CN217010339U - Auxiliary output short-circuit protection circuit and open-loop type isolation converter - Google Patents
Auxiliary output short-circuit protection circuit and open-loop type isolation converter Download PDFInfo
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- CN217010339U CN217010339U CN202123208163.3U CN202123208163U CN217010339U CN 217010339 U CN217010339 U CN 217010339U CN 202123208163 U CN202123208163 U CN 202123208163U CN 217010339 U CN217010339 U CN 217010339U
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Abstract
The utility model provides an auxiliary output short-circuit protection circuit and an open-loop isolation converter, wherein the auxiliary output short-circuit protection circuit is applied to the open-loop isolation converter with a linear regulator LDO (low dropout regulator), and comprises an auxiliary winding Nf and an auxiliary diode D2; one end of the auxiliary winding Nf is connected with the anode of an auxiliary diode D2, and the other end of the auxiliary winding Nf is connected with the output ground of the open-loop isolated converter; the cathode of the auxiliary diode D2 is used to connect with the positive output of the open-loop isolated converter. The loop formed by the auxiliary winding Nf and the auxiliary diode D2 is connected in parallel with the output loop of the LDO, and is used to provide a low impedance loop when the output is short-circuited, thereby reducing the overall impedance of the secondary side, so that the primary side transformer driving chip is coupled through the transformer, detects sufficient short-circuit current, and enters a short-circuit protection state.
Description
Technical Field
The present invention relates to the field of circuit technologies, and in particular, to an auxiliary output short-circuit protection circuit and an open-loop isolation converter.
Background
In the application field of micro-power DC-DC isolation converters, namely power-level switching power supply products of 6W and below, a push-pull type/full-bridge type/half-bridge type and the like are commonly used as a primary power topology, a transformer is matched, and a secondary rectifying circuit is combined, so that a DC-DC open-loop circuit with a simple structure can be formed, and the isolation and voltage conversion functions are realized.
With the continuous development of integrated circuits, the trend of IC productization is more and more prominent, many ICs integrating a common primary topology and a control part thereof appear on the market, and the IC is hereinafter referred to as a "transformer driving chip", such a transformer driving chip is specially designed for an open-loop isolation converter, and a short-circuit protection function of the transformer driving chip is to determine whether an output end is short-circuited by detecting a primary current/voltage, so as to provide a protection function.
To further describe the short-circuit protection function, as shown in the functional block diagram of fig. 1, a short-circuit detection mechanism of the transformer driving chip is described:
in the current angle, the output end of the secondary side is short-circuited, the current of the secondary side is increased, the current mapped to the primary side is increased, and when the current of the primary side is increased to a set point, the output short circuit is judged.
And secondly, from the voltage angle, the output end of the secondary side is in short circuit, the voltage of the secondary side winding of the transformer is reduced, correspondingly, the voltage of the primary side winding of the transformer is clamped by the secondary side to be reduced, the voltage of a driving chip of the transformer connected with the primary side winding in series is increased, and when the voltage is increased to a set point, the output short circuit is judged.
The basic principle of the points is similar, namely that the secondary power loop changes due to output short circuit, the state of the primary power loop is influenced through the transformer, and the transformer driving chip judges whether the output short circuit occurs or not by detecting the state change of the primary power loop. For ease of understanding, the following description is presented in terms of electrical current.
Further, the current of the transformer driving chip is defined as follows: rated current Ia, i.e., the current allowed to flow in steady state; the short-circuit trigger current Ib, that is, the short-circuit protection function of the transformer driving chip will be triggered after the current reaches this value, and obviously, the short-circuit trigger current Ib needs to be larger than the rated current Ia; the current range between them is defined as the overload current Ia-b.
The above principles and applications are all associative and consistent with circuit logic for a practitioner.
On the other hand, one significant disadvantage of the open loop circuit is that the output voltage is unregulated, which may follow the input voltage or load variations. In order to realize simple voltage stabilization of a micro-power circuit, a linear voltage stabilizer is often added at the output end of the circuit in the industry for expanding application, as shown in fig. 2, but the voltage stabilization scheme conflicts with a short circuit detection mechanism of a current transformer driving chip, and the specific conditions are as follows:
1. ideally, if the output end is short-circuited, the secondary side current rises sharply and is mapped to the primary side, so that the primary side current rises quickly to reach the short-circuit trigger current Ib of the transformer driving chip, and then the short-circuit protection state is entered.
2. In practical situations, a loop of the secondary side at least comprises a transformer secondary side winding, a rectifying circuit and a PCB (printed Circuit Board) wiring, certain impedance exists in the components, and when the output end is short-circuited, the secondary side current is limited by the impedance and cannot be increased infinitely; if a linear regulator is added to the secondary loop, the impedance of the secondary loop is inevitably increased; when the output end is short-circuited, the short-circuit current of the secondary side loop decreases due to the increase of the loop impedance, and correspondingly, the primary side current decreases along with the increase of the loop impedance.
3. Because the impedance of the linear voltage regulator is relatively large, in practical application, when the output end is short-circuited, the primary side current cannot reach the short-circuit trigger current Ib due to the reduction of the secondary side current, so that the short-circuit protection state cannot be entered, and the overload state with the current Ia-b is maintained all the time.
The transformer driving chip works in an overload state for a long time, abnormal heating conditions can be caused, and even the chip is directly burnt.
Therefore, if a circuit using a transformer driving chip selects a linear voltage regulator as a voltage stabilization expansion scheme, the output short circuit protection function cannot be compatible. Practitioners can only give up this short-circuit protection function or choose from linear regulators with short-circuit protection function, but such linear regulators are usually expensive, which increases the difficulty of model selection besides increasing the application cost.
SUMMERY OF THE UTILITY MODEL
In view of this, the technical problems to be solved by the present invention are: the utility model provides an auxiliary output short-circuit protection circuit and open-loop type isolation converter, under the condition that does not change core device, solve transformer driver chip IC collocation linear regulator LDO and use the back, because secondary impedance grow, and can't get into the problem of short-circuit protection state when the output takes place the short circuit.
The technical scheme adopted by the utility model is as follows:
in a first aspect, an auxiliary output short-circuit protection circuit is provided, including: an auxiliary winding Nf and an auxiliary diode D2; one end of the auxiliary winding Nf is connected with the anode of an auxiliary diode D2, and the other end of the auxiliary winding Nf is used for being connected with the output ground of the open-loop isolated converter; the cathode of the auxiliary diode D2 is used to connect with the positive output of the open-loop isolated converter.
Preferably, the number of turns of the auxiliary winding Nf is less than that of the secondary winding Ns of the open-loop isolated converter.
Preferably, the auxiliary winding Nf is formed by one or more wires connected in parallel.
Preferably, the auxiliary diode D2 is formed by one or more diodes connected in parallel.
Preferably, the converter further comprises a resistor R2, wherein one end of the resistor R2 is connected with the cathode of the auxiliary diode D2, and the other end is used for being connected with the positive output end of the open-loop converter.
In a second aspect, there is provided an open-loop isolated converter comprising: the transformer driving chip IC, the transformer T1, the rectifying circuit, the linear voltage regulator LDO and at least one path of auxiliary output short-circuit protection circuit are arranged; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted end of a primary winding Np of a transformer T1, the second output end of the transformer driving chip IC is connected with the dotted end of the primary winding Np of the transformer T1, and the ground end of the transformer driving chip IC is grounded; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal of the secondary winding Ns of the transformer T1 is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the linear voltage regulator LDO is used as the positive output end of the open-loop isolation converter and is connected with the cathode of the auxiliary diode D2 of each auxiliary output short-circuit protection circuit, and the ground end of the linear voltage regulator LDO is connected with the output ground; the end of the auxiliary winding Nf of each of the auxiliary output short-circuit protection circuits remote from the auxiliary diode D2 is connected to output ground.
In a third aspect, an open-loop isolated converter comprises: the transformer driving circuit comprises a transformer driving chip IC, a transformer T1, a rectifying circuit, a linear voltage regulator LDO, an auxiliary winding Nf and a diode D3; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted end of a primary winding Np of a transformer T1, the second output end of the transformer driving chip IC is connected with the synonym end of the primary winding Np of the transformer T1, and the ground end of the transformer driving chip IC is connected with an output ground; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal of the secondary winding Ns of the transformer T1 is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the linear regulator LDO is connected with the cathode of the diode D3, and the ground end is connected with the output ground; the anode of the diode D3 is connected with the dotted terminal of the auxiliary winding Nf; and the different name end of the auxiliary winding Nf is connected with an output ground.
Compared with the prior art, the utility model has the following beneficial effects:
1. for an open-loop voltage stabilizing circuit (also called an open-loop isolation converter) formed by matching a transformer driving chip with a linear regulator LDO, core devices do not need to be replaced or circuit parameters do not need to be changed, and secondary impedance during short circuit can be reduced by only adding an auxiliary winding Nf and an auxiliary diode D2, so that the short circuit protection function of the transformer driving chip is better realized, the cost is low, the structure is simple, and a product with better cost performance can be obtained.
2. The auxiliary output short-circuit protection circuit only works when the output is short-circuited, does not influence the circuit operation in a non-short-circuit state, and does not cause the circuit performance to be reduced.
Drawings
FIG. 1 is a block diagram of a conventional open-loop circuit in the background art;
FIG. 2 is a schematic block diagram of a conventional open loop circuit added linear regulator LDO in the background art;
FIG. 3 is a schematic block diagram of a first embodiment of an open-loop isolated converter including an auxiliary output short-circuit protection circuit;
figure 4 is a schematic diagram of an open-loop isolated converter according to a second embodiment;
fig. 5 is a schematic diagram of an open-loop isolated converter according to a third embodiment;
fig. 6 is a schematic diagram of an open-loop isolated converter according to a fourth embodiment;
fig. 7 is a schematic diagram of an open-loop isolated converter according to a fifth embodiment.
Detailed Description
The technical solutions in the embodiments of the present invention will be described in detail below with reference to the accompanying drawings in the embodiments of the present invention, which are for illustrative purposes only and are not to be construed as limiting the patent; for the purpose of better illustrating the embodiments, certain features of the drawings may be omitted, enlarged or reduced, and do not represent the size of an actual product; it will be understood by those skilled in the art that certain well-known structures in the drawings and descriptions thereof may be omitted. The technical solution of the present invention is further described below with reference to the accompanying drawings and examples.
First embodiment
As shown in fig. 3, which is a schematic block diagram of an open-loop isolated converter including an auxiliary output short-circuit protection circuit according to the present embodiment, in the present embodiment, an auxiliary output short-circuit protection circuit is provided, including: an auxiliary winding Nf and an auxiliary diode D2; one end of the auxiliary winding Nf is connected with the anode of the auxiliary diode D2, and the other end is used for being connected with the output ground of the open-loop type isolated converter; the cathode of the auxiliary diode D2 is used to connect to the positive output of the open-loop isolated converter.
Specifically, the dotted terminal of the auxiliary winding Nf is connected to the anode of the auxiliary diode D2, and the different-dotted terminal is used for being connected to the output ground of the open-loop isolated converter; an auxiliary output short-circuit loop formed by the auxiliary winding and the auxiliary diode D2 is connected in parallel with an output power loop formed by the transformer T1, the auxiliary winding Ns, the rectifying circuit and the linear voltage regulator LDO; when the output end is short-circuited, the auxiliary loop can provide another low-impedance loop, and the overall impedance of the secondary side is reduced.
In one embodiment, the number of turns of the auxiliary winding Nf is less than the number of turns of the secondary winding Ns of the open-loop isolated converter.
Specifically, the number of turns of the auxiliary winding Nf is less than that of the secondary winding Ns, and on the premise of ensuring that the voltage coupled to the auxiliary winding Nf is greater than the conduction voltage drop of the auxiliary diode D2, the number of turns of the auxiliary winding Nf needs to be reduced as much as possible to reduce unnecessary impedance, generally, but not limited to, the number of turns of the auxiliary winding Nf is 1/5Ns, so that the voltage of the coupled auxiliary winding Nf is lower than that of the secondary winding Ns, and accordingly, the voltage at the point a is lower than that at the point B, so that the auxiliary diode D2 is not turned on in a non-short-circuit state, and stable operation is not affected.
In one embodiment, the auxiliary winding Nf is formed by one or more wires connected in parallel.
In one embodiment, the auxiliary diode D2 is formed by one or more diodes connected in parallel.
In one embodiment, the auxiliary output short-circuit protection circuit further comprises a resistor R2, one end of the resistor R2 is connected to the cathode of the auxiliary diode D2, and the other end is used for connecting to the positive output terminal of the open-loop converter.
The working principle of the embodiment is as follows: when the output end is short-circuited, the point B is short-circuited with the output ground, and the voltage can be quickly pulled to zero potential and is not controlled by the voltage of the secondary winding Ns; because the transformer T1 is a non-ideal device and the loop has a certain impedance, although the inductance of the transformer T1 drops sharply due to a short circuit, in practice, there is a certain coupling voltage, so the voltage at point a is greater than the voltage at point B, the auxiliary diode D2 is turned on, and the auxiliary loop has a short-circuit current flowing through it, and the auxiliary circuit starts to operate; according to the connection mode, the auxiliary loop is connected with the output power loop in parallel, the overall impedance of the secondary side of the auxiliary loop is reduced, the corresponding secondary side current is increased, the current mapped to the primary side is also increased, the primary side current can more easily reach the short-circuit trigger current Ib of the transformer driving chip IC, and the short-circuit protection is triggered; therefore, for the open-loop voltage stabilizing circuit formed by matching the transformer driving chip IC with the linear regulator LDO, the core device does not need to be replaced or the circuit parameters do not need to be changed, the secondary impedance during short circuit can be reduced only by adding the auxiliary winding Nf and the auxiliary diode D2, the short-circuit protection function of the transformer driving chip IC is better realized, the cost is low, the structure is simple, and a product with better cost performance can be obtained.
Second embodiment
As shown in fig. 4, a schematic diagram of an open-loop type isolated converter in this embodiment is provided, where the open-loop type isolated converter includes: the transformer driving chip IC, the transformer T1, the rectifying circuit, the linear regulator LDO and at least one path of auxiliary output short-circuit protection circuit as in the first embodiment; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted terminal of the primary winding Np of the transformer T1, the second output end of the transformer driving chip IC is connected with the dotted terminal of the primary winding Np of the transformer T1, and the ground terminal of the transformer driving chip IC is connected with an output ground; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the LDO serves as the positive output end of the open-loop isolation converter and is connected with the cathode of the auxiliary diode D2 of each auxiliary output short-circuit protection circuit, and the ground end of the LDO is connected with the output ground; the end of the auxiliary winding Nf of each of the auxiliary output short-circuit protection circuits remote from the auxiliary diode D2 is connected to output ground.
Specifically, the transformer driving chip IC can select but is not limited to a push-pull topology, the transformer T1 secondary winding Ns of the transformer T1 primary winding Np is composed of a first winding and a second winding, a dotted end of the first winding is connected with a dotted end of the second winding to form a center tap, the dotted end of the first winding is used as a dotted end of the primary winding Np, and the dotted end of the second winding is used as a dotted end of the primary winding Np; the secondary winding Ns of the transformer T1 is composed of a third winding and a fourth winding, the synonym end of the third winding is connected with the synonym end of the fourth winding to form a center tap, the synonym end of the third winding is used as the synonym end of the secondary winding Ns, and the synonym end of the fourth winding is used as the synonym end of the secondary winding Ns; the isolation converter further comprises an input capacitor C1 and an output capacitor C3, the rectifying circuit is a full-wave rectifying circuit and comprises a diode D11, a diode D12 and a filter capacitor C2; an input end VCC of the transformer driving chip IC is respectively connected with one end of an input capacitor and a center tap of a primary winding Np of a transformer T1 and is used for being connected with an input voltage Vin, a first output end VD2 is connected with a dotted end of the primary winding Np of the transformer T1, a second output end VD1 is connected with a dotted end of the primary winding Np of the transformer T1, and a ground end GND is connected with an output ground; the other end of the input capacitor is grounded; the dotted terminal of the secondary winding Ns of the transformer T1 is connected with the anode of the diode D11, the unlike terminal is connected with the anode of the diode D12, and the center tap is grounded; the cathode of the diode D11 and the cathode of the diode D12 are both connected with the input end of the LDO; one end of the filter capacitor C2 is connected with the input end of the LDO, and the other end is connected with the output ground; the output end of the LDO is used as the positive output end of an open-loop isolation transformer T1 and is respectively connected with one end of an output capacitor C3 and the cathode of an auxiliary diode D2, and the ground end is connected with the output ground; the other end of the output capacitor C3 is connected to output ground; the anode of the auxiliary diode D2 is connected with the dotted terminal of the auxiliary winding Nf; the different name end of the auxiliary winding Nf is connected with the output ground; namely a primary winding Np of a transformer T1, a secondary winding Ns of a transformer T1, a pair of diodes D11 and D12 of an output full-wave rectifying circuit, a filter capacitor C2, an output linear regulator LDO and an output capacitor C3, which are connected in sequence according to a common circuit connection method for DC-DC conversion.
In order to reduce the impedance and ensure that the auxiliary diode D2 is turned on when the auxiliary winding Nf voltage is short-circuited, the number of turns of the auxiliary winding Nf is smaller than that of the secondary winding Ns, and the number of turns can be selected from, but is not limited to, 1/5 Ns.
The working principle is as follows: if the output end uses the linear regulator LDO to realize the voltage stabilization function, when the output end is short-circuited, the loop impedance of the output end is inevitably larger than that before the linear regulator LDO is not used, which causes the secondary short-circuit current to decrease, and the primary current mapped in the past is synchronously influenced, so that the primary current cannot reach the short-circuit threshold Ib (also called short-circuit trigger current Ib) of the transformer driving chip IC, and thus the output end cannot enter the short-circuit protection state, but is maintained in the overload state, and the temperature is abnormally increased or even damaged.
After the auxiliary winding Nf and the auxiliary diode D2 are added, the short circuit loop is formed by the original output power loop, and becomes an output power loop parallel auxiliary loop (also called an auxiliary output short circuit protection circuit). Because the auxiliary loop has fewer turns and only has the auxiliary diode D2, the impedance of the auxiliary loop is smaller than that of the output power loop, and structurally, the auxiliary loop and the output power loop are in a parallel structure, obviously, the total impedance is smaller than that of the prior circuit, so that the secondary short-circuit current is increased, the primary current naturally follows the primary current to be increased, and the short-circuit threshold Ib of the transformer driving chip IC can be easily triggered.
Meanwhile, the voltage at the point A is the voltage of the auxiliary winding Nf coupled with the primary side, and the voltage at the point B is the voltage obtained by subtracting the voltage drop of the diode D11/D12 and the voltage drop of the LDO (low dropout regulator). In the non-short-circuit state, since the number of turns of the auxiliary winding Nf is smaller than that of the secondary winding Ns, the coupling voltage is naturally small, and obviously, the voltage at the point a is smaller than that at the point B, the auxiliary diode D2 is not conducted, and thus, in the normal operating state, the auxiliary loop does not operate. When short circuit occurs, the voltage at the point B is forced to be pulled to the output ground to become zero potential, but because the auxiliary winding Nf, the auxiliary diode D2 and the PCB wiring impedance cannot be zero, the transformer T1 cannot be completely short-circuited, and still has certain electrical characteristics, the point a has coupling voltage and is greater than the voltage at the point B, the number of turns of the auxiliary winding Nf is properly designed, so that the voltage at the point a is greater than the conduction voltage drop of the auxiliary diode D2, and then the auxiliary loop can be conducted to form a short-circuit loop.
Therefore, the auxiliary output short-circuit protection circuit only plays a role in a short-circuit state, and does not influence the circuit operation in normal operation.
Third embodiment
As shown in fig. 5, a schematic diagram of the open-loop isolation converter in this embodiment is different from the first embodiment in that, in this embodiment, the auxiliary output short-circuit protection circuit includes two auxiliary short-circuit circuits, and the two auxiliary output short-circuit protection circuits are respectively connected in parallel with the open-loop isolation converter, so that the two auxiliary output short-circuit protection circuits are both connected in parallel with the output power loop, and impedance during secondary short-circuit can be further reduced, and a primary current can easily reach a short-circuit trigger threshold Ib of a transformer driving chip IC.
Fourth embodiment
Fig. 6 is a schematic diagram of an open-loop isolated converter according to the present embodiment, which is different from the second embodiment, in the present embodiment, on the basis of the first embodiment or the second embodiment, a sub-group loop adding resistor R2 is connected in series in a loop, and an output power loop adding resistor R1 is connected in series in the loop, specifically, one end of a resistor R1 is connected to a cathode of a diode D11, a cathode of a diode D12, and one end of a filter capacitor C2, respectively, and the other end is connected to an input end of a linear regulator LDO; one end of the resistor R2 is connected with the output end of the LDO, and the other end is connected with the cathode of the auxiliary diode D2. On the premise of ensuring that the impedance of the auxiliary loop is smaller than that of the output power loop, the resistors R2 and R1 with appropriate resistance values can appropriately fine-tune the impedance of each loop, so that the impedance of the auxiliary loop is smaller than that of the output power loop, and the beneficial effects can also be obtained.
Fifth embodiment
Referring to fig. 7, fig. 7 is a schematic structural diagram of an open-loop isolated converter according to the present embodiment; in this embodiment, an open-loop isolated converter is provided, comprising: the transformer driving circuit comprises a transformer driving chip IC, a transformer T1, a rectifying circuit, a linear voltage regulator LDO, an auxiliary winding Nf and a diode D3; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted end of a primary winding Np of a transformer T1, the second output end of the transformer driving chip IC is connected with the dotted end of the primary winding Np of the transformer T1, and the ground end of the transformer driving chip IC is grounded; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the linear voltage regulator LDO is connected with the cathode of a diode D3; the cathode of the diode D3 is connected to the dotted terminal of the auxiliary winding Nf; the opposite terminal of the auxiliary winding Nf is connected to the output ground.
Specifically, when the output end is short-circuited, the point B is short-circuited with the output ground, and the voltage can be quickly pulled to zero potential and is not controlled by the voltage of the secondary winding Ns; because the transformer T1 is a non-ideal device and the loop has a certain impedance, although the inductance of the transformer T1 drops sharply due to a short circuit, in practice, there is a certain coupling voltage, and the voltage at point a is greater than the voltage at point B, the diode D3 is turned on, and then the short-circuit current flows through the auxiliary winding Nf and the diode D3, and the auxiliary loop formed by the auxiliary winding Nf and the diode starts to work; according to the connection mode, the auxiliary loop is connected with the output power loop in parallel, the overall impedance of the secondary side of the auxiliary loop is reduced, the corresponding secondary side current is increased, the current mapped to the primary side is also increased, the primary side current can more easily reach the short-circuit current Ib of the transformer driving chip IC, and the short-circuit protection is triggered; therefore, for the open-loop voltage stabilizing circuit formed by the transformer driving chip IC and the LDO, core devices do not need to be replaced or circuit parameters do not need to be changed, the secondary impedance during short circuit can be reduced only by adding the auxiliary winding Nf and the diode D3, the short-circuit protection function of the transformer driving chip IC is better realized, the cost is low, the structure is simple, and a product with better cost performance can be obtained.
The above is only a preferred embodiment of the present invention, and it should be noted that the above preferred embodiment should not be considered as limiting the present invention, and it will be apparent to those skilled in the art that a similar beneficial effect can be obtained by changing the rectification manner and by connecting multiple windings or diodes in parallel, and it will be apparent to those skilled in the art that several modifications and decorations can be made without departing from the spirit and scope of the present invention, and these modifications and decorations should also be considered as the protection scope of the present invention, which is not described in detail by the embodiment herein, and the protection scope of the present invention should be subject to the scope defined by the claims.
Claims (7)
1. An auxiliary output short-circuit protection circuit is applied to an open-loop isolation converter with a linear voltage regulator LDO, and is characterized by comprising an auxiliary winding Nf and an auxiliary diode D2; one end of the auxiliary winding Nf is connected with the anode of an auxiliary diode D2, and the other end of the auxiliary winding Nf is used for being connected with the output ground of the open-loop isolated converter; the cathode of the auxiliary diode D2 is used to connect with the positive output of the open-loop isolated converter.
2. An auxiliary output short-circuit protection circuit according to claim 1, wherein the number of turns of the auxiliary winding Nf is less than that of the secondary winding Ns of the open-loop isolated converter.
3. An auxiliary output short-circuit protection circuit according to claim 1, wherein the auxiliary winding Nf is formed by one or more wires connected in parallel.
4. An auxiliary output short-circuit protection circuit as claimed in claim 1, wherein said auxiliary diode D2 is formed by one or more diodes connected in parallel.
5. An auxiliary output short-circuit protection circuit as claimed in any one of claims 1 to 4, further comprising a resistor R2, one end of the resistor R2 being connected to the cathode of the auxiliary diode D2 and the other end being adapted to be connected to the positive output terminal of the open-loop converter.
6. An open-loop isolated converter, comprising: a transformer driving chip IC, a transformer T1, a rectifying circuit, a linear regulator LDO and at least one auxiliary output short-circuit protection circuit of any one of claims 1-5; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted end of a primary winding Np of a transformer T1, the second output end of the transformer driving chip IC is connected with the dotted end of the primary winding Np of the transformer T1, and the ground end of the transformer driving chip IC is grounded; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal of the secondary winding Ns of the transformer T1 is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the LDO serves as the positive output end of the open-loop isolation converter and is connected with the cathode of the auxiliary diode D2 of each auxiliary output short-circuit protection circuit, and the ground end of the LDO is connected with the output ground; the end of the auxiliary winding Nf of each of the auxiliary output short-circuit protection circuits remote from the auxiliary diode D2 is connected to output ground.
7. An open-loop isolated converter, comprising: the transformer driving circuit comprises a transformer driving chip IC, a transformer T1, a rectifying circuit, a linear voltage regulator LDO, an auxiliary winding Nf and a diode D3; the input end of the transformer driving chip IC is used for being connected with an input voltage Vin, the first output end of the transformer driving chip IC is connected with the dotted end of a primary winding Np of a transformer T1, the second output end of the transformer driving chip IC is connected with the synonym end of the primary winding Np of the transformer T1, and the ground end of the transformer driving chip IC is connected with an output ground; the homonymous terminal of the secondary winding Ns of the transformer T1 is connected with the input terminal of the rectifying circuit, and the synonym terminal of the secondary winding Ns of the transformer T1 is connected with the output ground; the output end of the rectifying circuit is connected with the input end of the LDO; the output end of the linear voltage regulator LDO is connected with the cathode of the diode D3; the anode of the diode D3 is connected with the dotted terminal of the auxiliary winding Nf; and the different name end of the auxiliary winding Nf is connected with an output ground.
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| CN202123208163.3U CN217010339U (en) | 2021-12-20 | 2021-12-20 | Auxiliary output short-circuit protection circuit and open-loop type isolation converter |
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| CN202123208163.3U CN217010339U (en) | 2021-12-20 | 2021-12-20 | Auxiliary output short-circuit protection circuit and open-loop type isolation converter |
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