Power converter and its current limiting control circuit

Abstract

The present invention relates to a power converter and its current limiting control circuit. The current limiting control circuit includes a current limiting circuit unit electrically connected between a constant voltage output unit and a constant current output unit. The current limiting circuit unit includes a first arithmetic unit and a current limiting module. The first arithmetic unit receives a constant voltage signal generated by the constant voltage output unit and a divided voltage signal generated by an output current signal passing through a voltage dividing circuit unit, and generates a quasi-current limiting signal. After the quasi-current limiting signal is limited by a signal upper limit value and a signal lower limit value in the current limiting module, a current limiting signal is generated to prevent surges and improve current quality. The present invention is more efficient in current control and can better reduce the damage to the load caused by overcurrent due to surges.

Description

Technical Field

[0001] A power converter and its control circuit, especially a power converter and its current limiting control circuit. Background Art

[0002] Most current electronic products will protect their own circuits to extend the life of the products themselves. Electronic products that do not properly protect their circuits may risk losing stored data or even burning out the circuit in case of emergencies. Common emergencies include sudden power outages and sudden surges in power or a large demand for power, resulting in power grid surges. To protect their own circuits, current electronic products will have a certain inductor current feedback to mitigate the impact of emergencies on the circuit.

[0003] There is a known power supply circuit in the switching power supply of current electronic products. This power supply circuit usually includes a constant voltage (CV) output and a constant current (CC) output. First, the constant voltage output CV sets a voltage value, and then the constant current output CC determines an appropriate output current to supply power to a backend load.

[0004] In addition, the switching power supply of current electronic products often needs to face the generation of surges. When the power supply is turned on and off, surges will be generated due to the voltage difference between the power supply and the backend circuit, resulting in an overcurrent situation.

[0005] However, the known power supply circuit controls the current magnitude with the constant current output CC to generate a stable current output. When a surge occurs, the constant current output CC cannot fully control the output current, resulting in the surge affecting the output current and generating an excessive current output, which damages the circuit components in the load. Summary of the Invention

[0006] In view of the above problems, the present invention provides a current limiting control circuit for a power converter, including a current limiting circuit unit, which has a first arithmetic unit and a current limiting module. The first arithmetic unit has an output terminal, an inverting input terminal, and a non-inverting input terminal. The inverting input terminal of the first arithmetic unit receives a constant voltage signal generated by a constant voltage (CV) unit, the non-inverting input terminal of the first arithmetic unit receives a voltage dividing signal generated by a voltage dividing circuit unit, and the output terminal of the first arithmetic unit generates a quasi-current limiting signal, where the quasi-current limiting signal is connected to the inverting input terminal through a first resistor. Among them, the voltage dividing circuit unit receives an output current signal generated by a power converter to generate the voltage dividing signal.

[0007] The current limiting module is electrically connected to the output end of the first arithmetic unit and a constant current output unit, and the current limiting module receives the quasi-current limiting signal from the first arithmetic unit and outputs a current limiting signal to the constant current output unit. The current limiting module includes an upper limit DC power supply and a lower limit DC power supply. The positive terminal of the upper limit DC power supply is connected to the cathode of an upper limit diode, and the positive terminal of the lower limit DC power supply is connected to the anode of a lower limit diode. The negative terminal of the upper limit DC power supply is grounded, and the positive terminal of the upper limit DC power supply is connected to one end of the upper limit diode, while the anode of the upper limit diode is connected to the output end of the first arithmetic unit to receive the quasi-current limiting signal. The negative terminal of the lower limit DC power supply is grounded, and the cathode of the lower limit diode is connected to the output end of the first arithmetic unit to receive the quasi-current limiting signal.

[0008] The present invention utilizes inductor current feedback and through upper and lower limit circuits to achieve the limitation of the current peak value, and enables a power signal to be limited in current flow by the current limiting circuit unit before passing through the constant voltage output unit and before flowing into the constant current output unit, making the constant current output unit more efficient in current control and more capable of reducing the overcurrent caused by surges and damaging a load. Description of the Drawings

[0009] Figure 1 It is a circuit diagram of a current limiting circuit unit of a current limiting control circuit of a power converter according to the present invention.

[0010] Figure 2 It is a schematic diagram of the current limiting control circuit of the power converter in an embodiment of the present invention.

[0011] Figure 3 It is a circuit diagram near a constant voltage output unit in the embodiment of the present invention.

[0012] Figure 4 It is a circuit diagram near a current limiting circuit unit in the embodiment of the present invention.

[0013] Figure 5 It is a circuit diagram near a voltage dividing circuit unit in the embodiment of the present invention.

[0014] Figure 6 It is a circuit diagram near a comparator and a switch module in the embodiment of the present invention.

[0015] Figure 7 It is a circuit diagram of a power converter in the embodiment of the present invention.

[0016] Figure 8 It is another circuit diagram of a power converter in the embodiment of the present invention.

[0017] Figure 9This is the signal diagram of this embodiment of the present invention. Detailed implementation

[0018] The following will further elaborate on the technical means adopted by the present invention to achieve the intended invention purpose in conjunction with the drawings and the preferred embodiments of the present invention.

[0019] Please refer to Figure 1 As shown, the present invention is a current-limiting control circuit for a power converter, including a current-limiting circuit unit CL electrically connected between a constant voltage (CV) unit and a constant current (CC) unit. The current-limiting circuit unit CL has a first arithmetic unit OP1 and a current-limiting module LM. The first arithmetic unit OP1 receives a constant voltage signal V const generated by the constant voltage output unit CV and a voltage-dividing signal V Io generated by a voltage-dividing circuit unit VD, and the first arithmetic unit OP1 generates a quasi-current-limiting signal V pre_L . The first arithmetic unit OP1 has an inverting input terminal, a non-inverting input terminal, and an output terminal. The output terminal is connected to the inverting input terminal through a first resistor R1, and the constant voltage signal V const is input to the inverting input terminal through a second resistor R2. In addition, the voltage-dividing signal V Io is input to the non-inverting input terminal through a third resistor R3, and the quasi-current-limiting signal V pre_L is input to the current-limiting module LM from the output terminal through a fourth resistor R4. As Figure 2 shown, the voltage-dividing circuit unit VD receives an output current signal I o generated by a power converter PW to generate the voltage-dividing signal. The current-limiting module LM is connected to the output terminal of the first arithmetic unit OP1 through the fourth resistor R4, and the current-limiting module LM is connected to the constant current output unit CC. The current-limiting module LM receives the quasi-current-limiting signal V pre_L from the first arithmetic unit OP1 and outputs a current-limiting signal I L_refTo the constant current output unit CC. The current limiting module LM includes an upper limit DC power supply S1 and a lower limit DC power supply S2. The upper limit DC power supply S1 is connected to an upper limit diode D1, and the lower limit DC power supply S2 is connected to a lower limit diode D2. A negative terminal of the upper limit DC power supply S1 is grounded, and a positive terminal of the upper limit DC power supply S1 is connected to a cathode of the upper limit diode D1, and an anode of the upper limit diode D1 is connected to the output terminal of the first arithmetic unit OP1 through the fourth resistor R4. In addition, a negative terminal of the lower limit DC power supply S2 is grounded, and a positive terminal of the lower limit DC power supply S2 is connected to an anode of the lower limit diode D2, and a cathode of the lower limit diode D2 is also connected to the output terminal of the first arithmetic unit OP1 through the fourth resistor R4.

[0020] The forward bias direction of the upper limit diode D1 is the direction in which current flows from the quasi-current limiting signal V pre_L to the upper limit DC power supply S1, and the forward bias direction of the lower limit diode D2 is the direction in which current flows from the lower limit DC power supply S2 to the quasi-current limiting signal V pre_L .

[0021] The upper limit DC power supply S1 is provided with a signal upper limit value to limit the upper limit of the current of the quasi-current limiting signal V pre_L by controlling the voltage. The lower limit DC power supply S2 is provided with a signal lower limit value to limit the lower limit of the current of the quasi-current limiting signal V pre_L by controlling the voltage. The signal upper limit value and the signal lower limit value respectively correspond to the voltage values of the current upper limit and the current lower limit. Therefore, the flow directions of the upper limit diode D1 and the lower limit diode D2 are controlled by voltage to limit the current flow.

[0022] Specifically, when the voltage of the quasi-current limiting signal V pre_L is higher than the voltage of the signal upper limit value, the upper limit diode D1 will form a forward bias and conduct. A part of the current of the quasi-current limiting signal V pre_L will flow out from the upper limit diode D1 and pass through the upper limit DC power supply S1 to the ground, thereby limiting the voltage of the quasi-current limiting signal V pre_L . When the voltage of the quasi-current limiting signal V pre_L is lower than the voltage of the signal lower limit value, that is, when the voltage of the lower limit DC power supply S2 is higher than the voltage of the quasi-current limiting signal V pre_L , the lower limit diode D2 will form a forward bias and conduct. The current limiting signal I L_ref will receive a compensation current from the ground terminal, and the compensation current will flow in through the lower limit DC power supply S2 and the lower limit diode D2, thereby compensating the voltage of the quasi-current limiting signal V pre_L . And when the voltage of the quasi-current limiting signal V pre_LWhen the voltage is between the lower limit value and the upper limit value of the signal, the upper limit diode D1 and the lower limit diode D2 are not turned on due to reverse bias. In this way, the current limiting module LM can maintain the current limiting signal I L_ref Between the upper limit current and the lower limit current corresponding to the upper limit value and the lower limit value of the signal respectively, the purpose of limiting the current by voltage in the present invention is achieved. In addition, in a preferred embodiment, the upper limit value and the lower limit value of the signal are adjustable values.

[0023] Please refer to Figure 2 As shown, in this preferred embodiment, the current limiting control circuit of the power converter of the present invention is applied to a power device. The power device includes a power supply S3 and the power converter PW. The voltage-controlled current limiting control circuit further includes a comparator CP, the comparator CP is connected between the constant current output CC and the power converter PW of the power device, and the power converter PW is connected to the power supply S3, and the output current signal I of the power converter PW o Is output to the current limiting circuit unit CL through the voltage dividing circuit unit VD. The power converter PW is used to receive an output total power supply from the power supply S3, and the power converter PW converts the output total power supply into a converted power supply, and converts the converted power supply into an output power supply V through the inductance-capacitance unit LC o . In addition, in this embodiment, the power converter PW is a DC-AC power converter.

[0024] Please refer to together Figure 3 As shown, in this preferred embodiment, the constant voltage output unit CV is a second arithmetic unit OP2. Among them, an output voltage reference signal V from a function generator (Function Generator) FG o_ref And an output voltage signal V from the power converter PW o_fb Are connected to an inverting input terminal of the second arithmetic unit OP2, the ground is connected to a non-inverting input terminal of the second arithmetic unit OP2, and an output terminal of the second arithmetic unit OP2 generates the constant voltage signal V const . In addition, the output terminal of the second arithmetic unit OP2 is connected to the inverting input terminal of the second arithmetic unit OP2 through a fifth resistor R5 and a fifth capacitor C5.

[0025] The output voltage reference signal V o_ref Is a reference voltage signal, for example, it can come from the function generator FG, and the output voltage signal V o_fb Comes from a NO terminal and a LO terminal, and the NO terminal and the LO terminal are electrically connected to the power converter PW in the latter part of this specification Figure 7 And Figure 8 In.

[0026] Please refer to Figure 4 and Figure 5 As shown, the divided voltage signal V input to the current limiting circuit unit CL Io comes from the output current signal I passing through the voltage dividing circuit unit VD o . Specifically, the output current signal I o first passes through a current selector S before passing through the voltage dividing circuit unit VD. The current selector S selects only a small amount of current to pass through to the voltage dividing circuit unit VD, and the voltage dividing circuit unit VD uses a seventh resistor R7 and an eighth resistor R8 to divide the small portion of the output current signal I passing through the current selector S o , and outputs a voltage signal V o_fb . In this way, the current limiting circuit unit CL does not need to bear the relatively large amount of current of the output current signal I o , and can use the output voltage signal V o_fb to control the current flow of the current limiting signal I L_ref in terms of voltage.

[0027] When the output voltage reference signal V o_ref and the output voltage signal V o_fb are combined and input to the constant voltage output unit CV together, its waveform is a unique sinusoidal wave. And when the constant voltage signal V const generated by the constant voltage output unit CV and the divided voltage signal V Io are input to the current limiting circuit unit CL, the current limiting signal I L_ref output by the current limiting circuit unit CL is a wave with flattened peaks and valleys, that is, a sinusoidal wave restricted by the signal upper limit value and the signal lower limit value cannot increase its amplitude further at the current upper limit and the current lower limit, thus becoming a wave with flattened peaks and valleys. In other words, when the current limiting signal I L_ref is lower than the signal lower limit value, the current limiting signal I L_ref will receive a compensation current from the ground terminal to make the current limiting signal I L_ref maintain the amplitude of the signal lower limit value. And when the current limiting signal I L_ref is higher than the signal upper limit value, the current limiting signal I L_ref will flow to the ground from the upper limit diode D1, making the current limiting signal I L_ref maintain the amplitude of the signal upper limit value.

[0028] In this preferred embodiment, the constant current output unit CC is a third operational amplifier OP3. The current limiting signal I L_ref and a current limiting sampling signal I L_sampleConnect to an inverting input terminal of the third arithmetic unit OP3. Ground is connected to a non-inverting input terminal of the third arithmetic unit OP3, and a constant current signal I is generated at an output terminal of the third arithmetic unit OP3. const The output terminal of the third arithmetic unit OP3 is connected to the inverting input terminal of the third arithmetic unit OP3 through a sixth resistor R6 and a sixth capacitor C6.

[0029] Please refer to Figure 6 As shown, in this preferred embodiment, the comparator CP has an output terminal, an inverting input terminal, and a non-inverting input terminal. The inverting input terminal of the comparator CP is connected to a pulse-width modulation (PWM) signal generator PWMG and receives a first PWM signal PWM1. The non-inverting input terminal of the comparator CP is connected to the constant current output unit CC and receives the constant current signal I. const The output terminal of the comparator CP is connected to the power converter PW and generates a second PWM signal PWM2. The first PWM signal PWM1 is a triangular wave, and the second PWM signal PWM2 is a square wave.

[0030] Please refer to Figure 7 and Figure 8 As shown, the DC-AC power converter unit DCAC includes a switch module SW and a PWM module PWMM. The power converter PW is electrically connected to the power supply S3, and the power supply S3 is a DC power supply. The PWM module PWMM receives the second PWM signal PWM2, enables the second PWM signal PWM2 to be connected and controlled to the switch module SW through a NOT gate N1, and the switch module SW is controlled to change the total output power output by the power supply S3 into the converted power. In this preferred embodiment, the total output power is a direct current, and the converted power is an alternating current.

[0031] In another embodiment of the present invention, the switch module SW can become a boost converter, a buck converter, or a buck-boost converter according to different second PWM signals PWM2.

[0032] The inductance-capacitance unit LC is connected to the switch module SW of the DC-AC power converter DCAC, and the inductance-capacitance unit LC contains at least one inductor and at least one capacitor. In this preferred embodiment, if the power supply S3 suddenly loses power, the at least one inductor L1, L2 of the inductance-capacitance unit LC and the at least one capacitor C1, C2 can convert the respectively stored magnetic field and electric field into electric power for a period of time to buffer the time of power loss.

[0033] The inductance-capacitance unit LC also causes the current-limiting sampling signal I L_sample to reach the constant-current output unit only after passing through the inductance-capacitance unit, that is, the current-limiting sampling signal I L_sample flows to the third arithmetic unit OP3 of the constant-current output unit after passing through the inductance-capacitance unit LC, so as to enhance the current-limiting effect of the present invention. Among them, the current-limiting sampling signal I L_sample is generated by sampling the converted power supply.

[0034] As Figure 8 shown, the LO terminal and the NO terminal are led out and electrically connected to the second arithmetic unit OP2, providing power for the second arithmetic unit OP2 and the output voltage signal V o_fb . In this preferred embodiment, an electromagnetic interference filter (EMI) module is connected to the inductance-capacitance unit LC. The electromagnetic interference filter module EMI filters the current-limiting sampling signal I L_sample to generate the output current signal I o , so that the filtered output current signal I o flows to the first arithmetic unit OP1 for current feedback, so as to effectively enable the constant-current output unit CC to limit the current. The electromagnetic interference filter module EMI can filter out the surges in the circuit, prevent the surges from damaging a load during output, and also protect its own circuit from being impacted by surges when feeding back the output current signal I o .

[0035] Please refer to Figure 9 shown. In this preferred embodiment, under the condition that the load is in a full-load state, 100Vrms, 1kHz, the signal upper limit value is set to 5A, and the signal lower limit value is set to -5A. The output current signal I o is limited between -5A and 5A as shown in the figure, and shows a wave with a flattened peak and trough, which emphasizes that the present invention can effectively limit the current between the specified signal upper limit value and signal lower limit value. It can be seen that the current-limiting sampling signal I L_sample generated by the switch module SW has some fluctuations at the beginning, while the current-limiting signal I L_ref limited by the current-limiting circuit unit CL is relatively stable. This is another key point of the present invention, because it verifies that the current-limiting circuit unit CL of the present invention substantially improves the current fluctuations of all the current-limiting sampling signals I L_sample in a general circuit. The current-limiting signal I L_ref , the current-limiting sampling signal I L_sample , the output voltage signal V o_fb, the output voltage reference signal V o_ref and the output current signal I o are synchronized in time Figure 9 and recorded in. The current limiting signal I L_ref , the current limiting sampling signal I L_sample , the output voltage signal V o_fb and the output voltage reference signal V o_ref are synchronously changed with the change of the output current signal I o , indicating the synchronous consistency in the overall operation of the present invention.

[0036] The present invention feeds back the output current signal I o to a current limiting circuit unit CL for preliminary current limiting before being limited by the constant current output unit CC, which can reduce the generation of surges and more effectively limit the current flow.

[0037] The above are only the preferred embodiments of the present invention, and do not impose any form of limitation on the present invention. Although the present invention has been disclosed above with the preferred embodiments, it is not intended to limit the present invention. Any person skilled in the art can make some changes or modifications to equivalent embodiments by using the disclosed technical content within the scope of the technical solution of the present invention. However, any simple modification, equivalent change and modification made to the above embodiments based on the technical essence of the present invention still fall within the scope of the technical solution of the present invention.

Claims

1. A current limiting control circuit for a power converter, connected to a power converter, comprising: A voltage dividing circuit unit, receiving an output current signal generated by the power converter, and generating a voltage dividing signal according to the output current signal; A constant voltage output unit, generating a constant voltage signal; A current limiting circuit unit, electrically connected to the voltage dividing circuit unit and the constant voltage output unit, and receiving the constant voltage signal and the voltage dividing signal, and outputting a current limiting signal; wherein, the current limiting circuit unit further comprises: A first arithmetic unit, having an output terminal, an inverting input terminal and a non-inverting input terminal; wherein the inverting input terminal receives the constant voltage signal of the constant voltage output unit, the non-inverting input terminal receives the voltage dividing signal of the voltage dividing circuit unit, and the output terminal generates a quasi-current limiting signal, and the output terminal is connected to the inverting input terminal through a first resistor; and A current limiting module, electrically connected to the output terminal of the first arithmetic unit, and receiving the quasi-current limiting signal, and outputting the current limiting signal; wherein, the current limiting module further comprises: An upper limit DC power supply, connected to an upper limit diode, wherein a negative terminal of the upper limit DC power supply is grounded, and a positive terminal of the upper limit DC power supply is connected to a cathode of the upper limit diode, and an anode of the upper limit diode is connected to the output terminal of the first arithmetic unit; and A lower limit DC power supply, connected to a lower limit diode, wherein a negative terminal of the lower limit DC power supply is grounded, and a positive terminal of the lower limit DC power supply is connected to an anode of the lower limit diode, and a cathode of the lower limit diode is connected to the output terminal of the first arithmetic unit; It is characterized in that the output terminal of the first arithmetic unit of the current limiting circuit unit is electrically connected to a constant current output unit; Wherein the constant current output unit receives the current limiting signal and a current limiting sampling signal, and the constant current output unit outputs a constant current signal.

2. The current limiting control circuit of the power converter according to claim 1, characterized in that, Wherein before the output current signal generates the voltage dividing signal through the voltage dividing circuit unit, the output current signal first passes through a current selector and then is output to the voltage dividing circuit unit.

3. The current limiting control circuit of the power converter according to claim 1, characterized in that, Wherein the constant voltage output unit is a second arithmetic unit; Wherein, an inverting input terminal of the second arithmetic unit receives an output voltage reference signal and an output voltage signal generated by the power converter, and a non-inverting input terminal of the second arithmetic unit is grounded; Wherein, an output terminal of the second arithmetic unit is connected to the inverting input terminal of the second arithmetic unit through a fifth resistor and a fifth capacitor, and outputs the constant voltage signal.

4. The current limiting control circuit of the power converter according to claim 1, characterized in that, Wherein the constant current output unit is a third arithmetic unit; Wherein, an inverting input terminal of the third arithmetic unit receives the current limiting signal and a current limiting sampling signal, and a non-inverting input terminal of the third arithmetic unit is grounded; Wherein, an output terminal of the third arithmetic unit is connected to the inverting input terminal of the third arithmetic unit through a sixth resistor and a sixth capacitor, and outputs the constant current signal.

5. The current-limiting control circuit of the power converter according to claim 1, wherein Further comprising: A comparator having an output terminal, an inverting input terminal, and a non-inverting input terminal; wherein the inverting input terminal of the comparator receives a first pulse width modulation (PWM) signal, the non-inverting input terminal of the comparator is connected to the constant current output unit and receives the constant current signal, and the output terminal of the comparator generates a second PWM signal.

6. A power converter, characterized in that, It includes a current limiting control circuit of a power converter as described in claim 5; Wherein the power converter is electrically connected to a power supply to receive an output total power output by the power supply, and the power converter includes a switching module; Wherein the output terminal of the comparator is connected to the switching module through a NOT gate to output the second PWM signal to the switching module; Wherein the switching module is controlled according to the second PWM signal so that the switching module converts the output total power into a converted power; Wherein the current limiting sampling signal is generated by sampling the converted power.

7. The power converter according to claim 6, characterized in that Wherein the switching module is a boost converter, a buck converter, or a buck-boost converter.

8. The power converter according to claim 6, characterized in that, Further comprising: An inductor-capacitor unit connected to the switching module to receive the converted power; Wherein the converted power passes through the inductor-capacitor unit to generate an output power.

9. The power converter according to claim 8, wherein, Further comprising: An electromagnetic interference filter module connected to the inductor-capacitor unit; Wherein the inductor-capacitor unit is connected to a power output terminal of the power converter through the electromagnetic interference filter module to filter and output the output power; Wherein the output current signal is generated according to the filtered output power.

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