CN214154313U - Isolated voltage sampling device - Google Patents
Isolated voltage sampling device Download PDFInfo
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- CN214154313U CN214154313U CN202022876910.XU CN202022876910U CN214154313U CN 214154313 U CN214154313 U CN 214154313U CN 202022876910 U CN202022876910 U CN 202022876910U CN 214154313 U CN214154313 U CN 214154313U
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Abstract
The utility model discloses an isolated voltage sampling device, the secondary side main power part of a transformer T1 is divided into an upper winding and a lower winding, one is an auxiliary winding N3, and the other is a secondary side main winding N2; the resistor R1 and the filter capacitor C3 form a primary absorption circuit of the sampling circuit part, and one end of the resistor R1 is connected with the same-name end of the secondary main winding N2. And the sampling circuit is connected to a final sampling point through a filter capacitor, a rectifier diode, a charge-discharge capacitor, a discharge resistor, a series resistor and the like. Isolated voltage sampling is carried out through a transformer in a flyback main power topology, an additional sampling winding is not added, the circuit is simple, the cost is low, and the space is saved; the flyback power supply can realize isolated sampling of primary side voltage when working in a continuous discontinuous mode; isolation voltage sampling can be achieved without secondary design of a flyback transformer.
Description
Technical Field
The utility model relates to an isolator power primary voltage sampling technique especially relates to an isolation voltage sampling device.
Background
With the continuous advance of industrialization, the power electronic technology is rapidly developed. Among them, switching power supplies are widely used in the fields of communications, aviation, consumer electronics, and the like, and the technology is becoming mature. System isolation voltage sampling is common in switching power supplies. The existing detection means is that the primary detection and sampling are carried out and then transmitted to a secondary side singlechip through isolated communication. The sampling process involves multiple links such as primary side singlechip power supply, analog-to-digital conversion, isolation unit, communication and the like, so that the circuit is complex, the cost is high, and the design difficulty is high.
At present, the primary voltage of an isolation switch power supply is sampled in the following ways:
mode 1: the voltage is collected from the primary side through the operational amplifier, and the voltage signal is converted into a current signal. The current flows through the linear optocoupler, is sampled from the secondary measurement of the linear optocoupler, enters the singlechip AD and is finally converted into primary output side voltage.
Mode 2: after the primary side voltage is sampled, the primary side slave singlechip AD is used, the primary side slave singlechip AD converts the voltage value and transmits the voltage value to the secondary side master singlechip through isolated CAN communication, and the master singlechip obtains the primary side voltage and then performs related control.
Mode 3: and the voltage on the primary side is sampled and then transmitted to the secondary side through the isolation operational amplifier, and enters an AD port of the singlechip.
The main disadvantages of the prior art described above are: the circuit is complex and the cost is high.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an isolation voltage sampling device.
The utility model aims at realizing through the following technical scheme:
the utility model discloses an isolation voltage sampling device is connected with input filter capacitor C1 at input voltage both ends, and the dotted terminal of transformer T1's primary winding N1 connects at the drain electrode of main power MOSQ1, and main power MOSQ 1's source ground connection, and primary winding N1 is parallelly connected with input filter capacitor C1 after establishing ties main power MOSQ1 ground connection;
the secondary main power portion of transformer T1 is divided into two windings:
one is an auxiliary winding N3, the like name of which is connected with the anode of the output rectifier diode D4, the different name of which is connected with the ground of the secondary side, the cathode of the output rectifier diode D4 is connected with the anode of the output capacitor C8, and the cathode of the output capacitor C8 is grounded;
the other is a secondary side main winding N2, the same name of the secondary side main winding is connected with the anode of an output rectifier diode D1, the different name of the secondary side main winding is connected with the ground of the secondary side, the cathode of the output rectifier diode D1 is connected with the anode of an output capacitor C2, and the cathode of the output capacitor C2 is grounded;
the resistance of the resistor R1 is, the filter capacitor C3 forms a primary absorption circuit of the sampling circuit part, one end of the resistor R1 is connected with the same-name end of the secondary side main winding N2, the other end of the resistor R1 is connected with one end of the filter capacitor C3 and the cathode of the rectifier diode D2, the other end of the filter capacitor C3 is connected with the ground of the sampling circuit, the anode of the rectifier diode D2 is connected with one end of the charge-discharge capacitor C4, the other end of the charge-discharge capacitor C4 is connected with the ground of the sampling circuit, one end of the charge-discharge capacitor C4 connected with the anode of the rectifier diode D2 is simultaneously connected with one end of the discharge resistor R2, the other end of the discharge resistor R2 is connected with the ground of the sampling circuit, the voltage dividing resistor is formed by connecting the resistor R3 and the resistor R4 in series, the other end of the resistor R3 is connected with one end of the discharge resistor R2, the other end of the 3.3.3V power supply of the resistor R4, the middle of the resistor R3 and the resistor R4 is connected with one end of the filter capacitor C5, the final sampling point is connected with the ground of the final sampling point, and the other end of the filter capacitor C5 is connected with the ground of the sampling circuit.
According to the technical scheme provided by the utility model, the isolated voltage sampling device provided by the embodiment of the utility model has the advantages of simple circuit, low cost and space saving; the flyback power supply can realize isolated sampling of primary side voltage when working in a continuous discontinuous mode; isolation voltage sampling can be achieved without secondary design of a flyback transformer.
Drawings
Fig. 1 is a schematic circuit diagram of an isolated voltage sampling apparatus provided by an embodiment of the present invention.
Detailed Description
Embodiments of the present invention will be described in further detail below. Details not described in the embodiments of the present invention belong to the prior art known to those skilled in the art.
The utility model discloses an isolated voltage sampling device, the concrete implementation of its preferred is:
the method comprises the following steps:
an input filter capacitor C1 is connected to two ends of an input voltage, the homonymous end of a primary winding N1 of a transformer T1 is connected to the drain of a main power MOSQ1, the source of the main power MOSQ1 is grounded, and a primary winding N1 is connected in series with the main power MOSQ1 and then is connected with the input filter capacitor C1 in parallel after being grounded;
the secondary main power portion of transformer T1 is divided into two windings:
one is an auxiliary winding N3, the like name of which is connected with the anode of the output rectifier diode D4, the different name of which is connected with the ground of the secondary side, the cathode of the output rectifier diode D4 is connected with the anode of the output capacitor C8, and the cathode of the output capacitor C8 is grounded;
the other is a secondary side main winding N2, the same name of the secondary side main winding is connected with the anode of an output rectifier diode D1, the different name of the secondary side main winding is connected with the ground of the secondary side, the cathode of the output rectifier diode D1 is connected with the anode of an output capacitor C2, and the cathode of the output capacitor C2 is grounded;
the resistance of the resistor R1 is, the filter capacitor C3 forms a primary absorption circuit of the sampling circuit part, one end of the resistor R1 is connected with the same-name end of the secondary side main winding N2, the other end of the resistor R1 is connected with one end of the filter capacitor C3 and the cathode of the rectifier diode D2, the other end of the filter capacitor C3 is connected with the ground of the sampling circuit, the anode of the rectifier diode D2 is connected with one end of the charge-discharge capacitor C4, the other end of the charge-discharge capacitor C4 is connected with the ground of the sampling circuit, one end of the charge-discharge capacitor C4 connected with the anode of the rectifier diode D2 is simultaneously connected with one end of the discharge resistor R2, the other end of the discharge resistor R2 is connected with the ground of the sampling circuit, the voltage dividing resistor is formed by connecting the resistor R3 and the resistor R4 in series, the other end of the resistor R3 is connected with one end of the discharge resistor R2, the other end of the 3.3.3V power supply of the resistor R4, the middle of the resistor R3 and the resistor R4 is connected with one end of the filter capacitor C5, the final sampling point is connected with the ground of the final sampling point, and the other end of the filter capacitor C5 is connected with the ground of the sampling circuit.
Step 1: establishing an isolated voltage sampling device circuit, and connecting a sampling point to an AD pin of the singlechip;
step 2: setting the resistance value of the resistor R1 as R1, the capacitance value of the filter capacitor C3 as C3, the capacitance value of the charge-discharge capacitor C4 as C4, and the resistance value of the discharge resistor R2 as R2, the following relations are provided:
RC time constant τ 1 — R1 × C3, charging time constant τ C — R1 × C4, and discharging time constant τ d — R1 × C4;
and step 3: setting the voltage across the pin 6 of the transformer T1 as Vos, during the period of conducting the main power MOSQ1, the pin 6 of the transformer T1 induces a negative voltage, and the input voltage Vdc of the transformer T1, the number of turns of the primary winding N1 is N1, and the number of turns of the secondary winding N2 is N2, then there is a relation: Vdc/Vos-N1/N2;
and 4, step 4: the current charges a charge-discharge capacitor C4 through a resistor R1, a filter capacitor C3 and a rectifier diode D2, the voltage drop of the rectifier diode D2 is Vf, the voltage of the charge-discharge capacitor C4 is Vc4, Vc4 [ - (Vos + Vf) ] × [1-exp (-T/τ C) ], the charging time T is n × T, wherein n is the cycle number, T is the switching cycle, the cycle number n required by the minimum time for ensuring full charge is not less than 5 τ C/Ton, and Ton is the switching conduction time;
and 5: in the turn-off period of the main power MOSQ1, the discharge time constant τ d > τ c, so that Vc4 is maintained as follows: vc4max ═ Vos + Vf;
step 6: the sampling output voltage Vins calculation formula is as follows: vins [ - (Vdc/N1) × N2+ Vf ] } × R3/(R3+ R4).
The utility model discloses an isolated voltage sampling device utilizes flyback power to monitor voltage once at the secondary side, carries out isolated voltage sampling through the transformer among the flyback main power topology, does not increase extra sampling winding. The isolation characteristic of the main power transformer is fully utilized. And the secondary side is provided with an absorption circuit to ensure that the sampling process is not limited by the flyback operating mode. The problems of high sampling cost and complex circuit of the isolated voltage are solved.
The specific embodiment is as follows:
as shown in fig. 1, the main power is a flyback switching power supply topology. C1 acts as an input filter capacitor and across the input voltage. The dotted terminal of the primary winding N1 of the transformer T1 is connected to the drain of the main power MOS, and the source of the main power MOS is grounded. The N1 series Q1 is connected in parallel with C1 after being grounded. The secondary side main power part is divided into an upper winding and a lower winding. The winding N3 is an auxiliary winding, the same name of the auxiliary winding is connected with the anode of the output rectifier diode D4, and the different name of the auxiliary winding is connected with the ground of the secondary side. The cathode of the rectifier diode D4 is connected with the anode of the output capacitor C8. The cathode of the output capacitor is grounded. The winding N2 is a secondary side main winding, the same name of the winding is connected with the anode of the output rectifier diode D1, and the different name of the winding is connected with the ground of the secondary side. The cathode of the rectifier diode D1 is connected with the anode of the output capacitor C2. The cathode of the output capacitor is grounded.
R1 and C3 form a primary absorption circuit of the sampling circuit part. One end of R1 is connected with the same name end of the main winding N2, and the other end is connected with one end of the filter capacitor C3 and the cathode of the rectifier diode D2. The other end of C3 terminates at the sampled ground. The anode of the rectifying diode D2 is connected to one end of the charging and discharging capacitor C4. The other end of C4 terminates itself at ground. One end of the C4 which is connected with the anode of the diode D2 is simultaneously connected with one end of the discharge resistor R2 and one end of the R3, and the other end of the R2 is connected with the ground of the sampling. The divider resistor is composed of R3 and R4 which are connected in series, one end of R4 is connected with a 3.3V power supply, and the other end is connected with one end of a filter capacitor C5, wherein the end is a final sampling point. The other end of R3 also meets the final sampling point. The other end of C5 terminates the sampled ground.
The parameter design steps are as follows:
step 1: and establishing a circuit as shown in the figure, and connecting the sampling point to an AD pin of the singlechip.
Step 2: the resistance of the resistor R1 is set to R1. The capacitance value of the capacitor C3 is C3. The capacitance value of the capacitor C4 is C4. The resistance of the resistor R2 is R2. R1, R2, C3 and C4 have the following relations: RC time constant τ 1 — R1 × C3, charging time constant τ C — R1 × C4, and discharging time constant τ d — R1 × C4.
And step 3: the voltage across pin 6 of transformer T1 is set to Vos, and negative voltage is induced across pin 6 during MOS conduction. The input voltage Vdc and the number of turns of a primary winding N1 of the T1 is N1, and the number of turns of a secondary primary winding N2 is N2. Then there is the relation: Vdc/Vos-N1/N2.
And 4, step 4: the current passes through R1, C3 and D2 to charge a capacitor C4, the voltage drop of the diode D2 is Vf, the voltage of the capacitor C4 is Vc4, and then Vc4 [ - (Vos + Vf) ] × [1-exp (-t/τ C) ]. The charging time T is n × T, where n is the cycle number and T is the switching cycle. And ensuring that the number n of the cycles required by the minimum time of full charge is more than or equal to 5 tau c/Ton, wherein Ton is the switch conduction time.
And 5: while the MOS transistor Q1 is turned off, the discharge time constant τ d > τ c, so Vc4 remains unchanged. The size is as follows: vc4max ═ Vos + Vf.
Step 6: the sampling output Vins calculation formula is as follows: vins [ - (Vdc/N1) × N2+ Vf ] } × R3/(R3+ R4).
The utility model has simple circuit, low cost and space saving; the flyback power supply can realize isolated sampling of primary side voltage when working in a continuous discontinuous mode; isolation voltage sampling can be achieved without secondary design of a flyback transformer.
The above description is only for the preferred embodiment of the present invention, but the protection scope of the present invention is not limited thereto, and any changes or substitutions that can be easily conceived by those skilled in the art within the technical scope of the present invention are all covered by the protection scope of the present invention. Therefore, the protection scope of the present invention shall be subject to the protection scope of the claims.
Claims (1)
1. An isolated voltage sampling apparatus, comprising:
an input filter capacitor (C1) is connected to two ends of an input voltage, the dotted end of a primary winding (N1) of a transformer (T1) is connected to the drain electrode of a main power MOS (Q1), the source electrode of the main power MOS (Q1) is grounded, and a primary winding (N1) is connected in series with the main power MOS (Q1) and then is connected in parallel with the input filter capacitor (C1) after being grounded;
the secondary main power part of the transformer (T1) is divided into an upper winding and a lower winding:
one is an auxiliary winding (N3), the same name of the auxiliary winding is connected with the anode of the second output rectifier diode (D4), the different name of the auxiliary winding is connected with the ground of the secondary side, the cathode of the second output rectifier diode (D4) is connected with the anode of the second output capacitor (C8), and the cathode of the second output capacitor (C8) is grounded;
the other one is a secondary side main winding (N2), the same name of the secondary side main winding is connected with the anode of a first output rectifier diode (D1), the different name of the secondary side main winding is connected with the ground of the secondary side, the cathode of the first output rectifier diode (D1) is connected with the anode of a first output capacitor (C2), and the cathode of the first output capacitor (C2) is grounded;
the first resistor (R1) and the first filter capacitor (C3) form a primary absorption circuit of the sampling circuit part, one end of the first resistor (R1) is connected with the same-name end of the secondary side main winding (N2), the other end of the first resistor (R1) is connected with one end of the first filter capacitor (C3) and the cathode of the rectifier diode (D2), the other end of the first filter capacitor (C3) is connected with the ground of the sampling circuit, the anode of the rectifier diode (D2) is connected with one end of the charging and discharging capacitor (C4), the other end of the charging and discharging capacitor (C4) is connected with the ground of the sampling circuit, the charging and discharging capacitor (C4) is connected with one end of the anode of the rectifier diode (D2) and simultaneously connected with one end of the discharging resistor (R2), the other end of the discharging resistor (R2) is connected with the ground of the sampling circuit, the voltage dividing resistor (R4) is formed by connecting the second resistor (R3) and the third resistor (R2) in series, and the voltage dividing resistor (R6863) is connected with the other end of the power supply, the middle of the second resistor (R3) and the third resistor (R4) is connected with one end of the second filter capacitor (C5), the end is a final sampling point, and the other end of the second filter capacitor (C5) is connected with the ground of the sampling circuit.
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| CN202022876910.XU CN214154313U (en) | 2020-12-02 | 2020-12-02 | Isolated voltage sampling device |
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| CN202022876910.XU CN214154313U (en) | 2020-12-02 | 2020-12-02 | Isolated voltage sampling device |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
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| CN112366923A (en) * | 2020-12-02 | 2021-02-12 | 北京大华无线电仪器有限责任公司 | Isolated voltage sampling device |
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Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN112366923A (en) * | 2020-12-02 | 2021-02-12 | 北京大华无线电仪器有限责任公司 | Isolated voltage sampling device |
| CN112366923B (en) * | 2020-12-02 | 2024-09-13 | 北京大华无线电仪器有限责任公司 | Isolated voltage sampling device |
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