Regulator Circuit

Abstract

The invention relates to a regulator circuit, in particular for a switching power supply section, which has a negative feedback differential amplifier, wherein the negative feedback comprises a voltage divider consisting of a resistor and at least one capacitor between a signal input and an output of the regulator circuit, so that the transfer function corresponds to a PI regulator, wherein a switchable voltage source is provided, the output of which is connected to a reference potential and to an output-side terminal of the capacitor, wherein a threshold circuit is also provided, so that the voltage source is switched on when a first predetermined voltage value of the output voltage is exceeded and when a second predetermined voltage value of the output voltage is not exceeded.

Description

Technical Field

[0001] The present invention relates to a regulator circuit, in particular for a switching power supply section. Background Art

[0002] In order to adjust the output voltage to a predefined setpoint value, a regulator circuit, for example a so-called PI regulator, is provided in conventional switched-mode power supplies, which compares the current output voltage with a predefined setpoint value and generates a manipulated variable therefrom. From the manipulated variable of the regulator circuit, for example by means of a PWM controller, i.e. a control IC, a control signal for a clocked switching element on the primary side of the resonant converter is derived for adjusting the output voltage.

[0003] Conventional real PI controllers have disadvantages when used in switched-mode power supplies due to parasitic properties in the event of classic fault situations: grid failure and feedback, which manifest themselves in particular as overshoots of the output voltage. Summary of the invention

[0004] The object of the present invention is therefore to specify a regulator circuit which has an improved control behavior in the event of a fault.

[0005] According to the invention, this is achieved with a regulator circuit according to claim 1 .

[0006] Advantageous embodiments of the invention are described in the dependent claims. BRIEF DESCRIPTION OF THE DRAWINGS

[0007] The invention is explained in more detail with reference to the drawings.

[0008] For example:

[0009] Figure 1 Schematically showing a regulator circuit according to the present invention,

[0010] Figure 2 A first embodiment of a regulator circuit is shown,

[0011] Figure 3 A second embodiment of the regulator circuit is shown,

[0012] Figure 4 A portion of a switching power supply section with an impedance transformer is shown. DETAILED DESCRIPTION

[0013] according to Figure 1 The regulator circuit comprises an operational amplifier OP, which is connected as a negative feedback differential amplifier, wherein the negative feedback comprises a voltage divider consisting of two resistors R1, R2 and a capacitor C between the two resistors. The voltage divider is inserted at the signal input terminal Uist and the output terminal of the regulator circuit, and the common terminal of the first resistor R1 and the capacitor C is connected to the negative input terminal of the operational amplifier OP, and the voltage rating U soll is applied to the positive input of the operational amplifier OP. Due to this wiring, the transfer function of the regulator circuit corresponds to a PI regulator.

[0014] According to the invention, this conventional regulator circuit is supplemented with a switchable or switchable voltage source U1, the value of which corresponds approximately to the manipulated variable of the OP output voltage in a typical operating point of stable operation. The output of the voltage source is connected to a reference potential MS and an output-side terminal of a capacitor C. Here, the voltage source U1 has a very low impedance compared to the current flowing through the resistors R1 & R2, and acts both as a source and as a sink, with a substantially constant voltage. The switch S of the voltage source is controlled by a threshold circuit in such a way that the voltage source U1 is switched on when a first predetermined voltage value U2 of the output voltage is exceeded and when a second predetermined voltage value U3 of the output voltage is not exceeded.

[0015] By switching on the voltage source, the capacitor C is prevented from discharging in the event of a supply voltage failure or from overcharging in the event of an overload due to feedback, and a rapid and almost oscillation-free transition of the regulator to normal operation is ensured when the fault is removed. In the event that the regulator is not able to establish a balanced regulation state with its output signal, the capacitor is prevented from recharging to the supply limit of the operational amplifier (commonly referred to as saturation).

[0016] The threshold circuit comprises a second and a third differential amplifier K1, K2, wherein the negative input of the second differential amplifier K1 is connected to the second reference voltage source U2, and the positive input of the third differential amplifier is connected to the third reference voltage source U3, the positive input of the second differential amplifier K1 and the negative input of the third differential amplifier K2 are connected to each other and to the output of the regulator circuit. The outputs of the second differential amplifier K1 and the third differential amplifier K2 are led to the input of an OR gate, the output of which controls the switchable voltage source U1 or a bidirectional energized switch that connects the voltage source to the regulation circuit.

[0017] For example, the second differential amplifier K1 and the third differential amplifier K2 can be implemented by means of operational amplifiers.

[0018] from Figure 2 A particularly advantageous implementation variant of the threshold value circuit and the switchable voltage source can be seen in . In this embodiment, the threshold value circuit comprises two transistors TR3 , TR4 in a push-pull connection, whose common collector terminal is connected to the output-side terminal of the capacitor C.

[0019] The common base terminal is connected via the base resistor Rb The common emitter terminal is connected to a switchable or switchable voltage source, which consists of a series resistor R z And the voltage divider of Zener diode Z is formed.

[0020] As in Figure 3 As shown in , the threshold value circuit can also be constructed by means of two diodes D1 and D2 connected in antiparallel. This provides another simple implementation possibility.

[0021] The advantages of the regulator circuit according to the invention come into play in particular when used in a switched-mode power supply.

[0022] In this case of use, it may be advantageous if an impedance converter and an optocoupler are inserted between the regulator circuit and the PWM controller.

[0023] By adding an impedance converter at the output of the operational amplifier, on the one hand, the frequency response of the operational amplifier and the dynamic gain of the transmission path can be improved without adversely affecting the cut-off frequency of the regulator, and on the other hand, the output voltage of the OP regulator is maintained at the voltage level of the reference voltage of the impedance converter in most operating points and is thus not affected by temperature drift and load changes.

[0024] According to Figure 4 In an embodiment, the impedance converter may advantageously include a first series circuit and a second series circuit, wherein the first series circuit is composed of a collector resistor R z , a second transistor TR2 and a second Zener diode Z2, the second series circuit is composed of another collector resistor Rs, a load and a first transistor TR1, wherein the base terminals of the second and first transistors TR1 and TR2 are connected to each other via another resistor Rbl, and the base and collector of the second transistor TR2 are connected to each other.

[0025] The impedance converter has the task of converting the output voltage of the operational amplifier into a current for driving the optocoupler and thus achieving a high gain of the control loop, while the output voltage of the OPV remains at the level of the reference voltage of the impedance converter in most operating points.

[0026] Reference numerals list

[0027] OP Operational Amplifier

[0028] R1, R2, Rb, Rs, Rp, Rz resistors

[0029] C Capacitor

[0030] Uist signal input terminal

[0031] Usoll voltage rating

[0032] Ureg output voltage

[0033] Ul switchable voltage source

[0034] U2, U3 Pre-given voltage value

[0035] K1, K2 differential amplifier

[0036] ≥1 OR gate

[0037] S switch

[0038] Z, Z2 Zener diode

[0039] TR1, TR2, TR3, TR4 transistors

[0040] Dl, D2 diodes.

Claims

1. A regulator circuit, in particular for a switching power supply section, comprising a negative feedback differential amplifier, wherein the negative feedback comprises a voltage divider consisting of a resistor and at least one capacitor between a signal input and an output of the regulator circuit, so that the transfer function corresponds to a PI regulator, characterized in that The capacitor (C) is controlled by a supplementary circuit so that in the event of an uncontrolled fault in the path, the capacitor (C) is not completely discharged but is kept approximately at the potential of at least one operating point, which potential the capacitor has in controlled normal operation.

2. The regulator circuit according to claim 1, characterized in that The output-side capacitor ends are connected to a predetermined voltage source (U1) via active switches and are held there until the fault has subsided and regulation is possible again, wherein the voltage source (U1) essentially has a voltage corresponding to the potential of the capacitor terminals in at least one operating point.

3. The regulator circuit according to claim 1, characterized in that The capacitor (C) is integrated into the control circuit so that the regulation of the path is regulated by the operational amplifier (OP) by a change in the current and the potential of the output-side capacitor terminal is therefore kept essentially at a voltage in a circuit-dependent manner.

4. A regulator circuit, in particular for a switching power supply section, comprising a negative feedback differential amplifier, wherein the negative feedback comprises a voltage divider consisting of a resistor and at least one capacitor between a signal input and an output of the regulator circuit, so that the transfer function corresponds to a PI regulator, characterized in that A switchable voltage source (U1) is provided, the output end of which is connected to a reference potential and an output-side terminal of the capacitor (C), and a threshold circuit (K1, K2) is provided so that when a first predetermined voltage value of the output voltage (U2) is exceeded and when a second predetermined voltage value (U3) of the output voltage is not exceeded, the voltage source (U1) is switched on so that the capacitor terminal is substantially kept at the voltage of the switchable voltage source (U1).

5. The regulator circuit according to claim 4, characterized in that The threshold circuit comprises a second and a third differential amplifier (K1, K2), the negative input of the second differential amplifier (K1) being connected to a first reference voltage source (U2), and the positive input of the third differential amplifier (K2) being connected to a second reference voltage source (U3), the positive input of the second differential amplifier (K1) and the negative input of the third differential amplifier (K2) being connected to each other and to the output of the regulator circuit, and the outputs of the second differential amplifier and the third differential amplifier being led to the input of an OR gate, the output of the OR gate controlling the switchable voltage source (U1).

6. The regulator circuit according to claim 4, characterized in that The threshold value circuit comprises two transistors (TR3, TR4) in a push-pull connection, whose common collector terminal is connected to the output terminal of the capacitor (C), whose common base terminal is connected to the output of the regulator circuit via a resistor (Rb), and whose common emitter terminal is connected to the switchable voltage source (Ul), which is formed by a voltage divider having a resistor (Rz) and a Zener diode (Z).

7. The regulator circuit according to claim 4, characterized in that The threshold circuit includes two diodes (D1, D2) connected in anti-parallel.

8. A switching power supply part, characterized in that: A regulator circuit according to any one of claims 1 to 7 is provided.

9. The switching power supply unit according to claim 8, characterized in that: An impedance transformer and a resistor or a current source are inserted between the regulator circuit and the PWM controller, which results in a varying signal voltage which is conducted into the regulation stage directly or via an optocoupler or other isolated signal transmission medium.

10. The switching power supply unit according to claim 9, characterized in that: The impedance converter comprises a first series circuit, which is composed of a collector resistor (Rs), a second transistor (TR2) and a Zener diode (Z2), a second series circuit is provided, which is composed of a collector resistor (Rs), a load and a first transistor (TR1), and the base terminals of the second and first transistors (TR2, TR1) are connected to each other via a resistor (Rbl), and the base and collector of the second transistor (TR2) are connected to each other.

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