuit provides the primary voltage change value according to the DC voltage; or Furthermore, the primary detection circuit is coupled to the primary rectifier circuit, and the primary detection circuit provides the primary voltage change value according to the input voltage. The power converter according to claim 1, wherein the over-temperature adjustment circuit includes a temperature-control resistor, the temperature-control resistor generates a temperature-control resistance value according to the ambient temperature, and the current change value flows through the temperature-control resistance value And the temperature control voltage is generated. The power converter according to claim 1, wherein the primary-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 primary-side control unit turns off the main conversion unit, To activate the over-temperature protection. The power converter according to claim 1, wherein when the input voltage is higher, the current change value provided by the primary-side control unit is higher, and when the input voltage is lower, the primary-side control unit provides The current change value is low. The power converter according to claim 1, further comprising: an auxiliary winding coupled to the primary detection circuit and the main conversion unit; wherein the auxiliary winding obtains an auxiliary voltage through the main conversion unit, and the primary The detection circuit provides the primary voltage change value according to the auxiliary voltage. The power converter according to claim 1, wherein the primary detection circuit further includes: a diode coupled to the resistor; wherein the diode limits the polarity of the detection voltage. A power converter with over-temperature protection compensation includes: a main conversion unit including a primary side coupled to a primary rectifier filter circuit; a primary side control unit coupled to the primary side; and a primary detection A circuit, coupled to the primary-side control unit; and an over-temperature adjustment circuit, coupled to the primary-side control unit; Wherein, the primary side control unit learns a primary voltage change value corresponding to an input voltage through the primary detection circuit, and the primary side control unit provides a fixed current value to the over-temperature adjustment circuit according to the primary voltage change value The over-temperature adjustment circuit correspondingly generates a resistance change value according to the change in the input voltage, and provides a temperature control voltage according to the fixed current value and the resistance change value, so that the primary side control unit is based on the temperature control voltage Determine whether to activate an over-temperature protection. The power converter according to claim 9, wherein the over-temperature adjustment circuit includes: a temperature compensation circuit coupled to the primary side control unit; and a temperature control resistor coupled to the temperature compensation circuit; wherein the temperature compensation circuit The circuit correspondingly generates the resistance change value according to the change of the input voltage, and the temperature control resistor generates a temperature control resistance value according to an ambient temperature; the fixed value of current flows through the resistance change value and the temperature control resistance value. This temperature control voltage is generated. The power converter according to claim 10, wherein when the input voltage is higher, the resistance change value provided by the temperature compensation circuit is higher, and when the input voltage is lower, the resistance provided by the temperature compensation circuit The change value is low. The power converter according to claim 10, wherein the temperature compensation circuit includes: a detection circuit coupled to the primary rectification filter circuit or the main conversion unit; a voltage-controlled switch coupled to the detection circuit; and a control Unit, coupled to the voltage control switch; and a compensation resistor, coupled to the control unit; wherein, the detection circuit receives a detection voltage corresponding to the input voltage, and provides a voltage change value according to the detection voltage; The voltage control switch provides a control signal according to the voltage change value, and the control unit adjusts the resistance change value of the compensation resistor according to the control signal. The power converter according to claim 12, wherein the compensation resistor includes: a first compensation resistor coupled to the primary side control unit, the temperature control resistor, and the control unit; and A second compensation resistor is coupled to the primary side control unit, the temperature control resistor, and the control unit; wherein the control unit controls the first compensation resistor to be connected in parallel or not in parallel to the second compensation resistor according to the control signal to Adjust the resistance change value. The power converter according to claim 12, wherein the temperature compensation circuit further includes: a diode coupled to the detection circuit; wherein the diode limits the polarity of the detection voltage.

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