CN112366952B

CN112366952B - Isolated voltage conversion circuit, control circuit thereof and power supply method

Info

Publication number: CN112366952B
Application number: CN202011273190.6A
Authority: CN
Inventors: 俞秀峰; 林官秋; 叶俊
Original assignee: Shenzhen Biyi Microelectronics Co ltd
Current assignee: Shenzhen Biyi Microelectronics Co ltd
Filing date: 2020-11-13
Publication date: 2024-05-31
Anticipated expiration: 2040-11-13

Abstract

The invention provides a secondary side control circuit for an isolated voltage conversion circuit, the isolated voltage conversion circuit, an electronic package and a method for providing multiple output voltages. The secondary side of the isolated voltage conversion circuit comprises a first output circuit, the first output circuit comprises a switching tube, a first end of the switching tube is coupled with the secondary side winding, a second end of the switching tube is coupled with a linear device, a second end of the linear device is used for driving a load, and the secondary side control circuit is used for controlling the switching tube and the linear device. The secondary side control circuit, the isolated voltage conversion circuit, the electronic packaging part and the power supply method can provide multiple output voltages on the secondary side, have good load adjustment rate, and have high efficiency while providing accurate load driving voltage.

Description

Isolated voltage conversion circuit, control circuit thereof and power supply method

Technical Field

The present invention relates to the field of electronics, and in particular, but not exclusively, to an isolated voltage conversion circuit and a secondary side control circuit therefor, an electronic package and a method of providing multiple output voltages.

Background

In electronic power supply systems, it is often necessary to provide different power supplies for different loads in the system. For example, in the field of household appliances, different power supplies are required for different components, such as motors, processing units, etc. One conventional method is to provide separate power supplies for different loads, but this approach has a low integration and high system power supply cost. In order to improve the integration degree of the power supply system and reduce the cost of the power supply, a requirement is provided for the power supply system with multiple outputs.

A power supply method is to set two output circuits on the secondary side of an isolated power supply. Fig. 1 shows an isolated two-way output power supply system. The power supply system comprises a first path of output circuit for providing a first output voltage V1 and a second path of output circuit for providing a second output voltage V2, wherein the voltage V2 is fed back to a primary side control primary side switch through an optocoupler and the like so as to control the second output voltage V2. The voltage V1 is regulated by the linear device LDO to obtain higher output control precision. However, in such a circuit, the output range of the V1 voltage is limited and must be close to the second output voltage V2, otherwise the efficiency of the linear device LDO will be greatly reduced. Meanwhile, the linear device is not suitable for being used in the occasion of larger output current or short circuit, and when the LDO works for a long time and has overlarge working current, the reliability and efficiency of the system are greatly reduced.

In view of this, there is a need to provide a new architecture or control method in order to solve at least some of the above problems.

Disclosure of Invention

The present invention is directed to an isolated voltage conversion circuit, a secondary side control circuit thereof, an electronic package, and a method of providing multiple output voltages.

According to one aspect of the present invention, there is provided a secondary side control circuit for an isolated voltage conversion circuit, wherein the secondary side of the isolated voltage conversion circuit includes a first output circuit including a switching tube having a first end, a second end and a control end, the first end of the switching tube being coupled to a secondary side winding, the second end of the switching tube providing a first output voltage, the secondary side control circuit comprising: the switching tube control circuit is coupled with the control end of the switching tube and used for controlling the on and off states of the switching tube; and the output end of the linear control circuit is coupled with the control end of the linear device, wherein the first end of the linear device is coupled with the second end of the switching tube, and the second end of the linear device is used for providing a load driving voltage for driving a load.

In one embodiment, the secondary side of the isolated voltage conversion circuit further comprises a second output circuit coupled to the secondary side winding, the second output circuit providing a second output voltage for driving a second load.

In one embodiment, the secondary side control circuit further comprises a precision voltage stabilizing source, wherein a first end of the precision voltage stabilizing source is coupled to a light emitter of the optocoupler, the light emitter of the optocoupler is coupled to the second output voltage, a light receiver of the optocoupler is coupled to a primary side control circuit of the isolated voltage conversion circuit for adjusting energy transmitted to the secondary side, and the switching tube control circuit is coupled to the first voltage output end and controls the switching tube based on the first output voltage.

In one embodiment, the linear control circuit includes an over-current/short-circuit protection circuit that outputs an effective over-current protection signal when a signal indicative of an over-current/short-circuit of the linear device is acquired, and the linear control circuit controls the linear device to turn off based on the effective over-current protection signal.

In one embodiment, the linear control circuit further comprises a self-recovery timing circuit, when the overcurrent/short-circuit protection circuit outputs a valid overcurrent protection signal, the self-recovery timing circuit is triggered to start timing, and when a preset time period passes, the self-recovery timing circuit controls the overcurrent/short-circuit protection circuit to stop overcurrent protection.

In one embodiment, the linear control circuit includes an over-current/short-circuit protection circuit, the over-current/short-circuit protection circuit including: a comparison circuit that compares a sampled signal representative of current flowing through the linear device with a threshold signal, the comparison circuit providing an effective comparison signal when the sampled signal is greater than the threshold signal; and the continuous timing circuit counts when the comparison signal is in an effective state, and if the effective state duration of the comparison signal exceeds a preset duration, the overcurrent/short-circuit protection circuit outputs an effective overcurrent protection signal, and the linear control circuit controls the linear device to be turned off based on the effective overcurrent protection signal.

In one embodiment, the linear control circuit further comprises a self-recovery timing circuit which is triggered to start timing when the overcurrent protection signal is switched from the inactive state to the active state, and controls the overcurrent/short-circuit protection circuit to stop overcurrent protection when a preset time period elapses.

In one embodiment, the secondary side control circuit further comprises the linear device.

According to another aspect of the present invention, an isolated voltage conversion circuit includes: the primary circuit comprises a primary switch; the transformer comprises a primary winding and a secondary winding, wherein the primary winding is coupled with a primary switch; the first output circuit comprises a switching tube, the switching tube is provided with a first end, a second end and a control end, the first end of the switching tube is coupled with the secondary winding, and the second end of the switching tube provides a first output voltage; and a secondary side control circuit as in any of the embodiments above.

In one embodiment, the isolated voltage conversion circuit further comprises a second output circuit comprising a diode, an anode terminal of the diode being coupled to the secondary winding, a cathode terminal of the diode providing a second output voltage for driving a second load.

According to yet another aspect of the present invention, an electronic package for a secondary side of an isolated voltage conversion circuit has an input pin and a load drive pin, the electronic package internally comprising: the switch chip is provided with a first end, a second end and a control end, wherein the first end of the switch chip is coupled with the secondary winding through an input pin; and a control chip including an LDO device having a first end and a second end, wherein the first end of the LDO device is coupled to the second end of the switch chip, the second end of the LDO device is coupled to the load driving pin, the control chip further having a switch control output coupled to the control end of the switch chip.

In one embodiment, the electronic package further has: a first voltage output pin coupled to a second end of the switch chip; a power supply pin, which is internally coupled with a power supply end of the secondary side control chip and externally coupled with a second voltage output end of the isolated voltage conversion circuit; and a ground pin coupled to the secondary side reference ground.

In one embodiment, the electronic package further has a first voltage output pin coupled to the second end of the switch chip; a power supply pin, which is internally coupled with a power supply end of the secondary side control chip and externally coupled with a second voltage output end of the isolated voltage conversion circuit; and a ground pin coupled to the secondary side reference ground; the feedback pin is internally coupled with the feedback end of the secondary side control chip and externally coupled with the first voltage output end through the sampling circuit; the optical coupler is connected with the pin, internally coupled with the controllable voltage stabilizing source in the secondary side control chip, externally coupled with the first end of the optical coupler, and the second end of the optical coupler is coupled with the second voltage output end; and a reference pin internally coupled to a reference terminal of the controllable voltage stabilizing source in the secondary side control chip.

According to yet another aspect of the present invention, a method of providing a multiplexed output voltage in an isolated voltage conversion circuit includes: providing a first output voltage at a first voltage output end through a switching tube at a secondary side; providing a second output voltage at a second voltage output terminal of the secondary side; and coupling a first terminal of the linear device to the first voltage output terminal, providing a load driving voltage to a second terminal of the linear device, and controlling a conduction degree of the linear device based on the load driving voltage.

In one embodiment, the method further comprises enabling protection of the linear device when the linear device is over-current for a preset period of time.

In one embodiment, the method further comprises stopping protection of the linear device after a second predetermined period of time has elapsed after the protection mechanism is activated.

In one embodiment, the first output voltage is regulated by controlling a switching tube, which in turn regulates the load drive voltage.

The secondary side control circuit, the isolated voltage conversion circuit, the electronic package and the method for providing the multi-output voltage provided by the invention can provide the multi-output voltage on the secondary side, have better load adjustment rate and have higher efficiency while providing accurate load driving voltage.

Drawings

FIG. 1 illustrates an isolated two-way output power supply system;

FIG. 2 shows a schematic diagram of an isolated voltage conversion circuit according to an embodiment of the invention;

FIG. 3 illustrates an isolated voltage conversion circuit according to an embodiment of the invention;

FIG. 4 shows a schematic diagram of an over-current/short-circuit protection circuit according to an embodiment of the invention;

FIG. 5 shows a schematic diagram of an over-current/short-circuit protection circuit according to another embodiment of the invention;

FIG. 6 shows a schematic diagram of an electronic package according to an embodiment of the invention;

FIG. 7 shows a schematic diagram of an isolated voltage conversion circuit according to an embodiment of the invention; and

Fig. 8 is a flowchart of a method for providing multiple output voltages in an isolated voltage conversion circuit according to an embodiment of the invention.

Detailed Description

For a further understanding of the present invention, preferred embodiments of the invention are described below in conjunction with the examples, but it should be understood that these descriptions are merely intended to illustrate further features and advantages of the invention, and are not limiting of the claims of the invention.

The description of this section is intended to be illustrative of only a few exemplary embodiments and the invention is not to be limited in scope by the description of the embodiments. Combinations of the different embodiments, and alternatives of features from the same or similar prior art means and embodiments are also within the scope of the description and protection of the invention.

"Coupled" or "connected" in the specification includes both direct and indirect connections. An indirect connection is a connection via an intermediary, such as a connection via an electrically conductive medium, such as a conductor, where the electrically conductive medium may contain parasitic inductance or parasitic capacitance, or may be a connection via an intermediary circuit or component described in the embodiments of the specification; an indirect connection may also include a connection via other active devices or passive devices, such as a connection via circuits or components such as signal amplification circuits, follower circuits, etc., which may perform the same or similar functions. "plurality" or "multiple" means two or more.

Fig. 2 shows a schematic diagram of an isolated voltage conversion circuit according to an embodiment of the invention. The isolated voltage conversion circuit comprises a primary side circuit, a transformer T1 and a secondary side circuit. Wherein the primary circuit comprises a primary switch Qp. The transformer T1 includes a primary winding L1 and a secondary winding L2, wherein the primary winding L1 is coupled to a primary switch Qp. The secondary side circuit includes a first output circuit, a second output circuit, and a secondary side control circuit 20. Wherein the first output circuit comprises a diode D1 and a switching tube Q1. The switching tube Q1 has a first end, a second end and a control end, wherein the first end of the switching tube Q1 is coupled with the secondary winding L1 through a diode D1, and the second end of the switching tube Q1 provides a first output voltage V1. In another embodiment, diode D1 may not be included. The second output circuit and the first output circuit are coupled in parallel and then are coupled with the secondary winding L2. In another embodiment, the first output circuit and the second output circuit may each be coupled to the first secondary winding and the second secondary winding. The second output circuit comprises a diode D2 for providing a second output voltage V2.

The secondary side control circuit 20 includes a linear device 21, a switching tube control circuit 22, and a linear control circuit 23. The linear device 21 is also referred to as LDO device 21. Wherein a first terminal of the LDO device 21 is coupled to a second terminal of the switching transistor Q1 for receiving the first output voltage V1, a control terminal voltage of the LDO device 21 is controlled by the linear control circuit 23, and a second terminal of the LDO device 21 provides a load driving voltage V3 for driving a load.

The switching tube control circuit 22 is coupled to the control terminal of the switching tube Q1, and provides a switching control signal Ctrl1 for controlling the on and off states of the switching tube Q1. In one embodiment, the switching tube control circuit 22 is configured to control the switching tube Q1 based on the first output voltage V1, for example, when the primary side switch Qp is turned off, to control the switching tube Q1 to be in an off state, the secondary side winding L2 freewheels the second output circuit, and when the first output voltage V1 is lower than a preset threshold, the switching tube control circuit 22 turns on the switching tube Q1 to supply power to the first output circuit, so as to implement regulation of the first output voltage V1, while the second output voltage V2 is fed back to the primary side through an isolated feedback circuit such as an optocoupler, and the energy transferred to the secondary side is controlled by controlling the primary side switch Qp to regulate the second output voltage V2. In another embodiment, the switching tube control circuit 22 controls the switching tube Q1 based on the second output voltage V2, when the secondary side starts freewheeling, the switching tube Q1 is in a conducting state to supply power to the first output circuit, and when the second output voltage V2 of the second output circuit is lower than a preset threshold value, the switching tube Q1 is disconnected to supply power to the second output circuit for adjusting the voltage of the second output voltage V2, and meanwhile, the first output voltage V1 is fed back to the primary side through the isolation feedback circuit, and the adjustment is achieved by controlling the primary side switch Qp. The switching tube control circuit 22 may also have other control modes. The output terminal of the linear control circuit 23 provides a second control signal Ctrl2 to the control terminal of the linear device 21 for controlling the degree of conduction of the linear device 21. Preferably, the linear control circuit 23 is coupled to the second terminal of the LDO device 21 for obtaining the load driving voltage V3, and adjusts the second control signal Ctrl2 based on the load driving voltage V3. In one embodiment, the linear control circuit 23 includes an error amplifying circuit having a first output terminal receiving the load driving voltage V3, a second terminal coupled to the reference voltage, and an output terminal providing the second control signal Ctrl2. In one embodiment, the reference voltage is adjustable.

In this way, by controlling the switching tube Q1 to be turned on and off, the first output voltage V1 can be regulated to a voltage different from the second output voltage V2, while the load driving voltage V3 suitable for the use of a specific component can be provided to the load by the regulation of the linear device 21 on the basis of the first output voltage V1. The second output voltage V2 and the precisely controlled load driving voltage V3 may supply power for different components in the same appliance. By such a topology, accurate control of the load drive voltage can be achieved. Meanwhile, since the first output voltage V1 is adjustable, as adjusted by the setting of the sampling resistor shown in fig. 3, the voltage difference between the load driving voltage V3 output by the LDO device 21 and the input voltage V1 thereof can be controlled at a lower level, so that the loss is low and the system has higher efficiency. The low power consumption of the linear devices is easily integrated inside the control chip 20, further simplifying the architecture of the system.

In the embodiment shown in fig. 2, the secondary side of the isolated voltage conversion circuit comprises a first output circuit providing a voltage V1 and a second output circuit providing a voltage V2. In another embodiment, the isolated voltage conversion circuit includes a switching tube Q1 and LDO device 21, but does not include a second output circuit that provides a second output voltage V2. Wherein LDO device 21 generates a load driving voltage V3 based on a first output voltage V1 provided by switching transistor Q1 to provide an accurate driving voltage to the load. In further embodiments, the secondary side of the isolated voltage conversion circuit may further include other output circuits in addition to the first and second output circuits for coupling the secondary side windings to provide a greater number of output voltages. Wherein the first output voltage V1 can also be used to power a load and is suitable for driving a larger load.

In the embodiment shown in fig. 2, the secondary side control circuit 20 is fabricated on a semiconductor substrate to form a chip, wherein the secondary side control circuit chip includes the linear device 21. In another embodiment, the secondary side control circuit 20 may not include the LDO device 21, e.g., the secondary side control circuit 20 is fabricated on a semiconductor substrate, and the LDO device 21 is a discrete device.

In the embodiment shown in fig. 2, the isolated voltage conversion circuit comprises a flyback voltage conversion circuit. In further embodiments, the isolated voltage conversion circuit may have other topologies, such as may include a forward voltage conversion circuit.

In the embodiment shown in fig. 2, the transformer T1 comprises a secondary winding L2. In another embodiment, the transformer T2 may also include two secondary windings, whose common terminals are respectively coupled to the anode of the diode D1 of the first output circuit and the anode of the diode D2 of the second output circuit, and whose common terminals are both coupled to the secondary ground.

Fig. 3 shows an isolated voltage conversion circuit according to an embodiment of the invention. The isolated voltage conversion circuit comprises a primary side circuit, a transformer T1 and a secondary side circuit. The primary circuit includes a primary switch Qp and a primary control circuit 31 that controls the primary switch Qp. The transformer T1 includes a primary winding L1 and a secondary winding L2, wherein a first end (a synonym end) of the primary winding L1 is coupled to an input end of the isolated voltage conversion circuit for receiving a dc input voltage source, another end (a synonym end) of the primary winding L1 is coupled to a first end of the primary switch Qp, and another end of the primary switch Qp is coupled to a primary ground. The first end (the same name end) of the secondary winding L2 is coupled with the anode of the diode D1 of the first output circuit and the anode of the diode D2 of the second output circuit, and the second end (the different name end) of the secondary winding is connected with the secondary ground. The secondary side circuitry includes a first output circuit, a second output circuit, a secondary side control circuit 30, an isolated feedback loop, a sampling circuit, and the like. The first output circuit comprises a diode D1, a switching tube Q1 and a first output capacitor C1. The second output circuit includes a diode D2 and a second output capacitor C2. The isolation feedback circuit comprises an optical coupler and an auxiliary resistor and capacitor, wherein the optical coupler comprises a light emitter positioned on the secondary side and a light receiver positioned on the primary side. The first output capacitor C1 is coupled to the second end of the switching tube Q1. The second output capacitor C2 is coupled to the cathode of the diode D2. The third output capacitor C3 is coupled to the second terminal of the LDO device 32 in the secondary side control circuit 30 for providing a load driving circuit. The other end of each capacitor C1, C2 and C3 is coupled to the secondary side ground, and is used for filtering the first output voltage V1, the second output voltage V2 and the load driving voltage V3 respectively. In further embodiments, capacitors C1 and C2 may also be included in the load driven by each of voltages V1, V2, and V3.

The first output circuit includes a switching tube Q1, a first end of the switching tube Q1 is coupled to the secondary winding through a diode D1, a second end of the switching tube Q1 provides a first output voltage V1, and a control end of the switching tube Q1 is coupled to a switch control output GATE of the secondary control circuit 30. In the illustrated embodiment, the switching tube Q1 comprises a Metal Oxide Semiconductor Field Effect Transistor (MOSFET), wherein a drain terminal of the switching tube Q1 is coupled to a cathode of the diode D1 to further couple to the secondary winding L2, and a source terminal of the switching tube Q1 provides the first output voltage V1. The second output circuit includes a diode D2 coupled to the secondary winding L2, and provides a second output voltage V2 for driving a second load. When the primary switch Qp is turned off, if the switching tube Q1 is in an on state, the secondary freewheeling current charges the first output capacitor C1 through the diode D1 and the switching tube Q1, and the first output voltage V1 increases. When the switching tube Q1 is turned off, the secondary side freewheel current charges the second output capacitor C2 through the diode D2.

The control circuit 30 includes an LDO device 32, a linear control circuit 35, and a switching tube control circuit 36. The first terminal of the LDO device 32 is coupled to the source of the switching transistor Q1, the second terminal of the LDO device provides the load driving voltage V3, and the conduction degree of the LDO device 32 is controlled by the linear control circuit 35. The output terminal of the linear control circuit 35 is coupled to the control terminal of the LDO device 32, for controlling the conduction degree of the LDO device 32. The linear control circuit 35 includes an error amplifying circuit EA and a protection circuit 37. The non-inverting input terminal of the error amplification circuit EA receives the first reference signal Vref1, the inverting input terminal of the error amplification circuit EA is coupled to the second terminal of the LDO device 32 for receiving the load driving voltage V3, and the output terminal of the error amplification circuit is coupled to the control terminal of the LDO device 32, and the LDO device 32 is used for controlling the load driving voltage V3 at the voltage level indicated by the first reference signal Vref 1. The load driving voltage V3 controlled by the linear device 32 has a more accurate regulation level than the first output voltage V1 and the second output voltage V2. In one embodiment, the first reference signal Vref1 is a low-pass filtered signal or a timing sampling signal of the first output voltage V1, and the load driving voltage V3 is regulated by adjusting the resistance value of the sampling resistor coupled to the first voltage output terminal V1 while the load driving voltage V3 is stably controlled, so that the linear device LDO device 32 has the lowest power consumption.

The protection circuit 37 is used for controlling the linear control circuit 35 to pull down the voltage of the control terminal of the LDO device 32 for turning off the LDO device 32 when the abnormal state is detected. Preferably, the protection circuit includes an over-current/short-circuit protection function, in which, when a short-circuit or an over-current event occurs at the second end of the LDO device, i.e., the load driving output terminal V3, the over-current/short-circuit protection circuit 37 obtains a signal indicating that the linear device 32 is over-current/short-circuited, the over-current/short-circuit protection circuit 37 outputs an effective over-current protection signal PT, and the linear control circuit 37 controls the LDO device 32 to be turned off based on the effective over-current protection signal PT. In one embodiment, the over-current/short-circuit protection circuit 37 outputs an active over-current protection signal PT when a sudden drop in the voltage at the second terminal of the LDO device 32 is detected. Thus, the system can protect the LDO device 32, avoid the LDO device 32 to work for a long time under the overlarge current, avoid the LDO device 32 to have higher power consumption, and improve the reliability of the system. The protection circuit 37 may also implement overvoltage protection or over-temperature protection of the LDO device 32, and the like. Preferably, the LDO device 32 is integrated inside the secondary control chip, so that the system can realize various protection without providing additional pins outside the control chip, and has higher system integration level.

The switching tube control circuit 35 is coupled to the control end of the switching tube Q1 through a switching control output terminal GATE, and is used for controlling the on and off states of the switching tube Q1. In the embodiment shown in fig. 3, the switching tube control circuit 35 includes a comparison circuit CP, the non-inverting input terminal of the comparison circuit CP receives the second reference voltage Vref2, and the inverting input terminal of the comparison circuit CP is coupled to the output terminal of the sampling circuit through the feedback terminal FB, wherein the sampling circuit is configured to be coupled to the first voltage output terminal V1. When the feedback voltage of the first output voltage V1 is lower than the reference voltage Vref2, the switching tube control circuit 35 controls the switching tube Q1 to be turned on. In another embodiment, the sampling circuit is coupled to the second voltage output terminal, and the switching tube control circuit 35 controls the switching tube Q1 to be turned off when the second output voltage V2 is lower than the threshold voltage.

Preferably, the supply voltage terminal VDD of the secondary side control circuit 30 is coupled to the second voltage output terminal, and the second output voltage V2 is used for supplying power to the secondary side control circuit 30.

Preferably, secondary side control circuit 30 further includes a precision voltage regulator source 34. The precise voltage stabilizing source 34 and the optocoupler form an isolated feedback circuit for feeding back the voltage signal of the secondary side to the primary side and controlling the primary side switch Qp and thus the energy transferred from the primary side to the secondary side. In one embodiment, precision voltage regulator source 34 is a TL431 device. As shown, the first end of the precision voltage stabilizing source 34 is coupled to the first end of the light emitter of the optocoupler, the second end of the light emitter of the optocoupler is coupled to the second output voltage V2, and the light receiver of the optocoupler is coupled to the primary side control circuit 31 of the isolated voltage conversion circuit for adjusting the energy transmitted to the secondary side. Meanwhile, the first switching tube control circuit 36 is coupled to the first voltage output terminal and controls the switching tube Q1 based on the first output voltage V1. Thus, the first output voltage V1 is controlled primarily by the control loop in the secondary control circuit 30, and the second output voltage V2 is controlled primarily by the isolated feedback circuit. In another embodiment, the first voltage output terminal is coupled to the light emitter of the optocoupler, and the second voltage output terminal is coupled to the input terminal of the switching tube control circuit 36, such that the first output voltage V1 is mainly controlled by the isolated feedback circuit, and the second output voltage V2 is mainly controlled by the control loop of the secondary side control circuit 30.

Fig. 4 shows a schematic diagram of an over-current/short-circuit protection circuit according to an embodiment of the invention. Wherein the over-current/short-circuit protection circuit comprises a comparison circuit 41 for comparing a sampling signal CS representative of the current flowing through the linear device with a threshold voltage Vref3, the comparison circuit 41 providing an effective comparison signal to provide an effective protection signal PT when the sampling signal CS is greater than the threshold signal Vref 3. The over-current/short-circuit protection circuit further includes a self-recovery timer circuit 43 for timing the off-protection state so that the system automatically recovers to a normal state when the fault condition is eliminated, enabling the LDO device to start operation. When the comparison overcurrent protection signal PT is switched from the invalid state to the valid state, the self-recovery timing circuit 43 starts timing, and when the preset time length passes, the self-recovery timing circuit 43 controls the overcurrent/short-circuit protection circuit to stop overcurrent protection, the linear control circuit adjusts the conduction state of the linear device, and the linear device enters a normal working mode. In the illustrated embodiment, the over-current/short-circuit protection circuit further includes a trigger circuit 42 having a set input coupled to the output of the comparison circuit 41 and a reset input coupled to the output of the self-recovery timer circuit 43, and an output providing the over-current protection signal PT. When the comparison circuit 41 indicates that the current flowing through the linear device flows, the comparison signal is switched to an active state, the trigger circuit 42 is set, and the overcurrent protection signal PT is in an active state. When the self-recovery timer circuit 43 overflows, the trigger circuit 42 is reset, the overcurrent protection signal PT is switched to an inactive state for stopping protection and maintaining for a period of time, at this time, if the current flowing through the linear device is recovered to a normal value, the trigger circuit 42 will not be set any more, the linear device enters a normal operation state, and if a short circuit condition continues to exist, the comparator circuit 41 will set the trigger circuit 42 again, and the linear device is turned off. Of course, the trigger circuit 42 may be replaced by other logic circuits.

Fig. 5 shows a schematic diagram of an over-current/short-circuit protection circuit according to another embodiment of the invention. In contrast to the embodiment of fig. 4, the over-current/short-circuit protection circuit of fig. 5 further includes a keep-alive circuit 54. An input terminal of the continuous timing circuit 54 is coupled to the output terminal of the comparing circuit 51, and an output terminal of the continuous timing circuit 54 is coupled to the set input terminal of the trigger circuit 52. When the comparison signal output from the comparison circuit 41 is in an active state, the duration time counting circuit 54 counts time, and if the duration time of the active state of the comparison signal exceeds a preset time period, the overcurrent/short-circuit protection circuit outputs an active overcurrent protection signal PT for performing protection and turning off the linear device. Thus, by providing the keep-alive circuit 54, it is possible to avoid erroneous entry into the protected mode due to an interfering signal.

In one embodiment, the over-current/short-circuit protection circuit may not include the self-recovery timer circuit 53 and the trigger circuit 52, and the output of the continuous timer circuit 54 provides the protection signal PT. The system is restarted by other restart signals.

Fig. 6 shows a schematic diagram of an electronic package according to an embodiment of the invention. The electronic package may be used for the secondary side of an isolated voltage conversion circuit. The inside of the secondary electronic package includes a switch chip 61 and a control chip 62, and the outside of the electronic package has an input pin 631 and a load drive pin 632. In which the switching chip 61 is fabricated with a switching tube Q1 as shown in fig. 2 or 3. The secondary control chip 62 is provided with the secondary control circuit 20 shown in fig. 2 or the secondary control circuit 30 shown in fig. 3. The connection relationship of the switch chip 61 and the secondary side control chip 62 is described below with reference to fig. 2 or 3. The switch chip 61 has a first end, a second end and a control end, wherein the first end of the switch chip 61 is coupled to the secondary winding L2 of the isolated voltage conversion circuit via an input pin 631 (draw). In the illustrated embodiment, the first end of the switch chip 61 is disposed on the back side of the switch chip 61, electrically coupled to the lead frame 64 by a conductive material such as conductive glue and further coupled to an input pin 631 (DRAIN) of the electronic package. In one embodiment, the lead frame 64 includes at least a portion of the input pins 631, i.e., the lead frame 64 and the input pins 631 are integral for increasing the current load capacity. A second terminal of the switch chip 61 provides a first output voltage V1 and is coupled to a first terminal of the LDO device in the control chip 62. The control terminal of the switch chip 61 is coupled to the switch control output terminal of the control chip 62 for receiving the switch tube control signal Ctrl1. The switching tube control signal Ctrl1 may be provided by switching tube control circuitry in the control chip 62. The first terminal of the switch chip 61 may be the drain of the MOSFET Q1 shown in fig. 3, the second terminal of the switch chip 61 may be the source of the MOSFET Q1 shown in fig. 3, and the control terminal of the switch chip 61 may be the gate of the MOSFET Q1 shown in fig. 3. The control chip 62 includes an LDO device 621, wherein a first terminal of the LDO device 621 is coupled to a second terminal of the switch chip 61 for receiving the first output voltage V1, and a second terminal of the LDO device 621 is coupled to a load driving pin 632 for providing the load driving voltage V3. The control terminal of LDO device 621 may be coupled to a linear control circuit via an interconnect within control chip 62. Through such encapsulation, the system structure is simplified, and the method is applicable to realizing multiplexing output of different voltages through simple devices at the secondary side of the isolated voltage conversion circuit, and simultaneously providing the precisely-regulated load driving voltage V3.

Fig. 7 shows a schematic diagram of an isolated voltage conversion circuit according to an embodiment of the invention. The secondary side of the isolated voltage conversion circuit includes an electronic package 70. The electronic package 70 includes a switching chip and a control chip in the interior thereof as shown in fig. 6, wherein the switching chip may include a switching transistor Q1 as shown in fig. 3, and the control chip may include a secondary side control circuit 30 as shown in fig. 3. The exterior of the electronic package 70 has 8 pins as shown, and the electronic package 70 further has a first voltage output pin V1, a power supply pin VDD, a feedback pin FB, an optocoupler connection pin COMP, a reference pin REF, and a ground pin GND in addition to the input pin DRAIN and the load drive pin V3. As shown in fig. 6, the first voltage output pin V1 is coupled to the second end of the switch chip 61, and provides a first output voltage to the outside. The first output voltage V1 may also be used to drive a load. A sampling circuit may be disposed between the first voltage output pin V1 and the feedback pin FB, for obtaining a sampling signal of the first output voltage. The power supply pin VDD is coupled to the power supply end of the secondary control chip, that is, to the power supply end VDD of the secondary control circuit 30 shown in fig. 3, and is coupled to the second voltage output end V2 of the isolated voltage conversion circuit, and the secondary control chip is powered by the second output voltage V2. The feedback pin FB is internally coupled with the feedback end of the secondary side control chip, externally coupled with the first voltage output end V1 through the sampling circuit and used for acquiring a sampling signal of the first output voltage V1. In another embodiment, the electronic package 70 does not include the feedback pin FB, and the feedback terminal of the secondary control chip is directly coupled to the first voltage output terminal V1 inside the electronic package 70. The optocoupler connection pin COMP is coupled to the controllable voltage stabilizing source in the secondary control chip, and is coupled to the first end of the optocoupler 72. The second end of the optocoupler 72 is coupled to the second voltage output end V2, so that the primary side switch Qp is controlled based on the second output voltage V2, and further, the energy output to the secondary side is controlled to realize the adjustment of the second output voltage V2. The reference pin VREF pair is internally coupled with a reference end of a controllable voltage stabilizing source in the secondary side control chip and externally coupled with a voltage dividing resistor. By integrating the controllable voltage stabilizing source in the secondary side control chip, the system integration level is improved. In another embodiment, the controllable regulated source employs an external discrete device, such as TL431, and the electronic package 70 does not include optocoupler connection pin COMP and reference pin VREF. The ground pin GND is coupled to the secondary side ground.

Fig. 8 is a flowchart of a method for providing multiple output voltages in an isolated voltage conversion circuit according to an embodiment of the invention. The method includes coupling a first terminal of a switching tube to the secondary winding at a secondary side of the isolated voltage conversion circuit and providing a first output voltage at a second terminal of the switching tube, wherein the second terminal of the switching tube is used as a first voltage output terminal of the isolated voltage conversion circuit, step 801. The method includes providing a second output voltage at a secondary side of the isolated voltage conversion circuit at step 802, wherein the second output voltage is obtainable by coupling a rectifier tube to the secondary side winding and at an output of the rectifier tube. The method further includes coupling a linear device to the first voltage output terminal to provide a precisely controlled load driving voltage at step 803, and in particular, the first terminal of the linear device may be coupled to the first voltage output terminal, the second terminal of the linear device may provide the load driving voltage, and the precisely controlled load driving voltage may be provided by adjusting the degree of conduction of the linear device. The method may further include turning off the linear device and starting the protection mechanism when the linear device is detected to be over-current for a preset period of time. In one embodiment, after the protection mechanism is started, protection of the linear device is stopped when a second preset time elapses, so that the system can automatically recover. In one embodiment, the method further comprises adjusting the first output voltage by the switching tube based on a need to adjust the load driving voltage, and enabling the on-resistance of the linear device to be at a lower level while precisely controlling the load driving voltage, for keeping the power consumption of the system in a lower state, and improving the system efficiency. In one embodiment, the method further comprises error amplifying the load drive voltage from the timing sample signal of the first output voltage and further controlling the linear device such that the load drive voltage is regulated by adjusting the resistance of a sampling resistor coupled to the first voltage output while maintaining a stable and low power of the load drive voltage.

It will be appreciated by those skilled in the art that the logic controls of the "high" and "low", "set" and "reset", "and" or "," in-phase input "and" anti-phase input "among the logic controls described in the specification or drawings may be interchanged or changed, and that the same functions or purposes as those of the above embodiments may be achieved by adjusting the subsequent logic controls.

The description and applications of the present invention herein are illustrative and are not intended to limit the scope of the invention to the embodiments described above. The relevant descriptions of effects, advantages and the like in the description may not be presented in practical experimental examples due to uncertainty of specific condition parameters or influence of other factors, and the relevant descriptions of effects, advantages and the like are not used for limiting the scope of the invention. Variations and modifications of the embodiments disclosed herein are possible, and alternatives and equivalents of the various components of the embodiments are known to those of ordinary skill 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 assemblies, materials, and components, 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 invention.

Claims

1. A secondary side control circuit for an isolated voltage conversion circuit, wherein the secondary side of the isolated voltage conversion circuit includes a first output circuit, wherein the first output circuit includes a switching tube having a first end, a second end, and a control end, the first end of the switching tube being coupled to a secondary side winding, the second end of the switching tube providing a first output voltage, the secondary side control circuit comprising:

the switching tube control circuit is coupled with the control end of the switching tube and used for controlling the on and off states of the switching tube; and

A linear control circuit having an output coupled to a control terminal of the linear device, wherein a first terminal of the linear device is coupled to a second terminal of the switching tube, the second terminal of the linear device providing a load driving voltage for driving the load,

Wherein the linear control circuit includes an over-current/short-circuit protection circuit, the over-current/short-circuit protection circuit includes:

a comparison circuit that compares a sampled signal representative of current flowing through the linear device with a threshold signal, the comparison circuit providing an effective comparison signal when the sampled signal is greater than the threshold signal; and

And the continuous timing circuit is used for timing when the comparison signal is in an effective state, and outputting an effective overcurrent protection signal by the overcurrent/short-circuit protection circuit when the duration of the effective state of the comparison signal exceeds a preset duration, and controlling the linear device to be turned off by the linear control circuit based on the effective overcurrent protection signal.

2. The secondary side control circuit of claim 1, wherein the secondary side of the isolated voltage conversion circuit further comprises a second output circuit coupled to the secondary side winding, the second output circuit providing a second output voltage for driving a second load.

3. The secondary side control circuit of claim 2, further comprising a precision voltage regulator source, wherein a first end of the precision voltage regulator source is coupled to a light emitter of the optocoupler, the light emitter of the optocoupler is coupled to the second output voltage, a light receiver of the optocoupler is coupled to a primary side control circuit of the isolated voltage conversion circuit for regulating energy transferred to the secondary side, and the switching tube control circuit is coupled to the first voltage output and controls the switching tube based on the first output voltage.

4. The secondary side control circuit of claim 1, further comprising the linear device.

5. The secondary side control circuit of claim 1, wherein the linear control circuit includes an over-current/short-circuit protection circuit that outputs an active over-current protection signal when a signal indicative of an over-current/short-circuit of the linear device is acquired, the linear control circuit controlling the linear device to turn off based on the active over-current protection signal.

6. The secondary side control circuit as claimed in claim 5, wherein the linear control circuit further comprises a self-recovery timing circuit which is triggered to start timing when the overcurrent protection signal is switched from the inactive state to the active state, and which controls the overcurrent/short-circuit protection circuit to stop the overcurrent protection when a preset period of time elapses.

7. An isolated voltage conversion circuit comprising:

the primary circuit comprises a primary switch;

The transformer comprises a primary winding and a secondary winding, wherein the primary winding is coupled with a primary switch;

the first output circuit comprises a switching tube, the switching tube is provided with a first end, a second end and a control end, the first end of the switching tube is coupled with the secondary winding, and the second end of the switching tube provides a first output voltage; and

A secondary side control circuit as claimed in any one of claims 1 to 6.

8. The isolated voltage conversion circuit of claim 7, further comprising a second output circuit comprising a diode having an anode terminal coupled to the secondary winding, a cathode terminal of the diode providing a second output voltage for driving a second load.

9. An electronic package for an isolated voltage conversion circuit secondary having an input pin and a load drive pin, the electronic package comprising internally:

the switch chip is provided with a first end, a second end and a control end, wherein the first end of the switch chip is coupled with the secondary winding through an input pin; and

A control chip comprising an LDO device and a secondary control circuit as claimed in any of claims 1-6, the LDO device having a first terminal and a second terminal, wherein the first terminal of the LDO device is coupled to the second terminal of the switching chip, the second terminal of the LDO device is coupled to the load driving pin, the control chip further having a switch control output coupled to the control terminal of the switching chip.

10. The electronic package of claim 9, further having:

a first voltage output pin coupled to a second end of the switch chip;

A power supply pin, which is internally coupled with a power supply end of the secondary side control chip and externally coupled with a second voltage output end of the isolated voltage conversion circuit; and

The ground pin is coupled to the secondary side reference ground.

11. The electronic package of claim 10, further having:

The feedback pin is internally coupled with the feedback end of the secondary side control chip and externally coupled with the first voltage output end through the sampling circuit;

The optical coupler is connected with the pin, internally coupled with the controllable voltage stabilizing source in the secondary side control chip, externally coupled with the first end of the optical coupler, and the second end of the optical coupler is coupled with the second voltage output end; and

And a reference pin internally coupled to a reference terminal of the controllable voltage stabilizing source.

12. A method of providing a multiplexed output voltage in an isolated voltage conversion circuit employing a secondary side control circuit as claimed in any one of claims 1 to 6, the method comprising:

Providing a first output voltage at a first voltage output end through a switching tube at a secondary side;

providing a second output voltage at a second voltage output terminal of the secondary side; and

A first terminal of the linear device is coupled to the first voltage output terminal, a load driving voltage is provided to a second terminal of the linear device, and a conduction degree of the linear device is controlled based on the load driving voltage.

13. The method of claim 12, further comprising turning off the linear device to initiate protection when the linear device is detected to be over-current for a preset period of time, and stopping protection of the linear device after a second preset period of time has elapsed.

14. The method of claim 12, further comprising adjusting the load drive voltage by adjusting a resistance of a sampling resistor coupled to the first voltage output.