Check the voltage on Pin 4 (DTC). If it is shorted directly to ground, the dead-time is zero. This causes cross-conduction shoot-through currents. Unstable Output Frequency: Inspect the capacitor on Pin 5 ( CTcap C sub cap T ) and the resistor on Pin 6 ( RTcap R sub cap T
Both buck and boost topologies. Battery Chargers: Such as 36V Li-ion chargers.
Using a circuit simulator, such as SPICE, we can simulate the TL494 circuit diagram and observe the output voltage, current, and switching waveform. tl494 circuit diagram
). The frequency of this oscillator determines the switching rate of the power stages.
Advantages:
Common output for error amps, used for loop compensation. DTC (Pin 4): Dead-Time Control; controls minimum off-time. CT (Pin 5): Oscillator Capacitor connection. RT (Pin 6): Oscillator Resistor connection. GND (Pin 7): Ground. C1 (Pin 8): Collector of Output Transistor 1. E1 (Pin 9): Emitter of Output Transistor 1. E2 (Pin 10): Emitter of Output Transistor 2. C2 (Pin 11): Collector of Output Transistor 2. VCC (Pin 12): Supply Voltage.
Offers a user-adjustable dead-time minimum. This prevents simultaneous conduction in push-pull configurations, protecting external switching transistors from cross-conduction ("shoot-through"). Check the voltage on Pin 4 (DTC)
The "Feedback" or "Compensation" pin (Pin 3) is the output of these amplifiers. On the circuit diagram, this is the crucial junction where the voltage control and current control signals merge. It serves as the control voltage input for the PWM comparator. A higher voltage at Pin 3 results in a shorter duty cycle, effectively turning off the output transistors sooner to correct the output.
To prevent heavy inrush current during startup, an external capacitor can be wired between Pin 14 ( VREFcap V sub cap R cap E cap F end-sub Unstable Output Frequency: Inspect the capacitor on Pin
Conversely, a Boost converter steps up a lower DC voltage to a higher one. This topology is essential when the required output voltage is higher than the input, such as in battery-powered devices.