Advance Mini UPS

Mobile phone and small electronic gadget are powered from AC mains using an AC adaptor. In the event of mains failure, a low-capacity UPS will do the job satisfactorily. Here we design a simple, efficient, economical and easy-to-construct UPS for mobile phone or telephone set. The circuit advance mini ups can also be used for high power by changing a transformer with a high current rating so this circuit can be use power backup for laptop also.

Block Diagram of Advance Mini UPS

The block diagram of the circuit advance mini UPS wit charger unit is shown in figure 1. Normally, small power electronic gadgets utilize current less than 500mA to enable the circuit and to charge the battery. It consists of power supply for electronic gadget, charger unit, switching unit, SC sensor etc. The output power 5watts is delivered by the circuit advance mini UPS which is sufficient for most small powered gadget.block diagram of advance mini ups

Circuit Description of Advance Mini UPS

The circuit diagram of advance mini UPS is shown in figure 2. IC1 is a opto-coupler IC and consist a LED and a phototransistor which is used here as AC sensor. When AC mains is available internal LED of IC1 glow which activate internal phototransistor. As a result the output of IC1 becomes high which is connected to the input of gate N1 of IC2 as well as a 12V SMF battery. When output of IC1 is high, the output of gate N1 of pin 3 also goes high and relay RL1 energizes via relay driver transistor T3.

When relay RL1 energizes it conduct mains AC supply to the primary of the transformer X1 and also available at output of UPS. Transformer X1 stepped down the input AC mains voltage to 9V-0-9V which is further rectified by using diode D2 through D5. The availability of secondary voltage is indicated by glowing LED1 which is connected to secondary coil of transformer X1 through resistor R3. The battery is charged through charger circuit provided charger switch SW2 is ‘on’ (closed). The power supply to IC3 through relay contact RL1 (d) is disconnected. As a result, the transformer works as a charger transformer and the battery starts charging through current-limiting resistor R6 and R7.

circuit diagram of advance mini ups

When switch SW1 is in on position and AC mains supply fails which de-energizes the relay RL1 instantly and as a result the circuit use in inverter mode.

The inverter circuit is wired around IC3 in an astable multivibrator mode operating at a frequency of 50 Hz. The output from pin 10 and pin 11 of IC3 directly drive the MOSFET transistor T1 and T2. These two MOSFETs (T1 and T2) is configured in push-pull mode. Capacitor C1 is used to filter DC signal if any available at the output of inverter circuit.

At the time when the battery voltage become less then 10V the output of gate N2 at pin 4 goes high which further fired the SCR1 through resistor R17. As a result the supply voltage is pulled down to ground via RL1 (d), diode D8, resistor R12, and SCR1 which disable the oscillator due to the absence of power supply of IC3. Glowing LED5 indicate the battery is out of use i.e. cut-off condition. When the battery voltage is less then 13.5V or more than 10V it put output of gate N2 at pin 4 become low and as a result SCR1 does not fire. Glowing LED4 indicate that the battery is ready for use.

PCB Design: The actual-size, single-side PCB layout for the circuit of advance mini UPS is shown in Fig. 3 and its components layout in Fig. 4.

Fsolder side pcb design of advance mini ups

Figure 3: Actual Size Solder Side PCB Design  for Advance Mini UPS

component side pcb design of advance mini ups.png

Figure 4: Component Side PCB Design for Advance Mini UPS

The proposed front-panel layout for the advance mini UPS, including LEDs arrangement, is shown in Fig. 5.

proposed front panel layout including leds arrangement for the ups for advance mini ups



Resistor (all ¼-watt, ± 5% Carbon)

R1, R2, R12, R13 = 100 Ω, 1 WATT

R3 = 2.2 KΩ

R4 = 100 KΩ

R5 = 5 KΩ

R6, R7 = 10Ω, 10 WATT

R8 = 10 KΩ

R9, R10, R11, R17, R18 = 1 KΩ

R14 = 560 KΩ

R15, R16 = 100 Ω

C1 = 100nF/ 600V (Polyester Capacitor)

C2 = 100nF/250V (Polyester Capacitor)

C3, C4 = 1 µF/40V (electrolytic capacitor)

C5 = 1000 µF/40V (electrolytic capacitor)

C6 = 22 µF/40V (electrolytic capacitor)

C7 = 10 µF/40V (electrolytic capacitor)

C8 = 8.2nF (ceramic disc)


IC1 = PC817 (opto-coupler)

IC2 = CD4011B (Quadruple 2-input NAND gate)

IC3 = CD4047 (mono/astable multivibrator)

SCR1 = BT169

T1, T2 = IRFZ44N (N-channel MOSFET)

T3 = BD139 (NPN transistor)

D1 – D8 = 1N4007 (rectifier diode)

ZD1 = 10V (zener diode)

ZD2 = 13.5V (zener diode)

ZD3 = 5.6V (zener diode)

LED1, LED4 = Green LED

LED2, LED3, LED5 = Red LED

X1 = 230V AC primary to 9V-0-9V, 2A secondary transformer

RL1 = 9V, 150Ω 4C/O relay

SW1, SW2 = SPST switch

B1 = 12V, 7Ah SMS battery



  • partha sarathi banerjee

    sir, i need the pcb design of 800 va ups which can give 1 hour current backup for a desktop computer. please help me by providing it.