Flyback switching circuit
By introducing a half-wave rectifying filter circuit into the flyback switch circuit, the reverse voltage spike is absorbed and the EMI signal jitter control is performed, the problem of high auxiliary power loss in the prior art is solved, and the effect of stabilizing the output voltage and reducing the switching loss is achieved.
Patent Information
- Application Number
- CN202422155566.3
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- Filing Date
- 2024-09-03
- Publication Date
- 2025-06-27
- Estimated Expiration
- 2034-09-03
AI Technical Summary
The existing flyback switch circuit adds EMI filtering components to the auxiliary power supply part, resulting in an increase in the auxiliary power supply loss.
A flyback switching circuit is designed to absorb the reverse voltage spike through a half-wave rectifier filter circuit, and the switching power supply chip is jittered according to the EMI signal to reduce switching losses and current spikes.
A stable output voltage is achieved, reducing switching losses and current spikes during light or no-loads, reducing the loss of auxiliary power supplies without additional EMI filtering devices.
Smart Images
Figure CN223039908U_ABST
Abstract
Description
Technical Field
[0001] The utility model belongs to the technical field of flyback switching circuits, and particularly relates to a flyback switching circuit. Background Art
[0002] The flyback switching circuit is also called a single-ended flyback or buck-boost converter, and its output voltage can be higher or lower than the supply voltage. In the existing flyback switching circuits, EMI filtering components are mostly added to the auxiliary power supply part, resulting in losses in the auxiliary power supply.
[0003] Therefore, it is necessary to invent a flyback switching circuit to solve the above problems. Content of the Utility Model
[0004] In view of the above problems, the utility model provides a flyback switching circuit to solve the problems put forward in the above background art.
[0005] To achieve the above purpose, the utility model provides the following technical solution: A flyback switching circuit includes a transformer T1 and a switching power supply chip U2. The primary side of the transformer T1 is connected to a rectified voltage. A diode D6 and a diode D7 are connected in parallel to the primary side of the transformer T1. The rectified voltage supplies power to the switching power supply chip U2. The pin 7 of the secondary side of the transformer T1 is connected to the pin 6 of the switching power supply chip U2 through a diode D9 and a resistor R36. The pin 7 of the secondary side of the transformer T1 is also connected to the pin 5 of the switching power supply chip U2 through a resistor R37. The pin 7 of the secondary side of the transformer T1 outputs a supply voltage of 15V through a diode D3 and a resistor R6, and the pin 9 of the secondary side of the transformer T1 is grounded. The pin 8 of the secondary side of the transformer T1 outputs a supply voltage of 5V through a diode D8 and a resistor R8.
[0006] Further, the pin 6 of the switching power supply chip U2 is grounded through a capacitor C36, and the pin 5 of the switching power supply chip U2 is grounded through a capacitor C38.
[0007] Further, a diode D4 is connected in parallel to the diode D3, and a capacitor C11, a capacitor C14, and a resistor R7 are also connected in parallel to the diode D3. The diode D3 and the diode D4 in parallel and the capacitor C11, the capacitor C14, and the resistor R7 form a half-wave rectification and filtering circuit.
[0008] Further, the pin 8 of the secondary side of the transformer T1 is grounded through a diode D8 and a capacitor C31.
[0009] Further, the pin 8 of the secondary side of the transformer T1 is grounded through a diode D8 and a capacitor C32.
[0010] Further, the pins 1, 2, and 3 of the switching power supply chip U2 are grounded.
[0011] Further, pin 4 of the switching power supply chip U2 is grounded through resistor R40.
[0012] Technical effects and advantages of the present utility model:
[0013] 1. The present utility model absorbs reverse voltage spikes through a half-wave rectification and filtering circuit, and performs frequency dithering control on the switching power supply chip U2 according to the EMI signal, which facilitates the stable output voltage of the entire circuit, reduces switching losses and current spikes under light load or even no load, reduces the loss of the auxiliary power supply, and eliminates the need to provide additional EMI filtering devices for the auxiliary power supply. Description of the drawings
[0014] Figure 1 is the flyback switching circuit diagram of the embodiment of the present utility model. Detailed implementation manners
[0015] To make the objectives, technical solutions, and advantages of the embodiments of the present utility model clearer, the technical solutions of the present utility model will be clearly and completely described below in conjunction with the embodiments.
[0016] The present utility model provides a flyback switching circuit, as Figure 1 shown, which includes a transformer T1 and a switching power supply chip U2. The primary side of the transformer T1 is connected to a rectified voltage. A diode D6 and a diode D7 are connected in parallel to the primary side of the transformer T1, and the diodes D6 and D7 are connected in parallel to the primary side of the transformer T1 to absorb high-voltage spikes generated due to the leakage inductance of the primary side of the transformer T1. The rectified voltage powers the switching power supply chip U2. Pin 7 of the secondary side of the transformer T1 is connected to pin 6 of the switching power supply chip U2 through a diode D9 and a resistor R36. Pin 7 of the secondary side of the transformer T1 is also connected to pin 5 of the switching power supply chip U2 through a resistor R37. Pin 7 of the secondary side of the transformer T1 outputs a supply voltage of 15V through a diode D3 and a resistor R6, and pin 9 of the secondary side of the transformer T1 is grounded. Pin 8 of the secondary side of the transformer T1 outputs a supply voltage of 5V through a diode D8 and a resistor R8. When the inside of the switching power supply chip U2 conducts, pin 2 of the transformer T1 is the primary side, and pin 4 of the transformer T1 becomes the secondary side. At this time, the diodes D3, D8, and D9 do not conduct. When the inside of the switching power supply chip U2 does not conduct, there is a back electromotive force on pins 2 and 4 of the primary side of the transformer T1 that needs to be released. At this time, the diodes D3, D8, and D9 conduct.
[0017] Pin 6 of the switching power supply chip U2 is grounded through a capacitor C36, and pin 5 of the switching power supply chip U2 is grounded through a capacitor C38.
[0018] In Figure 1In it, a diode D4 is connected in parallel with the diode D3, and the diode D3 is also juxtaposed with a capacitor C11, a capacitor C14, and a resistor R7. After the diodes D3 and D4 are connected in parallel, they form a half-wave rectifier filter circuit with the capacitor C11, the capacitor C14, and the resistor R7. The parallel connection of the diodes D3 and D4 is for current expansion and heat dissipation, and the half-wave rectifier filter circuit is for absorbing reverse voltage spikes, performing frequency jitter control on the switching power supply chip U2 according to the EMI signal, facilitating the stable output voltage of the entire circuit, and reducing the switching loss and current spikes under light load or even no load.
[0019] Among them, the pin 8 of the secondary side of the transformer T1 is grounded through the diode D8 and the capacitor C31. The pin 8 of the secondary side of the transformer T1 is grounded through the diode D8 and the capacitor C32.
[0020] The pins 1, 2, and 3 of the switching power supply chip U2 are grounded. The pin 4 of the switching power supply chip U2 is grounded through the resistor R40. The flyback power supply of the switching power supply chip U2 provides an auxiliary power supply, providing 100 mA of current for the 15V power supply line and 300 mA of current for the 5V power supply. The loss of the auxiliary power supply is reduced, and no additional EMI filtering devices are required for the auxiliary power supply.
[0021] The working principle of the present invention:
[0022] Refer to Figure 1 As shown, when the inside of the switching power supply chip U2 conducts, the pin 2 of the transformer T1 is the primary side, and the pin 4 of the transformer T1 becomes the secondary side. At this time, the diodes D3, D8, and D9 are not conducting. When the inside of the switching power supply chip U2 does not conduct, there is a back electromotive force on the pins 2 and 4 of the primary side of the transformer T1 that needs to be released. At this time, the diodes D3, D8, and D9 conduct.
[0023] The parallel connection of the diodes D3 and D4 is for current expansion and heat dissipation, and the half-wave rectifier filter circuit is for absorbing reverse voltage spikes, performing frequency jitter control on the switching power supply chip U2 according to the EMI signal, facilitating the stable output voltage of the entire circuit, and reducing the switching loss and current spikes under light load or even no load.
[0024] The above embodiments are only used to illustrate the technical solutions of the present invention, rather than to limit it.
Claims
1. A flyback switching circuit, characterized in that: It includes a transformer T1 and a switching power supply chip U2, the primary side of the transformer T1 is connected to the rectified voltage, the primary side of the transformer T1 is connected in parallel with a diode D6 and a diode D7, the rectified voltage supplies energy to the switching power supply chip U2, the pin 7 of the secondary side of the transformer T1 is connected to the pin 6 of the switching power supply chip U2 through a diode D9 and a resistor R36, the pin 7 of the secondary side of the transformer T1 is also connected to the pin 5 of the switching power supply chip U2 through a resistor R37, the pin 7 of the secondary side of the transformer T1 outputs a power supply voltage of 15V through a diode D3 and a resistor R6, and the pin 9 of the secondary side of the transformer T1 is grounded, and the pin 8 of the secondary side of the transformer T1 outputs a power supply voltage of 5V through a diode D8 and a resistor R8.
2. The flyback switching circuit according to claim 1, characterized in that: Pin 6 of the switching power supply chip U2 is grounded via capacitor C36, and pin 5 of the switching power supply chip U2 is grounded via capacitor C38.
3. The flyback switching circuit according to claim 1, wherein: The diode D3 is connected in parallel with the diode D4, and the diode D3 is also connected in parallel with the capacitor C11, the capacitor C14 and the resistor R7. The diode D3 and the diode D4 are connected in parallel to form a half-wave rectification and filtering circuit with the capacitor C11, the capacitor C14 and the resistor R7.
4. The flyback switching circuit according to claim 1, wherein: Pin 8 of the secondary side of the transformer T1 is grounded via a diode D8 and a capacitor C31.
5. The flyback switching circuit according to claim 4, characterized in that: Pin 8 of the secondary side of the transformer T1 is grounded via a diode D8 and a capacitor C32.
6. The flyback switching circuit according to claim 1, characterized in that: Pin 1, pin 2 and pin 3 of the switching power supply chip U2 are grounded.
7. The flyback switching circuit according to claim 6, characterized in that: Pin 4 of the switching power supply chip U2 is grounded via a resistor R40.