Figure 1 shows the main circuit, power inverter bridge switch S1 ~ S4, S1, S4, S2, S3 with a driver circuit for PWM control of the bifurcation, the DC input voltage VDC convert area high frequency square wave voltage. Transformer secondary voltage by the full bridge rectifier, filter LF and CF, the output of a stable DC voltage.
Like the S1, S4, S2, S3 period may not be uniform, the phenomenon is the magnetic polarization of the transformer core saturation in destroying the normal function of the circuit, and even lead to failure. To do this, the high frequency transformer primary side to avoid blocking capacitors in series C, bias in magnetic phenomenon. C the value of (a) to decide. LP-E8 EN-EL3 EN-EL3e
If a group of power tubes (like S1 and S4) heat conduction, switching on the power control (S2 and S3) of the voltage applied to the voltage Vcc. dt To reduce the burden on power management, improved employment dv parallel switch at each rotation of the RC circuit to limit the depreciation rate of rise of voltage switch / alter the duration of the change As closure to ensure that the power control in reverse bias safe area of operation. power tube off losses are transferred to the buffer circuit to improve their working conditions. The parameters R and C of the buffer circuit selection should ensure that the process started with the lamp power, the C discharge is completed, the general attitude OR = (3.1 ~ 5.1) t ( a ton of time for the opening of the power tubes). NP-BG1 NP-FC10 NP-FC11
1.2 Closing Short circuit current limit
Closure of the impact of the current limiting circuit with the current limiting resistor in parallel with the circuit of SCR. Finally, the input filter capacitor voltage across the current limiting resistor. When the capacitor voltage reaches a certain value work inverter circuit. other high frequency transformer of the output voltage of the rectifier, the output control signal, triggering SCR conduction, the current limiting resistor is short-circuited. This structure limiting circuit is simple and immediate response without delay. value of the ultimate strength is too small, the current closing time is too great, the energy consumption of a high strength, ultimate strength is too high, the load slowly. Under normal circumstances, limit the strength should be able to guarantee the stability of the closed circuit current 8-10 times. BN-VF707 BN-VF714 BN-VF733
1.3 Driver
Transformer coupled drive circuit driving the transformer are connected to the secondary amplifier circuit complementary push-pull, a better ability to control the shape. Because the bridge circuit, the tube control pulse should be identical, only one processor input dual-output form shown in Figure 2.
In Figure 2, resistors R1 and R2 form a clamping system to ensure that the level of the output pulse, R3 is used to suppress parasitic oscillations. Compared to other forms of circuit training, the auxiliary control loop does not require too much power, simple structure, easy to implement.
control circuit 2
control circuit includes a constant current limiting and protection circuits. control peak current mode to solve their own shortcomings, the design of the compensation circuit of the slope, and the design parameters of the compensation circuit of the track, but also help to contain the phenomenon of magnetic polarization. Dell Vostro 1510 Dell Vostro 1710 Battery
2.1 Constant current limiting circuit
Circuit of Figure 3, A1 and A2 are two operational amplifiers, voltage reference Vref, VV and VI, the feedback voltage and input current signal. Its working principle is as follows: If the load current is not Viref value reached operational amplifier A1 in the regulation of the state, the A2 output is high, cut the reverse diode D, this time the error amplifier output is controlled from the highway A1 in the process of continuous adaptation. If VV> VVref, the output of the amplifier with low error VVref VV ", the amplifier output high error. The return flow is equal to the yield Viref output voltage is equal to the duration and OP VVref two play together. If the current rate of return higher than the Viref value is the output voltage is below reviews VVref necessarily high output A1, while the A2 state regulation. A2 A1 priority because of the high proportion reaches the end of the race.
