CN216351141U - Micromodule flyback switching power supply overcurrent detection circuit - Google Patents
Micromodule flyback switching power supply overcurrent detection circuit Download PDFInfo
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- CN216351141U CN216351141U CN202122722725.XU CN202122722725U CN216351141U CN 216351141 U CN216351141 U CN 216351141U CN 202122722725 U CN202122722725 U CN 202122722725U CN 216351141 U CN216351141 U CN 216351141U
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Abstract
The utility model discloses an overcurrent detection circuit of a micro-module flyback switching power supply in the technical field of current detection, which comprises a current transformer unit, a forward protection circuit, a sampling current conversion circuit and a signal input circuit, wherein the current transformer unit, the forward protection circuit, the sampling current conversion circuit and the signal input circuit are sequentially and electrically connected; the current transformer unit is electrically connected with a drain electrode of a primary side switching tube of the flyback switching power supply; the signal input circuit is electrically connected with the flyback switching power supply controller; and the flyback switching power supply controller is electrically connected with the grid electrode of the primary side switching tube of the flyback switching power supply. The utility model can greatly reduce the power loss of the over-current detection circuit, improve the conversion efficiency of the secondary isolation power supply of the microminiature module and increase the power density of the microminiature module.
Description
Technical Field
The utility model belongs to the technical field of current detection, and particularly relates to a micro-module flyback switching power supply overcurrent detection circuit.
Background
The flyback switching power supply has the advantages of simple circuit and small size. At present, a flyback topology structure is basically adopted for a low-power isolated power supply within 100W. The power supply is widely applied to low-power mobile charging equipment, high-power equipment auxiliary power supplies, DC-DC isolation module power supplies and the like. In the prior art, a primary switching tube drain electrode series current detection resistance method is adopted to convert a current signal into a voltage signal for detecting the magnitude of current. The method is simple and reliable, and the voltage value of the primary current on the resistor is directly sampled. However, the resistor still has power loss, and perhaps compared with a power supply with power of more than 20W, the loss is very small and can be ignored, but for some miniature module secondary isolation power supplies applied to special equipment, the input voltage is generally small (such as 9V-36V), the primary side current of the flyback power supply is relatively large, the internal reference voltage of a general controller is generally more than 0.6V, so that the power consumption on the current detection resistor may be more than 1W, and the large loss accounts for more than 10% or 20% of the total power consumption, which is unable to meet the requirement of high power density for the miniature module secondary isolation power supplies.
SUMMERY OF THE UTILITY MODEL
In order to overcome the defects in the prior art, the utility model provides the micro-module flyback switching power supply overcurrent detection circuit which can greatly reduce the power loss of the overcurrent detection circuit, improve the conversion efficiency of the micro-module secondary isolation power supply and increase the power density of the micro-module secondary isolation power supply.
In order to achieve the purpose, the technical scheme adopted by the utility model is as follows: an overcurrent detection circuit of a micro-module flyback switching power supply comprises a current transformer unit, a forward protection circuit, a sampling current conversion circuit and a signal input circuit which are electrically connected in sequence; the current transformer unit is electrically connected with a drain electrode of a primary side switching tube of the flyback switching power supply; the signal input circuit is electrically connected with the flyback switching power supply controller; and the flyback switching power supply controller is electrically connected with the grid electrode of the primary side switching tube of the flyback switching power supply.
Further, the current transformer unit, the forward protection circuit and the sampling current conversion circuit are connected to the ground in common.
Furthermore, the current transformer unit comprises a current transformer CT, a primary coil current input end of the current transformer CT is electrically connected with a drain electrode of a primary switch tube of the flyback switching power supply, and a primary coil current output end of the current transformer CT is connected with a primary power ground; and a secondary side coil of the current transformer CT is electrically connected with the forward protection circuit.
Further, the forward protection circuit comprises a resistor R1 and a diode D, a secondary coil equivalent current input end of the current transformer CT is connected with a first end of the resistor R1 and a positive end of the diode, and a secondary coil equivalent current output end of the current transformer CT is connected with a second end of the resistor R1; the cathode end of the diode D and the second end of the resistor R1 are connected with the sampling current conversion circuit.
Further, the sampling current conversion circuit comprises a resistor R2, wherein a first end of the resistor R2 is connected with the negative terminal of the diode D; the second end of the resistor R2 is connected with the second end of the resistor R1; a first terminal of the resistor R2 is connected to the signal input circuit.
Further, the signal input circuit comprises an input resistor R3 and a pull-up resistor R4, a first end of the input resistor R3 is connected with a first end of the resistor R2, and a second end of the input resistor R3 is connected with a second section of the pull-up resistor R4 and is connected with an over-current detection pin end of the flyback switching power supply controller; a first end of the pull-up resistor R4 is connected to the input voltage positive electrode Vin of the flyback switching power supply.
Compared with the prior art, the utility model has the following beneficial effects: the utility model is characterized in that a current transformer CT, a forward protection circuit, a sampling current conversion circuit and a signal input circuit are electrically connected in sequence; the current transformer CT is electrically connected with the drain electrode of the primary side switching tube of the flyback switching power supply; the signal input circuit is electrically connected with the flyback switching power supply controller; the flyback switching power supply controller is electrically connected with a grid electrode of a primary side switching tube of the flyback switching power supply; when the primary current of the flyback switching power supply flows through the current transformer CT, the secondary side of the current transformer CT outputs a sampling current value with a corresponding proportion, the sampling current value is converted into a sampling voltage value through the resistor R2 of the sampling current conversion circuit after being subjected to forward protection of the diode D of the forward protection circuit, and then the sampling voltage value is sent to the overcurrent detection pin of the flyback switching power supply controller through the input resistor R3 and the pull-up resistor R4 of the signal input circuit; the voltage signal of an overcurrent detection pin of the flyback switching power supply controller is compared with the reference voltage of an internal operational amplifier of the flyback switching power supply controller, and if the voltage signal of the overcurrent detection pin is larger than the reference voltage value, the controller stops the output of a PWM (pulse width modulation) switching signal to play an overcurrent protection role; the power loss of the over-current detection circuit can be greatly reduced, the conversion efficiency of the secondary isolation power supply of the microminiature module is improved, and the power density of the microminiature module is increased.
Drawings
Fig. 1 is a circuit block diagram of an over-current detection circuit of a micro-module flyback switching power supply according to an embodiment of the present invention;
fig. 2 is a circuit diagram of an over-current detection circuit of a micro-module flyback switching power supply according to an embodiment of the present invention.
Detailed Description
The utility model is further described below with reference to the accompanying drawings. The following examples are only for illustrating the technical solutions of the present invention more clearly, and the protection scope of the present invention is not limited thereby.
As shown in fig. 1 and 2, an overcurrent detection circuit of a micro-module flyback switching power supply includes: the current transformer unit 1, the forward protection circuit 2, the sampling current conversion circuit 3 and the signal input circuit 4 are electrically connected in sequence; the current transformer unit 1 is electrically connected with a drain electrode of a primary side switching tube Q of the flyback switching power supply; the signal input circuit 4 is electrically connected with the flyback switching power supply controller; and the flyback switching power supply controller is electrically connected with the grid electrode of the primary side switching tube Q of the flyback switching power supply.
As shown in fig. 2, the current transformer unit 1 includes a current transformer CT; the forward protection circuit 2 includes a resistor R1 and a diode D; the sampling current conversion circuit 3 includes a resistor R2, and the signal input circuit 4 includes an input resistor R3 and a pull-up resistor R4.
The current input end of a primary coil of the current transformer CT is electrically connected with the drain electrode of a primary switch tube of the flyback switch power supply, and the current output end of the primary coil of the current transformer CT is connected with a primary power ground; an equivalent current input end of a secondary coil of the current transformer CT is connected with a first end of the resistor R1 and a positive end of the diode, and an equivalent current output end of the secondary coil of the current transformer CT is connected with a second end of the resistor R1; a first end of the resistor R2 is connected with the negative electrode end of the diode D; the second end of the resistor R2 is connected with the second end of the resistor R1; the first end of the input resistor R3 is connected with the first end of the resistor R2, and the second end of the input resistor R3 is connected with the second section of the pull-up resistor R4 and is connected with the overcurrent detection pin end of the flyback switch power supply controller; a first end of the pull-up resistor R4 is connected to the input voltage positive electrode Vin of the flyback switching power supply. The current transformer CT, the forward protection circuit and the sampling current conversion circuit are grounded.
When the primary current of the flyback switching power supply flows through the current transformer CT, the secondary side of the current transformer CT outputs a sampling current value with a corresponding proportion, the sampling current value is converted into a sampling voltage value through the resistor R2 of the sampling current conversion circuit after being subjected to forward protection of the diode D of the forward protection circuit, and then the sampling voltage value is sent to the overcurrent detection pin of the flyback switching power supply controller through the input resistor R3 and the pull-up resistor R4 of the signal input circuit; the voltage signal of an overcurrent detection pin of the flyback switching power supply controller is compared with the reference voltage of an internal operational amplifier of the flyback switching power supply controller, and if the voltage signal of the overcurrent detection pin is larger than the reference voltage value, the controller stops the output of a PWM (pulse width modulation) switching signal to play an overcurrent protection role; in the embodiment, the overcurrent detection resistor of the switching power supply is replaced by the current transformer, so that the power circuit and the controller chip can be isolated, the power loss of the overcurrent detection circuit can be reduced to a greater extent in the low-power flyback switching power supply, the micro-system module circuit has higher conversion efficiency, high power density is realized, and the low-power flyback switching power supply is suitable for low-voltage input (such as 9-36V) low-power micro-module flyback switching power supplies.
The above description is only a preferred embodiment of the present invention, and it should be noted that, for those skilled in the art, several modifications and variations can be made without departing from the technical principle of the present invention, and these modifications and variations should also be regarded as the protection scope of the present invention.
Claims (6)
1. The utility model provides a micromodule flyback switching power supply overcurrent detection circuit which characterized in that includes: the current transformer unit, the forward protection circuit, the sampling current conversion circuit and the signal input circuit are electrically connected in sequence; the current transformer unit is electrically connected with a drain electrode of a primary side switching tube of the flyback switching power supply; the signal input circuit is electrically connected with the flyback switching power supply controller; and the flyback switching power supply controller is electrically connected with the grid electrode of the primary side switching tube of the flyback switching power supply.
2. The micro-module flyback switching power supply overcurrent detection circuit according to claim 1, wherein the current transformer unit, the forward protection circuit, and the sampling current conversion circuit are grounded in common.
3. The over-current detection circuit of the micro-module flyback switching power supply of claim 1, wherein the current transformer unit comprises a Current Transformer (CT), a current input end of a primary coil of the Current Transformer (CT) is electrically connected with a drain electrode of a primary switching tube of the flyback switching power supply, and a current output end of the primary coil of the Current Transformer (CT) is connected with a primary power ground; and a secondary side coil of the current transformer CT is electrically connected with the forward protection circuit.
4. The micro-module flyback switching power supply overcurrent detection circuit according to claim 3, wherein the forward protection circuit comprises a resistor R1 and a diode D, a secondary coil equivalent current input terminal of the current transformer CT is connected with a first end of the resistor R1 and a positive end of the diode, and a secondary coil equivalent current output terminal of the current transformer CT is connected with a second end of the resistor R1; the cathode end of the diode D and the second end of the resistor R1 are connected with the sampling current conversion circuit.
5. The micro-module flyback switching power supply overcurrent detection circuit according to claim 4, wherein the sampling current conversion circuit comprises a resistor R2, and a first end of the resistor R2 is connected to a negative terminal of a diode D; the second end of the resistor R2 is connected with the second end of the resistor R1; a first terminal of the resistor R2 is connected to the signal input circuit.
6. The micro-module flyback switching power supply overcurrent detection circuit of claim 4, wherein the signal input circuit comprises an input resistor R3 and a pull-up resistor R4, a first end of the input resistor R3 is connected to a first end of the resistor R2, and a second end of the input resistor R3 is connected to a second segment of the pull-up resistor R4 and to an overcurrent detection pin terminal of the flyback switching power supply controller; a first end of the pull-up resistor R4 is connected to the input voltage positive electrode Vin of the flyback switching power supply.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122722725.XU CN216351141U (en) | 2021-11-09 | 2021-11-09 | Micromodule flyback switching power supply overcurrent detection circuit |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN202122722725.XU CN216351141U (en) | 2021-11-09 | 2021-11-09 | Micromodule flyback switching power supply overcurrent detection circuit |
Publications (1)
| Publication Number | Publication Date |
|---|---|
| CN216351141U true CN216351141U (en) | 2022-04-19 |
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Family Applications (1)
| Application Number | Title | Priority Date | Filing Date |
|---|---|---|---|
| CN202122722725.XU Active CN216351141U (en) | 2021-11-09 | 2021-11-09 | Micromodule flyback switching power supply overcurrent detection circuit |
Country Status (1)
| Country | Link |
|---|---|
| CN (1) | CN216351141U (en) |
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2021
- 2021-11-09 CN CN202122722725.XU patent/CN216351141U/en active Active
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