CN111277129B - Under-voltage starting circuit and starting method of flyback converter based on high-voltage input - Google Patents
Under-voltage starting circuit and starting method of flyback converter based on high-voltage input Download PDFInfo
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- CN111277129B CN111277129B CN201811481421.5A CN201811481421A CN111277129B CN 111277129 B CN111277129 B CN 111277129B CN 201811481421 A CN201811481421 A CN 201811481421A CN 111277129 B CN111277129 B CN 111277129B
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- H—ELECTRICITY
- H02—GENERATION; CONVERSION OR DISTRIBUTION OF ELECTRIC POWER
- H02M—APPARATUS FOR CONVERSION BETWEEN AC AND AC, BETWEEN AC AND DC, OR BETWEEN DC AND DC, AND FOR USE WITH MAINS OR SIMILAR POWER SUPPLY SYSTEMS; CONVERSION OF DC OR AC INPUT POWER INTO SURGE OUTPUT POWER; CONTROL OR REGULATION THEREOF
- H02M1/00—Details of apparatus for conversion
- H02M1/36—Means for starting or stopping converters
Abstract
The invention provides an undervoltage starting circuit and a starting method of a flyback converter based on high-voltage input, wherein a high-voltage battery converts high-voltage electricity into low-voltage electricity through an input starting circuit to provide input voltage for a control chip, the input starting circuit charges a second capacitor, and a first electrode of the second capacitor is connected with an input end of the control chip; the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage; when the enabling circuit is disconnected, the control chip is forbidden to be used, and when the power supply voltage reaches a threshold voltage, the control chip normally operates and provides a control signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter; when the output of the flyback converter is normally established, the power supply of the control chip is switched to be provided by the input starting circuit to the output voltage; the self-shutdown circuit shuts off the input starting circuit, so that the input starting circuit stops charging the first electrode of the second capacitor, and power consumption caused by the input starting circuit in normal operation is reduced.
Description
Technical Field
The invention relates to the technical field of power electronics, in particular to an under-voltage starting circuit and a starting method of a flyback converter based on high-voltage input.
Background
As the circuit structure of the vehicle-mounted inverter is more and more complex, in order to meet different functional requirements, the number of auxiliary power supplies in the inverter is more and more, a flyback converter (flyback) is a circuit generally adopted by the auxiliary power supplies in the vehicle-mounted inverter, and a simple main circuit topology can be shown in fig. 1. For the popularization of the existing new energy automobile, various working conditions of the automobile are more complex, and the new energy automobile is applied to a high-voltage battery, when the vehicle-mounted inverter is in normal power supply abnormity, an auxiliary power supply under emergency conditions is needed to drive and supply power to a core device IGBT (shown in figure 2) in the inverter, so that the inverter can conveniently take some emergency measures in the emergency state. At this time, the input power of the flyback converter 20 can only come from the high-voltage battery 10, and belongs to the single-power input condition, that is, the low-voltage battery and other devices cannot supply power to the circuit in the vehicle-mounted inverter, and all the power of the vehicle-mounted inverter can only come from the high-voltage battery; therefore, the conventional auxiliary power supply is not suitable for the situation, and because the input voltage of a control chip of the conventional auxiliary power supply is generally not higher than 60V, a high-voltage starting scheme is needed to enable the designed flyback converter circuit to be suitable for the condition of high-voltage input; however, the voltage range of the high-voltage battery is large, and the fluctuation range may be from a certain minimum voltage Vinmin to a certain maximum voltage Vinmax; compared with an auxiliary power supply for low-voltage power taking, the highest voltage input by the auxiliary power supply is not very high, the designed lowest voltage is also relatively low, but when the auxiliary power supply is used for taking power from a high-voltage battery, the highest voltage is very high, the voltage variation range is very wide, and the lowest voltage cannot be designed too low by considering proper duty ratio selection; in a common flyback converter with high-voltage input, the normal input range is from Vinmin to Vinmax during design, and the working condition lower than the lowest input voltage is generally not considered in common design; however, for the flyback converter circuit without any limitation on the input port, a critical starting voltage exists between 0 and Vinmin, the circuit does not work when being smaller than the critical starting voltage, and the circuit starts to work when being larger than the critical starting voltage. When the high-voltage battery is in a power failure state and the voltage is between the critical starting voltage and the lowest input voltage Vinmin, the circuit can work normally, and the input voltage is lower (compared with the designed lowest voltage Vinmin), and according to energy conservation, when the high-voltage battery is output in a full load state, the input current is larger; compared with the components working in the normal input range, the larger the current is, the larger the power consumption of the components is, the larger the temperature rise is, the smaller the thermal margin at high temperature is, particularly near the critical input voltage, the maximum current is realized, the higher the power consumption at high temperature is, and the thermal risk is possibly caused by the components normally designed and selected.
Disclosure of Invention
The invention aims to provide an under-voltage starting circuit and a starting method of a flyback converter based on high-voltage input, and aims to solve the problem of thermal risk caused by large input current when the input voltage of the traditional flyback converter for supplying power to a high-voltage battery is low.
In order to solve the technical problem, the invention provides an under-voltage start-up circuit of a flyback converter based on high-voltage input, wherein a high-voltage battery provides input voltage for the under-voltage start-up circuit of the flyback converter based on high-voltage input, the high-voltage battery provides an input source for the flyback converter, the under-voltage start-up circuit of the flyback converter based on high-voltage input provides a control signal for a control chip of the flyback converter, the under-voltage start-up circuit of the flyback converter based on high-voltage input comprises an input start-up circuit, an input under-voltage circuit, an enable circuit and a self-turn-off circuit, and the under-voltage start:
the high-voltage battery provides input voltage for the control chip through the input starting circuit, the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit charges a second capacitor, so that the voltage on a first electrode of the second capacitor reaches and is kept on the input voltage of the control chip, the first electrode of the second capacitor is connected with the input end of the control chip and provides the input voltage for the control chip, and a second electrode of the second capacitor is grounded;
the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage, and controls the enabling circuit to be switched on after the power supply voltage of the high-voltage battery reaches the threshold voltage;
the enabling circuit is connected between an enabling end of the control chip and an input end of the control chip, and the input voltage provides enabling voltage for the control chip through the enabling circuit;
when the enabling circuit is disconnected, the control chip is forbidden to be used; when the enabling circuit is conducted, the control chip normally operates to provide a switching signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter;
the flyback converter starts to work, the output end of the flyback converter provides output voltage to the first electrode of the second capacitor, and the output voltage enables the voltage on the first electrode of the second capacitor to reach and be kept on the input voltage of the control chip;
the self-shutdown circuit shuts off the input startup circuit to cause the input startup circuit to stop charging the first electrode of the second capacitor.
Optionally, in the under-voltage starting circuit of the flyback converter based on the high-voltage input, the input under-voltage circuit includes a plurality of under-voltage dividing resistors, a first voltage regulator tube, a first triode, a fourth resistor, and a fifth resistor, where:
the undervoltage divider resistors are connected in series to form an undervoltage series circuit, one end of the undervoltage series circuit is connected with the high-voltage battery, and the other end of the undervoltage series circuit is connected with the cathode of the first voltage-regulator tube;
the anode of the first voltage-regulator tube is connected with one end of the fourth resistor and one end of the fifth resistor, and the other end of the fourth resistor is grounded;
the other end of the fifth resistor is connected with the base electrode of the first triode;
the emitter of the first triode is grounded, and the collector of the first triode is connected with the enabling circuit; the first triode is an NPN type triode.
Optionally, in the under-voltage starting circuit of the flyback converter based on the high-voltage input, the enable circuit includes a sixth resistor, a seventh resistor, an eighth resistor, a second voltage regulator tube, a third voltage regulator tube, a first capacitor, and a second triode, where:
the anode of the second voltage-regulator tube is connected with the collector of the first triode, and the cathode of the second voltage-regulator tube is connected with one end of the sixth resistor and one end of the seventh resistor;
the other end of the sixth resistor is connected with the first electrode of the second capacitor, and the other end of the seventh resistor is connected with the base electrode of the second triode;
an emitting electrode of the second triode is connected with a first electrode of the second capacitor, a collector electrode of the second triode is connected with one end of the eighth resistor, and the second triode is a PNP triode;
the other end of the eighth resistor is connected with the cathode of the third voltage-regulator tube and the first electrode of the first capacitor, and the anode of the third voltage-regulator tube and the second electrode of the first capacitor are both grounded.
Optionally, in the under-voltage start-up circuit of the flyback converter based on the high-voltage input, the input start-up circuit includes a plurality of start voltage-dividing resistors, a fifth voltage-stabilizing tube and a field-effect transistor, wherein:
the plurality of starting voltage-dividing resistors are connected in series to form a starting series circuit, one end of the starting series circuit is connected with the high-voltage battery, and the other end of the starting series circuit is connected with the grid electrode of the field effect transistor and the cathode of the fifth voltage-stabilizing tube;
the anode of the fifth voltage regulator tube is grounded, the drain of the field effect transistor is connected with the high-voltage battery, and the source of the field effect transistor is coupled to the first electrode of the second capacitor;
the field effect transistor is a P-channel field effect transistor.
Optionally, in the under-voltage start-up circuit of the flyback converter based on the high-voltage input, the input start-up circuit further includes a first diode, where:
the cathode of the first diode is connected with the second capacitor, and the anode of the first diode is connected with the source electrode of the field effect transistor.
Optionally, in the under-voltage starting circuit of the flyback converter based on the high-voltage input, the self-turn-off circuit includes a fourth voltage regulator tube, a ninth resistor, a tenth resistor, and a third triode, where:
the cathode of the fourth voltage-regulator tube is connected with the output end of the flyback converter, the anode of the fourth voltage-regulator tube is connected with one end of the ninth resistor, the other end of the ninth resistor is connected with one end of the tenth resistor and the base electrode of the third triode, and the other end of the tenth resistor is grounded;
and the collector electrode of the third triode is connected with the grid electrode of the field effect transistor, the emitter electrode of the third triode is grounded, and the third triode is an NPN type triode.
Optionally, in the undervoltage start circuit of the flyback converter based on the high-voltage input, the undervoltage start circuit of the flyback converter based on the high-voltage input further includes a second diode, a cathode of the second diode is connected to the first electrode of the second capacitor, and an anode of the second diode is connected to the output end of the flyback converter.
Optionally, in the under-voltage starting circuit of the flyback converter based on the high-voltage input, the supply voltage of the high-voltage battery is greater than 60V.
The invention also provides an undervoltage starting method of the flyback converter based on the high-voltage input, which comprises the following steps:
the high-voltage battery provides input voltage for an under-voltage starting circuit of the flyback converter based on high-voltage input, the high-voltage battery provides an input source for the flyback converter, and the under-voltage starting circuit of the flyback converter based on the high-voltage input provides a control signal for a control chip of the flyback converter;
the high-voltage battery provides input voltage for a control chip through an input starting circuit of an undervoltage starting circuit of a flyback converter based on high-voltage input, the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit charges a second capacitor, so that the voltage on a first electrode of the second capacitor reaches and is kept on the input voltage of the control chip, the first electrode of the second capacitor is connected with the input end of the control chip and provides the input voltage for the control chip, and a second electrode of the second capacitor is grounded;
the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage, and controls the enabling circuit to be switched on after the power supply voltage of the high-voltage battery reaches the threshold voltage;
the enabling circuit is connected between an enabling end of the control chip and an input end of the control chip, and the input voltage provides enabling voltage for the control chip through the enabling circuit;
when the enabling circuit is disconnected, the control chip is forbidden to be used; when the enabling circuit is conducted, the control chip normally operates to provide a switching signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter;
the flyback converter starts to work, the output end of the flyback converter provides output voltage to the first electrode of the second capacitor, and the output voltage enables the voltage on the first electrode of the second capacitor to reach and be kept on the input voltage of the control chip;
the self-shutdown circuit shuts off the input startup circuit to cause the input startup circuit to stop charging the first electrode of the second capacitor.
The invention applies the auxiliary power supply of the flyback converter to the environment of low-voltage and low-voltage input. Compared with the conventional low-voltage auxiliary power supply, the limit of the input voltage range is improved, the input voltage can be reasonably controlled to carry out low-voltage under-voltage blocking, and the application occasions of the flyback converter circuit are widened. An enabling circuit and an input undervoltage circuit are added in the mode that the function of an enabling pin of a control chip is utilized to the maximum extent, and a low-voltage threshold can be reasonably designed to carry out low-voltage undervoltage blocking; when the low-voltage input is performed, the circuit is prevented from normally working in full load, the input current is large, the power consumption of the switch MOS tube is increased, and the thermal risk is increased at high temperature; through the undervoltage circuit, the minimum input voltage is reasonably set by the increased undervoltage blocking mechanism, and the static power consumption of the circuit and the power consumption increase and thermal risk of the switching MOS tube are avoided. Meanwhile, a relatively simple starting circuit is added on the basis of a conventional auxiliary power supply, so that the IC chip with low-voltage input can be applied to the environment with high-voltage input without risk without replacement; meanwhile, a self-turn-off circuit is added in the starting circuit for the MOS tube applied to the starting circuit, so that the MOS tube is automatically turned off after the circuit output is established, and the starting MOS tube is prevented from running for a long time when the circuit normally works, the loss is increased, and the thermal risk of a high-temperature working condition is increased.
Drawings
Fig. 1 is a schematic diagram of a prior art flyback converter;
fig. 2 is a schematic diagram of a vehicle-mounted inverter of a new energy automobile to which a conventional flyback converter is applied;
fig. 3 is a schematic diagram of an under-voltage start-up circuit of a flyback converter based on high-voltage input according to an embodiment of the present invention;
fig. 4 is a schematic diagram of a first stage of a starting process in an under-voltage starting method of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 5 is a schematic diagram illustrating the operation of a field effect transistor in an under-voltage start-up circuit of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 6 is a schematic diagram of a second stage of a starting process in an under-voltage starting method of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 7 is a third schematic diagram illustrating a starting process in an under-voltage starting method of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 8 is a schematic diagram of a fourth stage of the starting process in the under-voltage starting method of the flyback converter based on the high-voltage input according to another embodiment of the present invention;
fig. 9 is a schematic diagram of an under-voltage start-up circuit of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 10 is a schematic diagram of an under-voltage start-up circuit of a flyback converter based on high-voltage input according to another embodiment of the present invention;
fig. 11 is a schematic diagram of an under-voltage start-up circuit of a flyback converter based on high-voltage input according to another embodiment of the present invention;
shown in the figure: 10-a high voltage battery; 20-a flyback converter; 30-a control chip; 40-input start-up circuit; 50-self-turn off circuit; 60-input brown-out circuit; 70-enable circuit.
Detailed Description
The undervoltage start circuit and the start method of the flyback converter based on high-voltage input according to the present invention will be described in further detail with reference to the accompanying drawings and specific embodiments. Advantages and features of the present invention will become apparent from the following description and from the claims. It is to be noted that the drawings are in a very simplified form and are not to precise scale, which is merely for the purpose of facilitating and distinctly claiming the embodiments of the present invention.
The core idea of the invention is to provide an under-voltage starting circuit and a starting method of a flyback converter based on high-voltage input, so as to solve the problem of thermal risk caused by large input current when the input voltage of the traditional flyback converter for supplying power to a high-voltage battery is low.
In order to achieve the above idea, the present invention provides an under-voltage start circuit and a start method of a flyback converter based on high-voltage input, wherein a high-voltage battery provides an input voltage for the under-voltage start circuit of the flyback converter based on high-voltage input, the high-voltage battery provides an input source for the flyback converter, the under-voltage start circuit of the flyback converter based on high-voltage input provides a control signal for a control chip of the flyback converter, the under-voltage start circuit of the flyback converter based on high-voltage input includes an input start circuit, an input under-voltage circuit, an enable circuit and a self-shutdown circuit, wherein: the high-voltage battery provides input voltage for the control chip through the input starting circuit, the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit charges a second capacitor, so that the voltage on a first electrode of the second capacitor reaches and is kept on the input voltage of the control chip, the first electrode of the second capacitor is connected with the input end of the control chip and provides the input voltage for the control chip, and a second electrode of the second capacitor is grounded; the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage, and controls the enabling circuit to be switched on after the power supply voltage of the high-voltage battery reaches the threshold voltage; the enabling circuit is connected between an enabling end of the control chip and an input end of the control chip, and the input voltage provides enabling voltage for the control chip through the enabling circuit; when the enabling circuit is switched off, the control chip is forbidden to be used, and when the enabling circuit is switched on, the control chip normally operates to provide a switching signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter; the flyback converter starts to work, the output end of the flyback converter provides output voltage to the first electrode of the second capacitor, and the output voltage enables the voltage on the first electrode of the second capacitor to reach and be kept on the input voltage of the control chip; the self-shutdown circuit shuts off the input startup circuit to cause the input startup circuit to stop charging the first electrode of the second capacitor.
Aiming at the problems, the power supply only needs to work from a certain low-voltage threshold, the low-voltage blocking is carried out when the low-voltage input is carried out, and the power supply is supplied to the flyback converter control chip after the low-voltage and high-voltage processing is carried out on the input voltage. Therefore, the invention provides an undervoltage starting mechanism based on a high-voltage single-power-supply input flyback converter circuit, which aims to supply power to a control chip after high-voltage input is limited by an undervoltage circuit and converted by a starting circuit, so that the circuit does not work completely in a range from 0 to Vinmin to reduce static power consumption, the control chip can work normally in the whole wide input voltage range from low-voltage Vinmin to high-voltage Vinmax, and the flyback converter can output power normally in the voltage input range.
The invention provides an under-voltage starting circuit of a flyback converter based on high-voltage input, as shown in fig. 3-11, a high-voltage battery T + provides input voltage for the under-voltage starting circuit of the flyback converter based on high-voltage input, the high-voltage battery T + provides an input source for a flyback converter 20, the under-voltage starting circuit of the flyback converter based on high-voltage input provides a control signal for a control chip 30 of the flyback converter 20, the under-voltage starting circuit of the flyback converter based on high-voltage input comprises an input starting circuit 40, an input under-voltage circuit 60, an enable circuit 70 and a self-turn-off circuit 50, wherein: the high-voltage battery T + provides an input voltage for the control chip 30 through the input start circuit 40, the input voltage is lower than the output voltage of the high-voltage battery, the input start circuit 40 charges a second capacitor C2, so that the voltage on the first electrode of the second capacitor C2 reaches and is kept at the input voltage of the control chip 30, the first electrode of the second capacitor C2 is connected to the input terminal Vin of the control chip 30 and provides the input voltage for the control chip 30, and the second electrode of the second capacitor C2 is grounded; the input undervoltage circuit 60 controls the enabling circuit 70 to be turned off before the power supply voltage of the high-voltage battery T + reaches a threshold voltage (the threshold voltage is the lowest input voltage Vinmin of the fluctuation range of the high-voltage battery, that is, the normal input range during the design of the high-voltage battery is Vinmin to Vinmax), and controls the enabling circuit 70 to be turned on after the power supply voltage of the high-voltage battery T + reaches the threshold voltage; the enable circuit 70 is connected between an enable terminal EN of the control chip 30 and an input terminal Vin of the control chip 30, and the input voltage provides an enable voltage for the control chip 30 through the enable circuit 70; when the enable circuit 70 is turned off, the control chip 30 is prohibited from being used, and when the enable circuit 70 is turned on, the control chip 30 normally operates to provide a switching signal for a switching MOS transistor of the flyback converter 20; when the flyback converter 20 starts to operate, the output Vo1 of the flyback converter 20 provides an output voltage to the first electrode of the second capacitor C2, and the output voltage Vo1 makes the voltage at the first electrode of the second capacitor C2 reach and maintain the input voltage of the control chip 30; the self-shutdown circuit 50 shuts off the input start-up circuit 40, so that the input start-up circuit 40 stops charging the first electrode of the second capacitor C2 and stops supplying the input voltage to the control chip 30.
As shown in fig. 3, the input undervoltage circuit 60 is composed of 5 undervoltage resistors (the number of the combined resistance values can be adjusted according to the input voltage and the power consumption), a voltage regulator D1 and a common NPN transistor T1; the enabling circuit 70 consists of a resistor, a common PNP triode T2, a voltage regulator tube D3 and a capacitor C1; the input starting circuit 40 of the present embodiment is composed of three starting resistors R11, R12 and R13 (the number of resistors is adjustable according to the input voltage and power consumption), a voltage regulator tube D5, a field effect transistor T4 and a diode D6, and the Vds withstand voltage value of the field effect transistor T4 of the input starting circuit 40 is selected according to the maximum input voltage and the worst working condition; the self-turn-off circuit 50 is composed of a voltage regulator tube D4, two voltage dividing resistors R9 and R10 and a common NPN triode T3. The whole circuit functions in the sequence that after the high voltage is electrified, a) the input undervoltage circuit functions; b) the input starting circuit is active; c) the input undervoltage circuit fails, and the enable circuit functions; d) the control chip works (for example, NCV8871 is a reference chip); e) the main circuit of the flyback converter works; d) the self-turn-off circuit is used for turning off the MOS tube in the input starting circuit.
Specifically, the input brown-out circuit includes a plurality of brown-out voltage dividing resistors (for example, including a first resistor R1, a second resistor R2, and a third resistor R3), a first voltage regulator D1, a first triode T1, a fourth resistor R4, and a fifth resistor R5, where: the undervoltage divider resistors are connected in series to form an undervoltage series circuit, one end of the undervoltage series circuit is connected with the high-voltage battery T +, and the other end of the undervoltage series circuit is connected with the cathode of the first voltage-regulator tube D1; the anode of the first voltage regulator tube D1 is connected with one end of the fourth resistor R4 and one end of the fifth resistor R5, and the other end of the fourth resistor R4 is grounded; the other end of the fifth resistor R5 is connected with the base of the first triode T1; the emitter of the first transistor T1 is grounded, and the collector of the first transistor T1 is connected to the enabling circuit 70; the first triode T1 is an NPN type triode. The enable circuit 70 includes a sixth resistor R6, a seventh resistor R7, an eighth resistor R8, a second regulator D2, a third regulator D3, a first capacitor C1, and a second transistor T2, wherein: the anode of the second regulator tube D2 is connected to the collector of the first transistor T1, and the cathode of the second regulator tube D2 is connected to one end of the sixth resistor R6 and one end of the seventh resistor R7; the other end of the sixth resistor R6 is connected to the first electrode of the second capacitor C2, and the other end of the seventh resistor R7 is connected to the base of the second transistor T2; an emitter of the second transistor T2 is connected to the first electrode of the second capacitor C2, a collector of the second transistor T2 is connected to one end of the eighth resistor R8, and the second transistor T2 is a PNP transistor; the other end of the eighth resistor R8 is connected to the cathode of the third regulator D3 and the first electrode of the first capacitor C1, and the anode of the third regulator D3 and the second electrode of the first capacitor C1 are both grounded.
Specifically, in the under-voltage start-up circuit of the flyback converter based on the high-voltage input, the input start-up circuit 40 includes a plurality of start voltage dividing resistors (for example, an eleventh resistor R11, a twelfth resistor R12, and a thirteenth resistor R13), a fifth voltage regulator D5, and a field effect transistor T4, wherein: the plurality of starting voltage-dividing resistors are connected in series to form a starting series circuit, one end of the starting series circuit is connected with the high-voltage battery T +, and the other end of the starting series circuit is connected with the grid electrode of the field effect transistor T4 and the cathode of the fifth voltage-stabilizing tube D5; the anode of the fifth regulator tube D5 is grounded, the drain of the fet T4 is connected to the high voltage battery T +, and the source of the fet T4 is coupled to the first electrode of the second capacitor C2. The number of the resistors is 2-5. The field effect transistor T4 is a P-channel field effect transistor. The input enable circuit 40 further includes a first diode D6, wherein: the cathode of the first diode D6 is connected to the first electrode of the second capacitor C2, and the anode of the first diode D6 is connected to the source of the field effect transistor T4.
Further, in the under-voltage start-up circuit of the flyback converter based on the high-voltage input, the self-turn-off circuit 50 includes a fourth regulator D4, a ninth resistor R9, a tenth resistor R10 and a third transistor T3, wherein: a cathode of the fourth regulator tube D4 is connected to an output Vo1 of the flyback converter 20, an anode of the fourth regulator tube D4 is connected to one end of the ninth resistor R9, the other end of the ninth resistor R9 is connected to one end of the tenth resistor R10 and a base of the third transistor T3, and the other end of the tenth resistor R10 is grounded; the collector of the third transistor T3 is connected to the gate of the FET T4, and the emitter of the third transistor T3 is grounded. The third transistor T3 is an NPN transistor.
In addition, in the under-voltage start-up circuit of the flyback converter based on the high-voltage input, the under-voltage start-up circuit of the flyback converter based on the high-voltage input further includes a second diode D7, a cathode of the second diode D7 is connected to the first electrode of the second capacitor C2, and an anode of the second diode D7 is connected to the output Vo1 of the flyback converter 20. The power supply voltage of the high-voltage battery T + is more than 60V.
The invention applies the auxiliary power supply of the flyback converter to the environment of low voltage and high voltage input. Compared with the conventional low-voltage auxiliary power supply, the limit of the input voltage range is improved, the input voltage can be reasonably controlled to carry out low-voltage under-voltage blocking, and the application occasions of the flyback converter circuit are widened. An enabling circuit and an input undervoltage circuit are added in the mode that the function of an enabling pin of a control chip is utilized to the maximum extent, and a low-voltage threshold can be reasonably designed to carry out low-voltage undervoltage blocking; when the low-voltage input is performed, the circuit is prevented from normally working in full load, the input current is large, the power consumption of the switch MOS tube is increased, and the thermal risk is increased at high temperature; through the undervoltage circuit, the minimum input voltage is reasonably set by the increased undervoltage blocking mechanism, and the static power consumption of the circuit and the power consumption increase and thermal risk of the switching MOS tube are avoided. Meanwhile, a relatively simple starting circuit is added on the basis of a conventional auxiliary power supply, so that the IC chip with low-voltage input can be applied to the environment with high-voltage input without risk without replacement; meanwhile, a self-turn-off circuit is added in the starting circuit for the MOS tube applied to the starting circuit, so that the MOS tube is automatically turned off after the circuit output is established, and the starting MOS tube is prevented from running for a long time when the circuit normally works, the loss is increased, and the thermal risk of a high-temperature working condition is increased.
According to the technical idea of the invention, the input voltage can be expanded to a larger range under the condition that each circuit component is properly selected. 1) Meanwhile, the number of paths of the output of the applicable circuit is not limited to 2 paths or 3 paths, and can be extended to multiple paths, such as 4, 5 and 6 … … n. If the circuit is expanded to be applied to a multi-output circuit, as shown in FIG. 9; 2) the main circuit flyback converter can also be extended to other DCDC circuits, as shown in fig. 10; 3) the start-up scheme can also be extended to other suitable start-up circuits, as shown in fig. 11.
In summary, the above embodiments have described in detail different configurations of the under-voltage start-up circuit of the flyback converter based on the high-voltage input, and it is needless to say that the present invention includes, but is not limited to, the configurations listed in the above embodiments, and any content converted based on the configurations provided by the above embodiments is within the protection scope of the present invention. One skilled in the art can take the contents of the above embodiments to take a counter-measure.
The embodiment also provides an under-voltage starting method of the flyback converter based on the high-voltage input, as shown in fig. 5 to 7, the under-voltage starting method of the flyback converter based on the high-voltage input includes: the high-voltage battery provides input voltage for an undervoltage starting circuit of the flyback converter based on high-voltage input, and the high-voltage battery T + provides an input source for the flyback converter 20; the undervoltage starting circuit of the flyback converter based on the high-voltage input provides a control signal for a control chip of the flyback converter; the high-voltage battery T + provides an input voltage for a control chip 30 through an input starting circuit 40 of an undervoltage starting circuit of a flyback converter based on high-voltage input, wherein the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit 40 charges a second capacitor C2, the voltage on a first electrode of a second capacitor C2 reaches and is kept on the input voltage of the control chip 30, a first electrode of the second capacitor C2 is connected with the input end of the control chip 30 and provides the input voltage for the control chip 30, and a second electrode of the second capacitor C2 is grounded; the input undervoltage circuit 60 controls the enabling circuit 70 to be turned off before the power supply voltage of the high-voltage battery T + reaches the threshold voltage, and controls the enabling circuit 70 to be turned on after the power supply voltage of the high-voltage battery T + reaches the threshold voltage; the enable circuit 70 is connected between an enable terminal EN of the control chip 30 and an input terminal Vin of the control chip 30, and the input voltage provides an enable voltage for the control chip 30 through the enable circuit 70; when the enable circuit 70 is turned off, the control chip 30 is prohibited from being used, and when the enable circuit 70 is turned on, the control chip 30 normally operates to provide a switching signal for a switching MOS transistor of the flyback converter 20; the flyback converter 20 starts to operate, and the output Vo1 of the flyback converter 20 provides an output voltage to the first electrode of the second capacitor C2; the output voltage makes the voltage on the first electrode of the second capacitor C2 reach and keep on the input voltage of the control chip 30; a self-disabling circuit 50 disables the input enable circuit 40 to disable the input enable circuit 40 from charging the first electrode of the second capacitor C2.
The whole circuit functions in the sequence that a) the input undervoltage circuit functions after the high-voltage battery T + is electrified; b) the input starting circuit is active; c) the input undervoltage circuit fails, and the enable circuit functions; d) control chip operation (NCV8871 is an example reference chip); e) the main circuit of the flyback converter works; d) the self-shutdown circuit 50 functions to initiate MOS shutdown. The detailed procedure of the circuit principle can be analyzed in detail in connection with the order in which the circuits function.
1) The brown-out input circuit 60 and the input enable circuit 40 function: as shown in fig. 4, when the input voltage rises slowly from 0V, the input under-voltage circuit plays a role of low voltage and under-voltage, the EN circuit cannot work normally, the enable pin of the IC chip does not meet the voltage requirement, the chip does not work, the circuit does not output, and the function of input under-voltage blocking is achieved; when the input voltage supplied by the high-voltage battery to the input starting circuit slowly rises from 0V, the gate voltage Vg of the field effect transistor T4 in the input starting circuit 40 rises to reach the gate threshold voltage Vgsth of the field effect transistor T4, at this time, the field effect transistor T4 is in a variable resistance region, the second capacitor C2 starts to charge, Vg and Vs of the field effect transistor T4 both rise continuously, and Vgs becomes Vg-Vs; when Vgs > -Vgsth the fet T4 increases with Vgs, Id charges C2 through fet T4, which increases Vs further, causing Vgs to decrease, and Id to decrease (as can be seen from fig. 6), thus forming a negative feedback mechanism similar to voltage control, so that Vgs Vg-Vs ═ Vgsth can be maintained at all times; at the moment, T1, T2 and T3 are in an open state; wherein the voltage regulator D5 is used to protect the fet T4.
2) As shown in fig. 5, the input voltage continues to rise, so that the fifth regulator tube D5 breaks down, the Vg voltage is clamped, and when the input voltage continues to rise, the Vg voltage is maintained constant, and the voltage according to the analysis Vs is also constant; at the moment, T1, T2 and T3 are still in an off state;
as long as the first voltage regulator D1 in the input undervoltage circuit 60 is not broken down, the first triode T1 is not turned on, the enable circuit 70 cannot work normally, the enable end EN of the control chip does not meet the voltage requirement, the control chip 30 does not work, the flyback converter circuit has no output, and the flyback converter 20 is in a low-voltage undervoltage blocking state all the time, so that the static power consumption is reduced.
3) Input undervoltage is not blocked: as shown in fig. 6, the input voltage continues to rise, so that the first regulator D1 breaks down, and the first transistor T1 has Vb-T1When the voltage is greater than 0.7V (reference value), the first transistor T1 is turned on (and before that, V of the second transistor T2 ise-T2、Vb-T3Voltage is equal and is higher than the breakdown voltage of the second regulator tube D2, but the anode of D2 is not in effect due to the disconnection of T1, D2); at this time, T1 is turned on, and T2 and T3 are turned off.
4) The enabling circuit functions: as shown in fig. 7, the first triodeT1 is turned on, the second voltage regulator D2 breaks down, and the V of the second triode T2b-T2Voltage clamped, Ve-T2The voltage being higher than Vb-T2When the second triode T2 is switched on, the third voltage regulator tube D3 is broken down, the enabling circuit operates, and the voltage of the EN pin at the enabling end of the control chip is clamped; at this time, T1, T2 are on, and T3 is off.
5) The control chip works: when the voltage of the Vin at the input end of the control chip reaches the requirement of starting voltage and the voltage of the EN pin at the enable end reaches the requirement, the control chip works normally and outputs PWM;
in the vehicle-mounted inverter, before the main circuit starts to work, the input starting circuit is acted, after the main circuit starts to work, the input starting circuit can be turned off, and the static loss of the circuit is reduced. Compared with a similar input starting circuit 40 containing a switching device, the input starting circuit is applied to a vehicle-mounted inverter, the highest temperature of the working environment of the input starting circuit 40 can reach 125 ℃, the switching device always works in the input starting circuit 40, the input starting circuit has no meaning when the circuit works normally, and loss exists on the contrary, so that the temperature of the device is further increased; for the input starting circuit 40, the efficiency of the whole flyback converter 20 circuit is reduced, and meanwhile, the temperature of the switching devices in the input starting circuit 40 rises after long-time operation, so that the switching devices are in thermal risk and are burnt out under the worst high-temperature condition.
6) The flyback converter 20 operates, the self-shutdown circuit functions: as shown in fig. 8, when the control chip normally operates, the main circuit of the flyback converter 20 starts to operate, the normal output Vo1 is established, the fourth regulator D4 breaks down, and the voltage of the third transistor T3 is divided by the resistor, so as to obtain the voltage Vb-T3When the voltage is more than 0.7V, T3 is turned on, the gate voltage Vg of the field effect transistor T4 is pulled to the ground, the field effect transistor T4 is turned off (the field effect transistor T4 only works in the starting process, the main circuit is turned off when in normal work, and the loss of the field effect transistor T4 is reducedReducing the thermal risk at high temperatures); the input power to the control chip and the subsequent power to the enable circuit are provided by the output Vo1 through the second diode D7.
The invention applies the auxiliary power supply of the flyback converter to the environment of low voltage and high voltage input. Compared with the conventional low-voltage auxiliary power supply, the limit of the input voltage range is improved, the input voltage can be reasonably controlled to carry out low-voltage under-voltage blocking, and the application occasions of the flyback converter circuit are widened. An enabling circuit and an input undervoltage circuit are added in the mode that the function of an enabling pin of a control chip is utilized to the maximum extent, and a low-voltage threshold can be reasonably designed to carry out low-voltage undervoltage blocking; when the low-voltage input is performed, the circuit is prevented from normally working in full load, the input current is large, the power consumption of the switch MOS tube is increased, and the thermal risk is increased at high temperature; through the undervoltage circuit, the minimum input voltage is reasonably set by the increased undervoltage blocking mechanism, and the static power consumption of the circuit and the power consumption increase and thermal risk of the switching MOS tube are avoided. Meanwhile, a relatively simple starting circuit is added on the basis of a conventional auxiliary power supply, so that the IC chip with low-voltage input can be applied to the environment with high-voltage input without risk without replacement; meanwhile, a self-turn-off circuit is added in the starting circuit for the MOS tube applied to the starting circuit, so that the MOS tube is automatically turned off after the circuit output is established, and the starting MOS tube is prevented from running for a long time when the circuit normally works, the loss is increased, and the thermal risk of a high-temperature working condition is increased.
The embodiments in the present description are described in a progressive manner, each embodiment focuses on differences from other embodiments, and the same and similar parts among the embodiments are referred to each other. For the system disclosed by the embodiment, the description is relatively simple because the system corresponds to the method disclosed by the embodiment, and the relevant points can be referred to the method part for description.
The above description is only for the purpose of describing the preferred embodiments of the present invention, and is not intended to limit the scope of the present invention, and any variations and modifications made by those skilled in the art based on the above disclosure are within the scope of the appended claims.
Claims (9)
1. The utility model provides a flyback converter's under-voltage starting circuit based on high-pressure input, high-voltage battery for flyback converter's under-voltage starting circuit based on high-pressure input provides input voltage, high-voltage battery provides the input source for flyback converter, flyback converter's under-voltage starting circuit based on high-pressure input provides control signal for flyback converter's control chip, a serial communication port, flyback converter's under-voltage starting circuit based on high-pressure input includes input starting circuit, input under-voltage circuit, enabling circuit and self-shutdown circuit, wherein:
the high-voltage battery provides input voltage for the control chip through the input starting circuit, the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit charges a second capacitor, so that the voltage on a first electrode of the second capacitor reaches and is kept on the input voltage of the control chip, the first electrode of the second capacitor is connected with the input end of the control chip and provides the input voltage for the control chip, and a second electrode of the second capacitor is grounded;
the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage, and controls the enabling circuit to be switched on after the power supply voltage of the high-voltage battery reaches the threshold voltage;
the enabling circuit is connected between an enabling end of the control chip and an input end of the control chip, and the input voltage provides enabling voltage for the control chip through the enabling circuit;
when the enabling circuit is disconnected, the control chip is forbidden to be used; when the enabling circuit is conducted, the control chip normally operates to provide a switching signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter;
the flyback converter starts to work, the output end of the flyback converter provides output voltage to the first electrode of the second capacitor, and the output voltage enables the voltage on the first electrode of the second capacitor to reach and be kept on the input voltage of the control chip;
the self-shutdown circuit shuts off the input startup circuit to cause the input startup circuit to stop charging the first electrode of the second capacitor.
2. The undervoltage start-up circuit of claim 1, wherein the input undervoltage circuit comprises a plurality of undervoltage divider resistors, a first voltage regulator, a first transistor, a fourth resistor, and a fifth resistor, wherein:
the undervoltage divider resistors are connected in series to form an undervoltage series circuit, one end of the undervoltage series circuit is connected with the high-voltage battery, and the other end of the undervoltage series circuit is connected with the cathode of the first voltage-regulator tube;
the anode of the first voltage-regulator tube is connected with one end of the fourth resistor and one end of the fifth resistor, and the other end of the fourth resistor is grounded;
the other end of the fifth resistor is connected with the base electrode of the first triode;
the emitter of the first triode is grounded, and the collector of the first triode is connected with the enabling circuit; the first triode is an NPN type triode.
3. The undervoltage start-up circuit of the flyback converter based on the high voltage input of claim 2, wherein the enable circuit comprises a sixth resistor, a seventh resistor, an eighth resistor, a second regulator, a third regulator, a first capacitor and a second triode, wherein:
the anode of the second voltage-regulator tube is connected with the collector of the first triode, and the cathode of the second voltage-regulator tube is connected with one end of the sixth resistor and one end of the seventh resistor;
the other end of the sixth resistor is connected with the first electrode of the second capacitor, and the other end of the seventh resistor is connected with the base electrode of the second triode;
an emitting electrode of the second triode is connected with a first electrode of the second capacitor, a collector electrode of the second triode is connected with one end of the eighth resistor, and the second triode is a PNP triode;
the other end of the eighth resistor is connected with the cathode of the third voltage-regulator tube and the first electrode of the first capacitor, and the anode of the third voltage-regulator tube and the second electrode of the first capacitor are both grounded.
4. The undervoltage start-up circuit of a flyback converter based on high-voltage input of claim 1, wherein the input start-up circuit comprises a plurality of start-up voltage-dividing resistors, a fifth voltage-stabilizing tube and a field-effect transistor, wherein:
the plurality of starting voltage-dividing resistors are connected in series to form a starting series circuit, one end of the starting series circuit is connected with the high-voltage battery, and the other end of the starting series circuit is connected with the grid electrode of the field effect transistor and the cathode of the fifth voltage-stabilizing tube;
the anode of the fifth voltage regulator tube is grounded, the drain of the field effect transistor is connected with the high-voltage battery, and the source of the field effect transistor is coupled to the first electrode of the second capacitor;
the field effect transistor is a P-channel field effect transistor.
5. The undervoltage start-up circuit of a high voltage input based flyback converter of claim 4, wherein the input start-up circuit further comprises a first diode, wherein:
the cathode of the first diode is connected with the second capacitor, and the anode of the first diode is connected with the source electrode of the field effect transistor.
6. The undervoltage start-up circuit of a flyback converter based on high-voltage input of claim 4, wherein the self-turn-off circuit comprises a fourth regulator tube, a ninth resistor, a tenth resistor and a third triode, wherein:
the cathode of the fourth voltage-regulator tube is connected with the output end of the flyback converter, the anode of the fourth voltage-regulator tube is connected with one end of the ninth resistor, the other end of the ninth resistor is connected with one end of the tenth resistor and the base electrode of the third triode, and the other end of the tenth resistor is grounded;
and the collector electrode of the third triode is connected with the grid electrode of the field effect transistor, the emitter electrode of the third triode is grounded, and the third triode is an NPN type triode.
7. The undervoltage start-up circuit of the high-voltage input based flyback converter of claim 1, wherein the undervoltage start-up circuit of the high-voltage input based flyback converter further comprises a second diode, a cathode of the second diode is connected to the first electrode of the second capacitor, and an anode of the second diode is connected to the output terminal of the flyback converter.
8. The undervoltage start-up circuit of a high-voltage input based flyback converter according to claim 1, wherein a supply voltage of the high-voltage battery is greater than 60V.
9. An under-voltage starting method of a flyback converter based on high-voltage input, which is characterized in that, based on the under-voltage starting circuit of the flyback converter based on high-voltage input of any one of claims 1 to 8, the under-voltage starting method of the flyback converter based on high-voltage input comprises the following steps:
the high-voltage battery provides input voltage for an under-voltage starting circuit of the flyback converter based on high-voltage input, the high-voltage battery provides an input source for the flyback converter, and the under-voltage starting circuit of the flyback converter based on the high-voltage input provides a control signal for a control chip of the flyback converter;
the high-voltage battery provides input voltage for a control chip through an input starting circuit of an undervoltage starting circuit of a flyback converter based on high-voltage input, the input voltage is lower than the output voltage of the high-voltage battery, the input starting circuit charges a second capacitor, so that the voltage on a first electrode of the second capacitor reaches and is kept on the input voltage of the control chip, the first electrode of the second capacitor is connected with the input end of the control chip and provides the input voltage for the control chip, and a second electrode of the second capacitor is grounded;
the input undervoltage circuit controls the enabling circuit to be switched off before the power supply voltage of the high-voltage battery reaches the threshold voltage, and controls the enabling circuit to be switched on after the power supply voltage of the high-voltage battery reaches the threshold voltage;
the enabling circuit is connected between an enabling end of the control chip and an input end of the control chip, and the input voltage provides enabling voltage for the control chip through the enabling circuit;
when the enabling circuit is disconnected, the control chip is forbidden to be used; when the enabling circuit is conducted, the control chip normally operates to provide a switching signal for a switching MOS (metal oxide semiconductor) tube of the flyback converter;
the flyback converter starts to work, the output end of the flyback converter provides output voltage to the first electrode of the second capacitor, and the output voltage enables the voltage on the first electrode of the second capacitor to reach and be kept on the input voltage of the control chip;
the self-shutdown circuit shuts off the input startup circuit to cause the input startup circuit to stop charging the first electrode of the second capacitor.
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| US8064227B2 (en) * | 2008-09-08 | 2011-11-22 | GM Global Technology Operations LLC | Rectifying circuit for a multiphase electric machine |
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| CN103683982A (en) * | 2014-01-03 | 2014-03-26 | 哈尔滨工业大学 | Wide-range alternating voltage input Buck structure voltage-stabilized source |
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