Switching DC regulated power supply
This circuit uses TWH8778 electronic switch integrated circuit to realize the function of DC regulated power supply.
1. Circuit working principle
The circuit diagram of the switching DC regulated power supply is shown in Figure 45.
When the switch S is closed, the 220V AC voltage is rectified by VD1~VD4, filtered by capacitor C1, and output in two ways. One way is added to pin 1 of the IC integrated circuit, and the other way is added to the emitter terminal of the triode VT through the resistors R1 and R3, so that the triode VT is in a saturated conduction state. At this time, the voltage of the collector (above 1.6V) is output to pin 5 of the IC, which makes the internal electronic switch of the IC conduct, and the output voltage of pins 2 and 3 increases the current in the inductor to supply the load.
When the output voltage reaches 6V, the regulator tube VS breaks down, and the current on the resistor R3 increases, causing the voltage on R3 to increase. When the output voltage reaches 12V, the triode VT changes from a saturated state to an amplified state. When the output voltage exceeds 12V, the emitter junction voltage of the triode VT decreases, causing the output voltage of the collector to drop. When it drops to 1.6V (that is, the potential of pin 5 of the IC integrated circuit drops to 1.6V), the IC switch integrated circuit is disconnected. The current of the inductor L drops, and the output voltage also drops. When it drops to 12V, the collector potential of the triode VT rises above 1.6V, and the IC is turned on again, so that the output voltage is always stable at 12V.
2. Selection of components:
IC selects TWH8778 electronic switch integrated circuit; R1-R5 selects RTX—1/4W carbon film resistor; C1 selects aluminum electrolytic capacitor with a withstand voltage of 25V, and C2 and C4 select CD11—16V electrolytic capacitor , C4 selects CT1 type high frequency ceramic capacitor; VD1~VD5 selects IN4004 silicon type rectifier diode, VD6 selects IN4148 silicon type switching
diode ; VS selects IN4106 or 2CW60 silicon voltage regulator diode; RP can use WSW type organic solid trimming variable Resistor; other components can be marked on the reference diagram.
3. Production and debugging method
The structure of this circuit is simple, as long as it is welded according to the circuit diagram, the selected components are correct, and it can work normally without debugging. The output voltage of the regulated power supply is 12V and the current is 1A.
Adjustable DC regulated power supply
This circuit can realize an adjustable DC stabilized power supply through a simple circuit structure, and has a voltage indicator, and the output DC voltage range is 0 ~ 30V.
1. Circuit working principle
The circuit principle is shown in Figure 46.
This circuit adds 220V AC voltage to the primary side W1 through the transformer T, and obtains 35V and 6V AC voltages on the secondary side W2 and W3 respectively, and the secondary side W2 terminal is rectified by diode VD1-VD4 and filtered by capacitors C1 and C2 After input to the input end of the IC three-terminal integrated voltage regulator circuit, the DC voltage of 35V is output through the IC voltage regulator integrated circuit, resistor R1 and capacitor C4. The 6V AC voltage output by the W3 coil on the secondary side outputs a -1.25V negative voltage as an auxiliary power supply through the diode VD5, capacitor C3, resistor R2 and Zener diode VS. The rheostat RP is added to the control terminal of the IC integrated circuit. By adjusting the rheostat RP, the output terminal can output a DC power supply of 0~30V.
2. Selection of components:
IC uses LM317 three-terminal voltage regulator integrated circuit; R1 and R use 1/2W metal film resistors; C1 and C3 use aluminum electrolytic capacitors with withstand voltages of 50V and 10V respectively; C2 and C4 use CD11 —16V electrolytic capacitor; VD1~VD5 choose IN4007 silicon rectifier diode; VS choose IN4106 or 2CW60 silicon Zener diode; RP can use WSW type organic solid fine-tuning variable resistor; T choose 10W, the secondary side voltage is 35V and 6V Power transformer; other components can be marked on the reference diagram.
3. Production and debugging method
The structure of this circuit is simple, as long as it is welded according to the circuit diagram, the selected components are correct, and it can work normally without debugging.