CN209961890U - Isolated primary side voltage sampling circuit - Google Patents
Isolated primary side voltage sampling circuit Download PDFInfo
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- CN209961890U CN209961890U CN201920616830.5U CN201920616830U CN209961890U CN 209961890 U CN209961890 U CN 209961890U CN 201920616830 U CN201920616830 U CN 201920616830U CN 209961890 U CN209961890 U CN 209961890U
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Abstract
The utility model discloses an isolated primary side voltage sampling circuit belongs to the electron technical field, including transformer T1, primary side circuit, vice limit main output circuit and voltage sampling circuit, solved the primary side and not had the sampling chip, with vice limit control chip sampling circuit and technical problem not altogether, the utility model discloses a gather transformer vice limit voltage, calculate the input voltage, reduce the design degree of difficulty, improve power density, reduce cost.
Description
Technical Field
The utility model belongs to the technical field of the electron, in particular to isolation type primary voltage sampling circuit.
Background
With the rapid development of the switching power supply technology, the use requirement of the switching power supply is higher and higher. Most isolated switching power supplies place the main control chip on the secondary side of the power supply, and the control circuit needs to detect the primary voltage. At present, a common method for detecting the input voltage of a primary side is to add a sampling singlechip to the primary side and transmit the voltage value of the primary side to a secondary side through an isolation unit. However, the power supply of the primary-side singlechip, the isolation unit and the like are involved, so that the cost is increased and the design difficulty is increased.
In order to implement increasingly complex control and protection logic, an isolated power supply system needs to integrate an auxiliary power supply system to supply power to a control system and a driving system on a secondary side. The primary side voltage sampling of the power supply generally adopts a primary side prevention sensor and a single chip microcomputer method, and then is transmitted to the single chip microcomputer of the secondary side through isolated serial port communication, so that the circuit cost is increased.
SUMMERY OF THE UTILITY MODEL
The utility model aims at providing an isolation type primary side voltage sampling circuit has solved the primary side and has not had sampling chip, with vice limit control chip sampling circuit and technical problem not altogether.
In order to achieve the above purpose, the utility model adopts the following technical scheme:
an isolated primary side voltage sampling circuit comprises a transformer T1, a primary side circuit, a secondary side main output circuit and a voltage sampling circuit;
the transformer T1 comprises a primary winding Np, a first secondary winding Ns1 and a second secondary winding Ns, wherein the two ends of the primary winding Np are a pin 1 and a pin 2 of the transformer T1, the two ends of the first secondary winding Ns1 are a pin 3 and a pin 4 of the transformer T1, and the two ends of the second secondary winding Ns are a pin 4 and a pin 5 of the transformer T1;
the primary side circuit comprises a field effect transistor Q1 and a capacitor C5, wherein the S pole of the field effect transistor Q1 is connected with the ground wire AGND of an external switching power supply, the D pole of the field effect transistor Q1 is connected with the 2 pin of a transformer T1, the 1 pin of the transformer T1 is connected with the positive voltage Vin output by the external switching power supply, the G pole of the field effect transistor Q1 is connected with the control signal DRV of the external switching power supply, one end of the capacitor C1 is connected with the ground wire AGND, and the other end of the;
the secondary side main output circuit comprises a diode D2 and a capacitor C4, wherein the anode of the diode D2 is connected with the 3 pin of a transformer T1 and a cathode output power supply V1, the 4 pin of the transformer T1 outputs a ground wire EGND, one end of the capacitor C4 is connected with the ground wire EGND, and the other end of the capacitor C4 is connected with the power supply V1;
the voltage sampling circuit comprises a sampling output terminal Vin _ adc, a resistor R1, a capacitor C1, a diode D1, a capacitor C2, a resistor R2, a resistor R3, a resistor R4 and a capacitor C3, wherein a pin 5 of a transformer T1 is connected with the anode of the diode D1 through a resistor R1, the cathode of a diode D1 is connected with the sampling output terminal Vin _ adc through the resistor R3, the anode of the diode D1 is further connected with a ground line EGND through the capacitor C1, the cathode of a diode D1 is connected with the ground line EGND through the capacitor C2 and the capacitor R2 which are connected in parallel, and the sampling output terminal Vin _ adc is further connected with the ground line 3 through the resistor R4 and the capacitor C3 which are connected in parallel.
Preferably, the external switching power supply is an isolated flyback switching power supply, and the external switching power supply control signal DRV is provided by the isolated flyback switching power supply.
An isolated primary voltage sampling circuit, solved and adopted the diode to keep apart the technical problem of sampling transformer secondary voltage, the utility model discloses a collection transformer secondary voltage calculates input voltage, reduces the design degree of difficulty, reduce cost, the utility model discloses realized accurate primary voltage sampling function through more ingenious inductance principle and peak hold principle under the condition that does not increase extra some costs and circuit logic in integrated auxiliary power system, saved the sampling calculation circuit and some middle isolation chip of the common primary side of trade. The types of system components are simplified, and the cost and the space are saved. Meanwhile, the stability and the easy maintenance of the auxiliary power supply are not lost.
Drawings
Fig. 1 is a circuit diagram of the voltage sampling circuit of the present invention.
Detailed Description
Example 1:
as shown in fig. 1, an isolated primary side voltage sampling circuit includes a transformer T1, a primary side circuit, a secondary side main output circuit, and a voltage sampling circuit;
the transformer T1 comprises a primary winding Np, a first secondary winding Ns1 and a second secondary winding Ns, wherein the two ends of the primary winding Np are a pin 1 and a pin 2 of the transformer T1, the two ends of the first secondary winding Ns1 are a pin 3 and a pin 4 of the transformer T1, and the two ends of the second secondary winding Ns are a pin 4 and a pin 5 of the transformer T1;
the primary side circuit comprises a field effect transistor Q1 and a capacitor C5, wherein the S pole of the field effect transistor Q1 is connected with the ground wire AGND of an external switching power supply, the D pole of the field effect transistor Q1 is connected with the 2 pin of a transformer T1, the 1 pin of the transformer T1 is connected with the positive voltage Vin output by the external switching power supply, the G pole of the field effect transistor Q1 is connected with the control signal DRV of the external switching power supply, one end of the capacitor C1 is connected with the ground wire AGND, and the other end of the;
the secondary side main output circuit comprises a diode D2 and a capacitor C4, wherein the anode of the diode D2 is connected with the 3 pin of a transformer T1 and a cathode output power supply V1, the 4 pin of the transformer T1 outputs a ground wire EGND, one end of the capacitor C4 is connected with the ground wire EGND, and the other end of the capacitor C4 is connected with the power supply V1;
the voltage sampling circuit comprises a sampling output terminal Vin _ adc, a resistor R1, a capacitor C1, a diode D1, a capacitor C2, a resistor R2, a resistor R3, a resistor R4 and a capacitor C3, wherein a pin 5 of a transformer T1 is connected with the anode of the diode D1 through a resistor R1, the cathode of a diode D1 is connected with the sampling output terminal Vin _ adc through the resistor R3, the anode of the diode D1 is further connected with a ground line EGND through the capacitor C1, the cathode of a diode D1 is connected with the ground line EGND through the capacitor C2 and the capacitor R2 which are connected in parallel, and the sampling output terminal Vin _ adc is further connected with the ground line 3 through the resistor R4 and the capacitor C3 which are connected in parallel.
Preferably, the external switching power supply is an isolated flyback switching power supply, and the external switching power supply control signal DRV is provided by the isolated flyback switching power supply.
Example 2:
the isolated primary voltage sampling method described in embodiment 2 is implemented by the isolated primary voltage sampling circuit described in embodiment 1, and includes the following steps:
step 1: establishing an isolated primary voltage sampling circuit, and connecting a sampling output end Vin _ adc to an AD input end of an external controller;
step 2: setting the capacitance value of the capacitor C1 to C1The capacitance C2 has a capacitance value of C2The resistance value of the resistor R1 is R1The resistance value of the resistor R2 is R2The resistance value of the resistor R3 is R3And the resistance of the resistor R4 is R4Then C1、C2、R1、R2、R3And R4The relationship between them is as follows: c1<C2， R1<[(R3+R4)×R2)÷(R3+R4+R2)]，τ1＝R1×C1，τc＝R1×C2，τd＝[(R3+R4)×R2)÷(R3+R4+R2)]×C2；τ1Is RC time constant, τdIs a discharge time constant, τcFor a charging time constant τc，τc<τd；
And step 3: setting the voltage at the 5-pin of the transformer T1 to Vos, during the conduction period of the fet Q1, the relationship between the number of turns of the primary Np of the transformer T1, the positive voltage Vin, the number of turns of the second secondary winding Ns, and the voltage Vos is as follows:
Vin/Vos＝Np/Ns；
and 4, step 4: after voltage Vos passes through R1 and a C1 filter circuit, a capacitor C2 is charged through a diode D1, the voltage drop of the diode D1 is 0.7V, and the voltage at two ends of a capacitor C2 is set to Vc2, then: vc2 ═ (Vos-0.7) x [1-exp (-t/tau)c)]；
And 5: during the turn-off of the FET Q1, the diode D1 isolates the FET, and tauc<τdThen the voltage Vos across the capacitor C2 is unchanged during the off period;
c2 is fully charged after time T, where T is n × T; n ≧ 5 τcTon, T is the switching period of FET Q1, Ton is the Q1 turn-on time; due to discharge time constant τdGreater than the charging time constant τcThereafter the capacitor C2 maintains the maximum voltage Vc2max unchanged: vc2max ═ Vos-0.7;
step 6: the value of the sampled output terminal Vin _ adc is calculated by the following formula:
Vin_adc＝[R4÷(R3+R4)]×Vc2max＝[R4÷(R3+R4)]×(Vin×Ns÷Np-0.7)；
since R3, R4, Ns, Np are constants, Vin _ adc is linear with the input voltage Vin. When the input voltage changes, such as the input voltage rises, C2 continues to charge, keeping the new peak constant after a while. When the input voltage drops, C2 discharges, over time t1After (t)1>＝5τd) The voltage across C2 drops to a new peak and remains unchanged.
And 7: the external controller calculates the values of the positive voltage Vin and the power supply V1 from the sampled output terminal Vin _ adc by the formulas and methods provided in steps 2 to 6.
Preferably, the external controller is an ARM9 controller.
An isolated primary voltage sampling circuit, solved and adopted the diode to keep apart the technical problem of sampling transformer secondary voltage, the utility model discloses a collection transformer secondary voltage calculates input voltage, reduces the design degree of difficulty, reduce cost, the utility model discloses realized accurate primary voltage sampling function through more ingenious inductance principle and peak hold principle under the condition that does not increase extra some costs and circuit logic in integrated auxiliary power system, saved the sampling calculation circuit and some middle isolation chip of the common primary side of trade. The types of system components are simplified, and the cost and the space are saved. Meanwhile, the stability and the easy maintenance of the auxiliary power supply are not lost.
Claims (2)
1. An isolated primary side voltage sampling circuit is characterized in that: the transformer T1, a primary side circuit, a secondary side main output circuit and a voltage sampling circuit are included;
the transformer T1 comprises a primary winding Np, a first secondary winding Ns1 and a second secondary winding Ns, wherein the two ends of the primary winding Np are a pin 1 and a pin 2 of the transformer T1, the two ends of the first secondary winding Ns1 are a pin 3 and a pin 4 of the transformer T1, and the two ends of the second secondary winding Ns are a pin 4 and a pin 5 of the transformer T1;
the primary side circuit comprises a field effect transistor Q1 and a capacitor C5, wherein the S pole of the field effect transistor Q1 is connected with the ground wire AGND of an external switching power supply, the D pole of the field effect transistor Q1 is connected with the 2 pin of a transformer T1, the 1 pin of the transformer T1 is connected with the positive voltage Vin output by the external switching power supply, the G pole of the field effect transistor Q1 is connected with the control signal DRV of the external switching power supply, one end of the capacitor C1 is connected with the ground wire AGND, and the other end of the;
the secondary side main output circuit comprises a diode D2 and a capacitor C4, wherein the anode of the diode D2 is connected with the 3 pin of a transformer T1 and a cathode output power supply V1, the 4 pin of the transformer T1 outputs a ground wire EGND, one end of the capacitor C4 is connected with the ground wire EGND, and the other end of the capacitor C4 is connected with the power supply V1;
the voltage sampling circuit comprises a sampling output terminal Vin _ adc, a resistor R1, a capacitor C1, a diode D1, a capacitor C2, a resistor R2, a resistor R3, a resistor R4 and a capacitor C3, wherein a pin 5 of a transformer T1 is connected with the anode of the diode D1 through a resistor R1, the cathode of a diode D1 is connected with the sampling output terminal Vin _ adc through the resistor R3, the anode of the diode D1 is further connected with a ground line EGND through the capacitor C1, the cathode of a diode D1 is connected with the ground line EGND through the capacitor C2 and the capacitor R2 which are connected in parallel, and the sampling output terminal Vin _ adc is further connected with the ground line 3 through the resistor R4 and the capacitor C3 which are connected in parallel.
2. An isolated primary voltage sampling circuit as defined in claim 1, wherein: the external switch power supply is an isolated flyback switch power supply, and the external switch power supply control signal DRV is provided by the isolated flyback switch power supply.
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975723A (en) * | 2019-04-30 | 2019-07-05 | 南京桐润新能源有限公司 | A kind of isolated original edge voltage sample circuit and its method |
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Cited By (1)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| CN109975723A (en) * | 2019-04-30 | 2019-07-05 | 南京桐润新能源有限公司 | A kind of isolated original edge voltage sample circuit and its method |
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