The challenge is becoming bigger in an era of creating the Ultimate Customer Experience. Traditional Royer auto-self-excited transductors and push-pull circuit is likely to cause mutual constraints and unbalance among the performances because of its inherent defects. As a result, it’s difficult to ensure excellent performance in many aspects at the same time, as shown in Figure 1. Meanwhile, the Royer circuit only provides basic functions but protections under abnormal conditions. Once the circuit is abnormal, the power module may be damaged and even cause serious consequences.
Most fixed input voltage DC/DC converters don't have the function of continuous SCP, which is shortcoming of the Royer circuit. However, MORNSUN fixed input voltage R3 series achieve a breakthrough in SCP by changing the working mode of the push-pull circuit and greatly enlarge capacitive load at the same time, making SCP in harmony with large capacitive load.
Sometimes a large capacitor is necessary to be connected at the output end of the converter to reduce the ripple & noise, but the capacitive load capacity of fixed input voltage converters may not be enough for it. For example, for 1W converter with 5V input and 5V output, its max. capacitive load is about 220uF. Once the capacitive load exceeds the limits, it will cause start-up failure and even damage the converter.
Generally, in power supplies market, people are often be induced to focus on the efficiency at full load, but ignore the efficiency at light load & stand-by power consumption, from which the first is relatively easier.
In case of short circuit, a power supply can be damaged or even melted if it doesn’t have SCP. The R3 series are designed with unique SCP control technology and achieve a continuous SCP for all series offering 5/12/15/24VDC input voltage. It effectively avoids chain reactions of front end power source caused by short circuit of back end circuit and protect front end power source from failure and further prevent the system breakdown, thereby improves the system reliability.
Royer self-oscillation circuit has no soft start-up function and has a large transient input current at the moment of start-up, which may breakdown the internal switching components then cause short circuit or even a chain reaction till a complete failure of the system. Yet, the IC fixed input voltage R3 series adopt features built-in soft-start function, setting R3 series free from above problem by avoiding too much impulse current at start-up.
On the other hand, the soft start-up can reduce input energy because of no need for a large input current, lower power redundancy of front end power source and save the cost of overall system design. Fixed input voltage R3 series are suitable for energy constraint applications such as explosion-proof and multi-power modules used in parallel.
Generally speaking, power supply’s capacitive load, soft start-up and SCP are interrelated and restricted, improving any one of which will constrain the other two.
By virtue of innovative technology, fixed input voltage R3 series "decouple" above three performances to eliminate mutual restraint and get the three performances promoted simultaneously. Consequently, R3 series not only achieve a great improvement in SCP and start-up, but also greatly improve the capacitive load,ensuring a normal start-up in CC mode where large capacitive load exists. For example, a fixed input voltage DC/DC R3 series outputs 5VDC, and then its max. capacitive load rises from 220uF to 2400uF. Another example is as shown in Figure 2. B0505S-1WR3 is connected with an external 4000uF and the CC mode starts normally.
The R3 series reduce the power consumption of main switching devices and transformers at different loads by optimizing control technology, thereby increasing the efficiency at light load and decreasing the stand-by power consumption.
Efficiency at light load: fixed input voltage R3 series with 5VDC output not only provide an efficiency to over 82% at full load (100% load) but also over 75% at light load (10% load), which reduces temperature rise of the system at light load. By contrast, it is 20 percentage points higher than fixed input voltage R2 series that are known for high efficiency at light load (see Figure 3).
Stand-by power consumption: B0505S-1WR3’s stand-by power consumption is 25mW and no-load current is 5mA (see Figure 4). It is particularly suitable for energy-saving equipment that has a higher requirement for stand- by power consumption, e.g., portable equipment.
Fixed input voltage R3 series have built-in OTP. Once the temperature exceeds its rated value, the converter will automatically go into dormant state to avoid damage and can automatically recover when the temperature drops to the set value.
For the system, the output current of a power module has an "embarrassing" area between rated value and minimum point to hit the over-current protection. If the module keeps operating in the over-current condition for a long time, it can easily be damaged due to heat of over power, which can be avoided if the module has OTP.