DE102019206636A1 - Switching power supply - Google Patents

Abstract

The invention relates to a switched-mode power supply (1) comprising a primary-side control module (RB) designed for the primary-side control of the switched-mode power supply (1), a transformer with a primary coil (LP) and at least one secondary coil (LS1, LS2) and, in addition, the following components: a primary signal circuit (R1) designed to generate a primary-side control signal for controlling the switched-mode power supply (1), - a secondary signal circuit (RS), designed to generate a secondary-side control signal for controlling the switched-mode power supply (1), - a switching unit (SE ), designed for the mutual provision of both control signals at a control input (F) of the control module (RB), the switching unit (SE) being designed in such a way that it a) the primary-side control signal in the switch-on phase of the switched-mode power supply (1) to the control input (F) leads and b) leads the secondary-side control signal in the blocking phase of the switched-mode power supply (1) to the control input (F).

Description

The invention relates to a switched-mode power supply, in particular a flyback converter.

Switching power supplies are used to regulate an output voltage, in particular with a galvanic separation of the input and output voltage, with either a primary-side or a secondary-side regulation being used.

One advantage of the primary-side control is that it has the lowest standby consumption. However, one of their disadvantages is that it regulates the power transmitted and not the output voltage. If a switched-mode power supply has several outputs, their output voltages depend on the load distribution. As a rule, the voltages of outputs that are barely loaded rise when other outputs are heavily loaded, whereas the voltage at heavily loaded outputs decreases. If you need a stable output voltage at one of several outputs, regulation on the secondary side is necessary, but this has a higher standby consumption.

DE 10 2004 052 865 A1 describes a switched-mode power supply, with a rectifier arrangement with output terminals for providing a rectified voltage from an input AC voltage, a charge storage arrangement, a series circuit with a primary coil of a transformer and the switching element, which is connected in parallel to the charge storage arrangement, a choke and an inductive with the primary coil coupled first auxiliary coil which are connected in series between an output terminal of the rectifier arrangement and the charge storage arrangement, a secondary circuit with a secondary coil of the transformer and output terminals for providing an output voltage. The capacitive storage element can be connected between a first output of the rectifier arrangement and a reference potential and the series circuit with the choke and the first auxiliary coil can be connected between a second connection of the rectifier arrangement coupled to the reference potential and the capacitive storage element.

The invention is based on the object of specifying an improved switched-mode power supply, in particular a flyback converter, and in particular of achieving a possibility of secondary-side regulation with a stable output voltage and a low standby consumption comparable to the primary regulation.

The invention solves this problem by means of the subjects of the independent claims. The subclaims reproduce preferred embodiments.

• - eine Primär-Signalschaltung, ausgelegt zur Generierung eines primärseitigen Regelsignals zur Regelung des Schaltnetzteils,
• - eine Sekundär-Signalschaltung, ausgelegt zur Generierung eines sekundärseitigen Regelsignals zur Regelung des Schaltnetzteils,
• - eine Schalteinheit, ausgelegt zur wechselseitigen Bereitstellung beider Regelsignale an einem Regeleingang des Regelbausteins, wobei die Schalteinheit dermaßen gestaltet ist, dass sie

1. a) das primärseitige Regelsignal in der Einschaltphase des Schaltnetzteils an den Regeleingang führt und
2. b) das sekundärseitige Regelsignal in der Sperrphase des Schaltnetzteils an den Regeleingang führt.

The switched-mode power supply according to the invention comprises a primary-side control module designed for the primary-side control of the switched-mode power supply, a transformer with a primary coil and at least one secondary coil and also the following components:

• - a primary signal circuit designed to generate a primary-side control signal for controlling the switched-mode power supply,
• - a secondary signal circuit designed to generate a secondary-side control signal for controlling the switched-mode power supply,
• - A switching unit, designed for the mutual provision of both control signals at a control input of the control module, the switching unit being designed in such a way that it

1. a) the primary-side control signal leads to the control input in the switch-on phase of the switched-mode power supply and
2. b) the secondary-side control signal leads to the control input in the blocking phase of the switched-mode power supply.

• - Generierung eines primärseitigen Regelsignals zur Regelung des Schaltnetzteils,
• - Generierung eines sekundärseitigen Regelsignals zur Regelung des Schaltnetzteils,
• - wechselseitige Bereitstellung beider Regelsignale an einem Regeleingang des Regelbausteins, wobei das primärseitige Regelsignal in der Einschaltphase des Schaltnetzteils an den Regeleingang geführt wird und das sekundärseitige Regelsignal in der Sperrphase des Schaltnetzteils an den Regeleingang geführt wird.

A method according to the invention for switching a switched-mode power supply with a primary-side control module designed for primary-side control of the switched-mode power supply, a transformer with a primary coil and at least one secondary coil, comprises the following steps:

• - Generation of a control signal on the primary side to control the switched-mode power supply,
• - Generation of a control signal on the secondary side to control the switched-mode power supply,
• - Mutual provision of both control signals at a control input of the control module, the primary-side control signal being fed to the control input in the switch-on phase of the switched-mode power supply and the secondary-side control signal being fed to the control input in the blocking phase of the switched-mode power supply.

Since this is a control process, the process steps are of course constantly repeated as long as the control is being carried out.

Switching power supplies with a primary-side control module designed for primary-side control of the switching power supply are known to those skilled in the art. They typically include a transformer with a primary coil to which the input voltage is applied during operation and at least one secondary coil to which the Output voltage is tapped. Such switched-mode power supplies often have several secondary coils, which do not necessarily all have to serve as load outputs. Some of the secondary coils can also be used to control the switch mode power supply (and are often referred to as "auxiliary coils"). The secondary circuits can be galvanically isolated from the primary circuit, but can also have a connection to a common reference potential (with one another or together with the primary circuit).

A signal circuit according to the invention is designed to generate a control signal for controlling the switched-mode power supply. In relation to the control signal, the designation “primary side” indicates that a control signal is meant for primary-side control, and “secondary side” that a control signal is meant for secondary-side control. This control signal preferably comprises (or is) a voltage. It is preferred that the control signal on the primary side is a measure for the voltage of the primary circuit and / or that the control signal on the secondary side is a measure of the voltage of a secondary circuit. Since the voltage in the secondary circuit is usually to be regulated very precisely, it is advantageous if at least the secondary-side control signal is based directly on the voltage of the secondary circuit (the voltage can be used directly or, if the control module has such a high or low voltage cannot work, a voltage adjusted by a corresponding constant factor).

Depending on the application, the voltage of the control signal on the primary side and the control signal on the secondary side can be measured at a common reference potential. However, it is also possible to galvanically separate the primary-side control signal and the secondary-side control signal, e.g. by means of another transformer or (especially if the control signals are voltages) by means of an optocoupler. A signal circuit (in particular the secondary signal circuit) can therefore have an optocoupler for galvanic isolation of the control signal. For this purpose, the output voltage of a secondary circuit is preferably measured and a control signal on the secondary side is generated as a function of this voltage by means of the optocoupler.

A signal circuit preferably comprises a voltage divider or a component of a voltage divider (e.g. a resistor). It is entirely possible that the primary signal circuit and the secondary signal circuit “share” a resistance of a voltage divider, whereby a resistance specific for the respective signal circuit is alternately connected in series with the common resistance by means of the switching unit. For this purpose, the switched-mode power supply preferably has a circuit in which, by means of the switching unit, the resistance of the primary signal circuit and / or the secondary signal circuit is connected to a further resistor to form a voltage divider as part of the routing of the control signal to the control input.

The switching unit is designed for the mutual provision of both control signals at a control input of the control module. For the invention, it is important that the primary-side control signal is fed to the control input in the switch-on phase of the switched-mode power supply and the secondary-side control signal is fed to the control input in the blocking phase of the switched-mode power supply. The blocking phase is the phase in which the control module locks, the switch-on phase is the phase in which the control module is switched on. In the event that a control signal is a voltage, “is conducted” means in particular that the control signal in question is electrically connected to the control input. However, it can also be the case, for example, that the control input is a photo element of an optocoupler. In this case, “is guided” can mean that the control signal is a light signal that is fed into the photo element.

"Alternating" here means that the control action takes place alternately. For this purpose, e.g. Signal lines that carry the control signals are alternately routed to the control input, e.g. through a physical connection or separation. However, it is also possible to leave one signal line (or both signal lines) permanently connected to the control input, provided that the control signal in question is such that it has no regulating effect when the other control signal is applied (e.g. 0V is). With such a circuit, however, it must be ensured that a control signal cannot influence the other control loop. This can e.g. can be achieved by suitable switching of a diode.

Another preferred embodiment of a switching unit according to the invention, which is also designed to provide both control signals alternately at a control input of the control module, comprises two physically separate switches, which, however, do not necessarily have to be installed in a common housing. These two switches can have a common control input, but it is particularly preferred that each switch has its own control input, with the control signals for these control inputs also being able to be picked up at different points in the circuit of the switched-mode power supply.

Since the control signal on the secondary side often represents an approximate DC voltage (which should be advantageously controlled by the invention), it is preferred here that the secondary signal circuit Can be (physically) separated from the control input of the control module via the switching element. In contrast, the control signal on the primary side is often greater than the control voltage on in the blocking phase Uf and can therefore also be the control signal at the same time. In this case, the primary signal circuit does not necessarily have to be physically separated from the control input and, in this preferred case, could be continuously connected to the control input, but the secondary signal circuit would have to be physically switched on and off. This can be done, for example, using a transistor that acts as a switch. In the example described here, however, care must be taken to ensure that the primary control signal does not affect the circuit of the secondary signal circuit, as this could cause serious control problems. This can be remedied by a diode, for example, which is connected in such a way that a negative voltage at its cathode during the conducting phase of the primary circuit causes the current required for over- and undervoltage detection from the control input F. but does not affect the secondary signal circuit in the blocking phase of the primary circuit, since the voltage at its cathode is then greater than the control reference voltage Uf _ref at the control input F. .

Since both the primary-side control signal and the secondary-side control signal are fed into the control input of the control module, and there are normally no separate contacts for primary-side and secondary-side control in the control input, it is preferred that both the primary-side control signal and the secondary-side control signal are designed in this way are that they generate a regulation that is comparable to one another (e.g. both voltages in the same voltage range).

Typically, at least two secondary circuits (and thus also at least two secondary coils) are required for the invention, in particular for control modules that require a secondary coil (as an auxiliary coil) for primary-side control. In some cases, e.g. In the case of control modules that receive their control signals on the primary side directly from their output (e.g. the drain of a field effect transistor), at least one secondary coil is required for regulation on the secondary side. In a preferred embodiment, the primary-side and the secondary-side control signal can be generated in a single secondary circuit.

The switching unit preferably comprises at least one semiconductor element, in particular a bipolar transistor or a field effect transistor (“FET”), since very fast switching processes can be implemented with these using very small switching voltages and / or currents.

The primary signal circuit can, however, also have a diode which is connected in such a way that it prevents the secondary-side control signal from the primary circuit from being influenced (see above). In this case, the primary signal circuit can be continuously connected to the control input (at least if the control signal on the secondary side is such that it has a value in the blocking phase that is lower than the voltage value at the cathode of the primary signal circuit diode D3 ). The control signal on the secondary side (which generally represents a direct voltage) can then simply be switched on by the switching unit in the blocking phase and switched off outside of the blocking phase.

The invention basically relates to all switched-mode power supplies, in particular flyback converters, which use a regulating module on the primary side. This can e.g. Be control modules of the series LNK677x, FAN102 or AP9383. In the case of the invention, “primary-side regulation” means that not only the control module is arranged on the primary side of the switched-mode power supply, but that the controller information also comes from the primary circuit. Depending on the configuration of the switched-mode power supply, an AC voltage or a DC voltage can be used as the input voltage.

The primary-side control signal is preferably tapped off at a secondary coil in order to generate it. However, the voltage can also be tapped directly at the output of the control module (MosFet-Drain), at all outputs between the secondary coil and a freewheeling diode in a secondary circuit, or these taps can be combined, at least if each control signal has its own control input.

As an alternative or in addition, the control signal on the secondary side is tapped for its generation at a point at which a voltage is applied which corresponds to the output voltage.

The control signal on the secondary side is preferably generated based on a voltage at a point (possibly tapped at a point) which is located between a diode and a capacitor in a mesh of diode, capacitor and secondary coil. The diode is preferably connected to the capacitor with its cathode. The capacitor is preferably an electrolytic capacitor. Basically you only need information about the voltage on the capacitor of the mesh. It would therefore still be possible in practice to include further components in the relevant secondary circuit, for example filter modules or others could also be built into the secondary circuit. Such a mesh of capacitor, secondary coil and diode can be used in a preferred Embodiment, the primary-side control signal can be generated (removed) at one connection of the diode and the secondary-side control signal generated (removed) at the other connection of the diode, the secondary-side control signal being always taken between the diode and capacitor. It is typically preferred, however, that the two control signals are generated in different secondary circuits.

To ensure an optimal switching process, the switching unit should be fast enough, as the control voltage that can be used for secondary control is only applied in the phase of demagnetization of the transformer in the blocking phase (often only a few microseconds long). A preferred switching unit therefore has a switching time of less than 1 μs, preferably less than 50 ns, in particular less than 10 ns. This could be achieved, for example, by means of field effect transistors. The switching unit therefore preferably comprises bipolar transistors or field effect transistors as a switch.

With regard to overvoltage or undervoltage detection, which is often carried out in parallel and which is usually implemented by current measurement, care should be taken that the switching currents of the switching unit do not influence the currents for overvoltage or undervoltage detection. For this purpose, it is preferred that the switching current for switching the switching unit flows (essentially) via a path in which there are no points used to carry out the measurement for overvoltage or undervoltage detection. Since the corresponding measurement current is usually in the range of a few µA and the gate or base currents of common field effect or bipolar rasistors are higher or similar and the measurement current could be influenced by this, the measurement signals for overvoltage and undervoltage detection are preferred with this Embodiment not or only minimally influenced by the circuit of the switching unit.

The invention combines the advantage of a stable output voltage by means of the secondary control with the advantages of the primary control, such as low standby consumption or indirect input voltage measurement. For example, a high-voltage measuring divider is no longer necessary. The invention also has the advantage that it is possible to switch between primary and secondary control.

• 1: Einen schematischen Aufbau eines Sperrwandlers gemäß dem Stand der Technik,
• 2: Einen schematischen Aufbau eines Sperrwandlers gemäß der Erfindung,
• 3: Ein Blockschaltbild zum erfindungsgemäßen Verfahren,
• 4: Einen zeitlichen Verlauf von relevanten Spannungen und Strömen,
• 5: Einen schematischen Aufbau gemäß eines Beispiels der Erfindung.

The principle of the invention is explained in more detail below with reference to a drawing by way of example. In the drawing show:

• 1 : A schematic structure of a flyback converter according to the prior art,
• 2 : A schematic structure of a flyback converter according to the invention,
• 3 : A block diagram of the method according to the invention,
• 4th : A chronological sequence of relevant voltages and currents,
• 5 : A schematic structure according to an example of the invention.

A circuit diagram for a primarily regulated flyback converter according to the prior art as an example for a switched-mode power supply is shown in 1 shown. Only the components that are most important for function are taken into account here. Chokes, vibration dampers or other assemblies that only serve to improve the function are not shown.

The input voltage Ue is via an input circuit IT applied to the circuit. This input circuit IT can, for example, use a rectifier (with an AC voltage as the input voltage Ue ), Capacitors, diodes or other components. The only important thing here is that a voltage suitable for the flyback converter is applied to the subsequent primary coil LP is applied. A first secondary coil LS ₁ is part of a first secondary circuit comprising a mesh from the first secondary coil LS ₁ a diode D1 and a capacitor C1 . A second secondary coil LS ₂ is part of a second secondary circuit comprising a mesh from the second secondary coil LS ₂ a diode D2 and a capacitor C2 . A load on the contacts of the capacitor can be connected to this second secondary circuit C2 to the output voltage Including be created.

The flyback converter has a primary-side regulation. The voltage divider from the two resistors can be used as the primary signal circuit R1 and R2 be considered.

The regulation is carried out by means of a regulation module RB reached. This rule module has a very simple structure and has an input S. and an exit D. , between which a contact can be made and a rule input F. . In practice, field effect transistors are often used in control modules RB are used are based on the contacts "Source" and "Drain" input S. and exit D. labeled accordingly.

The rule input F. is across the voltage divider with the resistors R1 , R2 with the voltage of the secondary coil LS ₁ (often referred to as "auxiliary voltage winding") connected. Is the one between entrance S. and exit D. lying, integrated (MosFet) switch closed, is at the output of the secondary coil LS ₁ a negative voltage proportional to the input voltage of the transformer. This negative voltage causes a current to flow out of the control input F. and most of the primary regulating Control modules use this to measure the input voltage and thus implement undervoltage and overvoltage detection. If the switch locks, the voltage on the secondary coil remains for the duration of the transformer demagnetization LS ₁ proportional to the live secondary output voltage. If there are several output voltages, it depends on the load distribution and the coupling conditions between the windings which of the voltages is currently in the lead. In any case, this information is used to control the frequency and / or the switch-on time of the control module RB and thus to regulate the transferred power.

2 shows based on the circuit 1 a schematic structure of a preferred flyback converter 1 according to the invention. Here the diode is at the cathode D2 of the second secondary circuit tapped a voltage across the resistor RS. The two resistors can be used here as the primary signal circuit and the secondary signal circuit R1 , RS are considered to have a common resistance R2 divide to form a voltage divider. The respective voltage dividers are set by means of the switching unit SE formed which the resistance R1 the primary signal circuit and the resistor RS of the secondary signal circuit alternate with the resistor R1 connect. It is entirely possible that in practice the second secondary circuit is used as an auxiliary circuit and the load is connected to a third secondary circuit.

In the circuit shown here it would be necessary to have both secondary circuits with a common reference potential GND connect to. This is done using the wire bridge B. . This is shown in dashed lines because it is often desirable to galvanically separate the second secondary circuit. In this case wire jumper could be used B. can be omitted and in place of (or in addition to) resistance RS an optocoupler can be used in the secondary signal circuit.

The switching unit SE is shown here with the circuit symbol of a toggle switch. Since, in practice, fast switching (in the microsecond range or less) is necessary, and mechanical switches are only of limited use for this, the switching unit comprises SE eg two electronic switches (eg field effect transistors) which are connected as changeover switches. The switching unit SE becomes synchronous with the control module RB switched. The usual resistance is used in the switch-on phase R1 switched on and the resistor RS for secondary control switched off. In the blocking phase, resistance RS is added and resistance R1 switched off. That the switching unit SE to the output of the second secondary coil LS ₂ is connected, the synchronicity with the control module RB clarify. This information can also be obtained at other places (e.g. at the first secondary coil LS ₁ or the drain voltage on the control module RB or at the gate of an FET in the control module) and then only needs to be converted into a suitable switching signal. The measuring methods of the control module are particularly important here RB to observe its regulation.

3 shows a block diagram of the method according to the invention for switching a switched-mode power supply as described above, for example.

In step I, a control signal on the primary side is generated for controlling the switched-mode power supply, for example by tapping a voltage on a secondary coil LS ₁ .

In step II, a control signal on the secondary side is generated for controlling the switched-mode power supply, for example by tapping a voltage at the cathode of a diode D2 in a stitch from a secondary coil LS ₂ , a capacitor C2 and the diode D2 which with its cathode with the capacitor C2 is connected (see e.g. 2 ).

In step III, both control signals are provided alternately at a control input F. of the rule module RB , the primary-side control signal in the switch-on phase of the switched-mode power supply 1 and the secondary-side control signal in the blocking phase of the switched-mode power supply 1 to the rule input F. to be led.

Steps I to III are repeated continuously as long as the control is being carried out.

1. 1. Aufmagnetisierung des Transformators (Einschaltphase: Regelbaustein RB leitend, Dioden D1, D2 in den Sekundärstromkreisen sperrend),
2. 2. Entmagnetisierung des Transformators (Sperrphase: Regelbaustein RB sperrend, Dioden D1, D2 in den Sekundärstromkreisen leitend),
3. 3. Transformator magnetfeldfrei (Regelbaustein RB sperrend, Dioden D1, D2 in den Sekundärstromkreisen sperrend).

If you do not consider the transition phases, a flyback converter such as in 2 is shown, in its intended use, essentially three phases:

1. 1. Magnetization of the transformer (switch-on phase: control module RB conductive, diodes D1 , D2 blocking in the secondary circuits),
2. 2. Demagnetization of the transformer (blocking phase: control module RB blocking, diodes D1 , D2 conductive in the secondary circuits),
3. 3. Transformer free of magnetic fields (control module RB blocking, diodes D1 , D2 blocking in the secondary circuits).

In phase 1 , the switch-on phase (see also 4th ), must be from the switching unit SE resistance R1 with the resistance R2 be connected, because in this phase the voltage is at the anode of the diode D1 negative and proportional to the input voltage on the capacitor C1 . This turns the Rule input F. of the rule module RB A negative current is drawn, which is used for overvoltage or undervoltage detection and for input voltage compensation.

In phase 2 (see also 4th ) must then from the switching unit SE the resistance RS with the resistance R2 connected to resistance R1 a voltage would be present in this phase that is in some way proportional to the power requirement of all outputs, which is always different depending on the load conditions. This voltage is therefore disadvantageous for regulation in this phase. However, the invention now takes advantage of the resistor RS the output voltage Including . This is then via the rule module RB well regulated.

In the phase 3 which are only available in intermittent operation (control module RB is only closed again when the demagnetization is completed), it is basically irrelevant for the inventive control how the switch positions of the switching unit SE are.

4th illustrates a time curve of voltages and currents in a flyback converter, as shown in, for example 2 is shown in a non-discontinuous operation (borderline operation). At the very bottom is the current at the output of the control module, here as "drain current" Id labeled, shown. This drain current Id has periodic saw tooth pulses. In the time interval of these sawtooth pulses (in phase 1 P1 ) the voltage at the output of the control module drops, here as "drain voltage" Ud marked, rapidly decreases to zero and increases after the sawtooth pulse (in phase 2 P2 ) to a constant voltage again with an overshoot. The voltage at the control input F. (i.e. the control signal itself), which here as "feedback voltage" Uf is referred to, basically follows the voltage curve of the drain voltage Ud . Whenever the feedback voltage UF and the reference voltage rise Uf _ref is reached, the secondary control signal is switched, an almost constant voltage, which is a measure of the output voltage Including represents that is to be regulated. Alternative to drain voltage Ud is still the tension Uk _D1 at the cathode of the diode D1 shown. This basically has the same curve as the drain voltage Ud and could be used as a switching signal for the switching unit as an alternative to the drain voltage SE be used.

5 Fig. 3 shows a schematic structure according to an example of the invention. The structure is largely the same as that of the 2 with the difference that the second secondary circuit is galvanic from the first secondary circuit via an optocoupler O1 is disconnected (there is no jumper B. ). Again, only those assemblies are shown here that are helpful for understanding, e.g. the protective resistor in front of the light-emitting diode of the optocoupler has been pointed out O1 waived. This light-emitting diode is operated with a voltage that corresponds to the output voltage Including corresponds.

Another difference (independent of the galvanic isolation) is the primary signal circuit R1 , D3 continuously connected to the control input and includes the diode here D3 . This is looking at the waveform in 4th quite possible, since the primary-side control signal in the time interval of the secondary-side control in any case rises to a voltage that is greater than Uf _ref . It only has to be prevented that when the voltage of the secondary-side control signal is switched on, a current flows from the first into the second secondary circuit, which occurs through the diode D3 is reached, which locks here.

Since the output transistor of the optocoupler behaves like a regulated resistor, the voltage is at the tap of the capacitor C1 divided to typically about 2V. When the cathode voltage is from D3 is now greater than 2V, the diode blocks D3 . This is always guaranteed in this example, since in the borderline case a voltage of 2V is applied C1 at the cathode of D3 at least a voltage of 2V + Uk _D1 (Diode forward voltage) is present.

Since the embodiment described in detail above is an example, it can be modified in the usual way by the person skilled in the art to a wide extent without departing from the scope of the invention. In particular, the specific embodiments can also follow in a form other than that described here. Likewise, the switched-mode power supply can be designed in a different form if this is necessary for reasons of space or design. Furthermore, the use of the indefinite article “a” or “an” does not exclude the possibility that the relevant characteristics can be present several times or more than once.

List of reference symbols

1

Flyback converter

B.

Wire bridge

C1, C2

capacitor

D.

output

D1, D2

diode

IT

Input circuit

F.

Rule input

GND

Reference potential

Id

Drain current

LP

Primary coil

LS _1, LS ₂

Secondary coil

O1

Optocoupler

P1

phase 1

P2

phase 2

RB

Rule module

R1, R2,

RS resistance

S.

entrance

SE

Switching unit

Ue

Input voltage

Including

Output voltage

Uf

Feedback voltage

Ud

Drain voltage

Uk _D1

tension

QUOTES INCLUDED IN THE DESCRIPTION

This list of the documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Patent literature cited

• DE 102004052865 A1 [0004]

Claims (10)

Switching power supply (1) comprising a primary-side control module (RB) designed for primary-side control of the switching power supply (1), a transformer with a primary coil (LP) and at least one secondary coil (LS ₁ , LS ₂ ) and, in addition, the following components: - a primary -Signal circuit (R1), designed to generate a primary-side control signal to control the switched-mode power supply (1), - a secondary signal circuit (RS), designed to generate a secondary-side control signal to control the switched-mode power supply (1), - a switching unit (SE), designed for the mutual provision of both control signals at a control input (F) of the control module (RB), the switching unit (SE) being designed in such a way that it a) feeds the primary-side control signal to the control input (F) during the switch-on phase of the switched-mode power supply (1) and b) leads the secondary-side control signal to the control input (F) in the blocking phase of the switched-mode power supply (1). Switching power supply (1) after Claim 1 , characterized in that the primary-side control signal and / or the secondary-side control signal comprises a voltage, in particular the primary-side control signal is a measure for the voltage of the primary circuit and / or the secondary-side control signal is a measure for the voltage of a secondary circuit. Switching power supply (1) after Claim 2 , characterized in that the voltage of the primary-side control signal and the secondary-side control signal is measured to a common reference potential (GND) or that the primary-side control signal and the secondary-side control signal are galvanically separated, preferably by means of an optocoupler. Switching power supply (1) according to one of the preceding claims, characterized in that the primary signal circuit (R1) and / or the secondary signal circuit (RS) comprises at least one resistor (R1, RS) of a voltage divider, the switching power supply (1) preferably has a circuit in which, by means of the switching unit (SE), the resistor (R1, RS) of the primary signal circuit (R1) and / or the secondary signal circuit (RS) is connected to a further resistor as part of the routing of the control signal to the control input ( R2) is connected to a voltage divider. Switching power supply (1) according to one of the preceding claims, characterized in that the switching power supply (1) is a flyback converter (1). Switching power supply (1) according to one of the preceding claims, characterized in that the secondary-side control signal is generated based on a voltage at a point which is between a diode (D1, D2) and a capacitor (C1, C2) in a mesh of diode ( D1, D2), capacitor (C1, C2) and secondary coil (LS ₁ , LS ₂ ), the diode (D1, D2) being connected with its cathode to the capacitor (C1, C2). Switching power supply (1) according to one of the preceding claims, characterized in that the switching unit (SE) has a switching time shorter than 1 µs, preferably shorter than 1 ns, the switching unit (SE) preferably comprising semiconductor elements as a switch. Switching power supply (1) according to one of the preceding claims, characterized in that the inrush current of the switching unit (SE) does not influence the currents for over- and / or undervoltage detection, it being preferred that the switching current for switching the switching unit (SE) essentially via a A different path flows than the parts of the switched-mode power supply used to generate the control signal. Switching power supply (1) according to one of the preceding claims, characterized in that the primary-side control signal is tapped to generate it at a secondary coil, and / or the voltage is tapped directly at the output (D) of the control module (RB). Switching power supply (1) according to one of the preceding claims, characterized in that the secondary-side control signal is tapped to generate it at a point at which a voltage is present which corresponds to an output voltage (Ua) of the switching power supply (1).

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