Flyback constant-voltage constant-current power supply

Abstract

The flyback constant-voltage and constant-current power supply provided by the utility model has constant-voltage and constant-current feedback and is prevented from being damaged. The circuit comprises a primary side driving circuit which converts high-voltage direct current into pulsating alternating current, a secondary side rectifying and filtering circuit which converts the pulsating alternating current into direct current and outputs the direct current to the outside, and a voltage and current feedback circuit which feeds back output voltage and current signals to a primary side driving chip so as to adjust output voltage and current. The primary side driving circuit comprises a driving MOS tube, the driving MOS tube converts high-voltage direct current into magnetic energy and stores the magnetic energy in a transformer, the secondary side rectifying and filtering circuit converts the magnetic energy into electric energy to supply power to a load, and the voltage and current feedback circuit monitors and outputs voltage and current signals in real time. And the signal is fed back to the primary side driving circuit through an optocoupler, and the primary side driving circuit dynamically adjusts the output voltage and current. The utility model can be applied to the technical field of power supplies.

Description

Technical Field

[0001] The utility model relates to the technical field of power supplies, in particular to a flyback constant voltage and constant current power supply. Background Art

[0002] With the continuous development of switching power supplies, flyback switching power supplies are widely used in various power supply devices due to their advantages of small size and low cost. At present, most flyback switching power supplies can only output a constant voltage, resulting in an increase in the maximum output current with the increase of the input voltage. When the load current is too large, it is easy to cause damage to the power supply. Therefore, it is necessary to design a new flyback switching power supply with constant voltage and constant current feedback to prevent overcurrent damage to the power supply. Summary of the Utility Model

[0003] The technical problem to be solved by the utility model is to overcome the deficiencies of the prior art and provide a flyback constant voltage and constant current power supply with constant voltage and constant current feedback to avoid damage.

[0004] The technical solution adopted by the utility model is that it includes

[0005] a primary drive circuit that converts high-voltage direct current into pulsating alternating current,

[0006] a secondary rectification and filtering circuit that converts pulsating alternating current into direct current for external output, and

[0007] a voltage and current feedback circuit that feeds back the output voltage and current signals to the primary drive chip to adjust the output voltage and current.

[0008] The primary drive circuit includes a driving MOS transistor. The driving MOS transistor converts high-voltage direct current into magnetic energy and stores it in a transformer. The secondary rectification and filtering circuit converts the magnetic energy into electrical energy to supply power to a load. The voltage and current feedback circuit monitors the output voltage and current signals in real time and feeds back the signals to the primary drive circuit through an optocoupler. The primary drive circuit dynamically adjusts the output voltage and current.

[0009] Further, the primary side drive circuit includes a first power management chip, a first capacitor, a second capacitor, a third capacitor, a fourth capacitor, a fifth capacitor, a sixth capacitor, a first resistor, a second resistor, a third resistor, a fourth resistor, a fifth resistor, a first diode, a second diode, and an optocoupler receiving end. Among them, the third capacitor is an input filter capacitor, and the fifth capacitor, the fifth resistor, and the first diode form an RCD absorption circuit. The RCD absorption circuit absorbs the D-pole voltage spike when the driving MOS transistor is turned off. The fourth resistor is a primary side current sampling resistor, the third resistor is a slope compensation resistor, the fourth capacitor is a filter capacitor for primary side current sampling, the first resistor is a frequency hopping setting resistor, and the amplitude for entering the frequency hopping mode is set by adjusting the resistance value of the first resistor. The first capacitor is a frequency hopping filter capacitor, the second capacitor is a filter capacitor for the optocoupler, the second diode is a rectifier diode for the power supply winding of the first power management chip, and the sixth capacitor is a storage filter capacitor for power supply to the first power management chip.

[0010] Still further, the secondary side rectification and filtering circuit includes a sixth resistor, an eighth resistor, a seventh capacitor, an eighth capacitor, a ninth capacitor, a tenth capacitor, and a third diode. Among them, the sixth resistor and the seventh capacitor form an RC absorption circuit to absorb the voltage spike across the third diode. The eighth capacitor, the ninth capacitor, and the tenth capacitor form a filter and energy storage circuit for filtering high-frequency ripple voltage. The eighth resistor is a dummy load resistor to ensure the stability of the output voltage under no-load conditions.

[0011] Furthermore, the voltage and current feedback circuit includes a second power management chip, a seventh resistor, a ninth resistor, a tenth resistor, a twelfth resistor, a thirteenth resistor, a fourteenth resistor, a fifteenth resistor, an eleventh capacitor, a twelfth capacitor, and an optocoupler transmitting end. Among them, the ninth resistor and the tenth resistor form a voltage division circuit for collecting the output voltage. The seventh resistor is an output current sampling resistor for collecting the output current. The eleventh capacitor and the twelfth resistor form a voltage feedback compensation network to improve the stability of the output voltage feedback circuit. The twelfth capacitor and the thirteenth resistor form a current feedback compensation network to improve the stability of the output current feedback circuit. The fourteenth resistor is a current limiting resistor for output current detection, and the fifteenth resistor is a current limiting resistor for the optocoupler transmitting end. In the voltage and current feedback circuit, the magnitude of the output voltage is adjusted by adjusting the resistance values of the ninth resistor and the tenth resistor, and the maximum value of the output current is adjusted by adjusting the resistance value of the seventh resistor.

[0012] In addition, the first power management chip uses a power management chip with the model number NCP1271D65R2G.

[0013] In addition, the second power management chip adopts a power management chip with the model number SEA05LTR.

[0014] The beneficial effects of the present utility model are as follows: In the present utility model, when the load current instantaneously increases (within the maximum output current range), the output voltage drops, the voltage across the tenth resistor drops, the voltage of the VCTRL pin of the second power management chip drops, the output voltage of the OUT pin of the second power management chip rises, the voltage difference across the light-emitting end of the optocoupler decreases, and the current I flowing through the light-emitting end of the optocoupler F decreases, the light intensity emitted by the light-emitting end of the optocoupler weakens, resulting in a decrease in the current I flowing through the light-receiving end of the optocoupler C decreases, the voltage of the FB pin of the first power management chip starts to rise, which causes the PWM duty cycle output by the DRV pin of the first power management chip to increase, the current of the secondary side of the transformer increases, and the output voltage rises. Conversely, when the load current drops, the output voltage rises, the voltage of the FB pin of the first power management chip drops, resulting in a decrease in the PWM duty cycle output by the DRV pin of the first power management chip, a decrease in the current of the secondary side of the transformer, and a drop in the output voltage; when the load current is the maximum output current, if the load current increases further at this time, the voltage across the seventh resistor (current sensing resistor) rises, the voltage of the ISENSE pin of the second power management chip rises, the output voltage of the OUT pin of the second power management chip drops, the voltage difference across the light-emitting end of the optocoupler increases, and the current I flowing through the light-emitting end of the optocoupler F increases, the current I flowing through the light-receiving end of the optocoupler C increases, the voltage of the FB pin of the first power management chip starts to drop, which causes the PWM duty cycle output by the DRV pin of the first power management chip to decrease, the current of the secondary side of the transformer to decrease, and the load current to drop, thereby maintaining a constant current output and further ensuring the safety and reliability of the power supply. Description of the Drawings

[0015] Figure 1 is the circuit schematic diagram of the primary side drive circuit and the secondary side rectification and filtering circuit;

[0016] Figure 2 is the circuit schematic diagram of the voltage and current feedback circuit. Detailed Embodiments

[0017] As Figure 1 and Figure 2 shown, the present utility model includes

[0018] a primary side drive circuit that converts high-voltage direct current into pulsating alternating current,

[0019] a secondary side rectification and filtering circuit that converts pulsating alternating current into direct current for external output, and

[0020] The output voltage and current signals are fed back to the primary side drive chip, thereby adjusting the voltage and current feedback circuit of the output voltage and current.

[0021] The primary side drive circuit includes a driving MOS transistor Q1. The driving MOS transistor Q1 converts high-voltage direct current into magnetic energy and stores it in a transformer. The secondary side rectifying and filtering circuit converts the magnetic energy into electrical energy to supply power to a load. The voltage and current feedback circuit monitors the output voltage and current signals in real time and feeds the signals back to the primary side drive circuit through an optocoupler. The primary side drive circuit dynamically adjusts the output voltage and current.

[0022] The primary side drive circuit includes a first power management chip IC1, a first capacitor C1, a second capacitor C2, a third capacitor C3, a fourth capacitor C4, a fifth capacitor C5, a sixth capacitor C6, a first resistor R1, a second resistor R2, a third resistor R3, a fourth resistor R4, a fifth resistor R5, a first diode D1, a second diode D2, and an optocoupler receiving end U1-B. The first power management chip IC1 uses a power management chip with the model number NCP1271D65R2G. Among them, the third capacitor C3 is an input filter capacitor. The fifth capacitor C5, the fifth resistor R5, and the first diode D1 form an RCD absorption circuit. The RCD absorption circuit absorbs the D-pole voltage spike when the driving MOS transistor Q1 turns off. The fourth resistor R4 is a primary side current sampling resistor. The third resistor R3 is a slope compensation resistor. The fourth capacitor C4 is a filter capacitor for primary side current sampling. The first resistor R1 is a hopping frequency setting resistor. By adjusting the resistance value of the first resistor R1, the amplitude for entering the hopping frequency mode is set. The first capacitor C1 is a hopping frequency filter capacitor. The second capacitor C2 is a filter capacitor for the optocoupler. The second diode D2 is a rectifying diode for the power supply winding of the first power management chip IC1. The sixth capacitor C6 is an energy storage filter capacitor for the power supply of the first power management chip IC1.

[0023] The secondary side rectifying and filtering circuit includes a sixth resistor R6, an eighth resistor R8, a seventh capacitor C7, an eighth capacitor C8, a ninth capacitor C9, a tenth capacitor C10, and a third diode D3. Among them, the sixth resistor R6 and the seventh capacitor C7 form an RC absorption circuit to absorb the voltage spike across the third diode D3. The eighth capacitor C8, the ninth capacitor C9, and the tenth capacitor C10 form a filtering and energy storage circuit for filtering high-frequency ripple voltage. The eighth resistor R8 is a dummy load resistor to ensure the stability of the output voltage under no-load conditions.

[0024] The voltage and current feedback circuit includes a second power management chip IC2, a seventh resistor R7, a ninth resistor R9, a tenth resistor R10, a twelfth resistor R12, a thirteenth resistor R13, a fourteenth resistor R14, a fifteenth resistor R15, an eleventh capacitor C11, a twelfth capacitor C12, and an optocoupler emitter U1-A. The second power management chip IC2 uses a power management chip with the model number SEA05LTR. Among them, the ninth resistor R9 and the tenth resistor R10 form a voltage division circuit for collecting the output voltage. The seventh resistor R7 is an output current sampling resistor for collecting the output current. The eleventh capacitor C11 and the twelfth resistor R12 form a voltage feedback compensation network for improving the stability of the output voltage feedback circuit. The twelfth capacitor C12 and the thirteenth resistor R13 form a current feedback compensation network for improving the stability of the output current feedback circuit. The fourteenth resistor R14 is a current-limiting resistor for output current detection, and the fifteenth resistor R15 is a current-limiting resistor for the optocoupler emitter U1-A. In the voltage and current feedback circuit, the magnitude of the output voltage is adjusted by adjusting the resistance values of the ninth resistor R9 and the tenth resistor R10, and its calculation formula is Vo = 2.5 * (R9 + R10) / R10; the maximum value of the output current is adjusted by adjusting the resistance value of the seventh resistor R7, and its calculation formula is Io(max) = 0.05 / R7.

[0025] The working process of the present utility model is as follows:

[0026] The constant voltage feedback regulation process is as follows: When the load current instantaneously increases (within the maximum output current range), the output voltage drops, the voltage across the tenth resistor R10 drops, the voltage at the VCTRL pin of the second power management chip IC2 drops, the output voltage at the OUT pin of the second power management chip IC2 rises, the voltage difference across the optocoupler emitter U1-A decreases, and the current I flowing through the optocoupler emitter U1-A F decreases, the light intensity emitted by the optocoupler emitter U1-A weakens, resulting in a decrease in the current I flowing through the optocoupler receiver U1-B C decreases, the voltage at the FB pin of the first power management chip IC1 starts to rise, which causes the PWM duty cycle output at the DRV pin of the first power management chip IC1 to increase, the current in the secondary side of the transformer T1 increases, and the output voltage rises. Conversely, when the load current drops, the output voltage rises, the voltage at the FB pin of the first power management chip IC1 drops, causing the PWM duty cycle output at the DRV pin of the first power management chip IC1 to decrease, the current in the secondary side of the transformer T1 decreases, and the output voltage drops.

[0027] The constant current feedback regulation process is as follows: When the load current is the maximum output current, if the load current increases further, the voltage across the seventh resistor R7 (current sensing resistor) rises, the voltage at the ISENSE pin of the second power management chip IC2 rises, the output voltage at the OUT pin of the second power management chip IC2 drops, the voltage difference across the emitting end U1-A of the optocoupler increases, and the current I F flowing through the emitting end U1-A of the optocoupler increases, and the current I C flowing through the receiving end U1-B of the optocoupler increases. The voltage at the FB pin of the first power management chip IC1 starts to drop, resulting in a decrease in the PWM duty cycle output at the DRV pin of the first power management chip IC1, a decrease in the current in the secondary side of the transformer T1, and a decrease in the load current, thereby maintaining a constant current output and ensuring the safety and reliability of the power supply.

[0028] In this utility model, the primary side drive circuit drives the MOS transistor to convert the high-voltage direct current into magnetic energy and store it in the transformer. The secondary side rectification and filtering circuit converts the magnetic energy into electrical energy to supply power to the load. The voltage and current feedback circuit monitors the output voltage and current signals in real time and feeds the signals back to the primary side drive circuit through the optocoupler, thereby dynamically regulating the output voltage and current.

[0029] Finally, it should be emphasized that the above are only the preferred embodiments of this utility model and are not used to limit this utility model. For those skilled in the art, this utility model can have various changes and modifications. Any modifications, equivalent replacements, improvements, etc. made within the spirit and principle of this utility model shall be included within the protection scope of this utility model.

Claims

1. A flyback constant voltage and constant current power supply, which comprises a primary drive circuit that converts high-voltage direct current into pulsating alternating current, a secondary rectification and filtering circuit that converts the pulsating alternating current into direct current for external output, and a voltage and current feedback circuit that feeds back the output voltage and current signals to the primary drive chip to adjust the output voltage and current. It is characterized in that the primary drive circuit includes a driving MOS transistor (Q1). The driving MOS transistor (Q1) converts the high-voltage direct current into magnetic energy and stores it in the transformer. The secondary rectification and filtering circuit converts the magnetic energy into electrical energy to supply power to the load. The voltage and current feedback circuit monitors the output voltage and current signals in real time and feeds the signals back to the primary drive circuit through an optocoupler. The primary drive circuit dynamically adjusts the output voltage and current.

2. The flyback constant voltage and constant current power supply according to claim 1, characterized in that The primary drive circuit includes a first power management chip (IC1), a first capacitor (C1), a second capacitor (C2), a third capacitor (C3), a fourth capacitor (C4), a fifth capacitor (C5), a sixth capacitor (C6), a first resistor (R1), a second resistor (R2), a third resistor (R3), a fourth resistor (R4), a fifth resistor (R5), a first diode (D1), a second diode (D2), and an optocoupler receiving end (U1-B). Among them, the third capacitor (C3) is an input filtering capacitor. The fifth capacitor (C5), the fifth resistor (R5), and the first diode (D1) form an RCD absorption circuit. The RCD absorption circuit absorbs the D-pole voltage spike when the driving MOS transistor (Q1) turns off. The fourth resistor (R4) is a primary current sampling resistor. The third resistor (R3) is a slope compensation resistor. The fourth capacitor (C4) is a filtering capacitor for primary current sampling. The first resistor (R1) is a hopping frequency setting resistor. By adjusting the resistance value of the first resistor (R1), the amplitude for entering the hopping frequency mode is set. The first capacitor (C1) is a hopping frequency filtering capacitor. The second capacitor (C2) is a filtering capacitor for the optocoupler. The second diode (D2) is a rectifying diode for the power supply winding of the first power management chip (IC1). The sixth capacitor (C6) is an energy storage filtering capacitor for the power supply of the first power management chip (IC1).

3. The flyback constant voltage and constant current power supply according to claim 1, characterized in that, The secondary rectification and filtering circuit includes a sixth resistor (R6), an eighth resistor (R8), a seventh capacitor (C7), an eighth capacitor (C8), a ninth capacitor (C9), a tenth capacitor (C10), and a third diode (D3). Among them, the sixth resistor (R6) and the seventh capacitor (C7) form an RC absorption circuit to absorb the voltage spike across the third diode (D3). The eighth capacitor (C8), the ninth capacitor (C9), and the tenth capacitor (C10) form a filtering and energy storage circuit for filtering high-frequency ripple voltage. The eighth resistor (R8) is a dummy load resistor to ensure the stability of the output voltage under no-load conditions.

4. The flyback constant voltage and constant current power supply according to claim 2, wherein, The voltage and current feedback circuit includes a second power management chip (IC2), a seventh resistor (R7), a ninth resistor (R9), a tenth resistor (R10), a twelfth resistor (R12), a thirteenth resistor (R13), a fourteenth resistor (R14), a fifteenth resistor (R15), an eleventh capacitor (C11), a twelfth capacitor (C12), and an optocoupler emitter (U1-A). Among them, the ninth resistor (R9) and the tenth resistor (R10) form a voltage division circuit for collecting the output voltage. The seventh resistor (R7) is an output current sampling resistor for collecting the output current. The eleventh capacitor (C11) and the twelfth resistor (R12) form a voltage feedback compensation network for improving the stability of the output voltage feedback circuit. The twelfth capacitor (C12) and the thirteenth resistor (R13) form a current feedback compensation network for improving the stability of the output current feedback circuit. The fourteenth resistor (R14) is a current-limiting resistor for output current detection, and the fifteenth resistor (R15) is a current-limiting resistor for the optocoupler emitter (U1-A). In the voltage and current feedback circuit, the magnitude of the output voltage is adjusted by adjusting the resistance values of the ninth resistor (R9) and the tenth resistor (R10), and the maximum value of the output current is adjusted by adjusting the resistance value of the seventh resistor (R7).

5. The flyback constant voltage and constant current power supply according to claim 2, characterized in that, The first power management chip (IC1) uses a power management chip of model NCP1271D65R2G.

6. The flyback constant voltage and constant current power supply according to claim 4, wherein, The second power management chip (IC2) uses a power management chip of model SEA05LTR.

Images