CN109586559B - Starting circuit of off-line switching power supply and switching power supply - Google Patents
Starting circuit of off-line switching power supply and switching power supply Download PDFInfo
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- CN109586559B CN109586559B CN201910020758.4A CN201910020758A CN109586559B CN 109586559 B CN109586559 B CN 109586559B CN 201910020758 A CN201910020758 A CN 201910020758A CN 109586559 B CN109586559 B CN 109586559B
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- 230000005669 field effect Effects 0.000 claims abstract description 68
- 239000003990 capacitor Substances 0.000 claims abstract description 26
- 238000005265 energy consumption Methods 0.000 abstract description 5
- 238000007599 discharging Methods 0.000 abstract description 2
- 238000004804 winding Methods 0.000 description 9
- 238000010586 diagram Methods 0.000 description 5
- 230000000087 stabilizing effect Effects 0.000 description 3
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 238000006467 substitution reaction Methods 0.000 description 2
- 230000009286 beneficial effect Effects 0.000 description 1
- 230000015556 catabolic process Effects 0.000 description 1
- 230000001105 regulatory effect Effects 0.000 description 1
Classifications
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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
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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
- H02M3/00—Conversion of dc power input into dc power output
- H02M3/22—Conversion of dc power input into dc power output with intermediate conversion into ac
- H02M3/24—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters
- H02M3/28—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac
- H02M3/325—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal
- H02M3/335—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only
- H02M3/33569—Conversion of dc power input into dc power output with intermediate conversion into ac by static converters using discharge tubes with control electrode or semiconductor devices with control electrode to produce the intermediate ac using devices of a triode or a transistor type requiring continuous application of a control signal using semiconductor devices only having several active switching elements
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- Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
- Y02—TECHNOLOGIES OR APPLICATIONS FOR MITIGATION OR ADAPTATION AGAINST CLIMATE CHANGE
- Y02B—CLIMATE CHANGE MITIGATION TECHNOLOGIES RELATED TO BUILDINGS, e.g. HOUSING, HOUSE APPLIANCES OR RELATED END-USER APPLICATIONS
- Y02B70/00—Technologies for an efficient end-user side electric power management and consumption
- Y02B70/10—Technologies improving the efficiency by using switched-mode power supplies [SMPS], i.e. efficient power electronics conversion e.g. power factor correction or reduction of losses in power supplies or efficient standby modes
Landscapes
- Engineering & Computer Science (AREA)
- Power Engineering (AREA)
- Dc-Dc Converters (AREA)
Abstract
The application discloses a starting circuit of an off-line switching power supply and the switching power supply. The starting circuit comprises a high-resistance starting resistor, a starting capacitor, a comparison circuit, a first field effect transistor and a feedback circuit. The switching power supply comprises the starting circuit, a control chip, a second field effect transistor, a third field effect transistor and a transformer. According to the application, the first end of the high-resistance starting resistor is used for being connected with a high-voltage power supply, the starting current is limited by the high-resistance resistor, and the starting capacitor is charged. The positive electrode of the starting capacitor is connected with the first input end of the comparison circuit for discharging, the output end of the comparison circuit is connected with the grid electrode of the first field effect tube, and the feedback circuit is connected with the drain electrode of the first field effect tube to prevent the critical point from shaking. The technical problems of high cost and high energy consumption caused by the fact that a circuit can be started only by a high-power adjusting tube in the prior art are solved, and therefore the starting circuit of the off-line switching power supply with low cost and low energy consumption is achieved.
Description
Technical Field
The application relates to the field of circuits, in particular to a starting circuit of an off-line switching power supply and the switching power supply.
Background
In the prior art, for some older types of high-frequency control chips (e.g., SG3525, TL 494), the start-up circuit is a non-negligible part if it is required to use it for an off-line switching power supply. As shown in FIG. 1, the commercial power is rectified and filtered to obtain high-voltage direct current HV, the HV value corresponding to 220V alternating current input is about 310V, the VCC typical voltage of the control chip is 12V, and the working current is between 10 mA and 30 mA. The traditional mode is that a linear voltage stabilizing circuit formed by R1, Q3, D5 and D3 in a frame is used for directly reducing voltage from HV to 12V, after a control chip works, switching tubes Q1 and Q2 are alternately driven to be conducted (the duty ratio is 50% at maximum) by the control chip, a main winding N1 of a main transformer obtains high-frequency voltage, an auxiliary winding N2 induces proportional voltage, and the proportional voltage is rectified and filtered by D4 and C3 to obtain normal working voltage of the chip. As long as the winding design of N2 is proper, the induced voltage of N2 is always higher than the output of the linear voltage stabilizing circuit, the regulating tube Q3 is in a cut-off state, and the power supply is started. Since there is a relatively high voltage difference between HV and VCC, in order to cope with possible faults, such as unsuccessful power supply start-up, the linear voltage stabilizing circuit is always operated, and the heat is not negligible, so the regulator Q3 must use a device capable of withstanding high power, and a radiator needs to be added if necessary, resulting in increased cost and device volume. If a low power device is selected for cost reduction, the circuit becomes unreliable.
Disclosure of Invention
The present application aims to solve at least one of the technical problems in the related art to some extent. Therefore, an object of the present application is to provide a low-cost and low-energy-consumption starting circuit for an off-line switching power supply and a switching power supply.
The technical scheme adopted by the application is as follows: the starting circuit of the off-line switching power supply comprises a high-resistance starting resistor, a starting capacitor, a comparison circuit, a first field effect transistor and a feedback circuit, wherein the comparison circuit comprises a first input end, a second input end and an output end;
the first end of the high-resistance starting resistor is used for being connected with a high-voltage power supply, and the second end of the high-resistance starting resistor is respectively connected with the anode of the starting capacitor and the first input end of the comparison circuit;
the negative electrode of the starting capacitor is grounded;
the first input end of the comparison circuit is connected with the source electrode of the first field effect transistor, the second input end of the comparison circuit is grounded, and the output end of the comparison circuit is connected with the grid electrode of the first field effect transistor;
the drain electrode of the first field effect transistor is connected with the input end of the feedback circuit, and the output end of the feedback circuit is connected with the first input end of the comparison circuit.
Preferably, the comparison circuit comprises a first resistor, a second resistor and a reference amplifying chip;
the first end of the first resistor is connected with the second end of the high-resistance starting resistor, the second end of the first resistor is connected with the first end of the second resistor, and the second end of the first resistor is connected with the first input end of the reference amplifying chip;
the second end of the second resistor is grounded;
the second input end of the reference amplifying chip is grounded, and the output end of the reference amplifying chip is connected with the grid electrode of the first field effect transistor;
the reference amplifying chip is used for comparing the discharge voltage of the starting capacitor with a preset reference voltage and outputting a control signal according to a comparison result to control the on/off of the first field effect transistor.
Preferably, the feedback circuit comprises a third resistor and a first diode;
the first end of the third resistor is connected with the drain electrode of the first field effect transistor, and the second end of the third resistor is connected with the positive electrode of the first diode;
the negative electrode of the first diode is connected with the second end of the first resistor.
Preferably, the first end of the fourth resistor is connected with the source electrode of the first field effect transistor, and the second end of the fourth resistor is connected with the grid electrode of the first field effect transistor.
Preferably, the model number of the reference amplifying chip is TL432.
A switching power supply comprises the starting circuit and control chip of the off-line switching power supply, a second field effect transistor, a third field effect transistor and a transformer;
the input end of the control chip is connected with the drain electrode of the first field effect tube, and the output end of the control chip is respectively connected with the grid electrode of the second field effect tube and the grid electrode of the third field effect tube;
the source electrode of the second field effect tube is grounded, and the drain electrode of the second field effect tube is connected with the source electrode of the third field effect tube;
the drain electrode of the third field effect transistor is connected with the input end of the transformer, and the output end of the transformer is connected with the second end of the high-resistance starting resistor.
The beneficial effects of the application are as follows:
according to the application, the high-resistance starting resistor, the starting capacitor, the comparison circuit, the first field effect transistor and the feedback circuit are arranged, the first end of the high-resistance starting resistor is used for being connected with a high-voltage power supply, the starting current is limited by the high-resistance resistor, and the starting capacitor is charged. The positive electrode of the starting capacitor is connected with the first input end of the comparison circuit for discharging, the output end of the comparison circuit is connected with the grid electrode of the first field effect tube, and the feedback circuit is connected with the drain electrode of the first field effect tube to prevent the critical point from shaking. The technical problems of high cost and high energy consumption caused by the fact that a circuit can be started only by a high-power adjusting tube in the prior art are solved, and therefore the starting circuit of the off-line switching power supply with low cost and low energy consumption is achieved.
Drawings
FIG. 1 is a schematic diagram of a prior art starting circuit for an off-line switching power supply;
FIG. 2 is a schematic diagram of a power-up circuit of an off-line switching power supply according to an embodiment of the present application;
FIG. 3 is a schematic circuit diagram of another embodiment of a start-up circuit for an off-line switching power supply according to the present application;
FIG. 4 is a schematic diagram of a reference amplifying chip according to an embodiment of the present application.
Detailed Description
It should be noted that, without conflict, the embodiments of the present application and features of the embodiments may be combined with each other.
The application provides a starting circuit of an off-line switching power supply. As shown in FIG. 2, the starting circuit comprises a high-resistance starting resistor, a starting capacitor, a comparison circuit, a first field effect transistor and a feedback circuit.
The comparison circuit comprises a first input end, a second input end and an output end.
The first end of the high-resistance starting resistor is used for being connected with a high-voltage power supply, and the second end of the high-resistance starting resistor is respectively connected with the positive electrode of the starting capacitor and the first input end of the comparison circuit.
The negative electrode of the starting capacitor is grounded.
The first input end of the comparison circuit is connected with the source electrode of the first field effect tube, the second input end of the comparison circuit is grounded, and the output end of the comparison circuit is connected with the grid electrode of the first field effect tube.
The drain electrode of the first field effect transistor is connected with the input end of the feedback circuit, and the output end of the feedback circuit is connected with the first input end of the comparison circuit.
In this embodiment, the starting current is limited to 1-2 mA by using a high-resistance starting resistor. The resistance range of the high-resistance starting resistor is 100K-300K.
In this embodiment, the first field effect transistor is an NMOS transistor.
Fig. 3 is a schematic circuit diagram of another embodiment of a starting circuit of an off-line switching power supply according to the present application. Wherein R1 is a high-resistance starting resistor, C4 is a starting capacitor, and Q4 is a first field effect transistor.
In this embodiment, the comparison circuit includes a first resistor R3, a second resistor R5, and a reference amplifying chip U1.
The first end of the first resistor R3 is connected with the second end of the high-resistance starting resistor R1, the second end of the first resistor R3 is connected with the first end of the second resistor R5, and the second end of the first resistor R3 is connected with the first input end of the reference amplifying chip U1.
The second terminal of the second resistor R5 is grounded.
The second input end of the reference amplifying chip U1 is grounded, and the output end of the reference amplifying chip U1 is connected with the grid electrode of the first field effect transistor Q4.
The reference amplifying chip U1 is configured to compare the discharge voltage of the start capacitor C4 with a preset reference voltage, and output a control signal according to the comparison result, to control the on/off of the first field effect transistor Q4.
In this embodiment, the model TL432 of the reference amplifying chip U1 or another type of chip. As shown in fig. 4, the reference amplifying chip U1 operates on the following principle: the pin A is A reference point of the chip, and before the voltage between the pins R-A reaches the reference voltage value (1.25V) in the chip, the voltage between the pins K-A is high, and the current flowing through the pins K-A is about 100 uA; after the voltage between the R-A pins reaches the reference voltage value (1.25V) in the chip, the triode in the chip is driven, the voltage between the K-A pins is low, and the first field effect transistor Q4 is conducted. The reference amplifying chip U1 may be understood as a three-terminal voltage comparator with a reference voltage, where the R terminal is a first input terminal of the reference amplifying chip U1, the a terminal is a second input terminal of the reference amplifying chip U1, and the K terminal is an output terminal of the reference amplifying chip U1.
In this embodiment, the feedback circuit includes a third resistor R2 and a first diode D5.
As shown in fig. 3, a first end of the third resistor R2 is connected to the drain of the first field effect transistor Q4, and a second end of the third resistor R2 is connected to the anode of the first diode D5. The negative electrode of the first diode D5 is connected to the second end of the first resistor R3.
In this embodiment, the starting circuit further includes a fourth resistor R4. The first end of the fourth resistor R4 is connected with the source electrode of the first field effect transistor Q4, and the second end of the fourth resistor R4 is connected with the grid electrode of the first field effect transistor Q4. The fourth resistor R4 is connected between the source and the drain of the first fet Q4, so as to prevent electrostatic breakdown of the first fet Q4.
The application also provides a switching power supply, which comprises the starting circuit, a control chip, a second field effect transistor Q2, a third field effect transistor Q1 and a transformer T1 as shown in figure 3.
The input end of the control chip is connected with the drain electrode of the first field effect transistor Q4, and the output end of the control chip is respectively connected with the grid electrode of the second field effect transistor Q2 and the grid electrode of the third field effect transistor Q1.
The source electrode of the second field effect tube Q2 is grounded, and the drain electrode of the second field effect tube Q2 is connected with the source electrode of the third field effect tube Q1.
The drain electrode of the third field effect transistor Q1 is connected with the input end of the transformer T1, and the output end of the transformer T1 is connected with the second end of the high-resistance starting resistor R1.
In this embodiment, a capacitor C1 is further connected between the third fet Q1 and the transformer T1, and a capacitor C2 is further connected between the negative electrode of the capacitor C1 and ground.
The specific working principle is as follows:
after the switch power supply is electrified, the high voltage HV is connected in, the high-resistance starting resistor R1 is used for limiting current, and only weak starting current (generally 1-2 mA) is provided for charging the starting capacitor C4. When the voltage of the start capacitor C4 is charged to the start value (r3/r5+1) ×1.25, the voltage between the R-a pins of the reference amplifying chip U1 reaches the reference voltage value, the potential of the K pin becomes low, and the first fet Q4 is turned on. The third resistor R2 and the first diode D5 provide a return difference value such that the start-up value of the circuit becomes (((r3×r2/(r3+r2))/r5) +1) 1.25, preventing the critical point from being dithered. The voltage stored by the starting capacitor C4 is provided to the control chip through the first field effect transistor Q4 to supply power to the control chip. After the control chip starts to work, the second field effect transistor Q2 and the third field effect transistor Q1 are alternately driven to be conducted (duty ratio is 50 percent respectively) by the control chip, the main winding N1 of the transformer T1 obtains high-frequency voltage, and the proportional voltage induced by the auxiliary winding N2 is provided for the normal working voltage of the control chip after being rectified and filtered by the second diode D4 and the starting capacitor C4. The voltages induced by the N3 winding and the N4 winding of the transformer T1 serve as output terminals of the switching power supply, and power is supplied to subsequent devices.
As long as the auxiliary winding N2 is properly designed, the induced voltage of the auxiliary winding N2 can be always higher than the start-up feedback value (r3+r2))/r5) +1) by 1.25, and the induced voltage can be always provided to the control chip through the start-up circuit, so that the start-up of the switching power supply is completed.
The switch power supply starting circuit has very high voltage difference from HV to Vcc, but has small starting current and low power consumption due to the arrangement of the high-resistance starting resistor. Moreover, a high-power tube is not needed, and the cost is low.
While the preferred embodiment of the present application has been described in detail, the present application is not limited to the embodiments, and those skilled in the art can make various equivalent modifications or substitutions without departing from the spirit of the present application, and the equivalent modifications or substitutions are included in the scope of the present application as defined in the appended claims.
Claims (5)
1. The starting circuit of the off-line switching power supply is characterized by comprising a high-resistance starting resistor, a starting capacitor, a comparison circuit, a first field effect transistor and a feedback circuit, wherein the comparison circuit comprises a first input end, a second input end and an output end;
the first end of the high-resistance starting resistor is used for being connected with a high-voltage power supply, and the second end of the high-resistance starting resistor is respectively connected with the anode of the starting capacitor and the first input end of the comparison circuit;
the negative electrode of the starting capacitor is grounded;
the first input end of the comparison circuit is connected with the source electrode of the first field effect transistor, the second input end of the comparison circuit is grounded, and the output end of the comparison circuit is connected with the grid electrode of the first field effect transistor;
the drain electrode of the first field effect transistor is connected with the input end of the feedback circuit, and the output end of the feedback circuit is connected with the first input end of the comparison circuit;
wherein, the comparison circuit also includes a reference amplifying chip with model TL432.
2. The startup circuit of an off-line switching power supply according to claim 1, wherein the comparison circuit further comprises a first resistor and a second resistor;
the first end of the first resistor is connected with the second end of the high-resistance starting resistor, the second end of the first resistor is connected with the first end of the second resistor, and the second end of the first resistor is connected with the first input end of the reference amplifying chip;
the second end of the second resistor is grounded;
the second input end of the reference amplifying chip is grounded, and the output end of the reference amplifying chip is connected with the grid electrode of the first field effect transistor;
the reference amplifying chip is used for comparing the discharge voltage of the starting capacitor with a preset reference voltage and outputting a control signal according to a comparison result to control the on/off of the first field effect transistor.
3. The startup circuit of an off-line switching power supply according to claim 1, wherein the feedback circuit comprises a third resistor and a first diode;
the first end of the third resistor is connected with the drain electrode of the first field effect transistor, and the second end of the third resistor is connected with the positive electrode of the first diode;
the negative electrode of the first diode is connected with the second end of the first resistor.
4. The startup circuit of an off-line switching power supply of claim 1, further comprising a fourth resistor, wherein a first end of the fourth resistor is connected to a source of the first field effect transistor and a second end of the fourth resistor is connected to a gate of the first field effect transistor.
5. A switching power supply, characterized by comprising a starting circuit and a control chip of an off-line switching power supply as claimed in any one of claims 1-4, a second field effect transistor, a third field effect transistor and a transformer;
the input end of the control chip is connected with the drain electrode of the first field effect tube, and the output end of the control chip is respectively connected with the grid electrode of the second field effect tube and the grid electrode of the third field effect tube;
the source electrode of the second field effect tube is grounded, and the drain electrode of the second field effect tube is connected with the source electrode of the third field effect tube;
the drain electrode of the third field effect transistor is connected with the input end of the transformer, and the output end of the transformer is connected with the second end of the high-resistance starting resistor.
Priority Applications (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910020758.4A CN109586559B (en) | 2019-01-09 | 2019-01-09 | Starting circuit of off-line switching power supply and switching power supply |
Applications Claiming Priority (1)
| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CN201910020758.4A CN109586559B (en) | 2019-01-09 | 2019-01-09 | Starting circuit of off-line switching power supply and switching power supply |
Publications (2)
| Publication Number | Publication Date |
|---|---|
| CN109586559A CN109586559A (en) | 2019-04-05 |
| CN109586559B true CN109586559B (en) | 2023-10-20 |
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| CN201910020758.4A Active CN109586559B (en) | 2019-01-09 | 2019-01-09 | Starting circuit of off-line switching power supply and switching power supply |
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| CN101674018A (en) * | 2009-10-09 | 2010-03-17 | 南京航空航天大学 | Multi-module combined converter and soft start control method thereof |
| CN101739112A (en) * | 2009-12-01 | 2010-06-16 | 广东威创视讯科技股份有限公司 | Low-voltage slow start circuit |
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| CN205141657U (en) * | 2015-11-05 | 2016-04-06 | 广州金升阳科技有限公司 | Input overvoltage crowbar |
| CN106100312A (en) * | 2016-08-25 | 2016-11-09 | 贵州航天凯山石油仪器有限公司 | A kind of DC source start-up circuit being applicable to high input impedance |
| CN106452037A (en) * | 2016-11-23 | 2017-02-22 | 生迪智慧科技有限公司 | Power control circuit and current protection circuit |
-
2019
- 2019-01-09 CN CN201910020758.4A patent/CN109586559B/en active Active
Patent Citations (8)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN101232199A (en) * | 2003-07-07 | 2008-07-30 | 日本电信电话株式会社 | Booster |
| CN101651426A (en) * | 2009-09-10 | 2010-02-17 | 广州金升阳科技有限公司 | Self-starting control power converter of output terminal |
| CN101674018A (en) * | 2009-10-09 | 2010-03-17 | 南京航空航天大学 | Multi-module combined converter and soft start control method thereof |
| CN101739112A (en) * | 2009-12-01 | 2010-06-16 | 广东威创视讯科技股份有限公司 | Low-voltage slow start circuit |
| CN202043032U (en) * | 2011-05-19 | 2011-11-16 | 深圳市振华微电子有限公司 | Micropower starting circuit of switching power supply |
| CN205141657U (en) * | 2015-11-05 | 2016-04-06 | 广州金升阳科技有限公司 | Input overvoltage crowbar |
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