CN201349124Y - Over-current protection sampling circuit for switching power supply - Google Patents
Over-current protection sampling circuit for switching power supply Download PDFInfo
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- CN201349124Y CN201349124Y CNU2009201295796U CN200920129579U CN201349124Y CN 201349124 Y CN201349124 Y CN 201349124Y CN U2009201295796 U CNU2009201295796 U CN U2009201295796U CN 200920129579 U CN200920129579 U CN 200920129579U CN 201349124 Y CN201349124 Y CN 201349124Y
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- 239000003990 capacitor Substances 0.000 claims abstract description 8
- 238000002955 isolation Methods 0.000 abstract description 2
- 238000004804 winding Methods 0.000 abstract 2
- 238000004519 manufacturing process Methods 0.000 abstract 1
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Abstract
The utility model discloses an over-current protection sampling circuit for a switching power supply. The circuit comprises a current sampling transformer which is connected in a primary loop of a main switching transformer, one end of a primary winding of the current sampling transformer is connected with an anode of a rectifier diode D1, a cathode of the rectifier diode D1 is connected with one end of a resistor R2, and the connection point is a CS end and is connected with a PWM circuit. The primary winding of a T1 is further connected with the anode of the rectifier diode D2, the cathode of the D2 is connected with the resistor R3 and one end of a capacitor C1, and the connection point is an IOV end and is connected with the PWM circuit. The over-current protection sampling circuit for the switching power supply has the advantages that the over-current protection sampling circuit simultaneously realizes the double functions of providing cycle-by-cycle switch current limit sampling signals and outputting current over-current protection sampling signals when sampling in the primary loop of the main switching transformer; and the switching power supply over-current protection sampling circuit does not need to use a primary isolation circuit, does not increase a primary sampling transformer or a sampling resistor and has small size, few elements, simple circuit, low power consumption and easy manufacture.
Description
Technical field
The utility model relates to a kind of Switching Power Supply overcurrent protection sample circuit.
Background technology
In switching power circuit, general requirement has current foldback circuit.Current foldback circuit is generally obtained over-current signal (sampled signal) at output, gives control circuit after treatment, and switching tube is controlled, and realizes overcurrent protection.
In the output sampling, be divided into two kinds of schemes substantially.A kind of is resistance sampling, promptly at output loop series connection sample resistance, when output current flows through sample resistance, produce voltage difference at the sample resistance two ends, this voltage difference is proportional to output current, by setting this sample resistance, can set the output overcurrent point, this scheme can produce big power loss on sample resistance when output current is big, reduce the conversion efficiency of Switching Power Supply greatly.
Another kind by being connected on the current sampling coil of main switch transformer secondary, is obtained the current signal of output for the transformer sampling, as the overcurrent protection signal, by feeding back to elementary control circuit, overcurrent protection is set with this signal.This scheme is when output current is big, and the current sampling coil of main switch transformer secondary is made difficulty.
The output sampling mode, in first utmost point isolation type switch power, it is elementary to take quarantine measures that sampled signal is delivered to, and has increased the complexity and the cost of circuit.
Summary of the invention
The utility model is at defective that exists in the prior art or deficiency; employing is elementary at the DC/DC converter; mode with current sampling; by a current sampling transformer and additional circuit design; at elementary realization current sampling, provide the sampled signal of realizing Cycle by Cycle switching current current limliting and output current overcurrent protection dual-use function.
The utility model is by realizing by the following technical solutions:
Design a kind of Switching Power Supply overcurrent protection sample circuit, described circuit comprises:
One current sampling transformer, described current sampling transformer elementary are serially connected in the primary return of main switch transformer, a secondary end ground connection of described current sampling transformer, and the secondary other end of described current sampling transformer connects:
The anode of one rectifier diode D1, the end of the negative electrode connecting resistance R2 of described rectifier diode D1, this tie point are the CS end, the other end ground connection of resistance R 2;
Described CS end connects pwm circuit.
At an end of the anode of the secondary connection rectifier diode D1 of current sampling transformer, also connect the anode of rectifier diode D2, the negative electrode of described rectifier diode D2 connects an end of resistance R 3 and capacitor C 1, and this tie point is I
OVEnd, the other end of resistance R 3 and capacitor C 1 is ground connection all, described I
OVEnd connects pwm circuit.
Between described current sampling transformer secondary, connect a resistance R 1.
Opposite side at the primary return of described main switch transformer connects a DC/DC converter switches transistor Q1, and described pwm circuit connects the control utmost point of DC/DC converter switches transistor Q1.
Compared with prior art, superiority of the present utility model is:
1, uses same group of coil of a current sampling transformer,, realize providing Cycle by Cycle switching current current limliting sampled signal and output current overcurrent protection sampled signal dual-use function simultaneously in elementary sampling;
2, do not need to use the primary and secondary buffer circuit;
3, do not increase secondary sampling transformer and sample resistance, volume is little, element is few, circuit is simple, low in energy consumption, make easily.
Description of drawings
Fig. 1 is the circuit diagram of a kind of Switching Power Supply overcurrent protection of the utility model sample circuit;
Fig. 2 is the sampled signal oscillogram that is input to pwm circuit of a kind of Switching Power Supply overcurrent protection of the utility model sample circuit.
Embodiment
Below in conjunction with accompanying drawing and embodiment the utility model is described in further detail.
As shown in Figure 1 and Figure 2, design a kind of Switching Power Supply overcurrent protection sample circuit, described circuit comprises:
One current sampling transformer T1, described current sampling transformer elementary is serially connected in the primary return of main switch transformer.A secondary end ground connection of described current sampling transformer according to shown in the figure, is noted end of the same name and non-same polarity during connection.
The secondary other end of described current sampling transformer connects:
The anode of one rectifier diode D1, the end of the negative electrode connecting resistance R2 of described rectifier diode D1, this tie point are the CS end, the other end ground connection of resistance R 2;
Described CS end connects pwm circuit.
As shown in Figure 2, the signal proportion of described CS end output is in DC/DC converter switches cycle input current signal waveform.
At an end of the anode of the secondary connection rectifier diode D1 of current sampling transformer, also connect the anode of rectifier diode D2, the negative electrode of described rectifier diode D2 connects an end of resistance R 3 and capacitor C 1, and this tie point is I
OVEnd, the other end of resistance R 3 and capacitor C 1 is ground connection all, described I
OVEnd connects pwm circuit.
As shown in Figure 2 because and connect capacitor C 1, filter action has just been arranged, triangular waveform becomes a dc waveform, in pwm circuit, respectively these two kinds of signals are handled accordingly, pwm circuit will be exported a suitable pulse signal and give DC/DC converter switches transistor Q1.
Between described current sampling transformer secondary, connect a resistance R 1.
Opposite side at the primary return of described main switch transformer connects a DC/DC converter switches transistor Q1, and described pwm circuit connects the control utmost point of DC/DC converter switches transistor Q1.
Circuit theory of the present utility model:
Vin is DC/DC transducer input anode, and T1 is the current sampling transformer of input, and T2 is the main switch transformer, and Q1 is a DC/DC converter switches transistor.By T1 coupling sampling, obtain current signal at T1 secondary (3～4 end), after this signal process rectifier diode D1 rectification, at CS end output Cycle by Cycle switching current signal, the voltage signal on the R2 just offers the control circuit of Q1, realizes Cycle by Cycle switching current current limliting.
The current signal that while is obtained at T1 secondary (3～4 end); after rectifier diode D2 rectification, C1 filtering; at output of Iov end and the proportional average current signal of input current; the voltage signal on the R3 just; offer the control circuit of Q1, realize switch power supply output current current-limiting protection.
In this circuit, R1 is used for the magnetic reset of T1, and C1 selects according to the required precision of output current overcurrent set-point.
Above content be in conjunction with concrete preferred implementation to further describing that the utility model is done, can not assert that concrete enforcement of the present utility model is confined to these explanations.For the utility model person of an ordinary skill in the technical field, under the prerequisite that does not break away from the utility model design, can also make some simple deduction or replace, all should be considered as belonging to protection range of the present utility model.
Claims (4)
1. Switching Power Supply overcurrent protection sample circuit is characterized in that described circuit comprises:
One current sampling transformer, described current sampling transformer elementary is serially connected in the primary return of main switch transformer, a secondary end ground connection of described current sampling transformer, the secondary other end of described current sampling transformer connects the anode of a rectifier diode D1, the end of the negative electrode connecting resistance R2 of described rectifier diode D1, this tie point is the CS end, the other end ground connection of resistance R 2;
Described CS end connects pwm circuit.
2. Switching Power Supply overcurrent protection sample circuit according to claim 1 is characterized in that:
At an end of the anode of the secondary connection rectifier diode D1 of current sampling transformer, also connect the anode of rectifier diode D2, the negative electrode of described rectifier diode D2 connects an end of resistance R 3 and capacitor C 1, and this tie point is I
OVEnd, the other end of resistance R 3 and capacitor C 1 is ground connection all, described I
OVEnd connects pwm circuit.
3. Switching Power Supply overcurrent protection sample circuit according to claim 1 is characterized in that:
Between described current sampling transformer secondary, connect a resistance R 1.
4. Switching Power Supply overcurrent protection sample circuit according to claim 1 is characterized in that:
Opposite side at the primary return of described main switch transformer connects a DC/DC converter switches transistor Q1, and described pwm circuit connects the control utmost point of DC/DC converter switches transistor Q1.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2009201295796U CN201349124Y (en) | 2009-01-20 | 2009-01-20 | Over-current protection sampling circuit for switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNU2009201295796U CN201349124Y (en) | 2009-01-20 | 2009-01-20 | Over-current protection sampling circuit for switching power supply |
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| Publication Number | Publication Date |
|---|---|
| CN201349124Y true CN201349124Y (en) | 2009-11-18 |
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| Application Number | Title | Priority Date | Filing Date |
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| CNU2009201295796U Expired - Lifetime CN201349124Y (en) | 2009-01-20 | 2009-01-20 | Over-current protection sampling circuit for switching power supply |
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Cited By (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103441672A (en) * | 2013-07-25 | 2013-12-11 | 北京控制工程研究所 | Self-excitation BUCK circuit based on auxiliary winding sampling circuit |
| CN104201912A (en) * | 2014-08-15 | 2014-12-10 | 京东方科技集团股份有限公司 | Alternating current-direct current (AC-DC) converter, power panel and display device |
| CN112014621A (en) * | 2020-08-03 | 2020-12-01 | 深圳创维－Rgb电子有限公司 | A current detection circuit, switching power supply and TV set |
-
2009
- 2009-01-20 CN CNU2009201295796U patent/CN201349124Y/en not_active Expired - Lifetime
Cited By (6)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN103441672A (en) * | 2013-07-25 | 2013-12-11 | 北京控制工程研究所 | Self-excitation BUCK circuit based on auxiliary winding sampling circuit |
| CN103441672B (en) * | 2013-07-25 | 2016-02-10 | 北京控制工程研究所 | A kind of self-excitation BUCK circuit based on auxiliary winding type sample circuit |
| CN104201912A (en) * | 2014-08-15 | 2014-12-10 | 京东方科技集团股份有限公司 | Alternating current-direct current (AC-DC) converter, power panel and display device |
| CN104201912B (en) * | 2014-08-15 | 2017-12-26 | 京东方科技集团股份有限公司 | A kind of AC DC converters, power panel and display device |
| US10026372B2 (en) | 2014-08-15 | 2018-07-17 | Boe Technology Group Co., Ltd. | Alternating current-direct current converter, power supply board and display apparatus |
| CN112014621A (en) * | 2020-08-03 | 2020-12-01 | 深圳创维－Rgb电子有限公司 | A current detection circuit, switching power supply and TV set |
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| Date | Code | Title | Description |
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| C14 | Grant of patent or utility model | ||
| GR01 | Patent grant | ||
| CX01 | Expiry of patent term | ||
| CX01 | Expiry of patent term |
Granted publication date: 20091118 |