CN214900668U - Primary side control circuit and isolated switching power supply - Google Patents
Primary side control circuit and isolated switching power supply Download PDFInfo
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- CN214900668U CN214900668U CN202120387577.8U CN202120387577U CN214900668U CN 214900668 U CN214900668 U CN 214900668U CN 202120387577 U CN202120387577 U CN 202120387577U CN 214900668 U CN214900668 U CN 214900668U
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Abstract
The utility model provides a former limit control circuit and isolated switching power supply. The primary side control circuit comprises a charging and discharging circuit and a driving signal generating circuit. The input end of the charge and discharge circuit is coupled with the first detection signal end, and the charge and discharge circuit controls the charge amount in the charge and discharge circuit within a unit time according to the first detection signal. The charging and discharging circuit is also respectively coupled with a signal end of the primary side inductor median current and a signal end of the secondary side circuit within the demagnetization time so as to control the discharge amount in the charging and discharging circuit within a unit time. The input end of the driving signal generating circuit is coupled with the charging and discharging circuit, and the output end of the driving signal generating circuit is coupled with the main switching tube in the primary side circuit. The utility model provides a primary side control circuit and isolated switching power supply can set for different output current constant current values according to isolated switching power supply's output voltage to effectively realize isolated switching power supply's high accuracy constant power output or adjustable constant current output.
Description
Technical Field
The utility model belongs to the technical field of power electronics, a isolated switching power supply technique is related to, in particular to primary side control circuit and isolated switching power supply.
Background
Isolated switching power supplies are widely used in switching power supplies due to their safety and high noise immunity. The isolated switch power supply comprises a transformer winding, a primary side circuit and a secondary side circuit. The traditional isolated switching power supply obtains a sampling signal through a primary side circuit and controls the switching state of a main switching tube so as to realize the control of constant current output of a secondary side circuit. Specifically, as shown in fig. 1, the isolated switching power supply is a flyback switching power supply, a CS median of a current flowing through a primary inductor is sampled in a primary circuit, a conduction duty ratio of a current of a secondary circuit is obtained, and constant current output control of the flyback switching power supply is realized by controlling the CS median of the current and the conduction duty ratio. In the application of the isolated switching power supply, the output power is often required to be controlled, for example, the application of constant power output, and the high-precision output power control of the isolated switching power supply cannot be effectively realized through the above method.
In view of the above, it is desirable to provide a new structure for solving the above technical problems.
SUMMERY OF THE UTILITY MODEL
In order to solve at least part of the problems, the utility model provides a primary side control circuit and isolated switching power supply.
The utility model discloses a primary side control circuit, primary side control circuit is used for isolation type switching power supply's primary side control, isolation type switching power supply includes primary side circuit and vice limit circuit, primary side control circuit includes:
the input end of the charge and discharge circuit is coupled with the first detection signal end to obtain a first detection signal representing the output voltage so as to control the charge amount in unit time in the charge and discharge circuit; the charging and discharging circuit is respectively coupled with a signal end of the primary side inductor median current and a signal end of the secondary side circuit within the demagnetization time so as to control the discharge amount in the charging and discharging circuit within a unit time; and
and the input end of the driving signal generating circuit is coupled with the charging and discharging circuit, and the output end of the driving signal generating circuit is coupled with a main switching tube in the primary side circuit.
Furthermore, the charging and discharging circuit comprises a discharging circuit, the discharging circuit is coupled to a signal end of the median current of the primary side inductor to control the discharging current, and the discharging circuit is also coupled to a signal end of the demagnetization time of the secondary side circuit to control the discharging time.
Still further, the charge and discharge circuit includes:
a charging circuit coupled to the first detection signal terminal for outputting a charging current according to the first detection signal;
a first capacitor, a first end of which is coupled to the output end of the charging circuit, and a second end of which is coupled to ground; and
and a discharge circuit, a first input end of which is coupled to the first end of the first capacitor, a second input end of which is coupled to the signal end of the demagnetization time of the secondary side circuit, and a third input end of which is coupled to the sampling signal end to receive a sampling signal representing the median current of the primary side inductor, so as to discharge the first capacitor according to the demagnetization time of the secondary side circuit and the sampling signal.
Furthermore, the charging circuit includes a first current source coupled to the first detection signal terminal to output a charging current according to a first detection signal; the discharge circuit includes:
a first switch, a first end of which is coupled to the first end of the first capacitor, and a switch control end of which is coupled to a signal end of the secondary side circuit during degaussing time;
a second switch tube, the drain of which is coupled to the second end of the first switch;
the non-inverting input end of the operational amplifier is coupled with the sampling signal end, the inverting input end of the operational amplifier is coupled with the source electrode of the second switch tube, and the output end of the operational amplifier is coupled with the control end of the second switch tube; and
a third resistor, a first end of which is coupled to the source of the second switch tube, and a second end of which is coupled to ground.
Furthermore, the first end of the first capacitor is coupled to the input end of the driving signal generating circuit, and the primary side control circuit controls the charging process and the discharging process to keep dynamic balance.
Furthermore, the isolated switching power supply is a flyback switching power supply, the flyback switching power supply includes an auxiliary winding, and the charging and discharging circuit is coupled to the auxiliary winding to obtain the first detection signal.
Furthermore, a first adjusting circuit is coupled between the charging and discharging circuit and the first detection signal terminal, and the first adjusting circuit is coupled to the first adjusting parameter and the first detection signal terminal to output a first adjusting signal, so as to control a charging amount per unit time in the charging and discharging circuit.
Furthermore, the charging circuit in the charging and discharging circuit comprises a first current source, and the first adjusting circuit controls the output current I1 of the first current source to be in positive correlation with K/Vdem, where I1 is the output current of the first current source, K is the first adjusting parameter, and Vdem is the first detection signal.
Further, the output current of the first current source satisfies any one of the following three conditions during the setting stage: the output current of the first current source is a fixed value; the output current of the first current source is reduced in a step mode along with the increase of the first detection signal; the output current of the first current source is inversely proportional to the first detection signal.
The utility model discloses an isolated switching power supply, isolated switching power supply includes primary circuit, vice limit circuit and transformer winding, primary circuit includes as above primary control circuit, primary control circuit is used for controlling the on-off state of main switch pipe.
The utility model provides a former limit control circuit and isolated switching power supply. The primary side control circuit comprises a charging and discharging circuit and a driving signal generating circuit. The input end of the charge and discharge circuit receives a first detection signal, and the charge and discharge circuit controls the charge amount in the charge and discharge circuit within a unit time according to the first detection signal. The charging and discharging circuit also controls the discharging amount in the charging and discharging circuit within a unit time according to the median current of the primary side inductor and the demagnetization time of the secondary side circuit so as to control the charging process and the discharging process to keep dynamic balance. The input end of the driving signal generating circuit is coupled with the charging and discharging circuit, and the output end of the driving signal generating circuit is coupled with the main switching tube in the primary side circuit. The utility model provides a primary side control circuit and isolated switching power supply can set for different output current constant current values according to isolated switching power supply's output voltage to effectively realize isolated switching power supply's high accuracy constant power output or adjustable constant current output.
Drawings
Fig. 1 shows a circuit schematic of a prior art flyback switching power supply.
Fig. 2 shows a schematic circuit diagram of an isolated switching power supply according to an embodiment of the present invention.
Fig. 3 shows a schematic circuit diagram of a primary side control circuit according to an embodiment of the present invention.
Fig. 4a and 4b show a voltage and current curve diagram, respectively, according to an embodiment of the invention.
Fig. 5a and 5b show a voltage and current curve diagram, respectively, according to another embodiment of the present invention.
Fig. 6a and 6b show a voltage and current curve diagram, respectively, according to a further embodiment of the present invention.
Fig. 7 is a flow chart illustrating steps of a control method of a primary side control circuit according to an embodiment of the present invention.
Detailed Description
The preferred embodiments of the present invention will be described in detail below with reference to the accompanying drawings.
For further understanding of the present invention, preferred embodiments of the present invention will be described below with reference to examples, but it should be understood that these descriptions are only for the purpose of further illustrating the features and advantages of the present invention, and are not intended to limit the claims of the present invention.
The description in this section is for exemplary embodiments only, and the present invention is not limited to the scope of the embodiments described. The same or similar prior art means and some technical features of the embodiments are mutually replaced and are also within the scope of the description and the protection of the invention.
The term "coupled" or "connected" in this specification includes both direct and indirect connections. An indirect connection is a connection made through an intermediate medium, such as a connection made through an electrically conductive medium, which may have parasitic inductance or parasitic capacitance; indirect connections may also include connections through other active or passive devices, such as connections through switches, follower circuits, etc., that serve the same or similar functional purpose.
The isolated switching power supply includes a primary side circuit and a secondary side circuit, and in a specific application, an output current or an output power is often required to be controlled to realize constant current output or constant power output of the isolated switching power supply. The switching state of a main switching tube in the primary circuit can be controlled according to the average value of the primary side inductive current or the average value of the secondary side inductive current in each switching period, so that the control of the output current or the output power is realized. The primary side inductor current is the current flowing through the inductor in the primary side circuit, and the secondary side inductor current is the current flowing through the inductor in the secondary side circuit. The output current Iout of the isolated switch power supply meets the following conditions:
wherein is (t) is a real-time current flowing through the secondary inductor or a real-time current flowing through the output diode, ip (t) is a real-time current flowing through the primary inductor, N is a turn ratio of a primary winding and a secondary winding of a transformer in the isolated switching power supply, and Ts is a switching period of the main switching tube. And the average current of the secondary side inductor can be expressed by the following formula in a continuous mode and a discontinuous mode:
wherein, Imid_PPrimary side inductance current T acquired by a main switch tube at the middle time point of a conduction time periodDISThe degaussing time of the secondary side inductor is shown. The average output current of the isolated switch power supply can be obtained by the formulaIs composed of
Wherein, Rcs is the sampling resistance of primary side inductance, Vmid _ P is the median voltage on sampling resistance Rcs obtained by main switch tube at the middle time point of conduction time period, DDISIs equal to TDIS/TS，DDISIs the on duty ratio of the secondary side circuit.
An embodiment of the utility model discloses a primary side control circuit, primary side control circuit are used for isolation type switching power supply's primary side control, and isolation type switching power supply includes primary side circuit and vice limit circuit, and primary side control circuit includes charge-discharge circuit and drive signal production circuit. The input end of the charge and discharge circuit is coupled with the first detection signal end to obtain a first detection signal representing the output voltage, and the charge and discharge circuit controls the charge amount in the charge and discharge circuit within a unit time according to the first detection signal. The charging and discharging circuit controls the discharging amount in the charging and discharging circuit within a unit time according to the median current of the primary side inductor and the demagnetization time of the secondary side circuit so as to control the charging process and the discharging process to keep dynamic balance. The output voltage is the output voltage of the isolated switching power supply. The input end of the driving signal generating circuit is coupled with the charging and discharging circuit, and the output end of the driving signal generating circuit is coupled with the main switching tube in the primary side circuit. In an embodiment of the present invention, the primary side inductance median current is the primary side inductance current obtained by the main switching tube at the middle time point of the conduction time period. The unit time may be a single switching period of the main switching tube, or may be a duration formed by a plurality of switching periods of the main switching tube. In one embodiment, the primary side control circuit controls the charging process and the discharging process to keep dynamic balance, and when the isolated switch power supply is in constant current output or constant power output, the charging process and the discharging process keep balance. When the first detection signal changes, the charging amount per unit time in the charging and discharging circuit changes, and the switching state of the main switching tube changes. Correspondingly, the median current of the primary inductor and the demagnetization time of the secondary circuit are correspondingly changed, the discharge amount in the charging and discharging circuit in unit time is adjusted, and the charging process and the discharging process are kept balanced after dynamic adjustment. The utility model discloses can set for different output current constant current values according to isolated switching power supply's output voltage, isolated switching power supply adopts closed-loop control simultaneously to effectively realize isolated switching power supply's high accuracy constant power output or adjustable constant current output.
The utility model discloses in, isolated switching power supply can be typical flyback switching power supply, also can be and be suitable for the utility model discloses technical scheme's other approximate topology.
In an embodiment of the utility model, as shown in fig. 2, isolated switching power supply is for swashing back formula switching power supply, and the output voltage of swashing back formula switching power supply obtains through auxiliary winding Na, and primary side control circuit 100 is equipped with pin DEM, and pin DEM is coupled auxiliary winding Na, and pin DEM is used for acquireing the first detected signal of sign output voltage. In another embodiment, a voltage dividing resistor set is further coupled between the pin DEM and the auxiliary winding Na, the voltage dividing resistor set includes a first resistor R1 and a second resistor R2, a first end of the first resistor R1 is coupled to the auxiliary winding Na, a second end of the first resistor R1 is coupled to the pin DEM, a first end of the second resistor R2 is coupled to a second end of the first resistor R1, and a second end of the second resistor R2 is coupled to ground. In an embodiment of the present invention, the first detection signal is the first detection voltage Vdem.
In an embodiment of the present invention, as shown in fig. 3, the primary side control circuit 100 includes a charging and discharging circuit and a driving signal generating circuit 120, and the charging and discharging circuit includes a charging circuit, a discharging circuit and a first capacitor C1. The charging circuit is coupled to a first detection voltage Vdem representing an output voltage of the flyback switching power supply, and the charging circuit is configured to output a charging current according to the first detection voltage Vdem. The first terminal of the first capacitor C1 is coupled to the output terminal of the charging circuit, and the second terminal of the first capacitor C1 is coupled to ground. The first input end of the discharge circuit is coupled to the first end of the first capacitor C1, the second input end of the discharge circuit receives the demagnetization time of the secondary side circuit, the third input end of the discharge circuit receives a sampling signal representing the median current of the primary side inductor, and the discharge circuit discharges the first capacitor C1 according to the demagnetization time of the secondary side circuit and the sampling signal. In one embodiment, the primary side control circuit 100 includes a main switching tube Q1, and the primary side control circuit 100 has a Drain terminal Drain. In another embodiment, the primary side control circuit 100 does not include the main switching transistor Q1, the primary side control circuit 100 is provided with a driving terminal Gate, and the driving terminal Gate of the primary side control circuit 100 is coupled to the Gate of the main switching transistor.
In an embodiment of the present invention, as shown in fig. 3, the charging circuit includes a first current source I1, and an output terminal of the first current source I1 is coupled to a first terminal of a first capacitor C1. In a specific embodiment, the first current source I1 is a voltage controlled current source. In another embodiment, the first current source I1 may also be a current-controlled current source, and a voltage-to-current conversion circuit is further disposed between the first current source I1 and the pin DEM. In addition, the charging and discharging circuit controls the discharging current according to the median current of the primary inductor, and controls the discharging time according to the degaussing time of the secondary circuit, as shown in fig. 3, the discharging circuit includes a first switch K1, a second switch Q2, an operational amplifier 111 and a third resistor R3. The first terminal of the first switch K1 is coupled to the first terminal of the first capacitor C1, the switch control terminal of the first switch K1 receives the degaussing time of the secondary side circuit, and when the secondary side circuit is in the degaussing time, the first switch K1 is controlled to be turned on. When the flyback switching power supply is in a continuous mode (CCM mode for short), the switching period Ts of the main switching tube includes an on time Ton and a degaussing time Toff. When the flyback switching power supply is in an intermittent mode (DCM for short), the switching period Ts of the main switching tube includes a conduction time Ton, a demagnetization time Tdem, and a dead time Tdie. In an embodiment of the present invention, the switching can be freely performed according to the continuous mode or the intermittent mode to select the corresponding degaussing time Toff or Tdem. The drain of the second switch transistor Q2 is coupled to the second terminal of the first switch K1. The non-inverting input terminal of the operational amplifier 111 is coupled to a sampling voltage Vmid _ P, which is a sampling signal representing a median current of the primary inductor and can be obtained by sampling a current flowing through the primary inductor or sampling a current flowing through a sampling resistor Rcs. The inverting input terminal of the operational amplifier 111 is coupled to the source of the second switch Q2, and the output terminal of the operational amplifier 111 is coupled to the control terminal of the second switch Q2. A first terminal of the third resistor R3 is coupled to the source of the second switch Q2, and a second terminal of the third resistor R3 is coupled to ground. The first end of the first capacitor C1 is coupled to the input end of the driving signal generating circuit 120, and the driving signal generating circuit 120 controls the current peak value and the switching frequency of the main switching transistor Q1 according to the voltage Vc1 across the first capacitor C1.
The utility model discloses an in the embodiment, still be coupled with first regulating circuit between charge-discharge circuit and the first detection signal end DEM, first regulating circuit exports first regulating signal to charge-discharge circuit according to first adjusting parameter and first detection signal, and charge-discharge circuit controls the charge volume in the charge-discharge circuit in the unit time according to first regulating signal. In another embodiment, the charging and discharging circuit includes a first current source, and the first adjusting circuit controls the output current I1 of the first current source to be positively correlated with K/Vdem, where I1 is the output current of the first current source, K is the first adjusting parameter, and Vdem is the first detection signal. In one embodiment, as shown in fig. 4a and 4b, the output current of the first current source is a fixed value, independent of the first detection signal. At this time, the first adjustment parameter K is directly proportional to the first detection signal Vdem, and K is a positive value. Correspondingly, the flyback switching power supply can keep constant current output. In another embodiment, as shown in fig. 5a and 5b, by adjusting the value of K, the output current I1 of the first current source decreases in a staircase shape as the first detection signal Vdem increases. Correspondingly, the flyback switching power supply can realize adjustable constant current output or constant power output. In yet another embodiment, as shown in fig. 6a and 6b, the output current I1 of the first current source is a fixed value in the first stage, and the flyback switching power supply outputs a constant current regardless of the first detection signal. The output current I1 of the first current source is inversely proportional to the first detection signal Vdem in the second stage, and the first adjustment parameter K is a fixed positive value. Correspondingly, the flyback switching power supply can keep constant power output. Based on the utility model discloses a primary side control circuit acquires the first detected signal of sign output voltage through charge-discharge circuit to according to first detected signal control charge-discharge process, drive signal produces the on-off state that circuit generated drive signal with control main switch pipe according to the both ends voltage of first electric capacity, can effectively realize swashing back formula switching power supply's high accuracy constant power output or adjustable constant current output.
The utility model discloses an embodiment still discloses an isolated switching power supply, isolated switching power supply include primary circuit, secondary circuit and transformer winding, and primary circuit passes through transformer winding and with energy transmission to secondary circuit. The primary side circuit comprises any one of the primary side control circuits, and the primary side control circuit is used for controlling the switching state of the main switching tube so as to realize high-precision constant power output or adjustable constant current output of the isolated switching power supply. In an embodiment of the present invention, the main switch transistor is a switch transistor, and may be a metal oxide semiconductor field effect transistor (MOSFET for short) or a junction field effect transistor (JFET for short). In another embodiment, the isolated switching power supply is a flyback switching power supply, and the isolated switching power supply may also be another approximate topology suitable for the technical solution of the present invention.
The utility model discloses an embodiment also discloses a control method of former limit control circuit, and control method is used for isolation switching power supply's former limit control, and isolation switching power supply includes former limit circuit and vice limit circuit, and former limit circuit includes former limit control circuit, and former limit control circuit includes charge-discharge circuit and drive signal production circuit. As shown in fig. 7, the control method of the primary side control circuit includes:
s1OO, acquiring a first detection signal representing output voltage;
step S2OO, controlling a charge amount of the first capacitor per unit time by the charge/discharge circuit according to the first detection signal; controlling the discharge amount of the charge-discharge circuit to the first capacitor in unit time according to the median current of the primary inductor and the demagnetization time of the secondary circuit so as to control the charge process and the discharge process to keep dynamic balance; and
and step S3OO, generating a driving signal according to the voltage at the two ends of the first capacitor so as to control the switching state of a main switching tube in the primary side circuit.
In a specific embodiment, the charging and discharging circuit acquires a first detection signal representing the output voltage, the charging and discharging circuit controls the charging and discharging circuit to charge and discharge the first capacitor in unit time according to the first detection signal, and the charging and discharging circuit controls the discharging amount of the charging and discharging circuit to the first capacitor in unit time according to the primary side inductance median current and the demagnetization time of the secondary side circuit so as to control the charging process and the discharging process to keep dynamic balance. The driving signal generating circuit generates a driving signal according to the voltage at the two ends of the first capacitor, and the driving signal controls the on-off state of a main switching tube in the primary side circuit.
In an embodiment of the present invention, the control method specifically includes: and controlling the discharge current according to the median current of the primary side inductor, and controlling the discharge time according to the demagnetization time of the secondary side circuit. In another embodiment, the isolated switching power supply is a flyback switching power supply, and the isolated switching power supply may also be another approximate topology suitable for the technical solution of the present invention.
In an embodiment of the present invention, the control method further includes: and outputting a first adjusting signal according to the first adjusting parameter and the first detection signal, wherein the first adjusting signal is used for controlling the charging amount in the charging and discharging circuit per unit time.
The utility model discloses an in the embodiment, charge-discharge circuit includes charging circuit, and charging circuit includes first current source, and control method still includes: controlling the output current I1 of the first current source to be positively correlated with K/Vmem, wherein I1 is the output current of the first current source, K is the first adjusting parameter, and Vmem is the first detection signal.
In an embodiment of the present invention, the output current of the first current source satisfies any one of the following three conditions during the setting stage: the output current of the first current source is a fixed value; the output current of the first current source is reduced in a step mode along with the increase of the first detection signal; the output current of the first current source is inversely proportional to the first detection signal. The setting of the setting stage is set according to a specific application scene, and the output current of the first current source can be a fixed value in a constant current output application scene. In order to realize adjustable constant current output or constant power output, the output current of the first current source can be controlled to be reduced in a step shape along with the increase of the first detection signal. When the isolated switch power supply needs to be set to be in constant current output in the first stage and constant power output in the second stage, the output current I1 of the first current source is a fixed value in the first stage and is irrelevant to the first detection signal, and the isolated switch power supply performs constant current output. The output current I1 of the first current source is inversely proportional to the first detection signal Vdem in the second stage, and the first adjustment parameter K is a fixed positive value, so as to perform constant power output.
The utility model provides a primary side control circuit and isolated switching power supply can set for different output current constant current values according to isolated switching power supply's output voltage to effectively realize isolated switching power supply's high accuracy constant power output or adjustable constant current output.
The above description and applications of the present invention are illustrative and are not intended to limit the scope of the invention to the above described embodiments. In the specification, "output current" and "output voltage" which are not explicitly described are the output current and the output voltage of the isolated switching power supply. The descriptions related to the effects or advantages mentioned in the embodiments may not be reflected in the experimental examples due to the uncertainty of the specific condition parameters, and are not used for limiting the embodiments. Variations and modifications of the embodiments disclosed herein are possible, and alternative and equivalent various components of the embodiments will be apparent to those skilled in the art. It will be clear to those skilled in the art that the present invention may be embodied in other forms, structures, arrangements, proportions, and with other components, materials, and parts, without departing from the spirit or essential characteristics thereof. Other variations and modifications of the embodiments disclosed herein may be made without departing from the scope and spirit of the present invention.
Claims (10)
1. A primary side control circuit for primary side control of an isolated switching power supply, the isolated switching power supply comprising a primary side circuit and a secondary side circuit, the primary side control circuit comprising:
the input end of the charge and discharge circuit is coupled with the first detection signal end to obtain a first detection signal representing the output voltage so as to control the charge amount in unit time in the charge and discharge circuit; the charging and discharging circuit is respectively coupled with a signal end of the primary side inductor median current and a signal end of the secondary side circuit within the demagnetization time so as to control the discharge amount in the charging and discharging circuit within a unit time; and
and the input end of the driving signal generating circuit is coupled with the charging and discharging circuit, and the output end of the driving signal generating circuit is coupled with a main switching tube in the primary side circuit.
2. The primary control circuit of claim 1, wherein the charge and discharge circuit comprises a discharge circuit coupled to a signal terminal of a median current of the primary inductor to control a discharge current, and coupled to a signal terminal of a degaussing time of the secondary circuit to control a discharge time.
3. The primary control circuit of claim 1 wherein said charge and discharge circuit comprises:
a charging circuit coupled to the first detection signal terminal for outputting a charging current according to the first detection signal;
a first capacitor, a first end of which is coupled to the output end of the charging circuit, and a second end of which is coupled to ground; and
and a discharge circuit, a first input end of which is coupled to the first end of the first capacitor, a second input end of which is coupled to the signal end of the demagnetization time of the secondary side circuit, and a third input end of which is coupled to the sampling signal end to receive a sampling signal representing the median current of the primary side inductor, so as to discharge the first capacitor according to the demagnetization time of the secondary side circuit and the sampling signal.
4. The primary control circuit of claim 3 wherein the charging circuit comprises a first current source coupled to the first detection signal terminal to output a charging current based on the first detection signal; the discharge circuit includes:
a first switch, a first end of which is coupled to the first end of the first capacitor, and a switch control end of which is coupled to a signal end of the secondary side circuit during degaussing time;
a second switch tube, the drain of which is coupled to the second end of the first switch;
the non-inverting input end of the operational amplifier is coupled with the sampling signal end, the inverting input end of the operational amplifier is coupled with the source electrode of the second switch tube, and the output end of the operational amplifier is coupled with the control end of the second switch tube; and
a third resistor, a first end of which is coupled to the source of the second switch tube, and a second end of which is coupled to ground.
5. The primary side control circuit of claim 3 wherein the first terminal of the first capacitor is coupled to an input of the drive signal generating circuit, and wherein the primary side control circuit controls the charging process and the discharging process to maintain dynamic balance.
6. The primary control circuit of claim 1, wherein the isolated switching power supply is a flyback switching power supply, the flyback switching power supply includes an auxiliary winding, and the charging and discharging circuit is coupled to the auxiliary winding to obtain the first detection signal.
7. The primary control circuit according to claim 1, wherein a first regulating circuit is further coupled between the charging and discharging circuit and the first detection signal terminal, and the first regulating circuit is coupled to the first regulating parameter and the first detection signal terminal to output a first regulating signal, so as to control a charging amount per unit time in the charging and discharging circuit.
8. The primary side control circuit of claim 7, wherein the charging circuit in the charging and discharging circuit comprises a first current source, and the first regulating circuit controls an output current I1 of the first current source to be positively correlated with K/Vdem, wherein I1 is the output current of the first current source, K is a first regulating parameter, and Vdem is a first detection signal.
9. The primary control circuit of claim 8 wherein the output current of the first current source during the set-up phase satisfies any one of the following three conditions: the output current of the first current source is a fixed value; the output current of the first current source is reduced in a step mode along with the increase of the first detection signal; the output current of the first current source is inversely proportional to the first detection signal.
10. An isolated switching power supply comprising a primary circuit, a secondary circuit and a transformer winding, wherein the primary circuit comprises the primary control circuit of any one of claims 1-9, wherein the primary control circuit is configured to control the switching state of the main switching tube.
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| CN202120387577.8U CN214900668U (en) | 2021-02-20 | 2021-02-20 | Primary side control circuit and isolated switching power supply |
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| CN202120387577.8U CN214900668U (en) | 2021-02-20 | 2021-02-20 | Primary side control circuit and isolated switching power supply |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112886823A (en) * | 2021-02-20 | 2021-06-01 | 深圳市必易微电子股份有限公司 | Primary side control circuit, control method and isolated switching power supply |
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2021
- 2021-02-20 CN CN202120387577.8U patent/CN214900668U/en not_active Withdrawn - After Issue
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112886823A (en) * | 2021-02-20 | 2021-06-01 | 深圳市必易微电子股份有限公司 | Primary side control circuit, control method and isolated switching power supply |
| CN112886823B (en) * | 2021-02-20 | 2024-05-31 | 深圳市必易微电子股份有限公司 | Primary side control circuit, control method and isolated switching power supply |
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